JP2019097155A - Elastic wave device, radio-frequency front-end circuit, and communication device - Google Patents

Abstract

To provide an elastic wave device in which a fractional bandwidth can be widened and variations in frequency are unlikely to occur.SOLUTION: An elastic wave device 1 includes a piezoelectric layer 2, an IDT electrode 3 on the piezoelectric layer 2, and a dielectric film 8 covering the IDT electrode 3. The IDT electrode 3 includes a first electrode layer 4 and a second electrode layer 5 laminated on the first electrode layer 4. Each of wavelength normalized film thicknesses of the first electrode layer 4 and the second electrode layer 5 is equal to or greater than 1.25%, the wavelength normalized film thicknesses of the first and second electrode layers being normalized using a wavelength defined by the electrode finger pitch of the IDT electrode 3. The second electrode layer 5 has a density lower than that of the first electrode layer 4. The side 5a of the second electrode layer 5 is inclined with respect to the thickness direction of the IDT electrode 3.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an elastic wave device, a high frequency front end circuit, and a communication device.

  Heretofore, elastic wave devices are widely used as filters for mobile phones. Patent Document 1 below discloses an example of an elastic wave device. In this elastic wave device, an IDT electrode made of a laminated metal film in which a plurality of metal layers are laminated is provided on a piezoelectric substrate. The side surface of the electrode finger of the IDT electrode extends in parallel with the thickness direction of the IDT electrode. The IDT electrode is covered by a dielectric layer provided on a piezoelectric substrate.

JP, 2012-175315, A

  In the elastic wave device described in Patent Document 1, since the IDT electrode is covered by the dielectric layer, the IDT electrode is not easily damaged. However, covering the IDT electrode with a dielectric layer has a problem that the specific band becomes narrow. Furthermore, depending on the configuration of the metal layer of the IDT electrode, the variation in frequency may be large.

  An object of the present invention is to provide an elastic wave device, a high frequency front end circuit, and a communication device which can widen a relative bandwidth and hardly cause variations in frequency.

  An elastic wave device according to the present invention comprises a piezoelectric layer, an IDT electrode provided on the piezoelectric layer, and a dielectric film covering at least a part of the IDT electrode, the IDT electrode being The first electrode layer having the first electrode layer and the second electrode layer laminated on the first electrode layer, the first electrode layer standardized by the wavelength defined by the electrode finger pitch of the IDT electrode And the second electrode layer has a density lower than that of the first electrode layer, and the second electrode layer has a density lower than that of the first electrode layer. The side surface of the second electrode layer is inclined with respect to the thickness direction of the IDT electrode.

  In a specific aspect of the elastic wave device according to the present invention, the side surface of the first electrode layer is inclined with respect to the thickness direction.

  In another particular aspect of the elastic wave device according to the present invention, the side surface of the first electrode layer extends parallel to the thickness direction. In this case, it is possible to widen the specific band in the wider range of the inclination angle of the side surface of the second electrode layer.

In still another particular aspect of the elastic wave device according to the present invention, the second electrode layer is an Al layer, and the Rayleigh wave is used as a main mode, and the resonant frequency of the Rayleigh wave is Fr and an unnecessary wave. When a resonant frequency of a certain SH wave is Fsh, an inclination angle of the first electrode layer and the second electrode layer with respect to the thickness direction is θ, and a wavelength normalized film thickness of the second electrode layer is T _Al In addition, combinations of the resonance frequency Fr, the resonance frequency Fsh, the inclination angle θ, and the wavelength normalized film thickness T _Al are combinations shown in Table 1 below.

In still another specific aspect of the elastic wave device according to the present invention, the first electrode layer is a Pt layer, the second electrode layer is an Al layer, and Rayleigh wave is used as a main mode. An inclination angle θ of the first electrode layer and the second electrode layer with respect to the thickness direction, a wavelength normalized film thickness of the first electrode layer T _PT , and a wavelength normalized of the second electrode layer the film thickness is taken as T _Al, the inclination angle theta, the wavelength standardized thickness T _Pt, and a combination of wavelength normalized thickness T _Al is a combination shown in Table 2 below. In this case, the relative bandwidth can be more reliably broadened.

In another specific aspect of the elastic wave device according to the present invention, the first electrode layer is a Pt layer, the second electrode layer is a Cu layer, and Rayleigh wave is used as a main mode. The inclination angle of the first electrode layer and the second electrode layer with respect to the thickness direction is θ, the wavelength normalized film thickness of the first electrode layer is T _PT , and the wavelength normalized film of the second electrode layer the thickness is taken as T _Cu, the inclination angle theta, the wavelength standardized thickness T _PT, and the combination of the wavelength normalized thickness T _Cu is a combination shown in Table 3 below. In this case, the relative bandwidth can be more reliably broadened.

In still another specific aspect of the elastic wave device according to the present invention, the first electrode layer is a Mo layer, the second electrode layer is an Al layer, and Rayleigh waves are used as a main mode. When an inclination angle of the first electrode layer and the second electrode layer with respect to the thickness direction is θ, and a wavelength normalized film thickness of the second electrode layer is T _Al , θ ≦ 2.2 × T _Al +12.1. In this case, the relative bandwidth can be more reliably broadened.

In still another specific aspect of the elastic wave device according to the present invention, the wavelength normalized film thickness T _Al of the second electrode layer is 2% or more. In this case, the relative bandwidth can be further surely increased.

  The high frequency front end circuit of the present invention comprises an elastic wave device configured according to the present invention and a power amplifier.

  The communication device of the present invention comprises a high frequency front end circuit configured according to the present invention and an RF signal processing circuit.

  According to the present invention, it is possible to provide an elastic wave device, a high frequency front end circuit, and a communication device which can widen the relative bandwidth and hardly cause variations in frequency.

It is a front sectional view of an elastic wave device concerning a 1st embodiment of the present invention. It is an enlarged front sectional view showing the electrode finger vicinity of an IDT electrode in a 1st embodiment of the present invention. It is a figure which shows the relationship of inclination-angle (theta) and (DELTA) f ratio in the 1st Embodiment of this invention, a 1st comparative example, and a 2nd comparative example. It is front sectional drawing which shows the electrode finger vicinity of the IDT electrode in a 3rd comparative example. It is a figure which shows the relationship of inclination-angle (theta) and (DELTA) f ratio in the 1st Embodiment of this invention, a 1st comparative example, and a 3rd comparative example. It is a figure which shows the relationship between inclination-angle (theta) of the side of the 1st electrode layer of an IDT electrode in the 4th comparative example, and a 2nd electrode layer, and specific zone deltaf. It is a figure which shows the relationship between inclination-angle (theta) of the side of the 1st electrode layer of an IDT electrode, and a 2nd electrode layer in 1st Embodiment and 4th Comparative example of this invention, and fr ratio. The second electrode layer in which the side surface is inclined with respect to the thickness direction of the IDT electrode in the case where the IDT electrode has a first electrode layer (Pt layer) having a wavelength normalized film thickness of 1.25% or more It is a figure which shows the relationship of the wavelength normalization film thickness of (Al layer), and (DELTA) f ratio. In the first embodiment of the present invention, the Δf ratio is 1 for the wavelength normalized film thickness of the first electrode layer and the second electrode layer, and the side surface of the first electrode layer and the second electrode layer. It is a figure which shows a relationship with inclination-angle (theta) 1. FIG. FIG. 7 is a diagram showing impedance frequency characteristics when the wavelength normalized film thickness of the first electrode layer is 3% in the first embodiment of the present invention. FIG. 7 is a diagram showing impedance frequency characteristics when the wavelength normalized film thickness of the first electrode layer is 7% in the first embodiment of the present invention. It is an enlarged front sectional view showing electrode finger vicinity of an IDT electrode in the 1st modification of a 1st embodiment of the present invention. It is front sectional drawing of the elastic wave apparatus which concerns on the 2nd modification of the 1st Embodiment of this invention. The figure which shows the relationship between the wavelength-normalized film thickness of the 1st electrode layer and the 2nd electrode layer in 3rd modification of a 1st embodiment of the present invention, and inclination angle theta 1 in which deltaf ratio becomes 1. It is. The figure which shows the relationship between the wavelength-normalized film thickness of the 1st electrode layer and the 2nd electrode layer in the 4th modification of the 1st embodiment of the present invention, and inclination angle theta 1 in which deltaf ratio becomes 1. It is. It is an enlarged front sectional view showing electrode finger vicinity of an IDT electrode in a 2nd embodiment of the present invention. It is a figure which shows the relationship between inclination-angle (theta) in 1st Embodiment and 2nd Embodiment of this invention, and ratio zone (DELTA) f ratio. FIG. 2 is a block diagram of a communication device having a high frequency front end circuit.

  Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

  It is to be noted that each embodiment described in the present specification is illustrative, and that partial replacement or combination of configurations is possible between different embodiments.

  FIG. 1 is a front cross-sectional view of an elastic wave device according to a first embodiment of the present invention.

  The elastic wave device 1 has a piezoelectric layer 2. The piezoelectric layer 2 is a lithium niobate layer, and the cut angle is 126 °. The material and the cut angle of the piezoelectric layer 2 are not limited to the above. The piezoelectric layer 2 may be a lithium tantalate layer. The piezoelectric layer 2 may be a lithium tantalate layer or a piezoelectric single crystal layer other than a lithium niobate layer.

  An IDT electrode 3 is provided on the piezoelectric layer 2. The IDT electrode 3 has a plurality of electrode fingers 3a. By applying an alternating voltage to the IDT electrode 3, an elastic wave is excited. In the present embodiment, Rayleigh waves are used as the main mode. When Rayleigh waves are used as the main mode, SH waves appear as ripples of unwanted waves. The reflector 6 and the reflector 7 are disposed on both sides of the IDT electrode 3 in the elastic wave propagation direction. Thus, the elastic wave device 1 of the present embodiment is an elastic wave resonator.

  FIG. 2 is an enlarged front cross-sectional view showing the vicinity of the electrode finger of the IDT electrode in the first embodiment.

  The IDT electrode 3 is a laminated metal layer in which a plurality of metal layers are laminated. Here, the film thickness of the plurality of metal layers standardized by the wavelength defined by the electrode finger pitch of the IDT electrode 3 is taken as the wavelength normalized film thickness (%). The plurality of metal layers of the IDT electrode 3 include a plurality of electrode layers which are metal layers having a wavelength normalized film thickness of 1.25% or more.

  More specifically, the IDT electrode 3 has a first electrode layer 4 located closest to the piezoelectric layer 2 and a second electrode layer 5 stacked on the first electrode layer 4. The wavelength normalized film thickness of the first electrode layer 4 is 2%, and the wavelength normalized film thickness of the second electrode layer 5 is 5%. The wavelength normalized film thickness of the first electrode layer 4 and the second electrode layer 5 is not limited to the above. The wavelength defined by the electrode finger pitch of the IDT electrode 3 is not particularly limited, but is 4 μm in the present embodiment.

  The first electrode layer 4 is the electrode layer having the highest density among the electrode layers having a wavelength normalized film thickness of 1.25% or more. The second electrode layer 5 is an electrode layer having a density lower than that of the first electrode layer 4. The IDT electrode 3 may include an electrode layer having a density higher than that of the first electrode layer 4 as long as the density of the first electrode layer 4 is higher than that of the second electrode layer 5.

  The material of the first electrode layer 4 is not particularly limited, but is Pt in this embodiment. The material of the second electrode layer 5 is not particularly limited, but is Al in the present embodiment. For example, the combination of materials of the first electrode layer 4 and the second electrode layer 5 may be Pt and Ti, Pt and Cu, Pt and Mo, Mo and Al, or Cu and Al, and the like.

  The configuration of the IDT electrode 3 is not limited to the above. The IDT electrode 3 only needs to have a plurality of electrode layers having a wavelength-normalized film thickness of 1.25% or more, and the first electrode layer 4 is positioned closer to the piezoelectric layer 2 than the second electrode layer 5 It should be done. The IDT electrode 3 may have a metal layer whose wavelength normalized film thickness is less than 1.25%. In the elastic wave device 1, the second electrode layer 5 is stacked directly on the first electrode layer 4, but indirectly on the first electrode layer 4 via another metal layer. The second electrode layer 5 may be stacked.

  As shown in FIG. 2, the first electrode layer 4 has a side surface 4 a. The second electrode layer 5 also has a side surface 5a. The side surface 4 a of the first electrode layer 4 and the side surface 5 a of the second electrode layer 5 are inclined with respect to the thickness direction of the IDT electrode 3. Here, the inclination angle with respect to the thickness direction of the IDT electrode 3 is assumed to be θ. The inclination angle θ has a positive inclination direction inward of the electrode finger 3a. The inclination angle θ of the side surface 4 a of the first electrode layer 4 and the inclination angle θ of the side surface 5 a of the second electrode layer 5 are the same in the present embodiment. The inclination angles θ of the side surfaces of the metal layers of the IDT electrode 3 may be different. In the IDT electrode 3, at least the side surface 5a of the second electrode layer 5 may be inclined with respect to the thickness direction.

A dielectric film 8 is provided on the piezoelectric layer 2 so as to cover the IDT electrode 3. The dielectric film 8 is made of silicon oxide represented by SiO _x . In the present embodiment, the dielectric film 8 is made of SiO ₂ . The dielectric film 8 may be made of silicon oxide in which x is a positive number, or may be made of a dielectric other than silicon oxide. The wavelength-normalized film thickness of the dielectric film 8 is not particularly limited, but is 30% in the present embodiment. In the present specification, the film thickness of the dielectric film 8 refers to the film thickness from the main surface of the piezoelectric layer 2 on which the dielectric film 8 is provided.

  The elastic wave device 1 of the present embodiment includes a piezoelectric layer 2, an IDT electrode 3 provided on the piezoelectric layer 2, and a dielectric film 8 covering the IDT electrode 3. Of the first electrode layer 4 and the second electrode layer 5 stacked on the first electrode layer 4, and the wavelength normalized film thickness of the first electrode layer 4 and the wavelength of the second electrode layer 5 The normalized film thickness is 1.25% or more, and the second electrode layer 5 has a density lower than that of the first electrode layer 4, and the side surface 5 a of the second electrode layer 5 is the IDT electrode 3. It has the composition of being inclined to the thickness direction. As a result, the relative bandwidth can be broadened, and frequency variations hardly occur. This will be described below by comparing the first embodiment with the first to fourth comparative examples.

  A plurality of elastic wave devices having the configuration of the first embodiment were manufactured by changing the inclination angles θ of the side surface 4 a of the first electrode layer 4 and the side surface 5 a of the second electrode layer 5. Furthermore, elastic wave devices of the first comparative example and the second comparative example were manufactured. The first comparative example is different from the first embodiment in that the inclination angle θ of the side surfaces of the first electrode layer and the second electrode layer is 0 °. The second comparative example is different from the first embodiment in that the IDT electrode includes only the first electrode layer. A plurality of elastic wave devices of the second comparative example were manufactured by changing the inclination angle θ of the side surface of the metal layer. The ratio bands Δf of the plurality of elastic wave devices were measured.

Here, the relative bandwidth of the elastic wave device in which the inclination angle θ of the side surface of all the metal layers of the IDT electrode is 0 ° is Δf ₀ . The value obtained by dividing the ratio band Δf of the elastic wave device in which the inclination angle θ of the side surface of at least one metal layer of the IDT electrode is larger than 0 ° by the ratio band Δf ₀ is the Δf ratio. At this time, the Δf ratio can be expressed as Δf / Δf ₀ . The elastic wave device that has measured the relative band Δf ₀ has the same conditions as the elastic wave device that has measured the relative band Δf except for the inclination angle θ. As in the first comparative example, the Δf ratio of the elastic wave device in which the inclination angle θ of the side surfaces of all the metal layers of the IDT electrode is 0 ° is 1. The Δf ratio of each elastic wave device having the configuration of the first embodiment by dividing the ratio band Δf of each elastic wave device having the configuration of the first embodiment by the ratio band Δf of the first comparative example Was calculated. Similarly, the ratio Δf of each elastic wave device of the second comparative example was calculated by dividing the ratio band Δf of each elastic wave device of the second comparative example by the ratio band Δf of the first comparative example. .

  FIG. 3 is a view showing the relationship between the inclination angle θ and the Δf ratio in the first embodiment, the first comparative example, and the second comparative example. When the relationship shown in FIG. 3 is determined, the first electrode layer is a Pt layer having a wavelength normalized film thickness of 2%, and the second electrode layer is an Al layer having a wavelength normalized film thickness of 5%. In FIG. 3, the white circular plot shows the results of the first embodiment. The black circular plot shows the results of the first comparative example. The square plots show the results of the second comparative example.

  As shown in FIG. 3, in the first embodiment in which the side surface of the second electrode layer is inclined with respect to the thickness direction of the IDT electrode, the Δf ratio is larger than 1 and the first electrode The specific band Δf can be wider than in the first comparative example in which the inclination angle θ of the side surface of the layer and the second electrode layer is 0 °. More specifically, when the inclination angle θ is 0 ° <θ <32 °, the relative bandwidth Δf can be made wider than in the first comparative example.

  On the other hand, in the second comparative example, the Δf ratio is smaller than 1 and the relative bandwidth Δf is narrower than in the first comparative example. Thus, when the IDT electrode is formed of a single layer, when the side surface of the electrode layer is inclined with respect to the thickness direction of the IDT electrode, the relative bandwidth Δf becomes narrower than when the inclination angle θ is 0 °. In the elastic wave device 1 according to the first embodiment, the plurality of side surfaces 5a of the second electrode layer 5 are not only inclined with respect to the thickness direction, but a plurality of wavelength normalized film thicknesses are 1.25% or more. The first electrode layer 4 and the second electrode layer 5 as an electrode layer of Thereby, the ratio band Δf can be effectively widened.

  As described above, when the wavelength-normalized film thickness of the second electrode layer is 5%, the inclination angle θ is preferably 0 ° <θ <32 °. Details of preferable ranges of the wavelength normalized film thickness of the first electrode layer and the second electrode layer and the inclination angle will be described later.

  The elastic wave device 1 of the first embodiment can widen the relative band by the side surface 5 a of the second electrode layer 5 being inclined with respect to the thickness direction of the IDT electrode 3. This will be shown below by comparing the first embodiment with the third comparative example.

  FIG. 4 is a front sectional view showing the vicinity of the electrode finger of the IDT electrode in the third comparative example.

  In the elastic wave device of the third comparative example, the side surface 104a of the first electrode layer 104 is inclined with respect to the thickness direction of the IDT electrode 103, and the side surface 105a of the second electrode layer 105 is in the thickness direction. It extends in parallel. A plurality of elastic wave devices of the third comparative example was manufactured by changing the inclination angle θ of the side surface 105 a of the second electrode layer 105.

  FIG. 5 is a view showing the relationship between the inclination angle θ and the Δf ratio in the first embodiment, the first comparative example, and the third comparative example. When the relationship shown in FIG. 5 is determined, the first electrode layer is a Pt layer having a wavelength normalized film thickness of 2%, and the second electrode layer is an Al layer having a wavelength normalized film thickness of 5%. In FIG. 5, a white circle plot shows the result of the first embodiment, and a black square plot shows the result of the third comparative example. The black circular plot shows the results of the first comparative example.

  As shown in FIG. 5, in the third comparative example, the Δf ratio is smaller than 1 and the relative bandwidth Δf is narrower than in the first comparative example. As described above, when the side surface 105 a of the second electrode layer 105 is not inclined with respect to the thickness direction of the IDT electrode 103, the side surface 104 a of the first electrode layer 104 may be inclined with respect to the thickness direction. The relative bandwidth Δf is narrower than when the inclination angle θ is 0 °. In the elastic wave device 1 of the first embodiment, since the side surface 5a of the second electrode layer 5 is inclined with respect to the thickness direction, the relative band Δf can be effectively widened.

  In the elastic wave device 1 according to the first embodiment, the first electrode layer having a density higher than that of the second electrode layer is located closer to the piezoelectric layer 2 than the second electrode layer. The bandwidth can be broadened. This will be shown below by comparing the first embodiment with the fourth comparative example.

  The fourth comparative example is different from the first embodiment in that the second electrode layer is located closer to the piezoelectric layer than the first electrode layer. A plurality of elastic wave devices of the fourth comparative example were manufactured by changing the inclination angle θ of the side surface of the first electrode layer and the second electrode layer (θ includes 0 °). The ratio bands Δf of the plurality of elastic wave devices of the fourth comparative example were measured.

  FIG. 6 is a view showing the relationship between the inclination angle θ of the side surface of the first electrode layer and the second electrode layer of the IDT electrode and the relative band Δf in the fourth comparative example. When the relationship shown in FIG. 6 is determined, the first electrode layer is a Pt layer having a wavelength normalized film thickness of 2%, and the second electrode layer is an Al layer having a wavelength normalized film thickness of 5%.

  As shown in FIG. 6, in the fourth comparative example, the inclination angle θ is larger than 0 ° than in the case where the inclination angle θ of the side surfaces of the first electrode layer and the second electrode layer is 0 °. It can be seen that the relative bandwidth Δf is narrower. As described above, when the second electrode layer having a lower density is positioned closer to the piezoelectric layer than the first electrode layer having a higher density, the specific band Δf becomes narrower as the inclination angle θ becomes larger. On the other hand, in the first embodiment, the first electrode layer 4 is located closer to the piezoelectric layer 2 than the second electrode layer 5, as shown in FIG. 3 and FIG. 5. In addition, the relative bandwidth can be broadened.

In the first embodiment, it will be shown below that frequency variations hardly occur. Here, a value obtained by dividing the resonance frequency of the elastic wave device having an inclination angle θ of the side surface of at least one metal layer of the IDT electrode larger than 0 ° by the resonance frequency of the elastic wave device having an inclination angle θ of 0 ° It is assumed to be the fr ratio. In addition, the said elastic wave apparatus whose inclination angle (theta) is larger than 0 degree is the conditions same as the said elastic wave apparatus whose inclination angle (theta) is 0 degree regarding points other than inclination angle (theta). Assuming that the resonance frequency of the elastic wave device in which the inclination angle θ of the side surface of all the metal layers of the IDT electrode is 0 ° is fr ₀ , the fr ratio can be expressed as fr / fr ₀ . The fr ratio of the elastic wave device in which the inclination angle θ of the side surface of all the metal layers of the IDT electrode is 0 ° is 1. The fr ratio of the first embodiment was determined by dividing the resonance frequency of each elastic wave device having the configuration of the first embodiment by the resonance frequency of the elastic wave device of the first comparative example. Similarly, the fr ratios of the respective elastic wave devices of the fourth comparative example were determined. By the way, the resonant frequency used in the calculation of the fr ratio is the resonant frequency of the main mode.

  FIG. 7 is a view showing the relationship between the inclination angle θ of the side surface of the first electrode layer and the second electrode layer of the IDT electrode and the fr ratio in the first embodiment and the fourth comparative example. In FIG. 7, a white circle plot shows the result of the first embodiment, and a black circle plot shows the result of the fourth comparative example.

  As shown in FIG. 7, in the fourth comparative example, the change of the fr ratio with respect to the change of the inclination angle θ is large. Therefore, when the inclination angle θ varies in the manufacturing process, the variation in frequency becomes large. On the other hand, in the first embodiment, it can be seen that the change in the fr ratio is small even if the inclination angle θ changes. Therefore, in the first embodiment, even if the inclination angle θ varies in the manufacturing process, the frequency variation hardly occurs. As described above, in the first embodiment, the relative bandwidth Δf can be broadened, and variations in frequency are less likely to occur.

  In the following, it is shown that the specific band can be broadened by the wavelength normalized film thickness of the first electrode layer 4 and the second electrode layer 5 being 1.25% or more.

  An elastic wave device having the same configuration as that of the first embodiment except that the inclination angle θ of the side surface of the first electrode layer is 0 ° and the inclination angle θ of the side surface of the second electrode layer is 5 °. A plurality of samples were manufactured by changing the wavelength normalized film thickness of the second electrode layer. Furthermore, in the elastic wave device of the first comparative example, in which the inclination angle θ of the side surface of the first electrode layer and the second electrode layer is 0 °, the wavelength-normalized film thickness of the second electrode layer is changed It was made to make two or more. Next, the Δf ratio of each elastic wave device was calculated.

  FIG. 8 shows that the side surface is inclined with respect to the thickness direction of the IDT electrode in the case where the IDT electrode includes the first electrode layer (Pt layer) having a wavelength-normalized film thickness of 1.25% or more. It is a figure which shows the relationship of the wavelength normalization film thickness of 2 electrode layers (Al layer), and (DELTA) f ratio. When the relationship in FIG. 8 is determined, the first electrode layer is a Pt layer having a wavelength normalized film thickness of 2%, and the second electrode layer is an Al layer.

  As shown in FIG. 8, the Δf ratio is smaller than 1 when the wavelength-normalized film thickness of the metal layer whose side surface is inclined with respect to the thickness direction of the IDT electrode is thinner than 1.25%. On the other hand, when the wavelength-normalized film thickness of the second electrode layer is 1.25% or more, it is understood that the Δf ratio is 1 or more. Therefore, when the wavelength-normalized film thickness of the electrode layer is 1.25% or more, the relative band can be effectively widened.

  Here, as shown in FIG. 3, when the wavelength-normalized film thickness of the second electrode layer is 5%, the inclination angle θ is preferably 0 ° <θ <32 °. In the following, preferable ranges of the wavelength normalized film thickness of the first electrode layer and the second electrode layer and the tilt angle will be described in more detail.

  A plurality of elastic wave devices having the configuration of the first embodiment were manufactured by changing the wavelength normalized film thickness of the first electrode layer 4 and the second electrode layer 5 and the inclination angle θ of the side surface. A plurality of elastic wave devices of the first comparative example having an inclination angle θ of 0 ° were manufactured by changing the wavelength-normalized film thickness of the first electrode layer and the second electrode layer. The ratio bands Δf of the plurality of elastic wave devices were measured. Furthermore, the Δf ratio of each elastic wave device having the configuration of the first embodiment was calculated. Here, the inclination angle θ at which the Δf ratio is 1 is taken as the inclination angle θ1. The inclination angle θ1 was obtained for each wavelength normalized film thickness of the first electrode layer 4 and the second electrode layer 5. The impedance frequency characteristics of the plurality of elastic wave devices were also measured.

  FIG. 9 shows the wavelength-normalized thicknesses of the first electrode layer and the second electrode layer, and the Δf ratio of 1 on the side surfaces of the first electrode layer and the second electrode layer in the first embodiment. It is a figure which shows the relationship with inclination angle (theta) 1 which becomes. When the relationship in FIG. 9 is determined, the first electrode layer is a Pt layer, and the second electrode layer is an Al layer. In FIG. 9, the white circular plot shows the result of the wavelength normalized film thickness of the Pt layer being 3%. The black circular plot shows the result that the wavelength-normalized film thickness of the Pt layer is 4%. The white square plot shows the result that the wavelength-normalized film thickness of the Pt layer is 6%. The black square plot shows the result that the wavelength-normalized film thickness of the Pt layer is 7%. The triangular plot shows the result of the wavelength normalized film thickness of the Pt layer being 8%.

  As shown in FIG. 9, as the wavelength-normalized film thickness of the second electrode layer 5 increases, the inclination angle θ1 at which the Δf ratio becomes 1 increases. As shown in FIG. 3, when the inclination angle θ is in the range of 0 ° <θ ≦ θ1, the Δf ratio is 1 or more, and the relative band Δf can be broadened.

  Here, in the cases where the wavelength-normalized film thickness of the Pt layer which is the first electrode layer 4 is 4% or less and 6% or more, the wavelength-normalized film thickness of the second electrode layer 5 The tendency of the change of the inclination angle θ at which Δf becomes 1 with respect to the change of is different. This is because the resonant frequency of the Rayleigh wave as the main mode and the resonant frequency of the SH wave in the cases where the wavelength-normalized film thickness of the first electrode layer 4 is 4% or less and 6% or more. It is thought that the relationship with is different. As an example of the basis which shows this, the example of the impedance characteristic in the case where the wavelength-normalized film thickness of the 1st electrode layer 4 is 4% or less and the case where it is 6% or more is shown in the following FIGS. Shown in.

  FIG. 10 is a diagram showing impedance frequency characteristics when the wavelength normalized film thickness of the first electrode layer is 3% in the first embodiment. FIG. 11 is a diagram showing impedance frequency characteristics when the wavelength normalized film thickness of the first electrode layer is 7% in the first embodiment.

  The resonance frequency of the Rayleigh wave is Fr, and the resonance frequency of the SH wave is Fsh. As shown in FIG. 10, when the wavelength-normalized film thickness of the first electrode layer 4 is 3%, it is understood that the relationship of Fsh> Fr is established. As shown in FIG. 11, when the wavelength-normalized film thickness of the first electrode layer 4 is 7%, it is understood that the relationship of Fsh <Fr is satisfied. Although not shown, it is known that when the wavelength-normalized film thickness of the first electrode layer 4 is around 5%, Fr and Fsh become substantially the same.

  Therefore, Fsh> Fr when the wavelength normalized film thickness of the first electrode layer 4 is 4% or less, and Fsh when the wavelength normalized film thickness of the first electrode layer 4 is 6% or more. It is considered to be <Fr.

Here, in the first embodiment, the wavelength normalized film thickness of the first electrode layer 4 as the Pt layer is T _PT, and the wavelength normalized film thickness of the second electrode layer 5 as the Al layer is T _Al. I assume. Returning to FIG. 9, the wavelength normalized film thickness T _PT of the first electrode layer 4 is 4% or less (Fsh> Fr), and the inclination angle θ ≦ 3.8 × T _Al +4.27. Sometimes, the Δf ratio can be more reliably made 1 or more, and the relative bandwidth Δf can be widened. On the other hand, the wavelength normalized thickness _{T PT} of the first electrode layer 4 is more than 6% (Fsh <Fr) in a case, the wavelength normalized thickness _{T Al} of the second electrode layer 5 is 4% or less In the case of the above, when the inclination angle θ ≦ 3.9 × T _Al −0.4, the Δf ratio can be more reliably made 1 or more. Wavelength standardized thickness _{T PT} of the first electrode layer 4 is at least 6% a (Fsh <Fr) case, when the wavelength normalized thickness _{T Al} of the second electrode layer is thicker than 4%, When the inclination angle θ ≦ 2.8 × T _Al +4, the Δf ratio can be more reliably made 1 or more. The conditions which can make (DELTA) f ratio more reliably 1 or more are put together in following Table 4 and Table 5, and are shown.

By combining the combination of the resonance frequency Fr, the resonance frequency Fsh, the inclination angle θ, and the wavelength normalized film thickness T _{Al with} the combination shown in Table 4, the Δf ratio can be more reliably set to 1 or more, and the ratio more reliably The band Δf can be broadened. Similarly, by setting the combination of the inclination angle θ, the wavelength normalized film thickness T _Pt and the wavelength normalized film thickness T _{Al to} the combination shown in Table 5, the Δf ratio can be more reliably made 1 or more. The relative band Δf can be surely widened.

  In the present embodiment, the IDT electrode 3 includes two electrode layers having a wavelength normalized film thickness of 1.25% or more, but three or more electrode layers having a wavelength normalized film thickness of 1.25% or more. You may have.

  Hereinafter, first and second modifications of the first embodiment will be described. Also in the first modification and the second modification, as in the first embodiment, the relative bandwidth Δf can be broadened, and variations in frequency are less likely to occur.

  FIG. 12 is an enlarged front cross-sectional view showing the vicinity of the electrode finger of the IDT electrode in the first modified example of the first embodiment.

  The present modification differs from the first embodiment in that the IDT electrode 13 includes a metal layer having a wavelength-normalized film thickness of less than 1.25%. Except for the above point, this modification has the same configuration as that of the first embodiment.

  More specifically, an adhesion layer 14 having a wavelength-normalized film thickness of less than 1.25% is provided between the piezoelectric layer 2 and the first electrode layer 4. Between the first electrode layer 4 and the second electrode layer 5, a diffusion preventing layer 15 having a wavelength-normalized film thickness of less than 1.25% is provided. Thereby, the adhesion between the IDT electrode 13 and the piezoelectric layer 2 can be enhanced, and the mutual diffusion between the first electrode layer 4 and the second electrode layer 5 can be suppressed. The adhesion layer 14 is not particularly limited, and is, for example, a Ti layer or a NiCr layer. Although the diffusion preventing layer 15 is not particularly limited, it is, for example, a Ti layer or the like. Thus, it may have a metal layer whose wavelength-normalized film thickness is less than 1.25%. The side surface of the metal layer having a wavelength-normalized film thickness of less than 1.25% may also be inclined with respect to the thickness direction of the IDT electrode 13.

  FIG. 13 is a front cross-sectional view of an elastic wave device according to a second modification of the first embodiment.

  The elastic wave device of this modification includes a support substrate 24, a high sound velocity film 25 provided on the support substrate 24, and a low sound velocity film 26 provided on the high sound velocity film 25. The piezoelectric layer 22 is provided on the low sound velocity film 26.

  The high sound velocity film 25 is a film in which the sound velocity of the bulk wave propagating is higher than the sound velocity of the elastic wave propagating in the piezoelectric layer 22. The material of the high sound velocity film 25 is, for example, a piezoelectric material such as aluminum nitride, aluminum oxide, silicon carbide, silicon nitride, silicon oxynitride, silicon, DLC film, silicon, sapphire, lithium tantalate, lithium niobate, quartz crystal, Examples include various ceramics such as alumina, zirconia, cordierite, mullite, steatite, forsterite, diamond, magnesia, materials containing the above materials as main components, and materials containing the mixture of the above materials as main components it can. The material of the high sound velocity film 25 may be a material having a relatively high sound velocity.

  The low sound velocity film 26 is a film in which the sound velocity of the bulk wave propagating is lower than the sound velocity of the elastic wave propagating in the piezoelectric layer 22. Examples of the material of the low sound velocity film 26 include a material containing silicon oxide, glass, silicon oxynitride, tantalum oxide, or a compound obtained by adding fluorine, carbon, or boron to silicon oxide as a main component. The material of the low sound velocity film 26 may be a material having a relatively low sound velocity.

  With the laminated body including the high sound velocity film 25, the low sound velocity film 26, and the piezoelectric layer 22, the energy of the elastic wave can be effectively confined to the piezoelectric layer 22 side.

  The high sound velocity film 25 may not be provided. In this case, the support substrate 24 is preferably a high sound velocity substrate made of a material having a relatively high sound velocity as described above. More specifically, as the material of the high sound velocity substrate, for example, aluminum nitride, aluminum oxide, silicon carbide, silicon nitride, silicon oxynitride, silicon, DLC film, silicon, sapphire, lithium tantalate, lithium niobate, quartz crystal Etc., various ceramics such as alumina, zirconia, cordierite, mullite, steatite, forsterite, etc., diamond, magnesia, or materials containing the above materials as main components, or mixtures of the above materials as main components Materials can be mentioned. As a result, the energy of the elastic wave can be effectively confined to the piezoelectric layer 22 side by forming a laminate composed of the support substrate 24 as the high sound velocity substrate, the low sound velocity film 26 and the piezoelectric layer 22. it can.

  As described above, the combination of materials of the first electrode layer and the second electrode layer is not limited to Pt and Al. In the following, the range of the tilt angle θ in which the specific band can be broadened is shown when the combination of materials of the first electrode layer and the second electrode layer is other than Pt and Al.

  Here, an elastic wave device according to a third modified example of the first embodiment shown below is the same as the elastic wave device of the first embodiment except that the second electrode layer is a Cu layer. The structure of An elastic wave device according to a fourth modified example of the first embodiment described below has the same configuration as the elastic wave device of the first embodiment except that the first electrode layer is a Mo layer. Have. The combination of materials of the first electrode layer and the second electrode layer is Pt and Cu in the third modification, and Mo and Al in the fourth modification.

  FIG. 14 shows the relationship between the wavelength-normalized film thickness of the first electrode layer and the second electrode layer and the inclination angle θ1 at which the Δf ratio is 1 in the third modification of the first embodiment. FIG. In FIG. 14, a white circular plot shows the result of a wavelength normalized film thickness of 2% of the Pt layer as the first electrode layer. The black circular plot shows the result that the wavelength-normalized film thickness of the Pt layer is 6%. The white square plot shows the result that the wavelength-normalized film thickness of the Pt layer is 7%. The black square plot shows the result that the wavelength-normalized film thickness of the Pt layer is 8%. The triangular plot shows the result of the wavelength normalized film thickness of the Pt layer being 9%.

  As shown in FIG. 14, the larger the wavelength-normalized film thickness of the second electrode layer, the larger the inclination angle θ1 at which the Δf ratio becomes 1. As described above, in the range where the inclination angle θ is 0 ° <θ ≦ θ1, the Δf ratio is 1 or more, and the relative bandwidth Δf can be broadened.

Here, in the third modification of the first embodiment, the wavelength normalized film thickness of the Pt layer as the first electrode layer is T _Pt, and the wavelength normalized film of the Cu layer as the second electrode layer. Let the thickness be T _Cu . As shown in FIG. 14, the wavelength normalized film thickness T _Pt of the first electrode layer is 2% or more and less than 7%, and the wavelength normalized film thickness T _Cu of the second electrode layer is 3 When the inclination angle is θ ≦ 3.3 × T _Cu -3.3, the Δf ratio can be more reliably made 1 or more, and the relative band Δf can be widened. The wavelength normalized film thickness T _Pt of the first electrode layer is 2% or more and less than 7%, and the wavelength normalized film thickness T _Cu of the second electrode layer is 3% or more, and the inclination angle is When θ ≦ 1.3 × T _Cu +2.4, the Δf ratio can be more reliably made 1 or more. On the other hand, when the wavelength-normalized film thickness of the first electrode layer is 7% or more, and the inclination angle θ ≦ 3.3 × T _Cu −3.3, the Δf ratio is more reliably 1 or more It can be done. The conditions which can make (DELTA) f ratio more reliably 1 or more are put together in following Table 6, and are shown.

By combining the combination of the inclination angle θ, the wavelength normalized film thickness T _Pt and the wavelength normalized film thickness T _{Cu with} the combination shown in Table 6, the Δf ratio can be more reliably made 1 or more, and the ratio is more reliably The band Δf can be broadened.

  FIG. 15 shows the relationship between the wavelength-normalized film thickness of the first electrode layer and the second electrode layer and the tilt angle θ1 at which the Δf ratio is 1 in the fourth modification of the first embodiment. FIG. In FIG. 15, the circular plot shows the result of the wavelength normalized film thickness of the Mo layer as the first electrode layer being 5%. The square plot shows the result of the wavelength normalized film thickness of the Mo layer being 7%. The triangular plot shows the result of the wavelength normalized film thickness of the Mo layer being 8%.

As shown in FIG. 15, as the wavelength-normalized film thickness T _Al of the Al layer as the second electrode layer increases, the inclination angle θ1 at which the Δf ratio becomes 1 increases. It can be seen that when the wavelength-normalized film thickness of the first electrode layer is 7% or more, the relationship between the wavelength-normalized film thickness of the second electrode layer and the inclination angle θ1 does not substantially change.

Further, as shown in FIG. 15, when the inclination angle θ ≦ 2.2 × T _Al +12.1, the Δf ratio can be more reliably made 1 or more, and the relative bandwidth Δf can be widened. Preferably, the inclination angle θ ≦ 2.2 × T _Al +12.1, and the wavelength normalized film thickness T _Al of the second electrode layer is 2% or more. In this case, the Δf ratio can be made to be 1 or more more reliably.

  FIG. 16 is an enlarged front cross-sectional view showing the vicinity of the electrode finger of the IDT electrode in the second embodiment.

  The present embodiment differs from the first embodiment in that the side surface 34 a of the first electrode layer 34 extends in parallel with the thickness direction of the IDT electrode 33. The elastic wave device of the present embodiment has the same configuration as the elastic wave device 1 of the first embodiment except for the above point.

  FIG. 17 is a view showing the relationship between the inclination angle θ and the ratio band Δf ratio in the first embodiment and the second embodiment. When the relationship shown in FIG. 17 is determined, the first electrode layer is a Pt layer having a wavelength normalized film thickness of 2%, and the second electrode layer is an Al layer having a wavelength normalized film thickness of 5%. In FIG. 17, the white circle plot shows the result of the first embodiment, the square plot shows the result of the second embodiment, and the black circle plot shows the result of the first comparative example. .

  As described above, in the first embodiment, the Δf ratio can be made larger than 1 and the relative band Δf can be made wider. Furthermore, as shown in FIG. 17, it can be seen that in the second embodiment, the relative bandwidth Δf can be made wider. In addition, in the second embodiment, the Δf ratio can be made larger than 1 even when the inclination angle θ is larger than 32 °. Thus, the ratio band Δf can be broadened in a wider range of tilt angles.

  The elastic wave device of each of the above embodiments can be used as a duplexer of a high frequency front end circuit or the like. An example of this is described below.

  FIG. 18 is a block diagram of a communication device and a high frequency front end circuit. Note that, in the same drawing, each component connected to the high frequency front end circuit 230, for example, the antenna element 202 and the RF signal processing circuit (RFIC) 203 are also illustrated. The high frequency front end circuit 230 and the RF signal processing circuit 203 constitute a communication device 240. The communication device 240 may include a power supply, a CPU, and a display.

  The high frequency front end circuit 230 includes a switch 225, duplexers 201A and 201B, filters 231 and 232, low noise amplifier circuits 214 and 224, and power amplifier circuits 234a, 234b, 244a and 244b. The high frequency front end circuit 230 and the communication device 240 in FIG. 18 are an example of the high frequency front end circuit and the communication device, and the present invention is not limited to this configuration.

  The duplexer 201A has filters 211 and 212. The duplexer 201B includes filters 221 and 222. The duplexers 201A and 201B are connected to the antenna element 202 via the switch 225. The elastic wave device may be a duplexer 201A or 201B, or may be a filter 211, 212, 221 or 222.

  Furthermore, the elastic wave device is also applied to a multiplexer including three or more filters, for example, a triplexer in which antenna terminals of three filters are shared, a hexaplexer in which antenna terminals of six filters are shared. Can.

  That is, the elastic wave device includes an elastic wave resonator, a filter, a duplexer, and a multiplexer including three or more filters. The multiplexer is not limited to the configuration including both the transmission filter and the reception filter, and may be configured to include only the transmission filter or only the reception filter.

  The switch 225 connects the antenna element 202 and a signal path corresponding to a predetermined band in accordance with a control signal from a control unit (not shown), and is formed of, for example, a single pole double throw (SPDT) type switch . Note that the number of signal paths connected to the antenna element 202 is not limited to one, and may be plural. That is, the high frequency front end circuit 230 may support carrier aggregation.

  The low noise amplifier circuit 214 is a reception amplifier circuit that amplifies a high frequency signal (here, a high frequency received signal) that has passed through the antenna element 202, the switch 225, and the duplexer 201A, and outputs the amplified signal to the RF signal processing circuit 203. The low noise amplifier circuit 224 is a reception amplifier circuit that amplifies a high frequency signal (here, a high frequency received signal) that has passed through the antenna element 202, the switch 225, and the duplexer 201B, and outputs the amplified signal to the RF signal processing circuit 203.

  The power amplifier circuits 234 a and 234 b are transmission amplifier circuits that amplify a high frequency signal (here, a high frequency transmission signal) output from the RF signal processing circuit 203 and output the amplified high frequency signal to the antenna element 202 via the duplexer 201 A and the switch 225. . The power amplifier circuits 244 a and 244 b are transmission amplifier circuits that amplify a high frequency signal (here, a high frequency transmission signal) output from the RF signal processing circuit 203 and output the amplified high frequency signal to the antenna element 202 via the duplexer 201 B and the switch 225. .

  The RF signal processing circuit 203 performs signal processing on the high frequency reception signal input from the antenna element 202 via the reception signal path by down conversion or the like, and outputs the reception signal generated by the signal processing. Further, the RF signal processing circuit 203 performs signal processing of the input transmission signal by up conversion or the like, and outputs a high frequency transmission signal generated by the signal processing to the power amplifier circuits 234a, 234b, 244a, 244b. The RF signal processing circuit 203 is, for example, an RFIC. The communication device may include a BB (baseband) IC. In this case, the BBIC processes the received signal processed by the RFIC. Also, the BBIC processes the transmission signal and outputs it to the RFIC. The reception signal processed by the BBIC or the transmission signal before the signal processing by the BBIC is, for example, an image signal or an audio signal.

  The high-frequency front end circuit 230 may include a duplexer according to a modification of the duplexers 201A and 201B instead of the duplexers 201A and 201B.

  On the other hand, the filters 231 and 232 in the communication device 240 are connected between the RF signal processing circuit 203 and the switch 225 without passing through the low noise amplifier circuits 214 and 224 and the power amplifier circuits 234a, 234b, 244a and 244b. The filters 231 and 232 are also connected to the antenna element 202 via the switch 225 in the same manner as the duplexers 201A and 201B.

  According to the high frequency front end circuit 230 and the communication device 240 configured as described above, the elastic wave device according to the present invention includes the elastic wave resonator, the filter, the duplexer, the multiplexer including three or more filters, and the like. The relative bandwidth can be broadened, and frequency variations hardly occur.

  The elastic wave device, the high frequency front end circuit, and the communication device according to the embodiments of the present invention have been described above by using the embodiments and the modifications thereof, but the present invention relates to any component in the embodiments and the modifications Another embodiment realized by combining the above, a variation obtained by applying various modifications to those skilled in the art without departing from the spirit of the present invention with respect to the above embodiment, a high frequency front end circuit according to the present invention The present invention also includes various devices incorporating a communication device.

  INDUSTRIAL APPLICABILITY The present invention can be widely used in communication devices such as cellular phones as elastic wave resonators, filters, duplexers, multiplexers applicable to multiband systems, front end circuits, and communication devices.

DESCRIPTION OF SYMBOLS 1 ... Elastic wave apparatus 2 ... Piezoelectric layer 3 ... IDT electrode 3a ... Electrode finger 4, 5 ... 1st, 2nd electrode layer 4a, 5a ... Side 6, 7 ... Reflector 8 ... Dielectric film 13 ... IDT electrode 14 adhesion layer 15 diffusion prevention layer 22 piezoelectric layer 24 support substrate 25 high sound velocity film 26 low sound velocity film 33 IDT electrode 34 first electrode layer 34a side surface 103 IDT electrode 104, 105 First and second electrode layers 104a, 105a: side surfaces 201A, 201B: duplexer 202: antenna element 203: RF signal processing circuit 211, 212: filter 214, low noise amplifier circuit 221, 222: filter 224, low noise amplifier circuit 225,. Switch 230: high frequency front end circuit 231, 232: filter 234a, 234b: power amplifier circuit 240: communication device 244a, 244b Power amps circuit

In the elastic wave device of the third comparative example, the side surface 104a of the first electrode layer 104 is inclined with respect to the thickness direction of the IDT electrode 103, and the side surface 105a of the second electrode layer 105 is in the thickness direction. It extends in parallel. A plurality of elastic wave devices of the third comparative example were manufactured by changing the inclination angle θ of the side surface 104 a of the first electrode layer 104 .

Claims (10)

A piezoelectric layer,
An IDT electrode provided on the piezoelectric layer;
A dielectric film covering at least a part of the IDT electrode;
Equipped with
The IDT electrode includes a first electrode layer and a second electrode layer stacked on the first electrode layer,
The wavelength normalized film thickness of the first electrode layer and the wavelength normalized film thickness of the second electrode layer normalized by the wavelength defined by the electrode finger pitch of the IDT electrode are each 1.25% or more And
The second electrode layer has a lower density than the first electrode layer,
The elastic wave device in which the side surface of the second electrode layer is inclined with respect to the thickness direction of the IDT electrode.   The elastic wave device according to claim 1, wherein a side surface of the first electrode layer is inclined with respect to the thickness direction.   The elastic wave device according to claim 1, wherein a side surface of the first electrode layer extends in parallel with the thickness direction. The second electrode layer is an Al layer,
Rayleigh wave is used as the main mode,
The resonance frequency of the Rayleigh wave is Fr, the resonance frequency of the SH wave which is the unnecessary wave is Fsh, the inclination angle of the first electrode layer and the second electrode layer with respect to the thickness direction is θ, and the second electrode layer the wavelength normalized thickness is taken as T _Al, the resonance frequency Fr, the resonance frequency Fsh, the inclination angle theta, and a combination of wavelength normalized thickness T _Al is a combination shown in Table 1 below, claims The elastic wave apparatus as described in 2.

The first electrode layer is a Pt layer,
The second electrode layer is an Al layer,
Rayleigh wave is used as the main mode,
The inclination angle of the first electrode layer and the second electrode layer with respect to the thickness direction is θ, the wavelength normalized film thickness of the first electrode layer is T _PT , and the wavelength normalized film of the second electrode layer the thickness is taken as T _Al, the inclination angle theta, the wavelength standardized thickness T _Pt, and a combination of wavelength normalized thickness T _Al is a combination shown in Table 2 below, according to claim 2 Elastic wave device.

The first electrode layer is a Pt layer,
The second electrode layer is a Cu layer,
Rayleigh wave is used as the main mode,
The inclination angle of the first electrode layer and the second electrode layer with respect to the thickness direction is θ, the wavelength normalized film thickness of the first electrode layer is T _PT , and the wavelength normalized film of the second electrode layer the thickness is taken as T _Cu, the inclination angle theta, the wavelength standardized thickness T _PT, and the combination of the wavelength normalized thickness T _Cu is a combination shown in Table 3 below, according to claim 2 Elastic wave device.

The first electrode layer is a Mo layer,
The second electrode layer is an Al layer,
Rayleigh wave is used as the main mode,
When the inclination angle of the first electrode layer and the second electrode layer with respect to the thickness direction is θ, and the wavelength normalized film thickness of the second electrode layer is T _Al , θ ≦ 2.2 × T The elastic wave device according to claim 2, which is _Al + 12.1. The elastic wave device according to claim 7, wherein the wavelength normalized film thickness T _Al of the second electrode layer is 2% or more. The elastic wave device according to any one of claims 1 to 8,
Power amplifier,
, High-frequency front end circuit. A high frequency front end circuit according to claim 9;
RF signal processing circuit,
A communication device comprising:

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