DE19712496A1 - Piezoelectric thin-film component - Google Patents

Abstract

The component comprises a substrate, a thin ferro-electric film which is formed through a Sol-Gel method on the substrate, and at least two upper electrodes arranged on the thin ferro-electric film. The thin ferro-electric film is a lead-titanate-zirconate or lead-titanate film which is polarized through applying a voltage at the upper electrodes.

Description

The present invention relates to piezoelectric Thin-film devices used for resonators and filters be used, which acoustic waves from the take advantage of piezoelectric components. The present The invention relates in particular to a piezoelectric Thin-film device in which a thin ferroelectric film of lead titanate zirconate (PZT) or lead titanate (PT) on one Substrate is deposited.

Piezoelectric thin-film devices are used in resonators and filters installed to as a converter between electrical To act signals and acoustic waves. Quartz, paraelectric AlN, CdS and ZnO and the like were reported as piezoelectric high frequency materials for these used piezoelectric components. In the last Years has been after filters with larger bandwidths and Resonators with wider resonant frequency ranges required; while having ferroelectric metal oxide materials such. B. Lithium niobate, lithium tantalate, lead titanate zirconate (PZT) and Lead titanate (PT) attracted attention. Efforts have been made in particular at the practical level Applications of PZT and PT made great have electromechanical coupling coefficients that the Efficiency of transformation between electrical signals and  indicate acoustic waves; There have been some ideas in this Direction proposed or disclosed.

Such examples include a piezoelectric thin film Device using a comb electrode as upper Electrode for generating a surface acoustic wave (Japanese Unexamined Patent Publication No. 5-145,370) and a piezoelectric thin film device, the Ground waves vibrated by applying a voltage Electrodes on and under a thin piezoelectric Film are arranged, is applied.

These examples only reveal the structure of piezoelectric Thin-film devices; they do not reveal enough Film deposition method, data, the piezoelectric Having thin film characteristics, and means for obtaining Filters that have desirable bandwidths, or from Resonators that have desirable oscillation frequencies.

In the conventionally used piezoelectric thin film Components using a thickness vibration must the lower electrode, because ground waves vibrated be applied by applying an electric field to electrodes which is responsible for a vertical polarization on and under the piezoelectric film are arranged as terminal Electrode for polarization to be uncovered (exposed). Thus, a piezoelectric film needs to be attached to the lower electrode be deposited so that a part of the lower electrode remains uncovered, z. B. a part of the lower electrode is uncovered by the evenly deposited piezoelectric film using an etching process is removed, or the lower electrode in front of a Deposition of the piezoelectric film partially masked becomes. Problems with thinner film materials that occur such complicated procedures to expose the lower  Electrode are durable, and in terms of interdiffusion between thin films have not been solved. Thus have Piezoelectric thin-film devices, the multilayer contain piezoelectric films, not yet practical Level reached.

An object of the present invention is therefore to to eliminate the disadvantages outlined above to disclose a piezoelectric thin film device, the one Configuration has the different difficulties of the Can overcome film deposition, and a piezoelectric To provide a thin film device, which is suitable for a filter a larger bandwidth and a resonator with a wide oscillation frequency range is used.

A piezoelectric thin film device according to a first Aspect of the present invention comprises a substrate, a formed on the substrate thin ferroelectric film and electrodes for applying a voltage to the thin ones ferroelectric film, wherein at least two upper Electrodes are provided as the electrodes, and the thin ferroelectric film a thin lead titanate zirconate (PZT) or lead titanate (PT) film formed by a sol Gel process is formed and by applying a voltage is polarized between the electrode.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, preferred embodiments of the piezoelectric thin film device according to the present invention described.

An embodiment of the present invention (Embodiment Type A) relates to a piezoelectric thin film device which oscillates ground waves by applying a voltage to electrodes on and under a thin piezoelectric film; and
Another embodiment (Embodiment Type B) relates to a piezoelectric thin film device that oscillates surface acoustic waves by using a comb electrode as the upper electrode.

These embodiments (A) and (B) will now be described with reference to FIGS Drawings described.

EMBODIMENT TYPE A

Fig. 1 includes isometric views illustrating an embodiment of the present invention; Fig. 1 (a) shows an embodiment of a Si substrate provided with an insulating layer; and Fig. 1 (b) shows an embodiment of a Si substrate provided with a thin diamond film thereon.

Fig. 2 is a front view illustrating another embodiment of the present invention;

Fig. 3 is an isometric view illustrating another embodiment of the present invention;

Fig. 4 shows another embodiment of the present invention, wherein Fig. 4 (a) is a front view and Fig. 4 (b) is a side view.

( Figure 5 shows an example of a Type B embodiment, described below, with comb electrodes forming an upper electrode).

In Figs. 1 to 5, each element having the same function is indicated by the same reference numeral.

In each embodiment, as described in FIG. 1, a piezoelectric thin film device is a piezoelectric thin film resonator comprising a substrate 1 , a lower electrode 2 formed on the substrate, and a thinner formed over a dielectric buffer layer on the lower electrode ferroelectric film 3 made of PZT or PT (not shown in the drawings) and at least two upper electrodes 4 (4A and 4B) formed on the thin ferroelectric film.

As a substrate of this type of a piezoelectric thin-film device are - although a Si substrate 1 can be obtained with an insulating layer 1 A in a simple manner - a single crystal or polycrystal diamond substrate and a single crystal or polycrystal diamond on Si substrate also preferably , With regard to the use of the piezoelectric thin film device, it is advantageous that the Si substrate 1 with insulating layer is as thin as possible. However, since an excessively thin film has a low mechanical strength, it is favorable that its thickness is about 100 to 300 μm.

A thin film of silicon oxide can be easily Insulating layer are deposited on the Si substrate, in With regard to the manufacturing process can also be a thinner Film of silicon nitride can be used. The insulating layer smoothes the substrate surface, prevents one Element diffusion during heat treatment and confers the substrate a sufficiently high mechanical strength. The result is that through a sol-gel process a thinner ferroelectric film of high quality can be obtained.  

Since the oxide film 1 A provides no anti-diffusion effects if it is excessively thin, or because it forms the substrate tears or wrinkles if it is excessively thick, it is preferable that the thickness is about 0.5 to 2 microns.

When a diamond substrate is used, an Si substrate 1 which is provided with a thin diamond film 1 D, low. Since the Si substrate 1 having the diamond thin film 1 D has sufficiently high mechanical strength, a high-quality thin PZT or PT film can be formed by a sol-gel method.

When the thin diamond film 1 D on the Si substrate 1 is excessively thin, the diamond is not easily oriented. In addition, it is difficult to obtain a smooth surface and improved mechanical strength. On the other hand, if the diamond film is excessively thick, a long time for film deposition is necessary, resulting in an increase in cost. In addition, the acoustic loss increases. Therefore, it is favorable that the thickness is about 1 to 30 μm.

It is preferable that the Si substrate 1 having a thin diamond film of the piezoelectric thin film device is as thin as possible. However, if it is excessively thin, its mechanical strength deteriorates unsatisfactorily. Thus, the advantageous thickness is about 200 to 600 microns.

It is advantageous if the thickness of the SiO 2 film 1 A, which is arranged on the back of the Si substrate, 0.5 to 1.5 microns.

Such a Si substrate 1 with a thin diamond film can be produced by preparing a thin diamond film having a desired thickness on a Si substrate by using a vapor-phase deposition method.

In the piezoelectric thin film device, type A, a lower electrode 2 must be formed on the insulating layer 1 A or the thin diamond film 1 D of the substrate 1 . As the lower electrode 2 , a conductive metal layer may be deposited by a vacuum deposition method using Pt, Ir, Al, or the like. The thickness is generally about 1,000 to 2,000 Å.

For depositing a thin ferroelectric film, it is preferable that a Ti layer (not shown in the drawings) is formed before deposition of the lower electrode 2 .

As a sol-gel method of shrinkage during Drying and heating steps in the deposition of a accompanied by thin ferroelectric film, is watching still a thin film deposited over 5 microns. Indeed is a thickness of the thin ferroelectric film of less less than 0.1 μm, as this is too little to be thinner Piezoelectric film to work. In contrast, if the Layer on the Si or diamond substrate containing an oxide film has, is deposited, can be a thin ferroelectric Film deposited with a relatively large thickness, by the Ti layer as an adhesive layer between the Si substrate and the lower electrode functions.

The Ti layer may be deposited by a sputtering method or the like, and it is preferable that the thickness is about 50 to 500 Å. For the deposition of the Ti layer, a thickness of less than 50 Å is not sufficient. In this type of the piezoelectric thin film device, a ferroelectric film containing PZT or PT is deposited on the lower electrode 2 . In the case of a thin PZT film, it is advantageous for depositing a high quality thin PZT film if a PbTiO₃ buffer layer (lead titanate or PT) not shown in the drawings is deposited before deposition of the PZT film. PT improves film characteristics because PT crystallizes at low temperature and can prevent lead diffusion into the PZT film deposited thereon.

The PT buffer layer may be as in the case of the thin PCT film also be deposited by a sol-gel method. Preferably, the thickness is about 0.01 to 0.1 microns. A Thickness of the thin PT film of less than 0.01 microns provides no satisfactory features, while a thickness of over 0.1 microns deteriorates the characteristics of the thin PCT film.

The thickness of the thin piezoelectric PZT film 3 according to the present invention need not be larger than 10 μm for a high frequency range. The thickness is preferably 0.1 to 10 μm, and more preferably 0.2 to 3 μm, and is set in this thickness range according to use. When the thin PZT film is excessively thin, satisfactory piezoelectric effects can not be obtained. On the other hand, if it is excessively thick, a high-quality film can not be formed.

As the upper electrodes 4 (4A and 4B), on the PZT or Pt thin ferroelectric film 3, by using a sputtering method by a stencil, a conductive metal layer similar to that for the lower electrode 2 as described above can be formed , The thickness is generally 1,000 to 2,000 Å.

In the present invention, two upper electrodes 4 A and 4 B are formed. The distance between the two upper electrodes 4 A and 4 B is larger than the thickness of the PZT or Pt thin ferroelectric film 3 .

If the distance between the upper electrode is smaller than the thickness of the PZT or Pt thin ferroelectric film 3 , a short circuit will occur if a voltage is applied to the polarization between the upper electrodes 4 A and 4 B. In this way, no polarization of the thin ferroelectric film in the vertical direction can be achieved. However, an excessively large distance between the upper electrodes causes an undesirable increase in device size.

Preferably, the distance between the upper Electrodes 2 to 200 times the thickness of the thin ferroelectric film, d. H. 0.2 to 2000 microns for a thin PZT or PT film with a thickness of 0.1 to 10 μm, and more preferably 10 to 100 times the thickness of the thin one ferroelectric film.

In the piezoelectric thin-film resonators is the Training a high quality thin PZT or PT film extremely important. The thin PZT film works as a thinner piezoelectric film with sufficient polarization. If However, the film quality is inferior, no to Polarization sufficient electric field can be applied and so the thin film can not be thinner act piezoelectric film.

As for polarization, an electric field between two upper electrodes - as already stated above - and not applied between the lower and upper electrodes can be a thin piezoelectric film, the  works satisfactorily, without difficulty conventional film deposition methods are obtained.

In the present invention, a hollow portion 5 may be formed by etching the side of the Si substrate 1 opposite to the side forming the lower electrode. Such formation of the hollow portion 5 allows for long oscillation of low modes and improves oscillation frequency and insertion loss characteristics, though the mechanical strength deteriorates slightly.

The hollow portion is preferably attached to a depth corresponding to 50 to 100% of that of the Si substrate 1 so as to be in a position on the opposite side of the upper electrodes 4 A and 4 B.

An insulating layer 6 may be partially formed on the ferroelectric film 3 , and the upper electrodes 4 A and 4 B as terminal electrodes are formed so as to bridge over the insulating layer 6 and the ferroelectric film 3 as shown in FIG. 3 is shown. The insulating layer may be formed of SiO₂, SiN, AlN, TiO₂, Al₂O₃, and the preferable thickness is about 0.05 to 1 μm.

When the insulating layer 6 is formed in this manner, the substrate Si may be provided with a hollow portion 5 , as shown in FIG .

In the following, a preferred embodiment of a Method for producing a piezoelectric thin-film Component, type A described.  

First, a Ti layer and a separately lower electrode on the surface of an oxidic Insulating layer mounted on a Si substrate, deposited by a process of sputtering.

Next, a liquid composition for formation of a thin PbTiO₃ film on the lower electrode applied and dried at 150 to 400 ° C, the liquid composition is prepared by adding a lead Connection such. As lead acetate and a titanium compound such as z. Example, titanium isopropoxide or titanium butoxide in a given Molar ratio in a solvent such. For example, methoxyethanol or an acetic acid ester, so that the Total weight of the solutes 1 to 10 wt .-% is. This The process is repeated until the PT buffer layer has a previously reached certain thickness.

In addition, a liquid composition for forming a thin PZT film by a method of Spin coating applied to it and at 150 to Dried at 600 ° C, the liquid composition is prepared by a lead compound such. B. a Lead carboxylate, for example lead acetate or a Lead alkoxide, for example lead diisopropoxide; a Zirconium compound such. For example, zirconium alkoxide Tetraethoxyzirconium, tetraisopropoxyzirconium, Tetrabutoxyzirconium or dimethoxydiisopropoxyzirconium; and a titanium compound such as. B. titanium alkoxide, for example Tetraethoxytitanium, tetraisopropoxytitanium, tetrabutoxytitanium or Dimethoxydiisopropoxytitan in a given molar ratio in a solvent such. B. 2-methoxyethanol dissolved so that the total weight of the dissolved compounds 10 to 20 wt .-%, expressed as metal oxides. This The process is repeated until the PZT film has a reaches predetermined thickness. The substrate is at 600 to  Dried at 700 ° C for 1 min to 1 h, using a thin PZT film is obtained.

On the resulting thin PZT film can by a Method of sputtering or a CVD method, when necessary, an insulating layer, such. B. an SiO₂ film, be deposited; then be through a process of Sputtering two upper electrodes in a given Pattern formed. An electric DC field with 200 to 500 kV / cm is at 120 to 200 ° C for 10 to 60 min applied between the two electrodes to allow the thin PZT Polarize film. After a polarization the thin PZT film as a thin piezoelectric film.

If a thin PZT film is not in sufficient quality has been formed, can not provide sufficient polarization the thin piezoelectric film can be achieved. Thus are in the present invention, the conditions for forming the Substrate, the lower electrode, the thin PZT film and the upper electrodes in the present invention optimized to produce a satisfactory thin PZT film manufacture.

When a hollow portion is formed by etching the Si substrate, as shown in FIGS. 2 and 4, the substrate may be formed by using an etching solution such as an etching solution. As tetramethylammonium hydroxide (TMAH) are partially removed.

The embodiment, type B, will now be described with reference to the drawings described.

Fig. 5 shows an embodiment, type B, according to the present invention, in which comb electrodes are formed as upper electrodes instead of the two electrodes in Figs .

In Figs. 1 to 5, elements having the same function are denoted by the same reference numerals.

With this type of embodiment, there is disclosed a surface acoustic wave device comprising a substrate 1 , a thin ferroelectric PZT or PT film 3 formed on the substrate 1 via a dielectric buffer layer, and upper comb electrodes 4 ( 4 a, 4 b, 4 c and 4 d) formed on the thin ferroelectric layer. An Si substrate 1 with an insulating layer 1 A is the most easily available substrate for this type of piezoelectric thin film device, but it can also be single crystal substrates such. As sapphire, MgO and SrTiO₃ be used.

Before a thin ferroelectric PZT or PT film 3 is formed on the substrate, a thin ferroelectric film, for example, a barium strontium titanate (BST) film, strontium titanate (STO) film or barium titanate (BTO) film may be preferably used as Buffer layer are formed on the substrate to produce a thin ferroelectric film 3 of high quality.

The thin BST, STO or BTO film buffer layer can be like the thin ferroelectric PZT or PT film through a sol-gel Procedures are formed. An excessively large thickness affects the piezoelectric characteristics disadvantageous, whereas an excessively small thickness the Loss of the lead anti-diffusion effect means. Therefore the thickness is generally 0.01 to 0.2 microns and preferably 0.01 to 0.15 microns.  

The thin ferroelectric film 3 is provided as a thin piezoelectric film formed on the buffer layer by using a thin, by a sol-gel process deposited film by means of DC voltage between the comb electrodes 4 a and 4 b and between the Comb electrodes 4 c and 4 d is applied, is polarized.

The thickness of the thin ferroelectric film used in this Manner was formed, depending on one desired resonant frequency and the electromechanical Coupling coefficients are determined and is in general 0.03 to 5 μm. At a thickness of less than 0.03 microns Surface acoustic waves do not oscillate while at a thickness of over 5 microns surface acoustic waves also due to errors in the film quality also not be oscillated.

The conductive film to form two upper comb electrodes is using a conductive material such. Al, Pt or Au according to a conventional method with Line width and line spacing (hereinafter referred to as L · S = line width and space), by the desired Characteristics depend in a conventional method patterned.

The polarization of the thin PZT or PT film can be achieved by applying a DC voltage of 20 to 50 V between two upper comb electrodes (between 4 a and 4 b and between 4 c and 4 d in FIG. 5) PZT or PT film are formed, can be achieved for 1 to 60 min. When the thin PZT or PT film is sufficiently polarized, the film operates as a thin piezoelectric film. However, if the thin PZT or PT film is of poor quality, it does not work as a thin piezoelectric film since no electric field sufficient for polarizing the film can be applied.

Hereinafter, a preferred embodiment of a Method for producing an acoustic Surface acoustic wave device as embodiment type B in Accordance with the present invention with reference to a acoustic PZT surface acoustic wave device having a silicon Substrate used, described.

First, on a Si substrate provided with an oxide film by a sol-gel method, a thin BST, STO or BTO film is formed as a buffer layer as follows:
A liquid composition for forming a thin BST, STO or BTO film is spin-coated on the Si substrate having an oxide film and dried at 400 to 600 ° C to prepare the liquid composition by adding barium - Connection such. Barium carboxylate, ie, barium 2-ethylhexanoate; a strontium compound such as. A strontium carboxylate such as strontium 2-ethylhexanoate; a titanium compound, such as. Example, a titanium alkoxide, for example, tetraethoxytitanium, tetraisopropoxytitanium, tetrabutoxytitanium or a Dimethoxydiisopropoxytitan and a carboxylic acid such as 2-ethylhexanoic acid or 2-ethylpropionic acid in a given molar ratio in a solvent such as. For example, isoamyl propionate can be dissolved so that the total weight of the dissolved compounds is 0.5 to 8% by weight, expressed in metal oxides. This process is repeated until the thin BST, STO or BTO film reaches a predetermined thickness. The substrate is fired at 600 to 700 ° C for 1 minute to 1 hour to obtain a thin BST, STO or BTO film.

Next, a thin ferroelectric PZT or PT Film with a similar process as the procedure for Formation of the thin ferroelectric PZT or PT film in Embodiment Type A described above the buffer layer is formed.

After upper comb electrodes, which is a conductive material such as As Al, Pt or Au, with a conventional Pattern forming method with a line width and a Line spacing according to the desired characteristics are formed on the thin PZT or PT film, the Thin PZT or PT film by applying a voltage between the two comb electrodes polarized, with an acoustic Surface wave device is completed.

(Application of Embodiment Type B)

As examples for explaining an application of Embodiment Type B according to the present invention a programmable surface acoustic wave resonator and a surface acoustic wave filter.

A conventional programmable surface acoustic wave device which can resave output codes as shown in Fig. 7 is disclosed by DP Morgan ("Surface Wave Device For Signal Processing" Elsevier, 1991, pp. 286-288). The programmable surface acoustic wave device comprises input comb electrodes 8 and a plurality of independent transducer elements 9 disposed on a paraelectric substrate 10 'and a voltage applying unit 7 for alternately applying a positive or negative voltage to these transducer elements 9 .

Each transducer element 9 comprises a first electrode and a second electrode 9 a 9 b, and the voltage applying unit 7, the a and 9 b applied voltage is positive or negative change between the first and second electrodes. 9 The polarization state of the paraelectric substrate 10 'between the electrode 9 a and 9 b is reversed by the polarity of the electrode between the 9 a and 9 b applied voltage is changed; the output code from the converter element 9 can be arbitrarily changed to 0 or 1.

The programmable surface acoustic wave device shown in Fig. 7 must be provided with the voltage applying unit 7 for operating the surface acoustic wave device; from the voltage application unit 7 , a voltage must be applied to each converter element 9 .

In contrast, a programmable acoustic Surface wave device that has a thin piezoelectric film in accordance with the present invention uses predetermined Generate output signals without a constant voltage the transducer element is created.

More specifically, a surface acoustic wave device according to the present invention, which is shown in Fig. 6, is provided with a transducer element on the piezoelectric substrate, the first electrode 12 a and second electrode 12 b, which are opposite to the first electrode comprises, and can prevent the output code or re-write by the polarity of the voltage which is applied between the first electrode 12 a and the second electrode 12 b is reversed. The piezoelectric substrate comprises a substrate main body and a thin ferroelectric film formed on the substrate main body. The thin ferroelectric film between the electrodes is polarized by a voltage applied between the first and second electrodes to set an output code. The set output code is retained by remanance even after removal of the applied voltage.

When a voltage is applied to the surface acoustic wave device of the present invention as shown in the example of Fig. 7, the thin dielectric film is polarized between the electrodes of the converter elements, and code 1 or 2 can be set in the converter element ,

However, if a thin ferroelectric film than Is used electrodes of the converter element, the remains Code described above due to the Remaneszens of ferroelectric material back. The by applying a Voltage to the transducer element set code can as set code from the surface acoustic wave Component can be output even after the voltage applying unit is removed.

In addition, the polarization state can be reversed, by applying a voltage with reversed polarity to the Transducer element is applied; in this way will the Output code cleared after the code in the Transformer element was entered. That way is the surface acoustic wave device programmable.

Accordingly, the surface acoustic wave Component as a programmable surface acoustic wave Resonator and programmable surface acoustic wave Filters are used. In an automatic  Identification system with the acoustic Surface wave component is equipped, an ID Code from a transponder (ID card) are rewritten.

The surface acoustic wave device in the above The above embodiment will now be described in more detail with reference to Drawings described.

Fig. 6 (a) is a plan view of the surface acoustic wave device, and Fig. 6 (b) is a circuit diagram of the voltage applying unit of the surface acoustic wave device.

Numeral 10 in the drawings denotes a surface of the thin ferroelectric film 3 containing PZT or PT and formed on the substrate main body; On the surface of the thin ferroelectric film 3 , a group of input comb electrodes 11 and a group of output comb electrodes (transducer elements) 12 are arranged. The group of input comb electrodes 11 consists of a first comb electrode 11 a and a second comb electrode 11 b, which are opposite to a certain distance.

The converter elements 12 consist of first electrodes 12 a and second electrode 12 b; four first electrode 12 a are connected in this embodiment as a comb, which is shown in the drawings. Each of the second electrodes 12 b is arranged straight and between adjacent first electrodes 12 a and 12 a.

In this embodiment, three converter elements 12 by three second electrodes 12 b, which are arranged between the first electrode 12 a, formed.

Each second electrode 12 b can be powered by batteries 14 and 15 in the voltage applying unit via a coil 16 and a switch 17 with power. Each second electrode 12 is connected via a capacitor 18 to an output terminal 19 to turn off DC voltage and pass AC voltage. The first electrodes 12 a are connected to the output terminal 20 . The first electrodes 12 a are connected via a ground to the batteries 14 and 15 .

In the surface acoustic wave device having such a configuration, by means of a changeover switch 17, both positive and negative voltages can be applied to the three converter elements 12 . When a positive voltage is applied to the three second electrode is applied 12 b, the output code [111], and if negative voltage is applied to this second electrode 12 b is applied, the output code [000]. By changing the polarity of b applied to this second electrode 12 voltages each combination can be obtained from 0 to 1.

Once a voltage is applied to each transducer element 12 by means of the voltage applying unit 13 , the set code is maintained by remanence of the thin ferroelectric film 3 after removal of the applied voltage (ie, if every second electrode 12 b is switched off by the batteries 14 and 15 is).

Therefore, the surface acoustic wave device can be operated after setting the code alone without the voltage applying unit 13 , as shown in Fig. 6 (c). The set code is changeable by reversing the voltage applied to each transducer element 12 using the voltage applying unit 13 .

Fig. 8 is a circuit which another voltage applying unit 13 'for applying a positive or negative voltage to each second electrode 12 b represents. Each electrode 12 b is connected via diodes which are arranged in parallel in the same or opposite direction, connected to a switching circuit. The circuit link 23 is connected to a positive or negative pulse generator 24 . A command signal is provided by a code generator 25 to the switching circuit 23 and the pulse generator 24 to determine the polarity of the applied voltage 12 b to each electrode.

The pulse generator 24 outputs a positive or negative pulse based on the signal from the code generator 25 ; the pulse is input through the circuit link 23 in one of the three electrodes 12 b. The code is set by the remanence of each transducer element 12 .

Although 3 converter elements are used in Fig. 6, the number of converter elements may be 2, 4 or more.

In addition, an output code can be set by a Tension in the input comb electrodes in the present Invention is created.

Fig. 9 (a) shows an embodiment in which reference numeral no. 11 'represents input comb electrodes and numeral no. 12 ' represents output comb transducing elements. Pulse voltages from a pulse generator 24 in the voltage applying unit 13 'are supplied through a circuit link 23 and diodes 22 to the input comb electrodes 11 '. Reference numeral 26 represents a unit including the diodes 26 and the capacitor 18 .

Fig. 9 (b) shows a surface acoustic wave device in which the polarity of each input comb electrode 11 "is changeable with switches 27 disposed on both sides of the input comb electrode.

In this embodiment, all the Materials for substrate, thin ferroelectric film and Electrodes described above (embodiment type B), preferably used.

As a further embodiment will be in the following Acoustic surface acoustic wave resonator and an acoustic Surface wave filter described.

As shown in FIG. 10, in the surface acoustic wave device of this embodiment, a lower electrode and a thin ferroelectric film are laminated on a substrate in the order named, a row of narrow first upper electrode 41 is parallel to the surface of the thin ferroelectric Films 3 are arranged and narrow second upper electrodes 42 between the first upper electrodes 41 are arranged. The thickness of the thin ferroelectric film is smaller than the distance between the first upper electrode 41 and the second upper electrode 42 . The device is equipped with a voltage applying unit for alternately applying a positive or negative charge to each upper electrode. In addition, elastic wave reflectors 50 are disposed on both sides of the upper electrode group consisting of the first and second upper electrodes along the electrode array.

When the substrate is conductive, the substrate itself may be a be lower electrode.  

Fig. 10 (a) is a plan view of the surface acoustic wave device according to the present invention; and Fig. 10 (b) is a cross section taken along the line BB in Fig. 10 (a).

A lower electrode 2 is attached to a rectangular substrate 1 and a thin ferroelectric film 3 is formed thereon.

In the middle of the substrate, narrow first upper electrodes 41 are formed in the longitudinal direction; between the first upper electrodes 1 narrow second upper electrodes 42 are formed. These first and second upper electrodes 41 and 42 are arranged in parallel in the transverse direction of the substrate. The first and second upper electrodes 41 and 42 are equidistantly spaced. The thickness of the thin ferroelectric film is smaller than the distance P between the first upper electrode 41 and the second upper electrode 42 .

Reflectors 50 are attached to both sides of the upper electrode group consisting of the first and second upper electrodes 41 and 42 . Each reflector 50 consists of a series of reflection sections 5 a parallel to the first and second upper electrodes 41 , 42 and short-circuit sections 50 b for connecting the reflection sections 50 a to each other. The distance between the reflecting portions 50 a is the same as that between the first and second upper electrodes 41 , 42 .

The upper electrodes 41 are connected via their respective capacitors 61 to a terminal 20 . Further, the upper electrodes 41 may be connected to the battery 14 or the battery 15 via their respective coils 42 and switches 81 . The positive electrode of the battery 14 is connected to the upper electrodes 41 , and the negative electrode of the battery 15 is connected to the upper electrodes 41 .

The upper electrodes 42 are connected via their respective capacitors 62 to a terminal 19 . Also, the upper electrodes 42 may be connected to the battery 14 or 15 through their respective coils 72 and switches 82 . The positive electrode of the battery 15 is connected to the upper electrodes, and the negative electrode of the battery 15 is connected to the upper electrodes 42 .

To the first and second upper electrodes 41 and 42 of the surface acoustic wave device having such a configuration, both positive and negative voltages may be applied. In oscillating this surface acoustic wave device, vibration waves generated by the electrode group are reflected by the reflectors 50 and generate a stationary wave, resulting in resonance. The resonance frequency depends on the voltage applied to the first and second upper electrodes 41 and 42 .

The resonance frequency is set to f when a positive or negative voltage is applied to all first and second upper electrodes 41 and 42 (Case 1 below). When a positive voltage is applied to the first upper electrodes 41 and a negative voltage is applied to the second upper electrodes (Case 2 below), the resonance frequency is 2 f. The resonance frequency is variable as follows by modifying the combination of the voltages applied to the first and second lower electrodes 41 and 42 .

If N 2 (where N is the number of the same polarities in the upper electrodes indicates) has an alternating arrangement N positive polarities (+) and N negative polarities (-) a resonant frequency of f / N.

After voltages are applied from the batteries 14 and 15 to the first and second upper electrodes 41 and 42 and the batteries are turned off, the resonance frequency characteristics due to remanence of the thin ferroelectric film 3 can be maintained. The polarity can also be reversed by applying the reverse voltage to produce a different resonant frequency.

This surface acoustic wave device can as programmable surface acoustic wave resonator or filters are used.

[Examples]

The present invention will now be described in more detail with reference to FIG Examples are described.  

Examples of the embodiment type A. EXAMPLES A1 to A16

By a method of sputtering were a Ti layer with a thickness of 500 Å and a Pt layer as lower electrode separated by a thickness of 2,000 Å a 250 μm thick Si substrate containing an oxide layer in a thickness of 1 micron, deposited.

With a sol-gel method was a thin PZT or PT film described in Table 1 on the PT layer as lower electrode deposited.

Before deposition of the thin PZT or PT film was a thin PT film having a thickness of 0.01 μm as a buffer layer deposited by a sol-gel method.

In the deposition of the PT buffer layer was a liquid Composition used to form the thin PT film, wherein the liquid composition by dissolving Lead acetate and titanium isopropoxide in methoxyethanol in one certain molar ratio was prepared.

In the PZT film deposition was a liquid Composition used to form the thin PZT film, wherein the liquid composition was prepared by a predetermined molar ratio of lead acetate, Zirconium butoxide and titanium isopropoxide in a solution were dissolved, so that the total content of dissolved Compounds 10 to 20 wt .-% was. The solution was through a spin-on and applied at 400 ° C. dried. The process was repeated until the film became a reached certain thickness. Finally, the educated thin PZT film fired for one hour at 650 ° C.  

An example of the liquid composition for formation of a thin PZT film (the total content as metal oxides: 20 % By weight) is the following:

lead acetate: 23.985% by weight tetrabutoxyzirconium: 11.455% by weight isopropoxytitanium 7.842% by weight 2-methoxyethanol: compensation

Upon deposition of the thin PT film, the thin PT film became directly without deposition of a buffer layer on the Pt layer of the lower electrode deposited.

In this case, a liquid composition was used for Formation of a thin PT film used, wherein the liquid Composition by dissolving lead acetate and Titanium isopropoxide in methoxymethanol in a given Mole ratio was prepared so that the total content of dissolved compounds was 10 wt .-% was.

With a sputtering method, two 70 μm × 70 μm square aluminum top electrodes having a thickness of 1,500 Å and an inter-electrode gap of 180 μm as shown in Fig. 1 were formed on the thin PZT or PT film.

Between the upper electrodes was at 150 ° C for 10 minutes a DC electric field of 300 kV / cm applied. The thin PZT and PT films were in the vertical direction polarized and thereby piezoelectric thin-film resonators manufactured.  

The fundamental resonance frequency of the vertical vibration of each resultant thin piezoelectric film is shown in FIG .

COMPARATIVE EXAMPLES A1 to A2

As in example A1 or A12, except the distance between the upper electrodes was 0.2 μm, which was smaller than the thickness of the thin PZT film and the thin PT film, became one thin PZT film and a thinner PT film.

The polarization of these films by applying a DC electric field was due to a short circuit unsatisfactory between the upper electrode.

EXAMPLE A17

It became a piezoelectric thin-film resonator, as in Example A1 except that the PZT film thickness is 0.8 μm and two rectangular (80 μm × 75 μm) upper aluminum Electrodes with an inter-electrode distance of 75 μm were formed. The resonance frequency and the Insertion loss are given in Table 2.

EXAMPLE A18

A piezoelectric thin-film resonator was fabricated as in Example A17 except that a hollow portion of 235 μm × 75 μm × 235 μm (depth) on the side of the Si substrate, that on the side where the upper electrodes were were formed opposite, was provided, as shown in Fig. 2. Resonant frequency and insertion loss are given in Table 2.

EXAMPLE A19

There was a piezoelectric thin-film resonator as in Example A12 except that the PZT film thickness is 0.8 μm was and two rectangular (80 microns × 75 microns) upper aluminum Electrodes with an inter-electrode distance of 75 μm were trained. Resonant frequency and insertion loss are given in Table 2.

EXAMPLE A20

A piezoelectric thin-film resonator was fabricated as in Example A19 except that a hollow portion of 235 μm × 75 μm × 235 μm (depth) was attached on the side of the Si substrate opposite to the side at which the upper electrodes were formed, as shown in Fig. 2. Resonant frequency and insertion loss are given in Table 2.

EXAMPLES A21 AND A22

After deposition of a thin PZT film and a thin PT film as in Example A7 and A20 was by a method of sputtering on this - but not in the vibration region - an SiO₂ film formed with a thickness of 1 micron, as shown in FIG 3 is shown. then, upper electrodes having an inter-electrode pitch of 10 μm were formed for the PZT film or 75 μm for the PT film so as to form a bridge between the SiO₂ film and the PZT or PT thin film. Two piezoelectric thin-film resonators were produced. In these thin film piezoelectric resonators, the area of the area formed on the PZT thin film was 70 μm × 70 μm, and the area of the portion formed on the PT thin film was 80 μm × 75 μm, the area It area, which was formed on the SiO₂ film, 100 microns × 100 microns. The width of the connection was 20 μm.

The impedance of the piezoelectric thin-film Resonators were compared with those of Examples A7 and A20 compared to the dependence of the impedance in the clarify the upper electrode area. The impedance of the piezoelectric thin-film resonators in Example A7 and A20 were approximately 50Ω and those in Examples A21 and A22 were also about 50 Ω. Thus, the change electrical characteristics with the resonator Configuration; it can reach a reinforced structure Be aware of the positions where the upper electrodes be trained to be moved.

Next, examples of deposition of a thin PZT or PT film using a thin film Diamond film substrate described.

EXAMPLES A23 AND A24

With a method of the sputtering were on a 250 micron thick Si substrate on which a thin diamond film with a thickness of 20 microns was formed, a Ti layer with a thickness of 500 Å and a Pt layer as the lower one Separated electrode with a thickness of 2 000 Å separately.

On the Pt layer as the lower electrode was by means of Sol-gel method a thin PZT or PT film with a Thickness of 0.8 microns deposited.

It was a liquid composition for PZT Film deposition used in the lead acetate, Zirconium butoxide and titanium isopropoxide in a given Molar ratio were dissolved in a solution, so that the  Total dissolved content was 18% by weight; to PT film deposition became a liquid composition used in the lead acetate and titanium propoxide in one certain ratio were dissolved in a solution, so that the total solids content was 10% by weight. This liquid Compositions were spin-coated and heated at 400 ° C dried. This procedure was repeated until the film reached a predetermined thickness, then the substrate became Fired at 650 ° C for 1 h.

Next, two rectangular (70 μm × 75 μm) upper electrodes 4 A and 4 B having a thickness of 1500 Å and an inter-electrode gap were patterned on the thin PZT or PT film by a sputtering method as described is shown in Fig. 1b.

Between the upper electrodes was at 150 ° C for 10 min a DC electric field with 300 kV / cm applied. Both the thin PZT and the PT film were in polarized in the vertical direction and thus piezoelectric Thin-film resonators produced.

The fundamental resonance frequency and the insertion loss of the vertical vibration for each resulting piezoelectric thin film are given in Table 3.

COMPARATIVE EXAMPLES A3 AND A4

A thin film PZT resonator and a thin film PT were used. Resonator as prepared in Examples A23 and A24, except that 250 microns thick Si substrates, a Had surface oxide film with a thickness of 1 μm, were used. The fundamental resonance frequency and the Insertion loss of vertical vibration for each thin Piezoelectric films are shown in Table 3.  

The results given in Table 3 illustrate that the insertion loss improves when a thinner Diamond film is used.

COMPARATIVE EXAMPLES A5 AND A6

It was a PZT thin-film resonator and a PT thin-film Resonator, as in Example A23 or Example A24 were used, with the exception that the electrode spacing 0.2 μm, which was smaller than the thickness of the thin PZT or the thin PT film. The resonators could because of a short circuit that occurred when a DC electric field between the upper electrodes was created, not polarized.

EXAMPLE A25

It became a piezoelectric thin-film resonator, as in Example A23 was prepared, but with the exception that the PZT film thickness was 0.8 microns and that two rectangular (80 microns × 75 microns) upper aluminum electrodes with a Electrode spacing were formed. The frequency resonance and the insertion loss are given in Table 4.

EXAMPLE A26

A piezoelectric thin-film resonator was fabricated as in Example A25 except that a hollow portion of 235 μm × 75 μm × 235 μm (depth) was formed on the side of the Si substrate facing the side on which the upper electrodes were formed opposite to each other, as shown in FIG . The frequency resonance and the insertion loss are shown in Table 4. The hollow portion does not affect the strength because of the thin diamond film deposited on the substrate.

EXAMPLE A27

After a thin PZT film was deposited as in Example A23, a SiO 2 film having a thickness of 1 μm was deposited on the thin PZT film except for the vibration region by a sputtering method; Then, the upper electrodes 4 A and 4 B, which had a thickness of 1500 Å, were formed with an electrode gap so as to form a bridge between the SiO₂ film and the PZT thin film. In this way, a piezoelectric thin-film resonator was produced. The area of the portion of the upper electrode formed on the thin PZT film was 70 μm × 70 μm; the area of the portion of the upper electrode formed on the SiO₂ film was 100 μm × 100 μm, and the width of the joint was 20 μm.

The impedance of this piezoelectric thin-film Resonator was compared with that of Example A23 to the Dependence of the impedance on the surface of the upper Clarify electrodes. The piezoelectric thin-film Resonators of Example A23 and A27 had about 50 Ω. In order to the impedance changes through such Configuration change not; it will be a reinforced one Structure by shifting the positions at which the Upper electrodes are formed reached.  

Examples of the embodiment type B EXAMPLES B1 to B7

On a single crystal Si substrate ( 3 inches in diameter, 250 μm in thickness) having a surface oxide film (1 μm in thickness), a thin BST buffer layer, a thin STO buffer layer, and a thin BST buffer layer were formed by a sol-gel method Separated BTO buffer layer with a thickness of 0.15 microns each separately; then a thin PZT film of 0.8 μm thick was deposited thereon.

To make the thin BST, STO, BTO, and PZT films were the following compositions with an apparatus applied to the spin coating and at 400 ° C. dried; this procedure was repeated until one before certain thickness was reached, then that became Substrate fired at 650 ° C for 1 h.

Liquid composition for BST film deposition (Total content of reduced metal oxides: 7% by weight):

Barium 2-ethylhexanoate: 9.514% by weight Strontium 2-ethylhexanoate: 3.598% by weight tetraisoproxytitanium: 9.205% by weight 2-ethylhexanoic: 18.50% by weight isoamylpropionate: compensation

Liquid composition for STO film deposition (Total content of reduced metal oxides: 7% by weight):

Strontium 2-ethylhexanoate: 14.269% by weight tetraisoproxytitanium: 10.950% by weight 2-ethylhexanoic: 22.0% by weight isoamylpropionate: compensation

Liquid composition for BTO film deposition (Total content of reduced metal oxides: 7% by weight):

Barium 2-ethylhexanoate: 12.722% by weight tetraisoproxytitanium: 8.616% by weight 2-ethylhexanoic: 17.31% by weight isoamylpropionate: compensation

Liquid composition for PZT film deposition (Total content of the reduced metal oxides: 20% by weight):

lead acetate: 23.985% by weight tetraisoproxytitanium: 7.842% by weight 2-methoxyethanol: compensation

Aluminum comb electrodes having the pattern shown in Fig. 5 (LAS is shown in Table 3) were formed; The thin PZT film was polarized by applying a DC voltage of 30 V between comb electrodes 4 a and 4 b and between comb electrodes 4 c and 4 d for 10 min.

The surface acoustic wave device oscillates acoustic surfaces due to a surface deformation caused by the piezoelectric effect when an electric signal is given between the electrodes 4 a and 4 b. When the distance between the electrodes 4 c and 4 d is half the surface acoustic wave wavelength, surface acoustic waves are largely oscillated and the device operates as a surface acoustic wave device.

It was an electrical signal between the electrodes 4 a and 4 b of the surface acoustic wave device brought and the output signal from the electrodes 4 c and 4 d measured. The fundamental resonance frequencies given in Table 5 were observed.

EXAMPLES B8 TO B10

In each example, a thin PZT film with a thickness was used of 0.8 .mu.m by a sol-gel method on mirror-thin Single crystal sapphire (5 cm × 5 cm × 0.7 mm depth) deposited. The liquid composition for PZT film deposition and the conditions are the same as those described above and used to deposit the thin PZT film were.

There were upper comb electrodes with different Electrode distance (LAS is given in Table 4) formed and the thin PZT film was under the same Conditions as above in the production of an acoustic Surface wave device polarized.

It was an electrical signal between the electrodes 4 a and 4 b of the surface acoustic wave device brought and the output signal from the electrodes 4 c and 4 d measured. The fundamental resonance frequencies given in Table 6 were measured.

Since the polarization directions between the upper electrodes In these examples, the frequency is two times the one that occurs when the polarization directions are vertical are equal to the comb electrodes.

EXAMPLE B11

As in Example B4, a thin PZT film having a thickness of 1 μm was deposited on the Si substrate. The electrode pattern indicated in Fig. 6 having a line width (L • S) of μm was formed on the thin PZT film. Each crossing length between the electrodes 11 a and 11 b and between the electrodes 12 a and 12 b was set to 400 microns. The batteries 14 and 15 had a voltage of 30 V.

To each transducer element in the acoustic Surface wave device, such a Configuration has been a positive or negative voltage applied; The code was removed by removing the voltage set. When input pulses with a pulse duration of 500 ns was applied, was a signal waveform, the corresponded to the set code. The entered Code has been changed repeatedly and always one Signal waveform corresponding to the inputted code, output.

As stated above, the set code is rewritable in the present invention, the acoustic Surface wave device and thus the resonator, filter and the ID card using the same can after Removal of the voltage applied to the code setting work.

The surface acoustic wave device according to Code Setting without the tension applying unit alone can work, it is lightweight and compact.

EXAMPLE B12

On a 4 inch silicon substrate, a thin PZT film having a thickness of 1 μm was formed by a sol-gel method. Then, aluminum electrodes 41 and 42 having a thickness of 0.1 μm as shown in Fig. 10 with a line width and a line pitch of 4 μm were patterned on the thin PZT film. Reflectors 50 having the same line width and line spacing of the reflection area were arranged. The voltage of batteries 14 and 15 was 30 volts.

A positive voltage was applied to the upper electrodes 41 and 42 of the surface acoustic wave device and removed again. The surface acoustic wave device oscillated at an oscillation frequency of 200 MHz. A signal waveform corresponding to the input code was always output. The resonance frequency was 400 MHz when the voltage pattern of Case 2 was applied; the resonance frequency was 100 MHz when the voltage pattern of case 3 was applied; and the resonance frequency was 66 MHz when the voltage pattern of Case 4 was applied.

It became a lower Pt electrode with a thickness of 0.2 microns formed on a MgO substrate. Using the MgO Substrate was made as above, an acoustic Surface wave component manufactured. The component had the same resonant frequency as that described above has been.

[ADVANTAGES]

Since a thin piezoelectric PZT or PT film in one piezoelectric thin-film component, embodiment type A according to the present invention as described above is used, the piezoelectric thin film device as a filter with a large bandwidth and as a resonator with a wide oscillation frequency work.  

Because the two upper electrodes at a certain distance are arranged, it is not necessary that the lower Electrode is used as a terminal electrode. This is No arduous steps to expose the bottom Electrode required; the piezoelectric Thin film resonator can be easily produced.

By forming a thin dielectric buffer film such as z. B. a BST, STO or BTO film can be a cheap Single crystal Si substrate can be used, resulting in a Cost reduction leads.

As a piezoelectric thin film device, the Resonant frequency can change, in another Embodiment obtainable according to the present invention is, the set code can be changed. The piezoelectric thin-film device can after removal of the voltage applied to the code setting work, and will because of its easily changeable Resonant frequency preferably in resonators, filters and ID Cards inserted.

The piezoelectric thin film device can after Setting the resonance frequency (of the code) alone without the Voltage applying unit can be used and is therefore lightweight and compact.  

[BRIEF DESCRIPTION OF THE DRAWINGS] [ Fig. 1]

Isometric views illustrating one embodiment Type A of the present invention; Fig. 1 (a) shows a Si substrate, and Fig. 1 (b) shows a Si substrate having a thin surface diamond film.

[ Fig. 2]

A front view showing another embodiment type A of the present invention.

[ Fig. 3]

An isometric view showing another embodiment Type A of the present invention.

[ Fig. 4]

Drawings illustrating still another embodiment type A of the present invention; Fig. 4 (a) is a front view and Fig. 4 (b) is a side view.

[ Fig. 5]

A top view showing a pattern of an upper comb electrode a surface acoustic wave device used in Embodiment Type B of the present invention is used is, represents.  

[ Fig. 6]

Drawings showing a configuration of the surface acoustic wave device, embodiment type B of the present invention; Fig. 6 (a) is a plan view, Fig. 6 (b) is a voltage applying unit circuit, and Fig. 6 (c) is a block diagram showing the state without the voltage applying unit.

[ Fig. 7]

A block diagram of a conventional acoustic Surface acoustic wave component.

[ Fig. 8]

A circuit that is another voltage applying unit which in one embodiment is type B of the present invention is used.

[ Fig. 9]

A block diagram of a surface acoustic wave Component according to another embodiment type B of present invention.

[ Fig. 10]

Drawings showing a configuration of a surface acoustic wave device in accordance with Embodiment B of the present invention; Fig. 10 (a) is a plan view and Fig. 10 (b) is a cross section taken along the line BB in Fig. 10 (a).

LIST OF REFERENCE NUMBERS

1 substrate (Si substrate)
1 A insulating layer (silicon oxide film)
1 D thin diamond film
2 lower electrode
3 Thin ferroelectric film (thin PZT or PT film)
4 A, 4 B Upper electrode
4 a, 4 b, 4 c, 4 d Upper comb electrode
5 Hollow section
6 insulating layer
8 , 9 Upper comb electrode in a conventional device
10 substrate surface of a thin ferroelectric film
10 ' substrate surface of a thin paraelectric film
11 , 11 ' Upper comb input electrode
11 a, 11 b, 12 a, 12 b electrode
13 , 13 ' tension applying unit
14 , 15 battery
17 switches
19 , 20 output terminal
22 diode
23 circuit connection
24 pulse generator circuit
25 code generator
41 First upper electrode
42 Second upper electrode
50 reflector
61 , 62 condenser
71 , 72 Resistor

Table 1

Table 2

PZT

PT

Table 3

Table 4

Table 5

Table 6

Claims (21)

1. Piezoelectric thin-film component comprising a substrate, one by a sol-gel method on this substrate trained thin ferroelectric film and Electrodes for applying a voltage to the thin comprising electrical film, wherein at least two upper Electrodes are arranged as the electrodes and the thin ferroelectric film a thin one Lead titanate zirconate (PZT) or lead titanate (PT) film is by applying a voltage between the Electrodes are polarized. 2. A piezoelectric thin film device according to claim 1, wherein the piezoelectric thin film device a thin piezoelectric resonator is the one Substrate, a lower one formed on the substrate Electrode, one formed on the lower electrode thin ferroelectric film containing PZT or PT, and two on the thin ferroelectric film attached electrodes, wherein the thin ferroelectric film by applying a voltage is polarized between the upper electrodes. 3. A piezoelectric thin film device according to claim 2, wherein the thin ferroelectric film, the PZT or PT contains, is formed by a sol-gel process and has a thickness between 0.1 and 10 microns.   4. A piezoelectric thin film device according to claim 2, wherein the substrate is a Si substrate, which is provided with a Insulating layer is provided, a single crystal or Polycrystalline diamond substrate, or a Si substrate, the with a thin single crystal or polycrystalline Diamond film is provided. 5. A piezoelectric thin film device according to claim 2, wherein the substrate is a Si substrate, which is provided with a Insulating layer is provided, and the thin is ferroelectric film containing PZT or PT at the lower electrode which formed on the substrate is formed over a dielectric buffer layer becomes. 6. A piezoelectric thin film device according to claim 5, wherein the dielectric buffer layer is a through Sol-gel process is formed lead titanate (PT) layer and has a thickness of between 0.01 and 0.3 μm. 7. A piezoelectric thin film device according to claim 2, the distance between the two upper electrodes greater than the thickness of the thin ferroelectric film, which contains PZT or PT is. 8. A piezoelectric thin film device according to claim 7, the distance between the two upper electrodes 2 to 200 times the thickness of the thin one ferroelectric film containing PZT or PT is. 9. A piezoelectric thin film device according to claim 2, wherein by etching on the side of the substrate, the where the lower electrode is formed opposite lies, a hollow section is formed.   10. A piezoelectric thin-film component according to claim 1, wherein the piezoelectric thin film device a Acoustic surface acoustic wave device is the one Substrate, one by a sol-gel method on the lower electrode formed thin ferroelectric Film containing PZT or PT and at least two upper ones Comb electrodes on the thin ferroelectric Film are formed, includes, and wherein the thin ferroelectric film by applying a voltage is polarized between the upper electrode. 11. A piezoelectric thin film device according to claim 10, wherein the thin ferroelectric film, the PZT and PT contains, is formed by a sol-gel process and has a thickness between 0.03 and 5 microns. 12. A piezoelectric thin film device according to claim 10, wherein the piezoelectric thin film device a Acoustic surface acoustic wave device is the one Si single crystal substrate covered with an insulating layer is provided, a thin ferroelectric film, the PZT or PT contains and by a dielectric Buffer layer on the Si single crystal substrate is formed, and two on the thin ferroelectric film formed upper crest Includes electrodes. 13. A piezoelectric thin film device according to claim 12, wherein the dielectric buffer layer is protected by a sol-gel Process is formed and barium strontium titanate (BST), strontium titanate (STO) or barium titanate (BTO) contains. 14. A piezoelectric thin film device according to claim 10, wherein the substrate is a Si single crystal substrate having  an insulating layer is provided, a single crystal or Polycrystalline diamond substrate, or a single crystal Substrate, sapphire, magnesium oxide or Contains strontium titanate is. 15. A piezoelectric thin-film component according to claim 10, where the polarization direction of the thin ferroelectric film containing PZT or PT, in is suitably changeable by alternately a positive or negative tension between the two upper comb electrodes is applied. 16. A piezoelectric thin film device according to claim 15, the distance between the two upper electrodes greater than the thickness of the thin ferroelectric film, which contains PZT or PT is. 17. A piezoelectric thin film device according to claim 15, wherein the piezoelectric thin film device with a Stress applying unit for alternate application a positive or negative voltage between the equipped with two upper electrodes, one Output code is set by the thin ferroelectric film by alternately applying positive or negative voltage between the Electrodes polarized, and the output code after Removal of the applied voltage by means of remanence is maintained. 18. Acoustic surface acoustic wave resonator or filter, the piezoelectric described in claim 15 Thin-film device used.   19. ID card for an automatic identification system, the piezoelectric described in claim 15 Thin-film device used. 20. A surface acoustic wave device comprising: a bottom electrode and a thin one ferroelectric film, in this order laminated to a substrate; a series of narrow ones first upper electrodes on the thin ferroelectric film are arranged; a row of narrow second upper electrodes between the first upper electrodes are arranged, wherein the Thickness of the ferroelectric film is smaller than that Distance between the first upper electrode and the second upper electrode; putting on a tension Unit for alternately applying a positive or negative voltage; a reflector for elastic Waves, along both sides of the direction of the Electrode grouping of the upper electrode group, the comprising the first and second upper electrodes, is arranged. 21. Acoustic surface acoustic wave resonator or filter, the piezoelectric described in claim 20 Thin-film device used.