JP3851336B1 - Surface acoustic wave device - Google Patents

Abstract

The present invention relates to a structure of a leaky surface acoustic wave filter or a leaky surface acoustic wave vibrator for the purpose of high performance and high stability of a surface acoustic wave device, and has a third-order temperature characteristic and extremely low loss fluctuation. A stable surface acoustic wave device is provided.
A rotating Y-cut quartz plate 400 cut at a film thickness of zero and a cut angle of 16.2 ° is provided with an air gap 404 and an IDT electrode 402 having a period of 2 Lp for exciting a leaky surface acoustic wave. Reference numeral 403 denotes an IDT electrode that receives the leaked surface acoustic wave. Since the IDT electrode is formed in the gap space above the quartz plate surface with the dielectric and the gap space in between, the electric field in the gap space that contributes to the excitation efficiency of the leaky surface acoustic wave on the quartz plate is There is a feature that the electric field in the air gap space on the εS crystal plate becomes stronger due to the weakening.
[Effect] By inserting a dielectric in the gap between the IDT electrode and the quartz plate surface, the electric field strength is increased and no mass load is applied to the surface acoustic wave, so that the above-mentioned problems can be overcome.
[Selection] Figure 4

Description

  The present invention is applicable to a surface acoustic wave device realized by using a leaky surface acoustic wave, and more specifically to all surface acoustic wave filters and surface acoustic wave vibrators. In particular, leakage elasticity for the purpose of high-performance and high-stability surface acoustic wave devices as the heart of optical modules in mobile communication fields and optical communication fields where high stability and high functionality are required The present invention relates to the structure of surface wave filters and leaky surface acoustic wave vibrators, and provides a highly stable surface acoustic wave device having third-order temperature characteristics and extremely low loss fluctuation.

In fields such as mobile communication devices and optical communication devices that require ultra-compact and high stability, surface acoustic wave filters have particularly established themselves as essential electromechanical functional devices. Since the surface acoustic wave filter is manufactured by the same photolithography technology as LSI, it is a device that can be mass-produced. Until now, ST-cut quartz having a parabolic frequency temperature characteristic curve having a frequency variation of 1 ppm / ° C. has been used for a long time as a surface acoustic wave device. This ST-cut crystal is inferior in temperature characteristics as compared with an AT-cut crystal having a third-order temperature characteristic curve of a bulk wave. Until now, cut surface acoustic wave waves with tertiary temperature characteristics have been investigated in various places, but unfortunately they could not be found by Rayleigh wave exploration. However, as described in Patent Document 1, during the experiment, the third-order leaky surface acoustic wave of the Y-cut (right-handed Euler angle near 15 °) belonging to the BT side of the world's first Y-cut quartz crystal in the world. An LST cut having temperature characteristics was discovered. Then, by conducting a detailed examination of this LST cut, it was found that the film thickness dependence was high as in the case of the bulk wave, and that the loss variation was particularly large at high temperatures. This is due to the fact that the propagation loss of the leaky surface acoustic wave is due to the temperature dependence of the propagation loss increasing or decreasing with respect to the temperature change. As a countermeasure, the cutting angle can be corrected by 0.6 °. It was also found to be the most effective. In order to obtain a cubic curve similar to that of an original AT-cut quartz crystal, it is necessary to remove the constraint from the film thickness inherent to the leaky surface acoustic wave. Unlike the silicon device, the surface acoustic wave device uses a piezoelectric crystal. Therefore, when the electrode film is formed on the piezoelectric crystal, the surface acoustic wave has a piezoelectric reaction and a mass load effect. In particular, the SAW filter as a leaky surface acoustic wave using an LST-cut crystal has a temperature characteristic that the conventional SAW filter using a Rayleigh wave appears in the form of a shift of the peak temperature of the center frequency of the mass load. temperature characteristic of the fact that changes in tertiary or linear, LST cut will be strongly affected by the electrode film thickness. In order to optimize the frequency stability, it is necessary to control both parameters of the cut angle and the film thickness. Usually, the propagation loss of the leaky surface acoustic wave is small, but the insertion loss increases rapidly when the temperature characteristic is on the high temperature side. Although the temperature characteristics of the insertion loss of the leaky surface acoustic wave have a large cut angle dependency, the influence of the electrode film thickness is not so great. Therefore, the temperature characteristic of insertion loss can be corrected by the cut angle if the electrode film thickness can be ignored.

  Current mobile communication equipment uses an AT-cut crystal overtone crystal oscillator as its frequency oscillation source, and obtains the required high frequency with a multiplier circuit. For this reason, the multiplication not only deteriorates the C / N and phase distortion of the crystal oscillator, but also hinders the improvement in performance and size and weight of the set. Therefore, surface acoustic wave vibrators that have the third-order temperature characteristics comparable to those of AT-cuts and can oscillate directly at high frequencies have long been the goal of research and development.

As a method of eliminating the mass load effect of an interdigital finger (IDT) electrode of a surface acoustic wave device, there are Patent Document 2 and Patent Document 3. Patent Document 2 includes a piezoelectric substrate, a comb electrode disposed above the piezoelectric substrate via an air gap, and an insulator bridge made of a non-piezoelectric material that supports the comb electrode. A surface acoustic wave element that excites or receives surface acoustic waves on a piezoelectric substrate through a gap. In the 13th to 14th lines in the upper right of page 3 of [Example] of the cited patent document 2, it is described that "the parts of the comb-shaped electrodes 3a and 3b are fixed so as to be suspended from the back surface of the insulator bridge 4". ing. Patent Document 3 provides an IDT electrode for transmitting and receiving a leaky surface acoustic wave formed opposite to a rotating Y-cut quartz crystal LST cut substrate with a gap layer interposed therebetween, and an extraction electrode portion that is electrically connected to the IDT electrode. In the transversal surface acoustic wave device constructed from the above, the IDT electrode part is formed on an insulating single or composite film provided with a gap so as to surround the leakage surface acoustic wave vibration region of the rotated Y-cut quartz LST cut substrate The surface acoustic wave device has a leaky surface acoustic wave device structure that is not affected by the electrode film thickness load.

JP 61-84105 A Japanese Patent Application No. 03-6912 JP 2003-17969 A "Excitation of surface acoustic wave to piezoelectric plate by interdigital electrodes", Tohoku University Research Institute of Electrical Communication, 120th Acoustical Engineering Meeting, 26 November 1965 "Examination of characteristics improvement of leaky surface acoustic wave propagating through quartz LST cut", IEICE Tech .: US-2001-53 (2001-09)

In the third to fourth lines from the top of page 3 of Non-Patent Document 1, the electric field of the electrode placed in the vicinity of the surface is not attached to the direct surface of the piezoelectric material, which is a superordinate concept as a surface wave excitation method. The method of excitation is shown. This method is a method of eliminating the mass load effect of the IDT electrode of the surface acoustic wave device, and this is a method of exciting a leaky surface acoustic wave with a comb-shaped electrode disposed through a spatial air gap. As the position of the IDT electrode moves away from the surface of the quartz plate, the excitation intensity of the surface acoustic wave and the received signal decrease, and the electric field intensity that can be transmitted and received by the IDT electrode becomes weaker. FIG. 7 of Non-Patent Document 2 shows the received electric field intensity distribution of the leaky surface acoustic wave obtained using the distance from the surface of the quartz plate of the IDT electrode provided in the space as a parameter. Patent Document 2 and Patent Document 3 are positioned as subordinate concepts different from the structure of Non-Patent Document 1 as the surface acoustic wave excitation method, and an external view thereof is shown in FIG. 10 and a sectional view thereof is shown in FIG. The rotating Y-cut quartz plate 1000, provided IDT electrode 1002 for vibration excitation of the leaky surface acoustic wave is provided a void space 1004 (1003). The electrode period of the IDT electrode 1002 (1003) is 2 Lp. Reference numeral 1003 (1002) denotes an IDT electrode that receives the leaked surface acoustic wave. The electric field distribution of the IDT electrode provided with this air gap is shown in FIG. Electric field distribution in the rotating Y-cut quartz plate 300 via a spatial void space 304 insulating film 301 is IDT electrode to vibration excitation of the leaky surface acoustic wave on the rotation Y cut quartz plate 300 is indicated by arrows. In the cross-sectional view of FIG. 11, IDT electrodes 1102 and 1103 supported by an insulating film 1101 are formed on a rotating Y-cut quartz plate 1100 with a gap space 1104 interposed therebetween. The method of exciting a leaky surface acoustic wave with an IDT electrode arranged through an air gap causes the excitation intensity of the leaky surface acoustic wave and the received signal to deteriorate as the arrangement of the IDT electrode moves away from the surface of the quartz plate. It is necessary to make the gap between the IDT electrode and the rotated Y-cut quartz plate very close.

Surface acoustic wave filter and a surface acoustic wave oscillator LSAW vibration region including the IDT electrodes and the reflectors with the use frequency domain in 70MHz～3GHz (area providing the air gap) is a 0.004 mm ² to 3 mm ² Very small area. The thickness of a simple substance or a composite film made of a dielectric material that spatially supports the IDT electrode through a gap is several thousand to several μm, and the mechanical strength is sufficient. As a means for solving the conventional problems, a transversal type in which an IDT electrode for transmitting and receiving a leaky surface acoustic wave formed opposite to a rotating Y-cut quartz crystal LST cut substrate of the present invention via a gap layer is provided. The surface acoustic wave filter has a structure in which an air gap space is formed on the surface of the rotating Y-cut quartz LST cut substrate, a dielectric is formed thereon, and an IDT electrode that excites a leaky surface acoustic wave is formed on the dielectric in a laminated form. By providing the surface acoustic wave filter, the problems of the surface acoustic wave excitation intensity and the deterioration of the received signal due to the conventional spatial excitation method can be solved. The resonator-type surface acoustic wave resonator according to the present invention includes a reflector having a groove structure or a metal electrode embedded structure on a rotating Y-cut quartz LST cut substrate to form a pair of reflective electrode structures. in resonator-type surface acoustic wave resonator made up of an IDT electrode which makes vibration excitation of the leaky surface acoustic wave which is formed with a gap space at a predetermined position between the reflecting electrodes, the surface of the rotating Y-cut quartz LST cut substrate In this structure, a dielectric is formed on the gap, and a cross-fingered electrode is formed on the dielectric to excite the leaky surface acoustic wave. To provide a highly stable and highly reliable surface acoustic wave resonator that is not affected. The method for exciting a leaky surface acoustic wave according to the present invention is widely applicable to Rayleigh waves , which are surface acoustic waves.

  The present invention is a transversal type having a structure formed in a dielectric having a gap so that an IDT electrode for exciting a leaky surface acoustic wave surrounds the leaky surface acoustic wave vibration region of a rotating Y-cut quartz LST cut substrate. A surface acoustic wave filter and a resonator type surface acoustic wave vibrator can also be provided.

Next, the operational characteristics of the surface acoustic wave device of the present invention will be described with reference to the drawings based on examples. 1 and 2 show a cross-sectional view of an IDT electrode per period of an IDT electrode portion of a surface acoustic wave device having a basic configuration of the present invention and an electric field distribution thereof. 1 shows that when the IDT electrode is formed on the surface of the dielectric, the electric field in FIG. 1 to which the voltage V is applied is the distance between the IDT electrode and the crystal plate d, and the relative permittivity ε of the dielectric 101 Assuming that _S and the thickness are d ₁ , the electric field strength of the dielectric 101 and the space 104 is expressed by Equation 1. Since the left side of Equation 1 is Equation 2, the electric field in the space that contributes to the excitation efficiency of the leaky surface acoustic wave becomes stronger as the electric field in the dielectric is weakened. Even if the position of the IDT electrode is extremely far from the surface of the quartz plate, the excitation intensity of the leaky surface acoustic wave and the received signal are hardly lowered. The integrated structure of the IDT electrode and the dielectric is the most efficient excitation method for exciting leakage elasticity through the air gap.

  As one of the best modes for carrying out the present invention, leakage elasticity formed to face a rotating Y-cut quartz LST cut substrate cut out at a right-handed Euler angle of 15 ° to 17 ° with a gap layer interposed therebetween. In a transversal surface acoustic wave device with an IDT electrode that transmits and receives surface waves, an air gap space is formed on the surface of a rotating Y-cut quartz LST cut substrate, a dielectric is formed on the surface, and a leaky surface acoustic wave is excited on the dielectric. In other words, the surface acoustic wave filter has a laminated structure as an IDT electrode, or the IDT electrode portion is formed in a dielectric.

  As one of the best modes of the surface acoustic wave vibrator for carrying out the present invention, a groove structure or an LST cut substrate cut out at a right-handed Euler angle of 15 ° to 17 ° is used. An IDT electrode for exciting a leaky surface acoustic wave formed through a gap layer at a predetermined position between the reflective electrodes by forming a pair of reflective electrode structures by providing reflectors with a metal electrode embedded structure facing each other. In the resonator-type surface acoustic wave resonator, the IDT electrode excites a space on the surface of the rotating Y-cut quartz LST substrate, a dielectric on it, and a leaky surface acoustic wave on the dielectric. It is a resonator type surface acoustic wave resonator having a laminated structure as an IDT electrode, and a resonator type surface acoustic wave resonator having an IDT electrode portion formed in a dielectric.

4 and 5 are an external view and a cross-sectional view of a transversal type leaky surface acoustic wave filter according to an embodiment of the present invention. Rotation was cut at a cut angle of 16.2 ° with zero thickness Y-cut quartz plate 400 (500), void space 404 (504) is provided, IDT electrodes 402 cycle 2Lp for vibration excitation of the leaky surface acoustic wave (502) Is provided. Reference numeral 403 (503) denotes an IDT electrode that receives the leaked surface acoustic wave. A method of providing the void space 404 (504) is established as a basic technique of the photolithography technique. First, a ZnO thin film or metal thin film having a thickness of 0.1 μm to several μm is deposited on the rotating Y-cut quartz plate 400 (500). Alternatively, a method of coating a photoresist film of several tens of μm can be applied. The surface of the gap forming sacrificial layer film is covered with a dielectric thin film 401 (501). Reference numeral 401 (501) denotes a hard coating dielectric film for spatially securing a void. The dielectric film of the coating is composed of a Pyrex (registered trademark) thin film, a diamond thin film, and β-C ₃ N ₄ nitride. Using a photolithography technique, the lowermost void forming sacrificial layer film is removed by etching, and a pattern is formed so as to ensure a desired leaky surface acoustic wave vibration region. This on the dielectric thin film 401 (501), an aluminum thin film is IDT electrodes for vibration excitation of the leaky surface acoustic wave sputtering, an evaporation method, or the like. When an IDT electrode is formed by photolithography, an IDT electrode maintained mechanically and spatially is formed on the surface of the dielectric thin film 401 (501). By precisely controlling the film forming conditions, the film is relieved of stress and can be basically made into a stable film structure. The leaky surface acoustic wave in this state is not mass loaded. In the three-layer structure of the void forming sacrificial layer film, the hard coating dielectric film, and the aluminum thin film, the lowermost void forming sacrificial layer film may be removed by etching to form a void space. Regarding the excitation efficiency, since the space gap between the IDT electrode and the crystal plate is 0.1 μm to several μm, the IDT electrode is formed on the upper portion of the crystal plate with the dielectric and the gap interposed therebetween. The electric field in the space that contributes to the excitation efficiency of the surface acoustic wave has a feature that it becomes stronger as the electric field in the dielectric is weakened. Even if the position of the IDT electrode is extremely far from the surface of the quartz plate, the excitation intensity of the leaky surface acoustic wave and the received signal are hardly lowered. The surface acoustic wave device having such a structure is the best method for exciting the surface acoustic wave at the IDT electrode disposed through the air gap. As described above, in the present invention, by using an LST cut angle of 16.2 ° with a film thickness of zero, a leaky surface acoustic wave filter is inserted within a temperature range of −30 ° C. to 110 ° C. with a frequency variation of 20 ppm or less. A surface acoustic wave device having a characteristic of a propagation loss of 0.0002 dB / λ or less with a change in loss of 0.4 dB or less can be realized.

6 and 7 are an external view and a sectional view of a transversal type leaky surface acoustic wave filter which is another embodiment of the present invention. The rotation was cut at a cut angle of 16.2 ° with zero thickness Y-cut quartz plate 600 (700), provided void space 604 (704), vibration excitation of the leaky surface acoustic wave in the dielectric 601 (701) An IDT electrode 602 (702) having a period of 2Lp is provided. Reference numeral 603 (703) denotes an IDT electrode that receives the leaked surface acoustic wave. A method of providing the void space 604 (704) is established as a basic technique of the photolithography technique. First, a ZnO thin film or metal thin film having a thickness of 0.1 μm to several μm is deposited on the rotating Y-cut quartz plate 600 (700). Alternatively, a method of coating a photoresist film of several tens of μm can be applied. The surface of the gap forming sacrificial layer film is covered with a dielectric thin film. This dielectric thin film is a hard coating dielectric film for spatially securing voids. The coating film is composed of a Pyrex (registered trademark) thin film, a diamond thin film, and β-C ₃ N ₄ nitride. By using a photolithography technique, the lowermost layer forming sacrificial layer for void formation is removed by etching, and a pattern is formed so as to secure a desired leaky surface acoustic wave vibration region. On the insulating dielectric thin film, an aluminum thin film is IDT electrodes for vibration excitation of the leaky surface acoustic wave sputtering, an evaporation method, or the like. If the IDT electrode is formed by the photolithography technique, the mechanically and spatially maintained IDT electrode is formed on the surface of the dielectric. By depositing a transparent SiO ₂ dielectric on the IDT electrode, the mechanical strength of the IDT electrode can be enhanced. In the leaky surface acoustic wave in this state, the mass load of the IDT electrode does not occur. A four-layer structure consisting of a gap forming sacrificial layer film, a hard coating dielectric film, an aluminum thin film, and a hard coating dielectric film, and forming the surface acoustic wave device by removing the lowermost layer forming the sacrificial layer film by etching. May be. Regarding the excitation efficiency of the leaky surface acoustic wave, since the space gap between the IDT and the quartz plate is 1 μm to several μm, the electric field formed by the IDT electrode is efficiently transferred from the gap space to the quartz plate surface via the dielectric. Works. For the excitation efficiency of the leaky surface acoustic wave, the electric field of void space of the quartz plate surface amount that weakened electric field in the dielectric, the electric field of void space in the epsilon _S times quartz plate is increased. The IDT electrode is covered with a transparent SiO ₂ film. As described above, the present invention uses a LST cut angle of 16.2 ° with a film thickness of zero, and is used as a leaky surface acoustic wave filter with a frequency variation of 20 ppm or less in a temperature range of −30 ° C. to 110 ° C. It is possible to realize one having a characteristic in which a change in loss is 0.4 dB or less and a propagation loss is 0.0002 dB / λ or less.

8 and 9 are an external view and a sectional view of a resonator-type leaky surface acoustic wave resonator according to another embodiment of the present invention. Reflectors 802 and 803 constituting a resonator are provided on the rotated Y-cut quartz plate 800 (900). The reflectors 802 and 803 are formed by performing a groove process with high reflection efficiency by dry etching. In order to further improve the reflection efficiency, the grooved groove may be filled with an aluminum film. However, when an aluminum film is deposited, the influence of mass load appears, so care must be taken. And a void space is provided to the optimum position between the reflectors 802 and 803, providing an IDT electrode 805 (905) for vibration excitation of the leaky surface acoustic wave. A method of providing the void space 804 (904) is established as a basic technique in the photolithography technique. First, a ZnO thin film or metal thin film having a thickness of 0.1 μm to several μm is deposited on a quartz plate. Alternatively, a method of coating a photoresist film of several tens of μm can be applied. The surface of the gap forming sacrificial layer film is covered with a dielectric thin film 801 (901). Reference numeral 801 (901) denotes a hard coating dielectric film for spatially securing voids. The coating film is composed of a Pyrex (registered trademark) thin film, a diamond thin film, and β-C ₃ N ₄ nitride. By using a photolithography technique, the lowermost layer forming sacrificial layer for void formation is removed by etching, and a pattern is formed so as to secure a desired leaky surface acoustic wave vibration region. On the insulating dielectric thin film 801 (901), an aluminum thin film is IDT electrodes for vibration excitation of the leaky surface acoustic wave sputtering, an evaporation method, or the like. If the IDT electrode is formed by the photolithography technique, the IDT electrode maintained in a mechanical space can be formed on the surface of the dielectric thin film 801 (901), and an excellent leakage surface acoustic wave resonator can be realized. By precisely controlling the film forming conditions, the film is relieved of stress and can be basically made into a stable film structure. The leaky surface acoustic wave in this state does not cause a mass load. A three-layer structure of a void forming sacrificial layer film, a hard coating dielectric film, and an aluminum thin film may be used, and the lowermost void forming sacrificial layer film may be removed by etching. A four-layer structure of a sacrificial layer film for void formation, a hard coating dielectric film, an aluminum thin film, and a hard coating dielectric film may be used. As described above, the leaky surface acoustic wave resonator according to the present invention uses an LST cut angle of 16.2 ° in a state where the film thickness is zero, so that the leaky surface acoustic wave resonator has a wide temperature range of −30 ° C. to 110 ° C. Within a range, a high QW SAW resonator with a frequency variation of 20 ppm or less can be realized.

  As described above, the surface acoustic wave device of the present invention is the surface of a rotating Y-cut quartz plate that forms IDT electrodes that are used as excitation electrodes for leaky surface acoustic waves and Rayleigh surface acoustic waves, which was a conventional concept. In order to increase the excitation efficiency and reception efficiency of leaky surface acoustic waves by using IDT electrodes that are spatially floated from the surface, the electric field strength distribution is increased by inserting a dielectric into the gap space between the IDT electrode and the quartz plate surface, and the mass By removing the influence of film thickness without giving load effect to surface acoustic waves, it is possible to obtain the excellent third-order temperature characteristics of the original leaky surface acoustic waves. A number of problems that occur at the interface between the surface and the IDT electrode can be overcome. This method can recover the damage of IDT electrodes under the influence of elastic vibration on the surface even for high-power SAW, so it may open up a new field, and its industrial value is extremely high.

The electric field distribution when the interdigital electrode of the surface acoustic wave device of the present invention is on the surface of the dielectric film is shown. The electric field distribution when the interdigital electrode of the surface acoustic wave device of the present invention is in the dielectric film is shown. The electric field distribution when the interdigital electrode of the surface acoustic wave device of the conventional invention is inside the dielectric film is shown. 1 is an external view of a transversal-type leaky surface acoustic wave filter according to an embodiment of the present invention. It is sectional drawing of the transversal type | mold leakage surface acoustic wave filter of one Example of this invention. It is an external view of the transversal type | mold leakage surface acoustic wave filter of the other Example of this invention. It is sectional drawing of the transversal type | mold leakage surface acoustic wave filter of the other Example of this invention. 1 is an external view of a transversal-type leaky surface acoustic wave resonator according to an embodiment of the present invention. 1 is a cross-sectional view of a transversal-type leaky surface acoustic wave resonator according to an embodiment of the present invention. It is an external view of the transversal type | mold leakage surface acoustic wave filter of the Example of a prior art invention. It is sectional drawing of the transversal type | mold leakage surface acoustic wave filter of the Example of conventional invention.

Explanation of symbols

100 crystal plate 101 insulating film 102 gap 200 crystal plate 201 insulating film 202 gap 300 crystal plate 301 insulating film 302 gap 400 crystal plate 401 insulating film 402 IDT electrode 403 IDT electrode 404 gap 500 crystal plate 501 insulating film 502 IDT electrode 503 IDT electrode 504 Gap 600 Crystal plate 601 Insulating film 602 IDT electrode 603 IDT electrode 604 Gap 700 Crystal plate 701 Insulating film 702 IDT electrode 703 IDT electrode 704 Gap 800 Crystal plate 801 Insulating film 802 Reflective electrode 803 Reflective electrode 804 IDT electrode 805 Gap 900 Crystal plate 901 Insulating film 902 Reflective electrode 903 Reflective electrode 904 IDT electrode 905 Gap 1000 Crystal plate 1001 Insulating film 1002 IDT electrode 1003 IDT electrode 1004 Gap 1100 Crystal plate 1101 Insulating film 1102 IDT electrode 1103 IDT Electrode 11 4 gap

Claims (2)

An interdigitated electrode for transmitting and receiving a leaky surface acoustic wave formed opposite to a rotating Y-cut quartz crystal LST cut substrate cut through a right-handed Euler angle of 15 ° to 17 ° through a gap layer is provided. A pair of reflective electrode structures are formed by providing a transversal surface acoustic wave filter composed of electrodes or a reflector having a groove structure or a metal electrode embedded structure on a rotating Y-cut quartz crystal LST cut substrate. In a resonator-type surface acoustic wave resonator, a laminated space is formed as a void space on the surface of the rotating Y-cut quartz LST cut substrate, a dielectric thereon, and a cross finger electrode for exciting a leaky surface acoustic wave on the dielectric. Surface acoustic wave device characterized by comprising structure 2. The surface acoustic wave device according to claim 1, wherein the interdigital electrodes are formed in a dielectric.