JP2010219706A - Surface acoustic wave element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface acoustic wave element that improves temperature characteristics without thinning a piezoelectric substrate, the element being easily miniaturized. <P>SOLUTION: The surface acoustic wave element 4 includes: (a) a piezoelectric substrate 10 having a pair of main surfaces 10a and 10b, the main surface 10a including a pair of sides 10k facing each other, and having a pair of facing surfaces extended from the pair of sides 10k to the other main surface 10b; (b) an IDT electrode 20 formed on the main surface 10a of the piezoelectric substrate 10 and including an electrode finger 22 extended substantially vertically to the pair of sides 10k; and (c) a pair of constraining part 14 formed on the pair of facing surfaces of the piezoelectric substrate 10 using a material whose linear expansion coefficient is smaller than that of the piezoelectric substrate 10. The constraining parts 14 are formed in parallel with the direction of propagating surface acoustic waves only on both sides of a vibration region where the surface acoustic waves by the IDT electrode 20 are propagated on one main surface 10a of the piezoelectric substrate 10. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a surface acoustic wave element, and more particularly to a technique for improving temperature characteristics of a surface acoustic wave element such as a filter or a resonator that uses a surface acoustic wave on a surface of a piezoelectric substrate.

Conventionally, for example, in a mobile communication system in which a frequency difference between a transmission band and a reception band is small, lithium tantalate (LiTaO ₃ ; LT), lithium niobate (LiNbO ₃ ; LN), etc. are used to secure attenuation in the reception band. A surface acoustic wave filter using a piezoelectric substrate having a large electromechanical coupling coefficient is used. However, since the frequency temperature coefficient (TCF) of the LT substrate or LN substrate is large, the transmission / reception band interval is substantially very small in consideration of manufacturing variations. Therefore, improvement of temperature characteristics is desired.

  Various measures for improving the temperature characteristics have been proposed as follows.

  For example, Patent Document 1 discloses that a fluorinated polyimide resin is applied to the surface of a piezoelectric substrate, and the slope of the temperature characteristic is reduced by the fluorinated polyimide resin to increase the frequency stability.

  Patent Document 2 discloses that a temperature substrate improvement effect is obtained by bonding a support substrate having high temperature characteristics to the back surface of the piezoelectric substrate and restraining the piezoelectric substrate.

In Patent Document 3, as shown in the configuration diagram of FIG. 7, a rectangular protection is provided so as to surround the IDT resonator 2 in a blank area around an IDT (interdigital transducer) resonator 2 on the surface of the LT substrate 1. A film 3 is formed. It is disclosed that the protective film 3 is formed of quartz (SiO ₂ ) having a thermal expansion coefficient smaller than that of the LT substrate 1 and the expansion and contraction of the substrate 1 is restricted by the protective film 3.

JP-A-8-181562 Japanese Patent Laid-Open No. 11-55070 JP 2003-17980 A

  However, the structure of Patent Document 1 is to change the apex temperature of the temperature-frequency characteristic by adding the temperature-frequency characteristic of the resin to the surface acoustic wave element in which the temperature-frequency characteristic has a quadratic curve, Frequency stability can be ensured only in a specific temperature range.

  When the support substrate is bonded to the back surface of the piezoelectric substrate as in Patent Document 2, it is necessary to make the piezoelectric substrate thin in order for the restraint by the support substrate to work effectively. However, there is a problem that the piezoelectric substrate is easily cracked by making it thin.

  In the structure of Patent Document 3, it is necessary to form the protective film 3 so as to surround the IDT type resonator 2, and it is necessary to increase the chip area to form the protective film 3, and it is difficult to reduce the size. is there.

  In view of such circumstances, the present invention is intended to provide a surface acoustic wave element that can improve temperature characteristics without being thinned and can be easily downsized.

  In order to solve the above problems, the present invention provides a surface acoustic wave device configured as follows.

  The surface acoustic wave element has (a) a pair of main surfaces, and outer edges of one of the main surfaces include a pair of opposite sides, and extend from the pair of sides toward the other main surface, respectively. And (b) an IDT electrode including electrode fingers formed on the one main surface of the piezoelectric substrate and extending substantially perpendicular to the pair of sides. And (c) a pair of restraining portions respectively formed on the pair of opposing surfaces of the piezoelectric substrate using a material having a smaller linear expansion coefficient than the piezoelectric substrate. The constraining portion is formed in parallel to the direction in which the surface acoustic wave propagates only on both sides of the vibration region in which the surface acoustic wave due to the IDT electrode propagates on the one main surface of the piezoelectric substrate.

  In the above configuration, the electrode finger of the IDT electrode formed on one main surface of the piezoelectric substrate is slightly inclined from the vertical to the pair of sides of the one main surface of the piezoelectric substrate, that is, substantially vertical. Also good. The pair of restraining portions are formed on the opposing surface of the piezoelectric substrate using a material having a smaller linear expansion coefficient than the piezoelectric substrate, and the surface acoustic wave propagates around the vibration region where the surface acoustic wave is propagated by the IDT electrode. Both sides of the direction substantially perpendicular to the direction extend substantially parallel to the direction in which the surface acoustic wave propagates. For this reason, the expansion and contraction in the direction in which the surface acoustic wave propagates is restricted by the restricting portion on one main surface of the piezoelectric substrate, the change in the state in which the surface acoustic wave propagates is suppressed, and the change in the frequency characteristics becomes small. Therefore, the surface acoustic wave element has improved temperature characteristics.

  According to the above configuration, the constraining portion is formed on the opposing surface formed from the pair of sides of the one main surface of the piezoelectric substrate toward the other main surface, so that the one main surface of the piezoelectric substrate is elastic. Expansion and contraction in the direction in which the surface wave propagates is restrained along one main surface by the restraining portion. Therefore, the effect of improving temperature characteristics can be obtained without reducing the thickness of the piezoelectric substrate.

  In addition, the constraining portions are formed only on both sides in the direction perpendicular to the direction in which the surface acoustic wave propagates, and on both sides in the direction in which the surface acoustic wave propagates, around the vibration region where the surface acoustic waves propagate through the IDT electrode. Not formed. Therefore, the dimension in the direction in which the surface acoustic wave propagates can be made smaller than when the constraining portion is formed so as to surround the entire circumference of the vibration region, and the surface acoustic wave element can be easily downsized.

  Preferably, a support layer formed on the other main surface of the piezoelectric substrate is further provided. The linear expansion coefficient of the support layer is smaller than the linear expansion coefficient of the piezoelectric substrate.

  In this case, the temperature characteristics can be further improved by restraining the expansion and contraction accompanying the temperature change of the piezoelectric substrate by the support layer. In addition, the support layer constrains the expansion and contraction associated with the temperature change of the constraining part and reduces the expansion and contraction associated with the temperature change of the constraining part itself, thereby increasing the constraining force that the constraining part constrains the piezoelectric substrate and further improving temperature characteristics. can do.

  In addition, the direction of the warp caused by the linear expansion coefficient between the constraining portion formed on one main surface side of the piezoelectric substrate and the piezoelectric substrate, and the support layer formed on the other main surface side of the piezoelectric substrate and the piezoelectric substrate Since the direction of the warp caused by the linear expansion coefficient is opposite, the warp due to the temperature change can be offset and the warp can be reduced as a whole.

  Furthermore, by constraining the piezoelectric substrate by the support layer, it is possible to disperse the stress accompanying the temperature change so that the stress is not concentrated at a specific location. As a result, the reliability of the surface acoustic wave device can be improved.

  The surface acoustic wave device of the present invention can improve temperature characteristics without making the piezoelectric substrate thin, and can be easily downsized.

It is sectional drawing which shows the manufacturing process of a surface acoustic wave element. (Example 1) It is sectional drawing which shows the manufacturing process of a surface acoustic wave element. (Example 2) It is sectional drawing which shows the manufacturing process of a surface acoustic wave element. (Example 3) It is a perspective view of a surface acoustic wave element. (Example 1) It is a perspective view of a surface acoustic wave element. (Comparative example) It is a perspective view of a surface acoustic wave element. (Example 2) It is a block diagram of a surface acoustic wave element. (Conventional example)

  Embodiments of the present invention will be described below with reference to FIGS.

  Example 1 A surface acoustic wave element 4 of Example 1 will be described with reference to FIGS. 1, 4, and 5.

  FIG. 4 is a perspective view schematically showing a configuration of the surface acoustic wave element 4 according to the first embodiment. FIG. 1 is a cross-sectional view schematically showing a manufacturing process of the surface acoustic wave element 4 of the first embodiment. 1 corresponds to a cross section taken along line AA in FIG.

  As shown in FIGS. 1C and 4, in the surface acoustic wave element 4, an element pattern including an IDT electrode 20 is formed on the surface 10 a which is one main surface of the piezoelectric substrate 10.

  As shown in FIG. 4, the piezoelectric substrate 10 generally has a pair of rectangular front surface 10a and rear surface 10b, and two pairs of side surfaces 10s and 10t facing each other, and a restraining portion 14 is formed on the front surface 10 side. ing.

  The outer edge of the surface 10a of the piezoelectric substrate 10 includes two pairs of sides 10k and 10m facing each other. As shown in FIG. 1, the piezoelectric substrate 10 has a pair of notches 11 formed along one pair of sides 10k and extends from the pair of sides 10k toward the back surface 10b as the other main surface. An inclined surface 11k that is a facing surface of the head is formed. A constraining portion 14 is formed on the inclined surface 11 k of the notch portion 11 using a material having a smaller linear expansion coefficient than the piezoelectric substrate 10.

  The electrode fingers 22 of the IDT electrode 20 are formed so as to extend perpendicularly to the pair of sides 10k. The surface acoustic wave generated by the IDT electrode 20 propagates in a direction perpendicular to the electrode finger 22 as indicated by an arrow 30 in FIG. The electrode fingers 22 of the IDT electrode 20 may be formed so as to extend with a slight inclination from the vertical with respect to the pair of sides 10k.

  As shown in FIG.1 and FIG.4, the notch part 11 and the restraint part 14 are formed only along a pair of edge | side 10k, and are not formed along the other pair of edge | side 10m. That is, it is formed only on both sides in the direction perpendicular to the direction in which the surface acoustic wave propagates, and on both sides in the direction in which the surface acoustic wave propagates, among the surroundings 11k and 11m of the vibration region where the surface acoustic wave propagates by the IDT electrode 20. Not formed. Therefore, the dimension in the direction in which the surface acoustic wave propagates can be made smaller than when the constraining portion is formed so as to surround the entire circumference of the vibration region, and the surface acoustic wave element can be easily downsized.

  The restraining portion 14 is formed on the inclined surface 11k of the piezoelectric substrate 10 using a material having a smaller linear expansion coefficient than that of the piezoelectric substrate 20, and the surface acoustic wave is generated around the vibration region in which the surface acoustic wave is propagated by the IDT electrode 20. The surface acoustic wave extends in parallel with the direction in which the surface acoustic wave propagates on both sides of the direction perpendicular to the direction of propagation. For this reason, the expansion and contraction of the surface 10a of the piezoelectric substrate 10 in the direction in which the surface acoustic wave propagates is limited by the restricting portion 14, the change in the state in which the surface acoustic wave propagates is suppressed, and the change in the frequency characteristics becomes small. Therefore, the surface acoustic wave element has improved temperature characteristics.

  Since the restraining portion 14 is formed on the slope 11k formed from the pair of sides 10k of the surface 10a of the piezoelectric substrate 10 toward the back surface 10b, the surface 10a of the piezoelectric substrate 10 expands and contracts in the direction in which the surface acoustic wave propagates. Is restrained along the surface 10 a by the restraining portion 14. Therefore, the effect of improving temperature characteristics can be obtained without reducing the thickness of the piezoelectric substrate 10.

  Next, a method for manufacturing the surface acoustic wave element 4 will be described with reference to FIG.

  As shown in FIG. 1A, a conductive pattern including an IDT electrode 20 is formed on the surface 10 a of the wafer-like piezoelectric substrate 10.

  Specifically, a conductive pattern including an IDT electrode 20, a pad (not shown), and a wiring (not shown) connecting the IDT electrode and the pad on the surface 10a of the piezoelectric substrate 10 such as an LT substrate or an LN substrate. Are formed using a photolithography technique or an etching technique. Reflectors may be formed by conductive patterns on both sides in the direction in which the surface acoustic wave due to the IDT electrode 20 propagates.

  Next, as shown in FIG. 1B, a notch 11 is formed in the surface 10a of the piezoelectric substrate. At this time, a side 10k of the front surface 10a of the piezoelectric substrate 10 and a slope 11k extending obliquely from the side 10k toward the back surface 10b are formed.

  Specifically, among the boundary lines of the plurality of surface acoustic wave elements 4, along the boundary line parallel to the direction in which the surface acoustic wave is propagated by the IDT electrode 20, the cross section is V-shaped by dicing or laser processing. A groove is formed. That is, the notch portion 11 is formed on the surface 10a side of the piezoelectric substrate 10 and is processed so that the slope 11k and the surface 10a of the notch portion 11 are trapezoidal.

  Next, as shown in FIG. 1C, after forming the constraining portion 14 on the slope 11k of the notch 11, the piezoelectric substrate 10 is completely cut until it reaches the back surface 10b of the piezoelectric substrate 10, and the surface acoustic wave element is obtained. Four pieces are formed.

Specifically, a mask is arranged on the surface 10a of the piezoelectric substrate 10, the portions other than the notch 11 are covered with the mask, and a piezoelectric material such as an LT substrate or an LN substrate is formed on the inclined surface 11k of the notch 11 by a method such as sputtering or thermal spraying. The constraining portion 14 is formed by depositing a material such as Si, Al ₂ O ₃ , or SiO ₂ having a smaller linear expansion coefficient than that of the substrate 10. At this time, the restraining portion 14 is formed to a height that does not affect the bumps and the like formed on the surface 10a of the piezoelectric substrate 10.

  The surface acoustic wave element 4 constrains the surface 10a of the piezoelectric substrate 10 on which the IDT electrode 20 is formed and the vicinity thereof by a constraining portion 14 formed on the inclined surface 11k, so that the expansion and contraction of the piezoelectric substrate 10 due to a temperature change is achieved. Can be suppressed, and the temperature characteristics can be improved.

  Since the surface 10a of the piezoelectric substrate 10 is constrained by the constraining portion 14 along the surface 10a, the temperature characteristic improvement effect can be achieved without reducing the thickness of the piezoelectric substrate 10, unlike the case of restraining from the back surface 10b side of the piezoelectric substrate 10. Is obtained.

  For example, in Example 1, the notch portion 11 is formed on the piezoelectric substrate 10 of the LT substrate (rotated Y-cut 42 °) in which the dimensions of the front surface 10a and the back surface 10b are 0.80 mm × 0.80 mm and the thickness is 0.25 mm. In the case where the alumina constraining portion 14 is formed in the notch portion 11, the deformation caused by the temperature change from 25 ° C. to 125 ° C. is simulated, and the surface acoustic wave by the center point of the surface 10 a and the IDT electrode 20 propagates. The linear expansion coefficient was calculated from the elongation of the distance between the center point of the surface 10a and the point 0.30 mm away in the direction, and it was 15.3 ppm / ° C. In addition, the dimension of the notch part 11 was taken as the width W shown in FIG. 4 being 0.1 mm, and the depth D being 0.1 mm.

  On the other hand, in the comparative example 1 shown in the perspective view of FIG. 5A, the LT substrate (rotary Y-cut 42) in which the dimensions of the front surface 10p and the back surface are 0.80 mm × 0.80 mm and the thickness is 0.25 mm. In the case of only the piezoelectric substrate 10x, the deformation caused by the temperature change from 25 ° C. to 125 ° C. is simulated, and the center point of the surface 10p and the center point of the surface 10p in the direction in which the surface acoustic wave by the IDT electrode 20 propagates When the linear expansion coefficient was calculated from the elongation between the points 0.30 mm away from the distance, it was 16.3 ppm / ° C.

  Similarly, in Comparative Example 2 shown in the perspective view of FIG. 5B, an LT substrate (rotated Y-cut 42 ° having a surface 10q and a back surface of 0.80 mm × 0.80 mm and a thickness of 0.10 mm). ), The deformation caused by the temperature change from 25 ° C. to 125 ° C. is simulated, and the center point of the surface 10q and the IDT are simulated. The coefficient of linear expansion was calculated from the elongation of the distance between the center point of the surface 10q and a point 0.30 mm away in the direction in which the surface acoustic wave propagated by the electrode 20 was 17.3 ppm / ° C. That is, if the piezoelectric substrate is made thinner than that shown in FIG. 5A and the support layer is provided, the linear expansion coefficient is increased.

  As the linear expansion coefficient of the piezoelectric substrate is smaller, the temperature characteristics are improved. From the simulation results of Example 1, Comparative Example 1 and Comparative Example 2, by forming the restraining portion 14 as in Example 1, It can be seen that the temperature characteristics are improved.

  As described above, the surface acoustic wave element 4 according to the first embodiment is improved in temperature characteristics by providing the pair of restraining portions 14. The effect of improving the temperature characteristics can be obtained without making the piezoelectric substrate 10 thin. Since the constraining portion 14 only needs to be formed in parallel with the direction in which the surface acoustic wave propagated by the IDT electrode 20, the surface acoustic wave element 4 according to the first embodiment forms the constraining portion so as to surround the entire circumference of the vibration region. The size can be reduced as compared with the case of doing so.

  Example 2 A surface acoustic wave element 4 of Example 2 will be described with reference to FIGS. 2 and 6.

  The surface acoustic wave element 4a according to the second embodiment is configured in substantially the same manner as the surface acoustic wave element 4 according to the first embodiment. In the following description, the same reference numerals are used for the same components as those of the surface acoustic wave element 4 of the first embodiment, and differences from the surface acoustic wave element 4 of the first embodiment will be mainly described.

  FIG. 6 is a perspective view schematically showing a configuration of the surface acoustic wave element 4a according to the second embodiment. FIG. 2 is a cross-sectional view schematically showing a manufacturing process of the surface acoustic wave element 4a of the second embodiment. FIG. 2 corresponds to a cross section taken along line BB in FIG.

  As shown in FIGS. 2 and 6, in the surface acoustic wave element 4a, a notch portion 11a formed along a pair of sides 10k of the surface 10a of the piezoelectric substrate 10, and a constraining portion 14a formed in the notch portion 11a, This is different from the surface acoustic wave element 4 according to the first embodiment in that the cross-sectional shape of the surface is rectangular.

  Next, a method for manufacturing the surface acoustic wave element 4a of Example 2 will be described with reference to FIG.

  As shown in FIG. 2A, a conductive pattern including the IDT electrode 20 is formed on the surface 10a of the wafer-like piezoelectric substrate 10 as in the first embodiment.

  Next, as shown in FIG. 2B, a notch 11a is formed in the surface 10a of the piezoelectric substrate. At this time, the notch 11a is formed in a rectangular shape in cross section, from the side 10k of the front surface 10a of the piezoelectric substrate 10, the vertical surface 11s that is a facing surface extending from the side 10k toward the back surface 10b, and the lower end of the vertical surface 13k. A bottom surface 11t extending in parallel with the surface 10a of the piezoelectric substrate 10 is formed.

  Next, as shown in FIG. 2C, as in the first embodiment, after forming the constraining portion 14a in the notch 11a, the constraining portion 14a and the piezoelectric substrate 10 are cut until the back surface 10b of the piezoelectric substrate 10 is reached. Thus, individual pieces of the surface acoustic wave element 4a are formed.

  The constraining portion 14a having a rectangular cross section is formed in parallel with the direction in which the surface acoustic wave propagates by the IDT electrode 20, and restricts expansion and contraction due to a temperature change in the direction in which the surface acoustic wave propagates on the surface 10a of the piezoelectric substrate 10. . Therefore, the surface acoustic wave element 4a according to the second embodiment can improve the temperature characteristics in the same manner as the surface acoustic wave element 4 according to the first embodiment.

  Further, since it is only necessary to form the constraining portion 14a in parallel with the direction in which the surface acoustic wave is propagated by the IDT electrode 20, the surface acoustic wave element 4a is more effective than the case where the constraining portion is formed so as to surround the entire circumference of the vibration region. Can be miniaturized.

  Example 3 A surface acoustic wave element 4b of Example 3 will be described with reference to FIG.

  FIG. 3 is a cross-sectional view schematically showing a method for manufacturing the surface acoustic wave element 4b of the third embodiment. As shown in FIG. 3C, the surface acoustic wave element 4b is configured in substantially the same manner as in the first embodiment.

  That is, the notch portion 13 is formed along a pair of opposite sides 12k of the surface 12a of the piezoelectric substrate 12, and the restraining portion 18 is formed on the inclined surface 13k of the notch portion 13 that is the opposing surface. In the IDT electrode 20, the electrode fingers 22 are formed perpendicular to a pair of sides 12 k facing each other on the surface 12 a of the piezoelectric substrate 12. The constraining portion 18 is formed in parallel with the direction in which the surface acoustic wave propagates along both sides of the vibration region in which the surface acoustic wave propagates through the IDT electrode 20 in a direction perpendicular to the direction in which the surface acoustic wave propagates. .

  However, the point that the support layer 16 is formed on the back surface 12b of the piezoelectric substrate 12 is different from the first embodiment.

  Next, a method for manufacturing the surface acoustic wave element 4b will be described.

As shown in FIG. 3A, a wafer 15 in which a pre-formed support layer 16 and a piezoelectric substrate 12 are bonded together is prepared, and a conductive pattern including an IDT electrode 20 is formed on the surface 10a of the piezoelectric substrate 10. . Alternatively, after forming a conductive pattern such as the IDT electrode 20 on the front surface 12a of the piezoelectric substrate 12, the support layer 16 may be formed on the back surface 12b of the piezoelectric substrate 12 by thermal spraying. As the piezoelectric substrate 10, an LT substrate, an LN substrate, or the like is used, and the support layer 16 is formed using a material having a smaller linear expansion coefficient than the piezoelectric substrate 10, such as Si, Al ₂ O ₃ , or SiO ₂ .

  Next, as shown in FIG. 3B, a notch 13 is formed in the surface 12 a of the piezoelectric substrate 12. For example, by forming a groove having a V-shaped cross section by dicing or laser processing along a boundary line parallel to the direction in which the surface acoustic wave propagates among the boundary lines of a plurality of surface acoustic wave elements, piezoelectric A slope 13k of the notch 13 is formed on the substrate 10. The inclined surface 13k may reach the back surface 12b of the piezoelectric substrate 12.

  Next, as shown in FIG. 3C, after the constraining portion 18 is formed in the notch portion 13, the constraining portion 18, the piezoelectric substrate 12 and the support layer 16 are cut to form individual pieces of the surface acoustic wave element 4b. To do.

  The surface acoustic wave element 4b according to the third embodiment has a higher temperature characteristic improving effect by using the restraint of the back surface 12b of the piezoelectric substrate 12 by the support layer 16 and the restraint of the surface 12a of the piezoelectric substrate 12 by the restraining portion 18 in combination. can get.

  In addition, the restraint portion 18 and the support layer 16 are brought close to each other or coupled to restrain the restraint portion 18 from expanding and contracting, and the restraint portion 18 itself can be restrained from expanding and contracting due to a temperature change. The effect of improving the temperature characteristics, which increases the restraining force of the portion 18 restraining the piezoelectric substrate 12, can be further enhanced.

  In addition, the direction of warping caused by the linear expansion coefficient between the restraining portion 18 formed on the front surface 12 a side of the piezoelectric substrate 12 and the piezoelectric substrate 12, the support layer 16 formed on the back surface 12 b side of the piezoelectric substrate 12, and the piezoelectric substrate 12. Therefore, the warp caused by the linear expansion coefficient is reversed, so that the warp due to the temperature change can be offset and the warp can be reduced as a whole.

  In addition, the stress accompanying the temperature change can be dispersed between the bumps on the front surface 12a of the piezoelectric substrate 12 and the back surface 12b of the piezoelectric substrate 12, and the stress can be prevented from concentrating at a specific location. As a result, the reliability of the surface acoustic wave device can be improved.

  <Summary> As described above, when the restraining portions 14 and 18 are provided in parallel with the direction in which the surface acoustic wave propagates, the temperature characteristics can be improved without making the piezoelectric substrates 10 and 12 thin, and the miniaturization is easy. It is.

  The present invention is not limited to the above embodiment, and can be implemented with various modifications.

4, 4a, 4b Surface acoustic wave element 10 Piezoelectric substrate 10a Surface (one main surface)
10b Back surface (the other main surface)
10k, 10m A pair of sides 11, 11a Notch 11k Slope (opposite surface)
11s Vertical surface (opposite surface)
11t bottom surface 12 piezoelectric substrate 12a surface (one main surface)
12b Back surface (the other main surface)
13 Notch 13k Slope (opposite surface)
14, 14a Constraint portion 16 Support layer 18 Constraint portion

Claims (2)

The outer edge of one of the main surfaces includes a pair of opposing sides, and a pair of opposing surfaces extending from the pair of sides toward the other main surface is formed. A piezoelectric substrate;
An IDT electrode including electrode fingers formed on the one main surface of the piezoelectric substrate and extending substantially perpendicular to the pair of sides;
A pair of constraining portions formed on the pair of opposing surfaces of the piezoelectric substrate using a material having a smaller linear expansion coefficient than the piezoelectric substrate;
With
The constraining portion is formed only on both sides of a vibration region in which the surface acoustic wave due to the IDT electrode propagates on the one main surface of the piezoelectric substrate, in parallel with the direction in which the surface acoustic wave propagates. A surface acoustic wave device. A support layer formed on the other principal surface of the piezoelectric substrate;
The surface acoustic wave device according to claim 1, wherein a linear expansion coefficient of the support layer is smaller than a linear expansion coefficient of the piezoelectric substrate.

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