Elastic wave device, and communication device

Abstract

The present invention improves the strength of a piezoelectric body. This elastic wave device comprises: a support substrate that has a recess; a piezoelectric body that overlaps the recess in plan view; and an excitation electrode that is positioned on a surface of the piezoelectric body. When a bonded region is defined as a region of the piezoelectric body that is bonded to the support substrate, and a non-bonded region is defined as a region of the piezoelectric body that is not bonded to the support substrate, the piezoelectric body is thicker in the non-bonded region than in the bonded region.

Description

Acoustic wave device and communication device

[0001] The present disclosure relates to an acoustic wave device and a communication device including the acoustic wave device.

[0002] Patent Document 1 discloses an example of the configuration of an acoustic wave device having a cavity.

[0003] WO2016 / 098526

[0004] In order to solve the above problem, an elastic wave device according to one aspect of the present disclosure comprises a support substrate having a recess on a first surface, a piezoelectric body having a second surface bonded to the first surface and overlapping the recess in a planar view, the piezoelectric body having a thickness of 3 μm or less, and an excitation electrode located on the surface of the piezoelectric body and overlapping the recess in a perspective view perpendicular to the first surface, wherein when a region of the piezoelectric body bonded to the support substrate is defined as a bonding region and a region of the piezoelectric body not bonded to the support substrate is defined as a non-bonding region, the piezoelectric body is thicker in the non-bonding region than in the bonding region.

[0005] 1 is a cross-sectional view illustrating the configuration of an elastic wave device according to a first embodiment; FIG. 2 is a plan view illustrating the configuration of an elastic wave device according to the first embodiment; FIG. 3 is a cross-sectional view illustrating the configuration of an elastic wave device according to a modified example of the first embodiment; FIG. 4 is a cross-sectional view illustrating the configuration of an elastic wave device according to a second embodiment; FIG. 5 is a cross-sectional view illustrating the configuration of an elastic wave device according to a third embodiment; and FIG. 6 is a diagram illustrating a schematic configuration of a communication device according to a fourth embodiment.

[0006] [Embodiment 1] An elastic wave device according to embodiment 1 will be described below. For ease of explanation, components having the same functions as those described in embodiment 1 will be denoted by the same reference numerals in the following embodiments, and their description will not be repeated. For simplicity, descriptions of well-known technical matters will also be omitted as appropriate. Unless otherwise specified, the components, materials, and numerical values ​​described in this specification are merely examples. Therefore, for example, unless otherwise specified, the positional relationship of each component is not limited to the example shown in each figure. Furthermore, the illustrations of each component are not necessarily to scale.

[0007] 1 is a cross-sectional view illustrating the configuration of an elastic wave device 1 according to embodiment 1. As shown in FIG. 1 , the elastic wave device 1 includes a support substrate 10, a piezoelectric body 20, and an excitation electrode 30.

[0008] The support substrate 10 supports other components included in the elastic wave device 1. The support substrate 10 has a first surface 11. The support substrate 10 has a recess 11a on the first surface 11. The portion of the first surface 11 other than the recess 11a is a support portion 12 to which the piezoelectric body 20 is bonded and supported. The depth of the recess 11a may be 0.1 μm or more and 100 μm or less. The recess 11a may penetrate to the back surface opposite the first surface 11, and may not have a bottom surface. If the recess 11a penetrates to the back surface, it will have the same depth as the support substrate 10.

[0009] FIG. 2 is a plan view illustrating an example of the configuration of the elastic wave device 1. In FIG. 2, reference numerals 201 and 202 indicate different examples of the configuration of the elastic wave device 1. In either example, the elastic wave device 1 may include a plurality of excitation electrodes 30 and two bus bars 35a, 35b to which the excitation electrodes 30 are connected. The excitation electrodes 30 will be described later. The support portion 12 has a frame-like shape in a plan view.

[0010] In the example indicated by reference numeral 201, the entire excitation electrode 30 overlaps with the recess 11a in a plan view. In the example indicated by reference numeral 201, the excitation electrode 30 has electrode fingers 31 and dummy electrode fingers 32. The electrode fingers 31 are connected to either the bus bar 35a or the bus bar 35b, and are located in intersection regions where the electrode fingers 31 intersect with the electrode fingers 31 connected to the bus bar 35a or the bus bar 35b to which the electrode fingers 31 are not connected. The dummy electrode fingers 32 are connected to either the bus bar 35a or the bus bar 35b, are shorter than the electrode fingers 31, and are not located in the intersection regions. The excitation electrode 30 does not necessarily have to have dummy electrode fingers 32.

[0011] In the example indicated by the reference numeral 202, the intersection region of the electrode fingers 31 of the excitation electrode 30 overlaps with the recess 11a in a plan view. The edge of the recess 11a, i.e., the boundary line between the region where the support substrate 10 supports the piezoelectric body 20 and the region where it does not support the piezoelectric body 20, is located in the gap portion of the excitation electrode 30. The gap portion is the region between the tip of the electrode finger 31 and the bus bars 35a, 35b facing the tip. The excitation electrode 30 may or may not have dummy electrode fingers 32. When the excitation electrode 30 has dummy electrode fingers 32, the gap portion is the region between the tip of the electrode finger 31 and the tip of the dummy electrode finger 32 facing the tip of the electrode finger 31.

[0012] The material of the support substrate 10 may be, for example, silicon (Si) or another material. The support substrate 10 may be integrally formed from a single material, or may be formed by combining multiple materials. When the support substrate 10 is integrally formed from a single material, the support substrate 10 having the recess 11a may be formed, for example, by etching the surface of a flat, plate-shaped substrate. When the support substrate 10 is formed from a combination of multiple materials, the support substrate 10 may be formed, for example, by arranging the support portion 12 on a flat, plate-shaped substrate. In this case, the region of the support substrate 10 where the support portion 12 is not arranged becomes the recess 11a.

[0013] The piezoelectric body 20 is a substantially flat member having a second surface 22 bonded to the first surface 11 of the support substrate 10. Specifically, the second surface 22 may be bonded to the support portion 12 of the first surface 11. Therefore, the piezoelectric body 20 overlaps the recess 11a in a planar view. Here, the planar view refers to a planar view from a direction perpendicular to the first surface 11. In other words, the piezoelectric body 20 covers the recess 11a with a space 13 therebetween. That is, the acoustic wave device 1 has a cavity. The material of the piezoelectric body 20 may be, for example, lithium tantalate (LT) or lithium niobate (LN). The thickness of the piezoelectric body 20 may be 3 μm or less. Alternatively, the thickness of the piezoelectric body 20 may be 1 μm or less.

[0014] The piezoelectric body 20 has a bonded region 211 and a non-bonded region 212. The bonded region 211 is defined as a region where the piezoelectric body 20 is bonded to the support substrate 10. The non-bonded region 212 is defined as a region where the piezoelectric body 20 is not bonded to the support substrate 10. For example, the bonded region 211 may be located at the outer edge of the piezoelectric body 20, and the non-bonded region 212 may be located inside the bonded region 211. In other words, the non-bonded region 212 may be surrounded by the bonded region 211. However, the positional relationship between the bonded region 211 and the non-bonded region 212 is not limited to this.

[0015] The excitation electrode 30 is an electrode that excites an elastic wave in the piezoelectric body 20. The excitation electrode 30 may be, for example, an IDT (Inter-Digital Transducer) electrode. In FIG. 1 , the excitation electrode 30 extends in a direction perpendicular to the paper surface. For example, when an alternating current is applied to such an excitation electrode 30, an elastic wave is excited in the piezoelectric body 20.

[0016] The excitation electrode 30 may be located on the surface of the piezoelectric body 20. In the example shown in Fig. 1, the piezoelectric body 20 further has a third surface 23 located on the opposite side to the second surface 22. The excitation electrode 30 is located on the third surface 23. However, the excitation electrode 30 may also be located on the second surface 22. The excitation electrode 30 is also located in the non-bonding region 212. That is, the excitation electrode 30 overlaps the recess 11a when viewed from a direction perpendicular to the first surface 11.

[0017] 1 , both the second surface 22 and the third surface 23 are flat in the non-bonding region 212. However, both the second surface 22 and the third surface 23 may be curved with the same curvature in the non-bonding region 212. That is, the piezoelectric body 20 may have a constant thickness in the non-bonding region 212 and may have a shape that is bent toward the second surface 22 or the third surface 23.

[0018] The piezoelectric body 20 is thicker in the non-bonded region 212 than in the bonded region 211. This improves the strength of the piezoelectric body 20, particularly the non-bonded region 212 excited by the excitation electrode 30, in the acoustic wave device 1 having a cavity. Specifically, the thickness of the piezoelectric body 20 in the non-bonded region 212 may be in a range of 1.01 to 2 times the thickness of the piezoelectric body 20 in the bonded region 211. Alternatively, the thickness of the piezoelectric body 20 in the non-bonded region 212 may be in a range of 1.1 to 1.4 times the thickness of the piezoelectric body 20 in the bonded region 211.

[0019] The non-bonding region 212 may include an electrode region 241 where the excitation electrode 30 is located. The thickness of the piezoelectric body 20 may be constant in the electrode region 241. This makes it easier for the elastic waves excited by the piezoelectric body 20 and the excitation electrode 30 to be reflected in a constant direction. Furthermore, the shape of the piezoelectric body 20 becomes simple, making it easier to manufacture the piezoelectric body 20.

[0020] 1 , the entire non-bonded region 212 is the electrode region 241. Therefore, the thickness of the piezoelectric body 20 may be constant throughout the entire non-bonded region 212. This further simplifies the shape of the piezoelectric body 20, and further simplifies the manufacturing process of the piezoelectric body 20, such as the bonding process.

[0021] 1 , both the second surface 22 and the third surface 23 are flat in the non-bonding region 212. However, both the second surface 22 and the third surface 23 may be curved with the same curvature in the non-bonding region 212. That is, the piezoelectric body 20 may have a constant thickness in the non-bonding region 212 and may have a shape that is bent toward the second surface 22 or the third surface 23.

[0022] 1 , the second surface 22 in the non-bonding region 212 is located closer to the support substrate 10 than the second surface 22 in the bonding region 211, so that the piezoelectric body 20 is thicker in the non-bonding region 212 than in the bonding region 211. Therefore, the distance between the piezoelectric body 20 and the support substrate 10 in the non-bonding region 212 is smaller than when the thickness of the non-bonding region 212 is equal to the thickness of the bonding region 211. Furthermore, at the boundary between the bonding region 211 and the non-bonding region 212, the side of the non-bonding region 212 is in contact with the support portion 12. As a result, heat generated in the excitation electrode 30 is more easily dissipated to the support substrate 10 than when the thickness of the non-bonding region 212 is equal to the thickness of the bonding region 211.

[0023] The second surface 22 in the non-bonding region 212 does not have to be located closer to the support substrate 10 than the second surface 22 in the bonding region 211. For example, the second surfaces 22 in the bonding region 211 and the non-bonding region 212 may be formed flush with each other. In this case, the third surface 23 in the non-bonding region 212 may be farther away from the support substrate 10 than the third surface 23 in the bonding region 211. Alternatively, the second surface 22 in the non-bonding region 212 may be located closer to the support substrate 10 than the second surface 22 in the bonding region 211, and the third surface 23 in the non-bonding region 212 may be farther away from the support substrate 10 than the third surface 23 in the bonding region 211. Even when the piezoelectric body 20 has such a shape, the strength of the non-bonding region 212 is improved compared to when the thickness of the non-bonding region 212 is equal to the thickness of the bonding region 211.

[0024] The distance between adjacent excitation electrodes 30 is defined as pitch PT, and the ratio of the width of excitation electrode 30 to pitch PT is defined as duty D. In this case, D may be less than 0.3 in elastic wave device 1. Furthermore, the thickness of the thickest portion of piezoelectric body 20 in electrode region 241 is defined as thickest-portion thickness T. In this case, T / (PT×D) may be less than 0.3 in elastic wave device 1.

[0025] Specifically, the pitch PT may be 3 μm or more and 5 μm or less, for example, 4 μm. The duty D may be 0.2 or more and less than 0.3. The thickness T of the thickest part of the piezoelectric body 20 may be 3 μm or less or 1 μm or less, as described above, for example, 0.4 μm.

[0026] When the pitch PT, duty D, and thickness T of the thickest part satisfy the above conditions, the elastic wave excited by the excitation electrode 30 may be a bulk wave. The bulk wave may be, for example, a thickness-shear mode wave. In this case, the elastic wave propagates in the thickness direction of the piezoelectric body 20. In addition, in this case, the resonant frequency of the elastic wave depends on the thickness of the piezoelectric body 20.

[0027] The pitch PT, duty D, and thickness T of the thickest portion do not necessarily have to satisfy the above conditions. If the pitch PT, duty D, and thickness T of the thickest portion do not satisfy the above conditions, the elastic wave excited by the excitation electrode 30 may be a plate wave. The plate wave may be, for example, an A1 mode Lamb wave. In this case, the elastic wave propagates in the thickness direction of the piezoelectric body and in the arrangement direction of the excitation electrodes 30. Furthermore, in this case, the resonant frequency of the elastic wave depends on the thickness of the piezoelectric body 20 and the pitch PT of the excitation electrodes.

[0028] The excitation electrode 30 is not limited to an IDT electrode. Furthermore, the material of the piezoelectric body 20 is not limited to LT or LN. When the excitation electrode 30 is not an IDT electrode and the material of the piezoelectric body 20 is not LT or LN, the acoustic wave excited by the excitation electrode 30 is not limited to a bulk wave or a plate wave.

[0029] The thermal conductivity of the material of the support substrate 10 may be higher than the thermal conductivity of the material of the piezoelectric body 20. When the material of the piezoelectric body 20 is LT or LN, silicon, which is mentioned above as an example of a material for the support substrate 10, satisfies this condition. This allows heat generated in the excitation electrode 30 to be efficiently dissipated to the outside of the acoustic wave device 1 via the piezoelectric body 20 and the support substrate 10. However, the support substrate 10 may be formed of another material that has a thermal conductivity higher than that of the material of the piezoelectric body 20.

[0030] (Manufacturing Method) An example of a manufacturing method for the elastic wave device 1 is shown below. For example, a sacrificial layer may be formed in the recess 11a of the support substrate 10, and the piezoelectric body 20 may be formed on the support portion 12 and the sacrificial layer. The sacrificial layer is then removed by etching to manufacture the elastic wave device 1 in which the piezoelectric body 20 overlaps the recess 11a in a planar view. Alternatively, the piezoelectric body 20, which is separately manufactured, may be bonded to the support portion 12 of the support substrate 10 by ultrasonic bonding or the like.

[0031] 3 is a cross-sectional view illustrating the configuration of an elastic wave device 1A according to a modification of Embodiment 1. The elastic wave device 1A differs from the elastic wave device 1 in that it includes a piezoelectric body 20A instead of the piezoelectric body 20 and an excitation electrode 30A instead of the excitation electrode 30. For simplicity, FIG. 3 illustrates the piezoelectric body 20A as if it has the same thickness in the bonded region 211 and the same thickness in the non-bonded region 212. However, the actual piezoelectric body 20A may have a shape in which the non-bonded region 212 is thicker than the bonded region 211, similar to the piezoelectric body 20 in the elastic wave device 1.

[0032] The piezoelectric body 20A may be formed of, for example, AlN or ScAlN. The excitation electrode 30A may be a plate-shaped electrode that is disposed along each of the second surface 22 and the third surface 23 of the piezoelectric body 20A. In this type of elastic wave device 1A, the strength of the piezoelectric body 20A is improved by the piezoelectric body 20A having the above-described shape.

[0033] 4 is a cross-sectional view illustrating the configuration of an elastic wave device 2 according to a second embodiment. As shown in FIG. 4 , the elastic wave device 2 differs from the elastic wave device 1 in that it includes a piezoelectric body 40 instead of the piezoelectric body 20. The piezoelectric body 40 differs from the piezoelectric body 20 in that it includes a second surface 42 instead of the second surface 22. The second surface 42 is curved in the non-bonding region 212 such that the distance from the third surface 23 decreases as the second surface 42 approaches the bonding region 211. In other words, the second surface 42 is curved in the non-bonding region 212 such that the second surface 42 moves away from the support substrate 10 as the second surface 42 approaches the bonding region 211.

[0034] In the elastic wave device 2, the excitation electrode 30 is also located on the third surface 23. The third surface 23 may be closer to flatness than the second surface 42. That is, in the elastic wave device 2, the curvature of the third surface 23 may be smaller than the curvature of the second surface 42. In the example shown in FIG. 4 , the third surface 23 is flat and the second surface 42 is curved. Alternatively, the third surface 23 may be curved and the second surface 42 may be curved with a larger curvature than the third surface 23. This makes the third surface 23 relatively flat, which makes it easier to form the excitation electrode 30 on the third surface 23 with high precision.

[0035] Furthermore, when an elastic wave device is applied to a frequency filter, the frequency characteristics become steeper as the difference between the resonant frequency and anti-resonant frequency of the elastic waves excited in the piezoelectric body becomes smaller. In elastic wave device 2, the portion of non-bonded region 212 of piezoelectric body 40 that is close to bonded region 211 is thinner than other portions. By having a thin portion in non-bonded region 212 of piezoelectric body 40, the difference between the resonant frequency and anti-resonant frequency of the elastic waves excited in piezoelectric body 40 becomes smaller. Therefore, when elastic wave device 2 is applied to a frequency filter, the attenuation characteristics of the frequency filter can be made steeper.

[0036] 5 is a cross-sectional view illustrating the configuration of an elastic wave device 3 according to embodiment 3. As shown in FIG. 5 , elastic wave device 3 differs from elastic wave device 1 in that it includes a piezoelectric body 50 instead of piezoelectric body 20. Piezoelectric body 50 differs from piezoelectric body 20 in that it includes a second surface 52 instead of second surface 22.

[0037] In the piezoelectric body 50, the non-bonding region 212 does not have to coincide with the electrode region 241. Specifically, the non-bonding region 212 may further have a step region 242 located between the electrode region 241 and the bonding region 211. In this case, the thickness of the piezoelectric body 50 may be constant in the electrode region 241. Furthermore, the height of the second surface 52 relative to the bottom surface of the recess 11a may be different between the bonding region 211 and the electrode region 241.

[0038] 5 , the second surface 52 in the step region 242 may be an inclined surface that slopes from the edge of the bonding region 211 toward the edge of the electrode region 241. In the example shown in FIG. 5 , the inclination of the second surface 52 in the step region 242 is constant regardless of the distance from the extension of the bonding region 211. However, the second surface 52 in the step region 242 may change depending on the distance from the extension of the bonding region 211. Furthermore, the second surface 52 in the electrode region 241 may be flat. In an elastic wave device 3 including a piezoelectric body 50 having such a shape, the strength of the piezoelectric body 50 is also improved.

[0039] Fourth Embodiment FIG. 6 illustrates a schematic configuration of a communication device 151 according to a fourth embodiment. The communication device 151 is an application example of an elastic wave device according to an aspect of the present disclosure and performs wireless communication using radio waves. The communication device 151 may include one duplexer 101 as a transmit filter 109 and another duplexer 101 as a receive filter 111. Each of the two duplexers 101 may include an elastic wave device according to an aspect of the present disclosure (e.g., elastic wave devices 1, 1A, 2, and 3). In this manner, the communication device 151 may include an elastic wave device according to an aspect of the present disclosure.

[0040] In the communication device 151, a transmission information signal TIS containing information to be transmitted may be modulated and frequency-raised (converted into a high-frequency signal having a carrier frequency) by an RF-IC (Radio Frequency-Integrated Circuit) 153, and converted into a transmission signal TS. A band-pass filter 155 may remove unnecessary components from the TS outside the transmission passband. Next, the TS after removing the unnecessary components may be amplified by an amplifier 157 and input to the transmission filter 109.

[0041] The transmission filter 109 may remove unnecessary components outside the transmission passband from the input transmission signal TS. The transmission filter 109 may output the TS after removing the unnecessary components to the antenna 159. The antenna 159 may convert the TS, which is an electrical signal input thereto, into radio waves as a wireless signal and transmit the radio waves to the outside of the communication device 151.

[0042] Furthermore, the antenna 159 may convert the received external radio waves into a received signal RS, which is an electrical signal, and input the RS to the receiving filter 111 via the antenna terminal. The receiving filter 111 may remove unnecessary components outside the receiving passband from the input RS. The receiving filter 111 may output the received signal RS after the unnecessary components have been removed to the amplifier 161. The output RS may be amplified by the amplifier 161. The bandpass filter 163 may remove unnecessary components outside the receiving passband from the amplified RS. The RS after the unnecessary components have been removed may be frequency-downgraded and demodulated by the RF-IC 153, and converted into a received information signal RIS.

[0043] The TIS and RIS may be low-frequency signals (baseband signals) containing appropriate information. For example, the TIS and RIS may be analog audio signals or digitized audio signals. The passband of the wireless signals may be set appropriately and may comply with various known standards.

[0044] [Summary] An elastic wave device according to aspect 1 of the present disclosure comprises a support substrate having a recess on a first surface, a piezoelectric body having a second surface bonded to the first surface and overlapping the recess in a planar view, the piezoelectric body having a thickness of 3 μm or less, and an excitation electrode located on the surface of the piezoelectric body and overlapping the recess in a perspective view perpendicular to the first surface, wherein when a region of the piezoelectric body bonded to the support substrate is defined as a bonding region and a region of the piezoelectric body not bonded to the support substrate is defined as a non-bonding region, the piezoelectric body is thicker in the non-bonding region than in the bonding region.

[0045] According to a second aspect of the present disclosure, in the elastic wave device of the first aspect, the thermal conductivity of the material of the support substrate is higher than the thermal conductivity of the material of the piezoelectric body.

[0046] An elastic wave device according to aspect 3 of the present disclosure is, in aspect 1 or 2, such that the piezoelectric body has a third surface located opposite the second surface, the excitation electrode is located on the third surface, the second surface is curved in the non-bonded region so that the distance to the third surface decreases as it approaches the bonded region, and the curvature of the third surface is smaller than the curvature of the second surface.

[0047] An elastic wave device according to aspect 4 of the present disclosure is any one of aspects 1 to 3, wherein the non-bonding region includes an electrode region in which the excitation electrode is located, and the thickness of the piezoelectric body is constant in the electrode region.

[0048] An elastic wave device according to a fifth aspect of the present disclosure is the same as the fourth aspect, wherein the thickness of the piezoelectric body is constant throughout the non-bonded region.

[0049] An elastic wave device according to aspect 6 of the present disclosure is, in aspect 4, such that the height of the second surface relative to the bottom surface of the recess is different between the bonding region and the electrode region, and the non-bonding region further has a step region located between the bonding region and the electrode region.

[0050] According to a seventh aspect of the present disclosure, in the elastic wave device of the sixth aspect, the second surface in the step region is an inclined surface that is inclined from the edge of the bonding region toward the edge of the electrode region.

[0051] In the elastic wave device according to aspect 8 of the present disclosure, in any one of aspects 1 to 7, when the spacing between the excitation electrodes is defined as the pitch and the ratio of the width of the excitation electrodes to the pitch is defined as the duty, the duty is less than 0.3.

[0052] In the elastic wave device according to aspect 9 of the present disclosure, in any one of aspects 1 to 8, when the spacing between the excitation electrodes is defined as the pitch, the ratio of the thickness of the thickest part of the piezoelectric body to the pitch is less than 0.3.

[0053] An elastic wave device according to a tenth aspect of the present disclosure is the elastic wave device of any one of the first to ninth aspects, wherein the excitation electrode is an IDT (Inter-Digital Transducer) electrode and excites a bulk wave or a plate wave.

[0054] A communication device according to an eleventh aspect of the present disclosure includes the acoustic wave device according to any one of the first to tenth aspects.

[0055] [Additional Notes] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure.

[0056] REFERENCE SIGNS LIST 1, 1A, 2, 3 Acoustic wave device 10 Support substrate 11 First surface 11a Recess 12 Support portion 20, 20A, 40, 50 Piezoelectric body 211 Bonded region 212 Non-bonded region 22, 42, 52 Second surface 23 Third surface 241 Electrode region 242 Step region 30, 30A Excitation electrode 151 Communication device

Claims

1. An elastic wave device comprising: a support substrate having a recess on a first surface; a piezoelectric body having a second surface bonded to the first surface and overlapping with the recess in a planar view and having a thickness of 3 μm or less; and an excitation electrode located on the surface of the piezoelectric body and overlapping with the recess when viewed from a direction perpendicular to the first surface, wherein when a region of the piezoelectric body bonded to the support substrate is defined as a bonding region and a region of the piezoelectric body not bonded to the support substrate is defined as a non-bonding region, the piezoelectric body is thicker in the non-bonding region than in the bonding region.

2. The acoustic wave device according to claim 1, wherein the material of the support substrate has a higher thermal conductivity than the material of the piezoelectric body.

3. The elastic wave device of claim 1 or 2, wherein the piezoelectric body has a third surface located opposite the second surface, the excitation electrode is located on the third surface, the second surface is curved in the non-bonded region such that the distance to the third surface decreases as the second surface approaches the bonded region, and the curvature of the third surface is smaller than the curvature of the second surface.

4. An elastic wave device according to any one of claims 1 to 3, wherein the non-bonded region includes an electrode region in which the excitation electrode is located, and the thickness of the piezoelectric body is constant in the electrode region.

5. The elastic wave device according to claim 4, wherein the thickness of the piezoelectric body is constant throughout the non-bonded region.

6. The elastic wave device according to claim 4, wherein a height of the second surface relative to a bottom surface of the recess differs between the bonding region and the electrode region, and the non-bonding region further has a step region located between the bonding region and the electrode region.

7. The acoustic wave device according to claim 6, wherein the second surface in the step region is an inclined surface that is inclined from the edge of the bonding region toward the edge of the electrode region.

8. An elastic wave device according to any one of claims 1 to 7, wherein when the spacing between the excitation electrodes is defined as a pitch and the ratio of the width of the excitation electrodes to the pitch is defined as a duty, the duty is less than 0.

3.

9. An elastic wave device according to any one of claims 1 to 8, wherein, when the spacing between the excitation electrodes is defined as a pitch, the ratio of the thickness of the thickest part of the piezoelectric body to the pitch is less than 0.

3.

10. The acoustic wave device according to claim 1, wherein the excitation electrode is an IDT (Inter-Digital Transducer) electrode and excites a bulk wave or a plate wave.

11. A communication device comprising the acoustic wave device according to any one of claims 1 to 10.

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