Elastic wave device

Abstract

An elastic wave device (1) comprises: a support substrate (33); a piezoelectric layer (31) having main surfaces (31a and 31b) facing each other; an IDT electrode (10) disposed on the main surface (31a); a wiring electrode (40a) disposed on the main surface (31a) and connected to the IDT electrode (10); and an intermediate layer (32) disposed between the support substrate (33) and the main surface (31b). The main surface (31b) includes, when the main surfaces (31a and 31b) are viewed in plan, a region R1 that overlaps the IDT electrode (10) and a region R2 that overlaps the wiring electrode (40a). The thickness T32E of the intermediate layer (32) in the region R2 is smaller than the thickness T32C of the intermediate layer (32) in the region R1, and the total thickness T30E of the intermediate layer (32) and the piezoelectric layer (31) in the region R2 is smaller than the total thickness T30C of the intermediate layer (32) and the piezoelectric layer (31) in the region R1.

Description

Elastic Wave Device

[0001] The present invention relates to an acoustic wave device.

[0002] Patent Document 1 discloses an acoustic wave device having a structure in which a support member, an acoustic reflection layer, a piezoelectric layer, an IDT electrode, and a wiring electrode are stacked in this order. The acoustic reflection layer, which is composed of a low-Z dielectric layer, a metal layer, and a high-Z dielectric layer, is said to be able to eliminate unnecessary capacitance components and reduce acoustic wave propagation loss.

[0003] International Publication No. 2018 / 235731

[0004] With the demand for higher output power in mobile communications, there is a demand for acoustic wave devices with improved heat dissipation properties.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an acoustic wave device with improved heat dissipation properties.

[0006] In order to achieve the above-mentioned object, an elastic wave device according to one aspect of the present invention comprises a support substrate, a piezoelectric layer having first and second main surfaces facing each other, a first IDT electrode arranged on the first main surface, a first wiring electrode arranged on the first main surface and connected to the first IDT electrode, and an intermediate layer arranged between the support substrate and the second main surface, wherein the second main surface includes a first region overlapping with the first IDT electrode and a second region overlapping with the first wiring electrode when the first and second main surfaces are viewed in a plane, the thickness of the intermediate layer in the second region being smaller than the thickness of the intermediate layer in the first region, and the total thickness of the intermediate layer and the piezoelectric layer in the second region being smaller than the total thickness of the intermediate layer and the piezoelectric layer in the first region.

[0007] According to the present invention, it is possible to provide an acoustic wave device with improved heat dissipation properties.

[0008] FIG. 1A is a plan view of an elastic wave device according to an embodiment. FIG. 1B is a cross-sectional view of an elastic wave device according to an embodiment. FIG. 2A is a plan view of an elastic wave device according to a comparative example. FIG. 2B is a cross-sectional view of an elastic wave device according to the comparative example. FIG. 3A is a plan view of an elastic wave device according to a first modification of an embodiment. FIG. 3B is a cross-sectional view of an elastic wave device according to the first modification of an embodiment. FIG. 4A is a plan view of an elastic wave device according to a second modification of an embodiment. FIG. 4B is a first cross-sectional view of an elastic wave device according to the second modification of an embodiment. FIG. 4C is a second cross-sectional view of an elastic wave device according to a third modification of an embodiment.

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component arrangements, and connection configurations shown in the following embodiments are merely examples and are not intended to limit the present invention. Among the components in the following embodiments, components that are not recited in independent claims will be described as optional components. Furthermore, the sizes or size ratios of the components shown in the drawings are not necessarily strict.

[0010] It should be noted that the drawings are schematic diagrams in which emphasis, omission, or adjustment of proportions has been appropriately made to illustrate the present invention, and are not necessarily strictly illustrated, and may differ from the actual shapes, positional relationships, and proportions. In the drawings, the same reference numerals are used to denote substantially the same components, and redundant explanations may be omitted or simplified.

[0011] In the circuit configurations of the present disclosure, "connected" includes not only direct connection by connection terminals and / or wiring conductors, but also electrical connection via matching elements such as inductors and capacitors, and switch circuits. "Connected between A and B" means connected to both A and B between A and B.

[0012] Furthermore, terms indicating the relationship between elements, such as "parallel" and "perpendicular," terms indicating the shape of elements, such as "rectangle," and numerical ranges do not only represent strict meanings, but also include substantially equivalent ranges, for example, including an error of a few percent.

[0013] In addition, in this disclosure, the term "major component of a material" refers to a component that accounts for more than 50% by weight of the material. The major component may be present in any one of single crystal, polycrystalline, and amorphous states, or in a mixture of these states.

[0014] In addition, in the present disclosure, two signals being in phase means that the phases are substantially the same, including a range in which the phases of the two signals differ by about 30%, for example.

[0015] 1A is a plan view of an elastic wave device 1 according to an embodiment. FIG. 1B is a cross-sectional view of the elastic wave device 1 according to the embodiment. FIG. 1A is a plan view of a main surface 31a of a piezoelectric layer 31 viewed from the positive side of the z-axis. FIG. 1B is a cross-sectional view taken along line Ib-Ib in FIG. 1A viewed from the negative side of the x-axis.

[0016] 1A and 1B, acoustic wave device 1 includes piezoelectric layer 31, intermediate layer 32, support substrate 33, IDT electrode 10, reflective electrode 60, and wiring electrodes 40a and 40b. Note that acoustic wave device 1 shown in FIGS. 1A and 1B is intended to illustrate a typical structure of an acoustic wave resonator that constitutes acoustic wave device 1, and the number and lengths of electrode fingers that constitute IDT electrode 10 and reflective electrode 60 are not limited thereto.

[0017] The piezoelectric layer 31 has opposing principal surfaces 31a (first principal surface) and 31b, and is disposed above (in the positive direction of the z-axis) the support substrate 33 and the intermediate layer 32. The piezoelectric layer 31 may be made of, for example, lithium tantalate or lithium niobate, or a material containing any of these materials as a main component. Alternatively, the piezoelectric layer 31 may be made of a material such as quartz or potassium nitride.

[0018] The support substrate 33 is disposed below the piezoelectric layer 31 and the intermediate layer 32 (in the negative z-axis direction) and supports the intermediate layer 32, the piezoelectric layer 31, the IDT electrode 10, the reflective electrode 60, and the wiring electrodes 40a and 40b. The acoustic velocity of the bulk waves propagating through the support substrate 33 is faster than that of the bulk waves propagating through the intermediate layer 32. The support substrate 33 can be made of, for example, a piezoelectric material such as silicon, aluminum nitride, aluminum oxide, lithium niobate, or quartz; a ceramic material such as sapphire, magnesia, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, or forsterite; a dielectric material such as diamond or glass; a semiconductor such as gallium nitride; a resin; or a material containing any of the above materials as a main component.

[0019] The intermediate layer 32 is disposed between the support substrate 33 and the main surface 31b of the piezoelectric layer 31. The intermediate layer 32, for example, causes the sound velocity of the bulk waves propagating through it to be slower than that of the bulk waves propagating through the piezoelectric layer 31. The intermediate layer 32 includes, for example, at least one of silicon oxide and silicon oxynitride. The intermediate layer 32 may also be made of a dielectric such as silicon oxide, silicon oxynitride, glass, lithium oxide, tantalum pentoxide, or a compound in which fluorine, carbon, or boron is added to silicon oxide, or a material containing any of the above materials as a main component.

[0020] The acoustic wave device 1 may also include a high acoustic velocity layer disposed between the intermediate layer 32 and the support substrate 33, the high acoustic velocity layer having bulk waves propagating at a higher acoustic velocity than the bulk waves propagating through the intermediate layer 32. The high acoustic velocity layer may include, for example, at least one of silicon nitride and silicon oxynitride. The high acoustic velocity layer may also be made of a piezoelectric material such as silicon nitride, silicon oxynitride, aluminum nitride, aluminum oxide, lithium niobate, or quartz; a ceramic material such as sapphire, magnesia, silicon carbide, zirconia, cordierite, mullite, steatite, or forsterite; a dielectric material such as diamond-like carbon (DLC), diamond, or glass; a semiconductor material such as silicon or gallium nitride; a resin; or a material containing any of the above materials as a main component.

[0021] The intermediate layer 32 may include an energy trapping layer. The energy trapping layer is disposed between the support substrate 33 and the piezoelectric layer 31 and consists of one or more layers, and the acoustic velocity of bulk waves propagating through at least one of the layers is higher than the acoustic velocity of bulk waves propagating near the piezoelectric layer 31. For example, the energy trapping layer may have a laminated structure of a low acoustic velocity layer and a high acoustic velocity layer. The low acoustic velocity layer is a film in which the acoustic velocity of bulk waves in the low acoustic velocity layer is slower than the acoustic velocity of elastic waves propagating through the piezoelectric layer. The high acoustic velocity layer is a film in which the acoustic velocity of bulk waves in the high acoustic velocity layer is faster than the acoustic velocity of elastic waves propagating through the piezoelectric layer. The energy trapping layer may also be an acoustic impedance layer having a configuration in which low acoustic impedance layers with a relatively low acoustic impedance and high acoustic impedance layers with a relatively high acoustic impedance are alternately laminated.

[0022] The IDT electrode 10 is an example of a first IDT electrode and is arranged on the main surface 31a. As shown in FIG. 1A , the IDT electrode 10 has a plurality of electrode fingers 11a and a plurality of electrode fingers 11b, and busbar electrodes 12a and 12b. The plurality of electrode fingers 11a are an example of a plurality of first electrode fingers and are arranged parallel to each other. The plurality of electrode fingers 11b are an example of a plurality of second electrode fingers and are arranged parallel to each other. The plurality of electrode fingers 11a and the plurality of electrode fingers 11b are arranged parallel to each other so as to be interdigitated with each other.

[0023] The busbar electrode 12a is an example of a first busbar electrode and is configured to connect one ends of the electrode fingers 11a to each other. The busbar electrode 12a extends in a direction (x-axis direction) intersecting the extension direction of the electrode fingers 11a (y-axis direction in FIG. 1A ).

[0024] The busbar electrode 12b is an example of a second busbar electrode and is configured to connect one ends of the electrode fingers 11b to each other. The busbar electrode 12b extends in a direction (x-axis direction) intersecting the extension direction of the electrode fingers 11b (y-axis direction in FIG. 1 ). The busbar electrodes 12a and 12b are arranged opposite each other with the electrode fingers 11a and the electrode fingers 11b sandwiched therebetween. The other ends of the electrode fingers 11a face the busbar electrode 12b, and the other ends of the electrode fingers 11b face the busbar electrode 12a.

[0025] The reflective electrodes 60 are arranged adjacent to the IDT electrode 10 on both sides of the IDT electrode 10 in a direction (x-axis direction) perpendicular to the extension direction of the electrode fingers 11 a and the electrode fingers 11 b. The reflective electrodes 60 are configured to confine a predetermined high-frequency signal that resonates in the IDT electrode 10 within the IDT electrode 10. Note that the reflective electrodes 60 may not be included in the acoustic wave device 1.

[0026] A dielectric film or an insulating film may be disposed between the IDT electrode 10 and the main surface 31 a. Also, a dielectric film or an insulating film may be disposed on the main surface 31 a so as to cover at least a part of the IDT electrode 10.

[0027] The IDT electrode 10 has a layered structure of, for example, titanium (Ti), aluminum (Al), and titanium (Ti). However, the IDT electrode 10 is not limited to the above layered structure, and may be made of a material containing at least one of copper (Cu), gold (Au), silver (Ag), molybdenum (Mo), tungsten (W), titanium (Ti), nickel (Ni), and chromium (Cr), or an alloy or layered film containing some of these metals.

[0028] Wiring electrode 40a is an example of a first wiring electrode, and is arranged on main surface 31a so as to be connected to busbar electrode 12a of IDT electrode 10. Wiring electrode 40b is an example of a first wiring electrode, and is arranged on main surface 31a so as to be connected to busbar electrode 12b of IDT electrode 10. When main surface 31a is viewed in plan, wiring electrode 40a and wiring electrode 40b are arranged opposite each other with IDT electrode 10 interposed therebetween.

[0029] The wiring electrodes 40a and 40b may be made of a material containing aluminum (Al) as a main component, for example. The wiring electrodes 40a and 40b may also be made of the same material as the IDT electrode 10. The thickness of the wiring electrodes 40a and 40b may be greater than the thickness of the IDT electrode 10. This reduces the resistance loss of the wiring electrodes 40a and 40b, and reduces the transmission loss of high-frequency signals input to and output from the IDT electrode 10 through the wiring electrodes 40a and 40b.

[0030] 1A and 1B , when the main surface 31a is viewed in a plane, the main surface 31a includes a region R1 (first region) overlapping with the IDT electrode 10 and a region R2 (second region) overlapping with the wiring electrodes 40a and 40b. Similarly, when the main surface 31b is viewed in a plane, the main surface 31b includes a region R1 (first region) overlapping with the IDT electrode 10 and a region R2 (second region) overlapping with the wiring electrodes 40a and 40b.

[0031] As shown in FIG. 1B , in the elastic wave device 1 according to this embodiment, the thickness T ３２Ｅ is the thickness T of the intermediate layer 32 in the region R1 ３２Ｃ In addition, the total thickness T ３０Ｅ is the total thickness T of the intermediate layer 32 and the piezoelectric layer 31 in the region R1 ３０Ｃ is smaller than.

[0032] This makes it possible to provide an elastic wave device 1 with improved heat dissipation properties.

[0033] For comparison, the configuration of a conventional elastic wave device will be described. FIG. 2A is a plan view of elastic wave device 500 according to a comparative example. FIG. 2B is a cross-sectional view of elastic wave device 500 according to the comparative example. As shown in FIGS. 2A and 2B , elastic wave device 500 includes piezoelectric layer 531, intermediate layer 532, support substrate 33, IDT electrode 10, reflection electrode 60, and wiring electrodes 40 a and 40 b. Elastic wave device 500 according to the comparative example differs from elastic wave device 1 according to the embodiment in the configurations of piezoelectric layer 531 and intermediate layer 532. Therefore, the following description of elastic wave device 500 according to the comparative example will omit a description of the same components as elastic wave device 1 according to the embodiment and will focus on the different components.

[0034] The piezoelectric layer 531 has main surfaces 531a and 531b facing each other, and is disposed above (in the positive direction of the z-axis) the support substrate 33 and the intermediate layer 532. The piezoelectric layer 531 has the same material composition as the piezoelectric layer 31.

[0035] The intermediate layer 532 is disposed between the support substrate 33 and the main surface 531b of the piezoelectric layer 531. For example, the acoustic velocity of the bulk waves propagating through the intermediate layer 532 is slower than that of the bulk waves propagating through the piezoelectric layer 531. The intermediate layer 532 has the same material composition as the intermediate layer 32.

[0036] 2A , when the main surface 531a is viewed in a plane, the main surface 531a includes a region R1 that overlaps with the IDT electrode 10 and a region R2 that overlaps with the wiring electrodes 40a and 40b. Similarly, when the main surface 531b is viewed in a plane, the main surface 531b includes a region R1 that overlaps with the IDT electrode 10 and a region R2 that overlaps with the wiring electrodes 40a and 40b.

[0037] 2B , in the elastic wave device 500 according to the comparative example, the thickness of the intermediate layer 532 in region R2 is equal to the thickness of the intermediate layer 532 in region R1. Furthermore, the total thickness of the intermediate layer 532 and the piezoelectric layer 531 in region R2 is equal to the total thickness of the intermediate layer 532 and the piezoelectric layer 531 in region R1.

[0038] The thickness of piezoelectric layer 531 and the thickness of intermediate layer 532 in region R1 are determined by high-frequency propagation characteristics such as the resonant frequency, resonant bandwidth, and impedance ratio of the acoustic wave resonators that constitute acoustic wave device 500. At the same time, in response to demands for higher output, a configuration that efficiently dissipates heat generated in IDT electrode 10 is desirable. However, in acoustic wave device 500 according to the comparative example, it is difficult to uniformly adjust the thicknesses of piezoelectric layer 531 and intermediate layer 532 solely from the perspective of heat dissipation.

[0039] Returning to the elastic wave device 1 according to the embodiment, a configuration that is advantageous for heat dissipation will be described.

[0040] In the elastic wave device 1 according to this preferred embodiment, the thickness of the piezoelectric layer 31 and the thickness T ３２Ｃ is determined by the high-frequency propagation characteristics such as the resonant frequency, resonant bandwidth, and impedance ratio of the elastic wave resonators constituting the elastic wave device 1. Therefore, the thickness T ３２Ｃ It is difficult to adjust this solely from the standpoint of heat dissipation.

[0041] On the other hand, the thickness of the piezoelectric layer 31 and the thickness T ３２Ｅ does not significantly affect the high-frequency propagation characteristics of the elastic wave resonator. From this perspective, in the elastic wave device 1 according to the present embodiment, the total thickness T ３０Ｅ The total thickness T in the region R1 ３０Ｃ , the thermal resistance from wiring electrode 40a or 40b to support substrate 33 in region R2 is made smaller than the thermal resistance from IDT electrode 10 to support substrate 33 in region R1. Furthermore, the thermal resistivity of intermediate layer 32 is higher than the thermal resistivity of piezoelectric layer 31. Therefore, the thermal resistance can be reduced more effectively by making intermediate layer 32 thinner than by making piezoelectric layer 31 thinner. From this perspective, in elastic wave device 1 according to this embodiment, thickness T ３２Ｅ is the thickness T of the intermediate layer 32 in the region R1. ３２ＣBy making the distance smaller than , the thermal resistance from wiring electrode 40 a or 40 b to support substrate 33 in region R2 can be effectively reduced. This makes it possible to provide elastic wave device 1 with improved heat dissipation properties without degrading the elastic wave propagation characteristics.

[0042] The thickness of the piezoelectric layer 31 in the region R2 may be greater than the thickness of the piezoelectric layer 31 in the region R1.

[0043] According to this, even if the thickness of the piezoelectric layer 31 becomes relatively large in the region R2, the total thickness T ３０Ｅ is the total thickness T of the intermediate layer 32 and the piezoelectric layer 31 in the region R1. ３０Ｃ Since the distance is smaller than the distance t1, the thermal resistance from the wiring electrode 40a or 40b to the support substrate 33 can be reduced.

[0044] The thickness of the piezoelectric layer 31 in the region R2 may be smaller than the thickness of the piezoelectric layer 31 in the region R1.

[0045] This makes it possible to more effectively reduce the thermal resistance from the wiring electrode 40a or 40b to the support substrate 33 in the region R2.

[0046] 1B, the main surface 31a has an inclined region between the busbar electrode 12a and the wiring electrode 40a, but the inclined region may reach the busbar electrode 12a or the electrode finger 11a. The main surface 31b has an inclined region between the busbar electrode 12b and the wiring electrode 40b, but the inclined region may reach the busbar electrode 12b or the electrode finger 11b.

[0047] Furthermore, the region between the busbar electrode 12a and the wiring electrode 40a on the main surface 31a may not include a slope but may include one or more steps. Furthermore, the region between the busbar electrode 12b and the wiring electrode 40b on the main surface 31b may not include a slope but may include one or more steps.

[0048] Furthermore, the shape of the principal surface 31a and the shape of the principal surface 31b may be different. For example, the region between the busbar electrode 12a and the wiring electrode 40a on the principal surface 31a may have a stepped shape, and the region between the busbar electrode 12a and the wiring electrode 40a on the principal surface 31b may have an inclined shape.

[0049] 2 Configuration of Elastic Wave Device 1A According to Modification 1 Fig. 3A is a plan view of elastic wave device 1A according to Modification 1 of the embodiment. Fig. 3B is a cross-sectional view of elastic wave device 1A according to Modification 1 of the embodiment. Fig. 3A is a plan view of main surface 31a of piezoelectric layer 31 as viewed from the positive side of the z-axis. Fig. 3B is a cross-sectional view taken along line IIIb-IIIb in Fig. 3A as viewed from the negative side of the x-axis.

[0050] 3A and 3B , elastic wave device 1A includes piezoelectric layer 31, intermediate layer 32, support substrate 33, planar electrode 50, IDT electrode 10, reflective electrode 60, and wiring electrodes 40 a and 40 b. Elastic wave device 1A according to Modification 1 differs from elastic wave device 1 according to the embodiment in that planar electrode 50 is provided. Therefore, the following description of elastic wave device 1A according to Modification 1 will omit a description of the same components as those of elastic wave device 1 according to the embodiment and will focus on the different components.

[0051] 3A , when the main surface 31a is viewed in a plane, the main surface 31a includes a region R1 (first region) overlapping with the IDT electrode 10 and a region R2 (second region) overlapping with the wiring electrodes 40a and 40b. Similarly, when the main surface 31b is viewed in a plane, the main surface 31b includes a region R1 (first region) overlapping with the IDT electrode 10 and a region R2 (second region) overlapping with the wiring electrodes 40a and 40b.

[0052] The planar electrode 50 is disposed between the principal surface 31b and the interface 32b between the support substrate 33 and the intermediate layer 32 so as to overlap with the IDT electrode 10 when the principal surfaces 31a and 31b are viewed in plan. More specifically, in the above planar view, the planar electrode 50 overlaps at least with the crossing width region where the plurality of electrode fingers 11a and the plurality of electrode fingers 11b cross each other, but does not overlap with region R2. The planar electrode 50 can be made of, for example, aluminum (Al) or a material containing aluminum as its main component.

[0053] By disposing the planar electrode 50 on the intermediate layer 32, the elastic wave device 1A can ensure a large capacitance, thereby enabling the elastic wave device 1A to be miniaturized.

[0054] As shown in FIG. 3B , in the elastic wave device 1A according to this modification, the thickness T ３２Ｅ is the thickness T of the intermediate layer 32 in the region R1 ３２Ｃ In addition, the total thickness T ３０Ｅ is the total thickness T of the intermediate layer 32 and the piezoelectric layer 31 in the region R1 ３０Ｃ is smaller than.

[0055] This makes it possible to provide an elastic wave device 1A with improved heat dissipation properties without deteriorating elastic wave propagation characteristics.

[0056] The thickness T of the intermediate layer 32 in the region R2 ３２Ｅ and the thickness T of the intermediate layer 32 in the region R1 ３２Ｃ The difference between these values ​​is smaller than the thickness of the planar electrode 50.

[0057] This allows a height difference smaller than the thickness of the planar electrode 50 to occur between the regions R1 and R2 on the main surface of the intermediate layer 32 that contacts the piezoelectric layer 31, thereby suppressing distortion of the piezoelectric layer 31 that occurs due to the height difference. This therefore suppresses deterioration of the crystallinity of the piezoelectric layer 31, thereby suppressing deterioration of the elastic wave propagation characteristics.

[0058] Furthermore, the distance between the piezoelectric layer 31 and the planar electrode 50 is smaller than the distance between the support substrate 33 and the planar electrode 50 .

[0059] This allows the capacitance of elastic wave device 1A to be increased, thereby enabling the size of elastic wave device 1A to be reduced.

[0060] The distance between the piezoelectric layer 31 and the planar electrode 50 is the thickness T of the intermediate layer 32 in the region R2. ３２Ｅ and the thickness T of the intermediate layer 32 in the region R1 ３２Ｃ is smaller than the difference between

[0061] This allows the capacitance of elastic wave device 1A to be increased, thereby enabling the size of elastic wave device 1A to be reduced.

[0062] 3B , the main surface 31 a (first main surface) of the piezoelectric layer 31 has an inclined region between the busbar electrode 12 a and the wiring electrode 40 a, but the inclined region may reach the busbar electrode 12 a or the electrode finger 11 a. The main surface 31 b (second main surface) of the piezoelectric layer 31 has an inclined region between the busbar electrode 12 b and the wiring electrode 40 b, but the inclined region may reach the busbar electrode 12 b or the electrode finger 11 b.

[0063] Furthermore, when the main surfaces 31 a and 31 b of the piezoelectric layer 31 are viewed from above, the planar electrode 50 may overlap the intersection region between the electrode fingers 11 a and 11 b, but may not overlap the busbar electrodes 12 a and 12 b. Furthermore, in the above-mentioned planar view, the planar electrode 50 may overlap the intersection region and may overlap the busbar electrodes 12 a and 12 b.

[0064] Furthermore, the region on the main surface 31a between the busbar electrode 12a and the wiring electrode 40a may not include a slope but may include one or more steps. Furthermore, the region on the main surface 31a between the busbar electrode 12b and the wiring electrode 40b may not include a slope but may include one or more steps.

[0065] Furthermore, the shape of the principal surface 31a and the shape of the principal surface 31b may be different. For example, the region between the busbar electrode 12a and the wiring electrode 40a on the principal surface 31a may have a stepped shape, and the region between the busbar electrode 12a and the wiring electrode 40a on the principal surface 31b may have an inclined shape.

[0066] 3. Configuration of Elastic Wave Device 1B According to Modification 2 FIG. 4A is a plan view of elastic wave device 1B according to Modification 2 of the embodiment. FIG. 4B is a first cross-sectional view of elastic wave device 1B according to Modification 2 of the embodiment. FIG. 4C is a second cross-sectional view of elastic wave device 1B according to Modification 2 of the embodiment. FIG. 4A is a plan view of main surface 31a of piezoelectric layer 31B from the positive side of the z-axis. FIG. 4B is a cross-sectional view taken along line IVb-IVb in FIG. 4A as viewed from the negative side of the y-axis. FIG. 4C is a cross-sectional view taken along line IVc-IVc in FIG. 4A as viewed from the negative side of the x-axis. As shown in FIGS. 4A to 4C, elastic wave device 1B includes piezoelectric layer 31B, intermediate layer 32, support substrate 33, IDT electrodes 10 and 20, reflective electrode 60, and wiring electrodes 40a and 40b. Elastic wave device 1B according to Modification 2 differs from elastic wave device 1 according to the embodiment in that IDT electrode 20 is provided and in the configuration of piezoelectric layer 31B. Therefore, the following description of elastic wave device 1B according to Modification 2 will omit a description of the same components as elastic wave device 1 according to the embodiment and will focus on the different components.

[0067] As shown in FIGS. 4B and 4C, the piezoelectric layer 31B has opposing main surfaces 31a (first main surface) and 31b, and is disposed above the support substrate 33 and the intermediate layer 32 (positive direction of the z-axis).

[0068] The intermediate layer 32 is disposed between the support substrate 33 and the main surface 31b of the piezoelectric layer 31B. For example, the acoustic velocity of the bulk waves propagating through the intermediate layer 32 is slower than that of the bulk waves propagating through the piezoelectric layer 31B.

[0069] The elastic wave device 1B may include a high acoustic velocity layer disposed between the intermediate layer 32 and the support substrate 33, the high acoustic velocity layer propagating the bulk waves at a higher acoustic velocity than the bulk waves propagating through the intermediate layer 32.

[0070] The intermediate layer 32 may include an energy trapping layer. The energy trapping layer is disposed between the support substrate 33 and the piezoelectric layer 31B and is composed of one or more layers, and the acoustic velocity of the bulk waves propagating through at least one of the layers is greater than the acoustic velocity of the bulk waves propagating near the piezoelectric layer 31B.

[0071] The IDT electrode 10 is an example of a first IDT electrode and is arranged on the main surface 31a. The IDT electrode 10 has a plurality of electrode fingers 11a and a plurality of electrode fingers 11b, and busbar electrodes 12a and 12b. The plurality of electrode fingers 11a are an example of a plurality of first electrode fingers and are arranged parallel to each other. The plurality of electrode fingers 11b are an example of a plurality of second electrode fingers and are arranged parallel to each other. The plurality of electrode fingers 11a and the plurality of electrode fingers 11b are arranged parallel to each other so as to be interdigitated with each other.

[0072] The busbar electrode 12a is an example of a first busbar electrode and is configured to connect one ends of the electrode fingers 11a to each other. The busbar electrode 12a extends in a direction (x-axis direction) intersecting the extension direction of the electrode fingers 11a (y-axis direction in FIG. 1 ).

[0073] The busbar electrode 12b is an example of a second busbar electrode and is configured to connect one ends of the electrode fingers 11b to each other. The busbar electrode 12b extends in a direction (x-axis direction) intersecting the extension direction of the electrode fingers 11b (y-axis direction in FIG. 1 ). The busbar electrodes 12a and 12b are arranged opposite each other with the electrode fingers 11a and the electrode fingers 11b sandwiched therebetween. The other ends of the electrode fingers 11a face the busbar electrode 12b, and the other ends of the electrode fingers 11b face the busbar electrode 12a.

[0074] A dielectric film or an insulating film may be disposed between the IDT electrode 10 and the main surface 31 a. Also, a dielectric film or an insulating film may be disposed on the main surface 31 a so as to cover at least a part of the IDT electrode 10.

[0075] The IDT electrode 20 is an example of a second IDT electrode and is arranged on the main surface 31b. The IDT electrode 20 has a plurality of electrode fingers 21a and a plurality of electrode fingers 21b, and busbar electrodes 22a and 22b. The plurality of electrode fingers 21a are an example of a plurality of third electrode fingers and are arranged parallel to each other. The plurality of electrode fingers 21b are an example of a plurality of fourth electrode fingers and are arranged parallel to each other. The plurality of electrode fingers 21a and the plurality of electrode fingers 21b are arranged parallel to each other so as to be interdigitated with each other.

[0076] The busbar electrode 22a is an example of a third busbar electrode and is configured to connect one ends of the electrode fingers 21a to each other. The busbar electrode 22a extends in a direction (x-axis direction) intersecting the extension direction of the electrode fingers 21a (y-axis direction in FIG. 1 ).

[0077] The busbar electrode 22b is an example of a fourth busbar electrode and is configured to connect one ends of the electrode fingers 21b to each other. The busbar electrode 22b extends in a direction (x-axis direction) intersecting the extension direction of the electrode fingers 21b (y-axis direction in FIG. 1 ). The busbar electrodes 22a and 22b are arranged opposite each other with the electrode fingers 21a and 21b sandwiched therebetween. The other ends of the electrode fingers 21a face the busbar electrode 22b, and the other ends of the electrode fingers 21b face the busbar electrode 22a.

[0078] A dielectric film or an insulating film may be disposed between the IDT electrode 20 and the main surface 31b.

[0079] The IDT electrode 20 has a layered structure of, for example, titanium (Ti), aluminum (Al), and titanium (Ti). However, the IDT electrode 20 is not limited to the above layered structure, and may be made of a material containing at least one of copper (Cu), gold (Au), silver (Ag), molybdenum (Mo), tungsten (W), titanium (Ti), nickel (Ni), and chromium (Cr), or an alloy or layered film containing some of these metals.

[0080] When the main surfaces 31a and 31b are viewed in plan, the plurality of electrode fingers 11a included in the IDT electrode 10 overlap one-to-one with the plurality of electrode fingers 21a included in the IDT electrode 20. The plurality of electrode fingers 11b included in the IDT electrode 10 overlap one-to-one with the plurality of electrode fingers 21b included in the IDT electrode 20. The plurality of electrode fingers 11a and the plurality of electrode fingers 21a are excited in phase, and the plurality of electrode fingers 11b and the plurality of electrode fingers 21b are excited in phase. This makes it possible to suppress spurious responses such as higher-order modes.

[0081] Wiring electrode 40a is an example of a first wiring electrode, and is arranged on main surface 31a so as to be connected to busbar electrode 12a of IDT electrode 10. Wiring electrode 40b is an example of a first wiring electrode, and is arranged on main surface 31a so as to be connected to busbar electrode 12b of IDT electrode 10. When main surface 31a is viewed in plan, wiring electrode 40a and wiring electrode 40b are arranged opposite each other with IDT electrode 10 interposed therebetween.

[0082] Wiring electrode 40c is an example of a second wiring electrode, and is arranged on main surface 31b so as to be connected to bus bar electrode 22a of IDT electrode 20. Wiring electrode 40d is an example of a second wiring electrode, and is arranged on main surface 31b so as to be connected to bus bar electrode 22b of IDT electrode 20. Wiring electrode 40c and wiring electrode 40d are arranged opposite each other with IDT electrode 20 interposed therebetween when main surface 31b is viewed in plan.

[0083] When the main surfaces 31a and 31b are viewed in plan, the IDT electrode 20 overlaps with the region R1, and the wiring electrodes 40c and 40d overlap with the region R2.

[0084] The wiring electrodes 40c and 40d may be made of a material containing aluminum (Al) as a main component, or may be made of the same material as the IDT electrode 20.

[0085] As shown in FIG. 4C , in the elastic wave device 1B according to this modification, the thickness T ３２Ｅ is the thickness T of the intermediate layer 32 in the region R1 ３２Ｃ In addition, the total thickness T ３０Ｅ is the total thickness T of the intermediate layer 32 and the piezoelectric layer 31B in the region R1 ３０Ｃ is smaller than.

[0086] According to this, the thickness T of the intermediate layer 32 in the region R2 ３２Ｅ is the thickness T of the intermediate layer 32 in the region R1. ３２ＣBy making the distance smaller than , the thermal resistance from wiring electrodes 40 a, 40 b, 40 c, or 40 d in region R2 to support substrate 33 can be effectively reduced. This makes it possible to provide elastic wave device 1B with improved heat dissipation properties without degrading the elastic wave propagation characteristics.

[0087] In this modification, the thickness T of the piezoelectric layer 31B in the region R2 ３１Ｅ is the thickness T of the piezoelectric layer 31B in the region R1 ３１Ｃ is greater than.

[0088] According to this, in the region R2, the thickness T ３１Ｅ Even if the thickness T of the intermediate layer 32 becomes relatively large, ３２Ｅ and total thickness T ３０Ｅ are the thickness T ３２Ｃ and total thickness T ３０Ｃ Since the thermal resistance from the wiring electrodes 40a, 40b, 40c, or 40d to the support substrate 33 is smaller than the above, the thermal resistance can be reduced.

[0089] In addition, the thickness T of the piezoelectric layer 31B in the region R2 ３１Ｅ is the thickness T of the piezoelectric layer 31 in the region R1 ３１Ｃ It may be smaller than

[0090] This makes it possible to more effectively reduce the thermal resistance from the wiring electrode 40a or 40b to the support substrate 33 in the region R2.

[0091] 4C , the main surface 31a has an inclined region between the busbar electrode 12a and the wiring electrode 40a, but the inclined region may reach the busbar electrode 12a or the electrode finger 11a. The main surface 31b has an inclined region between the busbar electrode 12b and the wiring electrode 40b, but the inclined region may reach the busbar electrode 12b or the electrode finger 11b.

[0092] Furthermore, the region on the main surface 31a between the busbar electrode 12a and the wiring electrode 40a may not include a slope but may include one or more steps. Furthermore, the region on the main surface 31a between the busbar electrode 12b and the wiring electrode 40b may not include a slope but may include one or more steps.

[0093] Furthermore, the shape of the principal surface 31a and the shape of the principal surface 31b may be different. For example, the region between the busbar electrode 12a and the wiring electrode 40a on the principal surface 31a may have a stepped shape, and the region between the busbar electrode 12a and the wiring electrode 40a on the principal surface 31b may have an inclined shape.

[0094] [4 Effects, etc.] As described above, elastic wave device 1 according to the embodiment includes support substrate 33, piezoelectric layer 31 having principal surfaces 31 a and 31 b facing each other, IDT electrode 10 disposed on principal surface 31 a, wiring electrode 40 a disposed on principal surface 31 a and connected to IDT electrode 10, and intermediate layer 32 disposed between support substrate 33 and principal surface 31 b. Principal surface 31 b includes region R1 overlapping with IDT electrode 10 and region R2 overlapping with wiring electrode 40 a when principal surfaces 31 a and 31 b are viewed in plan. A thickness T of intermediate layer 32 in region R2 is 1 / 2 mm. ３２Ｅ is the thickness T of the intermediate layer 32 in the region R1 ３２Ｃ and the total thickness T ３０Ｅ is the total thickness T of the intermediate layer 32 and the piezoelectric layer 31 in the region R1 ３０Ｃ is smaller than.

[0095] The thickness of the piezoelectric layer 31 and the thickness T of the intermediate layer 32 in the region R1 ３２Ｃ is determined by the high-frequency propagation characteristics such as the resonant frequency, resonant bandwidth, and impedance ratio of the elastic wave resonators constituting the elastic wave device 1. Therefore, the thickness T ３２Ｃ It is difficult to adjust this solely from the standpoint of heat dissipation.

[0096] On the other hand, the thickness of the piezoelectric layer 31 and the thickness T ３２Ｅ does not significantly affect the high frequency propagation characteristics of the elastic wave resonator. ３０Ｅ The total thickness T in the region R1 ３０ＣBy making the thickness T of the intermediate layer 32 in region R2 smaller than that of the IDT electrode 10, the thermal resistance from the wiring electrode 40a or 40b to the support substrate 33 in region R2 is made smaller than the thermal resistance from the IDT electrode 10 to the support substrate 33 in region R1. Also, the thermal resistivity of the intermediate layer 32 is higher than that of the piezoelectric layer 31. Therefore, the thermal resistance can be reduced more effectively by making the intermediate layer 32 thinner than by making the piezoelectric layer 31 thinner. From this perspective, the thickness T of the intermediate layer 32 in region R2 is ３２Ｅ is the thickness T of the intermediate layer 32 in the region R1. ３２Ｃ By making the distance smaller than , the thermal resistance from wiring electrode 40 a or 40 b to support substrate 33 in region R2 can be effectively reduced. This makes it possible to provide elastic wave device 1 with improved heat dissipation properties without degrading the elastic wave propagation characteristics.

[0097] Furthermore, for example, in the elastic wave device 1, the IDT electrode 10 includes a plurality of electrode fingers 11a and a plurality of electrode fingers 11b arranged parallel to each other, a busbar electrode 12a configured to connect one ends of the plurality of electrode fingers 11a to each other, and a busbar electrode 12b configured to connect one ends of the plurality of electrode fingers 11b to each other and arranged opposite the busbar electrode 12a across the plurality of electrode fingers 11a and the plurality of electrode fingers 11b, and the wiring electrode 40a is connected to the busbar electrode 12a.

[0098] This makes it possible to provide a surface acoustic wave resonator with improved heat dissipation properties.

[0099] For example, the elastic wave device 1A according to variant example 1 further includes a planar electrode 50 disposed between the main surface 31b and the interface 32b between the support substrate 33 and the intermediate layer 32, so as to overlap the IDT electrode 10 in the planar view.

[0100] In this case, by disposing the planar electrode 50 on the intermediate layer 32, the elastic wave device 1A can ensure a large capacitance, thereby enabling the elastic wave device 1A to be miniaturized.

[0101] In the elastic wave device 1A, the thickness T of the intermediate layer 32 in the region R2 ３２Ｅ and the thickness T of the intermediate layer 32 in the region R1 ３２Ｃ The difference between these values ​​is smaller than the thickness of the planar electrode 50.

[0102] This creates a height difference between the regions R1 and R2 on the main surface 31b that is smaller than the thickness of the planar electrode 50, thereby suppressing distortion of the piezoelectric layer 31 caused by the height difference. This prevents deterioration of the crystallinity of the piezoelectric layer 31, thereby preventing deterioration of the elastic wave propagation characteristics.

[0103] Furthermore, for example, in the elastic wave device 1A, the distance between the piezoelectric layer 31 and the planar electrode 50 is smaller than the distance between the support substrate 33 and the planar electrode 50 .

[0104] This allows the capacitance of elastic wave device 1A to be increased, thereby enabling the size of elastic wave device 1A to be reduced.

[0105] Furthermore, for example, in the elastic wave device 1A, the distance between the piezoelectric layer 31 and the planar electrode 50 is smaller than the difference in thickness between the intermediate layer 32 in region R2 and the intermediate layer 32 in region R1.

[0106] This allows the capacitance of elastic wave device 1A to be increased, thereby enabling the size of elastic wave device 1A to be reduced.

[0107] For example, the elastic wave device 1B according to variant example 2 further includes an IDT electrode 20 arranged on the principal surface 31 b and a wiring electrode 40 c arranged on the principal surface 31 b and connected to the IDT electrode 20, and in the above-mentioned planar view, the IDT electrode 20 overlaps with region R1, and the wiring electrode 40 c overlaps with region R2.

[0108] For example, in elastic wave device 1B, IDT electrode 20 includes a plurality of electrode fingers 21 a and a plurality of electrode fingers 21 b arranged parallel to each other, a busbar electrode 22 a configured to connect one ends of the plurality of electrode fingers 21 a to each other, and a busbar electrode 22 b configured to connect one ends of the plurality of electrode fingers 21 b to each other and arranged opposite busbar electrode 22 a across the plurality of electrode fingers 21 a and 21 b, and wiring electrode 40 c is connected to busbar electrode 22 a, and wiring electrode 40 d is connected to busbar electrode 22 b.

[0109] This makes it possible to provide a surface acoustic wave resonator with improved heat dissipation properties.

[0110] Furthermore, for example, in elastic wave device 1B, when principal surfaces 31a and 31b are viewed in plan, the plurality of electrode fingers included in IDT electrode 10 overlap with the plurality of electrode fingers included in IDT electrode 20 in a one-to-one relationship.

[0111] According to this, when multiple electrode fingers 11a and multiple electrode fingers 21a are excited in phase and multiple electrode fingers 11b and multiple electrode fingers 21b are excited in phase, it is possible to suppress spurious emissions such as higher modes.

[0112] Furthermore, for example, in the elastic wave device 1B, the thickness T ３１Ｅ is the thickness T of the piezoelectric layer 31B in the region R1 ３１Ｃ is smaller than.

[0113] This makes it possible to further effectively reduce the thermal resistance from the wiring electrode 40a or 40b to the support substrate 33 in the region R2.

[0114] Furthermore, for example, in the elastic wave device 1B, the thickness T ３１Ｅ is the thickness T of the piezoelectric layer 31B in the region R1 ３１Ｃ is greater than.

[0115] According to this, in the region R2, the thickness T ３１Ｅ Even if the total thickness T ３０Ｅ is the total thickness T of the intermediate layer 32 and the piezoelectric layer 31 in the region R1. ３０Ｃ Since the distance is smaller than the distance t1, the thermal resistance from the wiring electrode 40a to the support substrate 33 can be reduced.

[0116] Furthermore, for example, in the acoustic wave devices 1, 1A, and 1B, the piezoelectric layer 31 (31B) includes either lithium tantalate or lithium niobate.

[0117] Furthermore, for example, in the elastic wave devices 1, 1A, and 1B, the acoustic velocity of the bulk waves propagating through the intermediate layer 32 is slower than that of the bulk waves propagating through the piezoelectric layer 31 (31B).

[0118] This allows unwanted waves of higher modes to leak efficiently into the intermediate layer 32 .

[0119] Furthermore, for example, in the acoustic wave devices 1, 1A, and 1B, the intermediate layer 32 includes at least one of silicon oxide and silicon oxynitride.

[0120] Furthermore, for example, in elastic wave devices 1 , 1A, and 1B, the acoustic velocity of the bulk waves propagating through support substrate 33 is faster than that of the bulk waves propagating through intermediate layer 32 .

[0121] This makes it possible to suppress unwanted waves in higher modes.

[0122] Furthermore, for example, in the acoustic wave devices 1, 1A, and 1B, the support substrate 33 includes silicon or silicon carbide.

[0123] For example, the elastic wave devices 1, 1A, and 1B further include a high acoustic velocity layer disposed between the intermediate layer 32 and the support substrate 33, in which the acoustic velocity of the bulk waves propagating through the intermediate layer 32 is faster than that of the bulk waves propagating through the intermediate layer 32.

[0124] This makes it possible to suppress unwanted waves in higher modes.

[0125] Furthermore, for example, in the acoustic wave devices 1, 1A, and 1B, the high acoustic velocity layer includes at least one of silicon nitride and silicon oxynitride.

[0126] While the elastic wave device according to the present invention has been described above with reference to exemplary embodiments and modifications thereof, the present invention is not limited to the exemplary embodiments and modifications thereof. The present invention also includes other embodiments realized by combining any of the components in the exemplary embodiments and modifications thereof, as well as modifications obtained by applying various modifications to the exemplary embodiments and modifications thereof that would occur to those skilled in the art without departing from the spirit of the present invention.

[0127] The features of the acoustic wave devices described based on the above-described embodiment and modifications will be described below.

[0128] <1> An elastic wave device comprising: a support substrate; a piezoelectric layer having first and second principal surfaces opposing each other; a first IDT electrode disposed on the first principal surface; a first wiring electrode disposed on the first principal surface and connected to the first IDT electrode; and an intermediate layer disposed between the support substrate and the second principal surface, wherein the second principal surface includes a first region overlapping with the first IDT electrode and a second region overlapping with the first wiring electrode when the first and second principal surfaces are viewed in a plane; a thickness of the intermediate layer in the second region is smaller than a thickness of the intermediate layer in the first region; and a total thickness of the intermediate layer and the piezoelectric layer in the second region is smaller than a total thickness of the intermediate layer and the piezoelectric layer in the first region.

[0129] <2> The elastic wave device according to <1>, wherein the first IDT electrode includes: a plurality of first electrode fingers and a plurality of second electrode fingers arranged parallel to each other; a first bus bar electrode configured to connect one ends of the plurality of first electrode fingers to each other; and a second bus bar electrode configured to connect one ends of the plurality of second electrode fingers to each other and arranged to face the first bus bar electrode with the plurality of first electrode fingers and the plurality of second electrode fingers interposed therebetween; and the first wiring electrode is connected to the first bus bar electrode or the second bus bar electrode.

[0130] <3> The elastic wave device according to <1> or <2>, further comprising: a planar electrode disposed between the second principal surface and an interface between the support substrate and the intermediate layer, the planar electrode overlapping the first IDT electrode in the planar view.

[0131] <4> The acoustic wave device according to <3>, wherein a difference between a thickness of the intermediate layer in the second region and a thickness of the intermediate layer in the first region is smaller than a thickness of the planar electrode.

[0132] <5> The acoustic wave device according to <3> or <4>, wherein the distance between the piezoelectric layer and the planar electrode is smaller than the distance between the support substrate and the planar electrode.

[0133] <6> The elastic wave device according to <3> or <4>, wherein the distance between the piezoelectric layer and the planar electrode is smaller than the difference between the thickness of the intermediate layer in the second region and the thickness of the intermediate layer in the first region.

[0134] <7> The elastic wave device according to any one of <1> to <6>, further including: a second IDT electrode arranged on the second principal surface; and a second wiring electrode arranged on the second principal surface and connected to the second IDT electrode, wherein, in the planar view, the second IDT electrode overlaps with the first region, and the second wiring electrode overlaps with the second region.

[0135] <8> The elastic wave device according to <7>, wherein the second IDT electrode includes: a plurality of third electrode fingers and a plurality of fourth electrode fingers arranged parallel to each other; a third bus bar electrode configured to connect one ends of the third electrode fingers to each other; and a fourth bus bar electrode configured to connect one ends of the fourth electrode fingers to each other and arranged to face the third bus bar electrode with the third electrode fingers and the fourth electrode fingers interposed therebetween; and the second wiring electrode is connected to the third bus bar electrode or the fourth bus bar electrode.

[0136] <9> The elastic wave device according to <7> or <8>, wherein, in a plan view of the first principal surface and the second principal surface, each of the plurality of electrode fingers included in the first IDT electrode overlaps with each of the plurality of electrode fingers included in the second IDT electrode in a one-to-one relationship.

[0137] <10> The acoustic wave device according to any one of <1> to <9>, wherein the thickness of the piezoelectric layer in the second region is smaller than the thickness of the piezoelectric layer in the first region.

[0138] <11> The acoustic wave device according to any one of <1> to <9>, wherein the thickness of the piezoelectric layer in the second region is greater than the thickness of the piezoelectric layer in the first region.

[0139] <12> The acoustic wave device according to any one of <1> to <11>, wherein the piezoelectric layer contains either lithium tantalate or lithium niobate.

[0140] <13> The acoustic wave device according to any one of <1> to <12>, wherein the intermediate layer propagates bulk waves at a sound velocity slower than that of the bulk waves propagating in the piezoelectric layer.

[0141] <14> The acoustic wave device according to <13>, wherein the intermediate layer includes at least one of silicon oxide and silicon oxynitride.

[0142] <15> The acoustic wave device according to any one of <1> to <14>, wherein the bulk waves propagating through the support substrate have a higher acoustic velocity than the bulk waves propagating through the intermediate layer.

[0143] <16> The acoustic wave device according to <15>, wherein the support substrate includes silicon or silicon carbide.

[0144] <17> The elastic wave device according to any one of <1> to <16>, further comprising a high acoustic velocity layer disposed between the intermediate layer and the support substrate, the high acoustic velocity layer allowing bulk waves to propagate through the high acoustic velocity layer at a higher acoustic velocity than bulk waves to propagate through the intermediate layer.

[0145] <18> The acoustic wave device according to <17>, wherein the high acoustic velocity layer includes at least one of silicon nitride and silicon oxynitride.

[0146] INDUSTRIAL APPLICABILITY The present invention can be widely used as an acoustic wave device disposed in a front end portion of communication devices such as mobile phones.

[0147] 1, 1A, 1B, 500 Acoustic wave device 10, 20 IDT electrode 11a, 11b, 21a, 21b Electrode finger 12a, 12b, 22a, 22b Bus bar electrode 31, 31B, 531 Piezoelectric layer 31a, 31b, 531a, 531b Main surface 32, 532 Intermediate layer 32b Interface 33 Support substrate 40a, 40b, 40c, 40d Wiring electrode 60 Reflection electrode

Claims

1. An elastic wave device comprising: a support substrate; a piezoelectric layer having first and second principal surfaces opposing each other; a first IDT electrode disposed on the first principal surface; a first wiring electrode disposed on the first principal surface and connected to the first IDT electrode; and an intermediate layer disposed between the support substrate and the second principal surface, wherein the second principal surface includes a first region overlapping with the first IDT electrode and a second region overlapping with the first wiring electrode when the first and second principal surfaces are viewed in a plane; the thickness of the intermediate layer in the second region is smaller than the thickness of the intermediate layer in the first region; and the total thickness of the intermediate layer and the piezoelectric layer in the second region is smaller than the total thickness of the intermediate layer and the piezoelectric layer in the first region.

2. The elastic wave device of claim 1, wherein the first IDT electrode includes: a plurality of first electrode fingers and a plurality of second electrode fingers arranged parallel to each other; a first bus bar electrode configured to connect one ends of the plurality of first electrode fingers; and a second bus bar electrode configured to connect one ends of the plurality of second electrode fingers and arranged opposite the first bus bar electrode across the plurality of first electrode fingers and the plurality of second electrode fingers; and the first wiring electrode is connected to the first bus bar electrode or the second bus bar electrode.

3. The elastic wave device according to claim 1 or 2, further comprising a planar electrode disposed between the second principal surface and the interface between the support substrate and the intermediate layer, and arranged so as to overlap the first IDT electrode in the planar view.

4. The acoustic wave device according to claim 3, wherein the difference between the thickness of the intermediate layer in the second region and the thickness of the intermediate layer in the first region is smaller than the thickness of the planar electrode.

5. The acoustic wave device according to claim 3 or 4, wherein the distance between the piezoelectric layer and the planar electrode is smaller than the distance between the support substrate and the planar electrode.

6. The elastic wave device according to claim 3 or 4, wherein the distance between the piezoelectric layer and the planar electrode is smaller than the difference between the thickness of the intermediate layer in the second region and the thickness of the intermediate layer in the first region.

7. The elastic wave device according to any one of claims 1 to 6, further comprising: a second IDT electrode arranged on the second principal surface; and a second wiring electrode arranged on the second principal surface and connected to the second IDT electrode, wherein, in the planar view, the second IDT electrode overlaps with the first region, and the second wiring electrode overlaps with the second region.

8. The elastic wave device described in claim 7, wherein the second IDT electrode includes: a plurality of third electrode fingers and a plurality of fourth electrode fingers arranged parallel to each other; a third bus bar electrode configured to connect one ends of the plurality of third electrode fingers together; and a fourth bus bar electrode configured to connect one ends of the plurality of fourth electrode fingers together and arranged opposite the third bus bar electrode with the plurality of third electrode fingers and the plurality of fourth electrode fingers in between; and the second wiring electrode is connected to the third bus bar electrode or the fourth bus bar electrode.

9. The acoustic wave device according to claim 7 or 8, wherein, when the first principal surface and the second principal surface are viewed in a plan view, each of the plurality of electrode fingers included in the first IDT electrode overlaps each of the plurality of electrode fingers included in the second IDT electrode in a one-to-one relationship.

10. The elastic wave device according to any one of claims 1 to 9, wherein the thickness of the piezoelectric layer in the second region is smaller than the thickness of the piezoelectric layer in the first region.

11. The elastic wave device according to any one of claims 1 to 9, wherein the thickness of the piezoelectric layer in the second region is greater than the thickness of the piezoelectric layer in the first region.

12. The acoustic wave device according to any one of claims 1 to 11, wherein the piezoelectric layer contains either lithium tantalate or lithium niobate.

13. The elastic wave device according to any one of claims 1 to 12, wherein the intermediate layer propagates bulk waves at a sound velocity slower than that of the bulk waves propagating through the piezoelectric layer.

14. The acoustic wave device according to claim 13, wherein the intermediate layer includes at least one of silicon oxide and silicon oxynitride.

15. The acoustic wave device according to any one of claims 1 to 14, wherein the bulk waves propagating through the support substrate have a higher acoustic velocity than the bulk waves propagating through the intermediate layer.

16. The acoustic wave device according to claim 15, wherein the support substrate includes silicon or silicon carbide.

17. The elastic wave device according to any one of claims 1 to 16, further comprising a high acoustic velocity layer disposed between the intermediate layer and the support substrate, the high acoustic velocity layer allowing bulk waves to propagate through the high acoustic velocity layer at a higher acoustic velocity than bulk waves propagating through the intermediate layer.

18. The acoustic wave device according to claim 17, wherein the high acoustic velocity layer includes at least one of silicon nitride and silicon oxynitride.

Images