Elastic wave device

Abstract

Provided is an elastic wave device capable of suppressing crack propagation. This elastic wave device (10) is provided with: a support member having a support substrate; a piezoelectric layer (14) provided on the support member and having a first main surface (14a) and a second main surface (14b) facing each other; and an (IDT) electrode (11) provided on at least one of the first main surface (14a) and the second main surface (14b) of the piezoelectric layer (14). The (IDT) electrode (11) has: a first bus bar section (26) and a second bus bar section (27) facing each other; and a plurality of electrode fingers including at least one first electrode finger (28), one end of which is connected to the first bus bar section (26), and at least one second electrode finger (29), one end of which is connected to the second bus bar section (27). The first electrode fingers (28) and the second electrode fingers (29) are interleaved with each other. When viewed from a direction orthogonal to a direction in which the first electrode fingers (28) and the second electrode fingers (29) extend, a region in which adjacent first electrode fingers (28) and second electrode fingers (29) overlap each other is an intersection region (F). The support member is provided with a hollow portion (10a). The hollow portion (10a) overlaps the intersection region (F) in plan view. At least one of the first bus bar section (26) and the second bus bar section (27) has: outer bus bars (26a, 27a) that do not overlap the hollow section (10a) in plan view; and at least one protruding electrode (26c, 27c) extending from the outer bus bar toward the intersecting region (F) and facing an electrode finger that is not connected to the outer bus bar among the plurality of electrode fingers. The protruding electrode overlaps the outer peripheral edge of the hollow portion (10a) in plan view.

Description

Technical Field

[0001] The present invention relates to elastic wave devices. Background Art

[0002] In the past, elastic wave devices were widely used in filters for portable phones and the like. In recent years, an elastic wave device using a body wave in a thickness shear mode as described in the following patent document 1 has been proposed. In this elastic wave device, a piezoelectric layer is provided on a support body. An IDT (Interdigital Transducer) electrode is provided on the piezoelectric layer. The IDT electrode has a pair of comb-tooth electrodes. Each comb-tooth electrode has a bus bar and a plurality of electrode fingers. A pair of comb-tooth electrodes are interlaced with each other on the piezoelectric layer. A pair of comb-tooth electrodes are connected to different potentials. By applying an AC voltage to the IDT electrode, a body wave in a thickness shear mode is excited.

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent Document 1: U.S. Patent No. 10491192 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] In the elastic wave device described in Patent Document 1, a through hole is provided in a support body, and a piezoelectric layer is provided on the support body so as to cover the through hole. Therefore, in the laminate of the piezoelectric layer and the support body, the portion of the piezoelectric layer covering the through hole is in a thin film shape.

[0008] The area where adjacent electrode fingers face each other is located in the thin film portion. When this area is set as the intersection area, stress is easily concentrated in the intersection area and between the bus bar. Therefore, when a crack occurs in the thin film portion, the crack sometimes extends between the intersection area and the bus bar. As a result, the electrode fingers of the IDT electrode are easily broken. If the number of broken electrode fingers increases, electrostatic capacitance is sometimes generated in series with the IDT electrode. For this reason, the filter characteristics sometimes change.

[0009] An object of the present invention is to provide an elastic wave device capable of suppressing crack propagation.

[0010] Technical solutions to solve problems

[0011] The elastic wave device of the present invention comprises: a supporting member having a supporting substrate; a piezoelectric layer provided on the supporting member and having a first main surface and a second main surface facing each other; and an IDT electrode provided on at least one of the first main surface and the second main surface of the piezoelectric layer, the IDT electrode having a first bus bar portion and a second bus bar portion facing each other, and a plurality of electrode fingers, the plurality of electrode fingers including at least one first electrode finger having one end connected to the first bus bar portion, and at least one second electrode finger having one end connected to the second bus bar portion, the first electrode finger and the second electrode finger being interlaced with each other, When observed in a direction orthogonal to the direction in which the second electrode finger extends, the area where the adjacent first electrode fingers and the second electrode fingers overlap with each other is an intersection area, and a hollow portion is provided in the supporting member, and the hollow portion overlaps with the intersection area when viewed from above, and at least one of the first bus bar portion and the second bus bar portion has an outer bus bar and at least one protruding electrode, and the outer bus bar does not overlap with the hollow portion when viewed from above, and the at least one protruding electrode extends from the outer bus bar toward the intersection area side and is opposite to the electrode fingers among the multiple electrode fingers that are not connected to the outer bus bar, and the protruding electrode overlaps with the outer peripheral edge of the hollow portion when viewed from above.

[0012] Effects of the Invention

[0013] According to the present invention, an elastic wave device capable of suppressing crack propagation can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic plan view of the elastic wave device according to the first embodiment of the present invention.

[0015] Figure 2 It is along Figure 1 Schematic cross-sectional view of line II in FIG.

[0016] Figure 3 It is a schematic plan view of an elastic wave device according to a comparative example.

[0017] Figure 4 1 is a schematic plan view showing an enlarged portion of an elastic wave device according to a comparative example, and illustrates that a disconnected portion is equivalent to a capacitor portion.

[0018] Figure 5 FIG. 4 is a schematic cross-sectional view of an elastic wave device according to a second embodiment of the present invention, taken along a direction in which electrode fingers extend.

[0019] Figure 6 (a)~ Figure 6(c) is a diagram for explaining a sacrificial layer forming step and an insulating layer forming step in an example of a method for manufacturing an elastic wave device according to the second embodiment of the present invention, and shows a step corresponding to Figure 5 Schematic cross-sectional view of a portion of the cross section shown.

[0020] Figure 7 (a)~ Figure 7 (d) is a diagram for explaining a supporting substrate bonding step, a piezoelectric layer grinding step, an IDT electrode forming step, and a wiring electrode forming step in an example of a method for manufacturing an elastic wave device according to the second embodiment of the present invention, and shows a step corresponding to Figure 5 Schematic cross-sectional view of a portion of the cross section shown.

[0021] Figure 8 (a) and Figure 8 (b) is a schematic front cross-sectional view for explaining a through-hole forming step and a sacrificial layer removing step in an example of a method for manufacturing an elastic wave device according to the second embodiment of the present invention.

[0022] Fig. 9 (a) is a schematic perspective view showing the appearance of an elastic wave device using a thickness shear mode bulk wave, Fig. 9 (b) is a top view showing the electrode structure on the piezoelectric layer.

[0023] Fig.10 It is along Fig. 9 (a) is a cross-sectional view of a portion taken along line AA.

[0024] Fig.11 (a) is a schematic front cross-sectional view for explaining Lamb waves propagating through a piezoelectric film of an elastic wave device. Fig.11 (b) is a schematic front cross-sectional view for explaining a thickness shear mode bulk wave propagating through a piezoelectric film in an elastic wave device.

[0025] Fig.12 It is a diagram showing the amplitude direction of the body wave in the thickness shear mode.

[0026] Fig.13 FIG. 1 is a diagram showing the resonance characteristics of an elastic wave device using bulk waves in a thickness shear mode.

[0027] Fig.14 1 is a diagram showing the relationship between d / p and the relative bandwidth of the resonator when the distance between the centers of adjacent electrodes is defined as p and the thickness of the piezoelectric layer is defined as d.

[0028] Fig.15 This is a top view of an elastic wave device using bulk waves in a thickness shear mode.

[0029] Fig.16 FIG. 4 is a diagram showing the resonance characteristics of an elastic wave device according to a reference example in which spurious emission occurs.

[0030] Fig.17 This is a diagram showing the relationship between the relative bandwidth and the phase rotation amount of the impedance of the spurious signal normalized by 180 degrees, which is the magnitude of the spurious signal.

[0031] Fig.18 It is a graph showing the relationship between d / 2p and the metallization ratio MR.

[0032] Fig.19 This is a diagram showing a map of the relative bandwidth with respect to the Euler angle (0°, θ, ψ) of LiNbO 3 when d / p is made as close to 0 as possible.

[0033] Fig. 20 This is a partially cutaway perspective view for explaining an elastic wave device using Lamb waves. DETAILED DESCRIPTION

[0034] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings to clarify the present invention.

[0035] In addition, it should be noted that each embodiment described in this specification is an exemplary embodiment, and some structures can be replaced or combined between different embodiments.

[0036] Figure 1 It is a schematic plan view of the elastic wave device according to the first embodiment of the present invention. Figure 2 It is along Figure 1 Schematic cross-sectional view of line II in FIG.

[0037] like Figure 1 As shown in FIG. 1 , the elastic wave device 10 includes a piezoelectric substrate 12 and an IDT electrode 11. The piezoelectric substrate 12 is a substrate having piezoelectricity. Figure 2 As shown in FIG. 1 , the piezoelectric substrate 12 includes a support member 13 and a piezoelectric layer 14. In the present embodiment, the support member 13 is composed of only the support substrate. However, the support member 13 may be a laminate including the support substrate.

[0038] The piezoelectric layer 14 has a first principal surface 14a and a second principal surface 14b. The first principal surface 14a and the second principal surface 14b face each other. Of the first principal surface 14a and the second principal surface 14b, the second principal surface 14b is located on the support member 13 side.

[0039] For example, semiconductors such as silicon and ceramics such as alumina can be used as a material of the support substrate of the support member 13. The piezoelectric layer 14 is, for example, a lithium niobate layer such as a LiNbO3 layer or a lithium tantalate layer such as a LiTaO3 layer.

[0040] like Figure 2 As shown, a recess is provided in the support member 13. A piezoelectric layer 14 is provided on the support member 13 so as to block the recess. Thus, a hollow portion is formed. The hollow portion is a cavity 10a. In the present embodiment, the support member 13 and the piezoelectric layer 14 are configured so that a part of the support member 13 and a part of the piezoelectric layer 14 are opposite to each other with the cavity 10a sandwiched therebetween. However, the recess may also be provided in the piezoelectric layer 14. In addition, the cavity 10a may also be a through hole provided in the support member 13.

[0041] The piezoelectric layer 14 includes a thin film portion 14c. Specifically, the thin film portion 14c is a portion of the piezoelectric layer 14 that overlaps with the cavity portion 10a when viewed from above. In this specification, the term "viewed from above" refers to a portion of the piezoelectric layer 14 that overlaps with the cavity portion 10a when viewed from above. Figure 2 The upper direction in FIG. 1 is viewed along the stacking direction of the support member 13 and the piezoelectric layer 14. Figure 2 For example, among the support member 13 and the piezoelectric layer 14 , the piezoelectric layer 14 side is at the upper side.

[0042] The IDT electrode 11 is provided on the first main surface 14a of the piezoelectric layer 14. Figure 1 As shown, the IDT electrode 11 has a pair of bus bar portions and a plurality of electrode fingers. The pair of bus bar portions is specifically a first bus bar portion 26 and a second bus bar portion 27. The first bus bar portion 26 and the second bus bar portion 27 are opposite to each other. The plurality of electrode fingers are specifically a plurality of first electrode fingers 28 and a plurality of second electrode fingers 29. One end of the plurality of first electrode fingers 28 is respectively connected to the first bus bar portion 26. One end of the plurality of second electrode fingers 29 is respectively connected to the second bus bar portion 27. The plurality of first electrode fingers 28 and the plurality of second electrode fingers 29 are interlaced with each other. The IDT electrode 11 may also include a single-layer metal film, or may include a stacked metal film.

[0043] Hereinafter, the direction in which the plurality of first electrode fingers 28 and the plurality of second electrode fingers 29 extend is referred to as the electrode finger extending direction, and the direction orthogonal to the electrode finger extending direction is referred to as the electrode finger orthogonal direction. In addition, the electrode finger orthogonal direction is parallel to the direction in which the adjacent first electrode fingers 28 and second electrode fingers 29 are opposed. When the IDT electrode 11 is observed from the electrode finger orthogonal direction, the region in which the adjacent first electrode fingers 28 and second electrode fingers 29 overlap each other is referred to as the intersection region F. The intersection region F overlaps with the cavity portion 10a in a plan view.

[0044] like Figure 1 as well as Figure 2 As shown in FIG. 1 , the first bus bar portion 26 includes an outer bus bar 26a, an inner bus bar 26b, and a plurality of protruding electrodes 26c. Figure 2In FIG. 1 , the boundaries between the parts of the IDT electrode 11 are shown by dotted lines. Among the outer bus bar 26a and the inner bus bar 26b, the inner bus bar 26b is located on the inner side in the electrode finger extending direction. More specifically, as Figure 1 As shown, of the outer bus bar 26 a and the inner bus bar 26 b , the inner bus bar 26 b is located on the side of the intersection region F. One ends of a plurality of first electrode fingers 28 are connected to the inner bus bar 26 b of the first bus bar portion 26 .

[0045] The outer bus bar 26a does not overlap with the hollow portion 10a in a plan view. On the other hand, a portion of the inner bus bar 26b overlaps with the hollow portion 10a in a plan view. Specifically, the inner bus bar 26b overlaps with the hollow portion 10a in a plan view except for the vicinity of the end portion in the direction orthogonal to the electrode fingers. In other words, the inner bus bar 26b extends to reach a portion that does not overlap with the hollow portion 10a in a plan view.

[0046] The plurality of protruding electrodes 26c extend from the outer bus bar 26a toward the intersection region F and are opposite to the intersection region F. The plurality of protruding electrodes 26c overlap with the outer peripheral edge of the cavity portion 10a in a plan view. Specifically, the plurality of protruding electrodes 26c extend from a portion that does not overlap with the cavity portion 10a in a plan view to a portion that overlaps with the cavity portion 10a. The inner bus bar 26b is located between the plurality of protruding electrodes 26c and the intersection region F. The plurality of protruding electrodes 26c do not contact the inner bus bar 26b. The plurality of protruding electrodes 26c are opposite to the plurality of second electrode fingers 29 across the inner bus bar 26b.

[0047] The first bus bar portion 26 has a plurality of first connection portions 26d and a plurality of second connection portions 26e. The first connection portion 26d is a connection portion in the present invention. The plurality of first connection portions 26d and the plurality of second connection portions 26e connect the inner bus bar 26b and the outer bus bar 26a.

[0048] A plurality of first connecting portions 26d are arranged on the extension lines of the plurality of first electrode fingers 28 connected to the inner bus bar 26b. This structure is equivalent to a structure in which the first electrode finger 28 includes the first connecting portion 26d. In the case where the first electrode finger 28 includes the first connecting portion 26d, the first electrode finger 28 is connected to the outer bus bar 26a at the first connecting portion 26d. On the other hand, the plurality of second connecting portions 26e are not located on the extension lines of the plurality of first electrode fingers 28. The plurality of second connecting portions 26e are located in a portion that does not overlap with the hollow portion 10a when viewed from above. In addition, the second connecting portion 26e is a portion included in the outer bus bar 26a.

[0049] More specifically, in the present embodiment, the first bus bar portion 26 has two second connecting portions 26e. The two second connecting portions 26e connect the two ends of the electrode fingers of the inner bus bar 26b in the orthogonal direction to the outer bus bar 26a. Therefore, the first bus bar portion 26 has a structure in which a plurality of first connecting portions 26d and a plurality of protruding electrodes 26c are provided in a gap portion surrounded by the outer bus bar 26a, the inner bus bar 26b, and the two second connecting portions 26e.

[0050] Similarly, the second bus bar portion 27 also includes an outer bus bar 27a, an inner bus bar 27b, a plurality of protruding electrodes 27c, a plurality of first connecting portions 27d, and a plurality of second connecting portions 27e. The second connecting portion 27e is specifically a portion included in the outer bus bar 27a. The second bus bar portion 27 has a structure in which a plurality of first connecting portions 27d and a plurality of protruding electrodes 27c are provided in a gap portion surrounded by the outer bus bar 27a, the inner bus bar 27b, and the two second connecting portions 27e. One end of a plurality of second electrode fingers 29 is connected to the inner bus bar 27b. The plurality of protruding electrodes 27c are opposite to the plurality of first electrode fingers 28 across the inner bus bar 27b.

[0051] The structure of the second bus bar portion 27 and the second electrode finger 29 is equivalent to the structure in which the second electrode finger 29 includes the first connection portion 27d. When the second electrode finger 29 includes the first connection portion 27d, the second electrode finger 29 is connected to the outer bus bar 27a at the first connection portion 27d.

[0052] In addition, at least one of the first bus bar portion 26 and the second bus bar portion 27 may have at least one protruding electrode. For example, one of the first bus bar portion 26 and the second bus bar portion 27 may be a strip-shaped shape without an outer bus bar and an inner bus bar. However, it is preferred that at least one of the first bus bar portion 26 and the second bus bar portion 27 has a plurality of protruding electrodes. It is more preferred that both the first bus bar portion 26 and the second bus bar portion 27 have a plurality of protruding electrodes.

[0053] The present embodiment is characterized in that the first bus bar portion 26 has a plurality of protruding electrodes 26c, and the plurality of protruding electrodes 26c overlap with the outer peripheral edge of the cavity portion 10a in a plan view. As a result, the portion where stress is concentrated can be moved from the region between the intersection region F and the first bus bar portion 26 to the central side of the thin film portion 14c, and the stress itself can also be reduced. In addition, since the first bus bar portion 26 has a plurality of protruding electrodes 26c, stress can also be dispersed. As a result, the expansion of cracks along the first bus bar portion 26 can be suppressed. Therefore, the disconnection of the first electrode finger 28 can be suppressed, and the degradation of the electrical characteristics of the elastic wave device 10 can be suppressed.

[0054] The above-mentioned effects of the first embodiment will be described in more detail with reference to comparative examples. Figure 3 In the comparative example shown, the first bus bar portion 106 and the second bus bar portion 107 are strip-shaped without an outer bus bar and an inner bus bar. In the comparative example, a crack G is generated in the thin film portion 14c of the piezoelectric layer 14. The crack G is generated near the first bus bar portion 106. As described above, stress is easily concentrated between the intersection area and the first bus bar portion 106. Therefore, the crack G extends along the first bus bar portion 106. As a result, a plurality of first electrode fingers 28 are cut.

[0055] As Figure 4 As shown in the enlarged view, if the first electrode finger 28 is disconnected, a portion where the electrodes face each other will be generated. Figure 4 As schematically shown in , this portion is equivalent to a capacitor connected in series to IDT electrode 111. Therefore, the electrical characteristics of the elastic wave device may be degraded.

[0056] In contrast, Figure 1 In the first embodiment shown, the first bus bar portion 26 has a plurality of protruding electrodes 26c. As described above, the disconnection of the first electrode finger 28 can be suppressed, and the degradation of the electrical characteristics of the elastic wave device 10 can be suppressed. In addition, the second bus bar portion 27 also has a plurality of protruding electrodes 27c. As a result, the disconnection of the second electrode finger 29 can also be suppressed. Therefore, the degradation of the electrical characteristics of the elastic wave device 10 can be more reliably suppressed.

[0057] Hereinafter, further details of the structure of the first embodiment will be described.

[0058] The elastic wave device 10 of the first embodiment is an elastic wave resonator configured to utilize a thickness shear mode bulk wave. More specifically, in the elastic wave device 10, when the thickness of the piezoelectric layer 14 is d and the center-to-center distance between adjacent electrode fingers is p, d / p is equal to or less than 0.5. Thus, a thickness shear mode bulk wave can be appropriately excited.

[0059] In addition, when the IDT electrode 11 is observed from the direction orthogonal to the electrode fingers, the region where adjacent electrode fingers overlap each other and the region between the centers of adjacent electrode fingers is the excitation region. That is, in the first embodiment, the intersection region F includes a plurality of excitation regions. The intersection region F and each excitation region are regions of the piezoelectric layer 14 defined based on the structure of the IDT electrode 11. In each excitation region, a body wave of a thickness shear mode can be excited.

[0060] On the other hand, the elastic wave device 10 may be configured to utilize plate waves. In this case, the exciting region is the intersection region F.

[0061] Figure 2 The cavity 10a shown is a sound reflecting portion in the present invention. The sound reflecting portion can effectively confine the energy of the elastic wave to the piezoelectric layer 14 side.

[0062] The wiring electrode 24 is connected to the first bus bar portion 26. More specifically, the wiring electrode 24 is provided over the outer bus bar 26a of the first bus bar portion 26 and the piezoelectric layer 14. The wiring electrode 24 does not reach the boundary between the outer bus bar 26a and the plurality of protruding electrodes 26c. The thickness of the wiring electrode 24 is thicker than the thickness of the first bus bar portion 26. Thus, the resistance of the wiring electrode 24 is easily reduced.

[0063] Likewise, wiring electrode 25 is connected to second bus bar portion 27 . Elastic wave device 10 can be used in, for example, a filter device. In this case, IDT electrode 11 is connected to, for example, other elements in the filter device, a ground potential, etc., via wiring electrode 24 and wiring electrode 25 .

[0064] Back to Figure 1 The piezoelectric layer 14′ is provided with a plurality of through holes 14 d. The plurality of through holes 14 d are used when forming the cavity 10 a. Specifically, when manufacturing the elastic wave device 10 , the sacrificial layer is removed by etching, thereby forming the cavity 10 a. At this time, the sacrificial layer is removed by using the through holes 14 d.

[0065] The number of locations where through-holes 14d are provided in piezoelectric layer 14 is not particularly limited. Depending on the method of manufacturing elastic wave device 10, at least one through-hole 14d may be provided in piezoelectric layer 14. Alternatively, through-holes 14d may not necessarily be provided in piezoelectric layer 14.

[0066] In addition, the first bus bar portion 26 may not necessarily have the second connection portion 26e. In this case, the outer bus bar 26a and the inner bus bar 26b can be appropriately connected by the plurality of first connection portions 26d. Thus, the resistance of the first bus bar portion 26 can be appropriately reduced.

[0067] However, it is preferred that the first bus bar portion 26 has at least one second connection portion 26e. Figure 2 The portion supported by the support member 13 shown is configured such that the outer bus bar 26a and the inner bus bar 26b are connected. This can improve the strength of the first bus bar portion 26.

[0068] like Figure 1 As shown in FIG. 1 , the plurality of first connecting portions 26d are provided on extension lines of the plurality of first electrode fingers 28. In addition, the arrangement of the plurality of first connecting portions 26d is not limited to the above.

[0069] The first bus bar portion 26 may not necessarily have the inner bus bar 26b. In this case, the first bus bar portion 26 does not have the plurality of first connecting portions 26d and the plurality of second connecting portions 26e. However, it is preferred that the first bus bar portion 26 has the inner bus bar 26b. This can suppress the influence of the plurality of protruding electrodes 26c on the electrical characteristics of the elastic wave device 10. These preferred structures in the first bus bar portion 26 are also the same in the second bus bar portion 27.

[0070] The plurality of electrode fingers of the IDT electrode 11 may include at least one first electrode finger 28 and at least one second electrode finger 29. That is, the plurality of electrode fingers may be only one pair of the first electrode finger 28 and the second electrode finger 29. In this case, in the present specification, when the first electrode finger 28 and the second electrode finger 29 are opposed to each other in the electrode finger orthogonal direction, the first electrode finger 28 and the second electrode finger 29 are also assumed to be interlaced with each other.

[0071] A dielectric film may also be provided on the first main surface 14a of the piezoelectric layer 14 so as to cover the IDT electrode 11. Thus, the IDT electrode 11 is protected by the dielectric film, so that the IDT electrode 11 is not easily damaged. As the material of the dielectric film, for example, silicon oxide, silicon nitride or silicon oxynitride can be used. In addition, the material of the dielectric film is not limited to the above. This structure can also be applied to structures of other modes of the present invention.

[0072] In the first embodiment, the IDT electrode 11 is provided on the first principal surface 14a of the piezoelectric layer 14. However, the IDT electrode 11 may be provided on at least one of the first principal surface 14a and the second principal surface 14b of the piezoelectric layer 14. When the IDT electrode 11 is provided on the second principal surface 14b, a portion of each protruding electrode 26c of the first bus bar portion 26, a portion of the inner bus bar 26b, and the outer bus bar 26a are in contact with the support member 13. A portion of each first connecting portion 26d and each second connecting portion 26e of the first bus bar portion 26 are also in contact with the support member 13. The same is true for the second bus bar portion 27.

[0073] When the IDT electrode 11 is provided on the second main surface 14 b , the propagation of cracks along each bus bar portion can be suppressed as in the first embodiment, thereby suppressing disconnection of the plurality of electrode fingers and suppressing degradation of the electrical characteristics of the elastic wave device.

[0074] Figure 5 FIG. 4 is a schematic cross-sectional view of an elastic wave device according to a second embodiment, taken along a direction in which electrode fingers extend.

[0075] This embodiment differs from the first embodiment in that a support member 33 includes a support substrate 36 and an insulating layer 35, and a cavity 30a is provided in the insulating layer 35. Except for the above points, the elastic wave device 30 of this embodiment has the same structure as the elastic wave device 10 of the first embodiment.

[0076] An insulating layer 35 is provided on the support substrate 36. The piezoelectric layer 14 is provided on the insulating layer 35. As a material of the insulating layer 35, an appropriate dielectric such as silicon oxide or tantalum oxide can be used.

[0077] like Figure 5 As shown, a recess is provided in the insulating layer 35. A piezoelectric layer 14 is provided on the insulating layer 35 so as to block the recess. Thus, a hollow portion is formed. The hollow portion is a cavity 30a. In the present embodiment, the supporting member 33 and the piezoelectric layer 14 are configured so that a part of the supporting member 33 and a part of the piezoelectric layer 14 are opposed to each other with the cavity 30a sandwiched therebetween. However, the recess in the supporting member 33 may also be provided throughout the insulating layer 35 and the supporting substrate 36. Alternatively, it may be that only the recess provided in the supporting substrate 36 is blocked by the insulating layer 35. In addition, the cavity 30a may also be a through hole provided in the supporting member 33.

[0078] In the present embodiment, the IDT electrode 11 is also provided in the same manner as in the first embodiment. Therefore, the first bus bar portion 26 has a plurality of protruding electrodes 26c, and the plurality of protruding electrodes 26c overlap with the outer peripheral edge of the cavity portion 30a in a plan view. As a result, the portion where stress is concentrated can be moved from the intersection area and the area between the first bus bar portion 26 to the central side of the thin film portion 14c, and the stress itself can also be reduced. In addition, since the first bus bar portion 26 has a plurality of protruding electrodes 26c, stress can also be dispersed. As a result, the expansion of cracks along the first bus bar portion 26 can be suppressed. Therefore, the reference can be suppressed. Figure 1 The disconnection of first electrode fingers 28 shown can suppress degradation of the electrical characteristics of elastic wave device 30 .

[0079] Second bus bar portion 27 is also configured similarly to first bus bar portion 26. Thus, it is possible to suppress the propagation of cracks along second bus bar portion 27. Therefore, it is possible to more reliably suppress the degradation of the electrical characteristics of elastic wave device 30.

[0080] An example of a method for manufacturing elastic wave device 30 according to the present embodiment will be described below.

[0081] Figure 6 (a)~ Figure 6 (c) is a diagram for explaining a sacrificial layer forming step and an insulating layer forming step in an example of a method for manufacturing an elastic wave device according to the second embodiment, and shows a step corresponding to Figure 5Schematic cross-sectional view of a portion of the cross section shown. Figure 7 (a)~ Figure 7 (d) is a diagram for explaining a supporting substrate bonding step, a piezoelectric layer grinding step, an IDT electrode forming step, and a wiring electrode forming step in an example of a method for manufacturing an elastic wave device according to the second embodiment, and shows a step corresponding to Figure 5 Schematic cross-sectional view of a portion of the cross section shown. Figure 8 (a) and Figure 8 (b) is a schematic front cross-sectional view for explaining a through-hole forming step and a sacrificial layer removing step in an example of the method for manufacturing the elastic wave device according to the second embodiment.

[0082] like Figure 6 As shown in (a), a piezoelectric substrate 44 is prepared. The piezoelectric substrate 44 includes a piezoelectric layer in the present invention. Next, a sacrificial layer 47A is formed on the piezoelectric substrate 44. Next, the sacrificial layer 47A is appropriately patterned by etching or the like. Thus, as shown in FIG. Figure 6 As shown in (b), a sacrificial layer 47 is formed. As a material of the sacrificial layer 47, for example, ZnO, SiO 2、 Cu or resin, etc.

[0083] Then, if Figure 6 As shown in (c), the insulating layer 35 is formed so as to cover the sacrificial layer 47. The insulating layer 35 can be formed by, for example, sputtering or vacuum deposition.

[0084] Then, if Figure 7 As shown in (a) of FIG. 3 , the support substrate 36 and the insulating layer 35 are bonded together. Alternatively, for example, an insulating layer may be separately formed on the support substrate 36 , and then the insulating layer and the insulating layer 35 covering the sacrificial layer 47 may be bonded together.

[0085] Next, the thickness of the piezoelectric substrate 44 is reduced by grinding or polishing the main surface side of the piezoelectric substrate 44 where the insulating layer 35 is not provided. The thickness of the piezoelectric substrate 44 can be adjusted by, for example, grinding, CMP (Chemical Mechanical Polishing), ion slicing, or etching. Figure 7 As shown in (b), the piezoelectric layer 14 is obtained.

[0086] Then, if Figure 7 As shown in (c), the IDT electrode 11 is formed. The IDT electrode 11 can be formed by, for example, sputtering or vacuum deposition.

[0087] Then, if Figure 7As shown in (d), the wiring electrode 24 is formed on the outer bus bar 26a of the first bus bar portion 26 and on the piezoelectric layer 14. Similarly, the wiring electrode 25 is formed on the outer bus bar 27a of the second bus bar portion 27 and on the piezoelectric layer 14. The wiring electrode 24 and the wiring electrode 25 can be formed by, for example, sputtering or vacuum deposition.

[0088] Then, if Figure 8 As shown in (a), a plurality of through holes 14d are formed in the piezoelectric layer 14. More specifically, a plurality of through holes 14d are formed in the piezoelectric layer 14 so as to reach the sacrificial layer 47. The through holes 14d can be formed, for example, by RIE (Reactive Ion Etching) method or the like. Next, the sacrificial layer 47 is removed through the through holes 14d. More specifically, the sacrificial layer 47 in the concave portion of the insulating layer 35 is removed by allowing an etching solution to flow through the through holes 14d. Thus, as shown in FIG. Figure 8 As shown in (b), a cavity 30a is formed.

[0089] According to the above, we get Figure 5 The elastic wave device 30 shown in FIG. 1 is shown in FIG. 1 . The above-described manufacturing method is an example, and the elastic wave device 30 can also be obtained by other methods.

[0090] The following describes the details of the thickness shear mode using an example of a conventional IDT electrode. In addition, the "electrode" in the IDT electrode described below corresponds to the electrode finger in the present invention. The support member in the following example corresponds to the support substrate in the present invention.

[0091] Fig. 9 (a) is a schematic perspective view showing the appearance of an elastic wave device using a thickness shear mode bulk wave, Fig. 9 (b) is a top view showing the electrode structure on the piezoelectric layer. Fig.10 It is along Fig. 9 (a) is a cross-sectional view of a portion taken along line AA.

[0092] The elastic wave device 1 has a piezoelectric layer 2 including LiNbO3. The piezoelectric layer 2 may also be a piezoelectric layer including LiTaO3. The cutting angle of LiNbO3 and LiTaO3 is Z-cut, but may also be a rotated Y-cut or X-cut. The thickness of the piezoelectric layer 2 is not particularly limited, but in order to effectively excite the thickness shear mode, it is preferably greater than 40 nm and less than 1000 nm, and more preferably greater than 50 nm and less than 1000 nm. The piezoelectric layer 2 has a first principal surface 2a and a second principal surface 2b facing each other. An electrode 3 and an electrode 4 are provided on the first principal surface 2a. Here, electrode 3 is an example of a "first electrode", and electrode 4 is an example of a "second electrode". In Fig. 9 (a) and Fig. 9 In (b), the plurality of electrodes 3 are a plurality of first electrode fingers connected to the first bus bar portion 5. The plurality of electrodes 4 are a plurality of second electrode fingers connected to the second bus bar portion 6. The plurality of electrodes 3 and the plurality of electrodes 4 are interlaced with each other. The electrodes 3 and the electrodes 4 have a rectangular shape and a length direction. In a direction orthogonal to the length direction, the electrode 3 and the adjacent electrode 4 are opposed to each other. The length directions of the electrodes 3 and 4 and the directions orthogonal to the length directions of the electrodes 3 and 4 are directions intersecting with the thickness direction of the piezoelectric layer 2. Therefore, it can also be said that the electrode 3 and the adjacent electrode 4 are opposed to each other in a direction intersecting with the thickness direction of the piezoelectric layer 2. In addition, the length directions of the electrodes 3 and 4 can also be orthogonal to the length directions of the electrodes 3 and 4. Fig. 9 (a) and Fig. 9 The direction perpendicular to the length direction of electrodes 3 and 4 shown in (b) is reversed. Fig. 9 (a) and Fig. 9 In (b), the electrodes 3 and 4 may extend in the direction in which the first bus bar portion 5 and the second bus bar portion 6 extend. In this case, the first bus bar portion 5 and the second bus bar portion 6 are located at Fig. 9 (a) and Fig. 9 (b) becomes extended in the direction in which electrodes 3 and 4 extend. Moreover, a pair of structures in which an electrode 3 connected to one potential and an electrode 4 connected to another potential are adjacent are provided with multiple pairs in a direction orthogonal to the length direction of the electrodes 3 and 4. Here, the so-called electrode 3 and electrode 4 are adjacent refers to the situation in which the electrode 3 and the electrode 4 are arranged at intervals, rather than the situation in which the electrode 3 and the electrode 4 are arranged in direct contact. In addition, when the electrode 3 and the electrode 4 are adjacent, no electrode connected to the signal (hot) electrode and the ground electrode, including other electrodes 3 and 4, is arranged between the electrode 3 and the electrode 4. The number of pairs does not need to be an integer pair, and can also be 1.5 pairs, 2.5 pairs, etc. The center-to-center distance between the electrodes 3 and 4, that is, the spacing, is preferably in the range of 1 μm or more and 10 μm or less. In addition, the width of the electrodes 3 and 4, that is, the size of the opposing direction of the electrodes 3 and 4, is preferably in the range of 50 nm or more and 1000 nm or less, and more preferably in the range of 150 nm or more and 1000 nm or less. The center-to-center distance between electrodes 3 and 4 is the distance connecting the center of the dimension (width dimension) of electrode 3 in a direction perpendicular to the length direction of electrode 3 and the center of the dimension (width dimension) of electrode 4 in a direction perpendicular to the length direction of electrode 4.

[0093] In addition, in the elastic wave device 1, a Z-cut piezoelectric layer is used, so the direction orthogonal to the length direction of the electrodes 3 and 4 is a direction orthogonal to the polarization direction of the piezoelectric layer 2. When a piezoelectric body with another cutting angle is used as the piezoelectric layer 2, it is not limited to this. Here, the so-called "orthogonal" is not limited to the case of being strictly orthogonal, and can also be approximately orthogonal (the angle formed by the direction orthogonal to the length direction of the electrodes 3 and 4 and the polarization direction is, for example, within the range of 90°±10°).

[0094] A support member 8 is stacked on the second main surface 2b side of the piezoelectric layer 2 via an insulating layer 7. The insulating layer 7 and the support member 8 have a frame-like shape. Fig.10 As shown, there are through holes 7a and 8a. Thus, a cavity 9 is formed. The cavity 9 is provided so as not to hinder the vibration of the excitation region C of the piezoelectric layer 2. Therefore, the support member 8 is stacked on the second main surface 2b via the insulating layer 7 at a position that does not overlap with the portion where at least one pair of electrodes 3 and 4 is provided. In addition, the insulating layer 7 may not be provided. Therefore, the support member 8 can be directly or indirectly stacked on the second main surface 2b of the piezoelectric layer 2.

[0095] The insulating layer 7 includes silicon oxide. However, in addition to silicon oxide, suitable insulating materials such as silicon nitride oxide and alumina can also be used. The supporting member 8 includes Si. The surface orientation of the surface of Si on the side of the piezoelectric layer 2 can also be (100), (110), or (111). It is preferred that the Si constituting the supporting member 8 has a high resistance with a resistivity of more than 4 kΩcm. However, the supporting member 8 can also be composed of suitable insulating materials or semiconductor materials.

[0096] As the material of the supporting member 8, for example, piezoelectrics such as aluminum oxide, lithium tantalate, lithium niobate, and quartz, various ceramics such as alumina, magnesium oxide, sapphire, silicon nitride, aluminum nitride, silicon carbide, zirconium oxide, cordierite, mullite, steatite, and forsterite, dielectrics such as diamond and glass, and semiconductors such as gallium nitride can be used.

[0097] The plurality of electrodes 3, 4 and the first bus bar portion 5 and the second bus bar portion 6 are made of a suitable metal or alloy such as Al or an AlCu alloy. In the elastic wave device 1, the electrodes 3, 4 and the first bus bar portion 5 and the second bus bar portion 6 have a structure in which an Al film is stacked on a Ti film. Alternatively, a bonding layer other than a Ti film may be used.

[0098] During driving, an AC voltage is applied between the plurality of electrodes 3 and the plurality of electrodes 4. More specifically, an AC voltage is applied between the first bus bar portion 5 and the second bus bar portion 6. Thus, it is possible to obtain a resonance characteristic of a body wave utilizing a thickness shear mode excited in the piezoelectric layer 2. In addition, in the elastic wave device 1, when the thickness of the piezoelectric layer 2 is set to d and the center-to-center distance between any adjacent electrodes 3 and 4 in the plurality of pairs of electrodes 3 and 4 is set to p, d / p is set to be less than 0.5. Therefore, the body wave of the thickness shear mode can be effectively excited, and a good resonance characteristic can be obtained. More preferably, d / p is less than 0.24, in which case, a better resonance characteristic can be obtained.

[0099] In the elastic wave device 1, the above structure is provided, so even if the number of pairs of electrodes 3 and 4 is reduced to achieve miniaturization, the Q value is not likely to decrease. This is because even if the number of electrode fingers in the reflectors on both sides is reduced, the propagation loss is small. In addition, the number of electrode fingers can be reduced because the body wave of the thickness shear mode is utilized. Fig.11 (a) and Fig.11 (b) describes the difference between the Lamb wave used in the elastic wave device and the body wave of the thickness shear mode.

[0100] Fig.11 (a) is a schematic front cross-sectional view for explaining the Lamb wave propagating in the piezoelectric film of the elastic wave device described in the Japanese Patent Gazette: Japanese Patent Gazette No. 2012-257019. Here, the wave propagates in the piezoelectric film 201 as shown by the arrow. Here, in the piezoelectric film 201, the first main surface 201a and the second main surface 201b are opposite to each other, and the thickness direction connecting the first main surface 201a and the second main surface 201b is the Z direction. The X direction is the direction in which the electrode fingers of the IDT electrode are arranged. Fig.11 As shown in (a), for Lamb waves, the waves propagate in the X direction as shown in the figure. Since it is a plate wave, the piezoelectric film 201 vibrates as a whole, but since the waves propagate in the X direction, reflectors are arranged on both sides to obtain resonance characteristics. Therefore, wave propagation loss occurs, and when miniaturization is achieved, that is, when the number of pairs of electrode fingers is reduced, the Q value decreases.

[0101] In contrast, Fig.11As shown in (b), in the elastic wave device 1, the vibration displacement is in the thickness shear direction, so the wave propagates and resonates almost in the direction connecting the first main surface 2a and the second main surface 2b of the piezoelectric layer 2, that is, the Z direction. That is, the X-direction component of the wave is significantly smaller than the Z-direction component. Moreover, since the resonance characteristic is obtained by the propagation of the wave in the Z direction, it is not easy to generate propagation loss even if the number of electrode fingers of the reflector is reduced. Moreover, even if the number of pairs of electrode pairs including electrodes 3 and 4 is reduced to promote miniaturization, it is not easy to cause a decrease in the Q value.

[0102] In addition, if Fig.12 As shown in FIG. 1 , the amplitude directions of the body waves in the thickness shear mode become opposite in the first region 451 included in the excitation region C of the piezoelectric layer 2 and in the second region 452 included in the excitation region C. Fig.12 , a body wave is schematically shown when a voltage is applied between electrode 3 and electrode 4 so that electrode 4 has a higher potential than electrode 3. The first region 451 is a region between the imaginary plane VP1 and the first principal surface 2a in the excitation region C, wherein the imaginary plane VP1 is orthogonal to the thickness direction of the piezoelectric layer 2 and divides the piezoelectric layer 2 into two parts. The second region 452 is a region between the imaginary plane VP1 and the second principal surface 2b in the excitation region C.

[0103] As described above, in elastic wave device 1 , at least one pair of electrodes including electrode 3 and electrode 4 is disposed. However, since waves are not propagated in the X direction, there is no need to have a plurality of pairs of electrodes including electrodes 3 and 4 . In other words, at least one pair of electrodes is sufficient.

[0104] For example, the electrode 3 is an electrode connected to the signal potential, and the electrode 4 is an electrode connected to the ground potential. However, the electrode 3 may be connected to the ground potential, and the electrode 4 may be connected to the signal potential. In the elastic wave device 1, at least one pair of electrodes is an electrode connected to the signal potential or an electrode connected to the ground potential as described above, and no floating electrode is provided.

[0105] Fig.13 It is shown Fig.10 The resonance characteristics of the elastic wave device are shown in FIG. 1 . The design parameters of the elastic wave device 1 for obtaining the resonance characteristics are as follows.

[0106] Piezoelectric layer 2: LiNbO3 with Euler angles (0°, 0°, 90°), thickness = 400nm.

[0107] When observed in a direction orthogonal to the length direction of electrode 3 and electrode 4, the length of the overlapping area of ​​electrode 3 and electrode 4, i.e., the excitation area C, is 40 μm, the number of pairs of electrodes including electrodes 3 and 4 is 21 pairs, the center distance between electrodes is 3 μm, the width of electrodes 3 and 4 is 500 nm, and d / p is 0.133.

[0108] Insulating layer 7: a silicon oxide film having a thickness of 1 μm.

[0109] Supporting member 8: Si.

[0110] The length of the excitation region C refers to the dimension of the excitation region C along the length direction of the electrodes 3 and 4 .

[0111] In elastic wave device 1 , the inter-electrode distances of the electrode pairs including electrodes 3 and 4 are set equal in all pairs. That is, electrodes 3 and electrodes 4 are arranged at equal intervals.

[0112] according to Fig.13 It is clear that, despite the absence of a reflector, a good resonance characteristic with a relative bandwidth of 12.5% ​​can be obtained.

[0113] When the thickness of the piezoelectric layer 2 is d and the center-to-center distance between the electrodes 3 and 4 is p, as described above, in the elastic wave device 1, d / p is 0.5 or less, and more preferably 0.24 or less. Fig.14 This is explained.

[0114] and got Fig.13 A plurality of elastic wave devices are obtained by changing d / p in the same manner as the elastic wave device having the resonance characteristics shown. Fig.14 2 is a diagram showing the relationship between d / p and the relative bandwidth of the elastic wave device as a resonator.

[0115] according to Fig.14 It is clear that if d / p>0.5, even if d / p is adjusted, the relative bandwidth is less than 5%. In contrast, when d / p≤0.5, if d / p is changed within this range, the relative bandwidth can be made greater than 5%, that is, a resonator with a high coupling coefficient can be constructed. In addition, when d / p is less than 0.24, the relative bandwidth can be increased to more than 7%. In addition, if d / p is adjusted within this range, a resonator with a wider relative bandwidth can be obtained, and a resonator with a higher coupling coefficient can be realized. Therefore, it can be seen that by making d / p less than 0.5, a resonator with a high coupling coefficient that utilizes the body wave of the thickness shear mode mentioned above can be constructed.

[0116] Fig.151 is a top view of an elastic wave device using a thickness shear mode bulk wave. In the elastic wave device 80, a pair of electrodes including an electrode 3 and an electrode 4 are provided on the first principal surface 2a of the piezoelectric layer 2. Fig.15 K in is the crossing width. As described above, in the elastic wave device of the present invention, the number of pairs of electrodes may be 1 pair. In this case, as long as the above d / p is 0.5 or less, a thickness shear mode body wave can be effectively excited.

[0117] In the elastic wave device 1, it is preferable that the metallization ratio MR of the adjacent electrodes 3 and 4 in the region where the adjacent electrodes 3 and 4 overlap when viewed in the opposite direction, i.e., the excitation region C, satisfies MR≤1.75(d / p)+0.075. In this case, the stray emission can be effectively reduced. Fig.16 as well as Fig.17 This is explained. Fig.16 : is a reference diagram showing an example of the resonance characteristics of the elastic wave device 1. Spurious signals indicated by arrow B appear between the resonance frequency and the antiresonance frequency. In addition, d / p=0.08 is assumed, and the Euler angles of LiNbO3 are assumed to be (0°, 0°, 90°). In addition, the metallization ratio MR is assumed to be 0.35.

[0118] Reference Fig. 9 (b) will explain the metallization ratio MR. Fig. 9 In the electrode structure of (b), when focusing on a pair of electrodes 3 and 4, it is assumed that only the pair of electrodes 3 and 4 are provided. In this case, the portion surrounded by the single-point chain line becomes the excitation region C. The excitation region C is the region where the electrode 3 overlaps with the electrode 4, the region where the electrode 4 overlaps with the electrode 3, and the region between the electrode 3 and the electrode 4 when the electrode 3 and the electrode 4 are observed in the direction perpendicular to the longitudinal direction of the electrodes 3 and 4, that is, in the opposite direction. And, the area of ​​the electrodes 3 and 4 in the excitation region C relative to the area of ​​the excitation region C is the metallization ratio MR. That is, the metallization ratio MR is the ratio of the area of ​​the metallized portion to the area of ​​the excitation region C.

[0119] When a plurality of pairs of electrodes are provided, the ratio of the total area of ​​the metallized portions included in all the excitation regions to the area of ​​the excitation regions may be defined as MR.

[0120] Fig.17 The graph shows the relationship between the relative bandwidth and the phase rotation amount of the impedance of the spurious signal normalized by 180 degrees when a large number of spurious wave resonators are configured in the manner of the spurious wave device 1. In addition, the relative bandwidth was adjusted by making various changes to the film thickness of the piezoelectric layer and the size of the electrode. Fig.17 These are the results obtained when a piezoelectric layer including Z-cut LiNbO 3 is used; however, the same tendency is observed even when a piezoelectric layer having other cut angles is used.

[0121] exist Fig.17 In the area surrounded by the ellipse J in , the spurious signal becomes larger and becomes 1.0. Fig.17 It is clear that if the relative bandwidth exceeds 0.17, that is, if it exceeds 17%, even if the parameters constituting the relative bandwidth are changed, large spurious with a spurious level of 1 or more will appear in the passband. Fig.16 As shown in the resonance characteristics, large spurious signals indicated by arrow B appear in the frequency band. Therefore, it is preferable that the relative bandwidth is 17% or less. In this case, the spurious signals can be reduced by adjusting the film thickness of the piezoelectric layer 2, the dimensions of the electrodes 3 and 4, and the like.

[0122] Fig.18 : is a graph showing the relationship between d / 2p, metallization ratio MR, and relative bandwidth. In the above-mentioned elastic wave device, various elastic wave devices having different d / 2p and MR were constructed, and the relative bandwidth was measured. Fig.18 The hatched portion on the right side of the dotted line D is an area where the relative bandwidth is less than 17%. The boundary between the hatched area and the unhatched area can be represented by MR=3.5(d / 2p)+0.075. That is, MR=1.75(d / p)+0.075. Therefore, MR≤1.75(d / p)+0.075 is preferred. In this case, it is easy to make the relative bandwidth less than 17%. More preferably, Fig.18 The area on the right side of MR=3.5(d / 2p)+0.05 indicated by the dashed line D1 in FIG. 1. That is, if MR≤1.75(d / p)+0.05, the relative bandwidth can be reliably made 17% or less.

[0123] Fig.19 This is a diagram showing a map of the relative bandwidth with respect to the Euler angle (0°, θ, ψ) of LiNbO 3 when d / p is made as close to 0 as possible. Fig.19 The hatched portion of is a region where a relative bandwidth of at least 5% can be obtained. When the range of this region is approximated, it becomes a range represented by the following equations (1), (2), and (3).

[0124] (0°±10°, 0°~20°, arbitrary ψ) …Formula (1)

[0125] (0°±10°, 20°~80°, 0°~60° (1-(θ-50) 2 / 900) 1 / 2) or (0°±10°, 20°~80°, [180°-60° (1-(θ-50) 2 / 900) 1 / 2 ]~180°) …Formula (2)

[0126] (0°±10°, [180°-30°(1-(ψ-90) 2 / 8100) 1 / 2 ]~180°, any ψ) …Formula (3)

[0127] Therefore, in the case of the Euler angle range of the above-mentioned formula (1), formula (2) or formula (3), the relative bandwidth can be made sufficiently wide, which is preferable. The same is true when the piezoelectric layer 2 is a lithium tantalate layer.

[0128] Fig. 20 This is a partially cutaway perspective view for explaining an elastic wave device using Lamb waves.

[0129] The elastic wave device 81 has a supporting substrate 82. The supporting substrate 82 is provided with a recessed portion whose upper surface is open. A piezoelectric layer 83 is stacked on the supporting substrate 82. Thus, a cavity 9 is formed. An IDT electrode 84 is provided on the piezoelectric layer 83 above the cavity 9. Reflectors 85 and 86 are provided on both sides of the IDT electrode 84 in the direction of propagation of elastic waves. Fig. 20 , the outer periphery of the cavity 9 is shown by a dotted line. Here, the IDT electrode 84 has a first bus bar portion 84a, a second bus bar portion 84b, and a plurality of first electrode fingers 84c and a plurality of second electrode fingers 84d. The plurality of first electrode fingers 84c are connected to the first bus bar portion 84a. The plurality of second electrode fingers 84d are connected to the second bus bar portion 84b. The plurality of first electrode fingers 84c and the plurality of second electrode fingers 84d are interlaced with each other.

[0130] In the elastic wave device 81, Lamb waves as plate waves can be excited by applying an alternating electric field to the IDT electrode 84 on the cavity 9. Furthermore, since the reflectors 85 and 86 are provided on both sides, resonance characteristics based on the Lamb waves can be obtained.

[0131] As described above, the elastic wave device of the present invention may be an elastic wave device using plate waves. Fig. 20 In the example shown, the Figure 2 The first principal surface 14a of the piezoelectric layer 14 shown in the figure is provided with an IDT electrode 84, a reflector 85, and a reflector 86. When the elastic wave device of the present invention uses plate waves, the first principal surface 14a or the second principal surface 14b of the piezoelectric layer 14 in the elastic wave device of the first embodiment or the second embodiment is provided with an IDT electrode 84, a reflector 85, and a reflector 86. Fig. 20The reflector 85 and the reflector 86 shown are sufficient.

[0132] In the elastic wave device of the first embodiment or the second embodiment using the body wave in the thickness shear mode, as described above, d / p is preferably less than 0.5, and more preferably less than 0.24. Thus, a better resonance characteristic can be obtained. Furthermore, in the excitation region of the elastic wave device of the first embodiment or the second embodiment using the body wave in the thickness shear mode, as described above, MR ≤ 1.75 (d / p) + 0.075 is preferably satisfied. In this case, spurious emission can be suppressed more reliably.

[0133] The piezoelectric layer in the elastic wave device of the first embodiment or the second embodiment using the thickness shear mode body wave is preferably a lithium niobate layer or a lithium tantalate layer. Furthermore, the Euler angles (φ, θ, ψ) of the lithium niobate or lithium tantalate constituting the piezoelectric layer are preferably within the range of the above-mentioned formula (1), formula (2) or formula (3). In this case, the relative bandwidth can be made sufficiently wide.

[0134] Description of Reference Numerals

[0135] 1…Elastic wave device

[0136] 2…Piezoelectric layer

[0137] 2a, 2b...1st main surface, 2nd main surface

[0138] 3, 4…Electrode

[0139] 5, 6…1st bus bar section, 2nd bus bar section

[0140] 7…Insulation layer

[0141] 7a…Through hole

[0142] 8…Supporting member

[0143] 8a…Through hole

[0144] 9…Hollow

[0145] 10…Elastic wave device

[0146] 10a…Cavity

[0147] 11…IDT electrode

[0148] 12…Piezoelectric substrate

[0149] 13…Supporting member

[0150] 14…Piezoelectric layer

[0151] 14a, 14b…1st main surface, 2nd main surface

[0152] 14c…Thin Film Department

[0153] 14d…Through hole

[0154] 24, 25…Wiring electrodes

[0155] 26, 27 ... first bus bar portion, second bus bar portion

[0156] 26a, 27a…Outer busbars

[0157] 26b, 27b…Inner busbar

[0158] 26c, 27c ... protruding electrodes

[0159] 26d, 27d…1st connection part

[0160] 26e, 27e…Second connection part

[0161] 28, 29…1st electrode finger, 2nd electrode finger

[0162] 30…Elastic wave device

[0163] 30a…Cavity

[0164] 33…Supporting member

[0165] 35…Insulation layer

[0166] 36…Support base plate

[0167] 44…Piezoelectric substrate

[0168] 47, 47A…Sacrificial layer

[0169] 80, 81…Elastic wave device

[0170] 82…Support base plate

[0171] 83…Piezoelectric layer

[0172] 84…IDT electrode

[0173] 84a, 84b ... first bus bar portion, second bus bar portion

[0174] 84c, 84d ... first electrode finger, second electrode finger

[0175] 85, 86…Reflector

[0176] 106, 107 ... first bus bar portion, second bus bar portion

[0177] 111…IDT electrode

[0178] 201…Piezoelectric film

[0179] 201a, 201b…1st main surface, 2nd main surface

[0180] 451, 452…1st area, 2nd area

[0181] C…Incentive Area

[0182] F…Intersection area

[0183] VP1…imaginary plane.

Claims

1. An elastic wave device comprising: A support member having a support substrate; a piezoelectric layer provided on the supporting member and having a first main surface and a second main surface facing each other; and an IDT electrode provided on at least one of the first main surface and the second main surface of the piezoelectric layer, The IDT electrode comprises a first bus bar portion and a second bus bar portion facing each other, and a plurality of electrode fingers, wherein the plurality of electrode fingers include at least one first electrode finger having one end connected to the first bus bar portion, and at least one second electrode finger having one end connected to the second bus bar portion, wherein the first electrode finger and the second electrode finger are interlaced with each other. When viewed from a direction perpendicular to the direction in which the first electrode fingers and the second electrode fingers extend, a region where adjacent first electrode fingers and second electrode fingers overlap each other is a crossing region. The support member is provided with a cavity portion, and the cavity portion overlaps with the intersection region in a plan view. At least one of the first bus bar portion and the second bus bar portion has an outer bus bar and at least one protruding electrode, the outer bus bar does not overlap with the hollow portion when viewed from above, the at least one protruding electrode extends from the outer bus bar toward the intersection area side and is opposite to the electrode fingers among the multiple electrode fingers that are not connected to the outer bus bar, and the protruding electrode overlaps with the outer peripheral edge of the hollow portion when viewed from above.

2. The elastic wave device according to claim 1, wherein: Both the first bus bar portion and the second bus bar portion include the protruding electrode.

3. The elastic wave device according to claim 1 or 2, wherein: The bus bar portion having the protruding electrode among the first bus bar portion and the second bus bar portion further comprises: an inner bus bar provided between the intersection region and the protruding electrode; The electrode finger connected to the bus bar portion having the inner bus bar includes a connection portion connecting the inner bus bar and the outer bus bar.

4. The elastic wave device according to claim 3, wherein: The connecting portion is a first connecting portion, The inner bus bar extends to a portion that does not overlap with the cavity portion in a plan view. The outer bus bar has at least one second connection portion that connects the inner bus bar and the outer bus bar.

5. The elastic wave device according to any one of claims 1 to 4, wherein: The piezoelectric layer includes lithium niobate or lithium tantalate.

6. The elastic wave device according to any one of claims 1 to 5, wherein: The elastic wave device is configured to utilize thickness shear mode bulk waves.

7. The elastic wave device according to any one of claims 1 to 6, wherein: When the thickness of the piezoelectric layer is denoted as d and the center-to-center distance between adjacent electrode fingers is denoted as p, d / p is equal to or less than 0.

5.

8. The elastic wave device according to claim 7, wherein: d / p is less than 0.

24.

9. The elastic wave device according to any one of claims 1 to 8, wherein: The intersection region includes: a plurality of excitation regions, each located between the centers of the adjacent electrode fingers; When the metallization ratio of the plurality of electrode fingers to the excitation region is defined as MR, MR≦1.75(d / p)+0.075 is satisfied.

10. The elastic wave device according to any one of claims 1 to 9, wherein: The piezoelectric layer includes lithium niobate or lithium tantalate, The lithium niobate or the Euler angles (φ, θ, ψ) of lithium niobate constituting the piezoelectric layer are within the range of the following formula (1), formula (2) or formula (3), (0°±10°, 0°~20°, arbitrary ψ) …Formula (1) (0°±10°, 20°~80°, 0°~60° (1-(θ-50) 2 / 900) 1 / 2 ) or (0°±10°, 20°~80°, [180°-60° (1-(θ-50) 2 / 900) 1 / 2 ]~180°) …Formula (2) (0°±10°, [180°-30°(1-(ψ-90) 2 / 8100) 1 / 2 ]~180°, arbitrary ψ) …Formula (3).

11. The elastic wave device according to any one of claims 1 to 5, wherein: The elastic wave device is configured to utilize plate waves.

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