Elastic wave device

Abstract

An elastic wave device is provided that can suppress the breakage of IDT electrodes and the peeling of IDT electrodes from a piezoelectric layer. The elastic wave device (10) includes a support member (13), a piezoelectric layer (14), an IDT electrode (25) having first and second busbars (26, 27) and a plurality of first and second electrode fingers (28, 29), and a first insulating film (17A) disposed on the piezoelectric layer (14) and covering the front ends of the plurality of second electrode fingers (29). In the stack of the support member (13) and the piezoelectric layer 14, a cavity (13c) is provided at a position closer to the support member (13) than the piezoelectric layer (14). When the direction of extension of multiple electrode fingers is set as the electrode finger extension direction, in top view, the outer periphery of the cavity (13c) includes a first and a second outer periphery (13d, 13e) opposite to each other in the electrode finger extension direction. The first outer periphery (13d) is located on the side of the first busbar (26), and the first insulating film (17A) extends on the side of the first busbar (26) and overlaps with the first outer periphery (13d) of the cavity (13c) in top view.

Description

Technical Field

[0001] This invention relates to elastic wave devices. Background Technology

[0002] Previously, elastic wave devices have been widely used in filters for portable telephones, etc. Patent Document 1 discloses an example of an elastic wave device utilizing a plate wave. In this elastic wave device, a LiNbO3 substrate is provided on a support. A through-hole is provided in the support. An IDT (Interdigital Transducer) electrode is provided in the portion of the LiNbO3 substrate facing the through-hole.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: International Publication No. 2013 / 021948 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] In the elastic wave device described in Patent Document 1, the portion of the piezoelectric layer of the LiNbO3 substrate that overlaps with the void when viewed from above may be easily deformed due to the pressure difference between the surface and back of the piezoelectric layer. Therefore, the tip of the electrode finger of the IDT electrode may peel off from the piezoelectric layer or the electrode finger may break.

[0008] The purpose of this invention is to provide an elastic wave device capable of suppressing the breakage of IDT electrodes and the peeling of IDT electrodes from the piezoelectric layer.

[0009] means for solving problems

[0010] The elastic wave device of the present invention comprises: a support member having a support substrate; a piezoelectric layer disposed on the support member; an IDT electrode disposed on the piezoelectric layer having a first busbar and a second busbar facing each other and a plurality of electrode fingers; and a first insulating film disposed on the piezoelectric layer and covering the front ends of the plurality of electrode fingers facing the first busbar. In the laminate of the support member and the piezoelectric layer, a cavity is provided at a position closer to the support member than the piezoelectric layer. In plan view, at least a portion of the IDT electrode overlaps with the cavity. When the direction in which the plurality of electrode fingers extend is defined as the electrode finger extension direction, in plan view, the outer periphery of the cavity includes a first outer periphery portion and a second outer periphery portion facing each other in the electrode finger extension direction. The first outer periphery portion is located on the first busbar side, and the first insulating film extends on the first busbar side and overlaps with the first outer periphery portion of the cavity in plan view.

[0011] Invention Effects

[0012] The elastic wave device according to the present invention can suppress the breakage of the IDT electrode and the peeling of the IDT electrode from the piezoelectric layer. Attached Figure Description

[0013] Figure 1 This is a schematic cross-sectional view of the elastic wave device according to the first embodiment of the present invention along the direction in which the electrode fingers extend.

[0014] Figure 2 This is a schematic top view of the elastic wave device according to the first embodiment of the present invention.

[0015] Figure 3 (a) is a schematic cross-sectional view of the elastic wave device of the comparative example along the direction of the extension of the electrode fingers. Figure 3 (b) is a schematic cross-sectional view showing an example of a piezoelectric layer in a comparative elastic wave device deforming due to the pressure difference between the two main surfaces.

[0016] Figure 4 This is a schematic top view of an elastic wave device according to a first variation of the first embodiment of the present invention.

[0017] Figure 5 This is a schematic cross-sectional view of the elastic wave device of the second variation of the first embodiment of the present invention along the direction of extension of the electrode fingers.

[0018] Figure 6 This is a schematic cross-sectional view of the elastic wave device of the third variation of the first embodiment of the present invention along the direction of extension of the electrode fingers.

[0019] Figure 7 This is a schematic cross-sectional view of the elastic wave device of the fourth variation of the first embodiment of the present invention along the direction of extension of the electrode fingers.

[0020] Figure 8 This is a schematic top view of the elastic wave device according to the second embodiment of the present invention.

[0021] Figure 9 This is a schematic cross-sectional view of the elastic wave device according to the third embodiment of the present invention, along the direction in which the electrode fingers extend.

[0022] Figure 10 This is a schematic cross-sectional view of the elastic wave device according to the fourth embodiment of the present invention, along the direction in which the electrode fingers extend.

[0023] Figure 11 (a) is a perspective view of a simplified diagram showing the appearance of an elastic wave device utilizing a thickness shear mode for volume waves. Figure 11 (b) is a top view showing the electrode structure on the piezoelectric layer.

[0024] Figure 12 It is along Figure 11 A sectional view of the portion of line AA in (a).

[0025] Figure 13 (a) is a schematic front sectional view illustrating the propagation of a Lamb wave in a piezoelectric film of an elastic wave device. Figure 13 (b) is a schematic front sectional view of a bulk wave used to illustrate the thickness shear mode of propagation of a piezoelectric film in an elastic wave device.

[0026] Figure 14 This is a diagram showing the amplitude direction of the body wave in the thickness shear mode.

[0027] Figure 15 This is a diagram showing the resonant characteristics of an elastic wave device utilizing a thickness shear mode for body waves.

[0028] Figure 16 This is a graph showing the relationship between d / p and the fractional bandwidth of the resonator when the center-to-center distance between adjacent electrodes is set to p and the thickness of the piezoelectric layer is set to d.

[0029] Figure 17 This is a top view of an elastic wave device that utilizes the thickness shear mode of body waves.

[0030] Figure 18 This is a diagram showing the resonant characteristics of an elastic wave device with stray emissions, representing a reference example.

[0031] Figure 19This is a graph showing the relationship between the fractional bandwidth and the amount of phase rotation of the spurious impedance normalized to 180 degrees, which is the spurious size.

[0032] Figure 20 This is a graph showing the relationship between d / 2p and metallization rate MR.

[0033] Figure 21 This is a graph showing the mapping of the fractional bandwidth relative to the Euler angles (0°, θ, ψ) of LiNbO3 when d / p is infinitely close to 0.

[0034] Figure 22 This is a partially truncated three-dimensional diagram used to illustrate an elastic wave device utilizing Lamb waves. Detailed Implementation

[0035] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings, thereby making the present invention clear.

[0036] It should be noted that the embodiments described in this specification are illustrative, and it is indicated in advance that partial substitutions or combinations of structures can be made between different embodiments.

[0037] Figure 1 This is a schematic cross-sectional view of the elastic wave device according to the first embodiment of the present invention along the direction in which the electrode fingers extend. Figure 2 This is a schematic top view of the elastic wave device according to the first embodiment. It should be noted that... Figure 1 It is along Figure 2 A schematic cross-sectional view of line II in the diagram. The electrode fingers described above will be described later.

[0038] like Figure 1 As shown, the elastic wave device 10 has a piezoelectric substrate 12 and an IDT electrode 25. The piezoelectric substrate 12 has a support member 13 and a piezoelectric layer 14. In this embodiment, the support member 13 includes a support substrate 16 and a bonding layer 15 as an insulating layer. The bonding layer 15 is provided on the support substrate 16. The piezoelectric layer 14 is provided on the bonding layer 15. However, the support member 13 may also be composed solely of the support substrate 16.

[0039] A cavity 13c is provided in the support member 13. More specifically, a through hole is provided in the bonding layer 15. A through hole is provided in the support substrate 16, communicating with the through hole in the bonding layer 15. It should be noted that a recess may be provided in the support substrate 16 instead of a through hole. A piezoelectric layer 14 is provided on the bonding layer 15 to block the through hole. Thus, the cavity 13c of the support member 13 is formed. In this embodiment, the cavity 13c is formed in both the support substrate 16 and the bonding layer 15. However, the cavity 13c may also be formed only in the bonding layer 15. Alternatively, the cavity 13c may also be formed only in the support substrate 16.

[0040] As the material for the bonding layer 15, suitable dielectrics such as silicon oxide or tantalum pentoxide can be used. As the material for the support substrate 16, semiconductors such as silicon, suitable ceramics, etc., can be used.

[0041] The piezoelectric layer 14 has a first main surface 14a and a second main surface 14b. The first main surface 14a and the second main surface 14b are opposite to each other. The second main surface 14b is the main surface on the side of the support member 13. The piezoelectric layer 14 has a film portion 14c. The film portion 14c is the portion of the piezoelectric layer 14 that overlaps with the void portion 13c when viewed from above. The film portion 14c has a warped shape that is convex on the side of the first main surface 14a. However, the film portion 14c may not have a warped shape.

[0042] The piezoelectric layer 14 includes, for example, lithium niobate such as LiNbO3 or lithium tantalate such as LiTaO3. In this specification, the inclusion of a component in a material includes trace impurities that contribute to the degree to which the electrical properties of the elastic wave device are not degraded.

[0043] An IDT electrode 25 is disposed on the first main surface 14a of the piezoelectric layer 14. At least a portion of the IDT electrode 25 overlaps with the cavity 13c of the support member 13 when viewed from above. In this specification, "viewing from above" means from the perspective of... Figure 1 Observe from the direction roughly above.

[0044] like Figure 2As shown, the IDT electrode 25 has a first busbar 26 and a second busbar 27 as a pair of busbars, and a plurality of first electrode fingers 28 and a plurality of second electrode fingers 29. The first electrode fingers 28 are the first electrodes in this invention. The plurality of first electrode fingers 28 are periodically arranged. One end of each of the plurality of first electrode fingers 28 is connected to the first busbar 26. The other end, i.e., the front end, of each of the plurality of first electrode fingers 28 is opposite to the second busbar 27. The second electrode fingers 29 are the second electrodes in this invention. The plurality of second electrode fingers 29 are periodically arranged. One end of each of the plurality of second electrode fingers 29 is connected to the second busbar 27. The other end, i.e., the front end, of each of the plurality of second electrode fingers 29 is opposite to the first busbar 26. The plurality of first electrode fingers 28 and the plurality of second electrode fingers 29 are interleaved and interlocked.

[0045] The IDT electrode 25 may also include a stacked metal film, or it may include a single-layer metal film. In this specification, the first electrode finger 28 and the second electrode finger 29 may sometimes be referred to simply as electrode fingers.

[0046] A first insulating film 17A is provided on the first main surface 14a of the piezoelectric layer 14. More specifically, the first insulating film 17A covers the front ends of a plurality of second electrode fingers 29. The first insulating film 17A extends from the front ends of the plurality of second electrode fingers 29 toward the first busbar 26. The first insulating film 17A overlaps with the outer periphery of the cavity 13c of the support member 13 when viewed from above. It should be noted that, in this embodiment, the outer periphery of the cavity 13c is the outer periphery of the through hole of the bonding layer 15 when viewed from above.

[0047] More specifically, in this embodiment, the cavity 13c has a rectangular shape when viewed from above. The outer periphery of the cavity 13c has a first outer periphery portion 13d and a second outer periphery portion 13e. The first outer periphery portion 13d and the second outer periphery portion 13e correspond to a pair of opposite sides of the rectangle. When the direction in which the plurality of electrode fingers extend is defined as the electrode finger extension direction, the first outer periphery portion 13d and the second outer periphery portion 13e are opposite to each other in the electrode finger extension direction. The first outer periphery portion 13d is located on the side of the first busbar 26. The first outer periphery portion 13d and the second outer periphery portion 13e are straight. However, the first outer periphery portion 13d and the second outer periphery portion 13e can also be curved.

[0048] Figure 1 The single-dotted line in the diagram indicates the portion overlapping with the first outer peripheral portion 13d and the portion overlapping with the second outer peripheral portion 13e when viewed from above. The first insulating film 17A overlaps with the first outer peripheral portion 13d when viewed from above. More specifically, the first insulating film 17A covers the boundary between the overlapping and non-overlapping areas of the void portion 13c and the piezoelectric layer 14 when viewed from above.

[0049] A second insulating film 17B is provided on the first main surface 14a of the piezoelectric layer 14. More specifically, the second insulating film 17B covers the front ends of the plurality of first electrode fingers 28. The second insulating film 17B extends from the front ends of the plurality of first electrode fingers 28 toward the second busbar 27. In top view, the second insulating film 17B overlaps with the second outer peripheral edge 13e of the cavity 13c of the support member 13.

[0050] The first insulating film 17A and the second insulating film 17B can be, for example, inorganic insulating films or resin films. When the first insulating film 17A and the second insulating film 17B are inorganic insulating films, silicon oxide can be used, for example. Silicon oxide is, for example, SiO2. When the first insulating film 17A and the second insulating film 17B are resin films, polyimide can be used, for example.

[0051] The feature of this embodiment is that the first insulating film 17A covers the front ends of the plurality of second electrode fingers 29 and, when viewed from above, overlaps with the first outer peripheral portion 13d of the cavity portion 13c. This suppresses damage to the IDT electrode 25 and its peeling from the piezoelectric layer 14. This will be explained below by comparing this embodiment with a comparative example.

[0052] like Figure 3 As shown in (a), in the comparative example, neither the first insulating film nor the second insulating film is provided. The pressure applied to the first main surface 14a and the second main surface 14b of the piezoelectric layer 14 varies depending on the external environment, etc. Therefore, for example, Figure 3 As shown in (b), the shape of the film portion 14c of the piezoelectric layer 14 sometimes changes to a warped shape that becomes convex on the second main surface 14b side. Such changes in the shape of the piezoelectric layer 14 may cause the tip of the electrode finger to peel off as shown by arrow E1, or breakage near the base of the electrode finger as shown by arrow E2.

[0053] In contrast, Figure 1 In the embodiment shown, the first insulating film 17A covers the front ends of the plurality of second electrode fingers 29. This suppresses peeling of the front ends of the plurality of second electrode fingers 29.

[0054] Furthermore, the first insulating film 17A overlaps with the first outer peripheral edge 13d of the cavity 13c in the support member 13 when viewed from above. More specifically, in this embodiment, the first outer peripheral edge 13d overlaps with the first busbar 26 when viewed from above. Therefore, the first insulating film 17A covers a portion of the first busbar 26 and the base ends of the plurality of first electrode fingers 28. As a result, breakage near the base ends of the plurality of first electrode fingers 28 can be suppressed.

[0055] It should be noted that the first outer peripheral portion 13d may not overlap with the first busbar 26 when viewed from above. For example, the first outer peripheral portion 13d may overlap with the front ends of the plurality of second electrode fingers 29 and the area between the first busbar 26 when viewed from above. In this case, breakage of the portion of the plurality of first electrode fingers 28 covered by the first insulating film 17A can also be suppressed.

[0056] As in this embodiment, it is preferable that the second insulating film 17B covers the front ends of the plurality of first electrode fingers 28, and the second insulating film 17B overlaps with the second outer peripheral edge 13e of the cavity 13c of the support member 13 when viewed from above. This suppresses peeling of the front ends of the plurality of first electrode fingers 28 and also suppresses breakage of the plurality of second electrode fingers 29.

[0057] As described above, the film portion 14c of the piezoelectric layer 14 has a warped shape that is convex on the first main surface 14a side. When obtaining the piezoelectric substrate 12 of this embodiment, for example, when adjusting the thickness of the piezoelectric layer 14 while it is stacked on the support member 13, the processing pressure such as grinding the piezoelectric layer 14 can be adjusted to make the piezoelectric layer 14 into the shape described above. Alternatively, for example, a piezoelectric layer 14 of the above shape prepared separately can be bonded to the support member 13.

[0058] However, when the direction in which adjacent electrodes point to each other is defined as the electrode pointing direction, in this embodiment, such as Figure 2 As shown, the electrode finger opposition direction is orthogonal to the electrode finger extension direction. In this specification, the electrode finger opposition direction is synonymous with the direction in which multiple electrode fingers are arranged. When viewed from the electrode finger opposition direction, the area where adjacent electrode fingers overlap is the intersection region F. The intersection region F includes the area from one end of the electrode finger in the electrode finger opposition direction of the IDT electrode 25 to the other end of the electrode finger. More specifically, the intersection region F includes the area from the outer edge of the electrode finger in the electrode finger opposition direction at one end to the outer edge of the electrode finger in the electrode finger opposition direction at the other end.

[0059] Furthermore, the elastic wave device 10 has multiple excitation regions C. Elastic waves are excited in the multiple excitation regions C by applying an AC voltage to the IDT electrode 25. In this embodiment, for example, the elastic wave device 10 is configured to utilize a volume wave with a thickness shear mode, such as a first-order thickness shear mode. The excitation regions C, like the cross regions F, are regions where adjacent electrode fingers overlap when viewed from the electrode finger-opposing direction. It should be noted that each excitation region C is a region between a pair of electrode fingers. More specifically, the excitation region C is the region extending from the center of one electrode finger in the electrode finger-opposing direction to the center of the other electrode finger in the electrode finger-opposing direction. Therefore, the cross regions F include multiple excitation regions C. However, the elastic wave device 10 may also be configured to utilize a plate wave, for example. In the case where the elastic wave device 10 utilizes a plate wave, the cross regions F are the excitation regions.

[0060] like Figure 2 As shown, the first insulating film 17A and the second insulating film 17B are disposed on the portion where the tips of the plurality of electrode fingers are located in the intersection region F. On the other hand, the first insulating film 17A and the second insulating film 17B are not disposed outside the portion where the tips of the plurality of electrode fingers are located in the intersection region F. Thus, the first insulating film 17A and the second insulating film 17B are not disposed on a part of the intersection region F. However, the first insulating film 17A and the second insulating film 17B may also be disposed on the entire intersection region F.

[0061] In this embodiment, the first insulating film 17A covers a portion of the electrode fingers of the first busbar 26 in the opposite direction. Similarly, the second insulating film 17B covers a portion of the electrode fingers of the second busbar 27 in the opposite direction. However, this is not a limitation. For example, in Figure 4 In the first variation of the first embodiment shown, the first insulating film 17A covers the entire electrode fingers of the first busbar 26 in the opposite direction. The second insulating film 17B covers the entire electrode fingers of the second busbar 27 in the opposite direction. In this case, damage to the IDT electrode 25 and peeling of the IDT electrode 25 from the piezoelectric layer 14 can also be suppressed.

[0062] As described above, the void portion 13c of the support member 13 is formed on both the bonding layer 15 and the support substrate 16. It should be noted that the void portion 13c only needs to be provided in the laminate of the support member 13 and the piezoelectric layer 14 at a position closer to the support member 13 than the piezoelectric layer 14. Hereinafter, second to fourth modifications of the first embodiment are shown, differing only in the structure of the support member 13 from the first embodiment. In the second to fourth modifications, the breakage of the IDT electrode 25 and the peeling of the IDT electrode 25 from the piezoelectric layer 14 can be suppressed, similar to the first embodiment.

[0063] exist Figure 5In the second modified example shown, the recess is provided only in the bonding layer 35A. No recess or through hole is provided in the support substrate 36. Therefore, the cavity 33c1 of the support member 33A is formed only in the bonding layer 35A.

[0064] exist Figure 6 In the third variation shown, similar to the first embodiment, a through hole is provided in the bonding layer 15. On the other hand, no recess or through hole is provided in the support substrate 36. Thus, only the cavity 33c2 of the support member 33B is formed in the bonding layer 15.

[0065] exist Figure 7 In the fourth variation shown, a cavity 33c3 is provided between the support member 33C and the piezoelectric layer 14. More specifically, no recess or through hole is provided in the support substrate 36 and the bonding layer 35C. Therefore, the cavity 33c3 is not formed in the support member 33C. On the other hand, similar to the first embodiment, a portion of the piezoelectric layer 14 has a warped shape that is convex on the first main surface 14a side. Thus, a cavity 33c3 is provided between the support member 33C and the piezoelectric layer 14. The portion of the piezoelectric layer 14 facing the cavity 33c3 is the film portion 14c in this variation. It should be noted that in this variation, the boundary between the contact portion and the non-contact portion of the piezoelectric layer 14 and the bonding layer 35C is the outer periphery of the cavity 33c3. The portion corresponding to the edge on the first busbar 26 side of this outer periphery is the first outer periphery portion 33d. The portion corresponding to the side of the second busbar 27 on the outer periphery is the second outer periphery portion 33e.

[0066] like Figure 2 As shown, in the first embodiment, the first insulating film 17A and the second insulating film 17B are separately provided. However, the first insulating film 17A and the second insulating film 17B can also be provided as a single unit. This example is shown in the following second and third embodiments. It should be noted that the elastic wave device of the second and third embodiments has the same structure as the elastic wave device 10 of the first embodiment, except that it is provided with insulating films including the first insulating film 17A and the second insulating film 17B. Moreover, in the second and third embodiments, the damage to the IDT electrode 25 and the peeling of the IDT electrode 25 from the piezoelectric layer 14 can be suppressed in the same way as in the first embodiment.

[0067] Figure 8 This is a schematic top view of the elastic wave device according to the second embodiment.

[0068] In this embodiment, an insulating film 47 is provided on the first main surface 14a of the piezoelectric layer 14. The insulating film 47 is an integral insulating film consisting of a first insulating film 17A and a second insulating film 17B. The insulating film 47 includes the first insulating film 17A, the second insulating film 17B, and two connecting portions 47c. Each connecting portion 47c connects the ends of the first insulating film 17A and the second insulating film 17B in a direction parallel to the direction opposite to the electrode fingers to each other. The insulating film 47 is not provided outside the portion where the front ends of the plurality of electrode fingers are located in the intersection region F.

[0069] Figure 9 This is a schematic cross-sectional view of the elastic wave device of the third embodiment along the direction in which the electrode fingers extend.

[0070] In this embodiment, an insulating film 57 is provided on the first main surface 14a of the piezoelectric layer 14. The insulating film 57 is an integral insulating film consisting of the first insulating film 17A and the second insulating film 17B. More specifically, the insulating film 57 is configured to cover the entire IDT electrode 25 on the first main surface 14a. In the portion where the IDT electrode 25 is provided, the piezoelectric layer 14, the IDT electrode 25, and the insulating film 57 are sequentially stacked. In this embodiment, the entire intersection region F is covered by the insulating film 57.

[0071] The insulating film 57 has a first insulating film 17A, a second insulating film 17B, and a third insulating film 57C. In this embodiment, the first insulating film 17A corresponds to the portion of the insulating film 57 that covers the front ends of the plurality of second electrode fingers 29 and overlaps with the first outer peripheral portion 13d of the cavity 13c of the support member 13 when viewed from above. The second insulating film 17B corresponds to the portion of the insulating film 57 that covers the front ends of the plurality of first electrode fingers 28 and overlaps with the second outer peripheral portion 13e when viewed from above. The third insulating film 57C constitutes all the portions of the insulating film 57 except for the first insulating film 17A and the second insulating film 17B.

[0072] In this embodiment, the thickness of the first insulating film 17A and the second insulating film 17B is greater than the thickness of the third insulating film 57C. This effectively suppresses damage to the IDT electrode 25 and its peeling from the piezoelectric layer 14. It should be noted that the thickness of the first insulating film 17A and the second insulating film 17B can also be the same as the thickness of the third insulating film 57C.

[0073] Figure 10 This is a schematic cross-sectional view of the elastic wave device of the fourth embodiment along the direction in which the electrode fingers extend.

[0074] The difference between this embodiment and the first embodiment is that the dielectric film 66 is configured to cover the entire IDT electrode 25 on the first main surface 14a of the piezoelectric layer 14. The dielectric film 66 is disposed between the piezoelectric layer 14 and the IDT electrode 25 and the first insulating film 17A and the second insulating film 17B. Apart from the above aspects, the elastic wave device of this embodiment has the same structure as the elastic wave device 10 of the first embodiment.

[0075] The material of the dielectric film 66 is different from the materials of the first insulating film 17A and the second insulating film 17B. For example, silicon oxide, silicon nitride, or silicon oxynitride can be used as the material of the dielectric film 66.

[0076] In this embodiment, the IDT electrode 25 is covered by the dielectric film 66, thus making the IDT electrode 25 difficult to damage. However, it is sufficient for the dielectric film 66 to cover at least a portion of the IDT electrode 25.

[0077] Furthermore, in this embodiment, the first insulating film 17A and the second insulating film 17B are provided in the same manner as in the first embodiment. Therefore, the laminate of the first insulating film 17A and the dielectric film 66 covers the leading ends of the plurality of second electrode fingers 29 and overlaps with the first outer peripheral portion 13d of the cavity 13c of the support member 13 when viewed from above. The laminate of the second insulating film 17B and the dielectric film 66 covers the leading ends of the plurality of first electrode fingers 28 and overlaps with the second outer peripheral portion 13e when viewed from above. This further suppresses damage to the IDT electrode 25 and peeling of the IDT electrode 25 from the piezoelectric layer 14.

[0078] The elastic wave device utilizing a thickness shear mode for bulk waves will now be described in detail. It should be noted that the insulating layer described below corresponds to the bonding layer described above. The supporting member described below corresponds to the supporting substrate described above.

[0079] Figure 11 (a) is a perspective view of a simplified diagram showing the appearance of an elastic wave device utilizing a thickness shear mode for volume waves. Figure 11 (b) is a top view showing the electrode structure on the piezoelectric layer. Figure 12 It is along Figure 11 A sectional view of the portion of line AA in (a).

[0080] The elastic wave device 1 has a piezoelectric layer 2 comprising LiNbO3. The piezoelectric layer 2 may also comprise LiTaO3. The LiNbO3 and LiTaO3 are cut at a Z-angle, but can also be rotary cut at a Y-angle or X-angle. The thickness of the piezoelectric layer 2 is not particularly limited, but for effectively exciting the thickness shear mode, it is preferably 40 nm or more and 1000 nm or less, more preferably 50 nm or more and 1000 nm or less. The piezoelectric layer 2 has a first main surface 2a and a second main surface 2b opposite to each other. An electrode 3 and an electrode 4 are provided on the first main surface 2a. Here, electrode 3 is an example of a "first electrode," and electrode 4 is an example of a "second electrode." Figure 11 (a) and Figure 11 In (b), multiple electrodes 3 are connected to the first busbar 5. Multiple electrodes 4 are connected to the second busbar 6. The multiple electrodes 3 and multiple electrodes 4 are interleaved. Electrodes 3 and 4 have a rectangular shape and a length direction. Electrode 3 and adjacent electrode 4 are opposite each other in a direction orthogonal to this length direction. The length directions of electrodes 3 and 4, and the directions orthogonal to the length directions of electrodes 3 and 4, are both directions that intersect the thickness direction of the piezoelectric layer 2. Therefore, it can also be said that electrode 3 and adjacent electrode 4 are opposite each other in a direction that intersects the thickness direction of the piezoelectric layer 2. Alternatively, the length directions of electrodes 3 and 4 can be changed to intersect the thickness direction of the piezoelectric layer 2. Figure 11 (a) and Figure 11 The length directions of electrodes 3 and 4 shown in (b) are orthogonal. That is, in Figure 11 (a) and Figure 11 In (b), electrodes 3 and 4 can also extend along the directions in which the first busbar 5 and the second busbar 6 extend. In this case, the first busbar 5 and the second busbar 6 are... Figure 11 (a) and Figure 11(b) extends along the direction in which electrodes 3 and 4 extend. Furthermore, multiple pairs of electrodes 3 connected to one potential and electrodes 4 connected to another potential are arranged adjacent to each other in a direction orthogonal to the length direction of electrodes 3 and 4. Here, "adjacent to electrodes 3 and 4" does not mean that electrodes 3 and 4 are in direct contact, but rather that they are arranged with a gap between them. Additionally, when electrodes 3 and 4 are adjacent, no electrodes connected to signal electrodes or ground electrodes, including other electrodes 3 and 4, are arranged between electrodes 3 and 4. This number of pairs does not need to be an integer; it can be 1.5 pairs, 2.5 pairs, etc. The center-to-center distance, i.e., the spacing, between electrodes 3 and 4 is preferably in the range of 1 μm or more and 10 μm or less. Furthermore, the width of electrodes 3 and 4, i.e., the dimension in the opposing direction of electrodes 3 and 4, is preferably in the range of 50 nm or more and 1000 nm or less, more preferably in the range of 150 nm or more and 1000 nm or less. It should be noted that the center-to-center distance between electrodes 3 and 4 is the distance obtained by connecting the center of the dimension (width dimension) of electrode 3 in the direction orthogonal to the length direction of electrode 3 and the center of the dimension (width dimension) of electrode 4 in the direction orthogonal to the length direction of electrode 4.

[0081] Furthermore, in the elastic wave device 1, a Z-cut piezoelectric layer is used. Therefore, the direction orthogonal to the length direction of electrodes 3 and 4 becomes the direction orthogonal to the polarization direction of piezoelectric layer 2. This is not limited to cases where a piezoelectric material with a different cut angle is used as piezoelectric layer 2. Here, "orthogonal" is not limited to strictly orthogonal, but can also be approximately orthogonal (the angle between the direction orthogonal to the length direction of electrodes 3 and 4 and the polarization direction is, for example, within the range of 90° ± 10°).

[0082] On the second main surface 2b side of the piezoelectric layer 2, a support member 8 is stacked with an insulating layer 7 in between. The insulating layer 7 and the support member 8 have a frame-like shape, such as... Figure 12 As shown, it has through holes 7a and 8a. This forms a cavity 9. The cavity 9 is provided so as not to interfere with 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 with the insulating layer 7 in a position that does not overlap with the portion where at least one pair of electrodes 3 and 4 are provided. It should be noted that the insulating layer 7 may also be omitted. Therefore, the support member 8 may be stacked directly or indirectly on the second main surface 2b of the piezoelectric layer 2.

[0083] The insulating layer 7 comprises silicon oxide. However, in addition to silicon oxide, suitable insulating materials such as silicon oxynitride and bauxite can also be used. The support member 8 comprises Si. The orientation of the face of the piezoelectric layer 2 of Si can be (100), (110), or (111). The Si constituting the support member 8 is preferably a high resistivity of 4kΩ or higher. However, the support member 8 can also be constructed using suitable insulating materials or semiconductor materials.

[0084] Materials used as support components 8 include, for example, piezoelectric materials such as alumina, lithium tantalate, lithium niobate, and quartz, bauxite, magnesium oxide, sapphire, silicon nitride, aluminum nitride, silicon carbide, zirconium oxide, cordierite, mullite, block talc, magnesium olivine, diamond, glass, and other dielectrics, as well as semiconductors such as gallium nitride.

[0085] The aforementioned electrodes 3 and 4, as well as the first busbar 5 and the second busbar 6, comprise suitable metals or alloys such as Al and AlCu alloys. In this embodiment, the electrodes 3 and 4, and the first busbar 5 and the second busbar 6, have a structure in which an Al film is laminated on a Ti film. It should be noted that a bonding layer other than a Ti film may also be used.

[0086] During operation, an alternating current voltage is applied between the plurality of electrodes 3 and the plurality of electrodes 4. More specifically, an alternating current voltage is applied between the first busbar 5 and the second busbar 6. This allows for the resonant characteristics of a bulk wave utilizing the thickness shear mode excited in the piezoelectric layer 2. Furthermore, 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 two adjacent pairs of electrodes 3 and 4 is set to p, d / p is 0.5 or less. Therefore, the aforementioned thickness shear mode bulk wave can be effectively excited, resulting in good resonant characteristics. More preferably, d / p is 0.24 or less, in which case even better resonant characteristics can be obtained.

[0087] In the elastic wave device 1, due to the aforementioned structure, even if the number of pairs of electrodes 3 and 4 is reduced to achieve miniaturization, a decrease in the Q value is difficult to achieve. This is because even if the number of electrode fingers in the reflectors on both sides is reduced, the propagation loss is low. Furthermore, the ability to reduce the number of electrode fingers is achieved based on the use of volume waves with a thickness shear mode. (Refer to...) Figure 13 (a) and Figure 13 (b) illustrates the difference between the Lamb wave used in the elastic wave device and the volume wave of the thickness shear mode described above.

[0088] Figure 13(a) is a schematic front sectional view illustrating the Lamb wave propagating in the piezoelectric film of the elastic wave device described in Japanese Patent Publication No. 2012-257019. Here, the wave propagates in the piezoelectric film 201 as indicated by the arrow. Here, in the piezoelectric film 201, the first main surface 201a and the second main surface 201b are opposite 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 electrodes are arranged. Figure 13 As shown in (a), for a Lamb wave, the wave propagates along the X direction as illustrated. Since it is a plate wave, although the piezoelectric film 201 vibrates as a whole, the wave propagates along the X direction, so reflectors are placed on both sides to obtain a resonant characteristic. Therefore, wave propagation loss occurs, and the Q value decreases when miniaturization is achieved, i.e., when the number of electrode finger pairs is reduced.

[0089] In contrast, such as Figure 13 As shown in (b), in the elastic wave device 1, the vibration displacement is in the thickness shear direction. Therefore, the wave propagates and resonates approximately along the Z direction, which connects the first principal surface 2a and the second principal surface 2b of the piezoelectric layer 2. That is, the X-direction component of the wave is significantly smaller than the Z-direction component. Moreover, since the resonance characteristic is obtained through the propagation of the wave in the Z direction, it is difficult to generate propagation loss even if the number of electrode fingers of the reflector is reduced. Furthermore, even if the number of electrode pairs, including electrodes 3 and 4, is reduced to promote miniaturization, it is difficult to generate a decrease in the Q value.

[0090] It should be noted that, as Figure 14 As shown, the amplitude direction of the bulk wave in the thickness shear mode is opposite in the first excitation region 451 and the second excitation region 452 contained in the excitation region C of the piezoelectric layer 2. Figure 14 The diagram schematically illustrates a bulk wave when a voltage higher at electrode 4 than at electrode 3 is applied between electrodes 3 and 4. The first excitation region 451 is the region within excitation region C between an imaginary plane VP1, orthogonal to the thickness direction of the piezoelectric layer 2 and dividing the piezoelectric layer 2 into two parts, and the first main surface 2a. The second excitation region 452 is the region within excitation region C between the imaginary plane VP1 and the second main surface 2b.

[0091] As described above, the elastic wave device 1 is provided with at least one pair of electrodes, including electrodes 3 and 4. However, since the wave is not allowed to propagate in the X direction, the number of electrode pairs including electrodes 3 and 4 does not need to be multiple. That is, it is sufficient to provide at least one pair of electrodes.

[0092] For example, electrode 3 is connected to the signal potential, and electrode 4 is connected to the ground potential. However, it is also possible that electrode 3 is connected to the ground potential, and electrode 4 is connected to the signal potential. In this embodiment, at least one pair of electrodes is either connected to the signal potential or connected to the ground potential as described above, and no floating electrode is provided.

[0093] Figure 15 It is shown Figure 12 The diagram shows the resonant characteristics of the elastic wave device. It should be noted that the design parameters for the elastic wave device 1, from which these resonant characteristics are obtained, are as follows.

[0094] Piezoelectric layer 2: LiNbO3 with Euler angles (0°, 0°, 90°) and a thickness of 400 nm.

[0095] When viewed from a direction orthogonal to the length direction of electrodes 3 and 4, the length of the excitation region C, which is the area where electrodes 3 and 4 overlap, is 40 μm. The number of electrode pairs 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. d / p = 0.133.

[0096] Insulating layer 7: Silicon oxide film with a thickness of 1 μm.

[0097] Supporting component 8: Si.

[0098] It should be noted that the length of the excitation region C refers to the dimension of the excitation region C along the length direction of electrodes 3 and 4.

[0099] In this embodiment, the distance between the electrodes of the electrode pairs including electrodes 3 and 4 is equal in all pairs. That is, electrodes 3 and 4 are arranged at equal intervals.

[0100] according to Figure 15 It can be seen that, despite not having a reflector, a good resonant characteristic with a fractional bandwidth of 12.5% ​​was obtained.

[0101] However, when the thickness of the piezoelectric layer 2 is set to d and the center-to-center distance between the electrodes of electrode 3 and electrode 4 is set to p, as described above, in this embodiment, d / p is 0.5 or less, more preferably 0.24 or less. (Refer to...) Figure 16 This needs to be explained.

[0102] With Get Figure 15 Similarly, multiple elastic wave devices are obtained by varying d / p, as shown in the example of the elastic wave device with resonant characteristics. Figure 16 This is a graph showing the relationship between d / p and the fractional bandwidth of the resonator as an elastic wave device.

[0103] according to Figure 16It is known that when d / p > 0.5, even with adjustments to d / p, the fractional bandwidth is less than 5%. Conversely, when d / p ≤ 0.5, varying d / p within this range allows for a fractional bandwidth exceeding 5%, enabling the construction of a resonator with a high coupling coefficient. Furthermore, when d / p is below 0.24, the fractional bandwidth can reach over 7%. Moreover, adjusting d / p within this range yields a resonator with an even wider fractional bandwidth, achieving a resonator with a higher coupling coefficient. Therefore, by setting d / p to below 0.5, a resonator with a high coupling coefficient utilizing the aforementioned thickness shear mode for bulk waves can be constructed.

[0104] Figure 17 This is a top view of an elastic wave device utilizing a thickness shear mode for bulk waves. In the elastic wave device 80, a pair of electrodes, having electrodes 3 and 4, are disposed on the first main surface 2a of the piezoelectric layer 2. It should be noted that... Figure 17 K in the figure represents the cross width. As described above, in the elastic wave device of the present invention, the number of electrode pairs can also be one pair. In this case, if the above d / p is 0.5 or less, it is also possible to effectively excite a bulk wave in the thickness shear mode.

[0105] In the elastic wave device 1, preferably, among the plurality of electrodes 3, 4, the metallization MR of any adjacent electrodes 3, 4 with respect to the excitation region C is expected to satisfy MR ≤ 1.75(d / p) + 0.075, where the excitation region C is the overlapping region when viewed along the direction opposite to the aforementioned adjacent electrodes 3, 4. In this case, stray emissions can be effectively reduced. (Refer to...) Figure 18 and Figure 19 This needs to be explained. Figure 18 This is a reference diagram illustrating an example of the resonant characteristics of the aforementioned elastic wave device 1. The stray signal indicated by arrow B occurs between the resonant frequency and the anti-resonant frequency. It should be noted that d / p = 0.08 and the Euler angles of LiNbO3 are set to (0°, 0°, 90°). Furthermore, the metallization rate MR is set to 0.35.

[0106] Reference Figure 11 (b) explains the metallization rate MR. Figure 11In the electrode configuration of (b), considering only a pair of electrodes 3 and 4, it is assumed that only this pair of electrodes 3 and 4 are provided. In this case, the portion enclosed by the single-dotted line is called the excitation region C. This excitation region C refers to the region in electrode 3 that coincides with electrode 4, the region in electrode 4 that coincides with electrode 3, and the region between electrode 3 and electrode 4 when viewed along a direction orthogonal to the length direction of electrodes 3 and 4, i.e., the opposing direction. Furthermore, the area of ​​electrodes 3 and 4 within the excitation region C relative to the area of ​​this excitation region C is called the metallization rate MR. That is, the metallization rate MR is the ratio of the area of ​​the metallized portion to the area of ​​the excitation region C.

[0107] It should be noted that when there are multiple pairs of electrodes, the ratio of the total area of ​​the metallized portion of the entire excitation region to the total area of ​​the excitation region can be set as MR.

[0108] Figure 19 This is a graph showing the relationship between the fractional bandwidth and the phase rotation of the stray impedance, normalized to 180 degrees, as in the case of multiple elastic wave resonators constructed according to this embodiment. It should be noted that various changes and adjustments were made to the piezoelectric layer thickness and electrode dimensions for the fractional bandwidth. Furthermore, Figure 19 This is the result when using a piezoelectric layer of LiNbO3 with Z-cut edges, but the same trend is also observed when using piezoelectric layers with other cut angles.

[0109] exist Figure 19 Within the region enclosed by ellipse J, the stray energy is as high as 1.0. According to... Figure 19 It can be seen that when the fractional bandwidth exceeds 0.17, i.e., exceeds 17%, even if the parameters constituting the fractional bandwidth are changed, larger spurious emissions with a spurious emission level of 1 or higher will still appear in the passband. That is, as... Figure 18 As shown in the resonance characteristics, the larger spurious emissions indicated by arrow B occur within the frequency band. Therefore, the fractional bandwidth is preferably 17% or less. In this case, the spurious emissions can be reduced by adjusting the thickness of the piezoelectric layer 2, the dimensions of the electrodes 3 and 4, etc.

[0110] Figure 20 This is a graph showing the relationship between d / 2p, metallization rate (MR), and fractional bandwidth. In the aforementioned elastic wave devices, various elastic wave devices with different d / 2p and MR were constructed, and the fractional bandwidth was measured. Figure 20The area indicated by the shaded line to the right of the dashed line D is the region with a fractional bandwidth of 17% or less. The boundary between the shaded area and the unshaded area is represented by MR = 3.5(d / 2p) + 0.075, that is, MR = 1.75(d / p) + 0.075. Therefore, it is preferable that MR ≤ 1.75(d / p) + 0.075. In this case, it is easier to make the fractional bandwidth 17% or less. More preferably... Figure 20 The region to the right of MR = 3.5(d / 2p) + 0.05 is shown by the single-dotted line D1. That is, if MR ≤ 1.75(d / p) + 0.05, the fractional bandwidth may reliably be below 17%.

[0111] Figure 21 This is a graph showing the mapping of fractional bandwidth relative to the Euler angles (0°, θ, ψ) of LiNbO3 when the d / p wireless is close to 0. Figure 21 The area shown by the shading is the region with a fractional bandwidth of at least 5%, and when approximating the range of this region, it becomes the range represented by the following equations (1), (2) and (3).

[0112] (0°±10°, 0°~20°, any ψ)…Equation (1)

[0113] (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°)…Equation (2)

[0114] (0°±10°,[180°-30°(1-(ψ-90) 2 / 8100) 1 / 2 ]~180°, any ψ)…Equation (3)

[0115] Therefore, within the Euler angle range of equations (1), (2), or (3) above, it is preferable to sufficiently broaden the fractional bandwidth. The same applies when the piezoelectric layer 2 is a lithium tantalate layer.

[0116] Figure 22 This is a partially truncated three-dimensional diagram used to illustrate an elastic wave device utilizing Lamb waves.

[0117] The elastic wave device 81 has a support substrate 82. A recess with an open upper surface is provided on the support substrate 82. A piezoelectric layer 83 is stacked on the support substrate 82, thus forming a cavity 9. Above the cavity 9, an IDT electrode 84 is provided on the piezoelectric layer 83. Reflectors 85 and 86 are provided on both sides of the IDT electrode 84 in the elastic wave propagation direction. Figure 22 In the diagram, the outer periphery of the cavity 9 is shown in dashed lines. Here, the IDT electrode 84 has a first busbar 84a, a second busbar 84b, and multiple first electrode fingers 84c and multiple second electrode fingers 84d. The multiple first electrode fingers 84c are connected to the first busbar 84a. The multiple second electrode fingers 84d are connected to the second busbar 84b. The multiple first electrode fingers 84c and multiple second electrode fingers 84d are interleaved and interlocked.

[0118] In the elastic wave device 81, an alternating electric field is applied to the IDT electrode 84 on the aforementioned cavity 9 to excite a Lamb wave, which is a plate wave. Furthermore, since reflectors 85 and 86 are provided on both sides, resonance characteristics based on the aforementioned Lamb wave can be obtained.

[0119] Thus, the elastic wave device of the present invention can also utilize plate waves. In this case, the piezoelectric layer described in the first to fourth embodiments and their variations is provided... Figure 22 The IDT electrode 84, reflector 85, and reflector 86 shown are sufficient.

[0120] In the elastic wave devices of the first to fourth embodiments and their modifications utilizing the thickness shear mode of the bulk wave, as described above, d / p is preferably 0.5 or less, more preferably 0.24 or less. This results in better resonance characteristics. Furthermore, in the elastic wave devices of the first to fourth embodiments and their modifications utilizing the thickness shear mode of the bulk wave, as described above, MR ≤ 1.75(d / p) + 0.075 is preferably satisfied. In this case, stray emissions can be suppressed more reliably.

[0121] In the elastic wave devices of the first to fourth embodiments and their variations utilizing thickness shear modes, the piezoelectric layer preferably comprises lithium niobate or lithium tantalate. Furthermore, the Euler angle of the lithium niobate or lithium tantalate constituting this piezoelectric layer (…) , θ, ψ) are preferably within the range of equation (1), equation (2) or equation (3) above. In this case, the fractional bandwidth can be sufficiently widened.

[0122] Explanation of reference numerals in the attached figures

[0123] 1…elastic wave device;

[0124] 2…piezoelectric layer;

[0125] 2a…First main face;

[0126] 2b…Second main face;

[0127] 3, 4… electrodes;

[0128] 5, 6… First busbar, Second busbar;

[0129] 7…Insulation layer;

[0130] 7a…through hole;

[0131] 8…supporting components;

[0132] 8a…through hole;

[0133] 9…cavity section;

[0134] 10…elastic wave device;

[0135] 12…Piezoelectric substrate;

[0136] 13…supporting components;

[0137] 13c…cavity section;

[0138] 13d, 13e… First peripheral region, second peripheral region;

[0139] 14…piezoelectric layer;

[0140] 14a, 14b... First principal face, second principal face;

[0141] 14c…membrane portion;

[0142] 15… Bonding layer;

[0143] 16...support base plate;

[0144] 17A, 17B... First insulating film, second insulating film;

[0145] 25…IDT electrode;

[0146] 26, 27… First busbar, Second busbar;

[0147] 28, 29… First electrode finger, second electrode finger;

[0148] 33A~33C… Supporting components;

[0149] 33c1~33c3…cavity section;

[0150] 33d, 33e… First peripheral edge, second peripheral edge;

[0151] 35A, 35C… bonding layers;

[0152] 36...support base plate;

[0153] 47…insulating film;

[0154] 47c…Connecting part;

[0155] 57…insulating film;

[0156] 57C…Third insulating film;

[0157] 66…dielectric film;

[0158] 80, 81… elastic wave devices;

[0159] 82...support base plate;

[0160] 83…piezoelectric layer;

[0161] 84…IDT electrode;

[0162] 84a, 84b... First busbar, Second busbar;

[0163] 84c, 84d… First electrode finger, second electrode finger;

[0164] 85, 86… reflectors;

[0165] 201… piezoelectric film;

[0166] 201a, 201b... First main face, second main face;

[0167] 451, 452… First incentive region, second incentive region;

[0168] C…incentive region;

[0169] F…intersection area;

[0170] VP1…Imaginary plane.

Claims

1. An elastic wave device, comprising: A support member having a support base plate; A piezoelectric layer is disposed on the support member; An IDT electrode, disposed on the piezoelectric layer, has a first busbar and a second busbar opposite to each other, and a plurality of electrode fingers; and A first insulating film is disposed on the piezoelectric layer and covers the tip ends of the plurality of electrode fingers opposite the first busbar. In the laminate of the support member and the piezoelectric layer, a void is provided at a position closer to the support member than the piezoelectric layer. In a top view, at least a portion of the IDT electrode overlaps with the void. When the direction in which the plurality of electrode fingers extend is defined as the electrode finger extension direction, in a top view, the outer periphery of the cavity includes a first outer periphery portion and a second outer periphery portion opposite to each other in the electrode finger extension direction, wherein the first outer periphery portion is located on the side of the first busbar. The first insulating film extends on the side of the first busbar and, in top view, overlaps with the first outer peripheral edge of the cavity. The elastic wave device also includes a second insulating film that covers the front ends of the plurality of electrode fingers opposite to the second busbar. The second insulating film extends on the side of the second busbar and overlaps with the second outer periphery of the cavity when viewed from above. When viewed along the direction in which the plurality of electrode fingers are arranged, the area where adjacent electrode fingers overlap is an intersection area, and the first insulating film and the second insulating film are not disposed in a portion of the intersection area.

2. The elastic wave device according to claim 1, wherein, The first insulating film and the second insulating film are integrated into one insulating film.

3. The elastic wave device according to claim 1, wherein, The first insulating film and the second insulating film are separate components.

4. The elastic wave device according to any one of claims 1 to 3, wherein, The first insulating film and the second insulating film are resin films.

5. The elastic wave device according to any one of claims 1 to 3, wherein, The first insulating film and the second insulating film are inorganic insulating films.

6. The elastic wave device according to any one of claims 1 to 3, wherein, The support member has a bonding layer disposed between the support substrate and the piezoelectric layer. The cavity is located in the bonding layer.

7. The elastic wave device according to any one of claims 1 to 3, wherein, The cavity is disposed on the support substrate.

8. The elastic wave device according to any one of claims 1 to 3, wherein, The elastic wave device utilizes plate waves.

9. The elastic wave device according to any one of claims 1 to 3, wherein, When the thickness of the piezoelectric layer is set to d and the center-to-center distance between adjacent electrodes is set to p, d / p is 0.5 or less.

10. The elastic wave device according to claim 9, wherein, d / p is below 0.

24.

11. The elastic wave device according to claim 9, wherein, When viewed along the direction of the arrangement of the plurality of electrode fingers, the area where adjacent electrode fingers overlap is the intersection region. When the metallization rate of the plurality of electrode fingers relative to the intersection region is set as MR, MR ≤ 1.75 (d / p) + 0.075 is satisfied.

12. The elastic wave device according to claim 9, wherein, The piezoelectric layer includes lithium niobate or lithium tantalate. The Euler angles (φ, θ, ψ) of the lithium niobate or lithium tantalate constituting the piezoelectric layer are within the range of the following equations (1), (2), or (3). (0°±10°, 0°~20°, any ψ) … Equation (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°] …Equation (2) (0°±10°, [180°-30° (1-(ψ-90)) 2 / 8100) 1 / 2 [180°, any ψ] … Equation (3).

13. The elastic wave device according to any one of claims 1 to 3, wherein, The piezoelectric layer includes lithium niobate or lithium tantalate.

Images