Elastic wave device

Abstract

An elastic wave device 10 comprises: a piezoelectric layer 4; a first comb-shaped electrode 7 that has a first bus bar 12 and a plurality of first electrode fingers 15; a second comb-shaped electrode 8 that has a second bus bar 13 and a plurality of second electrode fingers 16 which are interpolated in the plurality of first electrode fingers 15; and a third electrode 9 that has a plurality of third electrode fingers 17 which each are provided so as to be side by side with a first electrode finger 15 and a second electrode finger 16, and at least one third bus bar 14 which connects the plurality of third electrode fingers 17 together, and that is connected at a potential different from those of the first comb-shaped electrode 7 and the second comb-shaped electrode 8. The first electrode fingers 15, the second electrode fingers 16, and the third electrode fingers 17 are disposed such that, when starting with a first electrode finger 15, one cycle is constituted by a first electrode finger 15, a third electrode finger 17, a second electrode finger 16, and a third electrode finger 17 in this order. The third bus bar 14 and the plurality of first electrode fingers 15 are electrically insulated from each other. A through hole 4c is provided in a part of the piezoelectric layer 4 that is positioned between the first bus bar 12 and an intersecting region E of the first electrode fingers 15 and the second electrode fingers 16 and that is positioned between the first comb-shaped electrode 7 and the third electrode 9 in the direction orthogonal to the electrode fingers. This suppresses the occurrence of unwanted waves.

Description

Elastic Wave Device

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

[0002] Acoustic wave devices have traditionally been widely used in filters for mobile phones and the like. Recently, an acoustic wave device has been proposed as an acoustically coupled filter, as described in Patent Document 1 below. In an acoustically coupled filter, an electrode connected to a potential different from the input potential and the output potential, such as a reference potential, is disposed between an electrode connected to an input potential and an electrode connected to an output potential. With this configuration, a filter waveform can be generated even with a single acoustically coupled filter. Therefore, by reducing the number of elements, the filter device can be made more compact.

[0003] Japanese Patent Application Laid-Open No. 2023-190656

[0004] The present inventors have discovered that in an acoustic wave device serving as an acoustically coupled filter, miniaturization of the acoustic wave device itself can be promoted by three-dimensionally intersecting an electrode connected to an input potential with an electrode connected to a potential different from the input potential and the output potential. Furthermore, in the area where the electrodes intersect, an insulating layer is provided between the electrodes to electrically insulate them from each other.

[0005] However, the present inventors have found that with the above configuration, ripples may occur in the frequency characteristics of the elastic wave device, resulting in degradation of the filter characteristics.

[0006] An object of the present invention is to provide an acoustic wave device that can suppress deterioration of filter characteristics.

[0007] In one broad aspect, an elastic wave device according to the present invention includes a piezoelectric layer having a first main surface and a second main surface opposing each other; a first interdigital electrode provided on the first main surface of the piezoelectric layer, the first interdigital electrode having a first bus bar and a plurality of first electrode fingers, one ends of which are connected to the first bus bar; a second interdigital electrode provided on the first main surface of the piezoelectric layer, the second interdigital electrode having a second bus bar and a plurality of second electrode fingers, one ends of which are connected to the second bus bar and interdigitated with the plurality of first electrode fingers; a third electrode having a plurality of third electrode fingers provided on one of the first principal surface and the second principal surface of the piezoelectric layer so as to be aligned with the first electrode fingers and the second electrode fingers in a direction in which the first electrode fingers and the second electrode fingers are aligned, and at least one third bus bar connecting the plurality of third electrode fingers to each other, and connected to a potential different from that of the first comb electrode and the second comb electrode; the other of the comb-shaped electrode and the second comb-shaped electrode is connected to an output potential, the order in which the first electrode finger, the second electrode finger, and the third electrode finger are arranged is an order in which, starting from the first electrode finger, the first electrode finger, the third electrode finger, the second electrode finger, and the third electrode finger form one period, and when a direction orthogonal to a direction in which the first electrode finger, the second electrode finger, and the third electrode finger extend is defined as an electrode finger orthogonal direction, regions in which the first electrode finger and the second electrode finger overlap each other in the electrode finger orthogonal direction are intersecting a cross-section region, in which, in a planar view, one third bus bar is located between the cross-section region and the first bus bar, the third bus bar overlaps with the plurality of first electrode fingers in a planar view, the third bus bar and the plurality of first electrode fingers are electrically insulated, and a through hole is provided in at least a part of a portion of the piezoelectric layer that is located between the cross-section region and the first bus bar and that is located between the first comb electrode and the third electrode in a direction perpendicular to the electrode fingers.

[0008] In another broad aspect of the present invention, an elastic wave device includes: a piezoelectric layer having a first main surface and a second main surface opposing each other; a first interdigital electrode provided on the first main surface of the piezoelectric layer, the first interdigital electrode including a first bus bar and a plurality of first electrode fingers, each having one end connected to the first bus bar; a second interdigital electrode provided on the first main surface of the piezoelectric layer, the second interdigital electrode including a second bus bar and a plurality of second electrode fingers, each having one end connected to the second bus bar and interdigitated with the plurality of first electrode fingers; a third electrode having a plurality of third electrode fingers provided on one of the first principal surface and the second principal surface of the piezoelectric layer so as to be aligned with the first electrode fingers and the second electrode fingers in a direction in which the first electrode fingers and the second electrode fingers are aligned, and at least one third bus bar connecting the plurality of third electrode fingers to each other, and connected to a potential different from that of the first comb electrode and the second comb electrode, wherein one of the first comb electrode and the second comb electrode is connected to an input potential, and the other of the interdigital electrode and the second interdigital electrode is connected to an output potential, the order in which the first electrode finger, the second electrode finger, and the third electrode finger are arranged is an order in which, starting from the first electrode finger, the first electrode finger, the third electrode finger, the second electrode finger, and the third electrode finger form one period, and when a direction orthogonal to a direction in which the first electrode finger, the second electrode finger, and the third electrode finger extend is defined as an electrode finger orthogonal direction, an overlapping region of the first electrode finger and the second electrode finger in the electrode finger orthogonal direction intersects with each other a region, in which, in a planar view, the first bus bar is located between the intersection region and one of the third bus bars, the first bus bar overlaps with the plurality of third electrode fingers in a planar view, the first bus bar and the plurality of third electrode fingers are electrically insulated from each other, and a through hole is provided in at least a part of a portion of the piezoelectric layer that is located between the intersection region and the first bus bar and that is located between the first comb electrode and the third electrode in a direction perpendicular to the electrode fingers.

[0009] In yet another broad aspect of the present invention, an elastic wave device includes: a piezoelectric layer having a first main surface and a second main surface opposing each other; a first interdigital electrode provided on the first main surface of the piezoelectric layer, the first interdigital electrode having a first bus bar and a plurality of first electrode fingers, one ends of which are connected to the first bus bar; and a second interdigital electrode provided on the first main surface of the piezoelectric layer, the second interdigital electrode having a second bus bar and a plurality of second electrode fingers, one ends of which are connected to the second bus bar and interdigitated with the plurality of first electrode fingers, the second interdigital electrode having a front surface and a rear surface, the front surface being oriented in a plane direction such that the front surface is perpendicular to the plane direction. a plurality of third electrode fingers provided on the first main surface of the piezoelectric layer so as to be aligned with the first electrode fingers and the second electrode fingers in a direction in which the first electrode fingers and the second electrode fingers are aligned; a plurality of connection electrodes penetrating the piezoelectric layer and connected to the plurality of third electrode fingers, respectively; and at least one third bus bar provided on the second main surface and electrically connected to the plurality of third electrode fingers by the plurality of connection electrodes, and connected to a potential different from that of the first comb electrode and the second comb electrode; one of the first comb electrode and the second comb electrode is connected to an input potential, and the other of the first comb electrode and the second comb electrode is connected to an output potential; the first electrode finger, the second electrode finger, and the third electrode finger are arranged in an order such that, starting from the first electrode finger, the first electrode finger, the third electrode finger, the second electrode finger, and the third electrode finger form one period; and when a direction perpendicular to a direction in which the first electrode finger, the second electrode finger, and the third electrode finger extend is defined as an electrode finger perpendicular direction, the first electrode finger, the second electrode finger, and the third electrode finger form one period. A region where the first electrode fingers and the second electrode fingers overlap in the electrode finger orthogonal direction is an intersection region, and when viewed in a plane, one third bus bar is located between the intersection region and the first bus bar, and the third bus bar overlaps with the plurality of first electrode fingers in a plane view. A through hole is provided in at least a part of a portion of the piezoelectric layer that is located between the intersection region and the first bus bar and that is located between the first electrode fingers and the third electrode fingers in the electrode finger orthogonal direction.

[0010] In yet another broad aspect of the present invention, an elastic wave device includes: a piezoelectric layer having a first main surface and a second main surface opposing each other; a first interdigital electrode provided on the first main surface of the piezoelectric layer, the first interdigital electrode having a first bus bar and a plurality of first electrode fingers, one ends of which are connected to the first bus bar; a second interdigital electrode provided on the first main surface of the piezoelectric layer, the second interdigital electrode having a second bus bar and a plurality of second electrode fingers, one ends of which are connected to the second bus bar and interdigitated with the plurality of first electrode fingers; a third electrode having a plurality of third electrode fingers provided on the first main surface of the piezoelectric layer so as to be aligned with the first electrode fingers and the second electrode fingers in a direction in which the first electrode fingers and the second electrode fingers are aligned when viewed from above, a plurality of connection electrodes connected to the plurality of third electrode fingers, respectively, and a third bus bar electrically connected to the plurality of third electrode fingers by the plurality of connection electrodes, and connected to a potential different from that of the first comb electrode and the second comb electrode; and the second comb electrode is connected to an input potential, and the other of the first comb electrode and the second comb electrode is connected to an output potential, the order in which the first electrode finger, the second electrode finger, and the third electrode finger are arranged is an order in which, starting from the first electrode finger, the first electrode finger, the third electrode finger, the second electrode finger, and the third electrode finger form one period, and when a direction orthogonal to a direction in which the first electrode finger, the second electrode finger, and the third electrode finger extend is defined as an electrode finger orthogonal direction, The region where the first electrode fingers and the second electrode fingers overlap is an intersection region, and when viewed in a plane, one third bus bar is located between the intersection region and the first bus bar, and the third bus bar overlaps the plurality of first electrode fingers in a plane view. A through hole is provided in at least a part of the portion of the piezoelectric layer that is located between the intersection region and the first bus bar and that is located between the first electrode fingers and the third electrode fingers in a direction perpendicular to the electrode fingers.

[0011] According to an acoustic wave device according to a preferred embodiment of the present invention, deterioration of filter characteristics can be suppressed.

[0012] FIG. 1 is a schematic front cross-sectional view of an elastic wave device according to a first preferred embodiment of the present invention. FIG. 2 is a schematic plan view of an elastic wave device according to the first preferred embodiment of the present invention. FIG. 3 is a schematic cross-sectional view taken along line II-II in FIG. 2 . FIG. 4 is a schematic plan view of an elastic wave device according to a comparative example. FIG. 5 is a diagram illustrating transmission characteristics in the comparative example. FIG. 6 is a diagram illustrating transmission characteristics in the first preferred embodiment of the present invention. FIG. 7 is a schematic plan view of an elastic wave device according to a first modified example of the first preferred embodiment of the present invention. FIG. 8 is a schematic plan view of an elastic wave device according to a second modified example of the first preferred embodiment of the present invention. FIG. 9 is a schematic plan view of an elastic wave device according to a second preferred embodiment of the present invention. FIG. 10 is a schematic front cross-sectional view of an elastic wave device according to a modified example of the second preferred embodiment of the present invention, illustrating a portion where one first electrode finger and a third bus bar intersect with an insulator layer interposed therebetween. FIG. 11 is a schematic plan view of an elastic wave device according to a third preferred embodiment of the present invention. FIG. 12 is a schematic plan view of an elastic wave device according to a fourth preferred embodiment of the present invention. FIG. 13 is a schematic plan view of an elastic wave device according to a fifth preferred embodiment of the present invention. FIG. 14 is a schematic plan view of an elastic wave device according to a sixth preferred embodiment of the present invention. FIG. 15 is a schematic plan view of an elastic wave device according to a modified example of the sixth preferred embodiment of the present invention. FIG. 16 is a schematic plan view showing a portion of an elastic wave device according to a seventh preferred embodiment of the present invention. FIG. 17 is a schematic cross-sectional view taken along line III-III in FIG. 16. FIG. 18 is a diagram showing transmission characteristics according to the seventh preferred embodiment of the present invention. FIG. 19 is a schematic plan view of an elastic wave device according to an eighth preferred embodiment of the present invention. FIG. 20 is a schematic plan view of an elastic wave device according to a ninth preferred embodiment of the present invention. FIG. 21 is a schematic plan view of an elastic wave device according to a tenth preferred embodiment of the present invention. FIG. 22 is a schematic cross-sectional view taken along line IV-IV in FIG. 21. FIG. 23 is a schematic plan view of an elastic wave device according to an eleventh preferred embodiment of the present invention. FIG. 24 is a schematic cross-sectional view taken along line II in FIG. 23. FIG. 25 is a schematic cross-sectional view taken along line V-V in FIG. 23. 26 and 27 are schematic enlarged front cross-sectional views illustrating a portion of an elastic wave device according to a first modified example of an eleventh embodiment of the present invention and a portion of an elastic wave device according to a second modified example of the eleventh embodiment of the present invention.FIG. 28 is a schematic front cross-sectional view of an elastic wave device according to a twelfth preferred embodiment of the present invention. FIG. 29 is a schematic front cross-sectional view showing a magnified portion of an elastic wave device according to the twelfth preferred embodiment of the present invention. FIG. 30 is a schematic plan view showing an electrode configuration on a first main surface of a piezoelectric layer according to the twelfth preferred embodiment of the present invention. FIG. 31 is a schematic front cross-sectional view showing a magnified portion of an elastic wave device according to a first modified example of the twelfth preferred embodiment of the present invention. FIG. 32 is a schematic front cross-sectional view showing a magnified portion of an elastic wave device according to a second modified example of the twelfth preferred embodiment of the present invention. FIG. 33 is a schematic front cross-sectional view of an elastic wave device according to a thirteenth preferred embodiment of the present invention. FIG. 34 is a schematic front cross-sectional view showing a magnified portion of an elastic wave device according to the thirteenth preferred embodiment of the present invention. FIG. 35 is a schematic plan view showing an electrode configuration on a first main surface of a piezoelectric layer according to the thirteenth preferred embodiment of the present invention. FIG. 36 is a schematic front cross-sectional view showing a magnified portion of an elastic wave device according to a first modified example of the thirteenth preferred embodiment of the present invention. Fig. 37 is a schematic front cross-sectional view showing an enlarged portion of an elastic wave device according to a second modification of the thirteenth embodiment of the present invention. Fig. 38 is a schematic front cross-sectional view of an elastic wave device according to a fourteenth embodiment of the present invention. Fig. 39 is a schematic plan view of an elastic wave device according to a reference example. Fig. 40 is a diagram showing the relationship between d / p and the fractional bandwidth of an elastic wave device according to a reference example. Fig. 41 is a diagram showing the relationship between the fractional bandwidth and the normalized magnitude of spurious signals in an elastic wave device according to a reference example. Fig. 42 is a diagram showing the relationship between d / p, the metallization ratio MR, and the fractional bandwidth. Fig. 43 shows LiNbO when d / p is as close to 0 as possible. ３ FIG. 10 is a diagram showing a map of fractional bandwidths versus Euler angles (0°, θ, ψ) of the .

[0013] The present invention will be clarified below by describing specific embodiments of the present invention with reference to the drawings.

[0014] It should be noted that the embodiments described in this specification are merely examples, and partial substitution or combination of configurations is possible between different embodiments.

[0015] FIG. 1 is a schematic front cross-sectional view of an elastic wave device according to a first preferred embodiment of the present invention. FIG. 2 is a schematic plan view of an elastic wave device according to the first preferred embodiment. FIG. 1 is a schematic cross-sectional view taken along line II in FIG. 2. In FIG. 2, electrodes in a piezoelectric layer (described later) are indicated by hatching. Meanwhile, through-holes in a piezoelectric layer (described later) are indicated by cross-hatching. In FIG. 2, the reference potential symbol is used to schematically indicate that a third electrode (described later) is connected to the reference potential. Similarly, in schematic plan views other than FIG. 2, electrodes may be indicated by hatching, through-holes may be indicated by cross-hatching, and the reference potential symbol may be used.

[0016] 1 is configured to utilize bulk waves in thickness shear mode. The acoustic wave device 10 is an acoustically coupled filter. The configuration of the acoustic wave device 10 will be described below.

[0017] The acoustic wave device 10 includes a piezoelectric substrate 2 and a functional electrode 1. The piezoelectric substrate 2 is a substrate having piezoelectric properties. Specifically, the piezoelectric substrate 2 includes a support member 3 and a piezoelectric layer 4. In this embodiment, the support member 3 includes a support substrate 6 and an insulating layer 5. The insulating layer 5 is provided on the support substrate 6. The piezoelectric layer 4 is provided on the insulating layer 5. The configuration is not limited to the above, and the support member 3 may be composed of only the support substrate 6. Alternatively, the support member 3 may not necessarily be provided.

[0018] The piezoelectric layer 4 has a first main surface 4a and a second main surface 4b. The first main surface 4a and the second main surface 4b face each other. Of the first main surface 4a and the second main surface 4b, the second main surface 4b is located on the support member 3 side. A functional electrode 1 is provided on the first main surface 4a of the piezoelectric layer 4. In this specification, "provided on the first main surface 4a" includes both a case where the functional electrode 1 is provided directly on the first main surface 4a and a case where the functional electrode 1 is provided indirectly on the first main surface 4a via another member. In this embodiment, the functional electrode 1 is provided directly on the first main surface 4a.

[0019] 2 is provided in the piezoelectric layer 4 from the first principal surface 4a to the second principal surface 4b. In this embodiment, the through-hole 4c is not provided in the portion of the piezoelectric layer 4 where the functional electrode 1 is provided. Therefore, all portions of the functional electrode 1 are provided on the piezoelectric layer 4.

[0020] As shown in Fig. 2, the functional electrode 1 has a pair of comb electrodes and a third electrode 9. Specifically, the pair of comb electrodes is a first comb electrode 7 and a second comb electrode 8. The first comb electrode 7 is connected to an input potential. The second comb electrode 8 is connected to an output potential. In this embodiment, the third electrode 9 is connected to a reference potential. Therefore, in this embodiment, the third electrode 9 is a reference potential electrode.

[0021] The first comb electrode 7 may be connected to the output potential. The second comb electrode 8 may be connected to the input potential. In this way, the first comb electrode 7 may be connected to one of the input potential and the output potential. The second comb electrode 8 may be connected to the other of the input potential and the output potential. This configuration can also be applied to configurations of the present invention other than the first embodiment.

[0022] The third electrode 9 does not necessarily have to be connected to the reference potential, but may be connected to a potential different from that of the first comb electrode 7 and the second comb electrode 8. However, it is preferable that the third electrode 9 be connected to the reference potential.

[0023] The first comb electrode 7 and the second comb electrode 8 are provided on the first main surface 4a of the piezoelectric layer 4. More specifically, the first comb electrode 7 and the second comb electrode 8 are provided directly on the first main surface 4a. The first comb electrode 7 has a first bus bar 12 and a plurality of first electrode fingers 15. One ends of the plurality of first electrode fingers 15 are connected to the first bus bar 12. On the other hand, the second comb electrode 8 has a second bus bar 13 and a plurality of second electrode fingers 16. One ends of the plurality of second electrode fingers 16 are connected to the second bus bar 13.

[0024] The first bus bar 12 and the second bus bar 13 face each other. The first electrode fingers 15 and the second electrode fingers 16 are interdigitated with each other. The first electrode fingers 15 and the second electrode fingers 16 are alternately arranged in a direction perpendicular to the direction in which the first electrode fingers 15 and the second electrode fingers 16 extend.

[0025] The third electrode 9 has one third bus bar 14 and a plurality of third electrode fingers 17. In this embodiment, the plurality of third electrode fingers 17 and the third bus bar 14 are provided on the first main surface 4 a of the piezoelectric layer 4. More specifically, the plurality of third electrode fingers 17 are provided directly on the first main surface 4 a. The third bus bar 14 is provided directly on the first main surface 4 a with some exceptions. The plurality of third electrode fingers 17 are electrically connected to each other by the third bus bar 14.

[0026] More specifically, the third bus bar 14 includes a plurality of common connection portions 14 a and a bar portion 14 b. Adjacent pairs of third electrode fingers 17 are connected to each other by the common connection portion 14 a. The bar portion 14 b is provided over the plurality of common connection portions 14 a. Note that the third bus bar 14 does not necessarily have to include a plurality of common connection portions 14 a.

[0027] In a plan view, the plurality of third electrode fingers 17 are provided so as to be aligned with the first electrode fingers 15 and the second electrode fingers 16 in the direction in which the first electrode fingers 15 and the second electrode fingers 16 are aligned. Therefore, the first electrode fingers 15, the second electrode fingers 16, and the third electrode fingers 17 are aligned in one direction. The plurality of third electrode fingers 17 extend in parallel with the plurality of first electrode fingers 15 and the plurality of second electrode fingers 16.

[0028] In this specification, a plan view refers to a view from a direction corresponding to the top in Fig. 1, along the stacking direction of the support member 3 and the piezoelectric layer 4. In Fig. 1, for example, of the support substrate 6 side and the piezoelectric layer 4 side, the piezoelectric layer 4 side is the top. Furthermore, in this specification, a plan view is synonymous with a view from the principal surface opposing direction. The principal surface opposing direction is the direction in which the first principal surface 4a and the second principal surface 4b of the piezoelectric layer 4 face each other. More specifically, the principal surface opposing direction is, for example, the normal direction of the first principal surface 4a.

[0029] Hereinafter, the direction in which the first electrode fingers 15, the second electrode fingers 16, and the third electrode fingers 17 extend will be referred to as the electrode finger extension direction, and the direction perpendicular to the electrode finger extension direction will be referred to as the electrode finger orthogonal direction. In this embodiment, the electrode finger orthogonal direction is parallel to the direction in which the first bus bar 12, the second bus bar 13, and the third bus bar 14 extend. In this specification, the first electrode fingers 15, the second electrode fingers 16, and the third electrode fingers 17 may be collectively referred to simply as electrode fingers. The first bus bar 12, the second bus bar 13, and the third bus bar 14 may be collectively referred to simply as bus bars.

[0030] The order in which the multiple electrode fingers are arranged is such that, starting from the first electrode finger 15, one period consists of the first electrode finger 15, the third electrode finger 17, the second electrode finger 16, and the third electrode finger 17. Therefore, the order in which the multiple electrode fingers are arranged is the first electrode finger 15, the third electrode finger 17, the second electrode finger 16, the third electrode finger 17, the first electrode finger 15, the third electrode finger 17, the second electrode finger 16, and so on. If the input potential is represented by IN, the output potential is represented by OUT, and the reference potential is represented by GND, the order of the multiple electrode fingers is IN, GND, OUT, GND, IN, GND, OUT, and so on.

[0031] 2 , in the region where a plurality of electrode fingers are provided, the electrode fingers located at both ends in the direction perpendicular to the electrode fingers are both second electrode fingers 16. In this region, the electrode fingers located at the ends in the direction perpendicular to the electrode fingers may be any of the first electrode fingers 15, the second electrode fingers 16, and the third electrode fingers 17.

[0032] The configuration of the functional electrode 1, excluding the third electrode 9, is the same as that of an IDT (Interdigital Transducer) electrode. When viewed from the direction perpendicular to the electrode fingers, the region where adjacent first electrode fingers 15 and second electrode fingers 16 overlap is the intersection region E. However, it can also be said that the intersection region E is the region where adjacent first electrode fingers 15 and third electrode fingers 17, or adjacent second electrode fingers 16 and third electrode fingers 17, overlap when viewed from the direction perpendicular to the electrode fingers.

[0033] 2 , the third bus bar 14 of the third electrode 9 electrically connects the plurality of third electrode fingers 17 to each other. Specifically, the third bus bar 14 is located in the region between the intersection region E and the first bus bar 12. The plurality of first electrode fingers 15 are also located in this region. However, the third bus bar 14 and the plurality of first electrode fingers 15 are electrically insulated from each other by the plurality of insulator layers 19.

[0034] FIG. 3 is a schematic cross-sectional view taken along line II-II in FIG.

[0035] The insulator layer 19 is provided on the first main surface 4 a of the piezoelectric layer 4 so as to cover the first electrode fingers 15. More specifically, in this embodiment, one insulator layer 19 covers a part of one first electrode finger 15 in the electrode finger extension direction.

[0036] 2, a plurality of insulator layers 19 are arranged in the direction perpendicular to the electrode fingers. Each insulator layer 19 is provided so as to cover a portion of one of the first electrode fingers 15. On the other hand, the common connection portion 14a is not covered by the insulator layers 19. A bar portion 14b is provided on the first main surface 4a, extending over the plurality of insulator layers 19 and the plurality of common connection portions 14a.

[0037] In this way, the plurality of first electrode fingers 15 that are part of the first comb electrode 7 and the third bus bar 14 that are part of the third electrode 9 intersect with each other on the piezoelectric layer 4 via the insulator layer 19. In other words, the third bus bar 14 and the plurality of first electrode fingers 15 intersect with each other via the insulator layer 19. As a result, the third bus bar 14 and the plurality of first electrode fingers 15 are electrically insulated from each other. On the other hand, the third bus bar 14 electrically connects the plurality of third electrode fingers 17.

[0038] In this embodiment, the first electrode finger 15, the second electrode finger 16, and the third electrode finger 17 are made of laminated metal films. Specifically, in each electrode finger, a Ti layer, an Al layer, and a Ti layer are laminated in this order from the piezoelectric layer 4 side. Note that the material of each electrode finger is not limited to the above. Alternatively, each electrode finger may be made of a single-layer metal film.

[0039] In this embodiment, the third busbar 14 is located in the region between the intersection region E and the first busbar 12. In other words, the third busbar 14 is located in the region between the tips of the second electrode fingers 16 and the first busbar 12. Therefore, the tips of the second electrode fingers 16 each face the third busbar 14 across a gap in the electrode finger extension direction. On the other hand, the tips of the first electrode fingers 15 each face the second busbar 13 across a gap in the electrode finger extension direction.

[0040] The third bus bar 14 may be located in a region between the tips of the first electrode fingers 15 and the second bus bar 13. In this case, the tips of the first electrode fingers 15 face the third bus bar 14 across a gap. On the other hand, the tips of the second electrode fingers 16 face the first bus bar 12 across a gap.

[0041] 2, through holes 4c are provided in the piezoelectric layer 4. Specifically, a plurality of through holes 4c are provided in the piezoelectric layer 4 in a portion between the intersection region E and the first bus bar 12. The plurality of through holes 4c are provided in the piezoelectric layer 4 on both the intersection region E side and the first bus bar 12 side of the bar portion 14b of the third bus bar 14. However, the through holes 4c are not provided between the intersection region E and an imaginary line connecting the edge portions of the plurality of common connection portions 14a of the third bus bar 14 on the intersection region E side.

[0042] Some of all the through holes 4c, namely, the plurality of through holes 4c, are located in a portion of the piezoelectric layer 4 between the bar portion 14b of the third bus bar 14 and the intersection region E, in a portion between the plurality of first electrode fingers 15 and the plurality of common connection portions 14a of the third bus bar 14. The other plurality of through holes 4c are located in a portion of the piezoelectric layer 4 between the bar portion 14b and the first bus bar 12, in a portion between the plurality of first electrode fingers 15 and the plurality of common connection portions 14a and in a portion between the plurality of first electrode fingers 15 themselves.

[0043] The elastic wave device 10 is an elastic wave resonator configured to utilize thickness-shear mode bulk waves. As shown in FIG. 2 , the elastic wave device 10 has multiple excitation regions C. Elastic waves are excited in the multiple excitation regions C. Note that only two of the multiple excitation regions C are shown in FIG. 2 .

[0044] Of all the excitation regions C, some excitation regions C are regions where adjacent first electrode fingers 15 and third electrode fingers 17 overlap when viewed from the electrode finger orthogonal direction, and are regions between the centers of adjacent first electrode fingers 15 and third electrode fingers 17. The remaining excitation regions C are regions where adjacent second electrode fingers 16 and third electrode fingers 17 overlap when viewed from the electrode finger orthogonal direction, and are regions between the centers of adjacent second electrode fingers 16 and third electrode fingers 17. These excitation regions C are lined up in the electrode finger orthogonal direction. The intersection region E includes multiple excitation regions C. The intersection region E and excitation regions C are regions of the piezoelectric layer 4 that are defined based on the configuration of the functional electrode 1.

[0045] Acoustic wave device 10 is an acoustically coupled filter. Acoustic waves of multiple modes, including thickness-shear bulk waves, are excited in excitation region C located between the centers of adjacent first electrode finger 15 and third electrode finger 17 and excitation region C located between the centers of adjacent second electrode finger 16 and third electrode finger 17. By coupling these modes, a suitable filter waveform can be obtained even in a single acoustic wave device 10.

[0046] A feature of this embodiment is that through holes 4c are provided in at least a portion of the piezoelectric layer 4, which is located between the intersection region E and the first bus bar 12 and between the first interdigital electrode 7 and the third electrode 9 in the direction perpendicular to the electrode fingers. This makes it possible to suppress ripples in the frequency characteristics and to prevent deterioration of the filter characteristics. Details of this will be explained below by comparing this embodiment with a comparative example.

[0047] As shown in FIG. 4, the comparative example differs from the first embodiment in that the piezoelectric layer 204 does not have through-holes.

[0048] The transmission characteristics of the first preferred embodiment and the comparative example were compared. The design parameters of the elastic wave device 10 having the configuration of the first preferred embodiment are as follows. The design parameters of the comparative example were also the same as those of the first preferred embodiment.

[0049] Piezoelectric layer: Material... LiNbO ３ , Euler angles (φ, θ, ψ)...(0°, 0°, 90°), thickness...400 nm First to third electrode fingers: layer structure...Ti layer / Al layer / Ti layer from the piezoelectric layer side, thickness...10 nm / 390 nm / 4 nm from the piezoelectric layer side Center-to-center distance between the first electrode finger and the third electrode finger: 1.4 μm Center-to-center distance between the second electrode finger and the third electrode finger: 1.4 μm Duty ratio: 0.3

[0050] Fig. 5 is a diagram showing the transmission characteristics in a comparative example. Fig. 6 is a diagram showing the transmission characteristics in the first embodiment. Figs. 5 and 6 show the results of an FEM (Finite Element Method) simulation. The transmission characteristics are shown using S parameters.

[0051] As indicated by the arrows A in FIG. 5, large ripples occur within the passband in the frequency characteristics as the passband characteristics of the comparative example. These ripples are caused by unwanted waves. In contrast, as shown in FIG. 6, it can be seen that the ripples are suppressed in the passband characteristics of the first embodiment. In this way, in the first embodiment, it is possible to suppress the deterioration of the filter characteristics. The reason for this will be explained below.

[0052] 2, in the first embodiment, the common connection portion 14a of the third bus bar 14 is adjacent to the first electrode finger 15 in the direction perpendicular to the electrode finger. Therefore, the common connection portion 14a and the first electrode finger 15 are located outside the intersection region E, adjacent to each other in the direction perpendicular to the electrode finger, and are electrodes connected to different potentials. This is also true in the comparative example shown in FIG.

[0053] In the comparative example, the electrodes located outside the crossing region E, adjacent to each other in the direction perpendicular to the electrode fingers, and connected to different potentials are all provided on the piezoelectric layer 204, with the piezoelectric layer 204 located between these electrodes. In this case, unwanted waves are generated, deteriorating the filter characteristics.

[0054] In contrast, in the first embodiment shown in Fig. 2, through holes 4c are provided in the piezoelectric layer 4 in portions between the common connection portions 14a of the third bus bar 14 and the first electrode fingers 15. Therefore, the piezoelectric layer 4 is not located in these portions. This makes it difficult for unwanted waves to be generated, thereby suppressing deterioration of the filter characteristics.

[0055] The through holes 4c may be provided in at least a part of the portion of the piezoelectric layer 4 that is located between the intersection region E and the first bus bar 12 and that is located between the first comb electrode 7 and the third electrode 9 in the direction perpendicular to the electrode fingers. For example, the through holes 4c may be provided in at least a part of the portion between the plurality of common connection portions 14a of the third bus bar 14 and the plurality of first electrode fingers 15. In this case, as in the first embodiment, it is possible to suppress unwanted waves and prevent deterioration of the filter characteristics.

[0056] The configuration of the first embodiment will be described in further detail below.

[0057] As shown in FIG. 1 , a recess is provided in the insulating layer 5. A piezoelectric layer 4 is provided on the insulating layer 5 so as to close the recess. This forms a hollow portion. This hollow portion is the cavity 10a. In the first embodiment, the support member 3 and the piezoelectric layer 4 are arranged so that a portion of the support member 3 and a portion of the piezoelectric layer 4 face each other with the cavity 10a in between. However, the recess in the support member 3 may be provided across the insulating layer 5 and the support substrate 6. Alternatively, a recess provided only in the support substrate 6 may be closed by the insulating layer 5. The recess may be provided in the piezoelectric layer 4, for example. The cavity 10a may be a through-hole provided in the support member 3.

[0058] In the first embodiment, the cavity 10a does not overlap, in a plan view, the first bus bar 12, the second bus bar 13, and the third bus bar 14. Therefore, the first bus bar 12, the second bus bar 13, and the third bus bar 14 are supported by the support member 3 and the piezoelectric layer 4.

[0059] The cavity 10a is the acoustic reflector of the present invention. The acoustic reflector can effectively confine the energy of the elastic wave to the piezoelectric layer 4 side. The acoustic reflector may be provided at a position on the support member 3 that overlaps with at least a portion of the functional electrode 1 in a planar view. More specifically, at least a portion of each of the first electrode finger 15, the second electrode finger 16, and the third electrode finger 17 may overlap with the acoustic reflector in a planar view. It is preferable that a plurality of excitation regions C overlap with the acoustic reflector in a planar view.

[0060] The acoustic reflecting portion may be an acoustic reflecting film such as an acoustic multilayer film, which will be described later. For example, an acoustic reflecting film may be provided on the surface of the support member.

[0061] In the first embodiment, the center-to-center distance between the adjacent pairs of first electrode fingers 15 and third electrode fingers 17 is the same as the center-to-center distance between the adjacent pairs of second electrode fingers 16 and third electrode fingers 17. However, the center-to-center distance between the adjacent first electrode fingers 15 and third electrode fingers 17 and the center-to-center distance between the adjacent second electrode fingers 16 and third electrode fingers 17 do not have to be constant. In this case, the longest distance among the center-to-center distance between the adjacent first electrode fingers 15 and third electrode fingers 17 and the center-to-center distance between the adjacent second electrode fingers 16 and third electrode fingers 17 is defined as p. Note that when the center-to-center distance is constant, as in this embodiment, the center-to-center distance between any adjacent electrode fingers is distance p.

[0062] When the thickness of the piezoelectric layer 4 is d, d / p is preferably 0.5 or less, and more preferably 0.24 or less, so that bulk waves in thickness shear mode are suitably excited.

[0063] However, the elastic wave device of the present invention does not necessarily have to be configured to be capable of exciting bulk waves in thickness shear mode. For example, the elastic wave device of the present invention may be configured to be capable of exciting plate waves. In this case, the excitation region is the intersection region E shown in FIG. 2 .

[0064] The first embodiment shows an example of an aspect in which through holes 4c are provided in the piezoelectric layer 4. Below, first and second modified examples of the first embodiment will be shown, which differ from the first embodiment only in the positions where the through holes 4c are provided.

[0065] 7 , a plurality of through holes 4c are provided in the piezoelectric layer 4A in a portion that does not overlap with the plurality of first electrode fingers 15 but overlaps with the third bus bar 14 in a plan view. In addition, a plurality of through holes 4c are also provided in the piezoelectric layer 4A between the plurality of first electrode fingers 15 and the plurality of common connection portions 14a of the third bus bar 14. These through holes 4c reach the support member 3. Therefore, a portion of the third bus bar 14 is supported by the support member 3.

[0066] On the other hand, in this modification, no through hole 4c is provided between the first bus bar 12 and an imaginary line connecting the edge portions of the plurality of common connection portions 14a of the third bus bar 14 on the first bus bar 12 side. Note that each insulator layer 19 is provided on the first main surface 4a of the piezoelectric layer 4 so as to cover each first electrode finger 15.

[0067] In this modification and the first embodiment, the portions of the third busbar 14 other than those overlapping with the first electrode fingers 15 in a planar view are adjacent to the first electrode fingers 15 in the direction perpendicular to the electrode fingers. Therefore, the above-described portions of the third busbar 14 and the first electrode fingers 15 are electrodes located outside the intersection region E, adjacent to each other in the direction perpendicular to the electrode fingers, and connected to different potentials. In this modification, the third busbar 14, among the electrodes located outside the intersection region E, adjacent to each other in the direction perpendicular to the electrode fingers, and connected to different potentials, is not directly provided on the first main surface 4 a of the piezoelectric layer 4A. Specifically, a portion of the third busbar 14 is supported by the support member 3, and the remaining portion is indirectly provided on the first main surface 4 a via the insulating layer 19. This effectively suppresses unwanted waves and effectively prevents degradation of the filter characteristics.

[0068] In the second modified example shown in Figure 8, a plurality of through holes 4c are provided in the piezoelectric layer 4B, in a portion located between the intersection region E and the first bus bar 12, which does not overlap with the first electrode finger 15 and the third electrode finger 17 in a planar view.

[0069] Specifically, a plurality of through holes 4c are provided in the piezoelectric layer 4B in a portion located between the intersection region E and the third bus bar 14, and between the plurality of first electrode fingers 15 and the plurality of third electrode fingers 17. A plurality of through holes 4c are also provided in a portion of the piezoelectric layer 4B that does not overlap with the plurality of first electrode fingers 15 but overlaps with the third bus bar 14 in a plan view. In addition, a plurality of through holes 4c are also provided in the piezoelectric layer 4B between the plurality of first electrode fingers 15 and the plurality of common connection portions 14a of the third bus bar 14. Furthermore, a plurality of through holes 4c are also provided in a portion of the piezoelectric layer 4B that is located between the third bus bar 14 and the first bus bar 12, and between the plurality of first electrode fingers 15.

[0070] These through holes 4c reach the support member 3. Therefore, a portion of the third bus bar 14 is supported by the support member 3. Meanwhile, the first electrode fingers 15 and the third electrode fingers 17 are provided on the piezoelectric layer 4B. Each insulator layer 19 is provided on the first main surface 4a of the piezoelectric layer 4B so as to cover each first electrode finger 15.

[0071] In this modification, outside the intersection region E, any portion of the third bus bar 14 adjacent to the first comb electrode 7 in the direction perpendicular to the electrode fingers is not provided directly on the first main surface 4 a of the piezoelectric layer 4 B. In addition, a plurality of through holes 4 c are provided between the plurality of first electrode fingers 15 and the plurality of third electrode fingers 17. This makes it possible to further suppress unwanted waves and to further prevent deterioration of the filter characteristics.

[0072] The configurations of the first and second modified examples can also be applied to other configurations of the present invention in which a third bus bar 14 is provided between the intersection region E and the first bus bar 12. When the third bus bar 14 does not include the common connection portion 14a, the edge portion of the third bus bar 14 is the edge portion of the bar portion 14b.

[0073] FIG. 9 is a schematic plan view of an elastic wave device according to a second preferred embodiment of the present invention.

[0074] This embodiment differs from the first embodiment in that the third bus bar 24 in the functional electrode 21 does not include the common connection portion 14a shown in Fig. 2 and in the arrangement of the through holes 4c in the piezoelectric layer 4C. The third bus bar 24 is provided over the plurality of third electrode fingers 17 and the plurality of insulator layers 19. Except for the above points, the elastic wave device of this embodiment has a similar configuration to the elastic wave device 10 of the first embodiment.

[0075] A plurality of through holes 4c are provided in the piezoelectric layer 4C in a portion that does not overlap with the plurality of first electrode fingers 15 and the plurality of third electrode fingers 17 in plan view, but overlaps with the third bus bar 24. In addition, a plurality of through holes 4c are also provided in a portion of the piezoelectric layer 4C that is located between the third bus bar 24 and the first bus bar 12, and between the plurality of first electrode fingers 15.

[0076] These through holes 4c reach the support member 3. Therefore, a portion of the third bus bar 24 is supported by the support member 3. Meanwhile, the first electrode fingers 15 and the third electrode fingers 17 are provided on the piezoelectric layer 4C. Each insulator layer 19 is provided on the first main surface 4a of the piezoelectric layer 4C so as to cover each first electrode finger 15.

[0077] The portions of the third busbar 24 other than those overlapping with the first electrode fingers 15 in a planar view are adjacent to the first electrode fingers 15 in the direction perpendicular to the electrode fingers. Therefore, the above-described portions of the third busbar 24 and the first electrode fingers 15 are electrodes located outside the intersection region E, adjacent to each other in the direction perpendicular to the electrode fingers, and connected to different potentials. In this embodiment, the third busbar 24, among the electrodes located outside the intersection region E, adjacent to each other in the direction perpendicular to the electrode fingers, and connected to different potentials, is not directly provided on the first main surface 4 a of the piezoelectric layer 4C. In addition, a through hole 4 c is provided between the first electrode fingers 15 and the third electrode fingers 17 in the piezoelectric layer 4C. This effectively suppresses unwanted waves and effectively prevents degradation of the filter characteristics.

[0078] In this embodiment, in the portion where the third bus bar 24 is laminated with the insulator layer 19 and the first electrode fingers 15, the first electrode fingers 15, the insulator layer 19, and the third bus bar 24 are laminated in this order from the piezoelectric layer 4C side. However, the order in which the first electrode fingers 15, the insulator layer 19, and the third bus bar 24 are laminated is not limited to the above.

[0079] 10 , in a portion where the third bus bar 24 is laminated with the insulator layer 19 and the first electrode finger 15, the third bus bar 24, the insulator layer 19, and the first electrode finger 15 are laminated in this order from the piezoelectric layer 4C side. More specifically, one insulator layer 19 is provided between the third bus bar 24 and one first electrode finger 15.

[0080] A plurality of insulator layers 19 are provided on the third bus bar 24. The plurality of insulator layers 19 are arranged in a direction perpendicular to the electrode fingers. Each insulator layer 19 is located between the third bus bar 24 and one of the first electrode fingers 15. This electrically insulates the first comb electrode 7 and the third electrode 29. The configuration in this modified example where electrodes connected to different potentials cross each other via an insulator layer 19 can also be applied to configurations of the present invention other than this modified example.

[0081] In this modification, as in the second embodiment, it is possible to effectively suppress unwanted waves and effectively prevent deterioration of filter characteristics.

[0082] FIG. 11 is a schematic plan view of an elastic wave device according to a third preferred embodiment of the present invention.

[0083] This embodiment differs from the second embodiment in the configuration of the functional electrode 31 and the position of the through-hole 4 c in the piezoelectric layer 4 D. Except for the above points, the elastic wave device of this embodiment has the same configuration as the elastic wave device of the second embodiment.

[0084] In the functional electrode 31, the third bus bar 24 is located in the region between the intersection region E and the second bus bar 13. In other words, the third bus bar 24 is located in the region between the tips of the plurality of first electrode fingers 15 and the second bus bar 13. Therefore, the tips of the plurality of first electrode fingers 15 each face the third bus bar 24 across a gap in the electrode finger extension direction. On the other hand, the tips of the plurality of second electrode fingers 16 each face the first bus bar 12 across a gap in the electrode finger extension direction.

[0085] A plurality of through holes 4c are provided in the piezoelectric layer 4D in a portion that does not overlap with the plurality of second electrode fingers 16 and the plurality of third electrode fingers 17 in plan view, but overlaps with the third bus bar 24. In addition, a plurality of through holes 4c are also provided in a portion of the piezoelectric layer 4D that is located between the third bus bar 24 and the second bus bar 13, and that is located between the plurality of second electrode fingers 16.

[0086] These through holes 4c reach the support member 3. Therefore, a portion of the third bus bar 24 is supported by the support member 3. Meanwhile, the second electrode fingers 16 and the third electrode fingers 17 are provided on the piezoelectric layer 4D. Each insulator layer 19 is provided on the first main surface 4a of the piezoelectric layer 4D so as to cover each second electrode finger 16.

[0087] The portions of the third busbar 24 other than those overlapping with the second electrode fingers 16 in a planar view are adjacent to the second electrode fingers 16 in the direction perpendicular to the electrode fingers. Therefore, the above-described portions of the third busbar 24 and the second electrode fingers 16 are electrodes located outside the intersection region E, adjacent to each other in the direction perpendicular to the electrode fingers, and connected to different potentials. In this embodiment, the third busbar 24, among the electrodes located outside the intersection region E, adjacent to each other in the direction perpendicular to the electrode fingers, and connected to different potentials, is not directly provided on the first main surface 4 a of the piezoelectric layer 4D. In addition, a through hole 4 c is provided between the second electrode fingers 16 and the third electrode fingers 17 in the piezoelectric layer 4D. This effectively suppresses unwanted waves and effectively prevents degradation of the filter characteristics.

[0088] In the functional electrode 31, the second electrode fingers 16 of the second comb electrode 8 are connected to the output potential. The third bus bar 24 of the third electrode 29 is connected to the reference potential. Therefore, in the portion overlapping with the third bus bar 24 in plan view, the electrode connected to the output potential and the electrode connected to the reference potential are adjacent in the direction perpendicular to the electrode fingers. On the other hand, in the second embodiment shown in FIG. 9 , in the portion overlapping with the third bus bar 24 in plan view, the electrode connected to the input potential and the electrode connected to the reference potential are adjacent in the direction perpendicular to the electrode fingers.

[0089] In the third embodiment, the second comb electrode 8 may be connected to an input potential, and the first comb electrode 7 may be connected to an output potential. In this case, the configuration of the third embodiment is equivalent to the configuration of the second embodiment in which the first comb electrode is connected to an input potential, and the second comb electrode 8 is connected to an output potential. Similarly, in the second embodiment, the first comb electrode 7 may be connected to an output potential, and the second comb electrode 8 may be connected to an input potential. In this case, the configuration of the second embodiment is equivalent to the configuration of the third embodiment in which the second comb electrode 8 is connected to an output potential, and the first comb electrode 7 is connected to an input potential.

[0090] Note that a through hole 4c may be provided in a portion of the piezoelectric layer 4D that is located between the intersection region E and the second bus bar 13, and that is located between the second electrode finger 16 and the third electrode finger 17 in the electrode finger-orthogonal direction. More specifically, a through hole 4c may be provided in a portion that is located between the intersection region E and the third bus bar 24, and that is located between the second electrode finger 16 and the third electrode finger 17 in the electrode finger-orthogonal direction. This makes it possible to effectively suppress spurious waves. This configuration can also be applied to configurations of the present invention other than the third embodiment, in which the third bus bar 24 is provided between the intersection region E and the second bus bar 13.

[0091] FIG. 12 is a schematic plan view of an elastic wave device according to a fourth preferred embodiment of the present invention.

[0092] This embodiment differs from the second embodiment in that the third electrode 49 includes two third bus bars 44A and three third bus bars 44B. The third electrode 49 has a grating shape. This embodiment also differs from the second embodiment in the positions of the multiple insulator layers 19. This embodiment also differs from the second embodiment in the positions of the through holes 4c in the piezoelectric layer 4E. Except for the above points, the elastic wave device of this embodiment has the same configuration as the elastic wave device of the second embodiment.

[0093] Some of the insulator layers 19 are provided on the first main surface 4 a of the piezoelectric layer 4E so as to cover a portion of each of the first electrode fingers 15. The remaining insulator layers 19 are provided on the first main surface 4 a of the piezoelectric layer 4E so as to cover a portion of each of the second electrode fingers 16.

[0094] One third bus bar 44A is located between the intersection region E and the first bus bar 12. The third bus bar 44A overlaps with the plurality of first electrode fingers 15 in a plan view. More specifically, the third bus bar 44A intersects with the plurality of first electrode fingers 15 via an insulator layer 19. As a result, the third bus bar 44A and the plurality of first electrode fingers 15 are electrically insulated from each other. On the other hand, the third bus bar 44A electrically connects the plurality of third electrode fingers 17.

[0095] The other third bus bar 44B is located between the intersection region E and the second bus bar 13. The third bus bar 44B overlaps with the plurality of second electrode fingers 16 in a plan view. More specifically, the third bus bar 44B intersects with the plurality of second electrode fingers 16 via the insulator layer 19. As a result, the third bus bar 44B and the plurality of second electrode fingers 16 are electrically insulated from each other. On the other hand, the third bus bar 44B electrically connects the plurality of third electrode fingers 17.

[0096] In the piezoelectric layer 4E, some of all the through holes 4c are arranged in the same manner as in the second embodiment. Specifically, the plurality of through holes 4c are provided in portions of the piezoelectric layer 4E that do not overlap with the plurality of first electrode fingers 15 and the plurality of third electrode fingers 17 in a plan view, but overlap with the third bus bar 44A. In addition, the plurality of through holes 4c are also provided in portions of the piezoelectric layer 4E that are located between the third bus bar 44A and the first bus bar 12, and between the plurality of first electrode fingers 15.

[0097] The other plurality of through holes 4c are provided in portions of the piezoelectric layer 4E that do not overlap with the plurality of second electrode fingers 16 and the plurality of third electrode fingers 17 in plan view, but overlap with the third bus bar 44B. In addition, a plurality of through holes 4c are also provided in portions of the piezoelectric layer 4E that are located between the third bus bar 44B and the second bus bar 13, and between the plurality of second electrode fingers 16.

[0098] These through holes 4c reach the support member 3. Therefore, a portion of the third bus bar 44A and a portion of the third bus bar 44B are supported by the support member 3. On the other hand, the plurality of first electrode fingers 15, the plurality of second electrode fingers 16, and the plurality of third electrode fingers 17 are provided on the piezoelectric layer 4E.

[0099] The portion of one third busbar 44A other than the portion overlapping with the first electrode finger 15 in plan view is adjacent to the first electrode finger 15 in the electrode finger orthogonal direction. The above portion of the third busbar 44A and the first electrode finger 15 are located outside the intersection region E, adjacent to each other in the electrode finger orthogonal direction, and are electrodes connected to different potentials. The portion of the other third busbar 44B other than the portion overlapping with the second electrode finger 16 in plan view is adjacent to the second electrode finger 16 in the electrode finger orthogonal direction. The above portion of the third busbar 44B and the second electrode finger 16 are located outside the intersection region E, adjacent to each other in the electrode finger orthogonal direction, and are electrodes connected to different potentials.

[0100] In this embodiment, the third bus bar 44A and the third bus bar 44B are not provided directly on the first main surface 4a of the piezoelectric layer 4E. In addition, through holes 4c are provided in the piezoelectric layer 4E between the first electrode finger 15 and the third electrode finger 17, and between the second electrode finger 16 and the third electrode finger 17. This makes it possible to effectively suppress unwanted waves and effectively prevent deterioration of the filter characteristics.

[0101] It is sufficient that the through holes 4c are provided in at least a part of the portion of the piezoelectric layer 4E that is located between the intersection region E and the first bus bar 12 and that is located between the first comb electrode 7 and the third electrode 49 in the electrode finger orthogonal direction. In this case, the first electrode fingers 15 may be connected to either the input potential or the output potential. In addition, it is preferable that the through holes 4c are also provided in at least a part of the portion of the piezoelectric layer 4E that is located between the intersection region E and the second bus bar 13 and that is located between the second comb electrode 8 and the third electrode 49 in the electrode finger orthogonal direction. This makes it possible to more reliably and effectively suppress unwanted waves.

[0102] FIG. 13 is a schematic plan view of an elastic wave device according to a fifth preferred embodiment of the present invention.

[0103] This embodiment differs from the fourth embodiment in the positional relationship between the second interdigital electrode 8 and the third electrode 49. This embodiment also differs from the fourth embodiment in the position of the through-holes 4c in the piezoelectric layer 4F. This embodiment also differs from the fourth embodiment in the arrangement of the insulator layer 19. Except for the above points, the elastic wave device of this embodiment has the same configuration as the elastic wave device of the fourth embodiment.

[0104] In a plan view, the second bus bar 13 is located between the intersection region E and the third bus bar 44B. In other words, the third bus bar 44B is arranged so as to sandwich the second bus bar 13 together with the intersection region E. The second bus bar 13 overlaps with the plurality of third electrode fingers 17 in a plan view. The second bus bar 13 and the plurality of third electrode fingers 17 are electrically insulated from each other by the insulator layer 19.

[0105] Specifically, the insulator layers 19 are provided on the first main surface 4 a of the piezoelectric layer 4F so as to cover the third electrode fingers 17. More specifically, one insulator layer 19 covers a portion of one third electrode finger 17 in the electrode finger extension direction. The multiple insulator layers 19 are aligned in the direction orthogonal to the electrode fingers. Each insulator layer 19 is provided so as to cover a portion of one third electrode finger 17. A second bus bar 13 is provided on the first main surface 4 a, spanning over the multiple insulator layers 19.

[0106] In this manner, the third electrode fingers 17, which are part of the third electrode 49, and the second bus bar 13, which is part of the second comb electrode 8, intersect with each other on the piezoelectric layer 4F via the insulator layer 19. This electrically insulates the second bus bar 13 and the third electrode fingers 17 from each other. Note that the third bus bar 44A and the first electrode fingers 15 intersect with each other via the insulator layer 19, as in the fourth embodiment.

[0107] In the piezoelectric layer 4F, some of all the through holes 4c are arranged in the same manner as the through holes 4c on the first bus bar 12 side in the second and fourth embodiments. The other through holes 4c are provided in portions of the piezoelectric layer 4F that do not overlap with the third electrode fingers 17 in plan view but overlap with the second bus bar 13. In addition, a plurality of through holes 4c are also provided in portions of the piezoelectric layer 4F that are located between the second bus bar 13 and the third bus bar 44B and between the third electrode fingers 17.

[0108] These through holes 4c reach the support member 3. Therefore, the third bus bar 44A and a portion of the second bus bar 13 are supported by the support member 3. On the other hand, the plurality of first electrode fingers 15, the plurality of second electrode fingers 16, and the plurality of third electrode fingers 17 are provided on the piezoelectric layer 4F.

[0109] In this embodiment, the portion of the second busbar 13 other than the portion overlapping with the third electrode finger 17 in plan view is adjacent to the third electrode finger 17 in the electrode finger orthogonal direction. The above portion of the second busbar 13 and the third electrode finger 17 are located outside the intersection region E, adjacent to each other in the electrode finger orthogonal direction, and are electrodes connected to different potentials. On the other hand, as in the fourth embodiment, the portion of the third busbar 44A other than the portion overlapping with the first electrode finger 15 in plan view is adjacent to the first electrode finger 15 in the electrode finger orthogonal direction. The above portion of the third busbar 44A and the first electrode finger 15 are located outside the intersection region E, adjacent to each other in the electrode finger orthogonal direction, and are electrodes connected to different potentials.

[0110] In this embodiment, the third bus bar 44A and the second bus bar 13 are not provided directly on the first main surface 4a of the piezoelectric layer 4F, which makes it possible to effectively suppress unwanted waves and effectively prevent deterioration of the filter characteristics.

[0111] In the functional electrode 41A, the second bus bar 13 is provided between the intersection region E and the third bus bar 44B. The first bus bar 12 may be provided between the intersection region E and the third bus bar 44A.

[0112] FIG. 14 is a schematic plan view of an elastic wave device according to a sixth preferred embodiment of the present invention.

[0113] This embodiment differs from the fifth embodiment in the positional relationship between the first comb electrode 7 and the third electrode 49. This embodiment also differs from the fifth embodiment in the position of the through-holes 4c in the piezoelectric layer 4G. This embodiment also differs from the fifth embodiment in the arrangement of the insulator layer 19. Except for the above points, the elastic wave device of this embodiment has the same configuration as the elastic wave device of the fifth embodiment.

[0114] The first bus bar 12 is located between the intersection region E and the third bus bar 44A. In other words, the third bus bar 44A is arranged to sandwich the first bus bar 12 together with the intersection region E. The first bus bar 12 overlaps with the plurality of third electrode fingers 17 in a plan view. The first bus bar 12 and the plurality of third electrode fingers 17 are electrically insulated from each other by an insulator layer 19.

[0115] Specifically, the insulator layers 19 are provided on the first main surface 4 a of the piezoelectric layer 4G so as to cover the third electrode fingers 17. More specifically, one insulator layer 19 covers a portion of one third electrode finger 17 in the electrode finger extension direction. The multiple insulator layers 19 are aligned in the direction orthogonal to the electrode fingers. Each insulator layer 19 is provided so as to cover a portion of one third electrode finger 17. A first bus bar 12 is provided on the first main surface 4 a, spanning over the multiple insulator layers 19.

[0116] In this manner, the plurality of third electrode fingers 17 that are part of the third electrode 49 and the first bus bar 12 that are part of the first comb electrode 7 intersect with each other on the piezoelectric layer 4G via the insulator layer 19. This electrically insulates the first bus bar 12 and the plurality of third electrode fingers 17 from each other. Note that the second bus bar 13 and the plurality of third electrode fingers 17 intersect with each other via the insulator layer 19, as in the fifth embodiment.

[0117] In the piezoelectric layer 4G, some of all the through holes 4c are provided in portions of the piezoelectric layer 4G that do not overlap with the third electrode fingers 17 in plan view but overlap with the first bus bar 12. In addition, a plurality of through holes 4c are also provided in portions of the piezoelectric layer 4G that are located between the first bus bar 12 and the third bus bar 44A and between the third electrode fingers 17. The remaining plurality of through holes 4c are arranged in the same manner as the plurality of through holes 4c on the second bus bar 13 side in the fifth embodiment.

[0118] These through holes 4c reach the support member 3. Therefore, a portion of the first bus bar 12 and a portion of the second bus bar 13 are supported by the support member 3. On the other hand, the plurality of first electrode fingers 15, the plurality of second electrode fingers 16, and the plurality of third electrode fingers 17 are provided on the piezoelectric layer 4G.

[0119] In this embodiment, the portion of the first busbar 12 other than the portion overlapping with the third electrode finger 17 in plan view is adjacent to the third electrode finger 17 in the electrode finger orthogonal direction. The above portion of the first busbar 12 and the third electrode finger 17 are located outside the intersection region E, adjacent to each other in the electrode finger orthogonal direction, and are electrodes connected to different potentials. On the other hand, as in the fifth embodiment, the portion of the second busbar 13 other than the portion overlapping with the third electrode finger 17 in plan view is adjacent to the third electrode finger 17 in the electrode finger orthogonal direction. The above portion of the second busbar 13 and the third electrode finger 17 are located outside the intersection region E, adjacent to each other in the electrode finger orthogonal direction, and are electrodes connected to different potentials.

[0120] In this embodiment, the first bus bar 12 and the second bus bar 13 are not provided directly on the first main surface 4 a of the piezoelectric layer 4 G. This makes it possible to effectively suppress unwanted waves and effectively prevent deterioration of the filter characteristics.

[0121] The arrangement of the through holes 4c in the piezoelectric layer 4G is not limited to the above. Below, a modified example of the sixth embodiment will be shown, which differs from the sixth embodiment only in the arrangement of the through holes 4c. In the modified example of the sixth embodiment, as in the sixth embodiment, unwanted waves can be effectively suppressed and deterioration of the filter characteristics can be effectively suppressed.

[0122] 15 , a plurality of through holes 4c are provided in a portion of the piezoelectric layer 4H that is located between the intersection region E and the first bus bar 12, and that is located between the plurality of first electrode fingers 15 and the plurality of third electrode fingers 17. This configuration can also be applied to other configurations of the present invention in which the first bus bar 12 is provided between the intersection region E and the third bus bar 44A.

[0123] A plurality of through holes 4c are provided in a portion of the piezoelectric layer 4H that is located between the intersection region E and the second bus bar 13, and that is located between the plurality of second electrode fingers 16 and the plurality of third electrode fingers 17. This configuration can also be applied to other configurations of the present invention in which the second bus bar 13 is provided between the intersection region E and the third bus bar 44B. In this modification, the remaining plurality of through holes 4c are provided in the same manner as in the sixth embodiment.

[0124] In this modification, outside the intersection region E, any portion of the third bus bar 44A adjacent to the first comb electrode 7 in the direction orthogonal to the electrode fingers is not provided directly on the first main surface 4a of the piezoelectric layer 4H. Similarly, outside the intersection region E, any portion of the third bus bar 44B adjacent to the second comb electrode 8 in the direction orthogonal to the electrode fingers is not provided directly on the first main surface 4a of the piezoelectric layer 4H. In addition, a plurality of through holes 4c are provided between the plurality of first electrode fingers 15 and the plurality of third electrode fingers 17, and between the plurality of second electrode fingers 16 and the plurality of third electrode fingers 17. This makes it possible to further suppress unwanted waves and to further prevent deterioration of the filter characteristics.

[0125] It is sufficient that the through hole 4c is provided in at least a part of the portion of the piezoelectric layer 4H that is located between the intersection region E and the first bus bar 12 and that is located between the first comb electrode 7 and the third electrode 49 in the direction perpendicular to the electrode fingers. For example, at least one through hole 4c may be provided only in at least a part of the portion of the piezoelectric layer 4H that is located between the plurality of first electrode fingers 15 and the plurality of third electrode fingers 17.

[0126] Alternatively, the through hole 4c may be provided in at least a part of the portion of the piezoelectric layer 4H that is located between the intersection region E and the second bus bar 13 and that is located between the second comb electrode 8 and the third electrode 49 in the direction perpendicular to the electrode fingers. For example, at least one through hole 4c may be provided only in at least a part of the portion of the piezoelectric layer 4H that is located between the plurality of second electrode fingers 16 and the plurality of third electrode fingers 17.

[0127] Fig. 16 is a schematic plan view showing a portion of an elastic wave device according to a seventh preferred embodiment of the present invention. Fig. 17 is a schematic cross-sectional view taken along line III-III in Fig. 16. Note that in Fig. 16, the insulator layer 19 is indicated by hatching.

[0128] As shown in Fig. 16 , this embodiment differs from the first embodiment in the configuration of the functional electrode 51. As shown in Fig. 17 , this embodiment also differs from the first embodiment in that the support member 53 is composed of only a support substrate. Returning to Fig. 16 , this embodiment also differs from the first embodiment in the position of the through-hole 4c in the piezoelectric layer 4I. Except for the above points, the elastic wave device of this embodiment has a similar configuration to the elastic wave device 10 of the first embodiment.

[0129] In the first comb-shaped electrode 57 of the functional electrode 51, the width of the first electrode finger 55 is not constant. Specifically, the portion of the first electrode finger 55 located outside the intersection region E has a wide portion and a narrow portion. More specifically, the wide portion of the first electrode finger 55 is located on the first bus bar 12 side. On the other hand, the narrow portion of the first electrode finger 55 is located on the intersection region E side. The width of the narrow portion of the first electrode finger 55 is the same as the width of the portion of the first electrode finger 55 located in the intersection region E. Note that the width of the electrode finger is the dimension of the electrode finger in the direction perpendicular to the electrode finger.

[0130] Similarly, the portion of the second electrode finger 56 of the second comb-shaped electrode 58 located outside the intersection region E also has a wide portion and a narrow portion. The wide portion of the second electrode finger 56 is located on the second bus bar 13 side. The narrow portion of the second electrode finger 56 is located on the intersection region E side. The width of the narrow portion of the second electrode finger 56 is the same as the width of the portion of the second electrode finger 56 located in the intersection region E.

[0131] The third electrode 59 has two third bus bars 54A and 54B. Each third bus bar has a plurality of common connection portions 54a and bar portions 54b. The plurality of common connection portions 54a of one third bus bar 54A extend toward the intersection region E. The plurality of common connection portions 54a of the other third bus bar 54B also extend toward the intersection region E. Note that none of the common connection portions 54a reach the intersection region E. The common connection portions 54a of the third bus bar 54A and the common connection portions 54a of the third bus bar 54B each connect adjacent pairs of third electrode fingers 17 to each other.

[0132] The common connection portions 54a of one third bus bar 54A, the common connection portions 54a of the other third bus bar 54B, and the third electrode fingers 17 are connected in a meandering pattern. Specifically, two adjacent third electrode fingers 17 connected to two adjacent common connection portions 54a of one third bus bar 54A are connected to one common connection portion 54a of the other third bus bar 54B. Similarly, two adjacent third electrode fingers 17 connected to two adjacent common connection portions 54a of the third bus bar 54B are connected to one common connection portion 54a of the third bus bar 54A.

[0133] The common connection portions 54a in one third bus bar 54A are connected by bar portions 54b. The width of each common connection portion 54a is not uniform. Specifically, the common connection portion 54a has a wide portion and a narrow portion. The narrow portion of the common connection portion 54a is located closer to the bar portion 54b than the wide portion. Therefore, a pair of third electrode fingers 17 are connected to the wide portion of the common connection portion 54a. Note that the width of the common connection portion 54a in this embodiment is the dimension along the direction perpendicular to the electrode fingers of the common connection portion 54a.

[0134] The bar portion 54b of the third bus bar 54A and the plurality of first electrode fingers 55 overlap in a plan view. In this embodiment, a strip-shaped insulator layer 19 is provided on the first main surface 4a of the piezoelectric layer 4I so as to cover a portion of each of the plurality of first electrode fingers 55. The bar portion 54b is provided on the insulator layer 19. This electrically insulates the first comb-shaped electrode 57 and the third electrode 59 from each other. The wider portion of each first electrode finger 55 extends beyond the insulator layer 19 toward the crossing region E.

[0135] The multiple common connection portions 54a of the other third bus bar 54B are connected by bar portions 54b. The width of each common connection portion 54a is not uniform. Each common connection portion 54a has a wide portion and a narrow portion. The narrow portion of the common connection portion 54a is located closer to the bar portion 54b than the wide portion. Therefore, a pair of third electrode fingers 17 is connected to the wide portion of the common connection portion 54a.

[0136] The bar portion 54b of the third bus bar 54B and the plurality of second electrode fingers 56 overlap in a plan view. In this embodiment, a strip-shaped insulator layer 19 is provided on the first main surface 4a of the piezoelectric layer 4I so as to cover a portion of each of the plurality of second electrode fingers 56. The bar portion 54b is provided on the insulator layer 19. This electrically insulates the second comb-shaped electrode 58 and the third electrode 59 from each other. The wider portion of each second electrode finger 56 extends beyond the insulator layer 19 toward the intersection region E.

[0137] 17 , in this embodiment, a support substrate serving as a support member 53 has a through-hole formed therein as a cavity 50a. The cavity 50a is an acoustic reflecting portion in this embodiment. The support member 53 supports the first bus bar 12 and the second bus bar 13. The support member 53 also supports the bar portion 54b of the third bus bar 54A and some of the common connecting portions 54a. Similarly, the support member 53 also supports the bar portion 54b of the third bus bar 54B shown in FIG. 16 and some of the common connecting portions 54a.

[0138] The piezoelectric layer 4I has a plurality of through holes 4c. Some of all the through holes 4c are provided in a portion of the piezoelectric layer 4I that is located between the common connection portions 54a of one third bus bar 54A and the first electrode fingers 55.

[0139] More specifically, two through holes 4c are provided in the piezoelectric layer 4I in the electrode finger extension direction in a portion between one common connection portion 54a of the third bus bar 54A and one first electrode finger 55. One of the through holes 4c is adjacent to the wide and narrow portions of the first electrode finger 55 in the direction perpendicular to the electrode fingers. The through hole 4c is adjacent to the narrow and wide portions of the common connection portion 54a in the direction perpendicular to the electrode fingers.

[0140] The other through hole 4c is adjacent to only the narrow portion of the first electrode finger 55 in the direction perpendicular to the electrode fingers, and is adjacent to only the wide portion of the common connection portion 54a in the direction perpendicular to the electrode fingers.

[0141] The other plurality of through holes 4c are provided in a portion of the piezoelectric layer 4I located between the plurality of common connection portions 54a and the plurality of second electrode fingers 56 of the other third bus bar 54B. More specifically, two through holes 4c are provided in the piezoelectric layer 4I in a portion between one common connection portion 54a of the third bus bar 54B and one second electrode finger 56, in the electrode finger extension direction. One of the through holes 4c is adjacent to the wide and narrow portions of the second electrode finger 56 in the electrode finger orthogonal direction. The through hole 4c is adjacent to the narrow and wide portions of the common connection portion 54a in the electrode finger orthogonal direction.

[0142] The other through hole 4c is adjacent in the direction perpendicular to the electrode fingers only to the narrow portion of the second electrode finger 56. The through hole 4c is adjacent in the direction perpendicular to the electrode fingers only to the wide portion of the common connection portion 54a.

[0143] In this embodiment, the through holes 4c are not provided in the portions overlapping with the third bus bars 54A and the third bus bars 54B in a plan view.

[0144] In this embodiment as well, through holes 4c are provided in portions of the piezoelectric layer 4I that are located outside the crossing region E, between electrodes that are adjacent in the orthogonal direction of the electrode fingers and connected to different potentials, thereby making it possible to suppress unwanted waves and prevent deterioration of the filter characteristics.

[0145] For an acoustic wave device having the configuration of this embodiment, the S parameters were derived by FEM simulation. The design parameters of the acoustic wave device are as follows. In the following, the distance between the tip of the electrode finger and the bus bar is referred to as the B-E gap. The width of the electrode finger is referred to as Mark.

[0146] Piezoelectric layer: Material... LiNbO ３, Cut angle...120°Y, Thickness...360 nm First to third electrode fingers: Layer structure...Ti layer / Al layer from the piezoelectric layer side, Thickness...12 nm / 360 nm from the piezoelectric layer side Center-to-center distance between the first electrode finger and the third electrode finger: 1.26 μm Center-to-center distance between the second electrode finger and the third electrode finger: 1.26 μm B-E gap: 2 μm Mark: 360 nm Insulator layer: Material...SiO ２ , thickness...0.0675 μm

[0147] FIG. 18 is a diagram showing the pass characteristic in the seventh embodiment.

[0148] 18, it can be seen that in this embodiment, ripples are suppressed within the passband. In this way, in this embodiment, it is possible to suppress unwanted waves and prevent deterioration of the filter characteristics.

[0149] FIG. 19 is a schematic plan view of an elastic wave device according to the eighth preferred embodiment of the present invention.

[0150] This embodiment differs from the second embodiment in the positional relationship between the first comb electrode 7 and the third electrode 29. This embodiment also differs from the second embodiment in the positions of the multiple insulator layers 19. This embodiment also differs from the second embodiment in the positions of the through holes 4c in the piezoelectric layer 4J. Except for the above points, the elastic wave device of this embodiment has the same configuration as the elastic wave device of the second embodiment.

[0151] In this embodiment, the configuration on the third bus bar 24 side of the intersection region E is similar to the configuration on the third bus bar 44A side of the intersection region E in the sixth embodiment shown in Fig. 14 . Specifically, as shown in Fig. 19 , the first bus bar 12 is located between the intersection region E and the third bus bar 24. The first bus bar 12 overlaps with the plurality of third electrode fingers 17 in a plan view. The first bus bar 12 and the plurality of third electrode fingers 17 are electrically insulated from each other by an insulator layer 19.

[0152] In the piezoelectric layer 4J, the plurality of through holes 4c are provided similarly to the plurality of through holes 4c on the third bus bar 44A side of the intersection region E in the sixth embodiment shown in Fig. 14. Specifically, as shown in Fig. 19, the through holes 4c are provided in a portion of the piezoelectric layer 4J that does not overlap with the plurality of third electrode fingers 17 but overlaps with the first bus bar 12 in plan view. In addition, the plurality of through holes 4c are also provided in a portion of the piezoelectric layer 4J that is located between the first bus bar 12 and the third bus bar 24 and that is located between the plurality of third electrode fingers 17.

[0153] In this embodiment, the portions of the first busbar 12 other than those overlapping with the third electrode fingers 17 in a plan view are adjacent to the third electrode fingers 17 in the direction perpendicular to the electrode fingers. Therefore, the above-mentioned portions of the first busbar 12 and the third electrode fingers 17 are located outside the intersection region E, are adjacent to each other in the direction perpendicular to the electrode fingers, and are electrodes connected to different potentials. The first busbar 12 is not provided directly on the first main surface 4 a of the piezoelectric layer 4J. This makes it possible to effectively suppress unwanted waves and effectively prevent deterioration of the filter characteristics.

[0154] 20 is a schematic plan view of an elastic wave device according to a ninth preferred embodiment of the present invention, in which the third electrode 29 is not hatched.

[0155] This embodiment differs from the second embodiment in that a portion of the third electrode 29 is provided on the second principal surface 4 b of the piezoelectric layer 4 C. The portion of the third electrode 29 that is not provided on the second principal surface 4 b is supported by the same support member 3 as in the first embodiment shown in FIG. 1 . This embodiment also differs from the second embodiment in that the insulator layer 19 is not provided. Apart from the above, the elastic wave device of this embodiment has the same configuration as the elastic wave device of the second embodiment.

[0156] In the present embodiment, the arrangement of the third electrodes 29 in a plan view is the same as that in the second embodiment. A plurality of third electrode fingers 17 are provided on the second main surface 4 b of the piezoelectric layer 4C so as to be aligned with the first electrode fingers 15 and the second electrode fingers 16 in the direction in which the first electrode fingers 15 and the second electrode fingers 16 are aligned in a plan view. The order in which the plurality of electrode fingers are aligned in a plan view is such that, starting from the first electrode finger 15, one period includes the first electrode finger 15, the third electrode finger 17, the second electrode finger 16, and the third electrode finger 17. In a plan view, the third bus bar 24 is provided between the intersection region E and the first bus bar 12.

[0157] The arrangement of the plurality of through holes 4c in the piezoelectric layer 4C is the same as in the second embodiment. Therefore, the plurality of through holes 4c are provided in portions of the piezoelectric layer 4C that do not overlap with the plurality of first electrode fingers 15 and the plurality of third electrode fingers 17 in a plan view, but overlap with the third bus bar 24. In addition, the plurality of through holes 4c are also provided in portions of the piezoelectric layer 4C that are located between the third bus bar 24 and the first bus bar 12, and between the plurality of first electrode fingers 15.

[0158] The third bus bar 24 and the plurality of first electrode fingers 15 face each other with the piezoelectric layer 4C in between, so that the first comb electrode 7 and the third electrode 29 are electrically insulated from each other.

[0159] In this embodiment as well, through holes 4c are provided in portions of the piezoelectric layer 4C that are located outside the crossing region E, between electrodes that are adjacent in the orthogonal direction of the electrode fingers and connected to different potentials, thereby making it possible to effectively suppress unwanted waves and effectively prevent deterioration of the filter characteristics.

[0160] The configuration in the ninth embodiment in which a portion of the third electrode is provided on the second main surface of the piezoelectric layer can also be applied to other configurations of the present invention other than the ninth embodiment. For example, a portion of the third electrode in the first embodiment, the third to eighth embodiments, and each of the modified examples may be provided on the second main surface. In this case, it is sufficient that a through hole is provided in at least a portion of a portion of the piezoelectric layer that is located outside the crossing region and that is located between the first comb electrode or the second comb electrode and the third electrode in the direction perpendicular to the electrode fingers.

[0161] In the first to ninth embodiments, the through-holes of the piezoelectric layer are hollow. However, a dielectric layer or a resin layer may be provided in the through-holes. This example is shown in the tenth embodiment.

[0162] Fig. 21 is a schematic plan view of an elastic wave device according to a tenth preferred embodiment of the present invention. Fig. 22 is a schematic cross-sectional view taken along line IV-IV in Fig. 21. In Fig. 21, dielectric layers, which will be described later, are indicated by hatching.

[0163] 21 , this embodiment differs from the first embodiment in the position of the through hole 4 c in the piezoelectric layer 4 K and in that a dielectric layer 62 is provided in the through hole 4 c. Except for the above differences, the elastic wave device of this embodiment has the same configuration as the elastic wave device 10 of the first embodiment.

[0164] One through hole 4c is provided in the piezoelectric layer 4K so as to overlap with the third bus bar 14 in a plan view. More specifically, in a plan view, the edge of the through hole 4c on the crossing region E side includes an imaginary line connecting the edges of the multiple common connection portions 14a on the crossing region E side. The edge of the through hole 4c on the first bus bar 12 side includes the edge of the first bus bar 12 on the crossing region E side. A dielectric layer 62 is filled inside this through hole 4c.

[0165] As shown in FIG. 22 , in this embodiment, some of the first electrode fingers 15 , the third bus bar 14 , and a plurality of insulator layers 19 are provided on a dielectric layer 62 .

[0166] In this embodiment, the portions of the third busbar 14 other than those overlapping with the first electrode fingers 15 in a planar view are adjacent to the first electrode fingers 15 in the direction perpendicular to the electrode fingers. Therefore, the above-mentioned portions of the third busbar 14 and the first electrode fingers 15 are located outside the intersection region E, adjacent to each other in the direction perpendicular to the electrode fingers, and connected to different potentials. In this embodiment, none of the portions of these electrodes that are adjacent to each other in the direction perpendicular to the electrode fingers are provided directly on the first main surface 4 a of the piezoelectric layer 4K. This makes it possible to effectively suppress unwanted waves and effectively prevent deterioration of the filter characteristics.

[0167] The configuration in this embodiment in which the dielectric layer 62 is provided inside the through hole 4c can also be used in configurations of the present invention other than this embodiment. Note that a resin layer may be provided instead of the dielectric layer 62.

[0168] In the first to tenth embodiments, the third bus bar and the third electrode fingers are provided on the same main surface of the piezoelectric layer. However, the third bus bar and the third electrode fingers do not necessarily have to be provided on the same main surface. An example in which the third bus bar and the third electrode fingers are provided on different main surfaces is shown in the eleventh embodiment.

[0169] Fig. 23 is a schematic plan view of an elastic wave device according to an eleventh preferred embodiment of the present invention. Fig. 24 is a schematic cross-sectional view taken along line II in Fig. 23. Fig. 25 is a schematic cross-sectional view taken along line VV in Fig. 23.

[0170] 23 , this embodiment differs from the second embodiment in the configuration of the third electrode 79. As shown in FIG. 24 , this embodiment also differs from the second embodiment in the configuration of the insulating layer 75. Except for the above points, the elastic wave device of this embodiment has the same configuration as the elastic wave device of the second embodiment.

[0171] 25 , the third electrode 79 includes a third bus bar 24, a plurality of third electrode fingers 17, and a plurality of connection electrodes 78. As in the second embodiment, the plurality of third electrode fingers 17 are provided on the first main surface 4 a of the piezoelectric layer 4L. Specifically, the plurality of third electrode fingers 17 are provided directly on the first main surface 4 a.

[0172] On the other hand, the third bus bar 24 is provided on the second main surface 4b of the piezoelectric layer 4L. Specifically, the third bus bar 24 is provided directly on the second main surface 4b. The third bus bar 24 extends in a direction perpendicular to the electrode fingers. The third bus bar 24 is provided so as to face the plurality of third electrode fingers 17 across the piezoelectric layer 4L. However, the direction in which the third bus bar 24 extends is not limited to the above.

[0173] The plurality of connection electrodes 78 penetrate the piezoelectric layer 4L. Each connection electrode 78 connects one third electrode finger 17 to the third bus bar 24. That is, the plurality of third electrode fingers 17 are electrically connected to the third bus bar 24 via the plurality of connection electrodes 78.

[0174] As shown in Fig. 24 , a hollow portion is provided in the insulating layer 75. That is, the hollow portion is configured as a cavity 70a in the insulating layer 75. In this embodiment, the insulating layer 75 covers the second main surface 4b of the piezoelectric layer 4L. As shown in Fig. 25 , the insulating layer 75 covers the third bus bar 24 of the third electrode 79. However, the insulating layer 75 does not have to cover the second main surface 4b or the third bus bar 24. For example, the insulating layer 75 may be provided in the same manner as the insulating layer 5 shown in Fig. 1 .

[0175] The third electrode 79 of this embodiment differs from the second embodiment in that it includes a plurality of connection electrodes 78. However, the arrangement of the third electrode 79 in a plan view shown in FIG. 23 is the same as that of the second embodiment. Therefore, in a plan view, a plurality of third electrode fingers 17 are provided on the first main surface 4 a of the piezoelectric layer 4L so as to be aligned with the first electrode fingers 15 and the second electrode fingers 16 in the direction in which the first electrode fingers 15 and the second electrode fingers 16 are aligned. In a plan view, the order in which the plurality of electrode fingers are aligned is such that, starting from the first electrode finger 15, one period includes the first electrode finger 15, the third electrode finger 17, the second electrode finger 16, and the third electrode finger 17.

[0176] In plan view, the third bus bar 24 is provided between the intersection region E and the first bus bar 12. The third bus bar 24 overlaps with the plurality of first electrode fingers 15 in plan view.

[0177] The plurality of through holes 4c in the piezoelectric layer 4L are provided in a portion of the piezoelectric layer 4L that overlaps with the third bus bar 24 in a plan view and is located between the plurality of first electrode fingers 15 and the plurality of third electrode fingers 17. In addition, the plurality of first electrode fingers 15 and the third bus bar 24 are provided on different main surfaces of the piezoelectric layer 4L. This makes it possible to effectively suppress unwanted waves and effectively prevent deterioration of the filter characteristics.

[0178] The arrangement of the through holes 4c is not limited to the above. For example, in a first modification of the eleventh embodiment shown in Fig. 26, the through holes 4c are provided in portions of the piezoelectric layer 4M that overlap with the third bus bar 24 and the first electrode fingers 15 in a plan view. The first electrode fingers 15 are supported by portions of the piezoelectric layer 4M other than the portions where the through holes 4c are provided. In this case, as in the eleventh embodiment, unwanted waves can be suppressed, and degradation of the filter characteristics can be suppressed.

[0179] 27 , a plurality of through holes 4c are provided in the piezoelectric layer 4N in a portion overlapping with the third bus bar 24 in a plan view and between the plurality of third electrode fingers 17. Therefore, the plurality of through holes 4c are also located in a portion overlapping with the first electrode fingers 15 in a plan view. In this modification, a dielectric layer 62 is provided in the plurality of through holes 4c. Part of the first electrode fingers 15 is provided on the dielectric layer 62. Note that a resin layer may be provided instead of the dielectric layer 62.

[0180] In this modification, as in the eleventh embodiment and the tenth embodiment, it is possible to suppress unwanted waves and to prevent deterioration of the filter characteristics.

[0181] In the first to eleventh embodiments, the third bus bar is provided on the first or second main surface of the piezoelectric layer. However, in the present invention, the third bus bar may be provided on a surface other than the first or second main surface of the piezoelectric layer. This example is shown in the twelfth and thirteenth embodiments.

[0182] Fig. 28 is a schematic front cross-sectional view of an elastic wave device according to a twelfth preferred embodiment of the present invention. In Fig. 28, the portions where the comb-shaped electrodes and the third electrode fingers are provided are shown as a simplified rectangle with two diagonal lines added. This is also true for the other schematic front cross-sectional views. Note that Fig. 28 shows a cross section of a portion of the third electrode where the third bus bar and the connection electrode are not provided.

[0183] An elastic wave device 80 of this preferred embodiment has a wafer level package (WLP) structure. Specifically, a first support 82, which serves as a support according to the present invention, is provided on a piezoelectric substrate 2L. More specifically, the first support 82 is provided on a first main surface 4a of a piezoelectric layer 4L. The first support 82 has a frame-like shape. Therefore, the first support 82 has an opening 82a.

[0184] The first main surface 4a of the piezoelectric layer 4L is provided with a first comb electrode, a second comb electrode, and a plurality of third electrode fingers of the functional electrode 81. When the portion of the piezoelectric layer 4L where the comb electrodes and the plurality of third electrode fingers are provided is defined as an element electrode forming portion F, the element electrode forming portion F is located within the opening 82a.

[0185] A plurality of second supports 83 are provided on the first main surface 4a of the piezoelectric layer 4L. The second supports 83 have a columnar shape. The plurality of second supports 83 are located within the openings 82a of the first support 82. In this embodiment, the first support 82 and the second support 83 are each a laminate of a plurality of metal layers. Note that the second supports 83 do not necessarily have to be provided.

[0186] A lid member 84 is provided on the first support 82 and the plurality of second supports 83 so as to cover the opening 82a. This forms a hollow space surrounded by the piezoelectric substrate 2L, the first support 82, and the lid member 84. An element electrode formation portion F of the piezoelectric layer 4L is located within this hollow space.

[0187] The lid member 84 has a lid member main body 84A and an inorganic oxide layer 84B. The lid member main body 84A has a pair of main surfaces that face each other. One of the main surfaces of the lid member main body 84A faces the piezoelectric substrate 2L. The inorganic oxide layer 84B is provided on both main surfaces of the lid member main body 84A.

[0188] More specifically, the lid member 84 has a third principal surface 84a and a fourth principal surface 84b. The third principal surface 84a and the fourth principal surface 84b face each other. Of the third principal surface 84a and the fourth principal surface 84b, the third principal surface 84a is the principal surface facing the piezoelectric substrate 2L. The principal surface of the lid member 84 is the surface of the inorganic oxide layer 84B. More specifically, the principal surface of the lid member 84 is the surface of the inorganic oxide layer 84B in the portion that is provided on the principal surface of the lid member main body 84A. However, the inorganic oxide layer 84B does not necessarily have to be provided. In this case, the third principal surface 84a and the fourth principal surface 84b of the lid member 84 are the principal surfaces of the lid member main body 84A.

[0189] In this embodiment, the lid member main body 84A is a silicon substrate. The support substrate 6 of the piezoelectric substrate 2L is also a silicon substrate. However, the materials of the support substrate 6 and the lid member main body 84A are not limited to those mentioned above.

[0190] A through electrode 85 is provided in the lid member 84. More specifically, a through hole is provided in the lid member 84. The through hole is provided so as to reach the second support 83. The through electrode 85 is provided in the through hole. One end of the through electrode 85 is connected to the second support 83. An external terminal 86 is provided so as to be connected to the other end of the through electrode 85. The external terminal 86 is configured as an electrode pad. In this embodiment, the through electrode 85 and the external terminal 86 are provided as a single unit. However, the through electrode 85 and the external terminal 86 may also be provided separately.

[0191] The inorganic oxide layer 84B of the lid member 84 is provided not only on the main surface of the lid member main body 84A but also inside the through-hole. More specifically, inside the through-hole, the inorganic oxide layer 84B is located between the through-electrode 85 and the lid member main body 84A. The inorganic oxide layer 84B is provided so as to cover the vicinity of the outer periphery of the external terminal 86. The inorganic oxide layer 84B extends between the external terminal 86 and the lid member main body 84A. The inorganic oxide layer 84B is, for example, a silicon oxide layer. However, the material of the inorganic oxide layer 84B is not limited to the above.

[0192] The inorganic oxide layer 84B does not have to be provided inside the through-holes of the lid member main body 84A. The inorganic oxide layer 84B does not have to be provided on the external terminals 86 or between the external terminals 86 and the lid member main body 84A.

[0193] Bumps 87 are provided as conductive bonding members on portions of the multiple external terminals 86 that are not covered with the inorganic oxide layer 84B. The bumps 87 may be, for example, solder bumps or Au bumps. The conductive bonding members may be, for example, a conductive adhesive. The conductive bonding members are electrically connected to an external reference potential or signal potential.

[0194] FIG. 29 is a schematic enlarged front cross-sectional view illustrating a portion of an elastic wave device according to a twelfth preferred embodiment of the present invention.

[0195] The third bus bar 24 of the third electrode 89 is provided on the third main surface 84 a of the cover member 84. The third bus bar 24 faces some of the plurality of third electrode fingers 17.

[0196] The plurality of connection electrodes 88 of the third electrode 89 are provided between the first main surface 4a of the piezoelectric layer 4L and the lid member 84. The connection electrodes 88 are columnar electrodes. More specifically, each connection electrode 88 is provided over one third electrode finger 17 and the piezoelectric layer 4L. Each connection electrode 88 is connected to the third bus bar 24. That is, the plurality of connection electrodes 88 connect the third bus bar 24 and the plurality of third electrode fingers 17.

[0197] However, it is sufficient that each connection electrode 88 is provided on at least the third electrode finger 17. At least one connection electrode 88 may be provided only on the third electrode finger 17. In this case, the connection electrode 88 is not provided directly on the piezoelectric layer 4L.

[0198] Fig. 30 is a schematic plan view showing an electrode configuration on a first main surface of a piezoelectric layer in the twelfth embodiment. Note that Fig. 29 above is a schematic cross-sectional view showing a portion along line VV in Fig. 30.

[0199] 30 , the third bus bar 24 is provided in a portion of the intersection region E that overlaps with an outer region in the electrode finger extension direction in a plan view. Specifically, the third bus bar 24 is provided between the intersection region E and the first bus bar 12 in a plan view. The third bus bar 24 overlaps with the first electrode fingers 15 in a plan view. The third bus bar 24 is electrically connected to a reference potential via other wiring and the through electrodes 85 and bumps 87 shown in FIG.

[0200] 29 , in this embodiment, a plurality of through holes 4c are provided in the piezoelectric layer 4L, similar to the eleventh embodiment. Specifically, the plurality of through holes 4c are provided in the piezoelectric layer 4L in a portion that overlaps with the third bus bar 24 in a plan view and is located between the plurality of first electrode fingers 15 and the plurality of third electrode fingers 17. In addition, the third bus bar 24 is provided on a cover member 84. This makes it possible to effectively suppress unwanted waves and effectively prevent deterioration of the filter characteristics.

[0201] The arrangement of the through holes 4c is not limited to the above. For example, in a first modification of the twelfth embodiment shown in Fig. 31 , the through holes 4c are provided in portions of the piezoelectric layer 4M that overlap with the third bus bar 24 and the first electrode fingers 15 in a plan view. The first electrode fingers 15 are supported by portions of the piezoelectric layer 4M other than the portions where the through holes 4c are provided. In this modification, as in the twelfth embodiment, unwanted waves can be suppressed and degradation of the filter characteristics can be suppressed.

[0202] 32 , in a second modification of the twelfth embodiment, a plurality of through holes 4c are provided in portions of the piezoelectric layer 4O that overlap with the third bus bar 24 and the plurality of third electrode fingers 17 in a plan view. The through holes 4c also overlap with the connection electrode 88 in a plan view. However, the third electrode fingers 17 and the connection electrode 88 are supported by portions of the piezoelectric layer 4O other than the portions where the through holes 4c are provided. In this modification, as in the twelfth embodiment, unwanted waves can be suppressed, and degradation of the filter characteristics can be suppressed.

[0203] 28 , in the twelfth preferred embodiment, there is a high degree of freedom in the layout of the third principal surface 84 a of the lid member 84. Therefore, wiring for connecting the third electrode 89 shown in FIG. 29 to a reference potential can be easily provided on the third principal surface 84 a without increasing the size of the elastic wave device 80. In addition, the width of the third bus bar 24 can be easily increased. This allows the electrical resistance of the third electrode 89 to be easily and effectively reduced.

[0204] 28 may be provided on a layer of the piezoelectric substrate 2L other than the piezoelectric layer 4L. More specifically, the support member 3 is a laminate of a support substrate 6 and an insulating layer 5, as in the first embodiment. For example, in a plan view, the outer periphery of the piezoelectric layer 4L may be located inside the outer periphery of the insulating layer 5 or the support substrate 6. In this case, the first support 82 may be provided on the insulating layer 5 or the support substrate 6.

[0205] 30 is connected to an input potential. The second comb electrode 8 is connected to an output potential. Alternatively, the second comb electrode 8 may be connected to the input potential and the first comb electrode 7 may be connected to the output potential.

[0206] FIG. 33 is a schematic front cross-sectional view of an elastic wave device according to a thirteenth preferred embodiment of the present invention.

[0207] The acoustic wave device 90 has a configuration in which an acoustic wave resonator is mounted on a mounting substrate 95. Specifically, the acoustic wave device 90 has a CSP (chip size package) structure. The mounting substrate 95 is a printed circuit board (PCB). In this embodiment, the material of the mounting substrate 95 is high-temperature co-fired ceramic (HTCC). However, the material of the mounting substrate 95 is not limited to the above.

[0208] On the other hand, the support substrate 6 of the piezoelectric substrate 2L is a silicon substrate, although the material of the support substrate 6 is not limited to the above.

[0209] A plurality of conductive bonding members are provided on the piezoelectric substrate 2L. More specifically, a plurality of electrode pads 98 are provided on the piezoelectric substrate 2L. A conductive bonding member is provided on each of the plurality of electrode pads 98. In this embodiment, the conductive bonding members are bumps 97. The bumps 97 may be, for example, solder bumps or Au bumps.

[0210] The piezoelectric substrate 2L is bonded to a mounting substrate 95 by a plurality of conductive bonding members. The mounting substrate 95 has a fifth main surface 95a and a sixth main surface 95b. The fifth main surface 95a and the sixth main surface 95b face each other. Of the fifth main surface 95a and the sixth main surface 95b, the fifth main surface 95a is the main surface on the piezoelectric substrate 2L side. A sealing resin 94 is provided on the fifth main surface 95a so as to cover the support substrate 6 of the piezoelectric substrate 2L. A hollow portion is formed by the piezoelectric substrate 2L, the sealing resin 94, and the mounting substrate 95. An element electrode formation portion F of the piezoelectric layer 4L is located within this hollow portion.

[0211] A plurality of external terminals 96 are provided on a sixth main surface 95b of the mounting substrate 95. A plurality of via electrodes and a plurality of wirings are provided within the mounting substrate 95. Each external terminal 96 is electrically connected to the via electrodes and wirings within the mounting substrate 95. Each of the plurality of external terminals 96 is electrically connected to an external reference potential or signal potential via a bump, a conductive adhesive, or the like.

[0212] FIG. 34 is a schematic enlarged front cross-sectional view illustrating a portion of the elastic wave device according to the thirteenth preferred embodiment.

[0213] In this embodiment, the third bus bar 24 of the third electrode 89 is provided on the fifth main surface 95 a of the mounting substrate 95. The third bus bar 24 faces some of the plurality of third electrode fingers 17.

[0214] The multiple connection electrodes 88 of the third electrode 89 are provided between the first main surface 4a of the piezoelectric layer 4L and the fifth main surface 95a of the mounting substrate 95. The connection electrodes 88 are columnar electrodes. More specifically, each connection electrode 88 is provided on only one third electrode finger 17. Each connection electrode 88 is connected to the third bus bar 24. That is, the multiple connection electrodes 88 connect the third bus bar 24 and the multiple third electrode fingers 17. It is sufficient that each connection electrode 88 is provided on at least the third electrode finger 17. At least one connection electrode 88 may be provided across the third electrode finger 17 and the piezoelectric layer 4L.

[0215] Fig. 35 is a schematic plan view showing an electrode configuration on a first main surface of a piezoelectric layer in the thirteenth embodiment. Note that Fig. 34 above is a schematic cross-sectional view showing a portion along line VV in Fig. 35.

[0216] 35 , the third bus bar 24 is located in a portion of the intersection region E that overlaps with an outer region in the electrode finger extension direction in a plan view. Specifically, the third bus bar 24 is provided between the intersection region E and the first bus bar 12 in a plan view. The third bus bar 24 overlaps with the first electrode fingers 15 in a plan view. The third bus bar 24 is electrically connected to a reference potential via wiring on a fifth main surface 95 a of the mounting substrate 95 shown in FIG. 33 , wiring and via electrodes within the mounting substrate 95, and external terminals 96.

[0217] 34 , in this embodiment, a plurality of through holes 4c are provided in the piezoelectric layer 4L, similar to the eleventh embodiment. Specifically, the plurality of through holes 4c are provided in a portion of the piezoelectric layer 4L that overlaps with the third bus bar 24 in a plan view and is located between the plurality of first electrode fingers 15 and the plurality of third electrode fingers 17. In addition, the third bus bar 24 is provided on a mounting substrate 95. This makes it possible to effectively suppress unwanted waves and effectively prevent deterioration of the filter characteristics.

[0218] The arrangement of the through holes 4c is not limited to the above. For example, in a first modification of the thirteenth embodiment shown in Fig. 36, the through holes 4c are provided in portions of the piezoelectric layer 4M that overlap with the third bus bar 24 and the first electrode fingers 15 in a plan view. The first electrode fingers 15 are supported by portions of the piezoelectric layer 4M other than the portions where the through holes 4c are provided. In this modification, as in the thirteenth embodiment, unwanted waves can be suppressed and degradation of the filter characteristics can be suppressed.

[0219] 37 , in a second modification of the thirteenth embodiment, a plurality of through holes 4c are provided in portions of the piezoelectric layer 4O that overlap with the third bus bar 24 and the plurality of third electrode fingers 17 in a plan view. The through holes 4c also overlap with the connection electrode 88 in a plan view. However, the third electrode fingers 17 and the connection electrode 88 are supported by portions of the piezoelectric layer 4O other than the portions where the through holes 4c are provided. In this modification, as in the thirteenth embodiment, unwanted waves can be suppressed, and degradation of the filter characteristics can be suppressed.

[0220] 33 , in this embodiment, there is a high degree of freedom in the layout of the fifth main surface 95 a of the mounting substrate 95. Therefore, wiring for connecting the third electrode 89 shown in FIG. 34 to a reference potential can be easily provided on the fifth main surface 95 a without increasing the size of the acoustic wave device 90. In addition, the width of the third bus bar 24 can be easily increased. This allows the electrical resistance of the third electrode 89 to be easily and effectively reduced.

[0221] 35 is connected to an input potential. The second comb electrode 8 is connected to an output potential. Alternatively, the second comb electrode 8 may be connected to the input potential and the first comb electrode 7 may be connected to the output potential.

[0222] In the twelfth and thirteenth embodiments, the arrangement of the third bus bars 24 in plan view and the arrangement of the through holes in the piezoelectric layer 4L are the same as those in the eleventh embodiment. However, it is sufficient that the through holes 4c are provided in at least a part of the part of the piezoelectric layer 4L that is located outside the crossing region E and that is located between the first comb electrode 7 or the second comb electrode 8 and the third electrode 89 in the electrode finger orthogonal direction.

[0223] In the first to thirteenth embodiments, the acoustic reflector is a cavity in the piezoelectric substrate. However, the acoustic reflector may be an acoustic reflecting film. This example is shown in the fourteenth embodiment.

[0224] FIG. 38 is a schematic front cross-sectional view of an elastic wave device according to a fourteenth preferred embodiment of the present invention.

[0225] This embodiment differs from the first embodiment in that the acoustic reflection portion is an acoustic reflection film 118. This embodiment also differs from the first embodiment in that the support member 113 is formed only from a support substrate. Except for the above points, the elastic wave device of this embodiment has the same configuration as elastic wave device 10 of the first embodiment.

[0226] An acoustic reflection film 118 is provided on the surface of the support member 113. A piezoelectric layer 4 is provided on the acoustic reflection film 118. The support member 113 and the piezoelectric layer 4 may be arranged such that at least a portion of the support member 113 and at least a portion of the piezoelectric layer 4 face each other with the acoustic reflection film 118 sandwiched between them.

[0227] The acoustic reflecting film 118 is a laminate of multiple acoustic impedance layers. Specifically, the acoustic reflecting film 118 has multiple low acoustic impedance layers and multiple high acoustic impedance layers. The low acoustic impedance layers are layers with relatively low acoustic impedance. More specifically, the multiple low acoustic impedance layers in the acoustic reflecting film 118 are low acoustic impedance layer 115a, low acoustic impedance layer 115b, and low acoustic impedance layer 115c.

[0228] On the other hand, the high acoustic impedance layer is a layer with a relatively high acoustic impedance. More specifically, the multiple high acoustic impedance layers in the acoustic reflecting film 118 are the high acoustic impedance layer 116a and the high acoustic impedance layer 116b. The low acoustic impedance layers and the high acoustic impedance layers are alternately stacked. The low acoustic impedance layer 115a is the layer in the acoustic reflecting film 118 that is located closest to the piezoelectric layer 4.

[0229] The acoustic reflection film 118 has three low acoustic impedance layers and two high acoustic impedance layers, although it is sufficient that the acoustic reflection film 118 has at least one low acoustic impedance layer and one high acoustic impedance layer.

[0230] The low acoustic impedance layer may be made of, for example, silicon oxide or aluminum, while the high acoustic impedance layer may be made of, for example, a metal such as platinum or tungsten, or a dielectric such as aluminum nitride, silicon nitride or hafnium oxide.

[0231] In this embodiment, as in the first embodiment, unwanted waves can be effectively suppressed and deterioration of the filter characteristics can be effectively suppressed. In addition, by providing the acoustic reflection film 118, the energy of the elastic waves can be effectively confined on the piezoelectric layer 4 side.

[0232] The configuration in this embodiment in which the acoustic reflecting portion is the acoustic reflecting film 118 can be applied to configurations of the present invention other than this embodiment.

[0233] A preferred configuration of the present invention will be described below using a reference example shown in Fig. 39. The reference example differs from the first embodiment in that an IDT electrode 201 is provided instead of the functional electrode 1 shown in Fig. 2. The reference example also differs from the first embodiment in that the piezoelectric layer 204 does not have a through-hole. Apart from the above, the elastic wave device of the reference example has the same configuration as the first embodiment.

[0234] The IDT electrode 201 differs from the functional electrode in that it does not have a third electrode. Therefore, the IDT electrode 201 has a first comb-shaped electrode 7 and a second comb-shaped electrode 8. The intersection region E in the reference example is a region where adjacent first electrode fingers 15 and second electrode fingers 16 overlap when viewed from the direction perpendicular to the electrode fingers.

[0235] The elastic wave device of the reference example also utilizes thickness-shear mode bulk waves, as in the first to fourteenth embodiments. In this case, a portion where a pair of adjacent electrode fingers are connected to different potentials functions as a single resonator. Therefore, the configuration of an elastic wave device utilizing thickness-shear mode bulk waves is equivalent to a configuration in which multiple resonators are connected in parallel. In this respect, this is true for both elastic wave devices having IDT electrodes and acoustically coupled filters such as those of the first to fourteenth embodiments. Therefore, the following configuration shown in the reference example can be said to be a preferred configuration for the first to fourteenth embodiments as well.

[0236] In the present invention, where d is the thickness of the piezoelectric layer and p is the center-to-center distance between adjacent electrode fingers, d / p is preferably 0.5 or less, and more preferably 0.24 or less. This allows thickness-shear mode bulk waves to be suitably excited and enables the elastic wave device to have a sufficiently large fractional bandwidth. The fractional bandwidth is expressed as (|fa-fr| / fr) x 100 [%], where fr is the resonant frequency and fa is the antiresonant frequency.

[0237] FIG. 40 is a graph showing the relationship between d / p and the fractional bandwidth of an elastic wave device according to a reference example.

[0238] As is clear from Figure 40, when d / p > 0.5, the fractional bandwidth is less than 5%. In contrast, when d / p ≤ 0.5, the fractional bandwidth can be increased to 5% or more. This increases the electromechanical coupling coefficient of the thickness-shear mode bulk wave. When d / p ≤ 0.24, the fractional bandwidth can be increased to 7% or more. This effectively increases the electromechanical coupling coefficient of the thickness-shear mode bulk wave.

[0239] When the metallization ratio of the electrode fingers to the excitation region C is MR, it is preferable to satisfy MR≦1.75(d / p)+0.075. In this case, the value of the fractional bandwidth of the acoustic wave device does not become too large, and spurious emissions between the resonant frequency and the antiresonant frequency can be suppressed. Details of this are described below.

[0240] In this specification, the metallization ratio MR of the electrode fingers to the excitation region C is the ratio of the portion of the piezoelectric layer covered with the metal constituting the electrode fingers to the excitation region C in a plan view. In the reference example shown in Fig. 39 , the metallization ratio MR is the ratio of the area of ​​the first electrode fingers 15 and the second electrode fingers 16 in the excitation region C to the area of ​​the excitation region C in a plan view. On the other hand, in the first embodiment of the present invention shown in Fig. 2 and the like, the metallization ratio MR is the ratio of the area of ​​the first electrode fingers 15 and the third electrode fingers 17 and the ratio of the area of ​​the second electrode fingers 16 and the third electrode fingers 17 to the excitation region C.

[0241] In addition, when the width of the electrode fingers located within the excitation region C is constant, the metallization ratio MR can also be calculated by dividing the sum of the widths of the electrode fingers located within the excitation region C by the dimension of the excitation region C along the direction perpendicular to the electrode fingers.

[0242] Fig. 41 is a diagram showing the relationship between the relative bandwidth and the normalized magnitude of spurious signals in the elastic wave device of the reference example. Fig. 41 shows the results of measuring the amount of phase rotation of spurious signals each time the relative bandwidth is changed by changing the thickness of the piezoelectric layer and the dimensions of the electrode fingers. Note that the normalized magnitude of spurious signals in Fig. 41 is specifically the value obtained by normalizing the amount of phase rotation of the spurious impedance by 180°. The results shown in Fig. 41 are for a Z-cut LiNbO ３ Although this is the result when a piezoelectric layer made of this material was used, the same tendency is observed when a piezoelectric layer having another cut angle is used.

[0243] In the region surrounded by ellipse B in Figure 41, the normalized magnitude of the spurious response between the resonant frequency and the anti-resonant frequency is 1.0. If the bandwidth fraction of the elastic wave resonator exceeds 17%, the normalized magnitude of the spurious response may be 1.0 or more. For this reason, it is preferable that the bandwidth fraction be 17% or less. This makes it possible to suppress the spurious response between the resonant frequency and the anti-resonant frequency.

[0244] 42 is a diagram showing the relationship between d / p, metallization ratio MR, and bandwidth fraction, in which the bandwidth fraction is calculated for each of different d / p and metallization ratio MR.

[0245] In FIG. 42 , the hatched portion is the region where the fractional bandwidth is 17% or less. The boundary between this hatched region and the non-hatched region is roughly represented by dashed line G. Dashed line G is represented by MR = 1.75(d / p) + 0.075. When MR≦1.75(d / p) + 0.075, it is easy to keep the fractional bandwidth at 17% or less in the reference example, and it is easy to suppress spurious signals. For this reason, in the present invention, it is preferable that MR≦1.75(d / p) + 0.075. This makes it easy to suppress spurious signals.

[0246] On the other hand, the dashed-dotted line G1 in Figure 42 indicates the boundary where the slope of the change in metallization ratio MR with respect to the change in d / p is the same as that of the dashed line G, and where the fractional bandwidth is 17% or less over the entire range. The dashed-dotted line G1 is represented by MR = 1.75(d / p) + 0.05. When MR ≤ 1.75(d / p) + 0.05, the fractional bandwidth can be more reliably kept to 17% or less, and spurious emissions can be more reliably suppressed. For this reason, in the present invention, it is more preferable that MR ≤ 1.75(d / p) + 0.05. This more reliably suppresses spurious emissions.

[0247] Here, the relationship between the bandwidth fraction of elastic wave device 10 and the Euler angles (φ, θ, ψ) of the piezoelectric portion of piezoelectric layer 4 when d / p is as close to 0 as possible in the configuration of the first preferred embodiment was derived. Note that φ in the Euler angles was set to 0°.

[0248] FIG. 43 shows the LiNbO ３ 43 is a diagram showing a map of fractional bandwidths with respect to Euler angles (0°, θ, ψ) of the frequency band of the optical fiber 100. The hatched area in FIG. 43 is a region where a fractional bandwidth of at least 5% or more can be obtained, and the range of this region can be approximated to the ranges expressed by the following formulas (1), (2), and (3).

[0249] (within the range of 0°±10°, 0° to 25°, any ψ) ... Equation (1) (within the range of 0°±10°, 25° to 100°, 0° to 75° [(1-(θ-50) ２ / 2500) １／２ or 180°-75°[(1-(θ-50) ２ / 2500) １／２ ~180°) ...Equation (2) (within the range of 0°±10°, 180°-40°[(1-(ψ-90) ２ / 8100)] １／２ ~180°, any ψ) ...Equation (3)

[0250] In the present invention, it is preferable that the Euler angles (φ, θ, ψ) of the lithium niobate constituting the piezoelectric layer are within the range of the above formula (1), formula (2), or formula (3). This allows the relative bandwidth of the elastic wave resonator to be sufficiently wide. The same applies when the piezoelectric layer is made of lithium tantalate.

[0251] Examples of embodiments of the acoustic wave device according to the present invention will be described below.

[0252] <1> A piezoelectric layer having a first main surface and a second main surface opposing each other; a first comb electrode provided on the first main surface of the piezoelectric layer, the first comb electrode having a first bus bar and a plurality of first electrode fingers, one end of each of which is connected to the first bus bar; a second comb electrode provided on the first main surface of the piezoelectric layer, the second comb electrode having a second bus bar and a plurality of second electrode fingers, one end of each of which is connected to the second bus bar and interdigitated with the plurality of first electrode fingers; a third electrode having a plurality of third electrode fingers provided on one of the first principal surface and the second principal surface of the piezoelectric layer so as to be aligned with the first electrode fingers and the second electrode fingers in a direction in which the second electrode fingers are aligned, and at least one third bus bar connecting the plurality of third electrode fingers to each other, and connected to a potential different from that of the first comb electrode and the second comb electrode, wherein one of the first comb electrode and the second comb electrode is connected to an input potential, and the other of the two electrodes is connected to an output potential, and the order in which the first electrode finger, the second electrode finger, and the third electrode finger are arranged is an order in which, starting from the first electrode finger, the first electrode finger, the third electrode finger, the second electrode finger, and the third electrode finger form one period, and when a direction orthogonal to a direction in which the first electrode finger, the second electrode finger, and the third electrode finger extend is defined as an electrode finger orthogonal direction, a region in which the first electrode finger and the second electrode finger overlap in the electrode finger orthogonal direction is an intersection region, and the third bus bar is located between the intersection region and the first bus bar in a plan view, the third bus bar overlaps with the first electrode fingers in a plan view, the third bus bar and the first electrode fingers are electrically insulated from each other, and a through hole is provided in at least a part of a portion of the piezoelectric layer that is located between the intersection region and the first bus bar and that is located between the first comb electrode and the third electrode in a direction perpendicular to the electrode fingers.

[0253] <2> An elastic wave device as described in <1>, wherein the through hole is provided in a portion of the piezoelectric layer located between the intersection region and the first bus bar, and located between the first electrode finger and the third electrode finger in the direction perpendicular to the electrode fingers.

[0254] <3> The elastic wave device described in <1> or <2>, wherein the third bus bar includes a common connection portion connecting adjacent pairs of the third electrode fingers, the common connection portion has a portion adjacent to the first electrode finger in a direction perpendicular to the electrode fingers, and the through hole is provided in a portion of the piezoelectric layer located between the intersection region and the first bus bar, and located between the first electrode finger and the common connection portion in the direction perpendicular to the electrode fingers.

[0255] <4> The elastic wave device according to any one of <1> to <3>, further comprising: two third bus bars; one of the third bus bars is located between the intersection region and the first bus bar in a planar view, the third bus bar overlaps with the first electrode fingers in a planar view, and the third bus bar is electrically insulated from the first electrode fingers; the other of the third bus bars is located between the intersection region and the second bus bar, the third bus bar overlaps with the second electrode fingers in a planar view, and the third bus bar is electrically insulated from the second electrode fingers; and a through hole is provided in at least a part of a portion of the piezoelectric layer that is located between the intersection region and the second bus bar and that is located between the second interdigital electrode and the third electrode in a direction perpendicular to the electrode fingers.

[0256] <5> The elastic wave device according to any one of <1> to <3>, further comprising: two third bus bars, one of which is located between the intersection region and the first bus bar in a planar view, the third bus bar overlapping the plurality of first electrode fingers in a planar view, and the third bus bar being electrically insulated from the plurality of first electrode fingers; the second bus bar being located between the intersection region and the other of the third bus bars, the second bus bar overlapping the plurality of third electrode fingers in a planar view, and the second bus bar being electrically insulated from the plurality of third electrode fingers; and a through hole being provided in at least a part of a portion of the piezoelectric layer that is located between the intersection region and the third bus bar and that is located between the second comb electrode and the third electrode in a direction perpendicular to the electrode fingers.

[0257] <6> The elastic wave device according to any one of <1> to <5>, wherein through holes are provided in the third bus bar that overlaps the plurality of first electrode fingers in a planar view, and in portions between the plurality of first electrode fingers that are located between the first bus bars.

[0258] <7> An elastic wave device according to any one of <1> to <6>, wherein the plurality of third electrode fingers and the third bus bar are provided on the first main surface of the piezoelectric layer, and further comprising an insulator layer provided on the first main surface of the piezoelectric layer, and wherein some of the plurality of first electrode fingers and some of the third bus bar intersect via the insulator layer.

[0259] <8> The elastic wave device according to any one of <1> to <6>, wherein the plurality of third electrode fingers and the third bus bar are provided on the first main surface of the piezoelectric layer, and further includes an insulator layer provided on the first main surface of the piezoelectric layer, wherein some of the plurality of first electrode fingers and some of the third bus bar intersect via the insulator layer, and the first electrode fingers, the insulator layer, and the third bus bar are stacked in this order.

[0260] <9> A piezoelectric layer having a first main surface and a second main surface opposing each other; a first comb electrode provided on the first main surface of the piezoelectric layer, the first comb electrode having a first bus bar and a plurality of first electrode fingers, one end of each of which is connected to the first bus bar; a second comb electrode provided on the first main surface of the piezoelectric layer, the second comb electrode having a second bus bar and a plurality of second electrode fingers, one end of each of which is connected to the second bus bar and interdigitated with the plurality of first electrode fingers; a third electrode having a plurality of third electrode fingers provided on one of the first principal surface and the second principal surface of the piezoelectric layer so as to be aligned with the first electrode fingers and the second electrode fingers in a direction in which the second electrode fingers are aligned, and at least one third bus bar connecting the plurality of third electrode fingers to each other, and connected to a potential different from that of the first comb electrode and the second comb electrode; the other of the electrodes is connected to an output potential, and the order in which the first electrode finger, the second electrode finger, and the third electrode finger are arranged is an order in which, starting from the first electrode finger, the first electrode finger, the third electrode finger, the second electrode finger, and the third electrode finger form one period, and when a direction orthogonal to a direction in which the first electrode finger, the second electrode finger, and the third electrode finger extend is defined as an electrode finger orthogonal direction, a region in which the first electrode finger and the second electrode finger overlap in the electrode finger orthogonal direction is an intersection region, the first bus bar is located between the intersection region and one of the third bus bars, the first bus bar overlaps with the third electrode fingers in a planar view, the first bus bar and the third electrode fingers are electrically insulated from each other, and a through hole is provided in at least a part of a portion of the piezoelectric layer that is located between the intersection region and the first bus bar and that is located between the first comb electrode and the third electrode in a direction perpendicular to the electrode fingers.

[0261] <10> The elastic wave device according to <9>, further comprising: two third bus bars; in a planar view, the first bus bar is located between the intersection region and one of the third bus bars; the first bus bar overlaps the third electrode fingers in a planar view, and the first bus bar and the third electrode fingers are electrically insulated from each other; in a planar view, the second bus bar is located between the intersection region and the other of the third bus bars; the second bus bar overlaps the third electrode fingers in a planar view, and the second bus bar and the third electrode fingers are electrically insulated from each other; and a through hole is provided in at least a part of a portion of the piezoelectric layer that is located between the intersection region and the second bus bar and that is located between the second comb electrode and the third electrode in a direction perpendicular to the electrode fingers.

[0262] <11> The elastic wave device according to <9> or <10>, wherein through holes are provided in the third bus bar, which is arranged to sandwich the first bus bar together with the intersection region, and between portions of the plurality of third electrode fingers located between the first bus bars.

[0263] <12> The elastic wave device according to any one of <1> to <6> or <9> to <11>, wherein the plurality of third electrode fingers and the third bus bar are provided on the second main surface of the piezoelectric layer.

[0264] <13> A piezoelectric layer having a first main surface and a second main surface facing each other; a first comb electrode provided on the first main surface of the piezoelectric layer, the first comb electrode having a first bus bar and a plurality of first electrode fingers, one end of each of which is connected to the first bus bar; a second comb electrode provided on the first main surface of the piezoelectric layer, the second comb electrode having a second bus bar and a plurality of second electrode fingers, one end of each of which is connected to the second bus bar and interdigitated with the plurality of first electrode fingers; a third electrode including: a plurality of third electrode fingers provided on the first main surface of the piezoelectric layer so as to be aligned with the first electrode fingers and the second electrode fingers in a direction in which the fingers are aligned; a plurality of connection electrodes penetrating the piezoelectric layer and connected to the plurality of third electrode fingers, respectively; and at least one third bus bar provided on the second main surface and electrically connected to the plurality of third electrode fingers by the plurality of connection electrodes, and connected to a potential different from that of the first comb electrode and the second comb electrode; one of the first comb electrode and the second comb electrode is connected to an input potential, and the other of the first comb electrode and the second comb electrode is connected to an output potential; the order in which the first electrode finger, the second electrode finger, and the third electrode finger are arranged is an order in which, starting from the first electrode finger, the first electrode finger, the third electrode finger, the second electrode finger, and the third electrode finger form one period; and when a direction orthogonal to a direction in which the first electrode finger, the second electrode finger, and the third electrode finger extend is defined as an electrode finger orthogonal direction, a region where the first electrode fingers and the second electrode fingers overlap is an intersection region, one third bus bar is located between the intersection region and the first bus bar in a planar view, and the third bus bar overlaps the plurality of first electrode fingers in a planar view, and a through hole is provided in at least a part of a portion of the piezoelectric layer that is located between the intersection region and the first bus bar and that is located between the first electrode fingers and the third electrode fingers in a direction perpendicular to the electrode fingers.

[0265] <14> A piezoelectric layer having a first main surface and a second main surface facing each other; a first comb electrode provided on the first main surface of the piezoelectric layer, the first comb electrode having a first bus bar and a plurality of first electrode fingers, one end of each of which is connected to the first bus bar; a second comb electrode provided on the first main surface of the piezoelectric layer, the second comb electrode having a second bus bar and a plurality of second electrode fingers, one end of each of which is connected to the second bus bar and interdigitated with the plurality of first electrode fingers; a third electrode having a plurality of third electrode fingers provided on the first main surface of the piezoelectric layer so as to be aligned with the first electrode fingers and the second electrode fingers in a direction in which the second electrode fingers are aligned, a plurality of connection electrodes connected to the plurality of third electrode fingers, respectively, and a third bus bar electrically connected to the plurality of third electrode fingers by the plurality of connection electrodes, and connected to a potential different from that of the first comb electrode and the second comb electrode; one of the first interdigital electrode and the second interdigital electrode is connected to an input potential, and the other of the first interdigital electrode and the second interdigital electrode is connected to an output potential; the order in which the first electrode finger, the second electrode finger, and the third electrode finger are arranged is an order in which, starting from the first electrode finger, the first electrode finger, the third electrode finger, the second electrode finger, and the third electrode finger form one period; and when a direction perpendicular to a direction in which the first electrode finger, the second electrode finger, and the third electrode finger extend is defined as an electrode finger perpendicular direction, an area where the first electrode fingers and the second electrode fingers overlap is an intersection area, and in a planar view, one third bus bar is located between the intersection area and the first bus bar, and the third bus bar overlaps the plurality of first electrode fingers in a planar view; and a through hole is provided in at least a part of a portion of the piezoelectric layer that is located between the intersection area and the first bus bar and that is located between the first electrode fingers and the third electrode fingers in a direction perpendicular to the electrode fingers.

[0266] <15> The elastic wave device according to <14>, further comprising: a support provided on the first main surface of the piezoelectric layer; and a lid member provided on the support, the lid member having a third main surface located on the piezoelectric layer side and a fourth main surface facing the third main surface, wherein the third bus bar is provided on the third main surface of the lid member so as to face some of the third electrode fingers, and the connection electrodes are provided on at least the third electrode fingers and connect the third electrode fingers to the third bus bar.

[0267] <16> The elastic wave device according to <14>, further comprising: a plurality of conductive bonding members provided on the first main surface of the piezoelectric layer; and a mounting substrate bonded to the piezoelectric layer by the plurality of conductive bonding members, the mounting substrate having a fifth main surface located on the piezoelectric layer side and a sixth main surface facing the fifth main surface, wherein the third bus bar is provided on the fifth main surface of the mounting substrate so as to face some of the third electrode fingers, and the plurality of connection electrodes are provided on at least the third electrode fingers and connect the third bus bar to the third electrode fingers.

[0268] <17> The acoustic wave device according to any one of <1> to <16>, wherein the first interdigital transducer is connected to an input potential and the second interdigital transducer is connected to an output potential.

[0269] <18> The acoustic wave device according to any one of <1> to <16>, wherein the first interdigital transducer is connected to an output potential and the second interdigital transducer is connected to an input potential.

[0270] <19> The elastic wave device according to any one of <1> to <18>, further comprising a support member laminated on the piezoelectric layer, wherein an acoustic reflecting portion is formed on the support member at a position overlapping with the plurality of first electrode fingers, the plurality of second electrode fingers, and the plurality of third electrode fingers in a planar view, and wherein, when the longest distance among the center-to-center distance between adjacent first electrode fingers and the third electrode fingers and the center-to-center distance between adjacent second electrode fingers and the third electrode fingers is defined as p, and when the thickness of the piezoelectric layer is defined as d, d / p is 0.5 or less.

[0271] <20> The acoustic wave device according to <19>, wherein d / p is 0.24 or less.

[0272] <21> An elastic wave device described in <19> or <20>, wherein the acoustic reflection portion is a hollow portion, and the support member and the piezoelectric layer are arranged so that a portion of the support member and a portion of the piezoelectric layer face each other across the hollow portion.

[0273] <22> The elastic wave device described in <19> or <20>, wherein the acoustic reflection portion is an acoustic reflection film including a high acoustic impedance layer having a relatively high acoustic impedance and a low acoustic impedance layer having a relatively low acoustic impedance, and the support member and the piezoelectric layer are arranged so that at least a portion of the support member and at least a portion of the piezoelectric layer face each other with the acoustic reflection film in between.

[0274] <23> The elastic wave device according to any one of <19> to <22>, wherein, when a direction perpendicular to the direction in which the first electrode finger, the second electrode finger, and the third electrode finger extend is defined as an electrode finger orthogonal direction, a region where adjacent first electrode fingers and third electrode fingers overlap in the electrode finger orthogonal direction and between the centers of adjacent first electrode fingers and third electrode fingers, and a region where adjacent second electrode fingers and third electrode fingers overlap in the electrode finger orthogonal direction and between the centers of adjacent second electrode fingers and third electrode fingers are excitation regions, and when a metallization ratio of the first electrode fingers and the third electrode fingers and the second electrode fingers and the third electrode fingers to the excitation region is defined as MR, MR≦1.75(d / p)+0.075 is satisfied.

[0275] <24> The elastic wave device according to any one of <1> to <23>, wherein the piezoelectric layer is made of lithium niobate, and the Euler angles (φ, θ, ψ) of the lithium niobate constituting the piezoelectric layer are within the range of the following formula (1), formula (2), or formula (3): (within a range of 0°±10°, 0° to 25°, any ψ) ... formula (1) (within a range of 0°±10°, 25° to 100°, 0° to 75°[(1-(θ-50)２ / 2500) １／２ or 180°-75°[(1-(θ-50) ２ / 2500) １／２ ~180°) ...Equation (2) (within the range of 0°±10°, 180°-40°[(1-(ψ-90) ２ / 8100)] １／２ ~180°, any ψ) ...Equation (3)

[0276] REFERENCE SIGNS LIST 1...functional electrode 2, 2L...piezoelectric substrate 3...support member 4, 4A to 4O...piezoelectric layer 4a, 4b...first and second principal surfaces 4c...through hole 5...insulating layer 6...support substrate 7, 8...first and second interdigital electrodes 9...third electrode 10...acoustic wave device 10a...cavity 12 to 14...first to third bus bars 14a...common connection portion 14b...bar portion 15 to 17...first to third electrode fingers 19...insulating layer 21...functional electrode 24...third bus bar 29...third electrode 31, 41A...functional electrode 44A, 44B...third bus bar 49...third electrode 50a...cavity 51...functional electrode 53...support member 54A, 54B...third bus bar 54a...Common connection portion 54b...Bar portion 55, 56...First and second electrode fingers 57, 58...First and second comb-shaped electrodes 59...Third electrode 62...Dielectric layer 70a...Cavity portion 75...Insulating layer 78...Connection electrode 79...Third electrode 80...Acoustic wave device 81...Functional electrode 82...First support 82a...Opening 83...Second support 84...Cover member 84A...Cover member main body 84B...Inorganic oxide layer 84a, 84b...Third and fourth principal surfaces 85...Through electrode 86...External terminal 87...Bump 88...Connection electrode 89...Third electrode 90...Acoustic wave device 94...Sealing resin 95...Mounting substrate 95a, 95b...Fifth and sixth principal surfaces 96...External terminal 97...Bump 98: Electrode pad 113: Support member 115a to 115c: Low acoustic impedance layers 116a, 116b: High acoustic impedance layers 118: Acoustic reflection film 201: IDT electrode 204: Piezoelectric layer C: Excitation region E: Intersection region F: Element electrode formation portion

Claims

1. A piezoelectric layer having a first main surface and a second main surface opposing each other; a first comb electrode provided on the first main surface of the piezoelectric layer, the first comb electrode having a first bus bar and a plurality of first electrode fingers, one end of each connected to the first bus bar; a second comb electrode provided on the first main surface of the piezoelectric layer, the second comb electrode having a second bus bar and a plurality of second electrode fingers, one end of each connected to the second bus bar and interdigitated with the plurality of first electrode fingers; and a third electrode having a plurality of third electrode fingers provided on one of the first main surface and the second main surface of the piezoelectric layer, the third electrode being connected to a potential different from that of the first comb electrode and the second comb electrode, the third electrode being connected to a potential different from that of the first comb electrode and the second comb electrode, one of the first comb electrode and the second comb electrode is connected to an input potential, and the other of the first comb electrode and the second comb electrode is connected to an output potential; the order in which the first electrode finger, the second electrode finger, and the third electrode finger are arranged is an order in which, starting from the first electrode finger, the first electrode finger, the third electrode finger, the second electrode finger, and the third electrode finger form one period; when a direction orthogonal to a direction in which the first electrode finger, the second electrode finger, and the third electrode finger extend is defined as an electrode finger orthogonal direction, a region in which the first electrode finger and the second electrode finger overlap in the electrode finger orthogonal direction is an intersection region; in a plan view, one third bus bar is located between the intersection region and the first bus bar, and the third bus bar overlaps with the plurality of first electrode fingers in a plan view, and the third bus bar and the plurality of first electrode fingers are electrically insulated from each other; An elastic wave device, wherein a through hole is provided in at least a portion of the portion of the piezoelectric layer that is located between the intersection region and the first bus bar, and that is located between the first comb electrode and the third electrode in the direction perpendicular to the electrode fingers.

2. An elastic wave device as described in claim 1, wherein the through hole is provided in a portion of the piezoelectric layer located between the intersection region and the first bus bar, and located between the first electrode finger and the third electrode finger in the direction perpendicular to the electrode fingers.

3. An elastic wave device as described in claim 1 or 2, wherein the third bus bar includes a common connection portion connecting adjacent pairs of the third electrode fingers, the common connection portion having a portion adjacent to the first electrode finger in a direction perpendicular to the electrode fingers, and the through hole is provided in a portion of the piezoelectric layer located between the intersection region and the first bus bar, and located between the first electrode finger and the common connection portion in the direction perpendicular to the electrode fingers.

4. The elastic wave device according to any one of claims 1 to 3, comprising two third bus bars, one of the third bus bars being located between the intersection region and the first bus bar in a planar view, overlapping with the plurality of first electrode fingers in a planar view and electrically insulated from the plurality of first electrode fingers, and the other of the third bus bars being located between the intersection region and the second bus bar, overlapping with the plurality of second electrode fingers in a planar view and electrically insulated from the plurality of second electrode fingers, and a through hole being provided in at least a part of a portion of the piezoelectric layer that is located between the intersection region and the second bus bar and that is located between the second interdigital electrode and the third electrode in a direction perpendicular to the electrode fingers.

5. The elastic wave device according to any one of claims 1 to 3, comprising two third bus bars, one of which is located between the intersection region and the first bus bar in a plan view, and which overlaps with the plurality of first electrode fingers in a plan view, and which is electrically insulated from the plurality of first electrode fingers, and the second bus bar is located between the intersection region and the other of the third bus bars in a plan view, and which overlaps with the plurality of third electrode fingers in a plan view, and which is electrically insulated from the plurality of third electrode fingers, and a through hole is provided in at least a part of a portion of the piezoelectric layer that is located between the intersection region and the third bus bar and that is located between the second comb electrode and the third electrode in a direction perpendicular to the electrode fingers.

6. An elastic wave device according to any one of claims 1 to 5, wherein through holes are provided in the third bus bar that overlaps the plurality of first electrode fingers in a planar view, and in the portions between the plurality of first electrode fingers that are located between the first bus bars.

7. The elastic wave device according to any one of claims 1 to 6, wherein the plurality of third electrode fingers and the third bus bar are provided on the first main surface of the piezoelectric layer, and further comprising an insulating layer provided on the first main surface of the piezoelectric layer, and wherein some of the plurality of first electrode fingers and some of the third bus bar intersect with each other via the insulating layer.

8. The elastic wave device according to any one of claims 1 to 6, wherein the plurality of third electrode fingers and the third bus bar are provided on the first main surface of the piezoelectric layer, and further comprising an insulator layer provided on the first main surface of the piezoelectric layer, wherein some of the plurality of first electrode fingers and some of the third bus bar intersect with each other via the insulator layer, and wherein the first electrode fingers, the insulator layer, and the third bus bar are stacked in this order.

9. A piezoelectric layer having a first main surface and a second main surface opposing each other; a first comb electrode provided on the first main surface of the piezoelectric layer and having a first bus bar and a plurality of first electrode fingers, one end of each connected to the first bus bar; a second comb electrode provided on the first main surface of the piezoelectric layer and having a second bus bar and a plurality of second electrode fingers, one end of each connected to the second bus bar and interdigitated with the plurality of first electrode fingers; and a third electrode having a plurality of third electrode fingers provided on one of the first main surface and the second main surface of the piezoelectric layer so as to be aligned with the first electrode fingers and the second electrode fingers in the direction in which the first electrode fingers and the second electrode fingers are aligned in a plan view, and at least one third bus bar connecting the plurality of third electrode fingers together, and connected to a potential different from that of the first comb electrode and the second comb electrode. one of the first comb electrode and the second comb electrode is connected to an input potential, and the other of the first comb electrode and the second comb electrode is connected to an output potential; the order in which the first electrode finger, the second electrode finger, and the third electrode finger are arranged is an order in which, starting from the first electrode finger, the first electrode finger, the third electrode finger, the second electrode finger, and the third electrode finger form one period; when a direction orthogonal to a direction in which the first electrode finger, the second electrode finger, and the third electrode finger extend is defined as an electrode finger orthogonal direction, a region in which the first electrode finger and the second electrode finger overlap in the electrode finger orthogonal direction is an intersection region; in a plan view, the first bus bar is located between the intersection region and one of the third bus bars, and the first bus bar overlaps with the plurality of third electrode fingers in a plan view, and the first bus bar and the plurality of third electrode fingers are electrically insulated from each other; An elastic wave device, wherein a through hole is provided in at least a portion of the portion of the piezoelectric layer that is located between the intersection region and the first bus bar, and that is located between the first comb electrode and the third electrode in the direction perpendicular to the electrode fingers.

10. The elastic wave device according to claim 9, comprising two third bus bars, wherein in a planar view, the first bus bar is located between the intersection region and one of the third bus bars, the first bus bar overlaps with the plurality of third electrode fingers in a planar view, and the first bus bar and the plurality of third electrode fingers are electrically insulated from each other, and wherein in a planar view, the second bus bar is located between the intersection region and the other of the third bus bars, the second bus bar overlaps with the plurality of third electrode fingers in a planar view, and the second bus bar and the plurality of third electrode fingers are electrically insulated from each other, and a through hole is provided in at least a part of a portion of the piezoelectric layer that is located between the intersection region and the second bus bar and that is located between the second comb electrode and the third electrode in a direction perpendicular to the electrode fingers.

11. The elastic wave device according to claim 9 or 10, wherein through holes are provided between the third bus bars arranged to sandwich the first bus bars together with the intersection region, and between portions of the plurality of third electrode fingers located between the first bus bars.

12. The elastic wave device according to any one of claims 1 to 6 or 9 to 11, wherein the plurality of third electrode fingers and the third bus bar are provided on the second main surface of the piezoelectric layer.

13. A piezoelectric layer having a first main surface and a second main surface facing each other; a first comb electrode provided on the first main surface of the piezoelectric layer, the first comb electrode having a first bus bar and a plurality of first electrode fingers, one end of each of which is connected to the first bus bar; and a second comb electrode provided on the first main surface of the piezoelectric layer, the second comb electrode having a second bus bar and a plurality of second electrode fingers, one end of each of which is connected to the second bus bar and interdigitated with the plurality of first electrode fingers. a third electrode having: a plurality of third electrode fingers provided on the first main surface of the piezoelectric layer so as to be aligned with the first electrode fingers and the second electrode fingers in a direction in which the first electrode fingers and the second electrode fingers are aligned in a plan view; a plurality of connection electrodes penetrating the piezoelectric layer and connected to the plurality of third electrode fingers, respectively; and at least one third bus bar provided on the second main surface and electrically connected to the plurality of third electrode fingers by the plurality of connection electrodes, and connected to a potential different from that of the first comb electrode and the second comb electrode; an electrode-orthogonal direction is a direction orthogonal to a direction in which the first electrode fingers, the second electrode fingers, and the third electrode fingers extend, and a region where the first electrode fingers and the second electrode fingers overlap in the electrode-orthogonal direction is a crossing region; one third bus bar is located between the crossing region and the first bus bar in a planar view, and the third bus bar overlaps with the plurality of first electrode fingers in a planar view; and a through hole is provided in at least a part of a portion of the piezoelectric layer that is located between the crossing region and the first bus bar and that is located between the first electrode fingers and the third electrode fingers in the electrode-orthogonal direction.

14. A piezoelectric layer having a first main surface and a second main surface facing each other; a first comb electrode provided on the first main surface of the piezoelectric layer, the first comb electrode having a first bus bar and a plurality of first electrode fingers, one end of each of which is connected to the first bus bar; and a second comb electrode provided on the first main surface of the piezoelectric layer, the second comb electrode having a second bus bar and a plurality of second electrode fingers, one end of each of which is connected to the second bus bar and interdigitated with the plurality of first electrode fingers. a third electrode having a plurality of third electrode fingers provided on the first main surface of the piezoelectric layer so as to be aligned with the first electrode fingers and the second electrode fingers in a direction in which the first electrode fingers and the second electrode fingers are aligned in a plan view, a plurality of connection electrodes connected to the plurality of third electrode fingers, respectively, and a third bus bar electrically connected to the plurality of third electrode fingers by the plurality of connection electrodes, and connected to a potential different from that of the first comb electrode and the second comb electrode; one of the first comb electrode and the second comb electrode is connected to an input potential, and the other of the first comb electrode and the second comb electrode is connected to an output potential; and the arrangement order of the first electrode fingers, the second electrode fingers, and the third electrode fingers is an order in which, starting from the first electrode finger, the first electrode finger, the third electrode finger, the second electrode finger, and the third electrode finger form one period, an electrode-finger-orthogonal direction is a direction orthogonal to the direction in which the first electrode fingers, the second electrode fingers, and the third electrode fingers extend, and a region in which the first electrode fingers and the second electrode fingers overlap in the electrode-finger-orthogonal direction is a crossing region; in a planar view, one third bus bar is located between the crossing region and the first bus bar, and the third bus bar overlaps with the plurality of first electrode fingers in a planar view; and a through hole is provided in at least a part of a portion of the piezoelectric layer that is located between the crossing region and the first bus bar and that is located between the first electrode fingers and the third electrode fingers in the electrode-finger-orthogonal direction.

15. The elastic wave device of claim 14, further comprising: a support provided on the first main surface of the piezoelectric layer; and a lid member provided on the support and having a third main surface located on the piezoelectric layer side and a fourth main surface facing the third main surface, wherein the third bus bar is provided on the third main surface of the lid member so as to face some of the third electrode fingers, and the plurality of connection electrodes are provided on at least the third electrode fingers and connect the third bus bar to the third electrode fingers.

16. The elastic wave device of claim 14, further comprising: a plurality of conductive bonding members provided on the first main surface of the piezoelectric layer; and a mounting substrate bonded to the piezoelectric layer by the plurality of conductive bonding members, the mounting substrate having a fifth main surface located on the piezoelectric layer side and a sixth main surface facing the fifth main surface, wherein the third bus bar is provided on the fifth main surface of the mounting substrate so as to face some of the plurality of third electrode fingers, and the plurality of connection electrodes are provided on at least the plurality of third electrode fingers to connect the third bus bar to the plurality of third electrode fingers.

17. The acoustic wave device according to any one of claims 1 to 16, wherein the first interdigital electrode is connected to an input potential, and the second interdigital electrode is connected to an output potential.

18. The acoustic wave device according to any one of claims 1 to 16, wherein the first interdigital electrode is connected to an output potential, and the second interdigital electrode is connected to an input potential.

19. The elastic wave device according to any one of claims 1 to 18, further comprising a support member laminated on the piezoelectric layer, wherein acoustic reflecting portions are formed on the support member at positions overlapping with the plurality of first electrode fingers, the plurality of second electrode fingers, and the plurality of third electrode fingers in a planar view, and wherein, when the longest distance among the center-to-center distances between the adjacent first electrode fingers and the third electrode fingers and the center-to-center distances between the adjacent second electrode fingers and the third electrode fingers is p and the thickness of the piezoelectric layer is d, d / p is 0.5 or less.

20. The acoustic wave device according to claim 19, wherein d / p is 0.24 or less.

21. An elastic wave device according to claim 19 or 20, wherein the acoustic reflection portion is a cavity, and the support member and the piezoelectric layer are arranged so that a portion of the support member and a portion of the piezoelectric layer face each other across the cavity.

22. An elastic wave device according to claim 19 or 20, wherein the acoustic reflection portion is an acoustic reflection film including a high acoustic impedance layer with a relatively high acoustic impedance and a low acoustic impedance layer with a relatively low acoustic impedance, and the support member and the piezoelectric layer are arranged so that at least a portion of the support member and at least a portion of the piezoelectric layer face each other with the acoustic reflection film in between.

23. The elastic wave device according to any one of claims 19 to 22, wherein, when a direction perpendicular to the direction in which the first electrode finger, the second electrode finger, and the third electrode finger extend is defined as an electrode finger perpendicular direction, excitation regions include a region where adjacent first electrode fingers and third electrode fingers overlap in the electrode finger perpendicular direction and between the centers of adjacent first electrode fingers and third electrode fingers, and a region where adjacent second electrode fingers and third electrode fingers overlap in the electrode finger perpendicular direction and between the centers of adjacent second electrode fingers and third electrode fingers, and wherein MR is the metallization ratio of the first electrode fingers and third electrode fingers and the second electrode fingers and third electrode fingers to the excitation region, and MR satisfies MR≦1.75(d / p)+0.

075.

24. The acoustic wave device according to any one of claims 1 to 23, wherein the piezoelectric layer is made of lithium niobate, and the Euler angles (φ, θ, ψ) of the lithium niobate constituting the piezoelectric layer are within the range of the following formula (1), formula (2), or formula (3): (within a range of 0°±10°, 0° to 25°, any ψ) ... formula (1) (within a range of 0°±10°, 25° to 100°, 0° to 75°[(1-(θ-50) ２ / 2500) １／２ or 180°-75°[(1-(θ-50) ２ / 2500) １／２ ~180°) ...Equation (2) (within the range of 0°±10°, 180°-40°[(1-(ψ-90) ２ / 8100)] １／２ ~180°, any ψ) ...Equation (3)

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