Elastic wave device

Abstract

Provided is an elastic wave device that makes it possible to suppress deterioration of filter characteristics.　An elastic wave device 10 according to the present invention comprises: a piezoelectric layer 4; a first interdigital electrode 7; a second interdigital electrode 8; a plurality of third electrode fingers 17 each provided on one of a first main surface 4a and a second main surface 4b of the piezoelectric layer 4 so as to be arranged adjacent to first electrode fingers 15 and second electrode fingers 16 in a direction in which the first electrode fingers 15 and the second electrode fingers 16 are arranged in a plan view; and a third electrode 9 that has at least one third bus bar 14 connecting the plurality of third electrode fingers 17 to each other, and is connected to a potential different from those of the first interdigital electrode 7 and the second interdigital electrode 8. Either or both of the third bus bar 14 and portions of the plurality of first electrode fingers 15 overlapping the third bus bar 14 in a plan view are provided on a non-piezoelectric region.

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 principal surface and a second principal surface opposing each other; a first comb electrode provided on the first principal surface of the piezoelectric layer, the first comb electrode having a first bus bar and a plurality of first electrode fingers, each having one end connected to the first bus bar; and a second comb electrode provided on the first principal surface of the piezoelectric layer, the second comb electrode having 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 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 a direction in which the first electrode fingers and the second electrode fingers are aligned when viewed from above, 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 first interdigital electrode and the second interdigital electrode is connected to an input potential, the order in which the first electrode finger, the second electrode finger, and the third electrode finger are arranged is such that, starting from the first electrode finger, one period includes the first electrode finger, the third electrode finger, the second electrode finger, and the third electrode finger, 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 and the third electrode finger are arranged in a direction perpendicular to the electrode finger direction, The region where the second electrode fingers overlap is an intersection region, and in a planar 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 planar view, and the third bus bar and the plurality of first electrode fingers are electrically insulated, and at least one of the portions of the plurality of first electrode fingers that overlap with the third bus bar in a planar view and the third bus bar is provided in a portion that does not have piezoelectricity.

[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 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 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 a direction in which the first electrode fingers and the second electrode fingers are aligned when viewed from above, 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 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 two electrode fingers overlap is an intersection region, and 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, and at least one of the portions of the plurality of third electrode fingers that overlap with the first bus bar in a planar view and the first bus bar is provided in a portion that does not have piezoelectricity.

[0009] In yet another broad aspect of the elastic wave device according to the present invention, there is provided an elastic wave device comprising: a piezoelectric layer having first and second principal surfaces opposing each other; a first comb electrode provided on the first principal 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 principal 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 plurality of third electrode fingers provided on the first 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 in a plan view; a plurality of connection electrodes penetrating the piezoelectric layer and connected to the plurality of third electrode fingers; and a plurality of connection electrodes provided on the second principal surface, the plurality of connection electrodes being aligned with the plurality of third electrode fingers. and a third electrode having at least one third bus bar electrically connected to the plurality of third electrode fingers by an electrode 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 being connected to an input potential and the other of the first comb electrode and the second comb electrode being connected to an output potential, the order in which the first electrode fingers, the second electrode fingers and the third electrode fingers 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, one third bus bar overlaps with the plurality of first electrode fingers in a planar view, and at least one of the portions of the plurality of first electrode fingers that overlap with the third bus bar in a planar view and the third bus bar is provided in a portion that does not have piezoelectricity.

[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 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; 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; and a plurality of connection electrodes connected to the plurality of third electrode fingers, respectively, which are connected by the plurality of connection electrodes to form a plurality of interdigitated wave elements. a third electrode having a third bus bar electrically connected to the third electrode fingers 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 being connected to an input potential and the other of the first comb electrode and the second comb electrode being connected to an output potential, the order in which the first electrode fingers, the second electrode fingers, and the third electrode fingers 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, one third bus bar overlaps with the plurality of first electrode fingers in a planar view, and the portion of at least one of the plurality of first electrode fingers and the plurality of third electrode fingers that overlaps with the third bus bar in a planar view is provided in a portion that does not have piezoelectricity.

[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 preferred embodiment of the present invention. FIG. 8 is a schematic plan view of an elastic wave device according to a second modified preferred embodiment of the first preferred embodiment of the present invention. FIG. 9 is a schematic plan view of an elastic wave device according to a third modified preferred embodiment of the first preferred embodiment of the present invention. FIG. 10 is a schematic plan view of an elastic wave device according to a second preferred embodiment of the present invention. FIG. 11 is a schematic front cross-sectional view illustrating a portion where one first electrode finger and a third bus bar intersect with an insulating layer interposed therebetween in a modified preferred embodiment of the second preferred embodiment of the present invention. FIG. 12 is a schematic plan view of an elastic wave device according to a third preferred embodiment of the present invention. FIG. 13 is a schematic plan view of an elastic wave device according to a fourth preferred embodiment of the present invention. FIG. 14 is a schematic plan view of an elastic wave device according to a fifth preferred embodiment of the present invention. FIG. 15 is a schematic plan view of an elastic wave device according to a sixth preferred embodiment of the present invention. FIG. 16 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. 17 is a schematic plan view of an elastic wave device according to a seventh preferred embodiment of the present invention. FIG. 18 is a schematic plan view of an elastic wave device according to an eighth preferred embodiment of the present invention. FIG. 19 is a schematic plan view of an elastic wave device according to a ninth preferred embodiment of the present invention. FIG. 20 is a schematic cross-sectional view taken along line II in FIG. 19 . FIG. 21 is a schematic cross-sectional view taken along line III-III in FIG. 19 . FIG. 22 is a schematic front cross-sectional view of an elastic wave device according to a tenth preferred embodiment of the present invention. FIG. 23 is a schematic front cross-sectional view showing an enlarged portion of an elastic wave device according to a tenth preferred embodiment of the present invention. FIG. 24 is a schematic plan view showing an electrode configuration on a first main surface of a piezoelectric layer according to a tenth preferred embodiment of the present invention. 25 and 26 are schematic cross-sectional front views of an elastic wave device according to an eleventh preferred embodiment of the present invention, respectively, and are enlarged schematic cross-sectional front views of a portion of the elastic wave device according to the eleventh preferred embodiment of the present invention.FIG. 27 is a schematic plan view showing an electrode configuration on a first main surface of a piezoelectric layer according to an eleventh preferred embodiment of the present invention. FIG. 28 is a schematic plan view of an elastic wave device according to a twelfth preferred embodiment of the present invention. FIG. 29 is a schematic cross-sectional view taken along line II-II in FIG. 28 . FIG. 30 is a schematic plan view of an elastic wave device according to a first modified example of the twelfth preferred embodiment of the present invention. FIG. 31 is a schematic plan view of an elastic wave device according to a second modified example of the twelfth preferred embodiment of the present invention. FIG. 32 is a schematic plan view of an elastic wave device according to a third modified example of the twelfth preferred embodiment of the present invention. FIG. 33 is a schematic plan 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 portion where one first electrode finger and a third bus bar intersect with an insulating layer interposed therebetween in a modified example of the thirteenth preferred embodiment of the present invention. FIG. 35 is a schematic plan view of an elastic wave device according to a fourteenth preferred embodiment of the present invention. FIG. 36 is a schematic plan view of an elastic wave device according to a fifteenth preferred embodiment of the present invention. FIG. 37 is a schematic plan view of an elastic wave device according to a sixteenth preferred embodiment of the present invention. FIG. 38 is a schematic plan view of an elastic wave device according to a seventeenth preferred embodiment of the present invention. FIG. 39 is a schematic plan view of an elastic wave device according to a modification of the seventeenth preferred embodiment of the present invention. FIG. 40 is a schematic plan view of an elastic wave device according to an eighteenth preferred embodiment of the present invention. FIG. 41 is a schematic plan view of an elastic wave device according to a nineteenth preferred embodiment of the present invention. FIG. 42 is a schematic plan view of an elastic wave device according to a twentieth preferred embodiment of the present invention. FIG. 43 is a schematic cross-sectional view taken along line III-III in FIG. 42. FIG. 44 is a schematic plan view illustrating an electrode configuration on a first main surface of a piezoelectric layer according to a twenty-first preferred embodiment of the present invention. FIG. 45 is a schematic cross-sectional view taken along line III-III in FIG. 44. FIG. 46 is a schematic cross-sectional view illustrating a portion corresponding to the cross section shown in FIG. 45 in a modification of the twenty-first preferred embodiment of the present invention. FIG. 47 is a schematic plan view illustrating an electrode configuration on a first main surface of a piezoelectric layer according to a twenty-second preferred embodiment of the present invention. Fig. 48 is a schematic cross-sectional view taken along line III-III in Fig. 47. Fig. 49 is a schematic cross-sectional view showing a portion of a modification of the 22nd embodiment of the present invention, corresponding to the cross section shown in Fig. 48. Fig. 50 is a schematic front cross-sectional view of an elastic wave device according to a 23rd embodiment of the present invention.Fig. 51 is a schematic plan view of an elastic wave device of a reference example. Fig. 52 is a diagram showing the relationship between d / p and the fractional bandwidth of an elastic wave device of a reference example. Fig. 53 is a diagram showing the relationship between the fractional bandwidth and the normalized magnitude of spurious signals in an elastic wave device of a reference example. Fig. 54 is a diagram showing the relationship between d / p, the metallization ratio MR, and the fractional bandwidth. Fig. 55 shows LiNbO when d / p approaches 0. ３ FIG. 10 is a diagram showing a map of fractional bandwidths versus Euler angles (0°, θ, ψ) of the .lambda.

[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, non-piezoelectric portions in a piezoelectric layer, which will be described later, and each electrode are indicated by hatching. In FIG. 2, the reference potential symbol is used to indicate that a third electrode, which will be described later, is connected to the reference potential. In schematic plan views other than FIG. 2, non-piezoelectric portions and electrodes may be similarly indicated by hatching, and the reference potential symbol may also 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. As shown in FIG. 2 , in this embodiment, the piezoelectric layer 4 has a non-piezoelectric portion 4c. The non-piezoelectric portion 4c is a portion that does not have piezoelectricity. On the other hand, portions of the piezoelectric layer 4 other than the non-piezoelectric portion 4c have piezoelectricity.

[0019] In this embodiment, the non-piezoelectric portion 4 c includes the entire portion in the thickness direction of a portion of the piezoelectric layer 4. Therefore, in the non-piezoelectric portion 4 c, neither the first principal surface 4 a nor the second principal surface 4 b has piezoelectricity. However, it is sufficient that the non-piezoelectric portion 4 c includes at least a portion of the portion of the piezoelectric layer 4 that is located on the first principal surface 4 a.

[0020] In this specification, a piezoelectric layer having no piezoelectricity does not necessarily mean that the piezoelectricity of the piezoelectric layer is 0. In this specification, a piezoelectric layer having such minute piezoelectricity that the acoustic wave device does not exhibit filter characteristics is also considered to be a piezoelectric layer having no piezoelectricity.

[0021] The functional electrode 1 is provided on the first principal surface 4 a of the piezoelectric layer 4. In this specification, "provided on the first principal surface 4 a" includes both a case where the functional electrode 1 is provided directly on the first principal surface 4 a and a case where the functional electrode 1 is provided indirectly on the first principal surface 4 a via another member. In this embodiment, the functional electrode 1 is provided directly on the first principal surface 4 a.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] More specifically, the third bus bar 14 includes a plurality of common electrode portions 14a and a bar portion 14b. Adjacent pairs of third electrode fingers 17 are connected to each other by the common electrode portion 14a. The bar portion 14b is provided across the plurality of common electrode portions 14a. Note that the third bus bar 14 does not necessarily have to include a plurality of common electrode portions 14a.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] FIG. 3 is a schematic cross-sectional view taken along line II-II in FIG.

[0037] 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.

[0038] 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 electrode 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 electrode portions 14a.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 2, the piezoelectric layer 4 has a non-piezoelectric portion 4c. The boundary between the non-piezoelectric portion 4c and the portion having piezoelectricity in the piezoelectric layer 4 includes the edge portion on the crossing region E side of the third bus bar 14. More specifically, the boundary includes the edge portion on the crossing region E side of the multiple common electrode portions 14a in the third bus bar 14. The boundary also extends in the direction perpendicular to the electrode fingers outside the edge portion on the crossing region E side of the third bus bar 14. In this embodiment, all of the portion of the functional electrode 1 located on the third bus bar 14 side of the boundary is provided in the non-piezoelectric portion 4c.

[0044] On the other hand, the entire portion of the functional electrode 1 located on the crossing region E side of the boundary between the non-piezoelectric portion 4c and the piezoelectric portion of the piezoelectric layer 4 is provided in the piezoelectric portion. Therefore, the portion of the piezoelectric layer 4 located in the crossing region E is the piezoelectric portion.

[0045] In this embodiment, the piezoelectric layer 4 is made of lithium niobate. In this specification, a certain component made of a certain material includes the case where the component contains a trace amount of impurities to the extent that the electrical characteristics of the acoustic wave device are not significantly deteriorated. In this embodiment, the Euler angles (φ, θ, ψ) of the piezoelectric portion of the piezoelectric layer 4 are (0°, 0°, 90°). The Euler angles (φ, θ, ψ) of the piezoelectric portion are not limited to the above. On the other hand, the polarization direction of the non-piezoelectric portion 4c is not constant. Therefore, the Euler angles (φ, θ, ψ) are not defined for the non-piezoelectric portion 4c.

[0046] 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 .

[0047] 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.

[0048] 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.

[0049] A feature of this embodiment is that the portions of the plurality of first electrode fingers 15 that overlap with the third bus bar 14 in a plan view and the third bus bar 14 are provided in the non-piezoelectric portion 4c of the piezoelectric layer 4. Note that it is sufficient that at least one of the portions of the plurality of first electrode fingers 15 that overlap with the third bus bar 14 in a plan view and the third bus bar 14 is provided in a non-piezoelectric portion. This makes it possible to suppress ripples in the frequency characteristics and to prevent deterioration of the filter characteristics. Details of this are shown below by comparing this embodiment with a comparative example.

[0050] 4 , the comparative example differs from the first embodiment in that the piezoelectric layer 104 does not have a non-piezoelectric portion. Therefore, the comparative example differs from the first embodiment in that the portions of the plurality of first electrode fingers 15 that overlap with the third bus bar 14 in a plan view and that the third bus bar 14 is provided in a portion that has piezoelectricity.

[0051] 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.

[0052] 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

[0053] 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.

[0054] 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.

[0055] 2 , in the first embodiment, the portions of the third busbar 14 other than the portions overlapping with the first electrode fingers 15 in a plan 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 are electrodes connected to different potentials. This is also true for the comparative example shown in FIG.

[0056] 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 in portions that have piezoelectricity, which generates unwanted waves and deteriorates the filter characteristics.

[0057] 2, the portions of the first electrode fingers 15 that overlap with the third bus bar 14 in a plan view, and the third bus bar 14, are provided in the non-piezoelectric portion 4c of the piezoelectric layer 4. This makes it difficult for unwanted waves to be generated, thereby suppressing deterioration of the filter characteristics.

[0058] It is only necessary that at least one of the portions of the plurality of first electrode fingers 15 that overlap with the third bus bar 14 in a plan view and the third bus bar 14 is provided in a portion that does not have piezoelectricity. In this case, as in the first embodiment, it is possible to suppress unwanted waves and prevent deterioration of the filter characteristics.

[0059] The configuration of the first embodiment will be described in further detail below.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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 .

[0066] In the first embodiment, the third bus bar 14 and portions of the first electrode fingers 15 that overlap with the third bus bar 14 in a plan view are provided in the non-piezoelectric portion 4c of the piezoelectric layer 4. The first bus bar 12 and portions of the first electrode fingers 15 that are located between the third bus bar 14 and the first bus bar 12 are also provided in the non-piezoelectric portion 4c.

[0067] As described above, it is sufficient that at least one of the portions of the plurality of first electrode fingers 15 that overlap with the third bus bar 14 in a plan view and the third bus bar 14 is provided in a non-piezoelectric portion. Below, first to third modified examples of the first embodiment are shown, which differ from the first embodiment only in the positions of the non-piezoelectric portions. In the first to third modified examples, as in the first embodiment, unwanted waves can be suppressed and degradation of the filter characteristics can be suppressed.

[0068] 7, the portions of the piezoelectric layer 4A that overlap with the third bus bar 14 in a plan view are designated as non-piezoelectric portions 4c, although the non-piezoelectric portions 4c also include portions that do not overlap with the third bus bar 14 in a plan view.

[0069] Specifically, the edge of non-piezoelectric portion 4c on the crossing region E side includes the edge of the multiple common electrode portions 14a of third busbar 14 on the crossing region E side, and extends in the direction perpendicular to the electrode fingers. The edge of non-piezoelectric portion 4c on the first busbar 12 side includes the edge of the multiple common electrode portions 14a of third busbar 14 on the first busbar 12 side, and extends in the direction perpendicular to the electrode fingers. When viewed from the electrode finger extension direction, non-piezoelectric portion 4c does not extend outside third busbar 14.

[0070] In addition, when the third bus bar 14 does not include the common electrode portion 14a, only the portion of the piezoelectric layer 4A that overlaps with the third bus bar 14 in a plan view is configured as the non-piezoelectric portion 4c.

[0071] In the second modified example shown in Figure 8, the portion of the piezoelectric layer 4B that overlaps with the third bus bar 14 in a planar view, and the portion between the third bus bar 14 and the intersection region E, etc., are made into non-piezoelectric portions 4c.

[0072] Specifically, the edge of the non-piezoelectric portion 4c on the crossing region E side includes the edge of the crossing region E on the third bus bar 14 side. The edge of the non-piezoelectric portion 4c on the crossing region E side also extends in the direction orthogonal to the electrode fingers outside the edge of the crossing region E on the third bus bar 14 side. However, when viewed from the direction in which the electrode fingers extend, the non-piezoelectric portion 4c does not extend outside the third bus bar 14. The edge of the non-piezoelectric portion 4c on the first bus bar 12 side includes the edge of the multiple common electrode portions 14a of the third bus bar 14 on the first bus bar 12 side, and extends in the direction orthogonal to the electrode fingers.

[0073] Therefore, the portions of the plurality of first electrode fingers 15 and the plurality of third electrode fingers 17 that are located between the third bus bar 14 and the intersection region E are provided in the non-piezoelectric portion 4 c. The portions of the plurality of first electrode fingers 15 that overlap with the third bus bar 14 in a plan view, and the third bus bar 14, are also provided in the non-piezoelectric portion 4 c.

[0074] In this modification, 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 provided in portions that do not have piezoelectricity, thereby making it possible to further suppress unwanted waves and to further prevent deterioration of the filter characteristics.

[0075] 9 , the boundary between the non-piezoelectric portion 4c and the piezoelectric portion of the piezoelectric layer 4C includes the edge portion on the third bus bar 14 side in the crossing region E. The boundary also extends in the direction perpendicular to the electrode fingers outside the edge portion on the third bus bar 14 side in the crossing region E. The entire portion of the functional electrode 1 located on the third bus bar 14 side of the boundary is provided in the non-piezoelectric portion 4c.

[0076] Specifically, the portions of the plurality of first electrode fingers 15 and the plurality of third electrode fingers 17 that are located between the intersection region E and the third bus bar 14 are provided in the non-piezoelectric portion 4 c. The portions of the plurality of first electrode fingers 15 that overlap with the third bus bar 14 in a plan view, and the third bus bar 14, are also provided in the non-piezoelectric portion 4 c. In addition, the portions of the plurality of first electrode fingers 15 that are located between the third bus bar 14 and the first bus bar 12, and the first bus bar 12 are also provided in the non-piezoelectric portion 4 c.

[0077] In this modification, the electrodes that are located outside the crossing region E, adjacent to each other in the direction perpendicular to the electrode fingers, and connected to different potentials are provided in portions that do not have piezoelectricity, so that, similar to the second modification, unwanted waves can be further suppressed and degradation of the filter characteristics can be further suppressed.

[0078] The configurations of the first to third 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 electrode portion 14a, the edge portion of the third bus bar 14 is the edge portion of the bar portion 14b.

[0079] FIG. 10 is a schematic plan view of an elastic wave device according to a second preferred embodiment of the present invention.

[0080] This embodiment differs from the first embodiment in that the third bus bar 24 in the functional electrode 21 does not include the common electrode portion 14a shown in FIG. 2 . The third bus bar 24 is provided over a plurality of third electrode fingers 17 and a plurality of insulator layers 19. Except for the above, the elastic wave device of this embodiment has a similar configuration to the elastic wave device 10 of the first embodiment. Therefore, like the first embodiment, this embodiment can effectively suppress unwanted waves and effectively prevent degradation of the filter characteristics.

[0081] 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 4 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.

[0082] 11 , 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 4 side. More specifically, one insulator layer 19 is provided between the third bus bar 24 and one first electrode finger 15.

[0083] 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 from each other. The configuration in this modification 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 modification.

[0084] In this modification, as in the second embodiment, it is possible to effectively suppress unwanted waves and effectively prevent deterioration of filter characteristics.

[0085] FIG. 12 is a schematic plan view of an elastic wave device according to a third preferred embodiment of the present invention.

[0086] This embodiment differs from the second embodiment in the configuration of the functional electrode 31 and the position of the non-piezoelectric portion 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.

[0087] 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.

[0088] In the piezoelectric layer 4D, the boundary between the non-piezoelectric portion 4c and the portion having piezoelectricity includes the edge portion on the crossing region E side of the third bus bar 24. The boundary also extends in the direction perpendicular to the electrode fingers outside the edge portion on the crossing region E side of the third bus bar 24. In this embodiment, all of the portion of the functional electrode 31 located on the third bus bar 24 side of the boundary is provided in the non-piezoelectric portion 4c. On the other hand, all of the portion of the functional electrode 31 located on the crossing region E side of the boundary is provided in the portion having piezoelectricity.

[0089] In this embodiment, the portions of the third bus bar 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-mentioned portions of the third bus bar 24 and the second electrode fingers 16 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. These portions are provided in the non-piezoelectric portion 4c of the piezoelectric layer 4D. This makes it possible to effectively suppress unwanted waves and effectively prevent deterioration of the filter characteristics.

[0090] 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. 10 , 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.

[0091] 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 7 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.

[0092] At least one of the portions of the second electrode fingers 16 that overlap with the third bus bar 24 in a plan view and the third bus bar 24 may be located in a non-piezoelectric portion. In this case, a portion including an edge portion of the intersection region E on the third bus bar 24 side may be the boundary between the non-piezoelectric portion and the piezoelectric portion. The boundary may extend outside the edge portion of the intersection region E on the third bus bar 24 side, for example, in a direction perpendicular to the electrode fingers. At least one of the second electrode fingers 16 and the third electrode fingers 17, a portion located between the third bus bar 24 and the intersection region E, may be located in a non-piezoelectric portion. This effectively suppresses unwanted waves. This configuration can be applied to configurations of the present invention other than the third embodiment in which the third bus bar 24 is located between the intersection region E and the second bus bar 13.

[0093] Furthermore, the portion of the plurality of second electrode fingers 16 located between the third bus bar 24 and the second bus bar 13 may be provided in a portion that does not have piezoelectricity. In addition, the second bus bar 13 may be provided in a portion that does not have piezoelectricity. These configurations 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.

[0094] FIG. 13 is a schematic plan view of an elastic wave device according to a fourth preferred embodiment of the present invention.

[0095] 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 non-piezoelectric portions 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.

[0096] Some of the insulator layers 19 each cover a part of one first electrode finger 15. The remaining insulator layers 19 each cover a part of one second electrode finger 16.

[0097] 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.

[0098] 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.

[0099] In this embodiment, the piezoelectric layer 4E has two non-piezoelectric portions 4c. One of the non-piezoelectric portions 4c is arranged in the same manner as in the first and second embodiments. Specifically, the boundary between the non-piezoelectric portion 4c and the portion having piezoelectricity includes the edge of the third bus bar 44A on the crossing region E side. The boundary also extends in the direction perpendicular to the electrode fingers outside the edge of the third bus bar 44A on the crossing region E side. The entire portion of the functional electrode 41 located on the third bus bar 44A side of the boundary is provided in the non-piezoelectric portion 4c.

[0100] The other non-piezoelectric portion 4c is arranged in the same manner as in the third embodiment. Specifically, when viewed in the direction perpendicular to the electrode fingers, the boundary between the non-piezoelectric portion 4c and the piezoelectric portion includes the edge of the third bus bar 44B on the crossing region E side. The boundary also extends in the direction perpendicular to the electrode fingers to the outside of the edge of the third bus bar 44B on the crossing region E side. The entire portion of the functional electrode 41 located on the third bus bar 44B side of the boundary is provided in the non-piezoelectric portion 4c.

[0101] 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.

[0102] These portions are provided in the non-piezoelectric portions 4c of the piezoelectric layer 4E, thereby making it possible to effectively suppress unwanted waves and effectively prevent deterioration of the filter characteristics.

[0103] Note that it is sufficient that at least one of the portions of the plurality of first electrode fingers 15 that overlap with the third bus bar 44A in a plan view and the third bus bar 44A is provided in a non-piezoelectric portion. In this case, the first electrode fingers 15 may be connected to either an input potential or an output potential. However, it is preferable that at least one of the portions of the plurality of second electrode fingers 16 that overlap with the third bus bar 44B in a plan view and the third bus bar 44B is also provided in a non-piezoelectric portion. This makes it possible to effectively suppress unwanted waves.

[0104] FIG. 14 is a schematic plan view of an elastic wave device according to a fifth preferred embodiment of the present invention.

[0105] 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 non-piezoelectric portion 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] The piezoelectric layer 4F has multiple non-piezoelectric portions 4c. One of the non-piezoelectric portions 4c is arranged in the same manner as one of the non-piezoelectric portions 4c in the fourth embodiment. The boundary between the other non-piezoelectric portion 4c and the portion having piezoelectricity includes the edge of the second bus bar 13 on the crossing region E side. The boundary also extends in the direction perpendicular to the electrode fingers, extending outward from the edge of the second bus bar 13 on the crossing region E side. The entire portion of the functional electrode 41A located on the second bus bar 13 side of the boundary is provided in the non-piezoelectric portion 4c.

[0110] 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. Therefore, the above portion of the second busbar 13 and the third electrode finger 17 are electrodes located outside the intersection region E, adjacent to each other in the electrode finger orthogonal direction, and 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 electrodes located outside the intersection region E, adjacent to each other in the electrode finger orthogonal direction, and connected to different potentials.

[0111] These portions are provided in the non-piezoelectric portions 4c of the piezoelectric layer 4F, thereby making it possible to effectively suppress unwanted waves and effectively prevent deterioration of the filter characteristics.

[0112] 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.

[0113] FIG. 15 is a schematic plan view of an elastic wave device according to a sixth preferred embodiment of the present invention.

[0114] This embodiment differs from the fifth embodiment in the positional relationship between the first interdigital electrode 7 and the third electrode 49. This embodiment also differs from the fifth embodiment in the position of the non-piezoelectric portion 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.

[0115] 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 the insulator layer 19.

[0116] 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.

[0117] 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.

[0118] The piezoelectric layer 4G has multiple non-piezoelectric portions 4c. The boundary between one non-piezoelectric portion 4c and the portion having piezoelectricity includes the edge portion on the crossing region E side of the first bus bar 12. The boundary also extends in the direction perpendicular to the electrode fingers, outside the edge portion on the crossing region E side of the first bus bar 12. All of the portion of the functional electrode 41B located on the first bus bar 12 side of the boundary is provided in the non-piezoelectric portion 4c. The other non-piezoelectric portion 4c is arranged in the same manner as the non-piezoelectric portion 4c on the second bus bar 13 side in the fifth embodiment.

[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. Therefore, the above portion of the first busbar 12 and the third electrode finger 17 are electrodes located outside the intersection region E, adjacent to each other in the electrode finger orthogonal direction, and 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 electrodes located outside the intersection region E, adjacent to each other in the electrode finger orthogonal direction, and connected to different potentials.

[0120] These portions are provided in the non-piezoelectric portions 4c of the piezoelectric layer 4G, thereby making it possible to effectively suppress unwanted waves and effectively prevent deterioration of the filter characteristics.

[0121] The arrangement of the non-piezoelectric portion 4 c 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 non-piezoelectric portion 4 c. As with the sixth embodiment, the modified example of the sixth embodiment can also effectively suppress unwanted waves and effectively suppress deterioration of the filter characteristics.

[0122] 16 , similar to the sixth embodiment, the piezoelectric layer 4H has two non-piezoelectric portions 4c. The boundary between one of the non-piezoelectric portions 4c and the piezoelectric portion includes the edge portion on the third bus bar 44A side in the crossing region E. The boundary also extends in the direction perpendicular to the electrode fingers outside the edge portion on the third bus bar 44A side in the crossing region E. The entire portion of the functional electrode 41B located on the third bus bar 44A side of the boundary is provided in the non-piezoelectric portion 4c.

[0123] Specifically, the portions of the plurality of first electrode fingers 15 and the plurality of third electrode fingers 17 that are located between the intersection region E and the first bus bar 12 are provided in the non-piezoelectric portion 4c. The portions of the plurality of third electrode fingers 17 that overlap with the first bus bar 12 in a plan view, and the first bus bar 12, are also provided in the non-piezoelectric portion 4c. These configurations 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.

[0124] 16 , the portions of the plurality of third electrode fingers 17 that are located between the third bus bar 44A and the first bus bar 12 are provided in the non-piezoelectric portion 4c. In addition, the third bus bar 44A is also provided in the non-piezoelectric portion 4c. These configurations 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.

[0125] The boundary between the other non-piezoelectric portion 4c and the portion having piezoelectricity includes the edge portion on the third bus bar 44B side in the crossing region E. The boundary also extends in the direction perpendicular to the electrode fingers outside the edge portion on the third bus bar 44B side in the crossing region E. The entire portion of the functional electrode 41B located on the third bus bar 44B side of the boundary is provided in the non-piezoelectric portion 4c.

[0126] Specifically, the portions of the plurality of second electrode fingers 16 and the plurality of third electrode fingers 17 that are located between the intersection region E and the second bus bar 13 are provided in the non-piezoelectric portion 4c. The portions of the plurality of third electrode fingers 17 that overlap with the second bus bar 13 in a plan view, and the second bus bar 13, are also provided in the non-piezoelectric portion 4c. These configurations 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.

[0127] 16 , the portions of the plurality of third electrode fingers 17 that are located between the third bus bar 44B and the second bus bar 13 are provided in the non-piezoelectric portion 4c. In addition, the third bus bar 44B is also provided in the non-piezoelectric portion 4c. These configurations 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.

[0128] In this modification, 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 provided in portions that do not have piezoelectricity, thereby making it possible to further suppress unwanted waves and to further prevent deterioration of the filter characteristics.

[0129] It is sufficient that at least one of the portions of the plurality of third electrode fingers 17 that overlap with the first bus bar 12 in a plan view and the first bus bar 12 is provided in a portion that does not have piezoelectricity. In this case, the portions of at least one of the plurality of first electrode fingers 15 and the plurality of third electrode fingers 17 that are located between the intersection region E and the first bus bar 12 may be provided in a portion that does not have piezoelectricity.

[0130] Alternatively, at least one of the portions of the plurality of third electrode fingers 17 that overlap with the second bus bar 13 in a plan view and the second bus bar 13 may be provided in a portion that does not have piezoelectricity. In this case, the portions of at least one of the plurality of second electrode fingers 16 and the plurality of third electrode fingers 17 that are located between the intersection region E and the second bus bar 13 may be provided in a portion that does not have piezoelectricity.

[0131] FIG. 17 is a schematic plan view of an elastic wave device according to a seventh preferred embodiment of the present invention.

[0132] This embodiment differs from the second embodiment in the positional relationship between the first interdigital 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 non-piezoelectric portions 4c in the piezoelectric layer 4I. 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.

[0133] 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. 15 . Specifically, as shown in Fig. 17 , 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.

[0134] The non-piezoelectric portion 4c in the piezoelectric layer 4I is provided in the same manner as the non-piezoelectric portion 4c located closer to the third bus bar 44A than the crossing region E in the sixth embodiment shown in Fig. 15. Specifically, as shown in Fig. 17, the boundary between the non-piezoelectric portion 4c and the portion having piezoelectricity includes the edge of the first bus bar 12 on the crossing region E side. The boundary also extends in the direction perpendicular to the electrode fingers outside the edge of the first bus bar 12 on the crossing region E side. The entire portion of the functional electrode 51 located closer to the first bus bar 12 than the boundary is provided in the non-piezoelectric portion 4c.

[0135] 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. These portions are provided in the non-piezoelectric portions 4c of the piezoelectric layer 4I. This makes it possible to effectively suppress unwanted waves and effectively prevent deterioration of the filter characteristics.

[0136] FIG. 18 is a schematic plan view of an elastic wave device according to the eighth preferred embodiment of the present invention.

[0137] This embodiment differs from the second embodiment in that a third electrode 29 is provided on the second main surface 4b of the piezoelectric layer 4. Specifically, the third electrode 29 is provided directly on the second main surface 4b. This embodiment also differs from the second embodiment in that the insulator layer 19 shown in FIG. 10 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.

[0138] In the present embodiment, the arrangement of the third electrodes 29 in a plan view is the same as that in the second embodiment. Therefore, in a plan view, a plurality of third electrode fingers 17 are provided on the second main surface 4 b of the piezoelectric layer 4 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 consists of 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.

[0139] The arrangement of the non-piezoelectric portions 4c in the piezoelectric layer 4 is the same as in the second embodiment. Therefore, the boundary between the non-piezoelectric portions 4c and the piezoelectric portion in the piezoelectric layer 4 includes the edge portion on the crossing region E side of the third bus bar 24. The non-piezoelectric portions 4c include the entire portion of the piezoelectric layer 4 in the thickness direction.

[0140] The portions of the first electrode fingers 15 that overlap with the third bus bar 24 in a plan view and the third bus bar 24 are provided in the non-piezoelectric portion 4 c. This makes it possible to effectively suppress unwanted waves and effectively prevent deterioration of the filter characteristics. Note that it is sufficient that at least one of the portions of the first electrode fingers 15 that overlap with the third bus bar 24 in a plan view and the third bus bar 24 is provided in a non-piezoelectric portion.

[0141] The configuration in which 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 eighth embodiment. For example, the third electrode in the first embodiment, the third to seventh embodiments, and each of the modified examples may be provided on the second main surface.

[0142] In the first to eighth 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. The ninth embodiment shows an example in which the third bus bar and the third electrode fingers are provided on different main surfaces.

[0143] Fig. 19 is a schematic plan view of an elastic wave device according to a ninth preferred embodiment of the present invention. Fig. 20 is a schematic cross-sectional view taken along line II in Fig. 19. Fig. 21 is a schematic cross-sectional view taken along line III-III in Fig. 19.

[0144] 19 , this embodiment differs from the second embodiment in the configuration of the third electrode 69. As shown in Fig. 20 , this embodiment also differs from the second embodiment in the configuration of the insulating layer 65. 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.

[0145] 21 , the third electrode 69 has a third bus bar 24, a plurality of third electrode fingers 17, and a plurality of connection electrodes 68. 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 4. Specifically, the plurality of third electrode fingers 17 are provided directly on the first main surface 4 a.

[0146] On the other hand, the third bus bar 24 is provided on the second main surface 4 b of the piezoelectric layer 4. Specifically, the third bus bar 24 is provided directly on the second main surface 4 b. 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 4. However, the direction in which the third bus bar 24 extends is not limited to the above.

[0147] The plurality of connection electrodes 68 penetrate the piezoelectric layer 4. Each connection electrode 68 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 68.

[0148] As shown in Fig. 20 , a hollow portion is provided in the insulating layer 65. That is, the hollow portion is configured as a cavity 60a in the insulating layer 65. In this embodiment, the insulating layer 65 covers the second main surface 4b of the piezoelectric layer 4. As shown in Fig. 21 , the insulating layer 65 covers the third bus bar 24 of the third electrode 69. However, the insulating layer 65 does not have to cover the second main surface 4b or the third bus bar 24. For example, the insulating layer 65 may be provided in the same manner as the insulating layer 5 shown in Fig. 1 .

[0149] The third electrode 69 of this embodiment differs from the second embodiment in that it includes a plurality of connection electrodes 68. However, the arrangement of the third electrode 69 in a plan view shown in FIG. 19 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 4 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.

[0150] 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.

[0151] The arrangement of the non-piezoelectric portions 4c in the piezoelectric layer 4 is the same as in the second embodiment. Therefore, the boundary between the non-piezoelectric portions 4c and the piezoelectric portion in the piezoelectric layer 4 includes the edge portion on the crossing region E side of the third bus bar 24. The non-piezoelectric portions 4c include the entire portion of the piezoelectric layer 4 in the thickness direction.

[0152] The portions of the first electrode fingers 15 that overlap with the third bus bar 24 in a plan view and the third bus bar 24 are provided in the non-piezoelectric portion 4 c. This makes it possible to effectively suppress unwanted waves and effectively prevent deterioration of the filter characteristics. Note that it is sufficient that at least one of the portions of the first electrode fingers 15 that overlap with the third bus bar 24 in a plan view and the third bus bar 24 is provided in a non-piezoelectric portion.

[0153] In the first to ninth 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 tenth and eleventh embodiments.

[0154] Fig. 22 is a schematic front cross-sectional view of an elastic wave device according to a tenth preferred embodiment of the present invention. In Fig. 22, 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 also applies to the other schematic front cross-sectional views. Note that Fig. 22 shows a cross section of a portion of the third electrode where the third bus bar and the connection electrode are not provided.

[0155] The elastic wave device 70 of this preferred embodiment has a wafer level package (WLP) structure. Specifically, a first support 72, which serves as a support according to the present invention, is provided on a piezoelectric substrate 2. More specifically, the first support 72 is provided on a first main surface 4a of the piezoelectric layer 4. The first support 72 has a frame-like shape. Therefore, the first support 72 has an opening 72a.

[0156] The first main surface 4 a of the piezoelectric layer 4 is provided with a first comb electrode, a second comb electrode, and a plurality of third electrode fingers of the functional electrode 71. When the portion of the piezoelectric layer 4 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 72 a.

[0157] A plurality of second supports 73 are provided on the first main surface 4a of the piezoelectric layer 4. The second supports 73 have a columnar shape. The plurality of second supports 73 are located within the openings 72a of the first support 72. In this embodiment, the first support 72 and the second support 73 are each a laminate of a plurality of metal layers. Note that the second support 73 does not necessarily have to be provided.

[0158] A lid member 74 is provided on the first support 72 and the plurality of second supports 73 so as to cover the opening 72a, thereby forming a hollow space surrounded by the piezoelectric substrate 2, the first support 72, and the lid member 74. An element electrode forming portion F of the piezoelectric layer 4 is located within this hollow space.

[0159] The lid member 74 has a lid member main body 74A and an inorganic oxide layer 74B. The lid member main body 74A has a pair of main surfaces that face each other. One of the main surfaces of the lid member main body 74A faces the piezoelectric substrate 2. The inorganic oxide layer 74B is provided on both main surfaces of the lid member main body 74A.

[0160] More specifically, the lid member 74 has a third principal surface 74a and a fourth principal surface 74b. The third principal surface 74a and the fourth principal surface 74b face each other. Of the third principal surface 74a and the fourth principal surface 74b, the third principal surface 74a is the principal surface facing the piezoelectric substrate 2. The principal surface of the lid member 74 is the surface of the inorganic oxide layer 74B. More specifically, the principal surface of the lid member 74 is the surface of the inorganic oxide layer 74B in the portion that is provided on the principal surface of the lid member main body 74A. However, the inorganic oxide layer 74B does not necessarily have to be provided. In this case, the third principal surface 74a and the fourth principal surface 74b of the lid member 74 are the principal surfaces of the lid member main body 74A.

[0161] In this embodiment, the lid member main body 74A is a silicon substrate. The support substrate 6 of the piezoelectric substrate 2 is also a silicon substrate. However, the materials of the support substrate 6 and the lid member main body 74A are not limited to those mentioned above.

[0162] A through electrode 75 is provided in the lid member 74. More specifically, a through hole is provided in the lid member 74. The through hole is provided so as to reach the second support 73. The through electrode 75 is provided in the through hole. One end of the through electrode 75 is connected to the second support 73. An external terminal 76 is provided so as to be connected to the other end of the through electrode 75. The external terminal 76 is configured as an electrode pad. In this embodiment, the through electrode 75 and the external terminal 76 are provided as a single unit. However, the through electrode 75 and the external terminal 76 may also be provided separately.

[0163] The inorganic oxide layer 74B of the lid member 74 is provided not only on the main surface of the lid member main body 74A but also inside the through-hole. More specifically, inside the through-hole, the inorganic oxide layer 74B is located between the through-electrode 75 and the lid member main body 74A. The inorganic oxide layer 74B is provided so as to cover the vicinity of the outer periphery of the external terminal 76. The inorganic oxide layer 74B extends between the external terminal 76 and the lid member main body 74A. The inorganic oxide layer 74B is, for example, a silicon oxide layer. However, the material of the inorganic oxide layer 74B is not limited to the above.

[0164] The inorganic oxide layer 74B does not have to be provided inside the through-hole of the lid member main body 74A. The inorganic oxide layer 74B does not have to be provided on the external terminal 76 or between the external terminal 76 and the lid member main body 74A.

[0165] Bumps 77 are provided as conductive bonding members on portions of the plurality of external terminals 76 that are not covered with the inorganic oxide layer 74B. The bumps 77 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.

[0166] FIG. 23 is a schematic enlarged front cross-sectional view illustrating a portion of the elastic wave device according to the tenth preferred embodiment.

[0167] The third bus bar 24 of the third electrode 79 is provided on the third main surface 74 a of the cover member 74. The third bus bar 24 faces some of the plurality of third electrode fingers 17.

[0168] The plurality of connection electrodes 78 of the third electrode 79 are provided between the first main surface 4 a of the piezoelectric layer 4 and the lid member 74. The connection electrodes 78 are columnar electrodes. More specifically, each connection electrode 78 is provided over one third electrode finger 17 and the piezoelectric layer 4. Each connection electrode 78 is connected to the third bus bar 24. That is, the plurality of connection electrodes 78 connect the third bus bar 24 and the plurality of third electrode fingers 17.

[0169] However, it is sufficient that each connection electrode 78 is provided on at least the third electrode finger 17. At least one connection electrode 78 may be provided only on the third electrode finger 17. In this case, the connection electrode 78 is not provided directly on the piezoelectric layer 4.

[0170] Fig. 24 is a schematic plan view showing an electrode configuration on a first main surface of a piezoelectric layer in the tenth embodiment. Note that Fig. 23 above is a schematic cross-sectional view showing a portion along line III-III in Fig. 24.

[0171] 24 , 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 plurality of 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 75 and bumps 77 shown in FIG.

[0172] 24 , in this embodiment, the boundary between the non-piezoelectric portion 4 c and the portion having piezoelectricity in the piezoelectric layer 4 includes the edge portion on the crossing region E side of the portion overlapping with the third bus bar 24 in a plan view. The non-piezoelectric portion 4 c includes at least a portion of the piezoelectric layer 4 that is located on the first main surface 4 a.

[0173] The portions of the plurality of first electrode fingers 15 and the plurality of third electrode fingers 17 that overlap with the third bus bar 24 in a plan view are provided in the non-piezoelectric portion 4 c. This makes it possible to effectively suppress unwanted waves and effectively prevent deterioration of the filter characteristics. Note that it is only necessary that the portions of at least one of the plurality of first electrode fingers 15 and the plurality of third electrode fingers 17 that overlap with the third bus bar 24 in a plan view are provided in a portion that does not have piezoelectricity.

[0174] 22 provides a high degree of layout freedom on the third principal surface 74a of the lid member 74. Therefore, wiring for connecting the third electrode 79 shown in FIG. 23 to a reference potential can be easily provided on the third principal surface 74a without increasing the size of the elastic wave device 70. In addition, the width of the third bus bar 24 can be easily increased. This allows the electrical resistance of the third electrode 79 to be easily and effectively reduced.

[0175] 22 may be provided on a layer other than the piezoelectric layer 4 of the piezoelectric substrate 2. 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 4 may be located inside the outer periphery of the insulating layer 5 or the support substrate 6. In this case, the first support 72 may be provided on the insulating layer 5 or the support substrate 6.

[0176] 24 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.

[0177] FIG. 25 is a schematic front cross-sectional view of an elastic wave device according to an eleventh preferred embodiment of the present invention.

[0178] The acoustic wave device 80 has a configuration in which an acoustic wave resonator is mounted on a mounting substrate 85. Specifically, the acoustic wave device 80 has a CSP (chip size package) structure. The mounting substrate 85 is a printed circuit board (PCB). In this embodiment, the material of the mounting substrate 85 is high-temperature co-fired ceramic (HTCC). However, the material of the mounting substrate 85 is not limited to the above.

[0179] On the other hand, the support substrate 6 of the piezoelectric substrate 2 is a silicon substrate. However, the material of the support substrate 6 is not limited to the above.

[0180] A plurality of conductive bonding members are provided on the piezoelectric substrate 2. More specifically, a plurality of electrode pads 88 are provided on the piezoelectric substrate 2. A conductive bonding member is provided on each of the plurality of electrode pads 88. In this embodiment, the conductive bonding members are bumps 87. The bumps 87 may be, for example, solder bumps or Au bumps.

[0181] The piezoelectric substrate 2 is bonded to a mounting substrate 85 by a plurality of conductive bonding members. The mounting substrate 85 has a fifth main surface 85a and a sixth main surface 85b. The fifth main surface 85a and the sixth main surface 85b face each other. Of the fifth main surface 85a and the sixth main surface 85b, the fifth main surface 85a is the main surface on the piezoelectric substrate 2 side. A sealing resin 84 is provided on the fifth main surface 85a so as to cover the support substrate 6 of the piezoelectric substrate 2. The piezoelectric substrate 2, the sealing resin 84, and the mounting substrate 85 form a hollow portion. An element electrode formation portion F of the piezoelectric layer 4 is located within this hollow portion.

[0182] A plurality of external terminals 86 are provided on a sixth main surface 85b of the mounting substrate 85. A plurality of via electrodes and a plurality of wirings are provided inside the mounting substrate 85. Each external terminal 86 is electrically connected to the via electrodes and wirings inside the mounting substrate 85. Each of the plurality of external terminals 86 is electrically connected to an external reference potential or signal potential via a bump, a conductive adhesive, or the like.

[0183] FIG. 26 is a schematic enlarged front cross-sectional view illustrating a portion of the elastic wave device according to the eleventh preferred embodiment.

[0184] In this embodiment, the third bus bar 24 of the third electrode 79 is provided on the fifth main surface 85 a of the mounting substrate 85. The third bus bar 24 faces some of the plurality of third electrode fingers 17.

[0185] The multiple connection electrodes 78 of the third electrode 79 are provided between the first main surface 4 a of the piezoelectric layer 4 and the fifth main surface 85 a of the mounting substrate 85. The connection electrodes 78 are columnar electrodes. More specifically, each connection electrode 78 is provided on only one third electrode finger 17. Each connection electrode 78 is connected to the third bus bar 24. That is, the multiple connection electrodes 78 connect the third bus bar 24 and the multiple third electrode fingers 17. It is sufficient that each connection electrode 78 is provided on at least the third electrode finger 17. At least one connection electrode 78 may be provided across the third electrode finger 17 and the piezoelectric layer 4.

[0186] Fig. 27 is a schematic plan view showing an electrode configuration on a first main surface of a piezoelectric layer in the eleventh embodiment. Note that Fig. 26 above is a schematic cross-sectional view showing a portion along line III-III in Fig. 27.

[0187] 27 , 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 85 a of the mounting substrate 85 shown in FIG. 25 , wiring and via electrodes within the mounting substrate 85, and external terminals 86.

[0188] 27 , in this embodiment, the boundary between the non-piezoelectric portion 4 c and the portion having piezoelectricity in the piezoelectric layer 4 includes the edge portion on the crossing region E side of the portion overlapping with the third bus bar 24 in a plan view. The non-piezoelectric portion 4 c includes at least a portion of the piezoelectric layer 4 that is located on the first main surface 4 a.

[0189] The portions of the plurality of first electrode fingers 15 and the plurality of third electrode fingers 17 that overlap with the third bus bar 24 in a plan view are provided in the non-piezoelectric portion 4 c. This makes it possible to effectively suppress unwanted waves and effectively prevent deterioration of the filter characteristics. Note that it is only necessary that the portions of at least one of the plurality of first electrode fingers 15 and the plurality of third electrode fingers 17 that overlap with the third bus bar 24 in a plan view are provided in a portion that does not have piezoelectricity.

[0190] 25 , there is a high degree of freedom in the layout of the fifth main surface 85 a of the mounting substrate 85. Therefore, wiring for connecting the third electrode 79 shown in FIG. 26 to a reference potential can be easily provided on the fifth main surface 85 a without increasing the size of the acoustic 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 79 to be easily and effectively reduced.

[0191] 27 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.

[0192] In the tenth and eleventh embodiments, the arrangement of the third bus bar 24 in plan view and the arrangement of the non-piezoelectric portions 4 c in the piezoelectric layer 4 are the same as those in the second embodiment shown in Fig. 10. However, it is sufficient that the portions of at least one of the plurality of first electrode fingers 15 and the plurality of third electrode fingers 17 that overlap with the third bus bar 24 in plan view are provided in a portion that does not have piezoelectricity. In this case, for example, the boundary between the non-piezoelectric portion 4 c and the portion that has piezoelectricity may include the edge portion of the intersection region E on the third bus bar 24 side in plan view.

[0193] Alternatively, in plan view, the third bus bar 24 may be located between the intersection region E and the second bus bar 13. In this case, it is sufficient that the portion of at least one of the plurality of second electrode fingers 16 and the plurality of third electrode fingers 17 that overlaps with the third bus bar 24 in plan view is provided in a portion that does not have piezoelectricity.

[0194] In the first to eleventh embodiments, examples have been shown in which the piezoelectric layer has a non-piezoelectric portion. In the first to eleventh embodiments, the portion that does not have piezoelectricity in the present invention is a non-piezoelectric portion. Note that the portion that does not have piezoelectricity in the present invention may be a dielectric layer or a resin layer. This example is shown in the twelfth to nineteenth embodiments. Note that in the twelfth to nineteenth embodiments, the positional relationship between the functional electrode and the portion that does not have piezoelectricity when viewed in plan is the same as in any of the first to eighth embodiments. In the twelfth to nineteenth embodiments, as in the first to eighth embodiments, unwanted waves can be suppressed and degradation of filter characteristics can be suppressed.

[0195] Fig. 28 is a schematic plan view of an elastic wave device according to a twelfth preferred embodiment of the present invention. Fig. 29 is a schematic cross-sectional view taken along line II-II in Fig. 28. Note that the dielectric layer 92 is indicated by hatching in Fig. 28. The same applies to the other schematic plan views.

[0196] 28 , the twelfth embodiment differs from the first embodiment in that the piezoelectric layer 104 does not have a non-piezoelectric portion. As shown in FIG. 29 , the twelfth embodiment also differs from the first embodiment in that a dielectric layer 92 is provided directly on the first main surface 4 a of the piezoelectric layer 104. Apart from the above, the elastic wave device of the twelfth embodiment has a similar configuration to the elastic wave device 10 of the first embodiment.

[0197] As described above, in this specification, the term "provided on the principal surface of the piezoelectric layer" also includes the case where the functional electrode 1 is indirectly provided on the principal surface of the piezoelectric layer. A part of the functional electrode 1 is indirectly provided on the first principal surface 4 a of the piezoelectric layer 104 via the dielectric layer 92. Therefore, a part of the functional electrode 1 is provided on the first principal surface 4 a of the piezoelectric layer 104, and is provided on the dielectric layer 92, which is a part that does not have piezoelectricity.

[0198] Specifically, a part of the first electrode fingers 15 and the third bus bar 14 are provided on the dielectric layer 92. In addition, the insulator layer 19 is also provided on the dielectric layer 92.

[0199] 28 , in the twelfth embodiment, the positional relationship between the functional electrode 1 and the dielectric layer 92 in a plan view is the same as the positional relationship between the functional electrode 1 and the non-piezoelectric portion in a plan view in the first embodiment. Specifically, in the twelfth embodiment, the third bus bar 14 and portions of the plurality of first electrode fingers 15 that overlap with the third bus bar 14 in a plan view are provided on the dielectric layer 92. In addition, the first bus bar 12 and portions of the plurality of first electrode fingers 15 that are located between the third bus bar 14 and the first bus bar 12 are also provided on the dielectric layer 92.

[0200] It should be noted that a resin layer may be provided in place of the dielectric layer 92. This also applies to the thirteenth to twenty-second embodiments and their modifications described below.

[0201] The following describes first to third modified examples of the twelfth embodiment. In the first to third modified examples, as in the twelfth embodiment, it is possible to suppress unwanted waves and to prevent degradation of the filter characteristics.

[0202] 30 , a dielectric layer 92 is provided in a portion of the piezoelectric layer 104 that overlaps with the third bus bar 14 in a plan view. However, the dielectric layer 92 is also provided in a portion that does not overlap with the third bus bar 14 in a plan view.

[0203] Specifically, the edge portion of the dielectric layer 92 on the crossing region E side overlaps the edge portions of the multiple common electrode portions 14a of the third bus bar 14 on the crossing region E side in a plan view, and extends in the direction perpendicular to the electrode fingers. The edge portion of the dielectric layer 92 on the first bus bar 12 side overlaps the edge portions of the multiple common electrode portions 14a of the third bus bar 14 on the first bus bar 12 side in a plan view, and extends in the direction perpendicular to the electrode fingers. When viewed from the electrode finger extension direction, the dielectric layer 92 does not extend outside the third bus bar 14.

[0204] If the third bus bar 14 does not include the common electrode portion 14a, the dielectric layer 92 is provided only in the portion that overlaps with the third bus bar 14 in a plan view.

[0205] In the second modified example of the twelfth embodiment shown in Figure 31, a dielectric layer 92 is provided in the piezoelectric layer 104, such as in the portion that overlaps with the third bus bar 14 in a planar view, and in the portion between the third bus bar 14 and the intersection region E.

[0206] Specifically, the edge of the dielectric layer 92 on the crossing region E side overlaps the edge of the crossing region E on the third bus bar 14 side in plan view. The edge of the dielectric layer 92 on the crossing region E side extends in the direction orthogonal to the electrode fingers, also outside the edge of the crossing region E on the third bus bar 14 side. However, when viewed from the electrode finger extension direction, the dielectric layer 92 does not extend outside the third bus bar 14. The edge of the dielectric layer 92 on the first bus bar 12 side overlaps the edge of the multiple common electrode portions 14a of the third bus bar 14 on the first bus bar 12 side in plan view, and extends in the direction orthogonal to the electrode fingers.

[0207] Therefore, portions of the plurality of first electrode fingers 15 and the plurality of third electrode fingers 17 that are located between the third bus bar 14 and the intersection region E are provided on the dielectric layer 92. Portions of the plurality of first electrode fingers 15 that overlap with the third bus bar 14 in a plan view, and the third bus bar 14, are also provided on the dielectric layer 92.

[0208] 32 , the edge of the dielectric layer 92 on the crossing region E side overlaps the edge of the dielectric layer 92 on the third bus bar 14 side in plan view. The edge of the dielectric layer 92 on the crossing region E side extends in the direction perpendicular to the electrode fingers, also outside the edge of the crossing region E on the third bus bar 14 side. The entire portion of the functional electrode 1 located closer to the third bus bar 14 than the crossing region E is provided on the dielectric layer 92.

[0209] Specifically, portions of the plurality of first electrode fingers 15 and the plurality of third electrode fingers 17 that are located between the intersection region E and the third bus bar 14 are provided on the dielectric layer 92. Portions of the plurality of first electrode fingers 15 that overlap with the third bus bar 14 in a plan view, and the third bus bar 14, are also provided on the dielectric layer 92. In addition, portions of the plurality of first electrode fingers 15 that are located between the third bus bar 14 and the first bus bar 12, and the first bus bar 12 are also provided on the dielectric layer 92.

[0210] FIG. 33 is a schematic plan view of an elastic wave device according to a thirteenth preferred embodiment of the present invention.

[0211] The thirteenth embodiment differs from the second embodiment in that the piezoelectric layer 104 does not have a non-piezoelectric portion and that a dielectric layer 92 is provided directly on the first main surface 4 a of the piezoelectric layer 104. Except for the above differences, the elastic wave device of the thirteenth embodiment has the same configuration as the elastic wave device of the second embodiment.

[0212] In the thirteenth embodiment, the positional relationship between the functional electrode 21 and the dielectric layer 92 in a plan view is the same as the positional relationship between the functional electrode 21 and the non-piezoelectric portion in a plan view in the second embodiment. Specifically, in the thirteenth embodiment, the portions of the plurality of first electrode fingers 15 that overlap with the third bus bar 24 in a plan view and the third bus bar 24 are provided on the dielectric layer 92. The portions of the plurality of first electrode fingers 15 that are located between the third bus bar 24 and the first bus bar 12, and the first bus bar 12 are also provided on the dielectric layer 92.

[0213] In the thirteenth 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 104 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.

[0214] 34 , in a portion where the third bus bar 24 is laminated with the insulator layer 19 and the first electrode fingers 15, the third bus bar 24, the insulator layer 19, and the first electrode fingers 15 are laminated in this order from the piezoelectric layer 104 side. More specifically, one insulator layer 19 is provided between the third bus bar 24 and one first electrode finger 15. The third bus bar 24 is provided on the dielectric layer 92, as in the thirteenth embodiment.

[0215] 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 from each other.

[0216] In this modification, as in the thirteenth embodiment, it is possible to effectively suppress unwanted waves and effectively prevent deterioration of the filter characteristics.

[0217] FIG. 35 is a schematic plan view of an elastic wave device according to a fourteenth preferred embodiment of the present invention.

[0218] The fourteenth embodiment differs from the third embodiment in that the piezoelectric layer 104 does not have a non-piezoelectric portion and that a dielectric layer 92 is provided directly on the first main surface 4 a of the piezoelectric layer 104. Except for the above differences, the elastic wave device of the fourteenth embodiment has the same configuration as the elastic wave device of the third embodiment.

[0219] In the fourteenth embodiment, the third bus bar 24 is provided between the intersection region E and the second bus bar 13. In the fourteenth embodiment, the positional relationship between the functional electrode 31 and the dielectric layer 92 in a plan view is the same as the positional relationship between the functional electrode 31 and the non-piezoelectric portion in a plan view in the third embodiment. Specifically, in the fourteenth embodiment, the third bus bar 24 and portions of the plurality of second electrode fingers 16 that overlap with the third bus bar 24 in a plan view are provided on the dielectric layer 92. The second bus bar 13 and portions of the plurality of second electrode fingers 16 that are located between the third bus bar 24 and the second bus bar 13 are also provided on the dielectric layer 92.

[0220] FIG. 36 is a schematic plan view of an elastic wave device according to a fifteenth preferred embodiment of the present invention.

[0221] The fifteenth embodiment differs from the fourth embodiment in that the piezoelectric layer 104 does not have a non-piezoelectric portion and that a dielectric layer 92 is provided directly on the first main surface 4 a of the piezoelectric layer 104. In the fifteenth embodiment, two dielectric layers 92 are provided on the first main surface 4 a. Except for the above points, the elastic wave device of the fifteenth embodiment has a similar configuration to the elastic wave device of the fourth embodiment.

[0222] In the fifteenth embodiment, the third electrode 49 has two third bus bars 44A and 44B. One third bus bar 44A is provided between the intersection region E and the first bus bar 12. The other third bus bar 44B is provided between the intersection region E and the second bus bar 13.

[0223] In the fifteenth embodiment, the positional relationship between the functional electrode 41 and the dielectric layer 92 in a plan view is the same as the positional relationship between the functional electrode 41 and the non-piezoelectric portion in a plan view in the fourth embodiment. Specifically, in the fifteenth embodiment, the third bus bar 44A and portions of the plurality of first electrode fingers 15 that overlap with the third bus bar 44A in a plan view are provided on one dielectric layer 92. The first bus bar 12 and portions of the plurality of first electrode fingers 15 that are located between the third bus bar 44A and the first bus bar 12 are also provided on the dielectric layer 92.

[0224] The third bus bar 44B and portions of the second electrode fingers 16 that overlap with the third bus bar 44B in a plan view are provided on the other dielectric layer 92. The second bus bar 13 and portions of the second electrode fingers 16 that are located between the third bus bar 44B and the second bus bar 13 are also provided on the dielectric layer 92.

[0225] FIG. 37 is a schematic plan view of an elastic wave device according to a sixteenth preferred embodiment of the present invention.

[0226] The sixteenth embodiment differs from the fifth embodiment in that the piezoelectric layer 104 does not have a non-piezoelectric portion and that a dielectric layer 92 is provided directly on the first main surface 4 a of the piezoelectric layer 104. In the sixteenth embodiment, two dielectric layers 92 are provided on the first main surface 4 a. Except for the above points, the elastic wave device of the sixteenth embodiment has a similar configuration to the elastic wave device of the fifth embodiment.

[0227] In the sixteenth embodiment, the third electrode 49 has two third bus bars, a third bus bar 44A and a third bus bar 44B. One third bus bar 44A is provided between the intersection region E and the first bus bar 12. The other third bus bar 44B is provided so as to sandwich the second bus bar 13 together with the intersection region E. In other words, the second bus bar 13 is provided between the intersection region E and the third bus bar 44B.

[0228] In the sixteenth embodiment, the positional relationship between the functional electrode 41A and the dielectric layer 92 in a plan view is the same as the positional relationship between the functional electrode 41A and the non-piezoelectric portion in a plan view in the fifth embodiment. Specifically, in the sixteenth embodiment, the third bus bar 44A and portions of the plurality of first electrode fingers 15 that overlap with the third bus bar 44A in a plan view are provided on one dielectric layer 92. The first bus bar 12 and portions of the plurality of first electrode fingers 15 that are located between the third bus bar 44A and the first bus bar 12 are also provided on the dielectric layer 92.

[0229] The second bus bar 13 and the portions of the third electrode fingers 17 that overlap with the second bus bar 13 in a plan view are provided on the other dielectric layer 92. The third bus bar 44B and the portions of the third electrode fingers 17 that are located between the second bus bar 13 and the third bus bar 44B are also provided on the dielectric layer 92.

[0230] FIG. 38 is a schematic plan view of an elastic wave device according to a seventeenth preferred embodiment of the present invention.

[0231] The seventeenth embodiment differs from the sixth embodiment in that the piezoelectric layer 104 does not have a non-piezoelectric portion and that a dielectric layer 92 is provided directly on the first main surface 4 a of the piezoelectric layer 104. In the seventeenth embodiment, two dielectric layers 92 are provided on the first main surface 4 a. Except for the above points, the elastic wave device of the seventeenth embodiment has a similar configuration to the elastic wave device of the sixth embodiment.

[0232] In the seventeenth embodiment, the third electrode 49 has two third bus bars, a third bus bar 44A and a third bus bar 44B. One of the third bus bars 44A is arranged to sandwich the first bus bar 12 together with the intersection region E. In other words, the first bus bar 12 is arranged between the intersection region E and the third bus bar 44A. The other third bus bar 44B is arranged to sandwich the second bus bar 13 together with the intersection region E. In other words, the second bus bar 13 is arranged between the intersection region E and the third bus bar 44B.

[0233] In the seventeenth embodiment, the positional relationship between the functional electrode 41B and the dielectric layer 92 in a plan view is the same as the positional relationship between the functional electrode 41B and the non-piezoelectric portion in a plan view in the sixth embodiment. Specifically, in the seventeenth embodiment, the first bus bar 12 and portions of the third electrode fingers 17 that overlap with the first bus bar 12 in a plan view are provided on one dielectric layer 92. The third bus bar 44A and portions of the third electrode fingers 17 that are located between the first bus bar 12 and the third bus bar 44A are also provided on the dielectric layer 92.

[0234] The second bus bar 13 and the portions of the third electrode fingers 17 that overlap with the second bus bar 13 in a plan view are provided on the other dielectric layer 92. The third bus bar 44B and the portions of the third electrode fingers 17 that are located between the second bus bar 13 and the third bus bar 44B are also provided on the dielectric layer 92.

[0235] The arrangement of the dielectric layer 92 is not limited to the above. Below, a modified example of the seventeenth embodiment will be described, which differs from the seventeenth embodiment only in the arrangement of the dielectric layer 92. In the modified example of the seventeenth embodiment, as in the seventeenth embodiment, unwanted waves can be effectively suppressed and degradation of the filter characteristics can be effectively suppressed.

[0236] 39 , similarly to the seventeenth embodiment, two dielectric layers 92 are provided on the first main surface 4 a of the piezoelectric layer 104. An edge portion on the crossing region E side of one of the dielectric layers 92 overlaps, in plan view, an edge portion on the third bus bar 44A side in the crossing region E. The edge portion on the crossing region E side of the dielectric layer 92 also extends in the direction orthogonal to the electrode fingers outside the edge portion on the third bus bar 44A side in the crossing region E.

[0237] The dielectric layer 92 is provided with portions of the plurality of first electrode fingers 15 and the plurality of third electrode fingers 17 that are located between the intersection region E and the first bus bar 12. The first bus bar 12 and portions of the plurality of third electrode fingers 17 that overlap with the first bus bar 12 in a plan view are also provided on the dielectric layer 92. In addition, the third bus bar 44A and portions of the plurality of third electrode fingers 17 that are located between the third bus bar 44A and the first bus bar 12 are also provided on the dielectric layer 92.

[0238] An edge portion of the other dielectric layer 92 on the crossing region E side overlaps, in a plan view, an edge portion on the third bus bar 44B side in the crossing region E. The edge portion of the dielectric layer 92 on the crossing region E side also extends in the direction perpendicular to the electrode fingers outside the edge portion on the third bus bar 44B side in the crossing region E.

[0239] The dielectric layer 92 is provided with portions of the second electrode fingers 16 and the third electrode fingers 17 that are located between the intersection region E and the second bus bar 13. The second bus bar 13 and portions of the third electrode fingers 17 that overlap with the second bus bar 13 in a plan view are also provided on the dielectric layer 92. In addition, the third bus bar 44B and portions of the third electrode fingers 17 that are located between the third bus bar 44B and the second bus bar 13 are also provided on the dielectric layer 92.

[0240] In this modification, 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 provided in portions that do not have piezoelectricity, thereby making it possible to further suppress unwanted waves and to further prevent deterioration of the filter characteristics.

[0241] FIG. 40 is a schematic plan view of an elastic wave device according to an eighteenth preferred embodiment of the present invention.

[0242] The eighteenth embodiment differs from the seventh embodiment in that the piezoelectric layer 104 does not have a non-piezoelectric portion and that a dielectric layer 92 is provided directly on the first main surface 4 a of the piezoelectric layer 104. Except for the above differences, the elastic wave device of the eighteenth embodiment has the same configuration as the elastic wave device of the seventh embodiment.

[0243] In the eighteenth embodiment, the functional electrode 51 has one third bus bar 24. The third bus bar 24 is provided so as to sandwich the first bus bar 12 together with the intersection region E. In other words, the first bus bar 12 is provided between the intersection region E and the third bus bar 24.

[0244] In the eighteenth embodiment, the positional relationship between the functional electrode 51 and the dielectric layer 92 in a plan view is the same as the positional relationship between the functional electrode 51 and the non-piezoelectric portion in a plan view in the seventh embodiment. Specifically, in the eighteenth embodiment, the first bus bar 12 and portions of the third electrode fingers 17 that overlap with the first bus bar 12 in a plan view are provided on the dielectric layer 92. The third bus bar 24 and portions of the third electrode fingers 17 that are located between the first bus bar 12 and the third bus bar 24 are also provided on the dielectric layer 92.

[0245] FIG. 41 is a schematic plan view of an elastic wave device according to a nineteenth preferred embodiment of the present invention.

[0246] The nineteenth embodiment differs from the eighth embodiment in that the piezoelectric layer 104 does not have a non-piezoelectric portion and that a dielectric layer 92 is provided directly on the first main surface 4 a of the piezoelectric layer 104. Except for the above differences, the elastic wave device of the nineteenth embodiment has the same configuration as the elastic wave device of the eighth embodiment.

[0247] In the nineteenth embodiment, the third electrode 29 is provided on the second main surface 4b of the piezoelectric layer 104. In plan view, the third bus bar 24 is provided between the intersection region E and the first bus bar 12.

[0248] The dielectric layer 92 is not provided on the second main surface 4b of the piezoelectric layer 104. Therefore, the third electrode 29 is provided directly on the second main surface 4b of the piezoelectric layer 104. The entire third electrode 29 is provided on a portion having piezoelectricity. On the other hand, a portion of the first comb electrode 7 is provided on the dielectric layer 92, which is a portion not having piezoelectricity.

[0249] In the 19th embodiment, the positional relationship between the functional electrode and the dielectric layer 92 in a plan view is the same as the positional relationship between the functional electrode and the non-piezoelectric portion in a plan view in the eighth embodiment. Specifically, in the 19th embodiment, portions of the plurality of first electrode fingers 15 that overlap with the third bus bar 24 in a plan view are provided on the dielectric layer 92. Portions of the plurality of first electrode fingers 15 that are located between the third bus bar 24 and the first bus bar 12 in a plan view, as well as the first bus bar 12, are also provided on the dielectric layer 92.

[0250] In the nineteenth embodiment, in a plan view, the portions of the third bus bar 24 other than those overlapping with the first electrode fingers 15 are adjacent to the first electrode fingers 15 in the direction perpendicular to the electrode fingers. Therefore, in a plan view, the above-mentioned portions of the third bus bar 24 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. It is sufficient that at least one of these electrodes is provided on the dielectric layer 92 or the resin layer. In the nineteenth embodiment, of these electrodes, the first electrode fingers 15 are provided on the dielectric layer 92. This makes it possible to suppress unwanted waves and prevent deterioration of the filter characteristics.

[0251] For example, among electrodes located outside the crossing region E, adjacent to each other in the electrode finger orthogonal direction, and connected to different potentials, only the third bus bar 24 may be provided on the dielectric layer 92 or the resin layer. In this case, it is sufficient that the dielectric layer 92 or the resin layer is provided on the second main surface 4 b of the piezoelectric layer 104. Then, it is sufficient that the third bus bar 24 is indirectly provided on the second main surface 4 b via the dielectric layer 92 or the resin layer. In this way, it is sufficient that the dielectric layer 92 or the resin layer is provided on at least one of the first main surface 4 a and the second main surface 4 b of the piezoelectric layer 104.

[0252] However, it is preferable that the dielectric layer 92 or the resin layer be provided on both the first principal surface 4 a and the second principal surface 4 b of the piezoelectric layer 104. It is also preferable that the portions of the plurality of first electrode fingers 15 that overlap with the third bus bar 24 in a plan view, and the third bus bar 24, are provided on the dielectric layer 92 or the resin layer. This makes it possible to effectively suppress unwanted waves and effectively prevent deterioration of the filter characteristics.

[0253] In the following, an example will be shown in which the third bus bar and the third electrode fingers are provided on different main surfaces of the piezoelectric layer.

[0254] Fig. 42 is a schematic plan view of an elastic wave device according to a twentieth preferred embodiment of the present invention, and Fig. 43 is a schematic cross-sectional view taken along line III-III in Fig. 42.

[0255] As shown in Fig. 42 , the twentieth embodiment differs from the ninth embodiment in that the piezoelectric layer 104 does not have a non-piezoelectric portion and that a dielectric layer 92 is provided directly on the first main surface 4a of the piezoelectric layer 104. The twentieth embodiment also differs from the ninth embodiment in the positional relationship between the functional electrode 61 and the non-piezoelectric portion. As shown in Fig. 43 , the twentieth embodiment also differs from the ninth embodiment in that an insulating layer does not cover the second main surface 4b of the piezoelectric layer 104 and the third bus bar 24. Apart from the above, the elastic wave device of the twentieth embodiment has the same configuration as the elastic wave device of the ninth embodiment.

[0256] As shown in Fig. 42 , a plurality of dielectric layers 92 are provided on the first main surface 4a of the piezoelectric layer 104. The plurality of dielectric layers 92 are arranged in a direction perpendicular to the electrode fingers. As shown in Fig. 43 , a portion of one first electrode finger 15 in the electrode finger extension direction is provided on one dielectric layer 92. Returning to Fig. 42 , the plurality of dielectric layers 92 overlap the plurality of first electrode fingers 15 and the third bus bar 24 in a plan view.

[0257] In plan view, each dielectric layer 92 also extends to a portion that does not overlap with the third bus bar 24. Specifically, in plan view, each dielectric layer 92 is provided over a portion located between the intersection region E and the third bus bar 24, a portion where the third bus bar 24 is located, and a portion located between the third bus bar 24 and the first bus bar 12. In plan view, each dielectric layer 92 also extends to the outside of the first electrode fingers 15 in the direction orthogonal to the electrode fingers.

[0258] In the twentieth embodiment, in a plan view, the portions of the third bus bar 24 other than those overlapping with the first electrode fingers 15 are adjacent to the first electrode fingers 15 in the direction perpendicular to the electrode fingers. Therefore, in a plan view, the above-mentioned portions of the third bus bar 24 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. Of these electrodes, the first electrode fingers 15 are provided on the dielectric layer 92. This makes it possible to suppress unwanted waves and prevent deterioration of the filter characteristics. Note that, instead of the multiple dielectric layers 92, multiple resin layers may be provided.

[0259] Even when the non-piezoelectric portion is the dielectric layer 92 or the resin layer, the third bus bar 24 may be provided on a portion other than the first main surface 4 a and the second main surface 4 b of the piezoelectric layer 104. This example will be described in the twenty-first and twenty-second embodiments.

[0260] Fig. 44 is a schematic plan view showing an electrode configuration on a first main surface of a piezoelectric layer in the twenty-first embodiment, and Fig. 45 is a schematic cross-sectional view taken along line III-III in Fig. 44.

[0261] 44 , the 21st embodiment differs from the 10th embodiment in that the piezoelectric layer 104 does not have a non-piezoelectric portion and that a dielectric layer 92 is provided directly on the first main surface 4 a of the piezoelectric layer 104. The 21st embodiment also differs from the 10th embodiment in the positional relationship between the functional electrode 71 and the non-piezoelectric portion. Except for the above points, the elastic wave device of the 21st embodiment has a similar configuration to the elastic wave device 70 of the 10th embodiment. The elastic wave device of the 21st embodiment has a WLP structure.

[0262] A plurality of dielectric layers 92 are provided on the first main surface 4a of the piezoelectric layer 104. The plurality of dielectric layers 92 are arranged in the direction perpendicular to the electrode fingers. As shown in FIG. 45 , a portion of one first electrode finger 15 in the electrode finger extension direction is provided on one dielectric layer 92. As in the tenth embodiment, the third bus bar 24 of the third electrode 79 is provided on the third main surface 74a of the cover member 74. The third bus bar 24 and the plurality of third electrode fingers 17 are connected by a plurality of connection electrodes 78. Returning to FIG. 44 , the plurality of dielectric layers 92 overlap the plurality of first electrode fingers 15 and the third bus bar 24 in a plan view.

[0263] In plan view, each dielectric layer 92 also extends to a portion that does not overlap with the third bus bar 24. Specifically, in plan view, each dielectric layer 92 is provided over a portion located between the intersection region E and the third bus bar 24, a portion where the third bus bar 24 is located, and a portion located between the third bus bar 24 and the first bus bar 12. In plan view, each dielectric layer 92 also extends to the outside of the first electrode fingers 15 in the direction orthogonal to the electrode fingers.

[0264] In the twenty-first embodiment, the portions of the first electrode finger 15 and the third electrode finger 17 that overlap with the third bus bar 24 in a plan view are adjacent to each other in the direction perpendicular to the electrode fingers. Therefore, the above-mentioned portions of the first electrode finger 15 and the third electrode finger 17 are located outside the intersection region E, adjacent to each other in the direction perpendicular to the electrode fingers, and are electrodes connected to different potentials. Of these electrodes, the first electrode finger 15 is provided on the dielectric layer 92. This makes it possible to suppress unwanted waves and prevent deterioration of the filter characteristics.

[0265] However, it is sufficient that at least one of the electrodes located outside the intersection region E, adjacent in the direction perpendicular to the electrode fingers, and connected to different potentials is provided on the dielectric layer 92 or the resin layer.

[0266] 46 , for example, a portion of one third electrode finger 17 that overlaps with the third bus bar 24 in plan view is provided on one dielectric layer 92. That is, among the electrodes that are located outside the intersection region E, adjacent in the direction perpendicular to the electrode fingers, and connected to different potentials, the third electrode finger 17 is provided on the dielectric layer 92 as a non-piezoelectric portion. In this case as well, it is possible to suppress unwanted waves and prevent deterioration of the filter characteristics.

[0267] In this modification, a portion of the third electrode finger 17 is covered with a connection electrode 78. The connection electrode 78 is provided over the third electrode finger 17 and the dielectric layer 92. Note that the connection electrode 78 may be provided only on the third electrode finger 17.

[0268] The portions of the first electrode fingers 15 and the third electrode fingers 17 that overlap with the third bus bar 24 in a plan view may be provided on the dielectric layer 92 or the resin layer. In this case, unwanted waves can be effectively suppressed, and deterioration of the filter characteristics can be effectively prevented.

[0269] Fig. 47 is a schematic plan view showing an electrode configuration on a first main surface of a piezoelectric layer in the twenty-second embodiment, and Fig. 48 is a schematic cross-sectional view taken along line III-III in Fig. 47.

[0270] 47 , the 22nd embodiment differs from the 11th embodiment in that the piezoelectric layer 104 does not have a non-piezoelectric portion and that a dielectric layer 92 is provided directly on the first main surface 4 a of the piezoelectric layer 104. The 22nd embodiment also differs from the 11th embodiment in the positional relationship between the functional electrode 71 and the non-piezoelectric portion. Except for the above points, the elastic wave device of the 22nd embodiment has a similar configuration to the elastic wave device 80 of the 11th embodiment. The elastic wave device of the 22nd embodiment has a CSP structure.

[0271] A plurality of dielectric layers 92 are provided on the first main surface 4a of the piezoelectric layer 104. The plurality of dielectric layers 92 are arranged in the direction perpendicular to the electrode fingers. As shown in FIG. 48 , a portion of one first electrode finger 15 in the electrode finger extension direction is provided on one dielectric layer 92. As in the eleventh embodiment, the third bus bar 24 of the third electrode 79 is provided on the fifth main surface 85a of the mounting substrate 85. The third bus bar 24 and the plurality of third electrode fingers 17 are connected by a plurality of connection electrodes 78. Returning to FIG. 47 , the plurality of dielectric layers 92 overlap the plurality of first electrode fingers 15 and the third bus bar 24 in a plan view.

[0272] In plan view, each dielectric layer 92 also extends to a portion that does not overlap with the third bus bar 24. Specifically, in plan view, each dielectric layer 92 is provided over a portion located between the intersection region E and the third bus bar 24, a portion where the third bus bar 24 is located, and a portion located between the third bus bar 24 and the first bus bar 12. In plan view, each dielectric layer 92 also extends to the outside of the first electrode fingers 15 in the direction orthogonal to the electrode fingers.

[0273] In the twenty-second embodiment, the portions of the first electrode finger 15 and the third electrode finger 17 that overlap with the third bus bar 24 in a plan view are adjacent to each other in the direction perpendicular to the electrode fingers. Therefore, the above-mentioned portions of the first electrode finger 15 and the third electrode finger 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. Of these electrodes, the first electrode finger 15 is provided on the dielectric layer 92. This makes it possible to suppress unwanted waves and prevent deterioration of the filter characteristics.

[0274] However, it is sufficient that at least one of the electrodes located outside the intersection region E, adjacent in the direction perpendicular to the electrode fingers, and connected to different potentials is provided on the dielectric layer 92 or the resin layer.

[0275] 49 , for example, a portion of one third electrode finger 17 that overlaps with the third bus bar 24 in plan view is provided on one dielectric layer 92. That is, of the electrodes that are located outside the intersection region E, adjacent in the direction perpendicular to the electrode fingers, and connected to different potentials, the third electrode finger 17 is provided on the dielectric layer 92 as a non-piezoelectric portion. In this case as well, it is possible to suppress unwanted waves and prevent deterioration of the filter characteristics.

[0276] In this modification, a portion of the third electrode finger 17 is covered with a connection electrode 78. The connection electrode 78 is provided over the third electrode finger 17 and the dielectric layer 92. Note that the connection electrode 78 may be provided only on the third electrode finger 17.

[0277] The portions of the first electrode fingers 15 and the third electrode fingers 17 that overlap with the third bus bar 24 in a plan view may be provided on the dielectric layer 92 or the resin layer. In this case, unwanted waves can be effectively suppressed, and deterioration of the filter characteristics can be effectively prevented.

[0278] In the first to twenty-second 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 twenty-third embodiment.

[0279] FIG. 50 is a schematic front cross-sectional view of an elastic wave device according to a twenty-third preferred embodiment.

[0280] 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.

[0281] 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.

[0282] 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 of the acoustic reflecting film 118 are low acoustic impedance layer 115a, low acoustic impedance layer 115b, and low acoustic impedance layer 115c.

[0283] 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 of 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 of the acoustic reflecting film 118 that is located closest to the piezoelectric layer 4.

[0284] 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.

[0285] 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.

[0286] In this embodiment, unwanted waves can also be effectively suppressed, and deterioration of the filter characteristics can be effectively suppressed. In addition, the provision of the acoustic reflection film 118 can effectively confine the energy of the elastic waves to the piezoelectric layer 4 side.

[0287] In this embodiment, the portion that does not have piezoelectricity is a non-piezoelectric portion in the piezoelectric layer 4. However, the portion that does not have piezoelectricity may be a dielectric layer or a resin layer. The configuration in this embodiment in which the acoustic reflection portion is the acoustic reflection film 118 can be applied to configurations of the present invention other than this embodiment.

[0288] A preferred configuration of the present invention will be described below using a reference example shown in Fig. 51. The reference example differs from the first embodiment in that an IDT electrode 101 is provided instead of the functional electrode 1 shown in Fig. 2. Apart from this, the elastic wave device of the reference example has the same configuration as the first embodiment.

[0289] The IDT electrode 101 differs from the functional electrode in that it does not have a third electrode. Therefore, the IDT electrode 101 has a first interdigital electrode 7 and a second interdigital 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. The portion of the piezoelectric layer 4 located in the intersection region E has piezoelectricity.

[0290] The elastic wave device of the reference example also utilizes thickness-shear mode bulk waves, as in the first to twenty-second 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 twenty-second embodiments. Therefore, the following configuration shown in the reference example is also preferred for the first to twenty-second embodiments.

[0291] 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.

[0292] FIG. 52 is a graph showing the relationship between d / p and the fractional bandwidth of an elastic wave device according to a reference example.

[0293] As is clear from Figure 52, 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.

[0294] 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.

[0295] 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. 51 , 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.

[0296] 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. The width of the electrode finger is the dimension of the electrode finger along the direction perpendicular to the electrode fingers.

[0297] Fig. 53 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. 53 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. 53 is specifically the value obtained by normalizing the amount of phase rotation of the spurious impedance by 180°. The results shown in Fig. 53 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.

[0298] In the region surrounded by ellipse B in Figure 53, 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.

[0299] 54 is a diagram showing the relationship between d / p, metallization ratio MR, and fractional bandwidth, in which the results of calculating fractional bandwidth for different d / p and metallization ratio MR are shown.

[0300] In FIG. 54, 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.

[0301] On the other hand, the dashed-dotted line G1 in Figure 54 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. If 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 allows for more reliably suppressing spurious emissions.

[0302] 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°.

[0303] FIG. 55 shows the LiNbO ３ 55 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. 55 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).

[0304] (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)

[0305] 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 4 is made of lithium tantalate.

[0306] Examples of embodiments of the acoustic wave device according to the present invention will be described below.

[0307] <1> 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, when viewed in plan. 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 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 first electrode finger and the second electrode finger overlap in the electrode finger orthogonal direction. an elastic wave device in which the overlapping region is an intersection region, one third bus bar 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, the third bus bar and the first electrode fingers are electrically insulated, and at least one of the portions of the first electrode fingers that overlap with the third bus bar in a planar view and the third bus bar is provided in a portion that does not have piezoelectricity.

[0308] <2> The elastic wave device according to <1>, 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 plan view; the third bus bar overlaps with the first electrode fingers in a plan view; 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 in a plan view; the third bus bar overlaps with the second electrode fingers in a plan view; the third bus bar is electrically insulated from the second electrode fingers; and at least one of the third bus bar and portions of the second electrode fingers that overlap with the third bus bar in a plan view and the third bus bar is provided in the non-piezoelectric portion.

[0309] <3> The elastic wave device according to <1>, 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 plan view; the third bus bar overlaps with the first electrode fingers in a plan view; the third bus bar is electrically insulated from the first electrode fingers; the second bus bar is located between the intersection region and the other third bus bar in a plan view; the second bus bar overlaps with the third electrode fingers in a plan view; the second bus bar is electrically insulated from the third electrode fingers; and at least one of the second bus bar and portions of the third electrode fingers that overlap with the second bus bar in a plan view and portions of the second bus bar are provided in the non-piezoelectric portion.

[0310] <4> An elastic wave device according to any one of <1> to <3>, wherein the third bus bar overlapping the plurality of first electrode fingers in a planar view, portions of the plurality of first electrode fingers located between the first bus bars, and the first bus bar are provided in a portion that does not have piezoelectricity.

[0311] <5> An elastic wave device described in any one of <1> to <4>, wherein the third bus bar that overlaps with the plurality of first electrode fingers in a planar view and the portions of the plurality of first electrode fingers that are located between the intersection regions are provided in the portion that does not have piezoelectricity.

[0312] <6> The elastic wave device according to any one of <1> to <5>, 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 with each other via the insulator layer, the third bus bar, the insulator layer, and the first electrode fingers are stacked in this order, and the third bus bar is provided in the portion that does not have piezoelectricity.

[0313] <7> The elastic wave device according to any one of <1> to <5>, wherein the 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 first electrode fingers and some of the third bus bar intersect with each other via the insulator layer, the first electrode fingers, the insulator layer, and the third bus bar are stacked in this order, and portions of the first electrode fingers that overlap with the third bus bar in a planar view are provided in a portion that does not have piezoelectricity.

[0314] <8> 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 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 first 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, the first electrode finger and the second electrode finger overlap in the electrode finger orthogonal direction. an area where the first and second bus bars meet is an intersection area, the first bus bar is located between the intersection area and one of the third bus bars in a planar view, 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, and at least one of the first bus bar and the portions of the third electrode fingers that overlap with the first bus bar in a planar view is provided in a portion that does not have piezoelectricity.

[0315] <9> The elastic wave device according to <8>, further comprising: two third bus bars; in a plan 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 plan view; the first bus bar and the third electrode fingers are electrically insulated from each other; in a plan 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 plan view; the second bus bar and the third electrode fingers are electrically insulated from each other; and at least one of the second bus bar and portions of the third electrode fingers that overlap the second bus bar in a plan view and portions of the second bus bar are provided in the non-piezoelectric portion.

[0316] <10> The elastic wave device according to <8> or <9>, wherein the third bus bar is arranged to sandwich the first bus bar together with the intersection region, and the third bus bar and the portions of the plurality of third electrode fingers located between the first bus bars are provided in the portion that does not have piezoelectricity.

[0317] <11> An elastic wave device described in any one of <8> to <10>, wherein the portion of the plurality of third electrode fingers located between the first bus bar and the intersection region is provided in the portion that does not have the piezoelectricity.

[0318] <12> The elastic wave device according to any one of <1> to <5> or <8> 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.

[0319] <13> 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 of which is 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 of which is connected to the second bus bar and interdigitated with the plurality of first electrode fingers; 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; and a plurality of connection electrodes provided on the second main surface, which connect the plurality of third electrode fingers to the plurality of third electrode fingers. and a third electrode having at least one third bus bar electrically connected to the third electrode fingers of the first and second comb electrodes and connected to a potential different from that of the first and second comb electrodes, wherein one of the first and second comb electrodes is connected to an input potential and the other of the first and second comb electrodes is connected to an output potential, the first electrode fingers, the second electrode fingers, and the third electrode fingers are arranged in an order such that, starting from the first electrode finger, one period consists of the first electrode finger, the third electrode finger, the second electrode finger, and the third electrode finger, and one third bus bar overlaps with the first electrode fingers in a planar view, and at least one of the portions of the first electrode fingers that overlap with the third bus bar in a planar view and the third bus bar is provided in a non-piezoelectric portion.

[0320] <14> 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 plurality of connection electrodes 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, the plurality of connection electrodes being connected to the plurality of third electrode fingers, and a third electrode 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 first comb electrode and the second comb electrode is connected to an output potential, the first electrode fingers, the second electrode fingers, and the third electrode fingers 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, one third bus bar overlaps with the plurality of first electrode fingers in a plan view, and a portion of at least one of the plurality of first electrode fingers and the plurality of third electrode fingers that overlaps with the third bus bar in a plan view is provided in a portion that does not have piezoelectricity.

[0321] <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.

[0322] <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.

[0323] <17> An elastic wave device according to any one of <1> to <16>, wherein a part of the piezoelectric layer is a part that does not have the piezoelectricity, and a part that is provided in the part that does not have the piezoelectricity is provided directly on the piezoelectric layer.

[0324] <18> An elastic wave device according to any one of <1> to <16>, wherein the non-piezoelectric portion is a dielectric layer or a resin layer, and the portion provided in the non-piezoelectric portion is indirectly provided on the piezoelectric layer via the dielectric layer or the resin layer.

[0325] <19> The acoustic wave device according to any one of <1> to <18>, wherein the first interdigital transducer is connected to an input potential and the second interdigital transducer is connected to an output potential.

[0326] <20> The acoustic wave device according to any one of <1> to <18>, wherein the first interdigital transducer is connected to an output potential and the second interdigital transducer is connected to an input potential.

[0327] <21> The elastic wave device according to any one of <1> to <20>, 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 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 defined as p, and when the thickness of the piezoelectric layer is defined as d, d / p is 0.5 or less.

[0328] <22> The acoustic wave device according to <21>, wherein d / p is 0.24 or less.

[0329] <23> An elastic wave device described in <21> or <22>, 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.

[0330] <24> The elastic wave device described in <21> or <22>, 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.

[0331] <25> The elastic wave device according to any one of <21> to <24>, wherein, 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 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.

[0332] <26> The elastic wave device according to any one of <1> to <25>, 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)

[0333] REFERENCE SIGNS LIST 1...functional electrode 2...piezoelectric substrate 3...support member 4...piezoelectric layer 4A-4I...piezoelectric layer 4a, 4b...first and second principal surfaces 4c...non-piezoelectric portion 5...insulating layer 6...support substrate 7, 8...first and second interdigital electrodes 9...third electrode 10...acoustic wave device 10a...cavity portion 12-14...first to third bus bars 14a...common electrode portion 14b...bar portion 15-17...first to third electrode fingers 19...insulating layer 21...functional electrode 24...third bus bar 29...third electrode 31, 41, 41A, 41B...functional electrodes 44A, 44B...third bus bar 49...third electrode 51...functional electrode 60a...cavity portion 61...functional electrode 65...insulating layer 68...Connection electrode 69...Third electrode 70...Acoustic wave device 71...Functional electrode 72...First support 72a...Opening 73...Second support 74...Cover member 74A...Cover member main body 74B...Inorganic oxide layer 74a, 74b...Third and fourth principal surfaces 75...Through electrode 76...External terminal 77...Bump 78...Connection electrode 79...Third electrode 80...Acoustic wave device 84...Sealing resin 85...Mounting substrate 85a, 85b...Fifth and sixth principal surfaces 86...External terminal 87...Bump 88...Electrode pad 92...Dielectric layer 101...IDT electrode 104...Piezoelectric layer 113...Support member 115a to 115c...Low acoustic impedance layers 116a, 116b...High acoustic impedance layers 118...Acoustic reflection film C...Excitation region E...Cross region F...Element electrode forming part

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 in which at least one of portions of the plurality of first electrode fingers that overlap with the third bus bar in a plan view and the third bus bar is provided in a portion that does not have piezoelectricity; 2. The elastic wave device according to claim 1, comprising two third bus bars, wherein in a planar view, one of the third bus bars is located between the intersection region and the first bus bar, overlapping 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 is located between the intersection region and the second bus bar, overlapping the plurality of second electrode fingers in a planar view and electrically insulated from the plurality of second electrode fingers, and at least one of the portions of the plurality of second electrode fingers that overlap with the third bus bar in a planar view and the third bus bar is provided in the portion that does not have piezoelectricity.

3. The elastic wave device according to claim 1, comprising two third bus bars, wherein in a planar view, one of the third bus bars 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 planar view, and the third bus bar and the plurality of first electrode fingers are electrically insulated from each other, and in a planar view, the second bus bar is located between the intersection region and the other of the third bus bars, and 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 at least one of the portions of the plurality of third electrode fingers that overlap with the second bus bar in a planar view and the second bus bar is provided in the portion that does not have piezoelectricity.

4. An elastic wave device according to any one of claims 1 to 3, wherein the third bus bar overlapping the plurality of first electrode fingers in a planar view, the portions of the plurality of first electrode fingers located between the first bus bars, and the first bus bar are provided in the portion that does not have piezoelectricity.

5. An elastic wave device according to any one of claims 1 to 4, wherein the third bus bar overlapping the plurality of first electrode fingers in a planar view and the portions of the plurality of first electrode fingers located between the intersection regions are provided in the non-piezoelectric portion.

6. The elastic wave device according to any one of claims 1 to 5, wherein the plurality of third electrode fingers and the third bus bar are provided on the first main surface of the piezoelectric layer, 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 via the insulator layer, the third bus bar, the insulator layer, and the first electrode fingers are layered in this order, and the third bus bar is provided in the portion not having piezoelectricity.

7. The elastic wave device according to any one of claims 1 to 5, 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 via the insulator layer, the first electrode fingers, the insulator layer, and the third bus bar are layered in this order, and portions of the plurality of first electrode fingers that overlap with the third bus bar in a planar view are provided in a portion that does not have piezoelectricity.

8. 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 in which at least one of portions of the third electrode fingers that overlap with the first bus bar in a plan view and the first bus bar is provided in a portion that does not have piezoelectricity.

9. The elastic wave device according to claim 8, 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 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 at least one of the portions of the plurality of third electrode fingers that overlap with the second bus bar in a planar view and the second bus bar is provided in the portion that does not have piezoelectricity.

10. The elastic wave device according to claim 8 or 9, wherein the third bus bar, which is arranged to sandwich the first bus bar together with the intersection region, and the portions of the plurality of third electrode fingers located between the first bus bars, and the third bus bar are provided in the non-piezoelectric portion.

11. The elastic wave device according to any one of claims 8 to 10, wherein the portions of the plurality of third electrode fingers located between the first bus bar and the intersection region are provided in the non-piezoelectric portion.

12. The elastic wave device according to any one of claims 1 to 5 or 8 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 elastic wave device in which the first electrode fingers, the second electrode fingers, and the third electrode fingers are arranged in an order such that, starting from the first electrode finger, one period consists of the first electrode finger, the third electrode finger, the second electrode finger, and the third electrode finger; one third bus bar overlaps with the plurality of first electrode fingers in a planar view; and at least one of the portions of the plurality of first electrode fingers that overlap with the third bus bar in a planar view and the third bus bar is provided in a portion that does not have piezoelectricity.

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 elastic wave device, wherein one third bus bar overlaps with the plurality of first electrode fingers in a planar view; and a portion of at least one of the plurality of first electrode fingers and the plurality of third electrode fingers that overlaps with the third bus bar in a planar view is provided in a portion that does not have piezoelectricity.

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. An elastic wave device according to any one of claims 1 to 16, wherein a portion of the piezoelectric layer is a portion that does not have piezoelectricity, and the portion that is provided in the portion that does not have piezoelectricity is provided directly on the piezoelectric layer.

18. The elastic wave device according to any one of claims 1 to 16, wherein the non-piezoelectric portion is a dielectric layer or a resin layer, and the portion provided in the non-piezoelectric portion is indirectly provided on the piezoelectric layer via the dielectric layer or the resin layer.

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

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

21. The elastic wave device according to any one of claims 1 to 20, 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.

22. The acoustic wave device according to claim 21, wherein d / p is 0.24 or less.

23. An elastic wave device according to claim 21 or 22, 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.

24. An elastic wave device according to claim 21 or 22, 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.

25. The elastic wave device according to any one of claims 21 to 24, 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.

26. The acoustic wave device according to any one of claims 1 to 25, 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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