Elastic wave device

Abstract

Provided is an elastic wave device in which a ladder-type filter device having an elastic wave resonator that has a small capacitance and uses a thickness shear mode bulk wave can be reduced in size, and in which deterioration of filter characteristics can be suppressed. The elastic wave device includes a plurality of acoustic elements. At least one of the plurality of acoustic elements has, between the first comb electrode and the second comb electrode, a third electrode connected to a potential different from that of the first comb electrode and that of the second comb electrode. In the support member, an acoustic reflection section (cavity section) is formed at a position overlapping the functional electrodes of the plurality of acoustic elements.

Description

Technical Field

[0001] The present invention relates to an elastic wave device having a plurality of acoustic elements. Background Art

[0002] In the past, elastic wave devices were widely used in filters of portable phones and the like. In recent years, an elastic wave device using a thickness shear mode body wave has been proposed, as described in the following patent document 1. In this elastic wave device, a piezoelectric layer is provided on a support. A pair of electrodes is provided on the piezoelectric layer. The paired electrodes are opposed to each other on the piezoelectric layer and are connected to different potentials. By applying an alternating voltage between the electrodes, a thickness shear mode body wave is excited.

[0003] Prior Art Literature

[0004] Patent Literature

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

[0006] Problem that the invention aims to solve

[0007] The so-called elastic wave device is, for example, an acoustic element such as an elastic wave resonator. The elastic wave resonator is used, for example, in a ladder filter. In order to obtain good characteristics in the ladder filter, it is necessary to increase the electrostatic capacitance ratio between the plurality of elastic wave resonators. In this case, it is necessary to increase the electrostatic capacitance of a portion of the elastic wave resonators in the ladder filter.

[0008] In order to increase the capacitance of the elastic wave resonator, for example, the elastic wave resonator needs to be enlarged. Therefore, when the elastic wave resonator is used in a ladder filter, the ladder filter tends to be enlarged. In particular, a ladder filter having an elastic wave resonator with a small capacitance and utilizing a bulk wave in a thickness shear mode tends to be enlarged.

[0009] The inventors of the present invention have found that, when an elastic wave resonator is used in a filter device, a suitable filter waveform can be obtained without increasing the size thereof by setting the structure of the elastic wave resonator to the following structure: the structure is a structure in which an electrode connected to a potential different from the input potential and the output potential, such as a reference potential, is arranged between an electrode connected to an input potential and an electrode connected to an output potential.

[0010] In addition, the inventors of the present invention have found that when the elastic wave resonator having the above-mentioned structure is used together with other acoustic elements in a filter device, the filter characteristics may be degraded.

[0011] An object of the present invention is to provide an elastic wave device that can promote miniaturization of a filter device and suppress degradation of filter characteristics.

[0012] Technical solutions to solve problems

[0013] The elastic wave device of the present invention comprises a plurality of acoustic elements, wherein the plurality of acoustic elements share a supporting member and a piezoelectric film, wherein the piezoelectric film is arranged on the supporting member and includes a piezoelectric layer composed of a piezoelectric body, wherein the plurality of acoustic elements include a first acoustic element and a second acoustic element electrically connected to the first acoustic element, wherein the first acoustic element is an acoustic coupling filter, wherein the first acoustic element includes: a first comb-shaped electrode, which is arranged on the piezoelectric layer and connected to an input potential, and has a first bus bar and a plurality of first electrode fingers, wherein one ends of the plurality of first electrode fingers are respectively connected to the first bus bar; a second comb-shaped electrode, which is arranged on the piezoelectric layer and connected to an output potential, and has a second bus bar and a plurality of second electrode fingers, wherein one ends of the plurality of second electrode fingers are respectively connected to the second bus bar and are interlaced with the plurality of first electrode fingers; and a third electrode, which has a plurality of third electrode fingers and connects adjacent third electrode fingers. The connecting electrodes are connected to each other and are connected to a potential different from that of the first comb-shaped electrode and the second comb-shaped electrode. The plurality of third electrode fingers are respectively arranged on the piezoelectric layer so that they are arranged with the first electrode finger and the second electrode finger in the direction in which the first electrode finger and the second electrode finger are arranged when viewed from above. When starting from the first electrode finger, the first electrode finger, the second electrode finger and the third electrode finger are arranged in an order that takes the first electrode finger, the third electrode finger, the second electrode finger and the third electrode finger as a period. The second acoustic element has a functional electrode arranged on the piezoelectric layer. When viewed from above, an acoustic reflection portion is formed in the supporting 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 the first acoustic element and the functional electrode of the second acoustic element.

[0014] Effects of the Invention

[0015] According to the present invention, it is possible to provide an elastic wave device that can promote miniaturization of a filter device and suppress degradation of filter characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic plan view of the elastic wave device according to the first embodiment of the present invention.

[0017] Figure 2 It is a schematic front cross-sectional view of a first acoustic element and a second acoustic element in the first embodiment of the present invention.

[0018] Figure 3 It is a schematic plan view of the first acoustic element in the first embodiment of the present invention.

[0019] Figure 4 This is a schematic front cross-sectional view showing the vicinity of first to third electrode fingers in the first embodiment of the present invention.

[0020] Figure 5 It is a schematic plan view of the second acoustic element in the first embodiment of the present invention.

[0021] Figure 6 It is a diagram showing the passage characteristics of the first embodiment of the present invention and a comparative example.

[0022] Figure 7 This is a diagram showing a map of the relative bandwidth with respect to the Euler angle (0°, θ, ψ) of LiNbO 3 when d / p is made as close to 0 as possible.

[0023] Figure 8 It is a schematic plan view of a first acoustic element in a modified example of the first embodiment of the present invention.

[0024] Fig. 9 It is a schematic plan view of a first acoustic element in a second embodiment of the present invention.

[0025] Fig.10 This is a schematic front cross-sectional view showing the vicinity of first to third electrode fingers in the second embodiment of the present invention.

[0026] Fig.11 It is a schematic front cross-sectional view of an elastic wave device according to a second embodiment of the present invention.

[0027] Fig.12 It is a schematic plan view of an elastic wave device according to a third embodiment of the present invention.

[0028] Fig.13 It is a schematic front cross-sectional view of an elastic wave device according to a fourth embodiment of the present invention.

[0029] Fig.14 It is a schematic plan view of an elastic wave device according to a fifth embodiment of the present invention.

[0030] Fig.15 It is a schematic front cross-sectional view of an elastic wave device according to a first modified example of the fifth embodiment of the present invention.

[0031] Fig.16 It is a schematic front cross-sectional view of an elastic wave device according to a second modified example of the fifth embodiment of the present invention.

[0032] Fig.17 It is a schematic front cross-sectional view of an elastic wave device according to a third modified example of the fifth embodiment of the present invention.

[0033] Fig.18 It is a schematic front cross-sectional view of an elastic wave device according to a fourth modified example of the fifth embodiment of the present invention.

[0034] Fig.19 It is a schematic plan view of an elastic wave device according to a fifth modification of the fifth embodiment of the present invention.

[0035] Fig. 20 (a) is a schematic perspective view showing the appearance of an elastic wave device using a thickness shear mode bulk wave, Fig. 20 (b) is a top view showing the electrode structure on the piezoelectric layer.

[0036] Fig.21 yes Fig. 20 (a) is a cross-sectional view of the portion along line AA.

[0037] Fig. 22 (a) is a schematic front cross-sectional view for explaining Lamb waves propagating through a piezoelectric film of an elastic wave device. Fig. 22 (b) is a schematic front cross-sectional view for explaining a thickness shear mode bulk wave propagating through a piezoelectric film in an elastic wave device.

[0038] Fig.23 It is a diagram showing the amplitude direction of the body wave in the thickness shear mode.

[0039] Fig.24 FIG. 1 is a diagram showing the resonance characteristics of an elastic wave device using bulk waves in a thickness shear mode.

[0040] Fig.25 1 is a diagram showing the relationship between d / p and the relative bandwidth of the resonator when the distance between the centers of adjacent electrodes is defined as p and the thickness of the piezoelectric layer is defined as d.

[0041] Fig.26 This is a top view of an elastic wave device using bulk waves in a thickness shear mode.

[0042] Fig. 27 FIG. 2 is a diagram showing the resonance characteristics of an elastic wave device according to a reference example in which spurious emission occurs.

[0043] Fig.28 This is a diagram showing the relationship between the relative bandwidth and the phase rotation amount of the impedance of the spurious signal normalized by 180 degrees, which is the magnitude of the spurious signal.

[0044] Fig.29 It is a graph showing the relationship between d / 2p and the metallization ratio MR.

[0045] Fig.30 This is a diagram showing a map of the relative bandwidth with respect to the Euler angle (0°, θ, ψ) of LiNbO 3 when d / p is made as close to 0 as possible.

[0046] Fig.31 It is a front cross-sectional view of an elastic wave device having an acoustic multilayer membrane.

[0047] Fig.32 This is a partially cutaway perspective view for explaining an elastic wave device using Lamb waves. DETAILED DESCRIPTION

[0048] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings to clarify the present invention.

[0049] In addition, it should be noted that each embodiment described in this specification is merely illustrative and that some structures may be replaced or combined between different embodiments.

[0050] Figure 1 It is a schematic plan view of the elastic wave device according to the first embodiment of the present invention.

[0051] The elastic wave device 10 is used as a part of a filter device. The elastic wave device 10 has a plurality of acoustic elements. However, the elastic wave device according to the present invention may also be a filter device. The structure of the elastic wave device 10 will be described below.

[0052] The elastic wave device 10 has a first acoustic element 10A and a second acoustic element 10B. In the present embodiment, the first acoustic element 10A and the second acoustic element 10B are both elastic wave resonators. Specifically, the first acoustic element 10A is an acoustic coupling filter. The first acoustic element 10A has a functional electrode 11. The second acoustic element 10B is an elastic wave resonator that is not an acoustic coupling filter. The second acoustic element 10B has an IDT (Interdigital Transducer) electrode 31 as a functional electrode.

[0053] The number of first acoustic elements 10A and second acoustic elements 10B in elastic wave device 10 is not limited to the above number. The elastic wave device of the present invention only needs to include at least one first acoustic element and at least one second acoustic element. The first acoustic element and the second acoustic element are electrically connected.

[0054] In elastic wave device 10, first acoustic element 10A and second acoustic element 10B are connected in parallel to each other. In this embodiment, second acoustic element 10B is used as a wave trap element. Alternatively, first acoustic element 10A and second acoustic element 10B may be connected in series to each other.

[0055] like Figure 1 As shown, the elastic wave device 10 has a piezoelectric substrate 12. The piezoelectric substrate 12 is a substrate having piezoelectricity. The piezoelectric substrate 12 has a piezoelectric layer 14 as a piezoelectric film. The piezoelectric layer 14 is a layer composed of a piezoelectric body. On the other hand, in this specification, the so-called piezoelectric film is a film having piezoelectricity, and does not necessarily refer to a film composed of a piezoelectric body. However, in the present embodiment, the piezoelectric film is a single-layer piezoelectric layer 14, which is a film composed of a piezoelectric body. In addition, in the present invention, the piezoelectric film may also be a laminated film including the piezoelectric layer 14. In the present embodiment, the piezoelectric substrate 12 is a laminated body including the piezoelectric layer 14. The first acoustic element 10A and the second acoustic element 10B share the piezoelectric substrate 12. Moreover, the first acoustic element 10A and the second acoustic element 10B share the piezoelectric layer 14 as a piezoelectric film.

[0056] The cavity 10 a is provided in the piezoelectric substrate 12 . In the present embodiment, when viewed along the stacking direction of the piezoelectric substrate 12 , at least a portion of the functional electrode 11 and at least a portion of the IDT electrode 31 overlap with the same cavity 10 a.

[0057] Hereinafter, the structure of the first acoustic element 10A as an acoustic coupling filter will be described in detail.

[0058] Figure 2 It is a schematic front cross-sectional view of the first acoustic element and the second acoustic element in the first embodiment. Figure 3 : is a schematic top view of the first acoustic element in the first embodiment. Figure 2 It is shown that the Figure 3 A schematic cross-sectional view of a portion of the cross section taken along line II in FIG. Figure 2 In FIG. 1 , each electrode is shown with hatching. Figure 2 Similarly, in other schematic top views, electrodes may be hatched. Figure 3 In the figure, wiring and the like connected to the first acoustic element 10A and the second acoustic element 10B are omitted.

[0059] As mentioned above, Figure 2 The first acoustic element 10A shown has a piezoelectric substrate 12 and a functional electrode 11. The piezoelectric substrate 12 has a supporting member 13 and a piezoelectric layer 14 as a piezoelectric film. In this embodiment, the supporting member 13 includes a supporting substrate 16 and an insulating layer 15. The insulating layer 15 is provided on the supporting substrate 16. The piezoelectric layer 14 is provided on the insulating layer 15. However, the supporting member 13 may also be composed of only the supporting substrate 16.

[0060] The piezoelectric layer 14 has a first principal surface 14a and a second principal surface 14b. The first principal surface 14a and the second principal surface 14b are opposite to each other. When the piezoelectric layer 14 is viewed from the direction in which the first principal surface 14a and the second principal surface 14b are opposite to each other, the piezoelectric layer 14 and the supporting member 13 overlap. Of the first principal surface 14a and the second principal surface 14b, the second principal surface 14b is located on the supporting member 13 side. The functional electrode 11 is provided on the first principal surface 14a of the piezoelectric layer 14.

[0061] As the material of the support substrate 16, for example, semiconductors such as silicon, ceramics such as aluminum oxide, etc. can be used. As the material of the insulating layer 15, appropriate dielectrics such as silicon oxide or tantalum oxide can be used. The piezoelectric layer 14 is, for example, a lithium niobate layer such as a LiNbO3 layer or a lithium tantalate layer such as a LiTaO3 layer.

[0062] A recess is provided in the insulating layer 15. A piezoelectric layer 14 as a piezoelectric film is provided on the insulating layer 15 so as to seal the recess. Thus, a hollow portion is formed. The hollow portion is a cavity 10a. In the present embodiment, the supporting member 13 and the piezoelectric film are configured so that a part of the supporting member 13 and a part of the piezoelectric film are opposed to each other with the cavity 10a sandwiched therebetween. However, the recess in the supporting member 13 may also be provided so as to span the insulating layer 15 and the supporting substrate 16. Alternatively, it may be that only the recess provided in the supporting substrate 16 is sealed by the insulating layer 15. The recess may also be provided in the piezoelectric layer 14, for example. In addition, the cavity 10a may also be a through hole provided in the supporting member 13.

[0063] The cavity 10a is the acoustic reflection portion in the present invention. Through the acoustic reflection portion, the energy of the elastic waves of the first acoustic element 10A and the second acoustic element 10B can be effectively confined on the piezoelectric layer 14 side. In a plan view, the acoustic reflection portion is provided at a position overlapping with at least a portion of the functional electrode 11 in the support member 13. In addition, as described above, the cavity 10a as the acoustic reflection portion overlaps with at least a portion of the IDT electrode 31 of the second acoustic element 10B in a plan view.

[0064] In this specification, the term "top view" refers to a view from the Figure 2 The upper direction in the diagram is observed along the stacking direction of the support member 13 and the piezoelectric film. Figure 2 In the embodiment of the present invention, for example, the piezoelectric layer 14 side of the support substrate 16 side and the piezoelectric layer 14 side is the upper side. Furthermore, in this specification, looking down is synonymous with observing from the main surface facing direction. The so-called main surface facing direction is the direction in which the first main surface 14a and the second main surface 14b of the piezoelectric layer 14 are facing each other. More specifically, the main surface facing direction is, for example, the normal direction of the first main surface 14a.

[0065] like Figure 3As shown, the functional electrode 11 has a pair of comb-shaped electrodes and a third electrode 19. Specifically, the pair of comb-shaped electrodes is a first comb-shaped electrode 17 and a second comb-shaped electrode 18. The first comb-shaped electrode 17 is connected to an input potential. The second comb-shaped electrode 18 is connected to an output potential. In the present embodiment, the third electrode 19 is connected to a reference potential. In the present embodiment, the third electrode 19 is a reference potential electrode. In addition, the third electrode 19 does not necessarily have to be connected to a reference potential. The third electrode 19 only needs to be connected to a potential different from that of the first comb-shaped electrode 17 and the second comb-shaped electrode 18. However, it is preferred that the third electrode 19 is connected to a reference potential.

[0066] The first comb-shaped electrode 17 and the second comb-shaped electrode 18 are provided on the first main surface 14a of the piezoelectric layer 14. The first comb-shaped electrode 17 has a first bus bar 22 and a plurality of first electrode fingers 25. One ends of the plurality of first electrode fingers 25 are respectively connected to the first bus bar 22. The second comb-shaped electrode 18 has a second bus bar 23 and a plurality of second electrode fingers 26. One ends of the plurality of second electrode fingers 26 are respectively connected to the second bus bar 23.

[0067] The first bus bar 22 and the second bus bar 23 face each other. The plurality of first electrode fingers 25 and the plurality of second electrode fingers 26 are interlaced with each other. The first electrode fingers 25 and the second electrode fingers 26 are alternately arranged in a direction orthogonal to the direction in which the first electrode fingers 25 and the second electrode fingers 26 extend.

[0068] The third electrode 19 includes a third bus bar 24 as a connection electrode and a plurality of third electrode fingers 27. The plurality of third electrode fingers 27 are provided on the first principal surface 14a of the piezoelectric layer 14. The plurality of third electrode fingers 27 are electrically connected to each other through the third bus bar 24.

[0069] The plurality of third electrode fingers 27 are arranged in a direction in which the first electrode fingers 25 and the second electrode fingers 26 are arranged. Thus, the first electrode fingers 25, the second electrode fingers 26, and the third electrode fingers 27 are arranged in one direction. The plurality of third electrode fingers 27 extend in parallel with the plurality of first electrode fingers 25 and the plurality of second electrode fingers.

[0070] Hereinafter, the direction in which the first electrode finger 25, the second electrode finger 26, and the third electrode finger 27 extend is referred to as the electrode finger extending direction, and the direction orthogonal to the electrode finger extending direction is referred to as the electrode finger orthogonal direction. When the direction in which the first electrode finger 25, the second electrode finger 26, and the third electrode finger 27 are arranged is referred to as the electrode finger arrangement direction, the electrode finger arrangement direction is parallel to the electrode finger orthogonal direction. In this specification, the first electrode finger 25, the second electrode finger 26, and the third electrode finger 27 are sometimes collectively referred to as simply an electrode finger. The first bus bar 22 and the second bus bar 23 are sometimes collectively referred to as simply a bus bar.

[0071] Figure 4 This is a schematic front cross-sectional view showing the vicinity of first to third electrode fingers in the first embodiment.

[0072] In the case of starting from the first electrode finger 25, the order in which the plurality of electrode fingers are arranged is an order in which the first electrode finger 25, the third electrode finger 27, the second electrode finger 26, and the third electrode finger 27 are one cycle. Therefore, the order in which the plurality of electrode fingers are arranged is the first electrode finger 25, the third electrode finger 27, the second electrode finger 26, the third electrode finger 27, the first electrode finger 25, the third electrode finger 27, the second electrode finger 26, ... If the input potential is represented by IN, the output potential is represented by OUT, and the reference potential is represented by GND, and the order of the plurality of electrode fingers is represented as the order of the potentials to which they are connected, it is continuous like IN, GND, OUT, GND, IN, GND, OUT, ...

[0073] In the present embodiment, in a region where a plurality of electrode fingers are provided, the electrode fingers located at both ends in the orthogonal direction of the electrode fingers are the third electrode fingers 27. In addition, in this region, the electrode fingers located at the ends in the orthogonal direction of the electrode fingers may be any of the first electrode fingers 25, the second electrode fingers 26, and the third electrode fingers 27.

[0074] like Figure 3 As shown, the third bus bar 24 as the connection electrode of the third electrode 19 electrically connects the plurality of third electrode fingers 27 to each other. Specifically, the third bus bar 24 is located in the region between the first bus bar 22 and the front ends of the plurality of second electrode fingers 26. The plurality of first electrode fingers 25 are also located in this region. However, the third bus bar 24 and the plurality of first electrode fingers 25 are electrically insulated from each other by the insulating film 29.

[0075] More specifically, the third bus bar 24 includes a plurality of first connection electrodes 24A and a second connection electrode 24B. Each first connection electrode 24A connects the front ends of two adjacent third electrode fingers 27 to each other. A U-shaped electrode is formed by the first connection electrode 24A and the two third electrode fingers 27. The second connection electrode 24B connects the plurality of first connection electrodes 24A to each other. An insulating film 29 is provided between the second connection electrode 24B and the plurality of first electrode fingers 25.

[0076] More specifically, the insulating film 29 is provided on the first main surface 14a of the piezoelectric layer 14 so as to cover a portion of the plurality of first electrode fingers 25. The insulating film 29 is provided in a region between the first bus bar 22 and the tips of the plurality of second electrode fingers 26. The insulating film 29 has a strip shape.

[0077] The insulating film 29 does not reach the first connecting electrode 24A of the third electrode 19. Moreover, the second connecting electrode 24B is provided across the insulating film 29 and the plurality of first connecting electrodes 24A. Specifically, the second connecting electrode 24B has a stripe 24a and a plurality of protrusions 24b. Each protrusion 24b extends from the stripe 24a toward each first connecting electrode 24A. Each protrusion 24b is connected to each first connecting electrode 24A. Thus, the plurality of third electrode fingers 27 are electrically connected to each other through the first connecting electrode 24A and the second connecting electrode 24B.

[0078] In the present embodiment, the third bus bar 24 is located in a region between the first bus bar 22 and the tips of the plurality of second electrode fingers 26. Therefore, the tips of the plurality of second electrode fingers 26 are opposed to the third bus bar 24 with a gap g1 in the electrode finger extending direction. On the other hand, the tips of the plurality of first electrode fingers 25 are opposed to the second bus bar 23 with a gap g2 in the electrode finger extending direction.

[0079] In addition, the third bus bar 24 may be located in a region between the second bus bar 23 and the tips of the plurality of first electrode fingers 25. In this case, the tips of the plurality of first electrode fingers 25 are spaced apart from the third bus bar 24. On the other hand, the tips of the plurality of second electrode fingers 26 are spaced apart from the first bus bar 22.

[0080] As such, in the first acoustic element 10A, when the third electrode 19 is a reference potential electrode, it is sufficient to be configured as follows. The front ends of the plurality of first electrode fingers 25 are sufficient to be opposed to electrodes connected to a potential different from that of the electrode finger, and which is any one of an input potential, an output potential, and a reference potential, at intervals in the electrode finger extension direction. Similarly, the front ends of the plurality of second electrode fingers 26 are sufficient to be opposed to electrodes connected to a potential different from that of the electrode finger, and which is any one of an input potential, an output potential, and a reference potential, at intervals in the electrode finger extension direction.

[0081] The dimension of these intervals along the electrode finger extending direction is defined as the interval length. In the present embodiment, the interval length of the interval g1 and the interval length of the interval g2 are the same. However, the interval length of the interval g1 and the interval length of the interval g2 may be different from each other.

[0082] The first acoustic element 10A is an elastic wave resonator configured to utilize bulk waves in a thickness shear mode. Figure 3 As shown in FIG. 1 , the first acoustic element 10A has a plurality of excitation regions C. In the plurality of excitation regions C, body waves in the thickness shear mode and elastic waves in other modes are excited. Figure 3 In FIG. 1 , only two excitation regions C among multiple excitation regions C are shown.

[0083] A part of the plurality of excitation regions C among all the excitation regions C are regions where the adjacent first electrode fingers 25 and third electrode fingers 27 overlap each other when viewed from the direction orthogonal to the electrode fingers, and are regions between the centers of the adjacent first electrode fingers 25 and third electrode fingers 27. The remaining plurality of excitation regions C are regions where the adjacent second electrode fingers 26 and third electrode fingers 27 overlap each other when viewed from the direction orthogonal to the electrode fingers, and are regions between the centers of the adjacent second electrode fingers 26 and third electrode fingers 27. These excitation regions C are arranged in the direction orthogonal to the electrode fingers.

[0084] In the functional electrode 11, the structure other than the third electrode 19 is the same as that of the IDT electrode. When viewed from the orthogonal direction of the electrode fingers, the area where the adjacent first electrode fingers 25 and second electrode fingers 26 overlap each other is the intersection area E. However, it can also be said that the intersection area E is an area where the adjacent first electrode fingers 25 and third electrode fingers 27 or the adjacent second electrode fingers 26 and third electrode fingers 27 overlap each other when viewed from the orthogonal direction of the electrode fingers. The intersection area E includes a plurality of excitation areas C. In addition, the intersection area E and the excitation area C are areas of the piezoelectric layer 14 defined based on the structure of the functional electrode 11.

[0085] Figure 5 is a schematic top view of the second acoustic element in the first embodiment. Figure 5 In the figure, wiring connected to the second acoustic element 10B and the first acoustic element 10A are omitted.

[0086] The second acoustic element 10B is configured to utilize bulk waves in a thickness shear mode. The second acoustic element 10B shares the piezoelectric substrate 12 with the first acoustic element 10A. The second acoustic element 10B includes the above-mentioned IDT electrode 31. More specifically, the IDT electrode 31 is provided on the first principal surface 14a of the piezoelectric layer 14 in the piezoelectric substrate 12.

[0087] like Figure 5 As shown, the IDT electrode 31 has a pair of bus bars and a plurality of electrode fingers. Specifically, the pair of bus bars is the 4th bus bar 32 and the 5th bus bar 33. The 4th bus bar 32 and the 5th bus bar 33 are opposite to each other. Specifically, the plurality of electrode fingers are a plurality of 4th electrode fingers 35 and a plurality of 5th electrode fingers 36. One end of the plurality of 4th electrode fingers 35 is connected to the 4th bus bar 32. One end of the plurality of 5th electrode fingers 36 is connected to the 5th bus bar 33. The plurality of 4th electrode fingers 35 and the plurality of 5th electrode fingers 36 are interlaced with each other.

[0088] Hereinafter, the fourth electrode finger 35 and the fifth electrode finger 36 are sometimes collectively described as simply an electrode finger. The fourth bus bar 32 and the fifth bus bar 33 are sometimes collectively described as simply a bus bar. In the second acoustic element 10B, the direction in which the fourth electrode finger 35 and the fifth electrode finger 36 extend is the electrode finger extending direction, and the direction orthogonal to the electrode finger extending direction is the electrode finger orthogonal direction.

[0089] The second acoustic element 10B also has an excitation region and an intersection region, similar to the first acoustic element 10A. In the second acoustic element 10B, the excitation region is a region where the adjacent fourth electrode finger 35 and fifth electrode finger 36 overlap each other when viewed from the orthogonal direction of the electrode fingers, and is a region between the centers of the adjacent fourth electrode finger 35 and fifth electrode finger 36. In the second acoustic element 10B, the intersection region is a region where the adjacent fourth electrode finger 35 and fifth electrode finger 36 overlap each other when viewed from the orthogonal direction of the electrode fingers. In the second acoustic element 10B, the intersection region also includes a plurality of excitation regions.

[0090] The present embodiment is characterized in that it has the following structure. 1) A first acoustic element 10A and a second acoustic element 10B are provided as acoustic coupling filters. 2) In a plan view, a plurality of first electrode fingers 25, a plurality of second electrode fingers 26, and a plurality of third electrode fingers 27 of the first acoustic element 10A and a plurality of fourth electrode fingers 35 and a fifth electrode finger 36 of the second acoustic element 10B overlap with the cavity 10a. Thus, when the elastic wave device 10 is used in a filter device, the miniaturization of the filter device can be promoted and the degradation of the filter characteristics can be suppressed. This is illustrated below by comparing the present embodiment with a comparative example.

[0091] The difference between the comparative example and the first embodiment is that the cavity portion where the functional electrode of the first acoustic element overlaps in a plan view and the cavity portion where the IDT electrode of the second acoustic element overlaps in a plan view are independently provided. In addition, in the comparative example, the first acoustic element and the second acoustic element are connected in parallel to each other, as in the first embodiment. In the first embodiment and the comparative example, the through characteristics are compared.

[0092] Figure 6 : is a graph showing the pass characteristics of the first embodiment and the comparative example. In addition, the pass characteristics are shown by S parameters.

[0093] First, if Figure 6 As shown in FIG. 1 , it can be seen that the filter characteristics are obtained in the elastic wave device 10 of the first embodiment. The first acoustic element 10A in the elastic wave device 10 is an acoustic coupling filter. In more detail, Figure 3As shown, the first acoustic element 10A has an excitation region C located between the centers of the adjacent first electrode finger 25 and the third electrode finger 27, and an excitation region C located between the centers of the adjacent second electrode finger 26 and the third electrode finger 27. Elastic waves of multiple modes including bulk waves of a thickness shear mode are excited in these excitation regions C. By coupling these modes, a filter waveform can be appropriately obtained.

[0094] Therefore, when elastic wave device 10 is used in a filter device, even if the number of elastic wave resonators constituting the filter device is small, an appropriate filter waveform can be obtained, thereby promoting miniaturization of the filter device.

[0095] like Figure 6 As shown by arrow F in , in the pass-through characteristic of the comparative example, a large ripple caused by an unnecessary wave is generated in the passband. In the pass-through characteristic of the comparative example, a large ripple caused by an unnecessary wave is also generated in a frequency band near the passband and on the high-frequency side of the passband. In contrast, it can be seen that in the first embodiment, the unnecessary wave is suppressed in the passband and outside the passband. In this way, in the first embodiment, the degradation of the filter characteristics can be suppressed. This is due to the following reasons.

[0096] exist Figure 1 In the first embodiment shown, the functional electrode 11 of the first acoustic element 10A and the IDT electrode 31 of the second acoustic element 10B overlap with the same cavity 10a in a plan view. As a result, the first acoustic element 10A and the second acoustic element 10B, which are acoustic coupling filters, are gradually acoustically coupled. In particular, the unnecessary waves generated in the second acoustic element 10B are reduced by the influence of the first acoustic element 10A, which is an acoustic coupling filter. As a result, in the elastic wave device 10, the unnecessary waves can be suppressed.

[0097] Hereinafter, the structure of the first embodiment will be described in more detail.

[0098] like Figure 1 As shown, a first signal potential wiring 28A, a second signal potential wiring 28B, a reference potential wiring 28C, and a common connection wiring 28D are provided on the first main surface 14a of the piezoelectric layer 14. The first signal potential wiring 28A is connected to the input potential. The second signal potential wiring 28B is connected to the output potential. The reference potential wiring 28C is connected to the reference potential. The first bus bar 22 of the first acoustic element 10A and the fourth bus bar 32 of the second acoustic element 10B are commonly connected to the common connection wiring 28D.

[0099] The first bus bar 22 of the first acoustic element 10A is connected to the first signal potential wiring 28A. Furthermore, the fourth bus bar 32 of the second acoustic element 10B is electrically connected to the first signal potential wiring 28A via the common connection wiring 28D and the first bus bar 22. Thus, the first acoustic element 10A and the second acoustic element 10B are connected to the same input potential. In addition, the first signal potential wiring 28A and the common connection wiring 28D may also be formed as one body.

[0100] The second bus bar 23 of the first acoustic element 10A and the fifth bus bar 33 of the second acoustic element 10B are commonly connected to the second signal potential wiring 28B. Thus, the first acoustic element 10A and the second acoustic element 10B are connected to the same output potential. In this way, the first acoustic element 10A and the second acoustic element 10B are connected in parallel with each other.

[0101] The third bus bar 24 as a connection electrode of the first acoustic element 10A is connected to the reference potential wiring 28C. The third bus bar 24 is connected to the reference potential via the reference potential wiring 28C.

[0102] In the first embodiment, a three-dimensional wiring portion including the third bus bar 24 and the common connection wiring 28D is formed. Specifically, an insulating film 39 is provided on the first main surface 14a of the piezoelectric layer 14 so as to cover a portion of the common connection wiring 28D. The common connection wiring 28D passes between the first main surface 14a and the insulating film 39 and is connected to the fourth bus bar 32.

[0103] On the other hand, the third bus bar 24 passes over the insulating film 39 and is connected to the reference potential wiring 28C. A portion of the common connection wiring 28D and a portion of the third bus bar 24 are opposed to each other with the insulating film 39 interposed therebetween. Thus, a three-dimensional wiring portion is formed. The common connection wiring 28D and the third bus bar 24 are electrically insulated from each other. By forming a three-dimensional wiring portion, the routing of the wiring can be simplified. Thus, the elastic wave device 10 can be made small. However, it is not necessary to form a three-dimensional wiring portion.

[0104] Preferably, as in the first embodiment, in a plan view, the plurality of excitation regions C of the first acoustic element 10A overlap with the cavity 10a as the sound reflection portion. Thus, the energy of the elastic wave in the first acoustic element 10A can be more reliably and effectively confined on the piezoelectric layer 14 side. Preferably, in a plan view, the plurality of excitation regions of the second acoustic element 10B overlap with the cavity 10a as the sound reflection portion. Thus, the energy of the elastic wave in the second acoustic element 10B can be more reliably and effectively confined on the piezoelectric layer 14 side.

[0105] In the first embodiment, the plurality of excitation regions of the first acoustic element 10A and the second acoustic element 10B overlap with the same cavity 10a in a plan view, thereby making it possible to more reliably and gradually acoustically couple the first acoustic element 10A and the second acoustic element 10B.

[0106] In addition, the sound reflecting portion may be a sound reflecting film such as a sound multilayer film described later. For example, a sound reflecting film may be provided on the surface of the supporting member.

[0107] In the first embodiment, in the first acoustic element 10A, the distance between the centers of the adjacent first electrode fingers 25 and the third electrode fingers 27 is the same as the distance between the centers of the adjacent second electrode fingers 26 and the third electrode fingers 27. However, the distance between the centers of the adjacent first electrode fingers 25 and the third electrode fingers 27 and the distance between the centers of the adjacent second electrode fingers 26 and the third electrode fingers 27 may not be constant. In this case, the longest distance between the distance between the centers of the adjacent first electrode fingers 25 and the third electrode fingers 27 and the distance between the centers of the adjacent second electrode fingers 26 and the third electrode fingers 27 is set to p. In addition, when the distance between the centers of the adjacent electrode fingers is fixed as in the first embodiment, the distance between the centers of any adjacent electrode fingers is the distance p.

[0108] When the thickness of the piezoelectric film is d, d / p is preferably 0.5 or less, and more preferably 0.24 or less. This allows the first acoustic element 10A to properly excite a thickness shear mode bulk wave. In the first embodiment, the thickness d is the thickness of the piezoelectric layer 14 .

[0109] In the second acoustic element 10B, when the longest distance between the centers of the adjacent fourth electrode finger 35 and the fifth electrode finger 36 is set to p, it is preferred that d / p is less than 0.5. It is more preferred that d / p is less than 0.24. Thus, in the second acoustic element 10B, a body wave of a thickness shear mode can be appropriately excited. In addition, in the first embodiment, the center-to-center distances of the adjacent fourth electrode finger 35 and the fifth electrode finger 36 are all the same. In this case, the center-to-center distances of any adjacent electrode fingers are all the distance p.

[0110] In addition, the first acoustic element of the present invention does not necessarily have to be configured to utilize the body wave of the thickness shear mode. For example, the first acoustic element of the present invention may also be configured to excite the plate wave. In this case, the excitation region is Figure 3 The intersection region E is shown. Similarly, the second acoustic element can also be configured to excite plate waves.

[0111] In the first embodiment, the piezoelectric layer 14 includes lithium niobate. In this specification, a certain member includes a certain material, including a small amount of impurities to the extent that the electrical characteristics of the elastic wave device are not significantly deteriorated. The relative bandwidth of the first acoustic element 10A depends on the Euler angles (φ, θ, ψ) of the lithium niobate used for the piezoelectric layer 14. The relative bandwidth can be expressed by (|fa-fr| / fr)×100[%] when the resonant frequency is fr and the anti-resonant frequency is fa.

[0112] The relationship between the relative bandwidth of the first acoustic element 10A and the Euler angles (φ, θ, ψ) of the piezoelectric layer 14 was derived when d / p was made as close to 0 as possible. In addition, φ in the Euler angles was set to 0°.

[0113] Figure 7 This is a diagram showing a map of the relative bandwidth with respect to the Euler angle (0°, θ, ψ) of LiNbO 3 when d / p is made as close to 0 as possible.

[0114] Figure 7 The hatched region R is a region where a relative bandwidth of at least 2% can be obtained. If the range of region R is approximated, it becomes the range represented by the following equations (1), (2), and (3). In addition, when φ in the Euler angle (φ, θ, ψ) is within the range of 0°±10°, the relationship between θ and ψ and the relative bandwidth is the same as Figure 7 When the piezoelectric layer 14 is a lithium tantalate layer, the relationship between θ and ψ in the Euler angle (in the range of 0°±10°, θ, ψ) and the relative bandwidth is also the same as Figure 7 The relationships shown are the same.

[0115] (within the range of 0°±10°, 0°~25°, arbitrary ψ) …Formula (1)

[0116] (Within the range of 0°±10°, 25°~100°, 0°~75°[(1-(θ-50) 2 / 2500)] 1 / 2 or 180°-75°[(1-(θ-50) 2 / 2500)] 1 / 2 ~180°) …Formula (2)

[0117] (0°±10°, 180°-40°[(1-(ψ-90) 2 / 8100)] 1 / 2 ~180°, arbitrary ψ)

[0118] …Formula (3)

[0119] The range of the Euler angles of the above-mentioned formula (1), formula (2), or formula (3) is preferably 0. This allows the relative bandwidth to be sufficiently widened. This allows the elastic wave device 10 including the first acoustic element 10A to be suitably used in a filter device.

[0120] like Figure 3 As shown in the first embodiment, the third electrode 19 has a third bus bar 24 as a connecting electrode and a plurality of third electrode fingers 27. The third electrode 19 is a comb-shaped electrode. However, the third electrode 19 may not be a comb-shaped electrode. For example, Figure 8 In the modification of the first embodiment shown, the third electrode 19A has a meandering shape. In this modification, the insulating film 29 is not provided on the piezoelectric layer 14. Moreover, the connection electrode 24C includes only a portion corresponding to the plurality of first connection electrodes 24A in the first embodiment. The connection electrode 24C of this modification is not a third bus bar.

[0121] More specifically, the third electrode 19A has a plurality of connection electrodes 24C located on the first bus bar 22 side and a plurality of connection electrodes 24C located on the second bus bar 23 side. The front end portions of two adjacent third electrode fingers 27 on the first bus bar 22 side or the front end portions on the second bus bar 23 side are connected to each other through the connection electrodes 24C. For example, the third electrode fingers 27 other than the two ends of the electrode fingers in the orthogonal direction among the plurality of third electrode fingers 27 are each connected to a connection electrode 24C at both ends of the front end portions on the first bus bar 22 side and the front end portions on the second bus bar 23 side. The third electrode finger 27 is connected to the third electrode fingers 27 on both sides through each connection electrode 24C. By repeating this structure, the shape of the third electrode 19A is set to a zigzag shape.

[0122] In this modification, the front ends of the plurality of second electrode fingers 26 are opposed to the plurality of connection electrodes 24C with a gap g1 in the electrode finger extension direction. That is, the front ends of the plurality of second electrode fingers 26 are opposed to the electrodes connected to the following potential with a gap g1 in the electrode finger extension direction, which potential is different from the potential of the electrode finger and is any one of the input potential, the output potential and the reference potential. Specifically, the second electrode finger 26 is connected to the output potential, and the connection electrode 24C is connected to the reference potential. The dimension of the gap g1 between the front ends of the second electrode fingers 26 and the connection electrode 24C along the electrode finger extension direction is the gap length.

[0123] Similarly, the front ends of the plurality of first electrode fingers 25 are respectively opposed to the plurality of connection electrodes 24C with a gap g2 in the electrode finger extension direction. That is, the front ends of the plurality of first electrode fingers 25 are respectively opposed to the electrodes connected to the following potential with a gap g2 in the electrode finger extension direction, which potential is a potential different from that of the electrode finger and is any one of the input potential, the output potential, and the reference potential. Specifically, the first electrode finger 25 is connected to the input potential, and the connection electrode 24C is connected to the reference potential. The dimension of the gap g2 between the front ends of the first electrode fingers 25 and the connection electrode 24C along the electrode finger extension direction is the gap length.

[0124] In this modification, the interval length of the interval g1 and the interval length of the interval g2 are the same, but the interval length of the interval g1 and the interval length of the interval g2 may be different from each other.

[0125] In this modification, the plurality of electrode fingers of the first acoustic element 10C and the plurality of electrode fingers of the second acoustic element 10B also overlap with the same cavity 10a in a plan view. Thus, similarly to the first embodiment, when the elastic wave device is used for a filter device, the filter device can be miniaturized and degradation of the filter characteristics can be suppressed.

[0126] Fig. 9 It is a schematic plan view of the first acoustic element in the second embodiment. Fig.10 This is a schematic front cross-sectional view showing the vicinity of the first to third electrode fingers in the second embodiment.

[0127] like Fig. 9 as well as Fig.10 As shown, this embodiment differs from the first embodiment in that a third electrode 19 is provided on the second principal surface 14b of the piezoelectric layer 14. Except for the above-described points, the elastic wave device of this embodiment has the same structure as the elastic wave device 10 of the first embodiment.

[0128] The configuration of the third electrode 19 in the present embodiment in a plan view is the same as that in the first embodiment. Therefore, the plurality of third electrode fingers 27 are respectively provided on the second main surface 14b of the piezoelectric layer 14 so as to be arranged with the first electrode finger 25 and the second electrode finger 26 in the direction in which the first electrode finger 25 and the second electrode finger 26 are arranged in a plan view. In a plan view, starting from the first electrode finger 25, the plurality of electrode fingers are arranged in an order that the first electrode finger 25, the third electrode finger 27, the second electrode finger 26, and the third electrode finger 27 form a cycle.

[0129] Fig.11 It is a schematic front cross-sectional view of an elastic wave device according to a second embodiment.

[0130] The third electrode 19 in the first acoustic element 40A is disposed in the cavity 10a. Therefore, in a plan view, the plurality of third electrode fingers 27 of the first acoustic element 40A overlap with the cavity 10a. The plurality of first electrode fingers 25 and the plurality of second electrode fingers 26 also overlap with the cavity 10a in a plan view. Furthermore, the cavity 10a and the plurality of fourth electrode fingers 35 and the fifth electrode fingers 36 of the second acoustic element 10B overlap in a plan view. Thus, similarly to the first embodiment, when the elastic wave device is used for the filter device, the miniaturization of the filter device can be promoted, and the degradation of the filter characteristics can be suppressed.

[0131] In this embodiment, the acoustic reflection portion is the cavity 10 a . However, as described above, the acoustic reflection portion may be an acoustic reflection film. In this case, the third electrode fingers 27 may be provided on the second main surface 14 b of the piezoelectric layer 14 so as to be buried in the acoustic reflection film.

[0132] In addition, the second acoustic element in the present invention does not necessarily have to be an elastic wave resonator. This example is described in the third embodiment.

[0133] Fig.12 It is a schematic plan view of an elastic wave device according to a third embodiment.

[0134] The present embodiment is different from the first embodiment in that the second acoustic element 50B is a capacitive element. Except for the above-described points, the elastic wave device 50 of the present embodiment has the same structure as the elastic wave device 10 of the first embodiment.

[0135] The second acoustic element 50B has an IDT electrode 51 as a functional electrode. The IDT electrode 51 has a pair of bus bars and a plurality of electrode fingers. Specifically, the pair of bus bars is a fourth bus bar 52 and a fifth bus bar 53. The fourth bus bar 52 and the fifth bus bar 53 are opposed to each other. Specifically, the plurality of electrode fingers are a plurality of fourth electrode fingers 55 and a plurality of fifth electrode fingers 56. One end of the plurality of fourth electrode fingers 55 is connected to the fourth bus bar 52. One end of the plurality of fifth electrode fingers 56 is connected to the fifth bus bar 53. The plurality of fourth electrode fingers 55 and the plurality of fifth electrode fingers 56 are interlaced with each other.

[0136] There is also a possibility that unnecessary waves are generated in the capacitor element in the filter device, and the filter characteristics are degraded. In contrast, in the present embodiment, the plurality of electrode fingers of the second acoustic element 50B as a capacitor element and the plurality of electrode fingers of the first acoustic element 10A as an acoustic coupling filter overlap with the same cavity 10a in a plan view. Thus, unnecessary waves can be suppressed.

[0137] In this embodiment, similarly to the first embodiment, when the elastic wave device 50 is used for a filter device, the filter device can be downsized and degradation of filter characteristics can be suppressed.

[0138] Fig.13 It is a schematic front cross-sectional view of an elastic wave device according to a fourth embodiment.

[0139] This embodiment differs from the first embodiment in that the second acoustic element 60B is a bulk wave resonator. This embodiment also differs from the first embodiment in the wiring structure. Except for the above-mentioned points, the elastic wave device 60 of this embodiment has the same structure as the elastic wave device 10 of the first embodiment.

[0140] The functional electrode of the second acoustic element 60B has a fourth electrode 67 and a fifth electrode 68 as the first electrode and the second electrode. The fourth electrode 67 is provided on the first principal surface 14a of the piezoelectric layer 14. The fifth electrode 68 is provided on the second principal surface 14b of the piezoelectric layer 14. The fourth electrode 67 and the fifth electrode 68 are opposed to each other with the piezoelectric layer 14 sandwiched therebetween. In the piezoelectric layer 14, the region sandwiched by the fourth electrode 67 and the fifth electrode 68 is an excitation region.

[0141] The fifth electrode 68 in the second acoustic element 60B is disposed in the cavity 10a. Therefore, in a plan view, the fifth electrode 68 of the second acoustic element 60B overlaps with the cavity 10a. The fourth electrode 67 also overlaps with the cavity 10a in a plan view. Furthermore, the cavity 10a and the plurality of first electrode fingers 25, the plurality of second electrodes 26, and the plurality of third electrode fingers 27 of the first acoustic element 10A overlap in a plan view. Thus, similarly to the first embodiment, when the elastic wave device is used for the filter device, the miniaturization of the filter device can be promoted, and the degradation of the filter characteristics can be suppressed.

[0142] In the elastic wave device 60 , the fourth electrode 67 of the second acoustic element 60B and the first comb-shaped electrode 17 of the first acoustic element 10A are connected to the same input potential. The fourth electrode 67 and the first comb-shaped electrode 17 are connected by wiring provided on the first principal surface 14 a of the piezoelectric layer 14 .

[0143] The fifth electrode 68 of the second acoustic element 60B and the second comb-shaped electrode 18 of the first acoustic element 10A are connected to the same output potential. For example, a through electrode penetrating the piezoelectric layer 14 may be provided. The fifth electrode 68 and the second comb-shaped electrode 18 are electrically connected via the through electrode and appropriate wiring.

[0144] In the present embodiment, the acoustic reflection portion is the cavity portion 10 a . However, the acoustic reflection portion may be an acoustic reflection film. In this case, the fifth electrode 68 may be provided on the second main surface 14 b of the piezoelectric layer 14 so as to be buried in the acoustic reflection film.

[0145] Fig.14 It is a schematic plan view of an elastic wave device according to a fifth embodiment.

[0146] The present embodiment differs from the first embodiment in that the second acoustic element 70B is an acoustic coupling filter. The present embodiment also differs from the first embodiment in that the first signal potential wiring 28A is integrally formed with the common connection wiring. Except for the above-mentioned aspects, the elastic wave device 70 of the present embodiment has the same structure as the elastic wave device 10 of the first embodiment.

[0147] The first acoustic element 10A and the second acoustic element 70B are connected in parallel to each other. The first acoustic element 10A and the second acoustic element 70B are not split resonators obtained by splitting one elastic wave resonator in parallel.

[0148] The second acoustic element 70B includes a first comb-shaped electrode, a second comb-shaped electrode, and a third electrode independently of the first acoustic element 10A. In addition, hereinafter, the first comb-shaped electrode of the second acoustic element 70B is set as the fourth comb-shaped electrode. The second comb-shaped electrode of the second acoustic element 70B is set as the fifth comb-shaped electrode. The third electrode of the second acoustic element 70B is set as the sixth electrode.

[0149] The fourth comb-shaped electrode is connected to the input potential. The fifth comb-shaped electrode is connected to the output potential. In the present embodiment, the sixth electrode is connected to the reference potential. In the present embodiment, the sixth electrode is a reference potential electrode. In addition, the sixth electrode does not necessarily have to be connected to the reference potential. The sixth electrode only needs to be connected to a potential different from that of the fourth comb-shaped electrode and the fifth comb-shaped electrode. However, it is preferred that the sixth electrode is connected to the reference potential.

[0150] The fourth comb-shaped electrode and the fifth comb-shaped electrode are provided on the first main surface 14a of the piezoelectric layer 14. The fourth comb-shaped electrode has a fourth bus bar 72 as the first bus bar and a plurality of fourth electrode fingers 75 as a plurality of first electrode fingers. One ends of the plurality of fourth electrode fingers 75 are respectively connected to the fourth bus bar 72. The fifth comb-shaped electrode has a fifth bus bar 73 as the second bus bar and a plurality of fifth electrode fingers 76 as a plurality of second electrode fingers. One ends of the plurality of fifth electrode fingers 76 are respectively connected to the fifth bus bar 73.

[0151] The fourth bus bar 72 and the fifth bus bar 73 face each other. The fourth electrode fingers 75 and the fifth electrode fingers 76 are interlaced with each other. The fourth electrode fingers 75 and the fifth electrode fingers 76 are alternately arranged in a direction orthogonal to the direction in which the fourth electrode fingers 75 and the fifth electrode fingers 76 extend.

[0152] The sixth electrode includes a sixth bus bar 74 as a connection electrode and a plurality of sixth electrode fingers 77 as a plurality of third electrode fingers. The plurality of sixth electrode fingers 77 are provided on the first principal surface 14a of the piezoelectric layer 14. The plurality of sixth electrode fingers 77 are electrically connected to each other through the sixth bus bar 74. The sixth bus bar 74 is configured similarly to the third bus bar 24 of the first acoustic element 10A. Therefore, the sixth bus bar includes a first connection electrode and a second connection electrode.

[0153] The plurality of sixth electrode fingers 77 are arranged in a direction in which the fourth electrode fingers 75 and the fifth electrode fingers 76 are arranged. Thus, the fourth electrode fingers 75, the fifth electrode fingers 76, and the sixth electrode fingers 77 are arranged in one direction. The plurality of sixth electrode fingers 77 extend in parallel with the plurality of fourth electrode fingers 75 and the plurality of second electrode fingers.

[0154] In the second acoustic element 70B, the direction in which the fourth electrode finger 75, the fifth electrode finger 76, and the sixth electrode finger 77 extend is the electrode finger extending direction, and the direction orthogonal to the electrode finger extending direction is the electrode finger orthogonal direction. Hereinafter, the fourth electrode finger 75, the fifth electrode finger 76, and the sixth electrode finger 77 are sometimes collectively described as a plurality of electrode fingers.

[0155] When starting from the fourth electrode finger 75 , the plurality of electrode fingers in the second acoustic element 70B are arranged in an order in which the fourth electrode finger 75 , the sixth electrode finger 77 , the fifth electrode finger 76 , and the sixth electrode finger 77 form one cycle.

[0156] The sixth bus bar 74 is located in a region between the fourth bus bar 72 and the tips of the plurality of fifth electrode fingers 76. The sixth bus bar 74 and the plurality of fourth electrode fingers 75 are electrically insulated from each other by an insulating film.

[0157] The tips of the fifth electrode fingers 76 face the sixth bus bar 74 at intervals g4 in the electrode finger extending direction. On the other hand, the tips of the fourth electrode fingers 75 face the fifth bus bar 73 at intervals g5 in the electrode finger extending direction.

[0158] In addition, in the second acoustic element 70B, when the sixth electrode is a reference potential electrode, it is sufficient to be configured as follows in the same manner as the first acoustic element 10A. The front ends of the plurality of fourth electrode fingers 75 are sufficient to be opposed to electrodes connected to a potential different from that of the electrode finger, and which is any one of an input potential, an output potential, and a reference potential, respectively, with intervals in the electrode finger extension direction. Similarly, the front ends of the plurality of fifth electrode fingers 76 are sufficient to be opposed to electrodes connected to a potential different from that of the electrode finger, and which is any one of an input potential, an output potential, and a reference potential, respectively, with intervals in the electrode finger extension direction.

[0159] The dimension of these intervals along the electrode finger extension direction is the interval length of the second acoustic element 70B. In this embodiment, the interval length of the interval g4 is the same as the interval length of the interval g5. However, the interval length of the interval g4 and the interval length of the interval g5 may be different from each other.

[0160] As in the first embodiment, in the first acoustic element 10A, the interval length of the interval g1 and the interval length of the interval g2 are the same, but the interval length of the interval g1 and the interval length of the interval g2 may be different from each other.

[0161] In the present embodiment, the interval lengths between the first acoustic element 10A and the second acoustic element 70B are different from each other.

[0162] The second acoustic element 70B has a plurality of excitation regions and intersection regions similarly to the first acoustic element 10A. Specifically, a portion of the plurality of excitation regions among all the excitation regions are regions where the adjacent fourth electrode finger 75 and sixth electrode finger 77 overlap when viewed from the orthogonal direction of the electrode fingers, and are regions between the centers of the adjacent fourth electrode finger 75 and sixth electrode finger 77. The remaining plurality of excitation regions are regions where the adjacent fifth electrode finger 76 and sixth electrode finger 77 overlap when viewed from the orthogonal direction of the electrode fingers, and are regions between the centers of the adjacent fifth electrode finger 76 and sixth electrode finger 77. These excitation regions are arranged in the orthogonal direction of the electrode fingers.

[0163] When viewed from the orthogonal direction of the electrode fingers, the area where the adjacent fourth electrode finger 75 and fifth electrode finger 76 overlap each other is the intersection area. However, it can also be said that the intersection area is the area where the adjacent fourth electrode finger 75 and sixth electrode finger 77 or the adjacent fifth electrode finger 76 and sixth electrode finger 77 overlap each other when viewed from the orthogonal direction of the electrode fingers.

[0164] The plurality of first electrode fingers 25, the plurality of second electrode fingers 26, and the plurality of third electrode fingers 27 in the first acoustic element 10A overlap with the cavity 10a in a plan view. The cavity 10a overlaps with the plurality of fourth electrode fingers 75, the plurality of fifth electrode fingers 76, and the plurality of sixth electrode fingers 77 in the second acoustic element 70B in a plan view. Thus, similarly to the first embodiment, when the elastic wave device is used for the filter device, the miniaturization of the filter device can be promoted, and the degradation of the filter characteristics can be suppressed.

[0165] like Fig.14 As shown, in this embodiment, the third bus bar 24 of the first acoustic element 10A and the sixth bus bar 74 of the second acoustic element 70B are integrally formed. The third bus bar 24 and the sixth bus bar 74 are connected to the reference potential via the reference potential wiring 28C. This simplifies the wiring and effectively promotes the miniaturization of the filter device.

[0166] When both the first acoustic element 10A and the second acoustic element 70B are acoustic coupling filters, it is sufficient that at least one of the following parameters is different between the first acoustic element 10A and the second acoustic element 70B. Specifically, the above parameters are the total number of electrode fingers, the center-to-center distance between adjacent electrode fingers, the width of the electrode fingers, the thickness of the electrode fingers, the spacing length, and the cross width. In addition, the width of the electrode finger is the dimension of the electrode finger along the orthogonal direction of the electrode finger. The cross width is the dimension of the cross region along the extension direction of the electrode finger.

[0167] In the fifth embodiment, the first acoustic element 10A and the second acoustic element 70B have different interval lengths. Fig.15 In the first variation of the fifth embodiment shown, the total number of the plurality of electrode fingers in the first acoustic element 10A and the second acoustic element 70D is different from each other. Specifically, the total number of the plurality of first electrode fingers 25, the plurality of second electrode fingers 26, and the plurality of third electrode fingers 27 is different from the total number of the plurality of fourth electrode fingers 75, the plurality of fifth electrode fingers 76, and the plurality of sixth electrode fingers 77.

[0168] exist Fig.16In the second variant of the fifth embodiment shown, in the first acoustic element 10A and the second acoustic element 70E, the center-to-center distances of adjacent electrode fingers are different from each other. Specifically, the center-to-center distance between the adjacent first electrode finger 25 and the third electrode finger 27 and the center-to-center distance between the adjacent second electrode finger 26 and the third electrode finger 27 are set as the center-to-center distance p1. The center-to-center distance between the adjacent fourth electrode finger 75 and the sixth electrode finger 77 and the center-to-center distance between the adjacent fifth electrode finger 76 and the sixth electrode finger 77 are set as the center-to-center distance p2. In this variant, in the first acoustic element 10A, the center-to-center distance p1 is fixed. Similarly, in the second acoustic element 70E, the center-to-center distance p2 is fixed. Moreover, p1≠p2.

[0169] In addition, in the first acoustic element 10A, the center-to-center distance p1 may not be fixed. In this case, the distance p in the first acoustic element 10A and the center-to-center distance p2 in the second acoustic element 10B may be different. The distance p in the first acoustic element 10A is the longest distance between the center distances of the adjacent first electrode finger 25 and the third electrode finger 27 and the center distances of the adjacent second electrode finger 26 and the third electrode finger 27. When the center-to-center distance p1 is fixed, any center-to-center distance p1 is the distance p.

[0170] Alternatively, in the second acoustic element 70E, the center-to-center distance p2 may not be fixed. In this case, it is sufficient that the distance p in the second acoustic element 70E and the center-to-center distance p1 in the first acoustic element 10A are different from each other. On the other hand, in the case where both the center-to-center distance p1 and the center-to-center distance p2 are not fixed, it is sufficient that the distance p in the first acoustic element 10A and the distance p in the second acoustic element 70E are different from each other. In this specification, the so-called center-to-center distances are different from each other, which means that the absolute value of the difference between the center-to-center distances is greater than 1% relative to any center-to-center distance.

[0171] exist Fig.17 In the third variation of the fifth embodiment shown in FIG. 1 , the widths of the electrode fingers in the first acoustic element 10A and the second acoustic element 70F are different from each other. Specifically, the widths of the first electrode finger 25, the second electrode finger 26, and the third electrode finger 27 in the first acoustic element 10A and the widths of the fourth electrode finger 75, the fifth electrode finger 76, and the sixth electrode finger 77 in the second acoustic element 70F are different from each other. In this specification, the widths of the electrode fingers are different from each other, which means that the absolute value of the difference between the widths is 1% or more relative to any width.

[0172] exist Fig.18In the fourth variation of the fifth embodiment shown in the figure, the thicknesses of the electrode fingers are different from each other in the first acoustic element 10A and the second acoustic element 70G. Specifically, the thicknesses of the first electrode finger 25, the second electrode finger 26, and the third electrode finger 27 in the first acoustic element 10A and the thicknesses of the fourth electrode finger 75, the fifth electrode finger 76, and the sixth electrode finger 77 in the second acoustic element 70G are different from each other. In this specification, the so-called different thicknesses of the electrode fingers means that the absolute value of the difference between the thicknesses is 1% or more relative to any thickness.

[0173] exist Fig.19 In the fifth variation of the fifth embodiment shown, the cross widths are different in the first acoustic element 10A and the second acoustic element 70H. Specifically, when the cross width in the first acoustic element 10A is Ap1 and the cross width in the second acoustic element 70H is Ap2, Ap1≠Ap2. In this specification, the cross widths are different from each other, which means that the absolute value of the difference between the cross widths is 1% or more relative to any cross width.

[0174] In the first to fifth modified examples, similarly to the fifth embodiment, when the elastic wave device is used for the filter device, the filter device can be miniaturized and degradation of the filter characteristics can be suppressed.

[0175] The thickness shear mode is described in detail below using an example in which the functional electrode is an IDT electrode. The "electrode" in the IDT electrode described below is equivalent to the electrode finger. The elastic wave device in the following example is an elastic wave resonator. The supporting member in the following example is equivalent to the supporting substrate in the present invention. In the following, the reference potential is sometimes recorded as the ground potential.

[0176] Fig. 20 (a) is a schematic perspective view showing the appearance of an elastic wave device using a thickness shear mode bulk wave, Fig. 20 (b) is a top view showing the electrode structure on the piezoelectric layer. Fig.21 yes Fig. 20 (a) is a cross-sectional view of the portion along line AA.

[0177] The elastic wave device 1 has a piezoelectric layer 2 containing LiNbO3. The piezoelectric layer 2 may also contain LiTaO3. The cutting angle of LiNbO3 and LiTaO3 is Z-cut, but it may also be a rotated Y-cut or X-cut. The thickness of the piezoelectric layer 2 is not particularly limited, but in order to effectively excite the thickness shear mode, it is preferably greater than 40nm and less than 1000nm, and more preferably greater than 50nm and less than 1000nm. The piezoelectric layer 2 has a first principal surface 2a and a second principal surface 2b facing each other. An electrode 3 and an electrode 4 are provided on the first principal surface 2a. Here, electrode 3 is an example of a "first electrode", and electrode 4 is an example of a "second electrode". In Fig. 20 (a) and Fig. 20 In (b), a plurality of electrodes 3 are connected to a first bus bar 5. A plurality of electrodes 4 are connected to a second bus bar 6. The plurality of electrodes 3 and the plurality of electrodes 4 are interlaced with each other. The electrodes 3 and 4 have a rectangular shape and a length direction. In a direction perpendicular to the length direction, the electrode 3 and the adjacent electrode 4 are opposed to each other. The length directions of the electrodes 3 and 4 and the directions perpendicular to the length directions of the electrodes 3 and 4 are directions intersecting with the thickness direction of the piezoelectric layer 2. Therefore, it can also be said that the electrode 3 and the adjacent electrode 4 are opposed to each other in a direction intersecting with the thickness direction of the piezoelectric layer 2. In addition, the length directions of the electrodes 3 and 4 can also be perpendicular to the length directions of the electrodes 3 and 4. Fig. 20 (a) and Fig. 20 The direction perpendicular to the length direction of electrodes 3 and 4 shown in (b) is reversed. Fig. 20 (a) and Fig. 20 In (b), the electrodes 3 and 4 may be extended in the direction in which the first bus bar 5 and the second bus bar 6 extend. In this case, the first bus bar 5 and the second bus bar 6 are Fig. 20 (a) and Fig. 20(b) becomes extended in the direction in which electrodes 3 and 4 extend. Moreover, a pair of structures in which an electrode 3 connected to one potential and an electrode 4 connected to another potential are adjacent are provided with multiple pairs in a direction orthogonal to the length direction of the electrodes 3 and 4. Here, the so-called electrode 3 and electrode 4 are adjacent, which does not mean that the electrodes 3 and 4 are configured to be in direct contact, but refers to the case where the electrodes 3 and 4 are configured to be spaced apart. In addition, when the electrodes 3 and 4 are adjacent, electrodes connected to the signal (hot) electrode and the ground electrode, including other electrodes 3 and 4, are not configured between the electrodes 3 and 4. The number of pairs does not need to be an integer pair, and can also be 1.5 pairs, 2.5 pairs, etc. The center-to-center distance (i.e., the spacing) between the electrodes 3 and 4 is preferably in the range of 1 μm or more and 10 μm or less. In addition, the width of the electrodes 3 and 4 (i.e., the size in the opposing direction of the electrodes 3 and 4) is preferably in the range of 50 nm or more and 1000 nm or less, and more preferably in the range of 150 nm or more and 1000 nm or less. The center-to-center distance between electrodes 3 and 4 is the distance connecting the center of the dimension (width dimension) of electrode 3 in a direction perpendicular to the length direction of electrode 3 and the center of the dimension (width dimension) of electrode 4 in a direction perpendicular to the length direction of electrode 4.

[0178] In addition, in the elastic wave device 1, a Z-cut piezoelectric layer is used, so the direction orthogonal to the length direction of the electrodes 3 and 4 is a direction orthogonal to the polarization direction of the piezoelectric layer 2. When a piezoelectric body with another cutting angle is used as the piezoelectric layer 2, it is not limited to this. Here, the so-called "orthogonal" is not limited to the case of being strictly orthogonal, and can also be approximately orthogonal (the angle formed by the direction orthogonal to the length direction of the electrodes 3 and 4 and the polarization direction is, for example, within the range of 90°±10°).

[0179] A support member 8 is stacked on the second main surface 2b side of the piezoelectric layer 2 via an insulating layer 7. The insulating layer 7 and the support member have a frame-like shape. Fig.21 As shown, there are through holes 7a and 8a. Thus, a cavity 9 is formed. The cavity 9 is provided so as not to hinder the vibration of the excitation region C of the piezoelectric layer 2. Therefore, the support member 8 is stacked on the second main surface 2b via the insulating layer 7 at a position that does not overlap with the portion where at least one pair of electrodes 3 and 4 is provided. In addition, the insulating layer 7 may not be provided. Therefore, the support member 8 can be directly or indirectly stacked on the second main surface 2b of the piezoelectric layer 2.

[0180] The insulating layer 7 includes silicon oxide. However, in addition to silicon oxide, suitable insulating materials such as silicon nitride oxide and alumina can also be used. The supporting member 8 includes Si. The surface orientation of the surface of Si on the side of the piezoelectric layer 2 can be (100), (110), or (111). The Si constituting the supporting member 8 is preferably a high resistor with a resistivity of 4 kΩcm or more. However, the supporting member 8 can also be composed of suitable insulating materials or semiconductor materials.

[0181] As the material of the supporting member 8, for example, piezoelectrics such as aluminum oxide, lithium tantalate, lithium niobate, and quartz, various ceramics such as alumina, magnesium oxide, sapphire, silicon nitride, aluminum nitride, silicon carbide, zirconium oxide, cordierite, mullite, steatite, and forsterite, dielectrics such as diamond and glass, and semiconductors such as gallium nitride can be used.

[0182] The plurality of electrodes 3, 4 and the first bus bar 5 and the second bus bar 6 include a suitable metal or alloy such as Al or AlCu alloy. In the elastic wave device 1, the electrodes 3, 4 and the first bus bar 5 and the second bus bar 6 have a structure in which an Al film is stacked on a Ti film. Alternatively, a bonding layer other than a Ti film may be used.

[0183] When driving, an AC voltage is applied between the plurality of electrodes 3 and the plurality of electrodes 4. More specifically, an AC voltage is applied between the first bus bar 5 and the second bus bar 6. As a result, it is possible to obtain the resonance characteristics of the bulk wave utilizing the thickness shear mode excited in the piezoelectric layer 2. In addition, in the elastic wave device 1, when the thickness of the piezoelectric layer 2 is set to d and the center-to-center distance between any adjacent electrodes 3 and 4 in the plurality of pairs of electrodes 3 and 4 is set to p, d / p is set to be less than 0.5. Therefore, the bulk wave of the thickness shear mode mentioned above can be effectively excited, and good resonance characteristics can be obtained. More preferably, d / p is less than 0.24, in which case, even better resonance characteristics can be obtained.

[0184] In the elastic wave device 1, the above structure is provided, so even if the number of pairs of electrodes 3 and 4 is reduced in order to achieve miniaturization, the Q value is not likely to decrease. This is because even if the number of electrode fingers in the reflectors on both sides is reduced, the propagation loss is small. In addition, the reason why the number of electrode fingers can be reduced is because the body wave of the thickness shear mode is utilized. Fig. 22 (a) and Fig. 22 (b) explains the difference between the Lamb waves used in the elastic wave device and the body waves of the thickness shear mode described above.

[0185] Fig. 22(a) is a schematic front cross-sectional view for explaining the Lamb wave propagating in the piezoelectric film of the elastic wave device described in the Japanese Patent Gazette: Japanese Patent Gazette No. 2012-257019. Here, the wave propagates in the piezoelectric film 201 as shown by the arrow. Here, in the piezoelectric film 201, the first main surface 201a and the second main surface 201b are opposite to each other, and the thickness direction connecting the first main surface 201a and the second main surface 201b is the Z direction. The X direction is the direction in which the electrode fingers of the IDT electrode are arranged. Fig. 22 As shown in (a), if it is a Lamb wave, the wave propagates in the X direction as shown in the figure. Since it is a plate wave, the piezoelectric film 201 vibrates as a whole, but the wave propagates in the X direction, so reflectors are arranged on both sides to obtain resonance characteristics. Therefore, wave propagation loss occurs, and when miniaturization is sought, that is, when the number of pairs of electrode fingers is reduced, the Q value decreases.

[0186] In contrast, Fig. 22 As shown in (b), in the elastic wave device 1, the vibration displacement is in the thickness shear direction, so the wave generally propagates and resonates in the direction connecting the first main surface 2a and the second main surface 2b of the piezoelectric layer 2 (i.e., the Z direction). That is, the X-direction component of the wave is significantly smaller than the Z-direction component. Moreover, since the resonance characteristic is obtained by the propagation of the wave in the Z direction, it is not easy to generate propagation loss even if the number of electrode fingers of the reflector is reduced. Furthermore, even if the number of pairs of electrode pairs including electrodes 3 and 4 is reduced in order to develop miniaturization, it is not easy to generate a decrease in the Q value.

[0187] In addition, if Fig.23 As shown in FIG. 1 , the amplitude directions of the volume waves in the thickness shear mode are opposite in the first region 451 included in the excitation region C of the piezoelectric layer 2 and in the second region 452 included in the excitation region C. Fig.23 , a body wave is schematically shown when a voltage is applied between the electrode 3 and the electrode 4 so that the electrode 4 has a higher potential than the electrode 3. The first region 451 is a region between the imaginary plane VP1 and the first principal surface 2a in the excitation region C, wherein the imaginary plane VP1 is orthogonal to the thickness direction of the piezoelectric layer 2 and divides the piezoelectric layer 2 into two parts. The second region 452 is a region between the imaginary plane VP1 and the second principal surface 2b in the excitation region C.

[0188] As described above, elastic wave device 1 includes at least one pair of electrodes including electrode 3 and electrode 4 , but waves are not propagated in the X direction, so there is no need to be a plurality of pairs of electrodes including electrode 3 and electrode 4 . In other words, at least one pair of electrodes is sufficient.

[0189] For example, the electrode 3 is an electrode connected to a signal (hot) potential, and the electrode 4 is an electrode connected to a ground potential. However, the electrode 3 may be connected to a ground potential, and the electrode 4 may be connected to a signal potential. In the elastic wave device 1, at least one pair of electrodes is an electrode connected to a signal potential or an electrode connected to a ground potential as described above, and no floating electrode is provided.

[0190] Fig.24 It is shown Fig.21 The resonance characteristics of the elastic wave device are shown in FIG. 1. The design parameters of the elastic wave device 1 that obtain the resonance characteristics are as follows.

[0191] Piezoelectric layer 2: LiNbO3 with Euler angles of (0°, 0°, 90°), thickness = 400nm.

[0192] When observed in a direction orthogonal to the length direction of electrode 3 and electrode 4, the length of the overlapping area of ​​electrode 3 and electrode 4 (i.e., excitation area C) = 40 μm, the number of pairs of electrodes including electrodes 3 and 4 = 21 pairs, the center distance between electrodes = 3 μm, the width of electrodes 3 and 4 = 500 nm, and d / p = 0.133.

[0193] Insulating layer 7: a silicon oxide film having a thickness of 1 μm.

[0194] Supporting member 8: Si.

[0195] The length of the excitation region C refers to the dimension of the excitation region C along the length direction of the electrodes 3 and 4 .

[0196] In elastic wave device 1 , the inter-electrode distances of the electrode pairs including electrodes 3 and 4 are set equal in all pairs. That is, electrodes 3 and electrodes 4 are arranged at equal intervals.

[0197] according to Fig.24 It is clear that, despite the absence of a reflector, a good resonance characteristic with a relative bandwidth of 12.5% ​​is obtained.

[0198] When the thickness of the piezoelectric layer 2 is d and the center-to-center distance between the electrodes 3 and 4 is p, as described above, in the elastic wave device 1, d / p is 0.5 or less, and more preferably 0.24 or less. Fig.25 This is explained.

[0199] and got Fig.24 The elastic wave devices having the same resonant characteristics as those shown above are obtained by changing d / p. Fig.25 3 is a diagram showing the relationship between d / p and the relative bandwidth of a resonator as an elastic wave device.

[0200] according to Fig.25 It is clear that if d / p>0.5, even if d / p is adjusted, the relative bandwidth is less than 5%. In contrast, when d / p≤0.5, if d / p is changed within this range, the relative bandwidth can be set to more than 5%, that is, a resonator with a high coupling coefficient can be constructed. In addition, when d / p is less than 0.24, the relative bandwidth can be increased to more than 7%. In addition, if d / p is adjusted within this range, a resonator with a wider relative bandwidth can be obtained, and a resonator with a higher coupling coefficient can be realized. Therefore, it can be seen that by setting d / p to less than 0.5, a resonator with a high coupling coefficient that utilizes the body wave of the thickness shear mode mentioned above can be constructed.

[0201] Fig.26 1 is a top view of an elastic wave device using a thickness shear mode bulk wave. In the elastic wave device 80, a pair of electrodes including an electrode 3 and an electrode 4 are provided on the first principal surface 2a of the piezoelectric layer 2. Fig.26 K in is the crossover width. As described above, in the elastic wave device of the present invention, the number of pairs of electrodes may be one pair. Even in this case, as long as the above d / p is 0.5 or less, the thickness shear mode body wave can be effectively excited.

[0202] In the elastic wave device 1, preferably, the metallization ratio MR of any adjacent electrodes 3 and 4 among the plurality of electrodes 3 and 4 relative to the excitation region C preferably satisfies MR≤1.75(d / p)+0.075, wherein the excitation region C is a region where the adjacent electrodes 3 and 4 overlap when viewed in opposite directions. In this case, the stray emission can be effectively reduced. Fig. 27 as well as Fig.28 This is explained. Fig. 27 : is a reference diagram showing an example of the resonance characteristics of the elastic wave device 1. Spurious signals indicated by arrow B appear between the resonance frequency and the antiresonance frequency. In addition, d / p=0.08 is assumed, and the Euler angles of LiNbO3 are assumed to be (0°, 0°, 90°). In addition, the metallization ratio MR is assumed to be 0.35.

[0203] Reference Fig. 20 (b) will explain the metallization ratio MR. Fig. 20In the electrode structure of (b), when focusing on a pair of electrodes 3 and 4, it is assumed that only the pair of electrodes 3 and 4 are provided. In this case, the portion surrounded by the single-dot chain line becomes the excitation region C. The so-called excitation region C is the region where the electrode 3 overlaps with the electrode 4, the region where the electrode 4 overlaps with the electrode 3, and the region between the electrode 3 and the electrode 4 where the electrode 3 overlaps with the electrode 4 when the electrode 3 and the electrode 4 are observed in the direction perpendicular to the longitudinal direction of the electrodes 3 and 4 (i.e., the opposing direction). And, the area of ​​the electrodes 3 and 4 in the excitation region C relative to the area of ​​the excitation region C is the metallization ratio MR. That is, the metallization ratio MR is the ratio of the area of ​​the metallized portion to the area of ​​the excitation region C.

[0204] When a plurality of pairs of electrodes are provided, the ratio of the total area of ​​the metallized portions included in all the excitation regions to the area of ​​the excitation regions may be defined as MR.

[0205] Fig.28 The graph shows the relationship between the relative bandwidth and the phase rotation amount of the impedance of the spurious signal normalized by 180 degrees when a large number of spurious wave resonators are formed according to the structure of the spurious wave device 1. In addition, various changes and adjustments were made to the film thickness of the piezoelectric layer and the size of the electrode with respect to the relative bandwidth. In addition, although Fig.28 These are the results obtained when a piezoelectric layer including Z-cut LiNbO 3 is used; however, the same tendency is observed even when a piezoelectric layer having other cut angles is used.

[0206] exist Fig.28 In the area surrounded by ellipse J, the spurious signal becomes larger and becomes 1.0. Fig.28 It is clear that if the relative bandwidth exceeds 0.17, that is, if it exceeds 17%, even if the parameters constituting the relative bandwidth are changed, large spurious signals with a spurious level of 1 or more will appear in the passband. Fig. 27 As shown in the resonance characteristics, large spurious signals indicated by arrow B appear in the band. Therefore, the relative bandwidth is preferably 17% or less. In this case, spurious signals can be reduced by adjusting the film thickness of the piezoelectric layer 2, the dimensions of the electrodes 3 and 4, and the like.

[0207] Fig.29 2 is a graph showing the relationship between d / 2p, metallization ratio MR, and relative bandwidth. Various elastic wave devices having different d / 2p and MR in the elastic wave device were constructed, and the relative bandwidth was measured. Fig.29The hatched portion on the right side of the dotted line D is an area where the relative bandwidth is less than 17%. The boundary between the hatched area and the unhatched area can be represented by MR=3.5(d / 2p)+0.075. That is, MR=1.75(d / p)+0.075. Therefore, it is preferred that MR≤1.75(d / p)+0.075. In this case, it is easy to make the relative bandwidth less than 17%. More preferably, Fig.29 The area on the right side of MR=3.5(d / 2p)+0.05 indicated by the dashed line D1 in FIG. 1. That is, if MR≤1.75(d / p)+0.05, the relative bandwidth can be reliably made 17% or less.

[0208] Fig.30 This is a diagram showing the mapping of the relative bandwidth to the Euler angle (0°, θ, ψ) of LiNbO3 when d / p is infinitely close to 0. Fig.30 The multiple regions R shown with hatching in the figure are regions where a relative bandwidth of 2% or more can be obtained. In addition, when φ among the Euler angles (φ, θ, ψ) is within the range of 0°±5°, the relationship between θ and ψ and the relative bandwidth is as follows: Fig.30 Even in the case where the piezoelectric layer contains lithium tantalate (LiTaO3), the relationship between θ and ψ in the Euler angle (in the range of 0°±5°, θ, ψ) and BW is the same as Fig.30 The relationships shown are the same.

[0209] Therefore, if the Euler angles (φ, θ, ψ) of lithium niobate or lithium tantalate constituting the piezoelectric layer are within the range of 0°±5°, and θ and φ are within the range of Fig.30 If the relative bandwidth is within any of the multiple regions R shown, it is preferable that the relative bandwidth is sufficiently wide.

[0210] Fig.31 It is a front cross-sectional view of an elastic wave device having an acoustic multilayer membrane.

[0211] In the elastic wave device 81, an acoustic multilayer film 82 is stacked on the second main surface 2b of the piezoelectric layer 2. The acoustic multilayer film 82 has a stacked structure of low acoustic impedance layers 82a, 82c, 82e with relatively low acoustic impedance and high acoustic impedance layers 82b, 82d with relatively high acoustic impedance. When the acoustic multilayer film 82 is used, even if the cavity 9 in the elastic wave device 1 is not used, the bulk wave of the thickness shear mode can be confined in the piezoelectric layer 2. In the elastic wave device 81, by setting the above-mentioned d / p to be less than 0.5, the resonance characteristics of the bulk wave based on the thickness shear mode can be obtained. In addition, in the acoustic multilayer film 82, the number of stacked layers of the low acoustic impedance layers 82a, 82c, 82e and the high acoustic impedance layers 82b, 82d is not particularly limited. It is sufficient as long as at least one layer of the high acoustic impedance layer 82b, 82d is arranged farther from the piezoelectric layer 2 than the low acoustic impedance layers 82a, 82c, 82e.

[0212] The low acoustic impedance layers 82a, 82c, 82e and the high acoustic impedance layers 82b, 82d can be made of any suitable material as long as the above-mentioned acoustic impedance relationship is satisfied. For example, silicon oxide or silicon oxynitride can be used as the material of the low acoustic impedance layers 82a, 82c, 82e. In addition, alumina, silicon nitride or metal can be used as the material of the high acoustic impedance layers 82b, 82d.

[0213] Fig.32 This is a partially cutaway perspective view for explaining an elastic wave device using Lamb waves.

[0214] The elastic wave device 91 has a support substrate 92. The support substrate 92 is provided with a recessed portion whose upper surface is open. A piezoelectric layer 93 is stacked on the support substrate 92. Thus, a cavity 9 is formed. An IDT electrode 94 is provided above the cavity 9 and on the piezoelectric layer 93. Reflectors 95 and 96 are provided on both sides of the IDT electrode 94 in the direction of propagation of elastic waves. Fig.32 In the figure, the outer periphery of the cavity 9 is shown by a dotted line. Here, the IDT electrode 94 has a first bus bar 94a, a second bus bar 94b, a plurality of first electrode fingers 94c, and a plurality of second electrode fingers 94d. The plurality of first electrode fingers 94c are connected to the first bus bar 94a. The plurality of second electrode fingers 94d are connected to the second bus bar 94b. The plurality of first electrode fingers 94c and the plurality of second electrode fingers 94d are interlaced with each other.

[0215] In the elastic wave device 91, Lamb waves, which are plate waves, are excited by applying an alternating electric field to the IDT electrode 94 on the cavity 9. Furthermore, since the reflectors 95 and 96 are provided on both sides, resonance characteristics based on the Lamb waves can be obtained.

[0216] As such, the elastic wave resonator in the present invention may also be an elastic wave resonator using plate waves. Fig.32 In the example shown, the Figure 1 The first principal surface 14a of the piezoelectric layer 14 shown in the figure is provided with an IDT electrode 94, a reflector 95, and a reflector 96. On the other hand, in the first acoustic element in the present invention, a pair of comb-shaped electrodes and a plurality of third electrode fingers are provided on the first principal surface 14a. In the case where the first acoustic element of the present invention is an acoustic element using plate waves, it is sufficient that a pair of comb-shaped electrodes and a plurality of third electrode fingers and the above-mentioned reflectors 95 and 96 are provided on the first principal surface 14a of the piezoelectric layer 14 in the first embodiment to the fifth embodiment and each modified example. In this case, it is sufficient that the reflectors 95 and 96 sandwich a pair of comb-shaped electrodes and a plurality of third electrode fingers in the orthogonal direction of the electrode fingers.

[0217] When the second acoustic element of the present invention is an elastic wave resonator having an IDT electrode and utilizing plate waves, for example, the following structure may be used. That is, the first principal surface 14a of the piezoelectric layer 14 in the first embodiment, the second embodiment, the fourth embodiment, and the modified example may be provided with an IDT electrode and the above-mentioned reflectors 95 and 96. In this case, the reflectors 95 and 96 may sandwich the IDT electrode in the direction orthogonal to the electrode fingers.

[0218] Alternatively, when the second acoustic element of the present invention is an acoustic coupling filter using plate waves, it is sufficient to be the same as the first acoustic element described above. That is, it is sufficient to provide a pair of comb-shaped electrodes and a plurality of third electrode fingers and the above-mentioned reflectors 95 and 96 on the first principal surface 14a of the piezoelectric layer 14 in the fifth embodiment and its variants. In this case, it is sufficient to sandwich a pair of comb-shaped electrodes and a plurality of third electrode fingers between the reflectors 95 and 96 in the orthogonal direction of the electrode fingers.

[0219] In the elastic wave devices of the first to fifth embodiments and their respective modifications, for example, an acoustic reflection film may be provided between the support member and the piezoelectric layer as the piezoelectric film. Fig.31 The acoustic multilayer membrane 82 shown. Specifically, the supporting member and the piezoelectric membrane can also be configured so that at least a portion of the supporting member and at least a portion of the piezoelectric membrane are opposed to each other with the acoustic multilayer membrane 82 sandwiched therebetween. In this case, it is sufficient that low acoustic impedance layers and high acoustic impedance layers are alternately stacked in the acoustic multilayer membrane 82. It is also possible that the acoustic multilayer membrane 82 is an acoustic reflection portion in the elastic wave device. Moreover, it is sufficient that the same acoustic multilayer membrane 82 overlaps with the multiple electrode fingers of the first acoustic element and the multiple electrode fingers of the second acoustic element when viewed from above.

[0220] When the sound reflecting portion is the acoustic multilayer film 82, it is preferable that at least one of the low acoustic impedance layer and the high acoustic impedance layer is a dielectric layer. This can reduce parasitic capacitance.

[0221] In the first to fifth embodiments and the first acoustic element in each modification using the body wave in the thickness shear mode, as described above, d / p is preferably 0.5 or less, and more preferably 0.24 or less. Thus, a better resonance characteristic can be obtained. The same is true for the second acoustic element in the first, second, fourth, fifth and modification using the body wave in the thickness shear mode.

[0222] Furthermore, in the excitation region of the first acoustic element in the first to fifth embodiments and various modifications utilizing the body wave in the thickness shear mode, as described above, MR ≤ 1.75 (d / p) + 0.075 is preferably satisfied. More specifically, when the metallization ratio of the first electrode finger and the third electrode finger and the second electrode finger and the third electrode finger relative to the excitation region is set to MR, MR ≤ 1.75 (d / p) + 0.075 is preferably satisfied. In this case, it is possible to more reliably suppress stray noise. The same is true in the excitation region of the second acoustic element in the first, second, fourth, fifth and various modifications utilizing the body wave in the thickness shear mode.

[0223] Description of reference numerals;

[0224] 1: Elastic wave device;

[0225] 2: Piezoelectric layer;

[0226] 2a, 2b: first main surface, second main surface;

[0227] 3, 4: electrodes;

[0228] 5, 6: Bus bar 1, bus bar 2;

[0229] 7: Insulation layer;

[0230] 7a: through hole;

[0231] 8: Supporting member;

[0232] 8a: through hole;

[0233] 9: hollow part;

[0234] 10: Elastic wave device;

[0235] 10a: cavity;

[0236] 10A, 10B: first sound element, second sound element;

[0237] 10C: 1st sound element;

[0238] 11: functional electrode;

[0239] 12: Piezoelectric substrate;

[0240] 13: Supporting member;

[0241] 14: piezoelectric layer;

[0242] 14a, 14b: 1st main surface, 2nd main surface;

[0243] 15: Insulation layer;

[0244] 16: Support base plate;

[0245] 17, 18: the first comb-shaped electrode, the second comb-shaped electrode;

[0246] 19, 19A: the third electrode;

[0247] 22-24: Bus bar 1 to bus bar 3;

[0248] 24A, 24B: first connecting electrode, second connecting electrode;

[0249] 24C: Connect electrodes;

[0250] 24a: stripe;

[0251] 24b: protrusion;

[0252] 25-27: 1st electrode finger to 3rd electrode finger;

[0253] 28A, 28B: first signal potential wiring, second signal potential wiring;

[0254] 28C: Reference potential wiring;

[0255] 28D: Common connection wiring;

[0256] 29: Insulation film;

[0257] 31: IDT electrode;

[0258] 32, 33: Bus No. 4, Bus No. 5;

[0259] 35, 36: the 4th electrode finger and the 5th electrode finger;

[0260] 39: Insulating film;

[0261] 40: Elastic wave device;

[0262] 40A: 1st sound element;

[0263] 50: elastic wave device;

[0264] 50B: 2nd sound element;

[0265] 51: IDT electrode;

[0266] 52, 53: Bus No. 4, Bus No. 5;

[0267] 55, 56: the 4th electrode finger and the 5th electrode finger;

[0268] 60: elastic wave device;

[0269] 60B: 2nd sound element;

[0270] 67, 68: 4th electrode, 5th electrode;

[0271] 70: Elastic wave device;

[0272] 70B, 70D~70H: second acoustic element;

[0273] 72-74: Bus No. 4 to Bus No. 6;

[0274] 75-77: 4th to 6th electrode fingers;

[0275] 80, 81: elastic wave device;

[0276] 82: Acoustic multilayer film;

[0277] 82a, 82c, 82e: low acoustic impedance layer;

[0278] 82b, 82d: high acoustic impedance layer;

[0279] 91: Elastic wave device;

[0280] 92: Support base plate;

[0281] 93: piezoelectric layer;

[0282] 94: IDT electrode;

[0283] 94a, 94b: 1st bus bar, 2nd bus bar;

[0284] 94c, 94d: first electrode finger, second electrode finger;

[0285] 95, 96: reflector;

[0286] 201: piezoelectric film;

[0287] 201a, 201b: 1st main surface, 2nd main surface;

[0288] 451, 452: Area 1, Area 2;

[0289] C: incentive area;

[0290] E: intersection area;

[0291] g1, g2, g4, g5: interval;

[0292] R: region;

[0293] VP1: Imaginary plane.

Claims

1. An elastic wave device, wherein: Equipped with multiple sound elements, The plurality of acoustic elements share a support member and a piezoelectric film, wherein the piezoelectric film is provided on the support member and includes a piezoelectric layer composed of a piezoelectric body. The plurality of acoustic elements include a first acoustic element and a second acoustic element electrically connected to the first acoustic element, the first acoustic element being an acoustic coupling filter, The first sound element comprises: A first comb-shaped electrode, disposed on the piezoelectric layer, connected to the input potential, having a first bus bar and a plurality of first electrode fingers, one end of each of the plurality of first electrode fingers being connected to the first bus bar; A second comb-shaped electrode, disposed on the piezoelectric layer, connected to the output potential, having a second bus bar and a plurality of second electrode fingers, one end of each of the plurality of second electrode fingers being connected to the second bus bar respectively, and interlaced with the plurality of first electrode fingers; as well as a third electrode having a plurality of third electrode fingers and a connecting electrode for connecting adjacent third electrode fingers to each other, and connected to a potential different from that of the first comb-shaped electrode and the second comb-shaped electrode, wherein the plurality of third electrode fingers are respectively arranged on the piezoelectric layer so as to be arranged 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 arranged when viewed from above, When starting from the first electrode finger, the first electrode finger, the second electrode finger, and the third electrode finger are arranged in an order such that the first electrode finger, the third electrode finger, the second electrode finger, and the third electrode finger form one period. The second acoustic element has a functional electrode disposed on the piezoelectric layer. An acoustic reflection portion is formed in the support member at a position overlapping the plurality of first electrode fingers, the plurality of second electrode fingers, and the plurality of third electrode fingers in the first acoustic element and the functional electrode of the second acoustic element in a plan view.

2. The elastic wave device according to claim 1, wherein: The first acoustic element is configured to be able to utilize a thickness shear mode bulk wave.

3. The elastic wave device according to claim 1, wherein: In the first acoustic element, when the longest distance between the centers of the adjacent first electrode finger and the third electrode finger and the longest distance between the centers of the adjacent second electrode finger and the third electrode finger is set to p, and when the thickness of the piezoelectric film is set to d, d / p is less than 0.

5.

4. The elastic wave device according to claim 3, wherein: d / p is less than 0.

24.

5. The elastic wave device according to claim 3 or 4, wherein: In the first acoustic element, when a direction orthogonal to the direction in which the first electrode finger, the second electrode finger, and the third electrode finger extend is set as an electrode finger orthogonal direction, an area where adjacent first electrode fingers and third electrode fingers overlap with each other in the electrode finger orthogonal direction and an area between the centers of adjacent first electrode fingers and third electrode fingers, and an area where adjacent second electrode fingers and third electrode fingers overlap with each other in the electrode finger orthogonal direction and an area between the centers of adjacent second electrode fingers and third electrode fingers are excitation areas, When the metallization ratio of the first electrode finger and the third electrode finger and the second electrode finger and the third electrode finger to the excitation region is MR, the following conditions are satisfied: MR≤1.75(d / p)+0.

075.

6. The elastic wave device according to any one of claims 1 to 5, wherein: The second acoustic element is an acoustic coupling filter, The second acoustic element independently includes a first comb-shaped electrode, a second comb-shaped electrode, and a reference potential electrode from the first acoustic element, the first comb-shaped electrode of the second acoustic element having a first bus bar and a plurality of first electrode fingers, and connected to an input potential, the second comb-shaped electrode of the second acoustic element having a second bus bar and a plurality of second electrode fingers, and connected to an output potential, the reference potential electrode of the second acoustic element having a plurality of third electrode fingers and a connection electrode, and connected to a reference potential, Between the first acoustic element and the second acoustic element, at least any one of the total number of the first electrode finger, the second electrode finger, and the third electrode finger, the center distance between adjacent first electrode fingers and third electrode fingers, the center distance between adjacent second electrode fingers and third electrode fingers, the width of the first electrode finger, the second electrode finger, and the third electrode finger, and the thickness of the first electrode finger, the second electrode finger, and the third electrode finger are different from each other.

7. The elastic wave device according to any one of claims 1 to 6, wherein: The second acoustic element is an acoustic coupling filter, The second acoustic element independently includes a first comb-shaped electrode, a second comb-shaped electrode, and a reference potential electrode from the first acoustic element, the first comb-shaped electrode of the second acoustic element having a first bus bar and a plurality of first electrode fingers, and connected to an input potential, the second comb-shaped electrode of the second acoustic element having a second bus bar and a plurality of second electrode fingers, and connected to an output potential, the reference potential electrode of the second acoustic element having a plurality of third electrode fingers and a connection electrode, and connected to a reference potential, In each of the first acoustic element and the second acoustic element, the front ends of the plurality of first electrode fingers and the plurality of second electrode fingers are spaced apart from each other and are opposed to electrodes connected to a potential different from that of the electrode fingers and being any one of an input potential, an output potential, and a reference potential. In each of the first acoustic element and the second acoustic element, when the direction in which the first electrode finger, the second electrode finger, and the third electrode finger extend is set as the electrode finger extension direction, and the dimension of the interval along the electrode finger extension direction is set as the interval length, the interval lengths are different between the first acoustic element and the second acoustic element.

8. The elastic wave device according to any one of claims 1 to 7, wherein: The second acoustic element is an acoustic coupling filter, The second acoustic element independently includes a first comb-shaped electrode, a second comb-shaped electrode, and a reference potential electrode from the first acoustic element, the first comb-shaped electrode of the second acoustic element having a first bus bar and a plurality of first electrode fingers, and connected to an input potential, the second comb-shaped electrode of the second acoustic element having a second bus bar and a plurality of second electrode fingers, and connected to an output potential, the reference potential electrode of the second acoustic element having a plurality of third electrode fingers and a connection electrode, and connected to a reference potential, In each of the first acoustic element and the second acoustic element, when the direction in which the first electrode finger, the second electrode finger, and the third electrode finger extend is set as the electrode finger extension direction and when observed from a direction orthogonal to the electrode finger extension direction, a region where the first electrode finger and the second electrode finger overlap with each other is a crossing region, In each of the first acoustic element and the second acoustic element, when a dimension of the intersection region along the extending direction of the electrode fingers is defined as an intersection width, the intersection widths are different between the first acoustic element and the second acoustic element.

9. The elastic wave device according to any one of claims 1 to 5, wherein: The second acoustic element is an elastic wave resonator other than an acoustic coupling filter. The functional electrode of the second acoustic element is an IDT electrode.

10. The elastic wave device according to any one of claims 6 to 9, wherein: The second acoustic element is configured to utilize plate waves.

11. The elastic wave device according to any one of claims 6 to 9, wherein: The second acoustic element is configured to be able to utilize a thickness shear mode bulk wave.

12. The elastic wave device according to any one of claims 1 to 5, wherein: The second acoustic element is a capacitive element, The functional electrode of the capacitive element is an IDT electrode.

13. The elastic wave device according to any one of claims 1 to 5, wherein: The second acoustic element is a bulk wave resonator. The piezoelectric film is the piezoelectric layer, and the piezoelectric layer has a first main surface and a second main surface facing each other. The functional electrode of the second acoustic element includes a fourth electrode provided on the first main surface and a fifth electrode provided on the second main surface. The fourth electrode and the fifth electrode face each other with the piezoelectric layer interposed therebetween.

14. The elastic wave device according to any one of claims 1 to 13, wherein: The sound reflecting part is a hollow part, The support member and the piezoelectric film are arranged so that a part of the support member and a part of the piezoelectric film face each other with the cavity portion interposed therebetween.

15. The elastic wave device according to any one of claims 1 to 14, wherein: The acoustic reflection part is an acoustic reflection film including a high acoustic impedance layer with relatively high acoustic impedance and a low acoustic impedance layer with relatively low acoustic impedance. The support member and the piezoelectric film are arranged so that at least a portion of the support member and at least a portion of the piezoelectric film face each other with the acoustic reflective film interposed therebetween.

16. The elastic wave device according to claim 15, wherein: At least one of the low acoustic impedance layer and the high acoustic impedance layer is a dielectric layer.

17. The elastic wave device according to any one of claims 1 to 16, wherein: The piezoelectric layer comprises lithium niobate, The Euler angles (φ, θ, ψ) of lithium niobate constituting the piezoelectric layer are within the range of the following formula (1), formula (2) or formula (3), (within the range of 0°±10°, 0°~25°, arbitrary ψ) …Formula (1) (Within the range of 0°±10°, 25°~100°, 0°~75°[(1-(θ-50) 2 / 2500)] 1 / 2 or 180°-75°[(1-(θ-50) 2 / 2500)] 1 / 2 ~180°) …Formula (2) (0°±10°, 180°-40°[(1-(ψ-90) 2 / 8100)] 1 / 2 ~180°, arbitrary ψ) …Formula (3).

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