Elastic wave device

Abstract

The invention provides an elastic wave device which can promote miniaturization of a filter device and can reduce insertion loss. An elastic wave device according to the present invention is provided with: a piezoelectric film including a piezoelectric layer including lithium niobate; a first comb electrode provided on the piezoelectric layer and having a first bus bar and a plurality of first electrode fingers; a second comb electrode having a second bus bar and a plurality of second electrode fingers interleaved with the plurality of first electrode fingers; and a third electrode having a plurality of third electrode fingers and a connection electrode connecting adjacent third electrode fingers to each other, the third electrode being connected to a potential different from that of the first comb electrode and that of the second comb electrode, the plurality of third electrode fingers being provided on the piezoelectric layer, and the third electrode being connected to a potential different from that of the first comb electrode and that of the second comb electrode. The first electrode fingers and the second electrode fingers are arranged in the direction in which the first electrode fingers and the second electrode fingers are arranged in plan view. The order in which the first electrode fingers, the second electrode fingers, and the third electrode fingers are arranged is an order in which the first electrode fingers, the third electrode fingers, the second electrode fingers, and the third electrode fingers are set as one cycle when starting from the first electrode fingers. In a plan view, a mass addition film is provided in at least a part of at least one of the first gap region (G1) and the second gap region (G2) in a region that is located between the tip of the plurality of first electrode fingers and the second bus bar in the direction in which the electrode fingers extend, does not include the connection electrode, and extends in the direction orthogonal to the electrode fingers.

Description

Technical Field

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

[0002] In the past, elastic wave devices were widely used in filters 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 from each other. 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 elastic wave resonator, which is used in, for example, a ladder filter. In order to obtain good characteristics in the ladder filter, it is necessary to increase the electrostatic capacitance ratio between a 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-type filter, the ladder-type filter tends to be enlarged. In particular, a ladder-type 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 the elastic wave device is used in a filter device, a suitable filter waveform can be obtained without increasing the size of the filter device by setting the structure of the elastic wave device 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 the insertion loss may not be reduced sufficiently even with the above-mentioned structure alone.

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

[0012] Technical solutions to solve problems

[0013] In a broad aspect of the elastic wave device involved in the present invention, it comprises: a piezoelectric film including a piezoelectric layer including lithium niobate; a first comb-shaped electrode arranged on the piezoelectric layer and having a first bus bar and a plurality of first electrode fingers each having one end connected to the first bus bar; a second comb-shaped electrode arranged on the piezoelectric layer and having a second bus bar and a plurality of second electrode fingers each having one end connected to the second bus bar and interlaced with the plurality of first electrode fingers; and a third electrode having a plurality of third electrode fingers and a connecting electrode connecting adjacent third electrode fingers to each other and connected to The third electrode fingers are arranged on the piezoelectric layer so that they are arranged in the direction in which the first electrode fingers and the second electrode fingers are arranged when viewed from above, one of the first comb-shaped electrode and the second comb-shaped electrode is connected to an input potential, and the other of the first comb-shaped electrode and the second comb-shaped electrode is connected to an output potential, and the order in which the first electrode fingers, the second electrode fingers, and the third electrode fingers are arranged is as follows: In the case of starting, the first electrode finger, the third electrode finger, the second electrode finger and the third electrode finger are arranged in a periodic order, the connecting electrode connects the front ends of at least the first bus bar side of the adjacent third electrode fingers to each other, the connecting electrode is at least located between the first bus bar and the front ends of the plurality of second electrode fingers, the direction in which the first electrode finger, the second electrode finger and the third electrode finger extend is set as the electrode finger extending direction, the direction orthogonal to the electrode finger extending direction is set as the electrode finger orthogonal direction, and in a plan view, in the electrode finger extending direction The area located between the front ends of the plurality of second electrode fingers and the connecting electrode and extending in the direction orthogonal to the electrode fingers is the first gap area, and the area located between the connecting electrode and the first bus bar and extending in the direction orthogonal to the electrode fingers is the second gap area. When viewed from above, a mass additional film is provided on at least a portion of at least any one of the area located between the front ends of the plurality of first electrode fingers and the second bus bar in the direction in which the electrode fingers extend and does not include the connecting electrode and extending in the direction orthogonal to the electrode fingers, the first gap area, and the second gap area.

[0014] In another broad aspect of the elastic wave device involved in the present invention, it comprises: a piezoelectric film including a piezoelectric layer including lithium niobate; a first comb-shaped electrode arranged on the piezoelectric layer and having a first bus bar and a plurality of first electrode fingers each having one end connected to the first bus bar; a second comb-shaped electrode arranged on the piezoelectric layer and having a second bus bar and a plurality of second electrode fingers each having one end connected to the second bus bar and interlaced with the plurality of first electrode fingers; and a third electrode having a plurality of third electrode fingers and a connecting electrode connecting adjacent third electrode fingers to each other and connected to the first comb-shaped electrode and the first comb-shaped electrode. The plurality of third electrode fingers are respectively arranged on the piezoelectric layer so that they are arranged in the direction in which the first electrode finger and the second electrode finger are arranged when viewed from above, one of the first comb-shaped electrode and the second comb-shaped electrode is connected to an input potential, and the other of the first comb-shaped electrode and the second comb-shaped electrode is connected to an output potential, and the order in which the first electrode finger, the second electrode finger and the third electrode finger are arranged is, starting from the first electrode finger, the first electrode finger, the third electrode finger, the second electrode finger, and the third electrode finger are arranged in a first order. The electrode fingers and the third electrode fingers are arranged in a periodic sequence, the connecting electrode connects the front ends of at least the first bus bar side of the adjacent third electrode fingers to each other, the connecting electrode is at least located between the first bus bar and the front ends of the plurality of second electrode fingers, the direction in which the first electrode fingers, the second electrode fingers, and the third electrode fingers extend is set as the electrode finger extending direction, the direction orthogonal to the electrode finger extending direction is set as the electrode finger orthogonal direction, and when viewed from above, the area located between the front ends of the plurality of second electrode fingers and the connecting electrode in the electrode finger extending direction and extending in the electrode finger orthogonal direction is the first electrode finger. A gap region, a region located between the connecting electrode and the first bus bar and extending in a direction orthogonal to the electrode fingers is a second gap region, and when viewed from above, a region located between the front ends of the plurality of first electrode fingers and the second bus bar in the extending direction of the electrode fingers and not including the connecting electrode and extending in a direction orthogonal to the electrode fingers, the first gap region and the second gap region, a through hole is provided in the piezoelectric film in at least any one of the regions, which are located between the front ends of the plurality of first electrode fingers and the second bus bar in the extending direction of the electrode fingers and do not include the connecting electrode and extend in a direction orthogonal to the electrode fingers, and when viewed from above, in the region where the through hole is provided, the through hole is located in all portions where the first electrode finger, the second electrode finger and the third electrode finger are not provided.

[0015] Effects of the Invention

[0016] According to the present invention, it is possible to provide an elastic wave device capable of promoting miniaturization of a filter device and reducing insertion loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic front cross-sectional view of the elastic wave device according to the first embodiment of the present invention.

[0018] Figure 2 It is a schematic plan view of the elastic wave device according to the first embodiment of the present invention.

[0019] Figure 3 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 4 It is a diagram showing the transmission characteristics of the elastic wave device according to the first embodiment of the present invention and the first comparative example.

[0021] Figure 5 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.

[0022] Figure 6 It is a schematic plan view of an elastic wave device according to a second embodiment of the present invention.

[0023] Figure 7 It is a diagram showing the transmission characteristics of the elastic wave device according to the second embodiment of the present invention and the first comparative example.

[0024] Figure 8 It is a schematic plan view of an elastic wave device according to a third embodiment of the present invention.

[0025] Fig. 9 It is a diagram showing the transmission characteristics of the elastic wave device according to the third embodiment of the present invention and the first comparative example.

[0026] Fig.10 It is a graph showing the transmission characteristics when the width of the first to fourth gap regions is 1.5 μm in the elastic wave devices according to the fourth embodiment of the present invention and the second comparative example.

[0027] Fig.11 It is a graph showing the transmission characteristics when the width of the first to fourth gap regions is 5 μm in the elastic wave devices according to the fourth embodiment of the present invention and the second comparative example.

[0028] Fig.12 It is a graph showing the transmission characteristics when the width of the first to fourth gap regions is 1.5 μm in the elastic wave devices according to the fifth embodiment of the present invention and the second comparative example.

[0029] Fig.13It is a graph showing the transmission characteristics when the width of the first to fourth gap regions is 5 μm in the elastic wave devices according to the fifth embodiment of the present invention and the second comparative example.

[0030] Fig.14 It is a schematic plan view of an elastic wave device according to a sixth embodiment of the present invention.

[0031] Fig.15 It is a schematic plan view of an elastic wave device according to a seventh embodiment of the present invention.

[0032] Fig.16 It is a schematic plan view of an elastic wave device according to an eighth embodiment of the present invention.

[0033] Fig.17 It is a schematic plan view of an elastic wave device according to a ninth embodiment of the present invention.

[0034] Fig.18 It is a schematic plan view of an elastic wave device according to a tenth embodiment of the present invention.

[0035] Fig.19 It is a schematic plan view of a first elastic wave resonator according to an eleventh embodiment of the present invention.

[0036] Fig. 20 It is a schematic front cross-sectional view showing the vicinity of the first to third electrode fingers in the eleventh embodiment of the present invention.

[0037] Fig.21 It is a schematic plan view of an elastic wave device according to a twelfth embodiment of the present invention.

[0038] Fig. 22 It is a diagram showing the transmission characteristics of the elastic wave device according to the twelfth embodiment of the present invention and the first comparative example.

[0039] Fig.23 It is a schematic plan view of an elastic wave device according to a thirteenth embodiment of the present invention.

[0040] Fig.24 It is a schematic plan view of an elastic wave device according to a fourteenth embodiment of the present invention.

[0041] Fig.25 It is a diagram showing the transmission characteristics of the elastic wave device according to the fourteenth embodiment of the present invention and the first comparative example.

[0042] Fig.26 It is a schematic plan view of an elastic wave device according to a fifteenth embodiment of the present invention.

[0043] Fig. 27(a) is a schematic perspective view showing the appearance of an elastic wave device using a thickness shear mode bulk wave, Fig. 27 (b) is a top view showing the electrode structure on the piezoelectric layer.

[0044] Fig.28 yes Fig. 27 (a) is a cross-sectional view of the portion along line AA.

[0045] Fig.29 (a) is a schematic front cross-sectional view for explaining Lamb waves propagating through a piezoelectric film of an elastic wave device. Fig.29 (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.

[0046] Fig.30 It is a diagram showing the amplitude direction of the body wave in the thickness shear mode.

[0047] Fig.31 FIG. 1 is a diagram showing the resonance characteristics of an elastic wave device using bulk waves in a thickness shear mode.

[0048] Fig.32 : This 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 set to p and the thickness of the piezoelectric layer is set to d.

[0049] Fig.33 This is a top view of an elastic wave device using bulk waves in a thickness shear mode.

[0050] Fig.34 FIG. 2 is a diagram showing the resonance characteristics of an elastic wave device according to a reference example in which spurious emission occurs.

[0051] Fig.35 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.

[0052] Fig.36 It is a graph showing the relationship between d / 2p and the metallization ratio MR.

[0053] Fig.37 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.

[0054] Fig.38 It is a front cross-sectional view of an elastic wave device having an acoustic multilayer membrane.

[0055] Fig.39 This is a partially cutaway perspective view for explaining an elastic wave device using Lamb waves. DETAILED DESCRIPTION

[0056] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings to clarify the present invention.

[0057] In addition, it should be noted that each embodiment described in this specification is an example, and some structures can be replaced or combined among different embodiments.

[0058] Figure 1 It is a schematic front cross-sectional view of the elastic wave device according to the first embodiment of the present invention. Figure 2 is a schematic plan view of the elastic wave device according to the first embodiment. Figure 1 : is a schematic front cross-sectional view of the central region F of the intersection region E described later. Figure 2 In FIG. 1 , each electrode is shown with hatching. Figure 2 Similarly, in other schematic plan views, electrodes may be hatched.

[0059] Figure 1 The elastic wave device 10 shown is configured to utilize the thickness shear mode. The elastic wave device 10 is an acoustic coupling filter. The structure of the elastic wave device 10 will be described below.

[0060] The elastic wave device 10 has a piezoelectric substrate 12 and a functional electrode 11. The piezoelectric substrate 12 is a substrate having piezoelectricity. Specifically, the piezoelectric substrate 12 has a supporting member 13 and a piezoelectric layer 14 as a piezoelectric film. The piezoelectric layer 14 is a layer including 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 including a piezoelectric body. However, in this embodiment, the piezoelectric film is a single-layer piezoelectric layer 14, and is a film including a piezoelectric body. In addition, in the present invention, the piezoelectric film may also be a stacked film including the piezoelectric layer 14. 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. In addition, the supporting member 13 may not necessarily be provided.

[0061] The piezoelectric layer 14 has a first principal surface 14 a and a second principal surface 14 b. The first principal surface 14 a and the second principal surface 14 b face each other. Of the first principal surface 14 a and the second principal surface 14 b, the second principal surface 14 b is located on the support member 13 side.

[0062] The piezoelectric layer 14 includes lithium niobate. More specifically, in the present embodiment, the lithium niobate used for the piezoelectric layer 14 is Z-cut LiNbO3. The Euler angles (φ, θ, ψ) of the LiNbO3 are (0°, 0°, 90°). However, the Euler angles (φ, θ, ψ) of the piezoelectric layer 14 are not limited to the above. In addition, in the present specification, a certain component includes a certain material, including a case where the electrical characteristics of the elastic wave device are not significantly degraded by a trace amount of impurities.

[0063] The functional electrode 11 is provided on the first main surface 14a of the piezoelectric layer 14. Figure 2 As 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 addition, the third electrode 19 may not necessarily 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.

[0064] In addition, the first comb-shaped electrode 17 may be connected to the output potential. The second comb-shaped electrode 18 may be connected to the input potential. In this way, the first comb-shaped electrode 17 only needs to be connected to one of the input potential and the output potential. The second comb-shaped electrode 18 only needs to be connected to the other of the input potential and the output potential.

[0065] 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.

[0066] 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.

[0067] The third electrode 19 has a zigzag shape. Specifically, the third electrode 19 has a plurality of connection electrodes 24 and a plurality of third electrode fingers 27. The plurality of connection electrodes 24 and the plurality of third electrode fingers 27 are provided on the first principal surface 14a of the piezoelectric layer 14. Adjacent third electrode fingers 27 are connected to each other via the connection electrodes 24. By repeating this structure, the shape of the third electrode 19 becomes a zigzag shape.

[0068] In more detail, the front ends of two adjacent third electrode fingers 27 on the first bus bar 22 side or the front ends on the second bus bar 23 side are connected to each other through the connection electrode 24. 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 24 at both ends of the front end on the first bus bar 22 side and the front end 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 24. By repeating this structure, the shape of the third electrode 19 becomes a zigzag shape.

[0069] In the present invention, the connection electrode 24 only needs to be located at least on the side of the first bus bar 22. The connection electrode 24 only needs to electrically connect the plurality of third electrode fingers 27 to each other.

[0070] like Figure 2 As shown, 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 26. The plurality of third electrode fingers 27 are respectively arranged to be arranged with the first electrode fingers 25 and the second electrode fingers 26 in the direction in which the first electrode fingers 25 and the second electrode fingers 26 are arranged. Therefore, the first electrode fingers 25, the second electrode fingers 26, and the third electrode fingers 27 are arranged in one direction.

[0071] 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 the electrode finger.

[0072] Figure 3 This is a schematic front cross-sectional view showing the vicinity of first to third electrode fingers in the first embodiment.

[0073] Regarding the order in which the plurality of electrode fingers are arranged, when starting from the first electrode finger 25, the order is such that the first electrode finger 25, the third electrode finger 27, the second electrode finger 26, and the third electrode finger 27 constitute 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 such that it is continuous like IN, GND, OUT, GND, IN, GND, OUT, ...

[0074] 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.

[0075] In this embodiment, in the functional electrode 11, the center distances between adjacent pairs of first electrode fingers 25 and third electrode fingers 27 and the center distances between adjacent pairs of second electrode fingers 26 and third electrode fingers 27 are the same. However, the center distances between adjacent electrode fingers may not be constant.

[0076] Each electrode finger of the functional electrode 11 includes a stacked metal film. Specifically, in each electrode finger, a Ti layer, an AlCu layer, and a Ti layer are stacked in order from the piezoelectric layer 14 side. In addition, the material of each electrode finger is not limited to the above. Alternatively, each electrode finger may also include a single-layer metal film.

[0077] In the present embodiment, the front ends of the plurality of second electrode fingers 26 are respectively opposed to the connection electrode 24 on the side of the first bus bar 22 with gaps therebetween in the electrode finger extension direction. In a plan view, a region located between the front ends of the plurality of second electrode fingers 26 and the connection electrode 24 in the electrode finger extension direction and extending in a direction orthogonal to the electrode fingers is the first gap region G1.

[0078] The connection electrode 24 on the first bus bar 22 side faces the first bus bar 22 with a gap in the electrode finger extending direction. In a plan view, a region located between the connection electrode 24 and the first bus bar 22 and extending in the electrode finger orthogonal direction is a second gap region G2.

[0079] The front ends of the plurality of first electrode fingers 25 are respectively opposed to the connection electrode 24 on the second bus bar 23 side with gaps in the electrode finger extension direction. When viewed from above, the region between the front ends of the plurality of first electrode fingers 25 and the connection electrode 24 on the second bus bar 23 side in the electrode finger extension direction and extending in the direction orthogonal to the electrode fingers is the third gap region G3.

[0080] The connection electrode 24 on the second bus bar 23 side is opposite to the second bus bar 23 with a gap in the electrode finger extension direction. In a plan view, the region between the connection electrode 24 and the second bus bar 23 and extending in the electrode finger orthogonal direction is the fourth gap region G4. Hereinafter, the first gap region G1, the second gap region G2, the third gap region G3, and the fourth gap region G4 are sometimes collectively described as simply a gap region.

[0081] The elastic wave device 10 is an elastic wave resonator configured to utilize bulk waves in a thickness shear mode. Figure 2 As shown, the elastic wave device 10 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 2 In FIG. 1 , only two excitation regions C among multiple excitation regions C are shown.

[0082] 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 orthogonal direction of 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 orthogonal direction of 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 orthogonal direction of the electrode fingers.

[0083] In the functional electrode 11, the structure other than the third electrode 19 is the same as the structure of the IDT (Interdigital Transducer) 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.

[0084] The intersection region E includes a central region F and a pair of edge regions. Specifically, the pair of edge regions are a first edge region H1 and a second edge region H2. The first edge region H1 and the second edge region H2 are arranged to sandwich the central region F in the extension direction of the electrode fingers and to face each other. The first edge region H1 is located on the first bus bar 22 side. The second edge region H2 is located on the second bus bar 23 side. The first edge region H1 is adjacent to the first gap region G1. The second edge region H2 is adjacent to the third gap region G3.

[0085] The plurality of third electrode fingers 27 extend to the outside of the intersection region E. Specifically, a portion of the plurality of third electrode fingers 27 is located in the first gap region G1 and the third gap region G3 .

[0086] The elastic wave device 10 includes a pair of mass addition films 28A and 28B. The mass addition film 28A is provided across the first gap region G1 and the first edge region H1. The mass addition film 28B is provided across the third gap region G3 and the second edge region H2. The mass addition film 28A and the mass addition film 28B are not provided in the central region F.

[0087] The mass addition film 28A has a strip shape. Specifically, the mass addition film 28A is provided in the first edge region H1 across the first principal surface 14a of the piezoelectric layer 14, the plurality of first electrode fingers 25, the plurality of second electrode fingers 26, and the plurality of third electrode fingers 27. The mass addition film 28A is provided in the first gap region G1 across the first principal surface 14a, the plurality of first electrode fingers 25, and the plurality of third electrode fingers 27. The mass addition film 28A is provided continuously to overlap the plurality of electrode fingers and the region between the electrode fingers in a plan view.

[0088] In this specification, the term "top view" refers to a view from the Figure 1 The upper direction in the diagram is observed along the stacking direction of the support member 13 and the piezoelectric film. Figure 1 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, it is assumed that the top view is synonymous with the observation from the main surface opposite direction. The so-called main surface opposite direction is the direction in which the first main surface 14a and the second main surface 14b of the piezoelectric layer 14 are opposite to each other. More specifically, the main surface opposite direction is, for example, the normal direction of the first main surface 14a.

[0089] The mass adding film 28B is provided across the first main surface 14a of the piezoelectric layer 14 and the plurality of electrode fingers in the second edge region H2 and the third gap region G3. The mass adding film 28B is provided continuously to overlap the plurality of electrode fingers and the region between the electrode fingers in a plan view.

[0090] Silicon oxide can be used as a material of the mass adding film 28A and the mass adding film 28B. However, the material of the mass adding film 28A and the mass adding film 28B is not limited to the above.

[0091] This embodiment is characterized by the following structures: 1) The third electrode fingers 27 of the third electrode 19 are provided between the first electrode fingers 25 of the first comb-shaped electrode 17 and the second electrode fingers 26 of the second comb-shaped electrode 18 in a plan view. 2) The mass addition film 28A and the mass addition film 28B are provided in the first gap region G1 and the third gap region G3.

[0092] In addition, the mass added film only needs to be provided in at least a portion of at least any one of the first gap region G1, the second gap region G2, the third gap region G3, and the fourth gap region G4. In the present embodiment, by having the above-mentioned structure, when the elastic wave device 10 is used in a filter device, the miniaturization of the filter device can be promoted and the insertion loss can be reduced. The following will show the details of the effect by comparing the present embodiment with the first comparative example.

[0093] The first comparative example is different from the first embodiment in that no mass addition film is provided. In the first comparative example, the piezoelectric layer includes Z-cut lithium niobate. The first embodiment and the first comparative example are compared in terms of pass characteristics. The design parameters of the elastic wave device 10 having the structure of the first embodiment are as follows.

[0094] Piezoelectric layer: material is LiNbO3, Euler angles (φ, θ, ψ) are (0°, 0°, 90°), thickness is 400nm

[0095] The first to third electrode fingers: the layer structure is Ti layer / AlCu layer / Ti layer from the piezoelectric layer side, and the thickness of each layer is 10nm / 390nm / 4nm from the piezoelectric layer side

[0096] The order of the first electrode finger to the third electrode finger is in the order indicated by the potentials to which they are connected: IN, GND, OUT, GND are repeated in this order.

[0097] The center-to-center distance between adjacent electrode fingers: 1.4 μm

[0098] Duty cycle: 0.3

[0099] The size of the first edge region and the second edge region along the electrode finger extension direction: 1 μm

[0100] Thickness of mass added film: 25nm

[0101] In the first comparative example, the same design parameters as those of the first embodiment were used except that the mass adding film was not provided.

[0102] Figure 4 Graphs showing the transmission characteristics of the elastic wave devices according to the first embodiment and the first comparative example. Figure 4 In the figure, the S21 passing characteristic is shown. Figure 4 The same is true for other diagrams showing the transmission characteristics.

[0103] First, if Figure 4 As shown in FIG. 1 , it can be seen that in the elastic wave device 10 according to the first embodiment, a filter waveform can be appropriately obtained. The elastic wave device 10 is an acoustic coupling filter. In more detail, Figure 2 As shown, the elastic wave device 10 includes 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. In these excitation regions C, elastic waves of multiple modes including a thickness shear mode bulk wave can be excited. By coupling these modes, a filter waveform can be appropriately obtained even in one elastic wave device 10.

[0104] 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.

[0105] In addition, if Figure 4 As shown, it can be seen that in the first embodiment, the loss near the center of the passband is smaller than in the first comparative example. Therefore, when the elastic wave device 10 is used in a filter device, the insertion loss can be reduced.

[0106] Hereinafter, the structure of the first embodiment will be described in more detail.

[0107] In the first embodiment, the mass addition film 28A is provided on a portion of the first gap region G1 in the direction in which the electrode fingers extend. The mass addition film 28A is provided on the entire first gap region G1 in the direction orthogonal to the electrode fingers.

[0108] The mass addition film 28B is provided on a portion of the third gap region G3 in the direction in which the electrode fingers extend. The mass addition film 28B is provided on the entire third gap region G3 in the direction orthogonal to the electrode fingers.

[0109] However, as described above, the mass-added film only needs to be provided in at least a portion of at least any one of the first gap region G1, the second gap region G2, the third gap region G3, and the fourth gap region. For example, the mass-added film 28A only needs to be provided in at least a portion of the first gap region G1 in the direction in which the electrode fingers extend and in at least a portion in the direction orthogonal to the electrode fingers. Alternatively, for example, only the mass-added film 28A may be provided between the mass-added film 28A and the mass-added film 28B.

[0110] In the first embodiment, the mass adding film 28A is provided in the entire first edge region H1 , and the mass adding film 28B is provided in the entire second edge region H2 .

[0111] like Figure 1 As shown, the support member 13 includes a support substrate 16 and an insulating layer 15. The piezoelectric substrate 12 is a stack of the support substrate 16, the insulating layer 15, and the piezoelectric layer 14. That is, when viewed from a direction in which the first principal surface 14a and the second principal surface 14b of the piezoelectric layer 14 are opposite, the piezoelectric layer 14 and the support member 13 overlap.

[0112] As a material of the support substrate 16 , for example, a semiconductor such as silicon, a ceramic such as aluminum oxide, etc. can be used. As a material of the insulating layer 15 , an appropriate dielectric such as silicon oxide or tantalum oxide can be used.

[0113] 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 first 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 across 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.

[0114] The cavity 10a is the acoustic reflection portion in the present invention. The acoustic reflection portion can effectively confine the energy of the elastic wave on the piezoelectric layer 14 side. In a plan view, the acoustic reflection portion only needs to be arranged at a position overlapping with at least a portion of the functional electrode 11 in the support member 13. More specifically, in a plan view, at least a portion of each of the first electrode finger 25, the second electrode finger 26, and the third electrode finger 27 overlaps with the acoustic reflection portion. Preferably, in a plan view, a plurality of excitation regions C overlap with the acoustic reflection portion.

[0115] 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.

[0116] like Figure 2 As shown, in the first embodiment, in the portion where the mass-added film 28A and the electrode fingers are stacked, the electrode fingers and the mass-added film 28A are stacked in order from the piezoelectric layer 14 side. However, in the portion where the mass-added film 28A and the electrode fingers are stacked, the mass-added film 28A and the electrode fingers are stacked in order from the piezoelectric layer 14 side. The same is true for the portion where the mass-added film 28B and the electrode fingers are stacked.

[0117] As described above, the material of mass-added film 28A and mass-added film 28B is not limited to silicon oxide. However, as the material of mass-added film 28A and mass-added film 28B, at least one dielectric selected from the group consisting of silicon oxide, tungsten oxide, niobium oxide, tantalum oxide, and hafnium oxide is preferably used. Thus, when elastic wave device 10 is used in a filter device, insertion loss can be reduced more reliably.

[0118] In the functional electrode 11, the center-to-center distance between adjacent electrode fingers is fixed. In addition, the center-to-center distance between adjacent electrode fingers may not be fixed. In this case, the longest distance between 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 is set to p. However, when the center-to-center distance between adjacent electrode fingers is fixed as in the first embodiment, the center-to-center distance between any adjacent electrode fingers is the distance p.

[0119] 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 appropriate excitation of thickness shear mode bulk waves. In this embodiment, the thickness d is the thickness of the piezoelectric layer 14 .

[0120] In addition, the elastic wave device of the present invention does not necessarily have to be configured to utilize body waves in the thickness shear mode. The elastic wave device of the present invention may also be configured to utilize plate waves. In this case, the excitation region is Figure 2 The intersection area E is shown.

[0121] In the first embodiment, the piezoelectric layer 14 includes Z-cut LiNbO3. However, the piezoelectric layer 14 may also include rotated Y-cut lithium niobate. In this case, the relative bandwidth of the elastic wave device 10 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 antiresonant frequency is fa.

[0122] The relationship between the relative bandwidth of elastic wave device 10 and the Euler angles (φ, θ, ψ) of 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°.

[0123] Figure 5 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.

[0124] Figure 5 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 5 The relationships shown are the same.

[0125] (within the range of 0°±10°, 0°~25°, arbitrary ψ) …Formula (1)

[0126] (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)

[0127] (0°±10°, 180°-40°[(1-(ψ-90) 2 / 8100)] 1 / 2 ~180°, any ψ) …Formula (3)

[0128] 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 to be suitably used in a filter device.

[0129] The second to fifth embodiments are shown below. The second to fifth embodiments differ from the first embodiment in at least one of the positions of the mass addition films 28A and 28B and the material of the piezoelectric layer 14. Specifically, in the second and third embodiments, the piezoelectric layer 14 includes Z-cut lithium niobate, but in the fourth and fifth embodiments, the piezoelectric layer 14 includes rotated Y-cut lithium niobate. Except for the above-mentioned points, the elastic wave devices of the second to fifth embodiments have the same structure as the first embodiment.

[0130] In the second to fifth embodiments, the mass added film 28A and the mass added film 28B are provided in any gap region. Therefore, in the second to fifth embodiments, when the elastic wave device is used for the filter device, the filter device can be miniaturized and the insertion loss can be reduced, as in the first embodiment.

[0131] In the second to fifth embodiments, in the gap region where the mass additional film 28A is provided, the mass additional film 28A is provided over the entire gap region in the direction orthogonal to the electrode fingers. Similarly, in the gap region where the mass additional film 28B is provided, the mass additional film 28B is provided over the entire gap region in the direction orthogonal to the electrode fingers.

[0132] Figure 6 It is a schematic plan view of an elastic wave device according to a second embodiment.

[0133] The present embodiment is different from the first embodiment in that the mass addition film 28A is provided across the first edge region H1, the first gap region G1, and the second gap region G2. The present embodiment is also different from the first embodiment in that the mass addition film 28B is provided across the second edge region H2, the third gap region G3, and the fourth gap region G4.

[0134] The mass adding film 28A is continuously provided from the first edge region H1 to the second gap region G2 in the electrode finger extending direction. Therefore, the mass adding film 28A overlaps with the connection electrode 24 on the first bus bar 22 side in a plan view. The mass adding film 28A is provided in the entire first gap region G1 and the second gap region G2 in the electrode finger extending direction.

[0135] The mass addition film 28B is continuously provided in the electrode finger extension direction from the second edge region H2 to the fourth gap region G4. Therefore, the mass addition film 28B overlaps with the connection electrode 24 on the second bus bar 23 side in a plan view. The mass addition film 28B is provided in the entirety of the third gap region G3 and the fourth gap region G4 in the electrode finger extension direction.

[0136] The second embodiment and the first comparative example compare the pass characteristics. The design parameters of the elastic wave device having the structure of the second embodiment are as follows. Figure 4 The design parameters in the first embodiment related to the comparison shown are the same.

[0137] Piezoelectric layer: material is LiNbO3, Euler angles (φ, θ, ψ) are (0°, 0°, 90°), thickness is 400nm

[0138] The first to third electrode fingers: the layer structure is Ti layer / AlCu layer / Ti layer from the piezoelectric layer side, and the thickness of each layer is 10nm / 390nm / 4nm from the piezoelectric layer side

[0139] The order of the first electrode finger to the third electrode finger is in the order indicated by the potentials to which they are connected: IN, GND, OUT, GND are repeated in this order.

[0140] The center-to-center distance between adjacent electrode fingers: 1.4 μm

[0141] Duty cycle: 0.3

[0142] The size of the first edge region and the second edge region along the electrode finger extension direction: 1 μm

[0143] Thickness of mass added film: 25nm

[0144] Figure 7 It is a diagram showing the transmission characteristics of the elastic wave devices according to the second embodiment and the first comparative example.

[0145] like Figure 7 As shown, it can be seen that in the second embodiment, the loss is smaller near the center of the passband and on the low-frequency side than in the first comparative example.

[0146] Figure 8 It is a schematic plan view of an elastic wave device according to a third embodiment.

[0147] The present embodiment is different from the first embodiment in that the mass addition film 28A is not provided in the first edge region H1, and is provided across the first gap region G1 and the second gap region G2. The present embodiment is also different from the first embodiment in that the mass addition film 28B is not provided in the second edge region H2, and is provided across the third gap region G3 and the fourth gap region G4.

[0148] The mass adding film 28A is continuously provided from the first gap region G1 to the second gap region G2 in the electrode finger extending direction. Therefore, the mass adding film 28A overlaps with the connection electrode 24 on the first bus bar 22 side in a plan view. The mass adding film 28A is provided in the entire first gap region G1 and the second gap region G2 in the electrode finger extending direction.

[0149] The mass adding film 28B is continuously provided from the third gap region G3 to the fourth gap region G4 in the electrode finger extending direction. Therefore, the mass adding film 28B overlaps with the connecting electrode 24 on the second bus bar 23 side in a plan view. The mass adding film 28B is provided in the entire third gap region G3 and the fourth gap region G4 in the electrode finger extending direction.

[0150] The third embodiment and the first comparative example compare the transmission characteristics. Figure 4 The design parameters in the first embodiment related to the comparison shown are the same.

[0151] Fig. 9 It is a diagram showing the transmission characteristics of the elastic wave devices according to the third embodiment and the first comparative example.

[0152] like Fig. 9 As shown, it can be seen that in the third embodiment, the loss is smaller near the center of the passband and on the low-frequency side than in the first comparative example.

[0153] Next, the fourth embodiment will be described. In the fourth embodiment, the position of the mass addition film is Figure 2 The fourth embodiment is different from the first embodiment in that the piezoelectric layer includes rotated Y-cut lithium niobate.

[0154] The fourth embodiment and the second comparative example compare the transmission characteristics. The second comparative example differs from the fourth embodiment in that no mass-added film is provided. In the second comparative example, the piezoelectric layer includes rotated Y-cut lithium niobate.

[0155] In addition, in this comparison, the widths of the first to fourth gap regions are set to two types. The width of the gap region is the dimension of the gap region along the extension direction of the electrode fingers. In one comparison, the widths of the first to fourth gap regions are set to 1.5 μm. In another comparison, the widths of the first to fourth gap regions are set to 5 μm. The design parameters of the elastic wave device having the structure of the fourth embodiment are as follows.

[0156] Piezoelectric layer: Material is LiNbO3, Euler angles (φ, θ, ψ) are (0°, 217.5°, 0°), thickness is 400nm

[0157] The first to third electrode fingers: the layer structure is Ti layer / AlCu layer / Ti layer from the piezoelectric layer side, and the thickness of each layer is 10nm / 390nm / 4nm from the piezoelectric layer side

[0158] The order of the first electrode finger to the third electrode finger is in the order indicated by the potentials to which they are connected: IN, GND, OUT, GND are repeated in this order.

[0159] The center-to-center distance between adjacent electrode fingers: 1.4 μm

[0160] Duty cycle: 0.3

[0161] The size of the first edge region and the second edge region along the electrode finger extension direction: 1 μm

[0162] Width of the 1st to 4th gap regions: 1.5 μm or 5 μm

[0163] Thickness of mass added film: 25nm

[0164] In the second comparative example, the same design parameters as those of the fourth embodiment were used except that the mass adding film was not provided.

[0165] Fig.10 It is a graph showing the transmission characteristics when the width of the first to fourth gap regions in the elastic wave devices according to the fourth embodiment and the second comparative example is 1.5 μm. Fig.11 It is a graph showing the transmission characteristics when the width of the first to fourth gap regions is 5 μm in the elastic wave devices according to the fourth embodiment and the second comparative example.

[0166] like Fig.10 As shown, when the width of the first to fourth gap regions is 1.5 μm, in the fourth embodiment, the loss can be reduced on the high-frequency side and the low-frequency side of the passband compared to the second comparative example.

[0167] like Fig.11 As shown in FIG. 1 , when the width of the first to fourth gap regions is 5 μm, a large ripple is generated in the passband in the pass characteristics of the second comparative example. In contrast, in the pass characteristics of the fourth embodiment, the ripple in the passband is smaller than that in the second comparative example. Therefore, in the fourth embodiment, the loss can be reduced.

[0168] However, comparison Fig.10 and Fig.11 It can be seen that when the piezoelectric layer includes rotated Y-cut lithium niobate, the ripple in the passband can be further suppressed because the widths of the first to fourth gap regions are narrow.

[0169] Next, the fifth embodiment will be described. In the fifth embodiment, the position of the mass addition film is Figure 6 The fifth embodiment is different from the second embodiment in that the piezoelectric layer includes rotated Y-cut lithium niobate.

[0170] In the fifth embodiment and the second comparative example, the pass characteristics are compared. In this comparison, the widths of the first to fourth gap regions are set to two types. In one comparison, the widths of the first to fourth gap regions are set to 1.5 μm. In the other comparison, the widths of the first to fourth gap regions are set to 5 μm. The design parameters of the elastic wave device having the structure of the fifth embodiment are compared with those of the second comparative example. Fig.10 as well as Fig.11 The design parameters in the fourth embodiment related to the comparison shown are the same.

[0171] Fig.12 It is a graph showing the transmission characteristics when the width of the first to fourth gap regions in the elastic wave devices according to the fifth embodiment and the second comparative example is 1.5 μm. Fig.13 It is a graph showing the transmission characteristics when the width of the first to fourth gap regions in the elastic wave devices according to the fifth embodiment and the second comparative example is 5 μm.

[0172] like Fig.12 As shown, in the fifth embodiment, when the width of the first to fourth gap regions is 1.5 μm, the loss can be reduced on the high-frequency side and the low-frequency side of the passband compared to the second comparative example.

[0173] like Fig.13 As shown in FIG. 1 , when the width of the first to fourth gap regions is 5 μm, a large ripple is generated in the passband in the pass characteristics of the second comparative example. In contrast, in the pass characteristics of the fifth embodiment, the ripple in the passband becomes smaller than the ripple in the second comparative example. Therefore, in the fifth embodiment, the loss can be reduced.

[0174] However, comparison Fig.12 and Fig.13 It can be seen that when the piezoelectric layer includes rotated Y-cut lithium niobate, the ripple in the passband can be further suppressed because the widths of the first to fourth gap regions are narrow.

[0175] In the first to fifth embodiments, for example, Figure 2As shown, the third electrode 19 has a zigzag shape. A portion of the plurality of connection electrodes 24 in the third electrode 19 is disposed between the front ends of the plurality of second electrode fingers 26 and the first bus bar 22. The remaining plurality of connection electrodes 24 are disposed between the front ends of the plurality of first electrode fingers 25 and the second bus bar 23.

[0176] However, the third electrode 19 may not have a zigzag shape. The connection electrode 24 only needs to be provided at least between the front ends of the plurality of second electrode fingers 26 and the first bus bar 22. In addition, when the connection electrode 24 is not provided between the front ends of the plurality of first electrode fingers 25 and the second bus bar 23, the third gap region G3 and the fourth gap region G3 are not formed. The sixth embodiment shows an example in which the third electrode 19 does not have a zigzag shape.

[0177] Fig.14 It is a schematic plan view of an elastic wave device according to the sixth embodiment.

[0178] This embodiment differs from the first embodiment in the structure of the third electrode 39. This embodiment also differs from the first embodiment in that the third gap region G3 and the fourth gap region G4 are not formed, but the fifth gap region G5 is formed. Therefore, this embodiment also differs from the first embodiment in the position of the mass addition film. Except for the above-mentioned points, the elastic wave device of this embodiment has the same structure as the elastic wave device 10 of the first embodiment.

[0179] In the third electrode 39, the connection electrode is the third bus bar 34. The third bus bar 34 as the connection electrode of the third electrode 39 electrically connects the plurality of third electrode fingers 27 to each other. Specifically, the third bus bar 34 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 34 and the plurality of first electrode fingers 25 are electrically insulated from each other by the insulating film 37.

[0180] More specifically, the third bus bar 34 includes a plurality of first connection electrodes 34A and a second connection electrode 34B. Each first connection electrode 34A 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 34A and the two third electrode fingers 27. The second connection electrode 34B connects the plurality of first connection electrodes 34A to each other. An insulating film 37 is provided between the second connection electrode 34B and the plurality of first electrode fingers 25.

[0181] More specifically, the insulating film 37 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 37 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 37 has a strip shape.

[0182] The insulating film 37 does not reach the first connection electrode 34A of the third electrode 39. Moreover, the second connection electrode 34B is provided across the insulating film 37 and the plurality of first connection electrodes 34A. More specifically, the second connection electrode 34B has a stripe 34a and a plurality of protrusions 34b. Each protrusion 34b extends from the stripe 34a toward each first connection electrode 34A. Each protrusion 34b is connected to each first connection electrode 34A. Thus, the plurality of third electrode fingers 27 are electrically connected to each other through the first connection electrode 34A and the second connection electrode 34B.

[0183] In the present embodiment, the third bus bar 34 is located in a region between the first bus bar 22 and the front ends of the plurality of second electrode fingers 26. Therefore, the front ends of the plurality of second electrode fingers 26 are opposed to the third bus bar 34 with gaps in the electrode finger extending direction. On the other hand, the front ends of the plurality of first electrode fingers 25 are opposed to the second bus bar 23 with gaps in the electrode finger extending direction.

[0184] In a plan view, a region located between the tips of the plurality of first electrode fingers 25 and the second bus bar 23 in the electrode finger extending direction and extending in the electrode finger orthogonal direction is the fifth gap region G5. The fifth gap region G5 is adjacent to the second edge region H2.

[0185] In addition, the first gap region G1 and the second gap region G2 are configured in the same manner as in the first embodiment. Specifically, in a plan view, the region located between the front ends of the plurality of second electrode fingers 26 and the third bus bar 34 as the connection electrode in the electrode finger extension direction and extending in the direction orthogonal to the electrode fingers is the first gap region G1. In a plan view, the region located between the third bus bar 34 and the first bus bar 22 and extending in the direction orthogonal to the electrode fingers is the second gap region G2. In the following, the fifth gap region G5 and other gap regions are sometimes included and recorded only as gap regions.

[0186] The fifth gap region G5 and Figure 2 The third gap region G3 and the fourth gap region G4 shown coincide with each other in the following points: These regions are located between the tips of the plurality of first electrode fingers 25 and the second bus bar 23 , do not include the connection electrodes, and extend in the direction orthogonal to the electrode fingers.

[0187] like Fig.14As shown, the mass adding film 28A is provided across the first gap region G1 and the first edge region H1 , and the mass adding film 28B is provided across the fifth gap region G5 and the second edge region H2 .

[0188] The present embodiment is characterized in that it has the following structures: 1) the third electrode fingers 27 of the third electrode 19 are provided between the first electrode fingers 25 of the first comb-shaped electrode 17 and the second electrode fingers 26 of the second comb-shaped electrode 18 in a plan view. 2) the mass addition film 28A and the mass addition film 28B are provided in the first gap region G1 and the fifth gap region G5.

[0189] In addition, the mass added film only needs to be provided in at least a portion of at least any one of the first gap region G1, the second gap region G2, and the fifth gap region G5. In the present embodiment, by having the above-mentioned structure, when the elastic wave device is used in the filter device, the miniaturization of the filter device can be promoted and the insertion loss can be reduced.

[0190] In the first to sixth embodiments, the mass addition film 28A and the mass addition film 28B have a strip shape. When viewed from the electrode finger extension direction, the mass addition film 28A and the mass addition film 28B overlap with the plurality of first electrode fingers 25, the plurality of second electrode fingers 26, and the plurality of third electrode fingers 27, respectively. However, the shape of the mass addition film is not limited to a strip shape. The seventh to tenth embodiments show examples in which the shape of the mass addition film is not a strip shape.

[0191] The seventh and eighth embodiments differ from the first embodiment only in the position of the mass addition film. However, in the seventh and eighth embodiments, the mass addition film is provided in at least a portion of at least any one of the first gap region G1, the second gap region G2, the third gap region G3, and the fourth gap region G4.

[0192] The 9th and 10th embodiments differ from the 6th embodiment only in the position of the mass addition film. However, in the 9th and 10th embodiments, the mass addition film is provided in at least a portion of at least any one of the first gap region G1, the second gap region G2, and the fifth gap region G5. In the 7th to 10th embodiments, similarly to the 1st or 6th embodiments, when the elastic wave device is used for the filter device, the filter device can be miniaturized and the insertion loss can be reduced.

[0193] Fig.15 It is a schematic plan view of an elastic wave device according to the seventh embodiment.

[0194] This embodiment is different from the first embodiment in the positions of the mass addition film 48A and the mass addition film 48B. Except for the above-mentioned points, the elastic wave device of this embodiment has the same structure as the elastic wave device 10 of the first embodiment. In this embodiment, a first gap region G1, a second gap region G2, a third gap region G3, and a fourth gap region G4 are formed.

[0195] In the present embodiment, a plurality of mass adding films 48A are provided across the first gap region G1 and the first edge region H1. The plurality of mass adding films 48A are arranged in a direction orthogonal to the electrode fingers. On the other hand, no mass adding film 48A is provided in the second gap region G2.

[0196] Each mass addition film 48A overlaps one of the plurality of electrode fingers when viewed from the electrode finger extending direction. Each mass addition film 48A overlaps one of the second electrode fingers 26 in a plan view. In addition, the mass addition film 48A may overlap the first electrode finger 25 or the third electrode finger 27 in a plan view.

[0197] A plurality of mass addition films 48B are provided across the third gap region G3 and the second edge region H2. The plurality of mass addition films 48B are arranged in a direction orthogonal to the electrode fingers. On the other hand, no mass addition film 48B is provided in the fourth gap region G4.

[0198] Each mass addition film 48B overlaps one of the plurality of electrode fingers when viewed from the electrode finger extending direction. Each mass addition film 48B overlaps one of the first electrode fingers 25 in a plan view. In addition, the mass addition film 48B may overlap the second electrode finger 26 or the third electrode finger 27 in a plan view.

[0199] Fig.16 It is a schematic plan view of an elastic wave device according to the eighth embodiment.

[0200] The difference between this embodiment and the seventh embodiment is that the mass addition film 48A is provided across the first edge region H1, the first gap region G1, and the second gap region G2. The difference between this embodiment and the seventh embodiment is that the mass addition film 48B is provided across the second edge region H2, the third gap region G3, and the fourth gap region G4. Except for the above points, the elastic wave device of this embodiment has the same structure as the elastic wave device of the seventh embodiment.

[0201] The mass adding film 48A is continuously provided from the first edge region H1 to the second gap region G2 in the electrode finger extending direction. The mass adding film 48A overlaps with the connection electrode 24 on the first bus bar 22 side in a plan view. The mass adding film 48A is provided in the entire first gap region G1 and the second gap region G2 in the electrode finger extending direction.

[0202] The mass adding film 48B is continuously provided from the second edge region H2 to the fourth gap region G4 in the electrode finger extending direction. The mass adding film 48B overlaps with the connection electrode 24 on the second bus bar 23 side in a plan view. The mass adding film 48B is provided in the entirety of the third gap region G3 and the fourth gap region G4 in the electrode finger extending direction.

[0203] Fig.17 It is a schematic plan view of an elastic wave device according to a ninth embodiment.

[0204] This embodiment is different from the sixth embodiment in the positions of the mass addition film 48A and the mass addition film 48B. Except for the above-mentioned points, the elastic wave device of this embodiment has the same structure as the elastic wave device of the sixth embodiment. In this embodiment, the first gap region G1, the second gap region G2, and the fifth gap region G5 are formed.

[0205] A plurality of mass adding films 48A are provided across the first gap region G1 and the first edge region H1. The plurality of mass adding films 48A are arranged in a direction orthogonal to the electrode fingers. On the other hand, no mass adding film 48A is provided in the second gap region G2.

[0206] Each mass addition film 48A overlaps one of the plurality of electrode fingers when viewed from the electrode finger extending direction. Each mass addition film 48A overlaps one of the second electrode fingers 26 in a plan view. In addition, the mass addition film 48A may overlap the first electrode finger 25 or the third electrode finger 27 in a plan view.

[0207] A plurality of mass adding films 48B are provided across the fifth gap region G5 and the second edge region H2 . The plurality of mass adding films 48B are arranged in a direction orthogonal to the electrode fingers.

[0208] Each mass addition film 48B overlaps one of the plurality of electrode fingers when viewed from the electrode finger extending direction. A portion of the plurality of mass addition films 48B overlaps one of the first electrode fingers 25 in a plan view. The remaining plurality of mass addition films 48B overlaps one of the third electrode fingers 27 in a plan view. In addition, the mass addition film 48B may overlap the second electrode finger 26 in a plan view.

[0209] Fig.18It is a schematic plan view of an elastic wave device according to a tenth embodiment.

[0210] The present embodiment differs from the ninth embodiment in that a mass addition film 48A is provided across the first edge region H1 , the first gap region G1 , and the second gap region G2 . Except for the above point, the elastic wave device of the present embodiment has the same structure as the elastic wave device of the ninth embodiment.

[0211] The mass adding film 48A is continuously provided from the first edge region H1 to the second gap region G2 in the electrode finger extending direction. The mass adding film 48A overlaps with the connection electrode 24 on the first bus bar 22 side in a plan view. The mass adding film 48A is provided in the entire first gap region G1 and the second gap region G2 in the electrode finger extending direction.

[0212] Fig.19 FIG. 1 is a schematic plan view of a first elastic wave resonator according to the eleventh embodiment. Fig. 20 It is a schematic front cross-sectional view showing the vicinity of the first to third electrode fingers in the eleventh embodiment.

[0213] like Fig.19 as well as Fig. 20 As shown, this embodiment differs from the sixth embodiment in that the third electrode 39 is provided on the second principal surface 14b of the piezoelectric layer 14. Except for the above point, the elastic wave device of this embodiment has the same structure as the elastic wave device of the sixth embodiment.

[0214] The configuration of the third electrode 39 in the present embodiment in a plan view is the same as that in the sixth 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 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, the order in which the plurality of electrode fingers are arranged is such that, starting from the first electrode finger 25, the first electrode finger 25, the third electrode finger 27, the second electrode finger 26, and the third electrode finger 27 are arranged as one cycle.

[0215] When the third electrode 39 is provided on the second main surface 14 b of the piezoelectric layer 14 , each gap region can be defined in the same manner as in the sixth embodiment.

[0216] Specifically, in a plan view, the region located between the front ends of the plurality of second electrode fingers 26 and the third bus bar 34 as the connection electrode and extending in the direction orthogonal to the electrode fingers is the first gap region G1. In a plan view, the region located between the third bus bar 34 and the first bus bar 22 and extending in the direction orthogonal to the electrode fingers is the second gap region G2. In a plan view, the region located between the front ends of the plurality of first electrode fingers 25 and the second bus bar 23 in the direction in which the electrode fingers extend and extending in the direction orthogonal to the electrode fingers is the fifth gap region G5.

[0217] The mass addition film 28A is provided across the first gap region G1 and the first edge region H1. The mass addition film 28B is provided across the fifth gap region G5 and the second edge region H2. Thus, in this embodiment, similarly to the sixth 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.

[0218] In addition, the structure in which the third electrode 39 is provided on the second main surface 14b of the piezoelectric layer 14 can also be applied to other aspects of the present invention. Figure 2 The third electrode 19 is the same as the first embodiment shown in FIG. In this case, a first gap region G1, a second gap region G2, a third gap region G3, and a fourth gap region G4 can be defined.

[0219] In the present invention, a through hole may be provided in the gap region. In this case, a mass adding film may not be provided. This example is shown below.

[0220] Fig.21 FIG. 1 is a schematic top view of an elastic wave device according to the twelfth embodiment. Fig.21 In FIG. 1 , the electrodes and the piezoelectric layer 14 are shown with hatching. Fig.21 Similarly, in other schematic plan views, the electrodes and the piezoelectric layer 14 may be hatched.

[0221] The elastic wave device 50 is an acoustic coupling filter and includes the piezoelectric substrate 12 and the functional electrode 11 similar to those of the first embodiment. The elastic wave device 50 includes a first gap region G1 , a second gap region G2 , a third gap region G3 , and a fourth gap region G4 .

[0222] The elastic wave device 50 has a plurality of excitation regions C and an intersection region E, similarly to the first embodiment. The elastic wave device 50 is configured to utilize a thickness shear mode. However, the elastic wave device 50 may be configured to utilize a plate wave.

[0223] The piezoelectric layer 14 comprises Z-cut lithium niobate. However, the piezoelectric layer 14 may also comprise rotated Y-cut lithium niobate.

[0224] like Fig.21 As shown, a plurality of through holes 54c are provided in the piezoelectric layer 14 as a piezoelectric film. A portion of the plurality of through holes 54c among all the through holes 54c are located in the first gap region G1. More specifically, in the first gap region G1, the through holes 54c are located in all portions where the first electrode finger 25, the second electrode finger 26, and the third electrode finger 27 are not provided.

[0225] The remaining plurality of through holes 54c among all the through holes 54c are located in the third gap region G3. In the third gap region G3, the through holes 54c are located in all portions where the first electrode fingers 25, the second electrode fingers 26, and the third electrode fingers 27 are not provided. In addition, when the piezoelectric film is a stacked film including the piezoelectric layer 14, it is sufficient that the through holes 54c penetrate the stacked film.

[0226] The present embodiment is characterized in that it has the following structure. 1) In a plan view, the third electrode finger 27 of the third electrode 19 is provided between the first electrode finger 25 of the first comb-shaped electrode 17 and the second electrode finger 26 of the second comb-shaped electrode 18. 2) In the first gap region G1 and the third gap region G3, a through hole 54c is provided in the piezoelectric layer 14 as a piezoelectric film. 3) In a plan view, in the region where the through hole 54c is provided, the through hole 54c is located in all portions where the first electrode finger 25, the second electrode finger 26, and the third electrode finger 27 are not provided.

[0227] However, it is sufficient that the through hole 54c is provided in the piezoelectric layer 14 in at least any one of the first gap region G1, the second gap region G2, the third gap region G3, and the fourth gap region G4. In this case, it is sufficient that the through hole 54c is located in all parts where the electrode finger is not provided in the region where the through hole 54c is provided when viewed from above. By having the above-mentioned structure, when the elastic wave device 50 is used in a filter device, the miniaturization of the filter device can be promoted, and the insertion loss can be reduced. This is illustrated below by comparing the present embodiment with the first comparative example.

[0228] The difference between the first comparative example and the twelfth embodiment is that no through hole is provided in the piezoelectric layer. In the first comparative example, the piezoelectric layer includes Z-cut lithium niobate. In the twelfth embodiment and the first comparative example, the pass characteristics are compared. The design parameters of the elastic wave device 50 having the structure of the twelfth embodiment are as follows.

[0229] Piezoelectric layer: material is LiNbO3, Euler angles (φ, θ, ψ) are (0°, 0°, 90°), thickness is 400nm

[0230] The first to third electrode fingers: the layer structure is Ti layer / AlCu layer / Ti layer from the piezoelectric layer side, and the thickness of each layer is 10nm / 390nm / 4nm from the piezoelectric layer side

[0231] The order of the first electrode finger to the third electrode finger is in the order indicated by the potentials to which they are connected: IN, GND, OUT, GND are repeated in this order.

[0232] The center-to-center distance between adjacent electrode fingers: 1.4 μm

[0233] Duty cycle: 0.3

[0234] In the first comparative example, the same design parameters as those of the twelfth embodiment are used except that no through-hole is provided.

[0235] Fig. 22 It is a diagram showing the transmission characteristics of the elastic wave devices according to the twelfth embodiment and the first comparative example.

[0236] First, if Fig. 22 As shown, it can be seen that in the elastic wave device 50 according to the twelfth embodiment, a filter waveform can be obtained appropriately. Therefore, when the elastic wave device 50 is used in a filter device, even if the number of elastic wave resonators constituting the filter device is small, a filter waveform can be obtained appropriately. Therefore, the miniaturization of the filter device can be promoted.

[0237] In addition, if Fig. 22 As shown, it can be seen that in the twelfth embodiment, the loss near the center of the passband and on the low-frequency side is smaller than in the first comparative example. Therefore, when elastic wave device 50 is used in a filter device, the insertion loss can be reduced.

[0238] The following describes the 13th and 14th embodiments in which only the configuration of the through hole 54c is different from the 12th embodiment. In the 13th and 14th embodiments, similarly to the 12th embodiment, when the elastic wave device is used for the filter device, the miniaturization of the filter device can be promoted and the insertion loss can be reduced.

[0239] Fig.23 It is a schematic plan view of an elastic wave device according to a thirteenth embodiment.

[0240] In the present embodiment, a plurality of through holes 54c are provided in the second gap region G2 and the fourth gap region G4 in the piezoelectric layer 14 as a piezoelectric film. No through holes 54c are provided in the first gap region G1 and the third gap region G3 in the piezoelectric layer 14. In a plan view, in the region where the through holes 54c are provided, the through holes 54c are located in all portions where no electrode fingers are provided.

[0241] Fig.24 It is a schematic plan view of an elastic wave device according to a fourteenth embodiment.

[0242] In the present embodiment, a plurality of through holes 54c are provided in the first gap region G1, the second gap region G2, the third gap region G3, and the fourth gap region G4 in the piezoelectric layer 14 as a piezoelectric film. In a plan view, in the region where the through holes 54c are provided, the through holes 54c are located in all portions where no electrode fingers are provided.

[0243] In this embodiment and the first comparative example, the pass characteristics are compared. Fig. 22 The design parameters in the 12th embodiment involved in the comparison shown are the same.

[0244] Fig.25 It is a diagram showing the transmission characteristics of the elastic wave devices according to the fourteenth embodiment and the first comparative example.

[0245] like Fig.25 As shown, it can be seen that in the fourteenth embodiment, the loss is smaller near the center of the passband and on the low-frequency side than in the first comparative example.

[0246] The structure in which the through hole is provided in the gap region can also be applied to the case where the gap region is the first gap region G1 , the second gap region G2 , and the fifth gap region G5 . This example is described in the fifteenth embodiment.

[0247] Fig.26 It is a schematic plan view of an elastic wave device according to a fifteenth embodiment.

[0248] In this embodiment, the functional electrodes are configured similarly to the sixth embodiment. In this embodiment, the third gap region G3 and the fourth gap region G4 are not configured. In this embodiment, the first gap region G1, the second gap region G2, and the fifth gap region G5 are configured.

[0249] The present embodiment is characterized in that it has the following structure. 1) In a plan view, the third electrode finger 27 of the third electrode 19 is provided between the first electrode finger 25 of the first comb-shaped electrode 17 and the second electrode finger 26 of the second comb-shaped electrode 18. 2) In the first gap region G1 and the fifth gap region G5, a through hole 54c is provided in the piezoelectric layer 14 as a piezoelectric film. 3) In a plan view, in the region where the through hole 54c is provided, the through hole 54c is located in all portions where the first electrode finger 25, the second electrode finger 26, and the third electrode finger 27 are not provided.

[0250] In addition, it is sufficient that the through hole 54c is provided in the piezoelectric layer 14 as the piezoelectric film in at least any one of the first gap region G1, the second gap region G2, and the fifth gap region G5. In this case, it is sufficient that the through hole 54c is located in all portions where the electrode finger is not provided in the region where the through hole 54c is provided when viewed from above. By having the above structure, when the elastic wave device is used for the filter device, the miniaturization of the filter device can be promoted, and the insertion loss can be reduced.

[0251] The following uses an example in which the functional electrode is an IDT electrode to illustrate the details of the thickness shear mode. In addition, the IDT electrode does not have a third electrode finger. The "electrode" in the IDT electrode described later is equivalent to the electrode finger. 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.

[0252] Fig. 27 (a) is a schematic perspective view showing the appearance of an elastic wave device using a thickness shear mode bulk wave, Fig. 27 (b) is a top view showing the electrode structure on the piezoelectric layer. Fig.28 yes Fig. 27 (a) is a cross-sectional view of the portion along line AA.

[0253] The elastic wave device 1 has a piezoelectric layer 2 including LiNbO3. The piezoelectric layer 2 may also include LiTaO3. The cutting angle of LiNbO3 and LiTaO3 is Z-cut, but may also be a rotated Y-cut or X-cut. The thickness of the piezoelectric layer 2 is not particularly limited, but in order to effectively excite the thickness shear mode, it is preferably greater than 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. 27 (a) and Fig. 27In (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 orthogonal to the length direction, the electrode 3 and the adjacent electrode 4 are opposed to each other. The length directions of the electrodes 3 and 4 and the directions orthogonal to the length directions of the electrodes 3 and 4 are both directions intersecting 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 the thickness direction of the piezoelectric layer 2. In addition, the length directions of the electrodes 3 and 4 and Fig. 27 (a) and Fig. 27 The direction perpendicular to the length direction of electrodes 3 and 4 shown in (b) is reversed. Fig. 27 (a) and Fig. 27 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. 27 (a) and Fig. 27 (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 above-mentioned electrodes 3 and 4. Here, the so-called electrode 3 and electrode 4 are adjacent does not refer to the case where the electrode 3 and electrode 4 are configured to be in direct contact, but refers to the case where the electrode 3 and electrode 4 are configured to be spaced apart. In addition, when the electrode 3 and electrode 4 are adjacent, no electrode connected to the signal electrode and the ground electrode including other electrodes 3 and 4 is configured between the electrode 3 and the electrode 4. The number of pairs does not need to be an integer pair, and can also be 1.5 pairs, 2.5 pairs, etc. The center-to-center distance between the electrodes 3 and 4, that is, the spacing, is preferably in the range of 1 μm or more and 10 μm or less. In addition, the width of the electrodes 3 and 4, that is, the size 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.

[0254] 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°).

[0255] 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.28 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.

[0256] 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 more than 4 kΩcm. However, the supporting member 8 can also be composed of suitable insulating materials or semiconductor materials.

[0257] 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.

[0258] The plurality of electrodes 3, 4 and the first bus bar 5 and the second bus bar 6 are made of 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.

[0259] During driving, an AC voltage is applied between the plurality of electrodes 3 and the plurality of electrodes 4. More specifically, an AC voltage is applied between the first bus bar 5 and the second bus bar 6. Thus, it is possible to obtain a resonance characteristic of a body wave utilizing a thickness shear mode excited in the piezoelectric layer 2. In addition, in the elastic wave device 1, when the thickness of the piezoelectric layer 2 is set to d and the center-to-center distance between any adjacent electrodes 3 and 4 in the plurality of pairs of electrodes 3 and 4 is set to p, d / p is set to be less than 0.5. Therefore, the body wave of the thickness shear mode can be effectively excited, and a good resonance characteristic can be obtained. More preferably, d / p is less than 0.24, in which case, a better resonance characteristic can be obtained.

[0260] 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.29 (a) and Fig.29 (b) describes the difference between the Lamb wave used in the elastic wave device and the body wave of the thickness shear mode.

[0261] Fig.29 (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.29 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.

[0262] In contrast, Fig.29As shown in (b), in the elastic wave device 1, the vibration displacement is in the thickness shear direction, so the wave propagates and resonates almost in the direction connecting the first main surface 2a and the second main surface 2b of the piezoelectric layer 2, that is, the Z direction. That is, the X-direction component of the wave is significantly smaller than the Z-direction component. Moreover, since the resonance characteristic is obtained by the propagation of the wave in the Z direction, it is not easy to generate propagation loss even if the number of electrode fingers of the reflector is reduced. Furthermore, even if the number of pairs of electrode pairs including electrodes 3 and 4 is reduced in order to promote miniaturization, it is not easy to generate a decrease in the Q value.

[0263] In addition, if Fig.30 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.30 , a body wave is schematically shown when a voltage is applied between electrode 3 and electrode 4 so that electrode 4 has a higher potential than electrode 3. The first region 451 is a region between an imaginary plane VP1 in the excitation region C and the first principal surface 2a, and 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 in the excitation region C and the second principal surface 2b.

[0264] As described above, elastic wave device 1 includes at least one pair of electrodes 3 and 4 , but waves are not propagated in the X direction, so there is no need to have more than one pair of electrodes 3 and 4 . In other words, at least one pair of electrodes is sufficient.

[0265] For example, the electrode 3 is an electrode connected to the signal potential, and the electrode 4 is an electrode connected to the ground potential. However, the electrode 3 may be connected to the ground potential, and the electrode 4 may be connected to the signal potential. In the elastic wave device 1, at least one pair of electrodes is an electrode connected to the signal potential or an electrode connected to the ground potential as described above, and no floating electrode is provided.

[0266] Fig.31 It is shown Fig.28 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.

[0267] Piezoelectric layer 2: LiNbO3 with Euler angles of (0°, 0°, 90°), thickness = 400 nm.

[0268] When observed in a direction orthogonal to the length direction of electrode 3 and electrode 4, the length of the overlapping area of ​​electrode 3 and electrode 4, i.e., the excitation area C, is 40 μm, the number of pairs of electrodes including electrodes 3 and 4 is 21 pairs, the center distance between electrodes is 3 μm, the width of electrodes 3 and 4 is 500 nm, and d / p is 0.133.

[0269] Insulating layer 7: a silicon oxide film having a thickness of 1 μm.

[0270] Supporting member 8: Si.

[0271] 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 .

[0272] 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.

[0273] according to Fig.31 It is clear that, despite the absence of a reflector, a good resonance characteristic with a relative bandwidth of 12.5% ​​is obtained.

[0274] Furthermore, 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.32 This is explained.

[0275] and got Fig.31 The elastic wave devices having the same resonant characteristics as those shown above are obtained by changing d / p. Fig.32 3 is a diagram showing the relationship between d / p and the relative bandwidth of a resonator as an elastic wave device.

[0276] according to Fig.32 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.

[0277] Fig.33 80 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.33K 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. 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.

[0278] In the elastic wave device 1, preferably, among the plurality of electrodes 3 and 4, the metallization ratio MR of any adjacent electrodes 3 and 4 with respect 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 light can be effectively reduced. Fig.34 as well as Fig.35 This is explained. Fig.34 : 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.

[0279] Reference Fig. 27 (b) will explain the metallization ratio MR. Fig. 27 In the electrode structure of (b), when focusing on a pair of electrodes 3 and 4, it is assumed that only the pair of electrodes 3 and 4 are provided. In this case, the portion surrounded by the single-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, that is, in the opposite direction. Moreover, the area of ​​the electrodes 3 and 4 in the excitation region C relative to the area of ​​the excitation region C becomes 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.

[0280] 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 used as MR.

[0281] Fig.35 This is a diagram showing the relationship between the relative bandwidth and the phase rotation amount of the impedance of the stray normalized by 180 degrees when a plurality of elastic wave resonators are formed according to the structure of the elastic wave device 1. In addition, the relative bandwidth was adjusted by making various changes to the film thickness of the piezoelectric layer and the size of the electrode. In addition, Fig.35These 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.

[0282] exist Fig.35 In the area surrounded by the ellipse J in , the spurious signal becomes larger and becomes 1.0. Fig.35 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.34 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.

[0283] Fig.36 : is a graph showing the relationship between d / 2p, metallization ratio MR, and relative bandwidth. In the above-mentioned elastic wave device, various elastic wave devices with different d / 2p and MR were constructed, and the relative bandwidth was measured. Fig.36 The hatched portion on the right side of the dotted line D is an area where the relative bandwidth is less than 17%. The boundary between the hatched area and the unhatched area can be represented by MR=3.5(d / 2p)+0.075. That is, MR=1.75(d / p)+0.075. Therefore, MR≤1.75(d / p)+0.075 is preferred. In this case, it is easy to make the relative bandwidth less than 17%. More preferably, Fig.36 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.

[0284] Fig.37 This is a diagram showing a map of the relative bandwidth with respect to the Euler angle (0°, θ, ψ) of LiNbO 3 when d / p is made as close to 0 as possible. Fig.37 The multiple regions R shown with hatching are regions where a relative bandwidth of 2% or more can be obtained. In addition, when φ in the Euler angles (φ, θ, ψ) is within the range of 0°±5°, the relationship between θ and ψ and the relative bandwidth is the same as Fig.37 In the case where the piezoelectric layer includes lithium tantalate (LiTaO3), the relationship between θ and ψ in the Euler angle (in the range of 0°±5°, θ, ψ) and BW is also the same as Fig.37 The relationships shown are the same.

[0285] Therefore, as long as the Euler angles (φ, θ, ψ) of lithium niobate or lithium tantalate constituting the piezoelectric layer are within the range of 0°±5°, θ and φ are within the range of Fig.37 If the relative bandwidth is within any of the multiple regions R shown, it is preferable that the relative bandwidth be sufficiently wide.

[0286] Fig.38 It is a front cross-sectional view of an elastic wave device having an acoustic multilayer membrane.

[0287] 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, the bulk wave of the thickness shear mode can be confined in the piezoelectric layer 2 even without using the cavity 9 in the elastic wave device 1. In the elastic wave device 81, the resonance characteristics of the bulk wave based on the thickness shear mode can be obtained by setting the above-mentioned d / p to 0.5 or less. In addition, in the acoustic multilayer film 82, the number of stacked low acoustic impedance layers 82a, 82c, 82e and high acoustic impedance layers 82b, 82d is not particularly limited. It is sufficient as long as at least one high acoustic impedance layer 82b, 82d is arranged on the side farther from the piezoelectric layer 2 than the low acoustic impedance layers 82a, 82c, 82e.

[0288] The low acoustic impedance layers 82a, 82c, 82e and the high acoustic impedance layers 82b, 82d can be made of appropriate materials 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.

[0289] Fig.39 This is a partially cutaway perspective view for explaining an elastic wave device using Lamb waves.

[0290] The elastic wave device 91 has a supporting substrate 92. The supporting substrate 92 has a recessed portion open on the upper surface. A piezoelectric layer 93 is stacked on the supporting 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.39In 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.

[0291] In the elastic wave device 91, Lamb waves as 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.

[0292] As described above, the elastic wave device of the present invention may be an elastic wave device using plate waves. Fig.39 In the example shown, the equivalent Figure 1 The main surface of the first main 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 elastic wave device of the present invention, a pair of comb-shaped electrodes are provided on the first main surface 14a, and a plurality of third electrode fingers are provided on the first main surface 14a or the second main surface 14b. In the case where the elastic wave device of the present invention is an elastic wave device using plate waves, it is sufficient that the above-mentioned reflectors 95 and 96 are provided on the first main surface 14a of the piezoelectric layer 14 in the first embodiment to the fifteenth embodiment. 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 a direction orthogonal to the electrode fingers when viewed from above.

[0293] In the elastic wave devices of the first to fifteenth embodiments, for example, an acoustic reflection film may be provided between the support member and the piezoelectric layer as the piezoelectric film. Fig.38 The acoustic multilayer membrane 82 shown. Specifically, the supporting member and the piezoelectric membrane may 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 to alternately stack low acoustic impedance layers and high acoustic impedance layers in the acoustic multilayer membrane 82. The acoustic multilayer membrane 82 may also be an acoustic reflection portion in an elastic wave device.

[0294] In the elastic wave devices of the first to fifteenth embodiments utilizing thickness shear mode bulk waves, as described above, d / p is preferably 0.5 or less, and more preferably 0.24 or less. This can provide better resonance characteristics.

[0295] Furthermore, in the excitation region of the elastic wave device of the first to fifteenth embodiments using the thickness shear mode body wave, as described above, MR ≤ 1.75 (d / p) + 0.075 is preferably satisfied. More specifically, when the metallization ratio of the first and third electrode fingers and the second and third electrode fingers with respect to the excitation region is MR, MR ≤ 1.75 (d / p) + 0.075 is preferably satisfied. In this case, spurious emission can be suppressed more reliably.

[0296] Description of Reference Numerals

[0297] 1: Elastic wave device;

[0298] 2: Piezoelectric layer;

[0299] 2a, 2b: first main surface, second main surface;

[0300] 3, 4: electrodes;

[0301] 5, 6: Bus bar 1, bus bar 2;

[0302] 7: Insulation layer;

[0303] 7a: through hole;

[0304] 8: Supporting member;

[0305] 8a: through hole;

[0306] 9: hollow part;

[0307] 10: Elastic wave device;

[0308] 10a: cavity;

[0309] 11: functional electrode;

[0310] 12: Piezoelectric substrate;

[0311] 13: Supporting member;

[0312] 14: piezoelectric layer;

[0313] 14a, 14b: 1st main surface, 2nd main surface;

[0314] 15: Insulation layer;

[0315] 16: Support base plate;

[0316] 17, 18: the first comb-shaped electrode, the second comb-shaped electrode;

[0317] 19: 3rd electrode;

[0318] 22, 23: Bus bar 1, bus bar 2;

[0319] 24: Connect electrodes;

[0320] 25-27: 1st electrode finger to 3rd electrode finger;

[0321] 28A, 28B: quality additional film;

[0322] 34: Bus bar 3;

[0323] 34A, 34B: first connecting electrode, second connecting electrode;

[0324] 34a: stripe;

[0325] 34b: protrusion;

[0326] 37: Insulation film;

[0327] 39: 3rd electrode;

[0328] 48A, 48B: quality additional film;

[0329] 50: elastic wave device;

[0330] 54c: through hole;

[0331] 80, 81: elastic wave device;

[0332] 82: Acoustic multilayer film;

[0333] 82a, 82c, 82e: low acoustic impedance layer;

[0334] 82b, 82d: high acoustic impedance layer;

[0335] 91: Elastic wave device;

[0336] 92: Support base plate;

[0337] 93: piezoelectric layer;

[0338] 94: IDT electrode;

[0339] 94a, 94b: 1st bus bar, 2nd bus bar;

[0340] 94c, 94d: first electrode finger, second electrode finger;

[0341] 95, 96: reflector;

[0342] 201: piezoelectric film;

[0343] 201a, 201b: 1st main surface, 2nd main surface;

[0344] 451, 452: Area 1, Area 2;

[0345] C: incentive area;

[0346] E: intersection area;

[0347] F: Central region;

[0348] G1~G5: 1st gap area~5th gap area;

[0349] H1, H2: 1st marginal area, 2nd marginal area;

[0350] R: region;

[0351] VP1: Imaginary plane.

Claims

1. An elastic wave device comprising: A piezoelectric film comprising a piezoelectric layer including lithium niobate; a first comb-shaped electrode, disposed on the piezoelectric layer, and comprising a first bus bar and a plurality of first electrode fingers, one end of each of which is connected to the first bus bar; A second comb-shaped electrode, disposed on the piezoelectric layer, and comprising a second bus bar and a plurality of second electrode fingers, one end of each of which is connected to the second bus bar and is interlaced with the plurality of first electrode fingers; as well as The third electrode has a plurality of third electrode fingers and a connecting electrode for connecting adjacent third electrode fingers to each other, and is 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 in a direction in which the first electrode fingers and the second electrode fingers are arranged when viewed from above, One of the first comb-shaped electrode and the second comb-shaped electrode is connected to an input potential, and the other of the first comb-shaped electrode and the second comb-shaped electrode is connected to an output potential. Regarding the order in which the first electrode finger, the second electrode finger, and the third electrode finger are arranged, when starting from the first electrode finger, the first electrode finger, the third electrode finger, the second electrode finger, and the third electrode finger are arranged as one cycle. The connection electrode connects at least the first bus bar-side tips of the adjacent third electrode fingers to each other, and the connection electrode is located at least between the first bus bar and the tips of the plurality of second electrode fingers. The direction in which the first electrode finger, the second electrode finger, and the third electrode finger extend is set as the electrode finger extending direction, and the direction orthogonal to the electrode finger extending direction is set as the electrode finger orthogonal direction. When viewed from above, the region located between the front ends of the plurality of second electrode fingers and the connecting electrode in the electrode finger extending direction and extending in the electrode finger orthogonal direction is the first gap region, and the region located between the connecting electrode and the first bus bar and extending in the electrode finger orthogonal direction is the second gap region. When viewed from above, a mass addition film is provided in at least a portion of at least any one of a region located between the front ends of the plurality of first electrode fingers and the second bus bar in the direction in which the electrode fingers extend, a region that does not include the connecting electrode and extends in a direction orthogonal to the electrode fingers, and a first gap region and a second gap region.

2. The elastic wave device according to claim 1, wherein: A plurality of the connection electrodes are provided, and a part of the plurality of connection electrodes connects the tips of the adjacent third electrode fingers on the second bus bar side to each other. When viewed from above, in the area between the front ends of the plurality of first electrode fingers and the second bus bar, the area between the front ends of the plurality of first electrode fingers and the connecting electrode in the extension direction of the electrode fingers and extending in the orthogonal direction of the electrode fingers is the third gap area, and the area between the connecting electrode and the second bus bar and extending in the orthogonal direction of the electrode fingers is the fourth gap area.

3. The elastic wave device according to claim 2, wherein: The mass addition film is provided in each of the first gap region and the third gap region.

4. The elastic wave device according to claim 3, wherein: The mass addition film is provided in each of the first gap region, the second gap region, the third gap region, and the fourth gap region.

5. The elastic wave device according to claim 1, wherein: The connection electrode connects only the tips of the tips of the adjacent third electrode fingers on the first bus bar side. In a plan view, a region located between the tips of the plurality of first electrode fingers and the second bus bar in the electrode finger extending direction and extending in a direction orthogonal to the electrode fingers is a fifth gap region.

6. The elastic wave device according to claim 5, wherein: The mass addition film is provided in each of the first gap region and the fifth gap region.

7. The elastic wave device according to claim 6, wherein: The mass addition film is provided in each of the first gap region, the second gap region, and the fifth gap region.

8. The elastic wave device according to any one of claims 3, 4, 6, or 7, wherein: The region where the first electrode finger and the second electrode finger overlap each other in the orthogonal direction of the electrode fingers is a crossing region, and the crossing region includes a central region and a first edge region and a second edge region that are arranged to sandwich the central region and face each other in the extending direction of the electrode fingers. The mass adding film is provided in each of the first edge region and the second edge region.

9. The elastic wave device according to any one of claims 1 to 8, wherein: When viewed from the extending direction of the electrode fingers, one mass additional film is provided so as to overlap with the plurality of first electrode fingers, the plurality of second electrode fingers, and the plurality of third electrode fingers.

10. The elastic wave device according to any one of claims 1 to 8, wherein: A plurality of mass addition films are arranged in a direction orthogonal to the electrode fingers, When viewed from the extending direction of the electrode fingers, one of the mass additional films is provided so as to overlap with one electrode finger among the plurality of first electrode fingers, the plurality of second electrode fingers, and the plurality of third electrode fingers.

11. The elastic wave device according to any one of claims 1 to 10, wherein: As a material of the mass additional film, at least one dielectric selected from the group consisting of silicon oxide, tungsten oxide, niobium oxide, tantalum oxide, and hafnium oxide is used.

12. An elastic wave device comprising: A piezoelectric film comprising a piezoelectric layer including lithium niobate; a first comb-shaped electrode, disposed on the piezoelectric layer, and comprising a first bus bar and a plurality of first electrode fingers, one end of each of which is connected to the first bus bar; A second comb-shaped electrode, disposed on the piezoelectric layer, and comprising a second bus bar and a plurality of second electrode fingers, one end of each of which is connected to the second bus bar and is interlaced with the plurality of first electrode fingers; as well as The third electrode has a plurality of third electrode fingers and a connecting electrode for connecting adjacent third electrode fingers to each other, and is 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 in a direction in which the first electrode fingers and the second electrode fingers are arranged when viewed from above, One of the first comb-shaped electrode and the second comb-shaped electrode is connected to an input potential, and the other of the first comb-shaped electrode and the second comb-shaped electrode is connected to an output potential. Regarding the order in which the first electrode finger, the second electrode finger, and the third electrode finger are arranged, when starting from the first electrode finger, the first electrode finger, the third electrode finger, the second electrode finger, and the third electrode finger are arranged as one cycle. The connection electrode connects at least the first bus bar-side tips of the adjacent third electrode fingers to each other, and the connection electrode is located at least between the first bus bar and the tips of the plurality of second electrode fingers. The direction in which the first electrode finger, the second electrode finger, and the third electrode finger extend is set as the electrode finger extending direction, and the direction orthogonal to the electrode finger extending direction is set as the electrode finger orthogonal direction. When viewed from above, the region located between the front ends of the plurality of second electrode fingers and the connecting electrode in the electrode finger extending direction and extending in the electrode finger orthogonal direction is the first gap region, and the region located between the connecting electrode and the first bus bar and extending in the electrode finger orthogonal direction is the second gap region. In a plan view, a through hole is provided in the piezoelectric film in at least any one of a region located between the front ends of the plurality of first electrode fingers and the second bus bar in the direction in which the electrode fingers extend and does not include the connection electrode and extends in a direction orthogonal to the electrode fingers, the first gap region, and the second gap region, In a plan view, in a region where the through hole is provided, the through hole is located in all portions where the first electrode finger, the second electrode finger, and the third electrode finger are not provided.

13. The elastic wave device according to claim 12, wherein: A plurality of the connection electrodes are provided, and a part of the plurality of connection electrodes connects the tips of the adjacent third electrode fingers on the second bus bar side to each other. When viewed from above, in the area between the front ends of the plurality of first electrode fingers and the second bus bar, the area between the front ends of the plurality of first electrode fingers and the connecting electrode in the extension direction of the electrode fingers and extending in the orthogonal direction of the electrode fingers is the third gap area, and the area between the connecting electrode and the second bus bar and extending in the orthogonal direction of the electrode fingers is the fourth gap area.

14. The elastic wave device according to claim 13, wherein: In each of the first gap region and the third gap region, the through hole is provided in the piezoelectric film.

15. The elastic wave device according to claim 14, wherein: In each of the first gap region, the second gap region, the third gap region, and the fourth gap region, the through hole is provided in the piezoelectric film.

16. The elastic wave device according to claim 12, wherein: The connection electrode connects only the tips of the tips of the adjacent third electrode fingers on the first bus bar side. In a plan view, a region located between the tips of the plurality of first electrode fingers and the second bus bar in the electrode finger extending direction and extending in a direction orthogonal to the electrode fingers is a fifth gap region.

17. The elastic wave device according to claim 16, wherein: In each of the first gap region and the fifth gap region, the through hole is provided in the piezoelectric film.

18. The elastic wave device according to claim 17, wherein: In each of the first gap region, the second gap region, and the fifth gap region, the through hole is provided in the piezoelectric film.

19. The elastic wave device according to any one of claims 1 to 18, wherein: The elastic wave device is configured to utilize thickness shear mode body waves.

20. The elastic wave device according to any one of claims 1 to 18, wherein: further comprising a supporting member stacked on the piezoelectric film, In a plan view along the stacking direction of the support member and the piezoelectric film, an acoustic reflection portion is formed at a position of the support member overlapping with the plurality of first electrode fingers, the plurality of second electrode fingers, and the plurality of third electrode fingers, When the longest distance between the centers of the adjacent first and third electrode fingers and the center distance between the adjacent second and third electrode fingers is set to p, and when the thickness of the piezoelectric film is set to d, d / p is less than or equal to 0.

5.

21. The elastic wave device according to claim 20, wherein: d / p is less than 0.

24.

22. The elastic wave device according to claim 20 or 21, wherein: The sound reflecting portion is a cavity portion, and the supporting member and the piezoelectric film are arranged so that a part of the supporting member and a part of the piezoelectric film face each other with the cavity portion interposed therebetween.

23. The elastic wave device according to claim 20 or 21, 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, and the supporting member and the piezoelectric film are configured so that at least a portion of the supporting member and at least a portion of the piezoelectric film are opposite to each other with the acoustic reflection film sandwiched therebetween.

24. The elastic wave device according to any one of claims 20 to 23, wherein: The region where the adjacent first electrode finger and the adjacent third electrode finger overlap in the orthogonal direction of the electrode finger and the region between the centers of the adjacent first electrode finger and the adjacent third electrode finger, and the region where the adjacent second electrode finger and the adjacent third electrode finger overlap in the orthogonal direction of the electrode finger and the region between the centers of the adjacent second electrode finger and the adjacent third electrode finger are the excitation region. When the metallization ratio of the first electrode finger and the third electrode finger and the second electrode finger and the third electrode finger with respect to the excitation region is MR, MR≦1.75(d / p)+0.075 is satisfied.

25. The elastic wave device according to any one of claims 1 to 24, wherein: 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) …Equation (3).

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