Elastic wave device and filter device

Abstract

Provided is an elastic wave device capable of suppressing useless waves in the vicinity of a resonant frequency or an anti-resonant frequency even when a structure in which a mass-added film is provided in an edge region and a gap region is provided. The elastic wave device has an acoustic reflection portion formed at a position overlapping the IDT electrode in the support member in a plan view as viewed in a stacking direction of the support member and the piezoelectric film. When the thickness of the piezoelectric film containing lithium niobate is d and the distance between the centers of adjacent electrode fingers is p, d / p is 0.5 or less. A region between the pair of bus bars and an intersection region (F), which is a region in which adjacent electrode fingers overlap each other when viewed from a direction orthogonal to the electrode fingers, is a pair of gap regions. The intersecting region (F) has a central region (H) and a pair of edge regions disposed so as to sandwich the central region (H) in the direction in which the electrode fingers extend. The present invention is further provided with: a strip-shaped mass-adding film which is provided in at least one gap region among the pair of gap regions, and which is continuously provided so as to overlap the plurality of electrode fingers and regions between the electrode fingers in a plan view; and a plurality of granular mass addition films that are provided across the gap region in which the band-shaped mass addition film is provided and the edge region adjacent to the gap region, and that are provided so as not to overlap with at least a part of the region between adjacent electrode fingers in at least one location in a plan view.

Description

Technical Field

[0001] The present invention relates to an elastic wave device and a filter device. Background Art

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

[0003] Patent document 2 listed below discloses an example of an elastic wave device using a piston mode. In this elastic wave device, an IDT (Interdigital Transducer) electrode is provided on a piezoelectric film. The region where the electrode fingers of the IDT electrode overlap with each other in the direction of propagation of the elastic wave is defined as an intersection region. A pair of gap regions are provided in the intersection region and in the region between a pair of bus bars of the IDT electrode. The intersection region has a central region and a pair of edge regions. The pair of edge regions are opposed to each other with the central region sandwiched in the direction in which the plurality of electrode fingers extend.

[0004] Patent Document 2 discloses an example of providing a mass-added film over the edge region, gap region, and busbar. In this example, multiple regions with different sound velocities are formed in the direction in which multiple electrode fingers extend, thereby establishing a piston mode. This achieves suppression of the transverse mode.

[0005] Prior Art Literature

[0006] Patent Literature

[0007] Patent Document 1: U.S. Patent No. 10491192

[0008] Patent Document 2: Japanese Patent Application Publication No. 2019-080093 Summary of the invention

[0009] Problem that the invention aims to solve

[0010] The inventors of the present invention have noticed that by providing mass-added films in edge regions and gap regions of an elastic wave device utilizing bulk waves in a thickness shear mode, degradation of loss can be suppressed, but on the other hand, unnecessary waves are generated near the resonance frequency and antiresonance frequency.

[0011] An object of the present invention is to provide an elastic wave device and a filter device capable of suppressing unnecessary waves near a resonance frequency or an antiresonance frequency even when a mass-added film is provided in an edge region and a gap region.

[0012] Technical solutions to solve problems

[0013] The elastic wave device according to the present invention comprises: a piezoelectric substrate having a supporting member including a supporting substrate, and a piezoelectric film provided on the supporting member and including a piezoelectric layer, wherein the piezoelectric layer includes lithium niobate; and an IDT electrode provided on the piezoelectric layer, having a pair of bus bars and a plurality of electrode fingers, wherein an acoustic reflection portion is formed at a position overlapping the IDT electrode in the supporting member in a plan view along the stacking direction of the supporting member and the piezoelectric film, wherein d / p is less than 0.5 when the thickness of the piezoelectric film is d and the center-to-center distance between adjacent electrode fingers is p, a portion of the electrode fingers among the plurality of electrode fingers are connected to one of the bus bars of the IDT electrode, and the remaining electrode fingers among the plurality of electrode fingers are connected to the other bus bar, wherein the plurality of electrode fingers connected to one of the bus bars and the plurality of electrode fingers connected to the other bus bar are interlaced with each other, and the plurality of electrode fingers connected to the bus bar are interlaced with each other. The direction in which the electrode fingers extend is set as the electrode finger extension direction, and the direction orthogonal to the electrode finger extension direction is set as the electrode finger orthogonal direction. When observed from the electrode finger orthogonal direction, the area where adjacent electrode fingers overlap with each other is an intersection area, and the area located between the intersection area and the pair of bus bars is a pair of gap areas, and the intersection area has a central area and a pair of edge areas configured to clamp the central area in the electrode finger extension direction. The elastic wave device also includes: a strip-shaped mass addition film, which is arranged in at least one gap area among the pair of gap areas, and is continuously arranged so as to overlap with the multiple electrode fingers and the area between the electrode fingers when viewed from above; and a plurality of granular mass addition films, which are arranged throughout the gap area where the strip-shaped mass addition film is arranged and the edge area adjacent to the gap area, and are arranged so as not to overlap with at least a part of the area between the adjacent electrode fingers in at least one part when viewed from above.

[0014] The filter device according to the present invention is a filter device having a plurality of elastic wave resonators including at least one series arm resonator and at least one parallel arm resonator, wherein at least one of the series arm resonator and the parallel arm resonator is an elastic wave device constructed according to the present invention.

[0015] Effects of the Invention

[0016] According to the present invention, it is possible to provide an elastic wave device and a filter device capable of suppressing unnecessary waves near a resonance frequency or an antiresonance frequency even when a mass-added film is provided in an edge region and a gap region. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0018] Figure 2 It is along Figure 1 Schematic cross-sectional view of line I-I in FIG.

[0019] Figure 3 It is a schematic plan view of an elastic wave device according to a first comparative example.

[0020] Figure 4 It is a schematic plan view of an elastic wave device according to a second comparative example.

[0021] Figure 5 It is a schematic plan view for explaining the first to third dimensions.

[0022] Figure 6 It is a graph showing the return losses in the first embodiment of the present invention, the first comparative example, and the second comparative example when the material of the strip-shaped mass adding film and the granular mass adding film is SiO 2 .

[0023] Figure 7 It is a diagram showing the excitation intensity of unnecessary waves in the first comparative example.

[0024] Figure 8 It is a diagram showing the return losses in the first embodiment of the present invention, the first comparative example, and the second comparative example when the material of the strip-shaped mass adding film and the granular mass adding film is Ta 2 O 5 .

[0025] Fig. 9 It is a schematic plan view of an elastic wave device according to a first modification example of the first embodiment of the present invention.

[0026] Fig.10 It is a schematic plan view of an elastic wave device according to a second modified example of the first embodiment of the present invention.

[0027] Fig.11 It is a schematic plan view of an elastic wave device according to a second embodiment of the present invention.

[0028] Fig.12 It is a schematic plan view of an elastic wave device according to a third embodiment of the present invention.

[0029] Fig.13It is a schematic plan view of an elastic wave device according to a fourth embodiment of the present invention.

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

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

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

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

[0034] Fig.18 This is a circuit diagram of a filter device according to an eighth embodiment of the present invention.

[0035] Fig.19 FIG. 1 is a schematic plan view of a second elastic wave resonator according to a ninth embodiment of the present invention.

[0036] Fig. 20 FIG. 1 is a schematic plan view of a third elastic wave resonator according to a ninth embodiment of the present invention.

[0037] Fig.21 FIG. 1 is a schematic plan view of a fourth elastic wave resonator according to a ninth embodiment of the present invention.

[0038] Fig. 22 FIG. 1 is a schematic plan view of a fifth elastic wave resonator according to a ninth embodiment of the present invention.

[0039] Fig.23 (a) is a schematic perspective view showing the appearance of an elastic wave device using a thickness shear mode bulk wave, Fig.23 (b) is a top view showing the electrode structure on the piezoelectric layer.

[0040] Fig.24 It is along Fig.23 (a) is a cross-sectional view of a portion taken along line AA.

[0041] Fig.25 (a) is a schematic front cross-sectional view for explaining Lamb waves propagating through a piezoelectric film of an elastic wave device. Fig.25 (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.

[0042] Fig.26 It is a diagram showing the amplitude direction of the body wave in the thickness shear mode.

[0043] Fig. 27 FIG. 1 is a diagram showing the resonance characteristics of an elastic wave device using bulk waves in a thickness shear mode.

[0044] Fig.28 1 is a diagram showing the relationship between d / p and the relative bandwidth of the resonator when the distance between the centers of adjacent electrodes is defined as p and the thickness of the piezoelectric layer is defined as d.

[0045] Fig.29 This is a top view of an elastic wave device using bulk waves in a thickness shear mode.

[0046] Fig.30 FIG. 2 is a diagram showing the resonance characteristics of an elastic wave device according to a reference example in which spurious emission occurs.

[0047] Fig.31 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.

[0048] Fig.32 It is a graph showing the relationship between d / 2p and the metallization ratio MR.

[0049] Fig.33 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.

[0050] Fig.34 It is a front cross-sectional view of an elastic wave device having an acoustic multilayer membrane. DETAILED DESCRIPTION

[0051] Hereinafter, specific embodiments of the present invention will be described with reference to the drawings to clarify the present invention.

[0052] 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.

[0053] Figure 1 It is a schematic plan view of the elastic wave device according to the first embodiment of the present invention. Figure 2 It is along Figure 1 Schematic cross-sectional view of line I-I in FIG.

[0054] like Figure 1 As shown in FIG. 1 , the elastic wave device 10 includes a piezoelectric substrate 12 and an IDT electrode 11. The piezoelectric substrate 12 is a substrate having piezoelectricity. Figure 2As shown, 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 containing 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 containing a piezoelectric body. However, in the present embodiment, the piezoelectric film is a single-layer piezoelectric layer 14, which is a film containing a piezoelectric body. In addition, in the present invention, the piezoelectric film may also be a stacked film including the piezoelectric layer 14. In the present 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.

[0055] 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.

[0056] As the material of the support substrate 16, for example, semiconductors such as silicon, ceramics such as aluminum oxide, etc. can be used. As the material of the insulating layer 15, a suitable dielectric such as silicon oxide or tantalum oxide can be used. The piezoelectric layer 14 contains, for example, lithium niobate such as LiNbO3. In this specification, the so-called "a certain component contains a certain material" includes the case where a trace amount of impurities is contained to the extent that the electrical characteristics of the elastic wave device are not significantly deteriorated.

[0057] like Figure 2 As shown, 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 block the recess. Thus, a hollow portion is formed. The hollow portion is a cavity 10a. In the present embodiment, the supporting member 13 and the piezoelectric film are configured so that a part of the supporting member 13 and a part of the piezoelectric film are opposed to each other with the cavity 10a sandwiched therebetween. However, the recess in the supporting member 13 may also be provided throughout the insulating layer 15 and the supporting substrate 16. Alternatively, it may be that only the recess provided in the supporting substrate 16 is blocked 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.

[0058] The IDT electrode 11 is provided on the first main surface 14a of the piezoelectric layer 14. In a plan view, at least a portion of the IDT electrode 11 overlaps with the cavity 10a of the support member 13. In this specification, the term "plan view" refers to a view from a direction corresponding to the direction of the piezoelectric layer 14. Figure 2 The upper direction in FIG. 1 is viewed along the stacking direction of the support member 13 and the piezoelectric film. Figure 2For example, the piezoelectric layer 14 side is the upper side of the support substrate 16 side and the piezoelectric layer 14 side. Furthermore, in this specification, the top view is defined as the same as the view from the main surface facing direction. The so-called main surface facing direction is the direction in which the first main surface 14a and the second main surface 14b of the piezoelectric layer 14 are facing each other. More specifically, the main surface facing direction is, for example, the normal direction of the first main surface 14a.

[0059] like Figure 1 As shown, the IDT electrode 11 has a pair of bus bars and a plurality of electrode fingers. The pair of bus bars is specifically the first bus bar 26 and the second bus bar 27. The first bus bar 26 and the second bus bar 27 are opposite to each other. The plurality of electrode fingers are specifically the plurality of first electrode fingers 28 and the plurality of second electrode fingers 29. One end of the plurality of first electrode fingers 28 is respectively connected to the first bus bar 26. One end of the plurality of second electrode fingers 29 is respectively connected to the second bus bar 27. The plurality of first electrode fingers 28 and the plurality of second electrode fingers 29 are interlaced with each other. The IDT electrode 11 may also include a single-layer metal film, or may include a stacked metal film.

[0060] Hereinafter, the first bus bar 26 and the second bus bar 27 are sometimes collectively described as simply bus bars. The first electrode finger 28 and the second electrode finger 29 are sometimes collectively described as simply electrode fingers. The direction in which the plurality of electrode fingers extend is defined as the electrode finger extending direction, and the direction orthogonal to the electrode finger extending direction is defined as the electrode finger orthogonal direction. In addition, when the direction in which adjacent electrode fingers face each other is defined as the electrode finger facing direction, the electrode finger orthogonal direction and the electrode finger facing direction are parallel.

[0061] When viewed from the orthogonal direction of the electrode fingers, the region where adjacent electrode fingers overlap each other is the intersection region F. The intersection region F has a central region H and a pair of edge regions. The pair of edge regions are specifically a first edge region E1 and a second edge region E2. The first edge region E1 and the second edge region E2 are configured to sandwich the central region H in the extending direction of the electrode fingers. The first edge region E1 is located on the first bus bar 26 side. The second edge region E2 is located on the second bus bar 27 side.

[0062] The region between the intersection region F and the pair of bus bars is a pair of gap regions. Specifically, the pair of gap regions are the first gap region G1 and the second gap region G2. The first gap region G1 is located between the first bus bar 26 and the first edge region E1. The second gap region G2 is located between the second bus bar 27 and the second edge region E2.

[0063] The elastic wave device 10 is an elastic wave resonator configured to utilize a thickness shear mode bulk wave. More specifically, in the elastic wave device 10, when the thickness of the piezoelectric film is set to d and the center-to-center distance between adjacent electrode fingers is set to p, d / p is less than 0.5. Thus, a thickness shear mode bulk wave can be appropriately excited. In the present embodiment, the thickness d is the thickness of the piezoelectric layer 14.

[0064] When viewed from the orthogonal direction of the electrode fingers, the area where adjacent electrode fingers overlap each other and the area between the centers of adjacent electrode fingers is the excitation area. That is, the intersection area F includes a plurality of excitation areas. In each excitation area, a body wave of the thickness shear mode is excited. In addition, the intersection area F, the excitation area, and a pair of gap areas are areas of the piezoelectric layer 14 defined based on the structure of the IDT electrode 11. However, the intersection area F and the pair of gap areas can also be said to be areas possessed by the IDT electrode 11 when representing the structure of the IDT electrode 11.

[0065] Figure 2 The hollow portion 10a of the support member 13 shown is the sound reflection portion in the present invention. Through the sound reflection portion, the energy of the elastic wave can be effectively confined on the side of the piezoelectric layer 14. In addition, an acoustic multilayer film described later may also be provided as the sound reflection portion. For example, an acoustic reflection film may also be provided on the surface of the support member.

[0066] In this specification, the first edge region E1 and the second edge region E2 are sometimes collectively recorded as simply the edge region. Similarly, the first gap region G1 and the second gap region G2 are sometimes collectively recorded as simply the gap region. Furthermore, below, when a component is arranged to overlap with an edge region in a plan view, it is sometimes recorded simply as the component being arranged in the edge region. For example, even when the component is not directly arranged on the piezoelectric layer 14, it is sometimes recorded as the component being arranged in the edge region. The same is true for the gap region.

[0067] like Figure 1 As shown, the elastic wave device 10 has a pair of strip-shaped mass-adding films. The strip-shaped mass-adding films are mass-adding films having a strip shape. Specifically, the pair of strip-shaped mass-adding films are a first strip-shaped mass-adding film 24A and a second strip-shaped mass-adding film 24B. The first strip-shaped mass-adding film 24A is provided in the first gap region G1. The second strip-shaped mass-adding film 24B is provided in the second gap region G2.

[0068] The elastic wave device 10 includes a plurality of granular mass adding films. The granular mass adding films are smaller in size in the direction perpendicular to the electrode fingers than the strip-shaped mass adding films. Specifically, the plurality of granular mass adding films are a plurality of first granular mass adding films 25A and a plurality of second granular mass adding films 25B.

[0069] The plurality of first granular mass addition films 25A are provided over the first gap region G1 and the first edge region E1. The plurality of first granular mass addition films 25A are arranged in a direction orthogonal to the electrode fingers. The plurality of second granular mass addition films 25B are provided over the second gap region G2 and the second edge region E2. The plurality of second granular mass addition films 25B are arranged in a direction orthogonal to the electrode fingers.

[0070] In this specification, the first band-shaped mass adding film 24A and the second band-shaped mass adding film 24B are sometimes collectively described as simply a band-shaped mass adding film. The first granular mass adding film 25A and the second granular mass adding film 25B are sometimes collectively described as simply a granular mass adding film. The structures of the band-shaped mass adding film and the granular mass adding film are described in more detail below.

[0071] The first strip-shaped mass adding film 24A is provided on the first main surface 14a of the piezoelectric layer 14 so as to cover the plurality of electrode fingers. The first strip-shaped mass adding film 24A is provided continuously so as to overlap with the plurality of first electrode fingers 28 and the plurality of second electrode fingers 29 and the regions between the electrode fingers in a plan view. The second strip-shaped mass adding film 24B is also provided continuously so as to overlap with the plurality of first electrode fingers 28 and the plurality of second electrode fingers 29 and the regions between the electrode fingers in a plan view.

[0072] The first strip-shaped mass-adding film 24A is provided in a part of the first gap region G1. More specifically, the first strip-shaped mass-adding film 24A reaches the edge portion on the first bus bar 26 side in the electrode finger extending direction of the first gap region G1. The second strip-shaped mass-adding film 24B is provided in a part of the second gap region G2. The second strip-shaped mass-adding film 24B reaches the edge portion on the second bus bar 27 side in the electrode finger extending direction of the second gap region G2. However, the configuration of the first strip-shaped mass-adding film 24A and the second strip-shaped mass-adding film 24B is not limited to the above.

[0073] The plurality of first granular mass addition films 25A and the plurality of second granular mass addition films 25B are arranged at a period of one electrode finger in the direction orthogonal to the electrode fingers. Specifically, the plurality of first granular mass addition films 25A overlap with the second electrode fingers 29 in a plan view. The plurality of first granular mass addition films 25A do not overlap with the first electrode fingers 28 in a plan view. On the other hand, the plurality of second granular mass addition films 25B overlap with the first electrode fingers 28 in a plan view. The plurality of second granular mass addition films 25B do not overlap with the second electrode fingers 29 in a plan view.

[0074] For example, the first granular mass addition films 25A and the second granular mass addition films 25B may overlap with both the first electrode fingers 28 and the second electrode fingers 29 in a plan view.

[0075] Each first granular mass addition film 25A overlaps with one electrode finger in a plan view. Specifically, each first granular mass addition film 25A is provided over the first main surface 14a of the piezoelectric layer 14 and one electrode finger. Each first granular mass addition film 25A is provided without extending over a plurality of electrode fingers. In this way, each first granular mass addition film 25A is provided so as not to overlap with a portion between the electrode fingers in a plan view.

[0076] Each second granular mass adding film 25B is also provided over the first main surface 14a of the piezoelectric layer 14 and one electrode finger. Each second granular mass adding film 25B is not provided over a plurality of electrode fingers. Each second granular mass adding film 25B is provided so as not to overlap a portion between electrode fingers in a plan view.

[0077] In addition, the granular mass adding film may overlap with one or more electrode fingers in a plan view. Alternatively, the granular mass adding film may not necessarily overlap with the electrode fingers in a plan view. In this case, preferably, the portion of the granular mass adding film located in the gap region is located on the extension line of the electrode fingers in a plan view.

[0078] IDT electrode 11 has a plurality of pairs of first electrode fingers 28 and second electrode fingers 29. Therefore, elastic wave device 10 has a plurality of regions between electrode fingers. In the present invention, the granular mass addition film may be provided so as not to overlap at least a portion of at least one region between adjacent electrode fingers in a plan view.

[0079] In the present embodiment, the first band-shaped mass adding film 24A, the plurality of first granular mass adding films 25A, the second band-shaped mass adding film 24B, and the plurality of second granular mass adding films 25B include a dielectric.

[0080] The first band-shaped mass adding film 24A and the plurality of first granular mass adding films 25A are formed integrally of the same material. The second band-shaped mass adding film 24B and the plurality of second granular mass adding films 25B are formed integrally of the same material. However, the first band-shaped mass adding film 24A and the plurality of first granular mass adding films 25A may also be provided independently. The second band-shaped mass adding film 24B and the plurality of second granular mass adding films 25B may also be provided independently.

[0081] The elastic wave device 10 only needs to include at least one of the first strip-shaped mass adding film 24A and the second strip-shaped mass adding film 24B. In other words, the strip-shaped mass adding film only needs to be provided in at least one of the pair of gap regions.

[0082] The elastic wave device 10 may include at least one of a plurality of first granular mass adding films 25A and a plurality of second granular mass adding films 25B. The plurality of granular mass adding films may be provided in the gap region where the strip-shaped mass adding films are provided and in the edge region adjacent to the gap region. For example, when the first strip-shaped mass adding films 24A are provided, the plurality of first granular mass adding films 25A may be provided. When the second strip-shaped mass adding films 24B are provided, the plurality of second granular mass adding films 25B may be provided.

[0083] The present embodiment is characterized in that a strip-shaped mass addition film is provided in the gap region, and a plurality of granular mass addition films are provided in the gap region where the strip-shaped mass addition film is provided and in an edge region adjacent to the gap region. By providing a plurality of granular mass addition films in the edge region, transverse modes can be suppressed. Furthermore, by providing both the strip-shaped mass addition film and the granular mass addition film, unnecessary waves generated by providing the mass addition film can be suppressed.

[0084] In addition, unnecessary waves caused by the provision of the mass-added film are generated near the resonant frequency or near the anti-resonant frequency. In this embodiment, in the case of a structure in which the mass-added film is provided in the edge region and the gap region, it is also possible to suppress unnecessary waves near the resonant frequency or near the anti-resonant frequency. The following describes the details of this effect by comparing this embodiment with the first comparative example and the second comparative example.

[0085] like Figure 3 As shown, the difference between the first comparative example and the first embodiment is that a pair of band-shaped mass adding films are provided over a pair of gap regions and a pair of edge regions, and no granular mass adding film is provided. Specifically, in the first comparative example, the first band-shaped mass adding film 74A is provided over the first gap region G1 and the first edge region E1. The second band-shaped mass adding film 74B is provided over the second gap region G2 and the second edge region E2. Each band-shaped mass adding film is provided continuously so as to overlap with a plurality of electrode fingers and the regions between the electrode fingers in a plan view.

[0086] like Figure 4As shown, the second comparative example is different from the first embodiment in that no strip-shaped mass adding film is provided. In the second comparative example, a plurality of first granular mass adding films 25A are provided over the first gap region G1 and the first edge region E1. A plurality of second granular mass adding films 25B are provided over the second gap region G2 and the second edge region E2.

[0087] Return losses were measured in the elastic wave device 10 having the structure of the first embodiment, the elastic wave device of the first comparative example, and the elastic wave device of the second comparative example. In these elastic wave devices, SiO2 was used as the material of the strip-shaped mass addition film and the granular mass addition film.

[0088] In addition, in the first embodiment involved in this comparison, Figure 5 The first dimension L1, the second dimension L2, and the third dimension L3 shown are set as follows.

[0089] The first dimension L1 is the dimension of the gap region along the direction in which the electrode fingers extend. The second dimension L2 is the dimension of the portion of the granular mass addition film disposed in the region between the electrode fingers at one location, along the direction orthogonal to the electrode fingers. The third dimension L3 is the dimension of the portion of the granular mass addition film disposed in the gap region, along the direction in which the electrode fingers extend. In the first embodiment involved in the comparison, the first dimension L1 is set to 7 μm, the second dimension L2 is set to 0.5 μm, and the third dimension L3 is set to 2 μm. In the first embodiment involved in the comparison, the thickness of the band-shaped mass addition film and the granular mass addition film is set to 30 nm.

[0090] Figure 6 It is a graph showing the return losses in the first embodiment, the first comparative example, and the second comparative example when the material of the strip-shaped mass adding film and the granular mass adding film is SiO 2 .

[0091] like Figure 6 As shown in FIG. 1 , in the first comparative example, unnecessary waves are generated near the frequencies indicated by arrows M1 and M2. In the second comparative example, unnecessary waves are generated near the frequency indicated by arrow M2, near the resonant frequency indicated by arrow M3, and near the anti-resonant frequency indicated by arrow M4. In contrast, in the first embodiment, it can be seen that unnecessary waves are suppressed near the frequencies indicated by arrows M1, M2, M3, and M4. This is based on the following reasons.

[0092] Figure 7 It is a diagram showing the excitation intensity of unnecessary waves in the first comparative example.

[0093] In the first comparative example, the excitation intensity of the unnecessary wave is particularly large in the region where the band-shaped mass addition film is provided between the electrode fingers. On the other hand, the excitation intensity of the unnecessary wave is small in the region where the band-shaped mass addition film is stacked with the electrode fingers. On the other hand, in the second comparative example, a plurality of granular mass addition films are provided in a portion that is not located between adjacent electrode fingers. Therefore, in the second comparative example, the unnecessary wave is suppressed compared to the first comparative example. Figure 6 On the other hand, in the first comparative example, the unnecessary waves near the frequencies indicated by the arrows M1 and M2 are suppressed compared with the second comparative example.

[0094] In the first embodiment, a band-shaped mass-adding film is provided in the gap region. Figure 6 In addition, a plurality of granular mass addition films are provided in the edge region instead of the band-shaped mass addition films. The plurality of granular mass addition films are provided as a part of the electrode fingers that are not located adjacent to each other. Thus, the unnecessary waves near the frequencies indicated by the arrows M1 and M2 can be suppressed.

[0095] Furthermore, the same comparison as above was performed when Ta2O5 was used as the material of the band-shaped mass adding film and the granular mass adding film. In the first embodiment of this comparison, the thickness of the band-shaped mass adding film and the granular mass adding film was set to 15 nm.

[0096] Figure 8 It is a diagram showing the return losses in the first embodiment, the first comparative example, and the second comparative example when the material of the strip-shaped mass adding film and the granular mass adding film is Ta 2 O 5 .

[0097] like Figure 8 As shown, it can be seen that in the case where the strip-shaped mass-added film and the granular mass-added film include Ta2O5, in the first embodiment, the unnecessary waves are also suppressed compared with the first comparative example and the second comparative example. As described above, in the first embodiment, when the mass-added film is provided in the edge region and the gap region, the unnecessary waves can be suppressed near the resonant frequency or near the antiresonant frequency. In addition, the transverse mode can also be suppressed.

[0098] The material of the band-shaped mass adding film and the granular mass adding film is not limited to SiO 2 and Ta 2 O 5 . The material of the band-shaped mass adding film and the granular mass adding film may include at least one material selected from the group consisting of silicon oxide, tantalum oxide, niobium oxide, tungsten oxide, and hafnium oxide.

[0099] In the first embodiment, the piezoelectric layer 14, the electrode fingers, and the strip-shaped mass adding film are sequentially stacked in the portion where the strip-shaped mass adding film and the electrode fingers are stacked. However, the piezoelectric layer 14, the strip-shaped mass adding film, and the electrode fingers may be sequentially stacked in this portion.

[0100] In the first embodiment, the piezoelectric layer 14, the electrode fingers, and the granular mass adding film are sequentially stacked in the portion where the granular mass adding film and the electrode fingers are stacked. However, the piezoelectric layer 14, the granular mass adding film, and the electrode fingers may be sequentially stacked in this portion.

[0101] The granular mass-adding film may overlap with one or more electrode fingers in a plan view. Fig. 9 In the first modification of the first embodiment shown, the first granular mass addition film 25A overlaps with a pair of adjacent first electrode fingers 28 and second electrode fingers 29 in a plan view. When a pair of adjacent first electrode fingers 28 and second electrode fingers 29 is set as a pair of electrode finger pairs, a portion of the region between the two adjacent pairs of electrode finger pairs does not overlap with the first granular mass addition film 25A in a plan view.

[0102] The second granular mass addition film 25B overlaps with a pair of adjacent first electrode fingers 28 and second electrode fingers 29 in a plan view. A portion of the region between two adjacent pairs of electrode fingers does not overlap with the second granular mass addition film 25B in a plan view. Like these, the first granular mass addition film 25A and the second granular mass addition film 25B are provided so as not to overlap with at least a portion of the region between at least one adjacent electrode finger in a plan view.

[0103] In this modification, both the strip-shaped mass addition film and the granular mass addition film are provided as in the first embodiment. This makes it possible to suppress unnecessary waves near the resonance frequency or the anti-resonance frequency.

[0104] However, the granular mass addition film preferably overlaps only one electrode finger in a plan view. In this case, in a plan view, the granular mass addition film is not located in at least a portion of the region between any electrode fingers in the edge region. This makes it possible to more reliably suppress unnecessary waves.

[0105] In the first embodiment, the band-shaped mass-added film is provided only in the gap region. Fig.10In the second modification of the first embodiment shown, the first strip-shaped mass-adding film 24A reaches the portion overlapping the first bus bar 26 in a plan view from the first gap region G1. The second strip-shaped mass-adding film 24B also reaches the portion overlapping the second bus bar 27 in a plan view from the second gap region G2. However, it is sufficient that the strip-shaped mass-adding film provided in at least one of the pair of gap regions reaches the portion overlapping the bus bar adjacent to the gap region in a plan view from the gap region.

[0106] In this modification, both the strip-shaped mass addition film and the granular mass addition film are provided as in the first embodiment. This makes it possible to suppress unnecessary waves near the resonance frequency or the anti-resonance frequency.

[0107] In this modification, the piezoelectric layer 14, the bus bar, and the strip-shaped mass-adding film are stacked in the portion where the strip-shaped mass-adding film and the bus bar are stacked. Alternatively, the piezoelectric layer 14, the strip-shaped mass-adding film, and the bus bar may be stacked in the portion where the strip-shaped mass-adding film and the bus bar are stacked.

[0108] return Figure 1 When the dimension of the strip-shaped mass adding film along the electrode finger extending direction is set as the width of the strip-shaped mass adding film, in the first embodiment, the width of the first strip-shaped mass adding film 24A is fixed. Similarly, the width of the second strip-shaped mass adding film 24B is fixed. However, this is not limited to this.

[0109] Fig.11 It is a schematic plan view of an elastic wave device according to a second embodiment.

[0110] The present embodiment differs from the first embodiment in that the width of the strip-shaped mass adding film is not constant and the dimension of the granular mass adding film along the electrode finger extending direction is not constant. Elastic wave device 30 of the present embodiment has the same structure as elastic wave device 10 of the first embodiment except for the above points.

[0111] The IDT electrode 11 includes a plurality of pairs of first electrode fingers 28 and second electrode fingers 29. When a region including only one pair of first electrode fingers 28 and second electrode fingers 29 is defined as an electrode finger pair region N, a plurality of electrode finger pair regions N are defined in the elastic wave device 30. The boundary between adjacent electrode finger pair regions N is defined as the center of the first electrode finger 28 of one electrode finger pair region N and the second electrode finger 29 of another electrode finger pair region N in the orthogonal direction of the electrode fingers.

[0112] The first strip-shaped mass-adding film 34A has a plurality of step portions 34a. In the present embodiment, the step portions 34a extend in the electrode finger extension direction. The first strip-shaped mass-adding film 34A has a structure in which portions having different widths are connected to each other. In the first strip-shaped mass-adding film 34A, the step portions 34a are boundaries between portions having different widths. The width of each portion of the first strip-shaped mass-adding film 34A, which is bounded by the step portions 34a, is constant.

[0113] Here, the plurality of first electrode fingers 28 each have a first edge portion 28a and a second edge portion 28b. Specifically, the first edge portion 28a and the second edge portion 28b are edge portions of the first electrode finger 28 when viewed from above. The first edge portion 28a and the second edge portion 28b of each first electrode finger 28 are opposed to each other in the electrode finger orthogonal direction. Similarly, the plurality of second electrode fingers 29 each have a first edge portion 29a and a second edge portion 29b.

[0114] The step portions 34a of the first strip-shaped mass adding film 34A are respectively located at portions overlapping with the first edge portions 28a of the first electrode fingers 28 in a plan view. Therefore, the width of the first strip-shaped mass adding film 34A is constant at portions overlapping with the regions between the first edge portions 28a of the adjacent first electrode fingers 28 in a plan view.

[0115] In the following, when the area of ​​the strip-shaped mass-adding film is recorded, unless otherwise specified, the area refers to the area of ​​the strip-shaped mass-adding film when viewed from above. When the area of ​​the granular mass-adding film is recorded, unless otherwise specified, the area refers to the area of ​​the granular mass-adding film when viewed from above.

[0116] like Fig.11 As shown in FIG. 1 , the step portion 34a of the first band-shaped mass adding film 34A is located in each electrode finger pair region N. As the width of the first band-shaped mass adding film 34A increases stepwise from one side to the other side in the orthogonal direction of the electrode fingers, with each step portion 34a as a boundary. Therefore, the area of ​​the first band-shaped mass adding film 34A is different from each other in all the electrode finger pair regions N.

[0117] The first band-shaped mass adding film 34A and the plurality of first granular mass adding films 35A are integrally formed of the same material. Furthermore, the first band-shaped mass adding film 34A reaches the edge portion of the first gap region G1 on the first bus bar 26 side in the electrode finger extending direction. Therefore, the narrower the width of the first band-shaped mass adding film 34A, the larger the size of the first granular mass adding film 35A along the electrode finger extending direction.

[0118] In addition, in one electrode finger pair region N, the dimension of the first band-shaped mass adding film 34A along the direction orthogonal to the electrode fingers is larger than the dimension of the first granular mass adding film 35A along the direction orthogonal to the electrode fingers. Therefore, in one electrode finger pair region N, the wider the width of the first band-shaped mass adding film 34A, the larger the total area of ​​the first band-shaped mass adding film 34A and the first granular mass adding film 35A. Therefore, when the total area of ​​the first band-shaped mass adding film 34A and the first granular mass adding film 35A in one electrode finger pair region N is set as the first additional film total area, the first additional film total area is different from each other in all electrode finger pair regions N.

[0119] Similarly, the second band-shaped mass adding film 34B also has a plurality of step portions 34b. The step portions 34b are respectively located in the portion overlapping with the second edge portion 29b of the second electrode finger 29 in a plan view. Therefore, the width of the second band-shaped mass adding film 34B in the portion overlapping with the region between the second edge portions 29b of the adjacent second electrode fingers 29 in a plan view is constant.

[0120] The step portion 34b of the second band-shaped mass adding film 34B is located in each electrode finger pair region N. As the width of the second band-shaped mass adding film 34B increases stepwise from one side to the other side in the orthogonal direction of the electrode fingers, with each step portion 34b as a boundary. Therefore, the area of ​​the second band-shaped mass adding film 34B is different from each other in all the electrode finger pair regions N.

[0121] The second band-shaped mass adding film 34B and the plurality of second granular mass adding films 35B are integrally formed of the same material. Furthermore, the second band-shaped mass adding film 34B reaches the end edge of the second gap region G2 on the side of the second bus bar 27 in the electrode finger extending direction. Therefore, the narrower the width of the second band-shaped mass adding film 34B, the larger the size of the second granular mass adding film 35B along the electrode finger extending direction.

[0122] In one electrode finger pair region N, the dimension of the second band-shaped mass adding film 34B along the direction orthogonal to the electrode fingers is larger than the dimension of the second granular mass adding film 35B along the direction orthogonal to the electrode fingers. Therefore, in one electrode finger pair region N, the wider the width of the second band-shaped mass adding film 34B, the larger the total area of ​​the second band-shaped mass adding film 34B and the second granular mass adding film 35B. Therefore, when the total area of ​​the second band-shaped mass adding film 34B and the second granular mass adding film 35B in one electrode finger pair region N is set as the second additional film total area, the second additional film total area is different from each other in all electrode finger pair regions N.

[0123] The elastic wave device 30 is an elastic wave resonator using a thickness shear mode body wave. In the elastic wave device 30, a portion of the piezoelectric layer 14 provided with a pair of first electrode fingers 28 and second electrode fingers 29 functions as a resonator. Therefore, the structure of the elastic wave device 30 is equivalent to a structure in which a resonator is arranged in each electrode finger pair region N. Furthermore, the structure of the elastic wave device 30 is equivalent to a structure in which a plurality of such resonators are connected in parallel.

[0124] In this embodiment, the total area of ​​the first additional film and the total area of ​​the second additional film are different from each other in the electrode finger pair regions N. Therefore, the frequency of the unnecessary wave generated in each electrode finger pair region is different. In this way, the frequency of the unnecessary wave can be dispersed. Therefore, the unnecessary wave can be effectively suppressed near the resonant frequency or near the anti-resonant frequency.

[0125] In addition, in the case of an elastic wave device using surface acoustic waves, the surface acoustic waves are excited in a region including the entirety of a plurality of electrode fingers. In contrast, the structure of the elastic wave device 30 is equivalent to a structure in which the resonators arranged in the regions of each electrode finger pair are connected in parallel as described above. Therefore, even if the total area of ​​the first additional film and the total area of ​​the second additional film are different, the waveform in the frequency characteristics of the elastic wave device 30 is not easily collapsed. That is, it is possible to suppress unnecessary waves without deteriorating the electrical characteristics.

[0126] In addition, the manner in which the width of the strip-shaped mass-adding film changes is not limited to the above. For example, the position of the step portion of the strip-shaped mass-adding film may not overlap with the first end edge portion or the second end edge portion of the electrode finger in a plan view. The step portion may also extend in a direction intersecting the extending direction of the electrode finger.

[0127] The total area of ​​the first additional film in at least one electrode finger pair region N may be different from the total area of ​​the first band-shaped mass additional film 24A and the first granular mass additional film 35A in other electrode finger pair regions N. Alternatively, the total area of ​​the second additional film in at least one electrode finger pair region N may be different from the total area of ​​the second additional film in other electrode finger pair regions N. In these cases, as in the second embodiment, it is possible to effectively suppress unnecessary waves near the resonant frequency or near the antiresonant frequency.

[0128] In the first and second embodiments, the granular mass addition film is stacked on the front end of the electrode finger. Moreover, in the portion where the granular mass addition film and the electrode finger are stacked, the piezoelectric layer 14, the electrode finger, and the granular mass addition film are stacked in sequence. However, this is not limited to this. Hereinafter, the third to fifth embodiments will be used to illustrate examples in which the structure of the granular mass addition film is different from that of the first and second embodiments.

[0129] The elastic wave devices of the third to fifth embodiments have the same structure as the elastic wave device 10 of the first embodiment except for the granular mass addition film. That is, in the third to fifth embodiments, both the strip-shaped mass addition film and the granular mass addition film are provided. Therefore, in the third to fifth embodiments, even when the mass addition film is provided in the edge region and the gap region, as in the first embodiment, it is possible to suppress unnecessary waves near the resonant frequency or near the antiresonant frequency.

[0130] Fig.12 It is a schematic plan view of an elastic wave device according to a third embodiment.

[0131] In the present embodiment, the first granular mass addition film 45A surrounds the front end of the second electrode finger 29 in three directions in a plan view. The first granular mass addition film 45A is in contact with the second electrode finger 29. However, the first granular mass addition film 45A does not overlap with the second electrode finger 29 in a plan view. The shape of the first granular mass addition film 45A in a plan view is a U-shape.

[0132] More specifically, the plurality of electrode fingers have a first surface 11a and a second surface 11b, and a side surface 11c. The first surface 11a and the second surface 11b are opposed to each other in the thickness direction. Of the first surface 11a and the second surface 11b, the second surface 11b is a surface on the side of the piezoelectric layer 14. The side surface 11c is connected to the first surface 11a and the second surface 11b. The first granular mass addition film 45A is in contact with the side surface 11c of the second electrode finger 29.

[0133] In a plan view, a portion of the first granular mass addition film 45A located in the first gap region G1 is located on an extension line of the second electrode finger 29 .

[0134] Similarly, the second granular mass addition film 45B surrounds the front end of the first electrode finger 28 in three directions in a plan view. The second granular mass addition film 45B is in contact with the side surface 11c of the first electrode finger 28. However, the second granular mass addition film 45B does not overlap with the first electrode finger 28 in a plan view. The shape of the second granular mass addition film 45B in a plan view is a U-shape. In a plan view, the portion of the second granular mass addition film 45B located in the second gap region G2 is located on the extension line of the first electrode finger 28.

[0135] Furthermore, the plurality of granular mass adding films may include at least one granular mass adding film surrounding the tip end portions of the electrode fingers in three directions in a plan view.

[0136] In this embodiment, the granular mass adding film does not overlap with the tip end of the electrode finger in a plan view. As a result, the mass added to the tip end of the electrode finger is reduced. As a result, the power resistance of the elastic wave device can be improved.

[0137] Fig.13 It is a schematic plan view of an elastic wave device according to a fourth embodiment.

[0138] In the present embodiment, the first granular mass addition film 45A surrounds the front end of the second electrode finger 29 in three directions in a plan view. However, the first granular mass addition film 45A does not contact the side surface 11c of the second electrode finger 29. Moreover, the first granular mass addition film 45A does not overlap the second electrode finger 29 in a plan view. In a plan view, the portion of the first granular mass addition film 45A located in the first gap region G1 is located on the extension line of the second electrode finger 29.

[0139] Similarly, the second granular mass addition film 45B surrounds the front end of the first electrode finger 28 in three directions in a plan view. The second granular mass addition film 45B does not contact the side surface 11c of the first electrode finger 28. Moreover, the second granular mass addition film 45B does not overlap with the first electrode finger 28 in a plan view. In a plan view, the portion of the second granular mass addition film 45B located in the second gap region G2 is located on the extension line of the first electrode finger 28.

[0140] In this embodiment as well, similarly to the third embodiment, the power handling capability of the elastic wave device can be improved.

[0141] Fig.14 It is a schematic plan view of an elastic wave device according to a fifth embodiment.

[0142] In this embodiment, the first granular mass addition film 25A overlaps the tip of the second electrode finger 29 in a plan view. Specifically, in the portion where the first granular mass addition film 25A and the second electrode finger 29 are stacked, the piezoelectric layer 14, the first granular mass addition film 25A, and the second electrode finger 29 are stacked in this order.

[0143] Similarly, the second granular mass addition film 25B overlaps the front end of the first electrode finger 28 in a plan view. Specifically, in the portion where the second granular mass addition film 25B and the first electrode finger 28 are stacked, the piezoelectric layer 14, the second granular mass addition film 25B and the first electrode finger 28 are stacked in this order.

[0144] In this embodiment, a granular mass addition film is provided between the piezoelectric layer 14 and the tip of the electrode finger. This can suppress the electric field applied to the electrode finger, thereby improving the power handling capability of the elastic wave device.

[0145] Fig.15 It is a schematic plan view of an elastic wave device according to the sixth embodiment.

[0146] The present embodiment is different from the first embodiment in that the band-shaped mass-adding film and the plurality of granular mass-adding films located in the same gap region are provided independently of each other. The band-shaped mass-adding film and the plurality of granular mass-adding films are not in contact with each other. Except for the above aspects, the elastic wave device of the present embodiment has the same structure as the elastic wave device 10 of the first embodiment.

[0147] The first band-shaped mass adding film 24A and the first granular mass adding films 25A are opposed to each other with a gap therebetween. In addition, the first granular mass adding films 25A are provided over the first gap region G1 and the first edge region E1. Therefore, the gap between the first band-shaped mass adding film 24A and the first granular mass adding films 25A is located in the first gap region G1.

[0148] The second band-shaped mass adding film 24B and each second granular mass adding film 25B are opposed to each other with a gap therebetween. Each second granular mass adding film 25B is provided over the second gap region G2 and the second edge region E2. Therefore, the gap between the second band-shaped mass adding film 24B and each second granular mass adding film 25B is located in the second gap region G2. In the present embodiment, the material of the band-shaped mass adding film and the material of the granular mass adding film are the same.

[0149] In this embodiment, as in the first embodiment, when the mass-added films are provided in the edge region and the gap region, it is possible to suppress unnecessary waves in the vicinity of the resonance frequency or the vicinity of the antiresonance frequency.

[0150] Furthermore, the structure in which the strip-shaped mass adding film and the plurality of granular mass adding films located in the same gap region are independently provided can also be applied to other aspects of the present invention.

[0151] Fig.16 It is a schematic plan view of an elastic wave device according to the seventh embodiment.

[0152] The present embodiment is different from the first embodiment in that a dielectric film 53 is provided on the piezoelectric layer 14. Except for the above-described point, the elastic wave device of the present embodiment has the same structure as the elastic wave device 10 of the first embodiment.

[0153] The dielectric film 53 is provided on the first main surface 14 a of the piezoelectric layer 14 so as to cover the IDT electrode 11 , the first band-shaped mass adding film 24A, the plurality of first granular mass adding films 25A, the second band-shaped mass adding film 24B, and the plurality of second granular mass adding films 25B.

[0154] The piezoelectric layer 14, the strip-shaped mass adding film and the dielectric film 53 are sequentially stacked in the stacked portion. The piezoelectric layer 14, the granular mass adding film and the dielectric film 53 are sequentially stacked in the stacked portion.

[0155] In this embodiment, both the strip-shaped mass addition film and the granular mass addition film are provided. Thus, similarly to the first embodiment, when the mass addition films are provided in the edge region and the gap region, unnecessary waves can be suppressed near the resonance frequency or the antiresonance frequency.

[0156] Furthermore, IDT electrode 11 is protected by dielectric film 53 . Thus, IDT electrode 11 is not easily damaged. Furthermore, the frequency of the elastic wave device can be easily adjusted by adjusting the thickness of dielectric film 53 .

[0157] For example, silicon oxide, silicon nitride, or silicon oxynitride can be used for the dielectric film 53. However, the material of the dielectric film 53 is not limited to the above.

[0158] The order of laminating the strip-shaped mass adding film, the granular mass adding film, and the dielectric film 53 is not limited to the above. Fig.17 In the modified example of the seventh embodiment shown, a dielectric film 53 is provided on the first main surface 14a of the piezoelectric layer 14 so as to cover the IDT electrode 11. A first band-shaped mass adding film 54A, a plurality of first granular mass adding films 55A, a second band-shaped mass adding film 54B, and a plurality of second granular mass adding films 55B are provided on the dielectric film 53.

[0159] The first band-shaped mass adding film 54A is provided in the first gap region G1. The first band-shaped mass adding film 54A is provided continuously so as to overlap with the plurality of first electrode fingers 28 and the plurality of second electrode fingers 29 and the region between the electrode fingers in a plan view. The plurality of first granular mass adding films 55A are provided over the first edge region E1 and the first gap region G1, respectively.

[0160] The second band-shaped mass adding film 54B is provided in the second gap region G2. The second band-shaped mass adding film 54B is provided continuously so as to overlap with the plurality of first electrode fingers 28 and the plurality of second electrode fingers 29 and the region between the electrode fingers in a plan view. The plurality of second granular mass adding films 55B are provided over the second edge region E2 and the second gap region G2, respectively.

[0161] In the portion where the strip-shaped mass adding film and the dielectric film 53 are stacked, the piezoelectric layer 14, the dielectric film 53, and the strip-shaped mass adding film are stacked in sequence. In the portion where the granular mass adding film and the dielectric film 53 are stacked, the piezoelectric layer 14, the dielectric film 53, and the granular mass adding film are stacked in sequence. In this case, as in the seventh embodiment, it is possible to suppress unnecessary waves near the resonance frequency or near the antiresonance frequency.

[0162] In this variant, the strip-shaped mass-adding film is not in contact with a plurality of electrode fingers connected to different potentials. In this case, the strip-shaped mass-adding film may also include a metal. The plurality of granular mass-adding films are not electrically connected to a plurality of electrode fingers connected to different potentials. In this case, the plurality of granular mass-adding films may also include a metal. However, in this variant, the strip-shaped mass-adding film and the plurality of granular mass-adding films may also include a dielectric.

[0163] The elastic wave device according to the present invention can be used in, for example, a filter device. This example is shown below.

[0164] Fig.18 This is a circuit diagram of a filter device according to an eighth embodiment of the present invention.

[0165] The filter device 60 is a ladder filter. The filter device 60 has a first signal terminal 62 and a second signal terminal 63, and a plurality of series arm resonators and a plurality of parallel arm resonators. In the present embodiment, all the series arm resonators and all the parallel arm resonators are elastic wave resonators. Moreover, all the elastic wave resonators are elastic wave devices according to the present invention. However, at least one of the series arm resonators and the parallel arm resonators in the filter device 60 may be an elastic wave device according to the present invention having any structure of the first to seventh embodiments.

[0166] The first signal terminal 62 and the second signal terminal 63 may be configured as, for example, electrode pads or wiring. In the present embodiment, the second signal terminal 63 is an antenna terminal. The antenna terminal is connected to an antenna.

[0167] The plurality of series arm resonators of the filter device 60 are specifically series arm resonators S1, S2, S3, and S4. The plurality of parallel arm resonators are specifically parallel arm resonators P1, P2, and P3.

[0168] The series arm resonator S1, the series arm resonator S2, the series arm resonator S3, and the series arm resonator S4 are connected in series between the first signal terminal 62 and the second signal terminal 63. The parallel arm resonator P1 is connected between the connection point between the series arm resonator S1 and the series arm resonator S2 and the ground potential. The parallel arm resonator P2 is connected between the connection point between the series arm resonator S2 and the series arm resonator S3 and the ground potential. The parallel arm resonator P3 is connected between the connection point between the series arm resonator S3 and the series arm resonator S4 and the ground potential.

[0169] However, the circuit configuration of the filter device 60 is not limited to the above. When the filter device 60 according to the present invention is a ladder-type filter, the filter device 60 may include at least one series arm resonator and at least one parallel arm resonator.

[0170] Alternatively, the filter device 60 may include, for example, a longitudinally coupled resonator type elastic wave filter. In this case, the filter device 60 may include, for example, a series arm resonator or a parallel arm resonator connected to the longitudinally coupled resonator type elastic wave filter. The series arm resonator or the parallel arm resonator may be the elastic wave device according to the present invention.

[0171] The antiresonance frequency of the parallel arm resonator constituting the passband of the filter device 60 is located within the passband of the filter device 60. Therefore, the influence of the unnecessary waves generated near the antiresonance frequency in the parallel arm resonator on the electrical characteristics in the passband of the filter device 60 is large. The resonant frequency of the series arm resonator constituting the passband of the filter device 60 is located within the passband of the filter device 60. Therefore, the influence of the unnecessary waves generated near the resonant frequency in the series arm resonator on the electrical characteristics in the passband of the filter device 60 is also large.

[0172] In the present embodiment, each parallel arm resonator and each series arm resonator are elastic wave devices according to the present invention. Therefore, even when each elastic wave resonator of the filter device 60 is configured with a mass-added film in the edge region and the gap region, it is possible to suppress unnecessary waves near the resonant frequency or the antiresonant frequency.

[0173] Furthermore, for each parallel arm resonator of the filter device 60, for example, an elastic wave device capable of suppressing useless waves near the antiresonance frequency may be used. For each series arm resonator, for example, an elastic wave device capable of suppressing useless waves near the resonant frequency may be used. Thus, the influence of useless waves on the electrical characteristics within the passband of the filter device 60 can be suppressed. Furthermore, when the elastic wave device of the first embodiment and the like is used for the series arm resonator or the parallel arm resonator, the degradation of the loss can also be suppressed in the elastic wave resonator. Therefore, the degradation of the filter characteristics of the filter device 60 can be suppressed.

[0174] A ninth embodiment is described below, which is different from the eighth embodiment in the structure of each elastic wave resonator. The ninth embodiment has the same circuit structure as the eighth embodiment. Therefore, the same reference numerals and drawings as those used in the eighth embodiment are used in the description of the ninth embodiment.

[0175] The plurality of elastic wave resonators of the filter device according to the ninth embodiment include first to fifth elastic wave resonators. The first elastic wave resonator is an elastic wave device according to the present invention. The first elastic wave resonator has, for example, any of the structures of the first to seventh embodiments. The second to fifth elastic wave resonators are not elastic wave devices according to the present invention.

[0176] Continue to use Fig.18 The series arm resonator S1 shown is the third elastic wave resonator. The series arm resonator S2 is the first elastic wave resonator. The series arm resonator S3 is the fifth elastic wave resonator. The series arm resonator S4 is the fourth elastic wave resonator. The parallel arm resonator P1 is the third elastic wave resonator. The parallel arm resonator P2 is the second elastic wave resonator. The parallel arm resonator P3 is the fourth elastic wave resonator. In addition, the circuit configuration of the first to fifth elastic wave resonators is not limited to the above.

[0177] In the present embodiment, all elastic wave resonators share a piezoelectric substrate. The specific structures of the second to fifth elastic wave resonators are described below.

[0178] Fig.19 FIG. 1 is a schematic plan view of a second elastic wave resonator according to the ninth embodiment. Fig. 20 FIG. 1 is a schematic plan view of a third elastic wave resonator according to the ninth embodiment. Fig.21 FIG. 1 is a schematic plan view of a fourth elastic wave resonator according to the ninth embodiment. Fig. 22 FIG. 1 is a schematic plan view of a fifth elastic wave resonator according to the ninth embodiment.

[0179] like Fig.19 As shown, second elastic wave resonator 71B includes piezoelectric substrate 12. Second elastic wave resonator 71B shares piezoelectric substrate 12 with the first elastic wave resonator. Figure 20 to Figure 22 Third elastic wave resonator 71C, fourth elastic wave resonator 71D, and fifth elastic wave resonator 71E each include piezoelectric substrate 12. Third elastic wave resonator 71C, fourth elastic wave resonator 71D, and fifth elastic wave resonator 71E share piezoelectric substrate 12 with the first elastic wave resonator.

[0180] Alternatively, the second elastic wave resonator 71B, the third elastic wave resonator 71C, the fourth elastic wave resonator 71D, and the fifth elastic wave resonator 71E may have piezoelectric substrates independently of the first elastic wave resonator. In this case, the piezoelectric substrates of the respective resonators may be configured similarly to the piezoelectric substrate 12 of the elastic wave device 10 according to the first embodiment. Figure 2 As shown, the piezoelectric substrate 12 may include a supporting member 13 and a piezoelectric layer 14 .

[0181] like Fig.19 As shown, the second elastic wave resonator 71B includes an IDT electrode 11. The IDT electrode 11 is provided on a piezoelectric substrate 12. The IDT electrode 11 includes a pair of bus bars and a plurality of electrode fingers. The IDT electrode 11 is configured similarly to the IDT electrode 11 of the elastic wave device 10 according to the first embodiment.

[0182] Specifically, the IDT electrode 11 of the second elastic wave resonator 71B has a pair of bus bars and a plurality of electrode fingers. The pair of bus bars is more specifically a first bus bar 26 and a second bus bar 27. The first bus bar 26 and the second bus bar 27 are opposed to each other. The plurality of electrode fingers is more specifically a plurality of first electrode fingers 28 and a plurality of second electrode fingers 29. One end of each of the plurality of first electrode fingers 28 is connected to the first bus bar 26, respectively. One end of each of the plurality of second electrode fingers 29 is connected to the second bus bar 27, respectively. The plurality of first electrode fingers 28 and the plurality of second electrode fingers 29 are interlaced with each other.

[0183] Similarly, in Figure 20 to Figure 22 In the third elastic wave resonator 71C, the fourth elastic wave resonator 71D, and the fifth elastic wave resonator 71E shown in the figure, the IDT electrode 11 is also provided on the piezoelectric substrate 12. The IDT electrode 11 of each of the third elastic wave resonator 71C, the fourth elastic wave resonator 71D, and the fifth elastic wave resonator 71E is also configured similarly to the IDT electrode 11 of the elastic wave device 10 of the first embodiment.

[0184] Alternatively, the design parameters of IDT electrodes 11 of first elastic wave resonator 71B, second elastic wave resonator 71C, third elastic wave resonator 71C, fourth elastic wave resonator 71D, and fifth elastic wave resonator 71E may be different from one another depending on desired electrical characteristics.

[0185] like Fig.19 As shown in FIG. 1 , the second elastic wave resonator 71B has an intersection region F and a pair of gap regions similar to the elastic wave device 10 of the first embodiment.

[0186] Specifically, in the second elastic wave resonator 71B, when the IDT electrode 11 is viewed from a direction perpendicular to the direction in which the plurality of electrode fingers extend, a region where adjacent electrode fingers overlap each other is an intersection region F. The intersection region F includes a central region H and a pair of edge regions. More specifically, the pair of edge regions are a first edge region E1 and a second edge region E2. The first edge region E1 and the second edge region E2 are arranged to sandwich the central region H in the direction in which the plurality of electrode fingers extend. The first edge region E1 is located on the first bus bar 26 side. The second edge region E2 is located on the second bus bar 27 side.

[0187] In the second elastic wave resonator 71B, the region between the intersection region F and the pair of bus bars is a pair of gap regions. Specifically, the pair of gap regions is a first gap region G1 and a second gap region G2. The first gap region G1 is located between the first bus bar 26 and the first edge region E1. The second gap region G2 is located between the second bus bar 27 and the second edge region E2.

[0188] Likewise, Figure 20 to Figure 22 The third elastic wave resonator 71C, the fourth elastic wave resonator 71D, and the fifth elastic wave resonator 71E shown also have the intersection region F, the first gap region G1, and the second gap region G2, respectively. Figure 20 to Figure 22 The intersection region F of the third elastic wave resonator 71C, the fourth elastic wave resonator 71D, and the fifth elastic wave resonator 71E shown includes a central region H, a first edge region E1, and a second edge region E2.

[0189] As described above, second elastic wave resonator 71B, third elastic wave resonator 71C, fourth elastic wave resonator 71D, and fifth elastic wave resonator 71E include piezoelectric substrate 12 and IDT electrode 11. Each of these elastic wave resonators includes intersection region F and a pair of gap regions. However, each of these elastic wave resonators differs from each other in the structure of the mass-added film.

[0190] like Fig.19 As shown, second elastic wave resonator 71B does not have a mass-added film. Therefore, second elastic wave resonator 71B does not have a mass-added film corresponding to the strip-shaped mass-added film and the granular mass-added film in the first elastic wave resonator.

[0191] like Fig. 20 As shown, third elastic wave resonator 71C does not have a mass addition film equivalent to the granular mass addition film of the first elastic wave resonator. On the other hand, third elastic wave resonator 71C has a strip-shaped mass addition film independently of the first elastic wave resonator.

[0192] In the third elastic wave resonator 71C, the first strip-shaped mass adding film 24A is provided in the first gap region G1. On the other hand, the second strip-shaped mass adding film 24B is provided in the second gap region G2. The first strip-shaped mass adding film 24A and the second strip-shaped mass adding film 24B are not provided in the intersection region F. The first strip-shaped mass adding film 24A and the second strip-shaped mass adding film 24B are provided continuously so as to overlap with the plurality of electrode fingers and the regions between the electrode fingers in a plan view.

[0193] In third elastic wave resonator 71C, the strip-shaped mass adding film may be provided in at least one of the pair of gap regions and not provided in intersection region F. The strip-shaped mass adding film may be provided continuously so as to overlap with the plurality of electrode fingers and the regions between the electrode fingers in plan view.

[0194] like Fig.21 As shown, fourth elastic wave resonator 71D does not have a mass addition film equivalent to the strip-shaped mass addition film of the first elastic wave resonator. On the other hand, fourth elastic wave resonator 71D has a plurality of granular mass addition films independently of the first elastic wave resonator.

[0195] In the fourth elastic wave resonator 71D, a plurality of first granular mass addition films 25A are provided over the first gap region G1 and the first edge region E1. On the other hand, a plurality of second granular mass addition films 25B are provided over the second gap region G2 and the second edge region E2. The plurality of first granular mass addition films 25A and the plurality of second granular mass addition films 25B each overlap one electrode finger in a plan view.

[0196] In fourth elastic wave resonator 71D, a plurality of granular mass adding films may be provided over at least one gap region among a pair of gap regions and an edge region adjacent to the gap region. The plurality of granular mass adding films may be provided so as not to overlap at least a portion of a region between at least one adjacent electrode finger in a plan view. The granular mass adding film may overlap one or less electrode fingers in a plan view, or may overlap one or more electrode fingers.

[0197] When the granular mass adding film does not overlap with the electrode fingers in a plan view, it is preferred that a portion of the granular mass adding film provided in the gap region is located on an extension line of the electrode fingers in a plan view.

[0198] like Fig. 22 As shown, fifth elastic wave resonator 71E does not have a mass addition film equivalent to the granular mass addition film in the first elastic wave resonator. On the other hand, the fifth elastic wave resonator has a strip-shaped mass addition film independently of the first elastic wave resonator.

[0199] In the fifth elastic wave resonator 71E, a first strip-shaped mass adding film 74A is provided over the first gap region G1 and the first edge region E1. On the other hand, a second strip-shaped mass adding film 74B is provided over the second gap region G2 and the second edge region E2. The first strip-shaped mass adding film 74A and the second strip-shaped mass adding film 74B are provided continuously so as to overlap with the plurality of electrode fingers and the regions between the electrode fingers in a plan view.

[0200] In fifth elastic wave resonator 71E, the strip-shaped mass-adding film may be provided over at least one of the pair of gap regions and an edge region adjacent to the gap region. The strip-shaped mass-adding film may be provided continuously so as to overlap with the plurality of electrode fingers and the region between the electrode fingers in a plan view.

[0201] The filter device of the ninth embodiment includes the elastic wave device according to the present invention as the first elastic wave resonator. Therefore, even when the first elastic wave resonator of the filter device is configured with mass-added films in the edge region and the gap region, it is possible to suppress unnecessary waves near the resonance frequency or the antiresonance frequency.

[0202] Furthermore, the first elastic wave resonator, the second elastic wave resonator 71B, the third elastic wave resonator 71C, the fourth elastic wave resonator 71D, and the fifth elastic wave resonator 71E have different structures of the mass-added films. Thus, in the ninth embodiment, the frequencies of the generated unnecessary waves can be dispersed. Thus, the unnecessary waves can be effectively suppressed.

[0203] In the present embodiment, the first elastic wave resonator 71B, the third elastic wave resonator 71C, the fourth elastic wave resonator 71D, and the fifth elastic wave resonator 71E are configured to utilize bulk waves in a thickness shear mode. In any of these elastic wave resonators, d / p is preferably 0.5 or less.

[0204] The series arm resonator or the parallel arm resonator of the filter device may include at least one first elastic wave resonator. Furthermore, the series arm resonator and the parallel arm resonator of the filter device may include at least one second elastic wave resonator 71B, third elastic wave resonator 71C, fourth elastic wave resonator 71D, or fifth elastic wave resonator 71E. In this case, the frequency of the generated unnecessary waves can be dispersed.

[0205] The thickness shear mode will be described in detail below. In addition, the "electrode" in the IDT electrode described below corresponds to the electrode finger in the present invention. The support member in the following example corresponds to the support substrate in the present invention.

[0206] Fig.23(a) is a schematic perspective view showing the appearance of an elastic wave device using a thickness shear mode bulk wave, Fig.23 (b) is a top view showing the electrode structure on the piezoelectric layer. Fig.24 It is along Fig.23 (a) is a cross-sectional view of a portion taken along line AA.

[0207] The elastic wave device 1 has a piezoelectric layer 2 containing LiNbO3. The piezoelectric layer 2 may also contain LiTaO3. The cutting angle of LiNbO3 and LiTaO3 is Z-cut, but it may also be a rotated Y-cut or X-cut. The thickness of the piezoelectric layer 2 is not particularly limited, but in order to effectively excite the thickness shear mode, it is preferably greater than 40nm and less than 1000nm, and more preferably greater than 50nm and less than 1000nm. The piezoelectric layer 2 has a first principal surface 2a and a second principal surface 2b facing each other. An electrode 3 and an electrode 4 are provided on the first principal surface 2a. Here, electrode 3 is an example of a "first electrode", and electrode 4 is an example of a "second electrode". In Fig.23 (a) and Fig.23 In (b), the plurality of electrodes 3 are a plurality of first electrode fingers connected to the first bus bar 5. The plurality of electrodes 4 are a plurality of second electrode fingers connected to the 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 all directions intersecting with the thickness direction of the piezoelectric layer 2. Therefore, it can also be said that the electrode 3 and the adjacent electrode 4 are opposed to each other in a direction intersecting with the thickness direction of the piezoelectric layer 2. In addition, the length directions of the electrodes 3 and 4 can also be orthogonal to the length directions of the electrodes 3 and 4. Fig.23 (a) and Fig.23 The direction perpendicular to the length direction of the electrodes 3 and 4 shown in (b) is changed. Fig.23 (a) and Fig.23 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.23 (a) and Fig.23(b) becomes extended in the direction in which electrodes 3 and 4 extend. Moreover, a pair of structures in which an electrode 3 connected to one potential and an electrode 4 connected to another potential are adjacent are provided with multiple pairs in a direction orthogonal to the length direction of the electrodes 3 and 4. Here, the so-called electrode 3 and electrode 4 are adjacent does not mean that the electrodes 3 and electrode 4 are arranged in direct contact, but refers to the case where the electrodes 3 and electrode 4 are arranged with a gap. 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 arranged 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 of 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.

[0208] In addition, in the elastic wave device 1, since a Z-cut piezoelectric layer is used, the direction perpendicular to the length direction of the electrodes 3 and 4 becomes a direction perpendicular to the polarization direction of the piezoelectric layer 2. In the case where a piezoelectric body with another cutting angle is used as the piezoelectric layer 2, this 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 perpendicular to the length direction of the electrodes 3 and 4 and the polarization direction is, for example, within the range of 90°±10°).

[0209] 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 8 have a frame-like shape. Fig.24 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 may be directly or indirectly stacked on the second main surface 2b of the piezoelectric layer 2.

[0210] 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 Si in the surface on the side of the piezoelectric layer 2 can be (100), (110), or (111). It is preferred that the Si constituting the supporting member 8 has a high resistance with a resistivity of more than 4 kΩcm. However, the supporting member 8 can also be composed of suitable insulating materials or semiconductor materials.

[0211] 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.

[0212] The plurality of electrodes 3, 4 and the first bus bar 5 and the second bus bar 6 include a suitable metal or alloy such as Al or AlCu alloy. In the elastic wave device 1, the electrodes 3, 4 and the first bus bar 5 and the second bus bar 6 have a structure in which an Al film is stacked on a Ti film. Alternatively, a bonding layer other than a Ti film may be used.

[0213] 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 the resonance characteristics of the bulk wave utilizing the thickness shear mode excited in the piezoelectric layer 2. In addition, in the elastic wave device 1, when the thickness of the piezoelectric layer 2 is set to d and the center-to-center distance between any adjacent electrodes 3 and 4 among the plurality of pairs of electrodes 3 and 4 is set to p, d / p is set to be less than 0.5. Therefore, the bulk wave of the thickness shear mode can be effectively excited, and good resonance characteristics can be obtained. More preferably, d / p is less than 0.24, in which case, even better resonance characteristics can be obtained.

[0214] In the elastic wave device 1, since it has the above-mentioned structure, 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 number of electrode fingers can be reduced because the body wave of the thickness shear mode is utilized. Fig.25 (a) and Fig.25 (b) explains the difference between the Lamb wave used in the elastic wave device and the body wave of the thickness shear mode.

[0215] Fig.25(a) is a schematic front cross-sectional view for explaining Lamb waves propagating in a piezoelectric film of an elastic wave device as described in Japanese Patent Gazette No. 2012-257019. Here, the wave propagates in the piezoelectric film 201 as indicated by the arrow. Here, in the piezoelectric film 201, the first principal surface 201a and the second principal surface 201b are opposed to each other, and the thickness direction connecting the first principal surface 201a and the second principal surface 201b is the Z direction. The X direction is the direction in which the electrode fingers of the IDT electrode are arranged. Fig.25 As shown in (a), for Lamb waves, the waves propagate in the X direction as shown in the figure. Since it is a plate wave, although the piezoelectric film 201 vibrates as a whole, the waves propagate 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.

[0216] In contrast, Fig.25 As shown in (b), in the elastic wave device 1, the vibration displacement is in the thickness shear direction, so the wave generally propagates 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, and resonates. That is, the X-direction component of the wave is significantly smaller than the Z-direction component. Moreover, the resonance characteristics can be obtained by the propagation of the wave in the Z direction, so even if the number of electrode fingers of the reflector is reduced, it is not easy to cause propagation loss. 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 cause a decrease in the Q value.

[0217] In addition, if Fig.26 As shown in FIG. 1 , the amplitude directions of the thickness shear mode body wave 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.26 , a body wave is schematically shown when a voltage is applied between the electrode 3 and the electrode 4 so that the electrode 4 has a higher potential than the electrode 3. The first region 451 is a region between the first principal surface 2a and the imaginary plane VP1 which is orthogonal to the thickness direction of the piezoelectric layer 2 and divides the piezoelectric layer 2 into two parts in the excitation region C. The second region 452 is a region between the imaginary plane VP1 and the second principal surface 2b in the excitation region C.

[0218] As described above, elastic wave device 1 includes at least one pair of electrodes including electrode 3 and electrode 4 , but since waves are not propagated in the X direction, there is no need to have more than one pair of electrodes including electrode 3 and electrode 4 . In other words, at least one pair of electrodes is sufficient.

[0219] 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.

[0220] Fig. 27 It is shown Fig.24 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.

[0221] Piezoelectric layer 2: LiNbO3 with Euler angles (0°, 0°, 90°), thickness = 400nm.

[0222] 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.

[0223] Insulating layer 7: a silicon oxide film having a thickness of 1 μm.

[0224] Supporting member 8: Si.

[0225] 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 .

[0226] In elastic wave device 1 , the inter-electrode distances of the electrode pairs including electrodes 3 and 4 are set equal in a plurality of pairs. In other words, electrodes 3 and electrodes 4 are arranged at equal intervals.

[0227] according to Fig. 27 It is clear that good resonance characteristics with a relative bandwidth of 12.5% ​​are obtained despite the absence of a reflector.

[0228] 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.28 This is explained.

[0229] and got Fig. 27 A plurality of elastic wave devices are obtained by changing d / p in the same manner as the elastic wave devices having the resonance characteristics shown. Fig.28 3 is a diagram showing the relationship between d / p and the relative bandwidth of a resonator as an elastic wave device.

[0230] according to Fig.28It 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 made greater 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.

[0231] Fig.29 1 is a top view of an elastic wave device using a thickness shear mode bulk wave. In the elastic wave device 80, a pair of electrodes including an electrode 3 and an electrode 4 are provided on the first principal surface 2a of the piezoelectric layer 2. Fig.29 K in is the crossing width. As described above, in the elastic wave device of the present invention, the number of pairs of electrodes may be 1 pair. In this case, as long as the above d / p is 0.5 or less, a thickness shear mode body wave can be effectively excited.

[0232] In the elastic wave device 1, it is preferable that the metallization ratio MR of the excitation region C, which is an area where any adjacent electrodes 3 and 4 overlap when viewed in the opposite direction relative to the adjacent electrodes 3 and 4, satisfies MR≤1.75(d / p)+0.075. In this case, the stray can be effectively reduced. Fig.30 as well as Fig.31 Let me explain this. Fig.30 : 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.

[0233] Reference Fig.23 (b) will explain the metallization ratio MR. Fig.23In 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 refers to 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. And, the area of ​​the electrodes 3 and 4 in the excitation region C relative to the area of ​​the excitation region C is the metallization ratio MR. That is, the metallization ratio MR is the ratio of the area of ​​the metallized portion to the area of ​​the excitation region C.

[0234] When a plurality of pairs of electrodes are provided, the ratio of the total area of ​​the metallized portions included in all the excitation regions to the area of ​​the excitation regions may be defined as MR.

[0235] Fig.31 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 configured in the manner 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.31 These are the results obtained when a piezoelectric layer including Z-cut LiNbO 3 is used, but the same tendency is observed when a piezoelectric layer having other cut angles is used.

[0236] exist Fig.31 In the area surrounded by ellipse J in , the spurious signal increases to 1.0. Fig.31 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 spurs with a spurious level of 1 or more will appear in the passband. Fig.30 As shown in the resonance characteristics, large spurious signals indicated by arrow B appear in the frequency band. Therefore, it is preferable that the relative bandwidth is 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.

[0237] Fig.32 : 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 having different d / 2p and MR were constructed, and the relative bandwidth was measured. Fig.32The portion marked with hatching 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 is represented by MR=3.5(d / 2p)+0.075. That is, MR=1.75(d / p)+0.075. Therefore, it is preferred that MR≤1.75(d / p)+0.075. In this case, it is easy to make the relative bandwidth less than 17%. More preferably, Fig.32 The region to the right of MR=3.5(d / 2p)+0.05 is indicated by the dashed line D1 in FIG. That is, as long as MR≤1.75(d / p)+0.05, the relative bandwidth can be reliably made 17% or less.

[0238] Fig.33 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.33 The hatched portion of is a region where a relative bandwidth of at least 5% can be obtained. When the range of this region is approximated, it becomes a range represented by the following equations (1), (2), and (3).

[0239] (0°±10°, 0°~20°, arbitrary ψ) …Formula (1)

[0240] (0°±10°, 20°~80°, 0°~60° (1-(θ-50) 2 / 900) 1 / 2 ) or (0°±10°, 20°~80°, [180°-60°(1-(θ-50) 2 / 900) 1 / 2 ]~180°) …Formula (2)

[0241] (0°±10°, [180°-30° (1-(ψ-90) 2 / 8100) 1 / 2 ]~180°, any ψ) …Formula (3)

[0242] Therefore, in the case of the Euler angle range of the above-mentioned formula (1), formula (2) or formula (3), the relative bandwidth can be sufficiently widened, which is preferable. The same is true when the piezoelectric layer 2 is a lithium tantalate layer.

[0243] Fig.34 It is a front cross-sectional view of an elastic wave device having an acoustic multilayer membrane.

[0244] 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 having relatively low acoustic impedance and high acoustic impedance layers 82b, 82d having 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, by making the above-mentioned d / p less than 0.5, the resonance characteristics of the bulk wave based on the thickness shear mode can be obtained. In addition, in the acoustic multilayer film 82, the number of stacked 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 away from the piezoelectric layer 2 compared with the low acoustic impedance layers 82a, 82c, 82e.

[0245] 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.

[0246] In the elastic wave devices of the first to seventh embodiments and their respective modifications, for example, an acoustic reflection film may be provided between the support member and the piezoelectric layer as the piezoelectric film. Fig.34 The acoustic multilayer film 82 shown. Specifically, the support member and the piezoelectric film may be arranged so that at least a portion of the support member and at least a portion of the piezoelectric film are opposed to each other with the acoustic multilayer film 82 sandwiched therebetween. In this case, in the acoustic multilayer film 82, it is sufficient to alternately stack low acoustic impedance layers and high acoustic impedance layers. The acoustic multilayer film 82 may also be an acoustic reflection portion in an elastic wave device.

[0247] In the elastic wave devices of the first to seventh embodiments and their variants using body waves in a thickness shear mode, as described above, d / p is preferably less than 0.5, and more preferably less than 0.24. This allows for better resonance characteristics. Furthermore, in the excitation region of the elastic wave devices of the first to seventh embodiments and their variants using body waves in a thickness shear mode, as described above, MR ≤ 1.75 (d / p) + 0.075 is preferably satisfied. In this case, spurious emission can be more reliably suppressed.

[0248] The piezoelectric layer in the elastic wave device of the first to seventh embodiments and each modified example using the bulk wave in the thickness shear mode is preferably a lithium niobate layer. Furthermore, the Euler angles (φ, θ, ψ) of the lithium niobate constituting the piezoelectric layer are preferably within the range of the above-mentioned formula (1), formula (2) or formula (3). In this case, the relative bandwidth can be sufficiently expanded.

[0249] Description of Reference Numerals

[0250] 1…Elastic wave device

[0251] 2…Piezoelectric layer

[0252] 2a, 2b…1st and 2nd main surfaces

[0253] 3, 4…Electrode

[0254] 5, 6…1st and 2nd bus bars

[0255] 7…Insulation layer

[0256] 7a…Through hole

[0257] 8…Supporting member

[0258] 8a…Through hole

[0259] 9…Hollow

[0260] 10…Elastic wave device

[0261] 10a…Cavity

[0262] 11…IDT electrode

[0263] 11a, 11b…Page 1 and 2

[0264] 11c…side

[0265] 12…Piezoelectric substrate

[0266] 13…Supporting member

[0267] 14…Piezoelectric layer

[0268] 14a, 14b…1st, 2nd main surface

[0269] 15…Insulation layer

[0270] 16...Support base plate

[0271] 24A, 24B ... 1st and 2nd band-shaped mass-added films

[0272] 25A, 25B ... 1st and 2nd granular mass addition films

[0273] 26, 27…1st and 2nd bus bars

[0274] 28, 29…1st and 2nd electrode fingers

[0275] 28a, 29a ... first edge portion

[0276] 28b, 29b ... second edge portion

[0277] 30…Elastic wave device

[0278] 34A, 34B ... 1st and 2nd band-shaped mass-added films

[0279] 34a, 34b…stepped portion

[0280] 35A, 35B ... 1st and 2nd granular mass addition films

[0281] 45A, 45B ... 1st and 2nd granular mass addition films

[0282] 53…Dielectric film

[0283] 54A, 54B ... 1st and 2nd band-shaped mass-added films

[0284] 55A, 55B ... 1st and 2nd granular mass addition films

[0285] 60…Filter device

[0286] 62, 63…1st and 2nd signal terminals

[0287] 71B to 71E…2nd to 5th elastic wave resonators

[0288] 74A, 74B ... 1st and 2nd band-shaped mass-added films

[0289] 80, 81…Elastic wave device

[0290] 82…Acoustic multilayer film

[0291] 82a, 82c, 82e…low acoustic impedance layer

[0292] 82b, 82d…high acoustic impedance layer

[0293] 201…Piezoelectric film

[0294] 201a, 201b ... first and second main surfaces

[0295] 451, 452…1st and 2nd areas

[0296] C…Incentive Area

[0297] E1, E2…1st and 2nd edge areas

[0298] F…Intersection area

[0299] G1, G2…1st and 2nd gap areas

[0300] H…Central area

[0301] N…Electrode finger pair area

[0302] P1~P3…Parallel arm resonator

[0303] S1~S4…Series arm resonator

[0304] VP1…imaginary plane.

Claims

1. An elastic wave device comprising: A piezoelectric substrate having a support member including a support substrate, and a piezoelectric film provided on the support member and including a piezoelectric layer, the piezoelectric layer including lithium niobate; and An IDT electrode is disposed on the piezoelectric layer and has a pair of bus bars and a plurality of electrode fingers. 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 IDT electrode. When the thickness of the piezoelectric film is d and the center-to-center distance between adjacent electrode fingers is p, d / p is equal to or less than 0.

5. A portion of the electrode fingers among the plurality of electrode fingers are connected to one of the bus bars of the IDT electrode, and the remaining electrode fingers among the plurality of electrode fingers are connected to the other bus bar, and the plurality of electrode fingers connected to the one bus bar and the plurality of electrode fingers connected to the other bus bar are interlaced with each other. The direction in which the plurality of electrode fingers extend is set as the electrode finger extension direction, and the direction orthogonal to the electrode finger extension direction is set as the electrode finger orthogonal direction. When observed from the electrode finger orthogonal direction, the region where adjacent electrode fingers overlap each other is a cross region, and the region between the cross region and the pair of bus bars is a pair of gap regions. The cross region has a central region and a pair of edge regions arranged to sandwich the central region in the electrode finger extension direction. The elastic wave device further comprises: a band-shaped mass addition film provided in at least one of the pair of gap regions and provided continuously so as to overlap with the plurality of electrode fingers and the region between the electrode fingers in a plan view; and A plurality of granular mass adding films are provided over the gap region where the strip-shaped mass adding films are provided and the edge region adjacent to the gap region, and are provided so as not to overlap at least a portion of a region between at least one adjacent electrode fingers in a plan view.

2. The elastic wave device according to claim 1, wherein: Each of the granular mass adding films overlaps with one or less of the electrode fingers in a plan view.

3. The elastic wave device according to claim 1 or 2, wherein: The strip-shaped mass adding film includes a first strip-shaped mass adding film provided in one of the gap regions and a second strip-shaped mass adding film provided in the other of the gap regions. The plurality of granular mass adding films include a plurality of first granular mass adding films arranged throughout the gap region where the first strip-shaped mass adding film is arranged and the edge region adjacent to the gap region, and a plurality of second granular mass adding films arranged throughout the gap region where the second strip-shaped mass adding film is arranged and the edge region adjacent to the gap region.

4. The elastic wave device according to any one of claims 1 to 3, wherein: The plurality of granular mass adding films include the granular mass adding film having a portion stacked with the electrode finger, In a portion where the granular mass addition film and the electrode fingers are stacked, the piezoelectric layer, the electrode fingers, and the granular mass addition film are stacked in this order.

5. The elastic wave device according to any one of claims 1 to 3, wherein: The plurality of granular mass adding films include the granular mass adding film having a portion stacked with the electrode finger, In a portion where the granular mass addition film and the electrode fingers are stacked, the piezoelectric layer, the granular mass addition film, and the electrode fingers are stacked in this order.

6. The elastic wave device according to claim 4 or 5, wherein: The granular mass addition film having a portion overlapping the electrode fingers has a portion overlapping the front end portions of the electrode fingers.

7. The elastic wave device according to any one of claims 1 to 3, wherein: The plurality of granular mass adding films include the granular mass adding film surrounding the tip portions of the electrode fingers in three directions in a plan view.

8. The elastic wave device according to any one of claims 1 to 7, wherein: The strip-shaped mass adding film includes a first strip-shaped mass adding film provided in one of the gap regions. The plurality of granular mass adding films include a plurality of first granular mass adding films provided over the gap region where the first band-shaped mass adding film is provided and the edge region adjacent to the gap region. When a region including only one pair of the electrode fingers connected to the mutually different bus bars among the plurality of electrode fingers is defined as an electrode finger pair region, a plurality of the electrode finger pair regions are configured. The plurality of electrode finger pair regions include at least one electrode finger pair region in which the total area of ​​the first band-shaped mass adding film and the first granular mass adding film is different from that of the other electrode finger pair regions.

9. The elastic wave device according to any one of claims 1 to 8, wherein: The strip-shaped mass-adding film provided in at least one of the pair of gap regions extends from the gap region to a portion overlapping with the bus bar adjacent to the gap region in a plan view.

10. The elastic wave device according to any one of claims 1 to 9, wherein: The strip-shaped mass adding film and the plurality of granular mass adding films provided in the same gap region are integrally formed of the same material.

11. The elastic wave device according to any one of claims 1 to 9, wherein: The strip-shaped mass adding film and the plurality of granular mass adding films located in the same gap region are provided independently of each other, and the strip-shaped mass adding film and the plurality of granular mass adding films are not in contact with each other.

12. The elastic wave device according to any one of claims 1 to 11, wherein: A dielectric film is provided on the piezoelectric layer so as to cover the IDT electrode.

13. The elastic wave device according to claim 12, wherein: The dielectric film includes silicon oxide.

14. The elastic wave device according to any one of claims 1 to 13, wherein: The strip-shaped mass adding film and the plurality of granular mass adding films include at least one material selected from the group consisting of silicon oxide, tantalum oxide, niobium oxide, tungsten oxide, and hafnium oxide.

15. The elastic wave device according to any one of claims 1 to 14, wherein: d / p is less than 0.

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16. The elastic wave device according to any one of claims 1 to 15, wherein: The region where the adjacent electrode fingers overlap each other when viewed from the orthogonal direction of the electrode fingers and the region between the centers of the adjacent electrode fingers in the orthogonal direction are the excitation regions. When the metallization ratio of the plurality of electrode fingers to the excitation region is MR, MR≦1.75(d / p)+0.075 is satisfied.

17. The elastic wave device according to any one of claims 1 to 16, 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), (0°±10°, 0°~20°, arbitrary ψ) …Formula (1) (0°±10°, 20°~80°, 0°~60° (1-(θ-50) 2 / 900) 1 / 2 ) or (0°±10°, 20°~80°, [180°-60°(1-(θ-50) 2 / 900) 1 / 2 ]~180°) …Formula (2) (0°±10°, [180°-30° (1-(ψ-90) 2 / 8100) 1 / 2 ]~180°, arbitrary ψ) …Formula (3).

18. The elastic wave device according to any one of claims 1 to 17, wherein: The sound reflecting portion is a cavity portion, and the support member and the piezoelectric film are arranged so that a portion of the support member and a portion of the piezoelectric film face each other with the cavity portion interposed therebetween.

19. The elastic wave device according to any one of claims 1 to 17, wherein: The acoustic reflection portion is an acoustic reflection membrane including a high acoustic impedance layer having relatively high acoustic impedance and a low acoustic impedance layer having relatively low acoustic impedance, and the supporting member and the piezoelectric membrane are configured so that at least a portion of the supporting member and at least a portion of the piezoelectric membrane are opposite to each other with the acoustic reflection membrane sandwiched therebetween.

20. A filter device comprising a plurality of elastic wave resonators including at least one series arm resonator and at least one parallel arm resonator, wherein: At least one of the series arm resonator and the parallel arm resonator is the elastic wave device according to any one of claims 1 to 19.

21. The filter device according to claim 20, wherein The series arm resonator and the parallel arm resonator include at least one first elastic wave resonator and at least one second elastic wave resonator. The first elastic wave resonator is the elastic wave device. The second elastic wave resonator includes a piezoelectric substrate and an IDT electrode provided on the piezoelectric substrate and including a pair of bus bars and a plurality of electrode fingers, and does not include a mass addition film corresponding to the strip-shaped mass addition film and the granular mass addition film of the first elastic wave resonator.

22. The filter device according to claim 20 or 21, wherein: The series arm resonator and the parallel arm resonator include at least one first elastic wave resonator and at least one third elastic wave resonator. The first elastic wave resonator is the elastic wave device. The third elastic wave resonator includes a piezoelectric substrate and an IDT electrode provided on the piezoelectric substrate and including a pair of bus bars and a plurality of electrode fingers, and does not include a mass addition film corresponding to the granular mass addition film of the first elastic wave resonator. In the third elastic wave resonator, when the IDT electrode is viewed from a direction orthogonal to the direction in which the plurality of electrode fingers extend, a region where adjacent electrode fingers overlap each other is a crossing region, and a region between the crossing region and the pair of bus bars of the IDT electrode is a pair of gap regions. The third elastic wave resonator and the first elastic wave resonator independently have a strip-shaped mass-addition film. In the third elastic wave resonator, the strip-shaped mass-addition film is provided in at least one of the pair of gap regions and is not provided in the intersection region. The strip-shaped mass-addition film is provided continuously so as to overlap with the plurality of electrode fingers and regions between the electrode fingers in a plan view.

23. The filter device according to any one of claims 20 to 22, wherein: The series arm resonator and the parallel arm resonator include at least one first elastic wave resonator and at least one fourth elastic wave resonator. The first elastic wave resonator is the elastic wave device. The fourth elastic wave resonator includes a piezoelectric substrate and an IDT electrode provided on the piezoelectric substrate and including a pair of bus bars and a plurality of electrode fingers, and does not include a mass addition film corresponding to the strip-shaped mass addition film of the first elastic wave resonator. In the fourth elastic wave resonator, when the IDT electrode is viewed from a direction orthogonal to the direction in which the plurality of electrode fingers extend, a region where adjacent electrode fingers overlap each other is a cross region, a region between the cross region and the pair of bus bars of the IDT electrode is a pair of gap regions, and the cross region includes a central region and a pair of edge regions arranged to sandwich the central region in the direction in which the electrode fingers extend. The fourth elastic wave resonator and the first elastic wave resonator independently have a plurality of granular mass addition films. In the fourth elastic wave resonator, the plurality of granular mass addition films are arranged over at least one gap region among the pair of gap regions and the edge region adjacent to the gap region, and are arranged to overlap with one or less of the electrode fingers in a plan view.

24. The filter device according to any one of claims 20 to 23, wherein: The series arm resonator and the parallel arm resonator include at least one first elastic wave resonator and at least one fifth elastic wave resonator. The first elastic wave resonator is the elastic wave device. The fifth elastic wave resonator includes a piezoelectric substrate and an IDT electrode provided on the piezoelectric substrate and including a pair of bus bars and a plurality of electrode fingers, and does not include a mass addition film equivalent to the granular mass addition film of the first elastic wave resonator. In the fifth elastic wave resonator, when the IDT electrode is viewed from a direction orthogonal to the direction in which the plurality of electrode fingers extend, a region where adjacent electrode fingers overlap each other is a cross region, a region between the cross region and the pair of bus bars of the IDT electrode is a pair of gap regions, and the cross region includes a central region and a pair of edge regions arranged to sandwich the central region in the direction in which the plurality of electrode fingers extend. The fifth elastic wave resonator and the first elastic wave resonator independently have a strip-shaped mass-addition film. In the fifth elastic wave resonator, the strip-shaped mass-addition film is provided over at least one gap region among the pair of gap regions and the edge region adjacent to the gap region, and is provided continuously so as to overlap with the plurality of electrode fingers and the region between the electrode fingers in a plan view.

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