Elastic wave device

Abstract

Provided is an elastic wave device with which it is possible to promote miniaturization of a filter device and to suppress deterioration of filter characteristics. An elastic wave device (10) according to the present invention is provided with: a first elastic wave resonator (10A) having a first piezoelectric film including a first piezoelectric layer (piezoelectric layer (14)) including a piezoelectric body; and at least one second elastic wave resonator (10B) electrically connected to the first elastic wave resonator (10A) and having a second piezoelectric film including a second piezoelectric layer (piezoelectric layer (14)) including a piezoelectric body, and an IDT electrode (31) provided on the second piezoelectric layer. A first elastic wave resonator (10A) is provided with: a first comb electrode that is provided on a first piezoelectric layer, has first bus bars, and a plurality of first electrode fingers (25) each of which has one end connected to the first bus bars, and is connected to an input potential; a second comb-shaped electrode provided on the first piezoelectric layer, having a second bus bar and a plurality of second electrode fingers (26), one end of which is connected to each of the second bus bars, the plurality of second electrode fingers (26) being interleaved and inserted with the plurality of first electrode fingers (25), the second comb-shaped electrode being connected to the output potential; and a third electrode having a plurality of third electrode fingers (27) provided on the first piezoelectric layer so as to be aligned with the first electrode fingers (25) and the second electrode fingers (26) in a direction in which the first electrode fingers (25) and the second electrode fingers (26) are aligned in plan view, and a connection electrode (third bus bar (24)) that connects adjacent third electrode fingers (27) to each other, the third electrode fingers (27) being provided on the first piezoelectric layer so as to be aligned with the first electrode fingers (25) and the second electrode fingers (26) in a direction in which the first electrode fingers (25) and the second electrode fingers (26) are aligned in plan view. The third electrode is connected to a potential different from that of the first comb electrode and that of the second comb electrode. The order in which the first electrode fingers (25), the second electrode fingers (26), and the third electrode fingers (27) are arranged is an order in which the first electrode fingers (25), the third electrode fingers (27), the second electrode fingers (26), and the third electrode fingers (27) are arranged as one cycle from the first electrode fingers (25). An IDT electrode (31) of the second elastic wave resonator (10B) has a plurality of fourth electrode fingers (35) and a plurality of fifth electrode fingers (36) that are interleaved with each other. The second elastic wave resonator (10B) is a series arm resonator or a parallel arm resonator.

Description

Technical Field

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

[0002] In the past, elastic wave devices were widely used in filters of portable phones, etc. In recent years, an elastic wave device using a thickness shear mode body 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, the thickness shear mode body wave is excited.

[0003] Prior Art Literature

[0004] Patent Literature

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

[0006] Problem that the invention aims to solve

[0007] The elastic wave device is, for example, an elastic wave resonator, which is used in, for example, a ladder filter. In order to obtain good characteristics in the ladder filter, it is necessary to increase the electrostatic capacitance ratio between the plurality of elastic wave resonators. In this case, it is necessary to increase the electrostatic capacitance of some elastic wave resonators in the ladder filter.

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

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

[0010] Furthermore, the present inventors have found that even if only the above-mentioned structure is adopted, the filter characteristics may be degraded.

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

[0012] Technical solutions to solve problems

[0013] The elastic wave device involved in the present invention comprises: a first elastic wave resonator, which has a first piezoelectric film including a first piezoelectric layer, the first piezoelectric layer including a piezoelectric body; and at least one second elastic wave resonator, which is electrically connected to the first elastic wave resonator, and has a second piezoelectric film including a second piezoelectric layer and an IDT electrode arranged on the second piezoelectric layer, the second piezoelectric layer including a piezoelectric body, the first elastic wave resonator comprising: a first comb-shaped electrode, which is arranged on the first piezoelectric layer, and has a first bus bar and a plurality of first electrode fingers, one end of which is respectively connected to the first bus bar, the first comb-shaped electrode is connected to an input potential; a second comb-shaped electrode, which is arranged on the first piezoelectric layer, and has a second bus bar and a plurality of second electrode fingers, one end of which is respectively connected to the second bus bar and is interlaced with the plurality of first electrode fingers, the second comb-shaped electrode is connected to an output potential; and a third electrode, which has a plurality of third electrode fingers and connecting electrodes connecting adjacent third electrode fingers to each other, the plurality of third electrode fingers are respectively arranged on the first piezoelectric layer so that, in a plan view, they are arranged with the first electrode fingers and the second electrode fingers in the direction in which the first electrode fingers and the second electrode fingers are arranged, the third electrode is connected to a potential different from that of the first comb-shaped electrode and the second comb-shaped electrode, the first electrode fingers, the second electrode fingers and the third electrode fingers are arranged in an order that takes the first electrode fingers, the third electrode fingers, the second electrode fingers and the third electrode fingers as a period when starting from the first electrode finger, the IDT electrode of the second elastic wave resonator has a plurality of fourth electrode fingers and a plurality of fifth electrode fingers that are interlaced with each other, and the second elastic wave resonator is a series arm resonator or a parallel arm resonator.

[0014] Effects of the Invention

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

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

[0017] Figure 2 4 is a schematic front cross-sectional view of the first elastic wave resonator in the first embodiment of the present invention.

[0018] Figure 3 FIG. 1 is a schematic plan view of the first elastic wave resonator according to the first embodiment of the present invention.

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

[0020] Figure 5 FIG. 1 is a schematic plan view of the second elastic wave resonator according to the first embodiment of the present invention.

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

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

[0023] Figure 8 FIG. 1 is a schematic plan view of a first elastic wave resonator in a first modification of the first embodiment of the present invention.

[0024] Fig. 9 4 is a schematic front cross-sectional view of a second elastic wave resonator in a second modified example of the first embodiment of the present invention.

[0025] Fig.10 FIG. 1 is a schematic plan view of a first elastic wave resonator according to a second embodiment of the present invention.

[0026] Fig.11 1 is a schematic front cross-sectional view showing the vicinity of first to third electrode fingers in the second embodiment of the present invention.

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

[0028] Fig.13 It is a diagram showing the passage characteristics of the third embodiment of the present invention and the second comparative example.

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

[0030] Fig.15 (a) is a perspective view showing a schematic diagram of the appearance of an elastic wave device using a thickness shear mode bulk wave, Fig.15 (b) is a top view showing the electrode structure on the piezoelectric layer.

[0031] Fig.16 It is along Fig.15 (a) A partial cross-sectional view along line AA.

[0032] Fig.17(a) is a schematic front cross-sectional view for explaining Lamb waves propagating through a piezoelectric film of an elastic wave device. Fig.17 (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.

[0033] Fig.18 It is a diagram showing the amplitude direction of the body wave in the thickness shear mode.

[0034] Fig.19 FIG. 1 is a diagram showing the resonance characteristics of an elastic wave device using bulk waves in a thickness shear mode.

[0035] Fig. 20 : This is a diagram showing the relationship between d / p and the fractional 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.

[0036] Fig.21 This is a top view of an elastic wave device using bulk waves in a thickness shear mode.

[0037] Fig. 22 FIG. 4 is a diagram showing the resonance characteristics of an elastic wave device according to a reference example in which spurious emission occurs.

[0038] Fig.23 This is a diagram showing the relationship between the fractional 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.

[0039] Fig.24 It is a graph showing the relationship between d / 2p and the metallization ratio MR.

[0040] Fig.25 This is a diagram showing a mapping of the fractional bandwidth with respect to the Euler angle (0°, θ, ψ) of LiNbO 3 when d / p is made as close to 0 as possible.

[0041] Fig.26 It is a front cross-sectional view of an elastic wave device having an acoustic multilayer membrane.

[0042] Fig. 27 This is a partially cutaway perspective view for explaining an elastic wave device using Lamb waves. DETAILED DESCRIPTION

[0043] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings, thereby making the present invention clear.

[0044] It should be noted that each embodiment described in this specification is illustrative and that some structures may be replaced or combined between different embodiments.

[0045] Figure 1It is a schematic plan view of the elastic wave device according to the first embodiment of the present invention.

[0046] The elastic wave device 10 is used as a part of a filter device. The elastic wave device 10 includes a plurality of elastic wave resonators. However, the elastic wave device according to the present invention may also be a filter device. The structure of the elastic wave device 10 will be described below.

[0047] The elastic wave device 10 has a first elastic wave resonator 10A and a second elastic wave resonator 10B. The first elastic wave resonator 10A is an acoustic coupling filter. The second elastic wave resonator 10B is an elastic wave resonator having an IDT (Interdigital Transducer) electrode 31. It should be noted that the number of the first elastic wave resonator 10A and the second elastic wave resonator 10B in the elastic wave device 10 is not limited to the above. The elastic wave device of the present invention only needs to have at least one first elastic wave resonator and at least one second elastic wave resonator.

[0048] In elastic wave device 10, first elastic wave resonator 10A and second elastic wave resonator 10B are connected in series. Second elastic wave resonator 10B is a series arm resonator. In the present embodiment, second elastic wave resonator 10B is used as a trap element. It should be noted that second elastic wave resonator 10B may also be a parallel arm resonator.

[0049] The elastic wave device of the present invention may have at least one of the following structures: one structure is a structure in which the second elastic wave resonator as at least one series arm resonator is electrically connected to at least one first elastic wave resonator; and the other structure is a structure in which the second elastic wave resonator as at least one parallel arm resonator is electrically connected to at least one first elastic wave resonator.

[0050] like Figure 1 As shown, the elastic wave device 10 has a piezoelectric substrate 12. The piezoelectric substrate 12 is a substrate having piezoelectricity. The piezoelectric substrate 12 has a piezoelectric layer 14 as a piezoelectric film. The first elastic wave resonator 10A and the second elastic wave resonator 10B share the piezoelectric substrate 12. Therefore, when the piezoelectric substrate of the first elastic wave resonator 10A is set as the first piezoelectric substrate and the piezoelectric substrate of the second elastic wave resonator 10B is set as the second piezoelectric substrate, in the present embodiment, the first piezoelectric substrate and the second piezoelectric substrate are the same piezoelectric substrate 12. Here, the piezoelectric layer is a layer including a piezoelectric body. On the other hand, in this specification, a piezoelectric film is a film having piezoelectricity, and does not necessarily refer to a film including a piezoelectric body. However, in the present embodiment, the piezoelectric film is a single-layer piezoelectric layer 14, which is a film including a piezoelectric body. It should be noted that in the present invention, the piezoelectric film may also be a stacked film including the piezoelectric layer 14.

[0051] First elastic wave resonator 10A includes a first piezoelectric layer as a first piezoelectric film. Second elastic wave resonator 10B includes a second piezoelectric layer as a second piezoelectric film. However, in the present embodiment, first elastic wave resonator 10A and second elastic wave resonator 10B share piezoelectric layer 14 as a piezoelectric film. Therefore, the first piezoelectric layer and the second piezoelectric layer are the same piezoelectric layer 14. It should be noted that, for example, first elastic wave resonator 10A and second elastic wave resonator 10B may also include a piezoelectric film separately. First elastic wave resonator 10A and second elastic wave resonator 10B may also include a piezoelectric substrate separately.

[0052] Hereinafter, the structure of the first elastic wave resonator 10A as an acoustic coupling filter will be described in detail.

[0053] Figure 2 4 is a schematic front cross-sectional view of the first elastic wave resonator in the first embodiment. Figure 3 is a schematic top view of the first elastic wave resonator in the first embodiment. It should be noted that Figure 2 It is along Figure 3 Schematic cross-sectional view of line II in FIG. Figure 2 In the diagram, each electrode is indicated by a hatched line. Figure 2 In other schematic top views, electrodes may also be shaded similarly. Figure 3 In the figure, wiring connected to the first elastic wave resonator and the like are omitted.

[0054] Figure 2 The first elastic wave resonator 10A shown has a piezoelectric substrate 12 as a first piezoelectric substrate and a functional electrode 11. The piezoelectric substrate 12 has a supporting member 13 and a piezoelectric layer 14 as a first piezoelectric layer. In this embodiment, the supporting member 13 includes a supporting substrate 16 and an insulating layer 15. The insulating layer 15 is provided on the supporting substrate 16. The piezoelectric layer 14 is provided on the insulating layer 15. However, the supporting member 13 may also be composed of only the supporting substrate 16. It should be noted that the supporting member 13 may not necessarily be provided.

[0055] The piezoelectric layer 14 has a first principal surface 14a and a second principal surface 14b. The first principal surface 14a and the second principal surface 14b are opposite to each other. Of the first principal surface 14a and the second principal surface 14b, the second principal surface 14b is located on the side of the supporting member 13. In the present embodiment, the piezoelectric layer 14 includes lithium niobate. Specifically, the piezoelectric layer 14 includes Z-cut LiNbO3. However, the piezoelectric layer 14 may also include rotated Y-cut lithium niobate. Alternatively, the piezoelectric layer 14 may also include lithium tantalate such as LiTaO3. In the present specification, a certain component includes a certain material, including trace impurities to the extent that the electrical characteristics of the elastic wave device are not significantly deteriorated.

[0056] The functional electrode 11 is provided on the first main surface 14a of the piezoelectric layer 14. Figure 3 As shown, the functional electrode 11 has a pair of comb-shaped electrodes and a third electrode 19. Specifically, the pair of comb-shaped electrodes is a first comb-shaped electrode 17 and a second comb-shaped electrode 18. The first comb-shaped electrode 17 is connected to an input potential. The second comb-shaped electrode 18 is connected to an output potential. In the present embodiment, the third electrode 19 is connected to a reference potential. It should be noted that the third electrode 19 may not necessarily be connected to a reference potential. The third electrode 19 may be connected to a potential different from that of the first comb-shaped electrode 17 and the second comb-shaped electrode 18. However, the third electrode 19 is preferably connected to a reference potential.

[0057] The first comb-shaped electrode 17 and the second comb-shaped electrode 18 are provided on the first main surface 14a of the piezoelectric layer 14. The first comb-shaped electrode 17 has a first bus bar 22 and a plurality of first electrode fingers 25. One ends of the plurality of first electrode fingers 25 are respectively connected to the first bus bar 22. The second comb-shaped electrode 18 has a second bus bar 23 and a plurality of second electrode fingers 26. One ends of the plurality of second electrode fingers 26 are respectively connected to the second bus bar 23.

[0058] The first bus bar 22 and the second bus bar 23 are opposite to each other. The plurality of first electrode fingers 25 and the plurality of second electrode fingers 26 are interlaced with each other. The first electrode fingers 25 and the second electrode fingers 26 are alternately arranged in a direction orthogonal to the direction in which the first electrode fingers 25 and the second electrode fingers 26 extend.

[0059] The third electrode 19 includes a third bus bar 24 as a connection electrode and a plurality of third electrode fingers 27. The plurality of third electrode fingers 27 are provided on the first principal surface 14a of the piezoelectric layer 14. The plurality of third electrode fingers 27 are electrically connected to each other by the third bus bar 24.

[0060] The plurality of third electrode fingers 27 are respectively arranged so as to be arranged with the first electrode fingers 25 and the second electrode fingers 26 in the direction in which the first electrode fingers 25 and the second electrode fingers 26 are arranged. Therefore, the first electrode fingers 25, the second electrode fingers 26, and the third electrode fingers 27 are arranged in one direction. The plurality of third electrode fingers 27 extend in parallel with the plurality of first electrode fingers 25 and the plurality of second electrode fingers.

[0061] Hereinafter, the direction in which the first electrode finger 25, the second electrode finger 26, and the third electrode finger 27 extend is referred to as the electrode finger extending direction, and the direction orthogonal to the electrode finger extending direction is referred to as the electrode finger orthogonal direction. When the direction in which the first electrode finger 25, the second electrode finger 26, and the third electrode finger 27 are arranged is referred to as the electrode finger arrangement direction, the electrode finger arrangement direction is parallel to the electrode finger orthogonal direction. In this specification, the first electrode finger 25, the second electrode finger 26, and the third electrode finger 27 are sometimes collectively referred to as simply electrode fingers. The first bus bar 22 and the second bus bar 23 are sometimes collectively referred to as simply bus bars.

[0062] Figure 4 This is a schematic front cross-sectional view showing the vicinity of first to third electrode fingers in the first embodiment.

[0063] The order in which the plurality of electrode fingers are arranged is the order in which the first electrode finger 25, the third electrode finger 27, the second electrode finger 26, and the third electrode finger 27 are one cycle when starting from the first electrode finger 25. Therefore, the order in which the plurality of electrode fingers are arranged is the first electrode finger 25, the third electrode finger 27, the second electrode finger 26, the third electrode finger 27, the first electrode finger 25, the third electrode finger 27, the second electrode finger 26, ..., and so on. When the input potential is represented by IN, the output potential is represented by OUT, and the reference potential is represented by GND, and the order of the plurality of electrode fingers is represented as the order of the potentials to be connected, it is represented by IN, GND, OUT, GND, IN, GND, OUT, ..., and so on.

[0064] In the present embodiment, in a region where a plurality of electrode fingers are provided, the electrode fingers located at both ends in the orthogonal direction of the electrode fingers are the third electrode fingers 27. It should be noted that in this region, the electrode fingers located at the ends in the orthogonal direction of the electrode fingers may also be any type of electrode fingers among the first electrode fingers 25, the second electrode fingers 26 and the third electrode fingers 27.

[0065] like Figure 3 As shown, the third bus bar 24 as the connection electrode of the third electrode 19 electrically connects the plurality of third electrode fingers 27 to each other. Specifically, the third bus bar 24 is located in the region between the first bus bar 22 and the front ends of the plurality of second electrode fingers 26. The plurality of first electrode fingers 25 are also located in this region. However, the third bus bar 24 and the plurality of first electrode fingers 25 are electrically insulated from each other by the insulating film 29.

[0066] More specifically, the third bus bar 24 includes a plurality of first connection electrodes 24A and a second connection electrode 24B. Each first connection electrode 24A connects the front ends of two adjacent third electrode fingers 27 to each other. A U-shaped electrode is formed by the first connection electrode 24A and the two third electrode fingers 27. The second connection electrode 24B connects the plurality of first connection electrodes 24A to each other. An insulating film 29 is provided between the second connection electrode 24B and the plurality of first electrode fingers 25.

[0067] More specifically, the insulating film 29 is provided on the first main surface 14a of the piezoelectric layer 14 so as to cover a part of the plurality of first electrode fingers 25. The insulating film 29 is provided in a region between the first bus bar 22 and the tips of the plurality of second electrode fingers 26. The insulating film 29 has a strip shape.

[0068] The insulating film 29 does not reach the first connection electrode 24A of the third electrode 19. Moreover, the second connection electrode 24B is provided over the insulating film 29 and the plurality of first connection electrodes 24A. Specifically, the second connection electrode 24B has a stripe 24a and a plurality of protrusions 24b. Each protrusion 24b extends from the stripe 24a toward each first connection electrode 24A. Each protrusion 24b is connected to each first connection electrode 24A. Thus, the plurality of third electrode fingers 27 are electrically connected to each other through the first connection electrode 24A and the second connection electrode 24B.

[0069] In the present embodiment, the third bus bar 24 is located in a region between the first bus bar 22 and the front ends of the plurality of second electrode fingers 26. Therefore, the front ends of the plurality of second electrode fingers 26 are opposed to the third bus bar 24 with gaps in the electrode finger extending direction. On the other hand, the front ends of the plurality of first electrode fingers 25 are opposed to the second bus bar 23 with gaps in the electrode finger extending direction.

[0070] It should be noted that the third bus bar 24 may also be located in the region between the second bus bar 23 and the front ends of the plurality of first electrode fingers 25. In this case, the front ends of the plurality of first electrode fingers 25 are spaced apart from each other and face the third bus bar 24. On the other hand, the front ends of the plurality of second electrode fingers 26 are spaced apart from each other and face the first bus bar 22.

[0071] The first elastic wave resonator 10A is an elastic wave resonator configured to utilize a thickness shear mode bulk wave. Figure 3 As shown, the first elastic wave resonator 10A has a plurality of excitation regions C. In the plurality of excitation regions C, body waves in the thickness shear mode and elastic waves in other modes are excited. Figure 3 In the figure, only two excitation areas C among the multiple excitation areas C are shown.

[0072] When viewed from the direction orthogonal to the electrode fingers, a portion of the plurality of excitation regions C among all the excitation regions C are regions where adjacent first electrode fingers 25 and third electrode fingers 27 overlap, and are regions between the centers of adjacent first electrode fingers 25 and third electrode fingers 27. When viewed from the direction orthogonal to the electrode fingers, the remaining plurality of excitation regions C are regions where adjacent second electrode fingers 26 and third electrode fingers 27 overlap, and are regions between the centers of adjacent second electrode fingers 26 and third electrode fingers 27. These excitation regions C are arranged in the direction orthogonal to the electrode fingers.

[0073] In the functional electrode 11, the structure other than the third electrode 19 is the same as that of the IDT electrode. When viewed from the orthogonal direction of the electrode fingers, the area where the adjacent first electrode fingers 25 and second electrode fingers 26 overlap is the intersection area E. However, when viewed from the orthogonal direction of the electrode fingers, the intersection area E can also be said to be the area where the adjacent first electrode fingers 25 and third electrode fingers 27 or the adjacent second electrode fingers 26 and third electrode fingers 27 overlap. The intersection area E includes a plurality of excitation areas C. It should be noted that the intersection area E and the excitation area C are areas of the piezoelectric layer 14 defined based on the structure of the functional electrode 11.

[0074] Figure 5 is a schematic top view of the second elastic wave resonator in the first embodiment. Figure 5 In the figure, wiring connected to the second elastic wave resonator and the like are omitted.

[0075] The second elastic wave resonator 10B is configured to utilize a thickness shear mode bulk wave. The second elastic wave resonator 10B includes a piezoelectric substrate 12 as a second piezoelectric substrate and an IDT electrode 31. The piezoelectric substrate 12 includes Figure 2 Shown are a support member 13 and a piezoelectric layer 14 as a second piezoelectric layer.

[0076] like Figure 5 As shown, the IDT electrode 31 has a pair of bus bars and a plurality of electrode fingers. Specifically, the pair of bus bars is a fourth bus bar 32 and a fifth bus bar 33. The fourth bus bar 32 and the fifth bus bar 33 are opposite to each other. Specifically, the plurality of electrode fingers are a plurality of fourth electrode fingers 35 and a plurality of fifth electrode fingers 36. One end of the plurality of fourth electrode fingers 35 is connected to the fourth bus bar 32. One end of the plurality of fifth electrode fingers 36 is connected to the fifth bus bar 33. The plurality of fourth electrode fingers 35 and the plurality of fifth electrode fingers 36 are interlaced with each other.

[0077] Hereinafter, fourth electrode fingers 35 and fifth electrode fingers 36 may be collectively referred to as simply electrode fingers. Fourth bus bar 32 and fifth bus bar 33 may be collectively referred to as simply bus bars. In second elastic wave resonator 10B, the direction in which fourth electrode fingers 35 and fifth electrode fingers 36 extend is the electrode finger extending direction, and the direction orthogonal to the electrode finger extending direction is the electrode finger orthogonal direction.

[0078] Second elastic wave resonator 10B also has an excitation region and an intersection region similar to first elastic wave resonator 10A. In second elastic wave resonator 10B, when viewed from the electrode finger orthogonal direction, the excitation region is a region where adjacent fourth electrode fingers 35 and fifth electrode fingers 36 overlap, and is a region between the centers of adjacent fourth electrode fingers 35 and fifth electrode fingers 36. In second elastic wave resonator 10B, when viewed from the electrode finger orthogonal direction, the intersection region is a region where adjacent fourth electrode fingers 35 and fifth electrode fingers 36 overlap. In second elastic wave resonator 10B, the intersection region also includes a plurality of excitation regions.

[0079] Return to Figure 3 In first elastic wave resonator 10A, the center-to-center distance between adjacent first electrode fingers 25 and third electrode fingers 27 and the center-to-center distance between adjacent second electrode fingers 26 and third electrode fingers 27 is set to p1. The center-to-center distances p1 between adjacent pairs of first electrode fingers 25 and third electrode fingers 27 and the center-to-center distances p1 between adjacent pairs of second electrode fingers 26 and third electrode fingers 27 are the same. However, the center-to-center distances p1 may not be constant.

[0080] exist Figure 5 In second elastic wave resonator 10B shown, the center-to-center distance between adjacent fourth electrode fingers 35 and fifth electrode fingers 36 is defined as p2. The center-to-center distance p2 is the same for a plurality of adjacent pairs of fourth electrode fingers 35 and fifth electrode fingers 36. However, the center-to-center distance p2 may not be constant.

[0081] The relationship between the center distance p1 of the first elastic wave resonator 10A and the center distance p2 of the second elastic wave resonator 10B as a series arm resonator is p2≠p1. Specifically, p2<p1. The relationship between the center distance p1 and the center distance p2 is not limited to the above.

[0082] In the present embodiment, Al is used as the material of first electrode fingers 25, second electrode fingers 26, and third electrode fingers 27 in first elastic wave resonator 10A, and fourth electrode fingers 35 and fifth electrode fingers 36 in second elastic wave resonator 10B. However, the material of each electrode finger of first elastic wave resonator 10A and each electrode finger of second elastic wave resonator 10B is not limited to the above. Alternatively, the material of each electrode finger of first elastic wave resonator 10A and each electrode finger of second elastic wave resonator 10B may include a laminated metal film.

[0083] The width of each electrode finger of first elastic wave resonator 10A and the width of each electrode finger of second elastic wave resonator 10B are the same. However, the width of each electrode finger of first elastic wave resonator 10A and the width of each electrode finger of second elastic wave resonator 10B may be different from each other. The width of an electrode finger is the dimension of the electrode finger along the direction orthogonal to the electrode finger.

[0084] The thickness of each electrode finger of first elastic wave resonator 10A and the thickness of each electrode finger of second elastic wave resonator 10B are the same. However, the thickness of each electrode finger of first elastic wave resonator 10A and the thickness of each electrode finger of second elastic wave resonator 10B may be different from each other.

[0085] The present embodiment is characterized in that first elastic wave resonator 10A as an acoustic coupling filter is connected to second elastic wave resonator 10B having IDT electrode 31, and second elastic wave resonator 10B is a series arm resonator. Thus, when elastic wave device 10 is used in a filter device, the filter device can be miniaturized and degradation of filter characteristics can be suppressed. This is described below by comparing the present embodiment with the first comparative example.

[0086] The first comparative example is different from the first embodiment in that it does not include a second elastic wave resonator. The transmission characteristics of the first embodiment and the first comparative example were derived through simulation. The design parameters of the elastic wave device 10 having the structure of the first embodiment are as follows.

[0087] Piezoelectric layer: Material…Z-cut LiNbO3, thickness…400nm

[0088] First electrode finger, second electrode finger and third electrode finger: material…Al, thickness…400nm, width…420nm

[0089] Fourth electrode finger and fifth electrode finger: material…Al, thickness…400nm, width…420nm

[0090] Center-to-center distance p1 in the first elastic wave resonator: 1.4 μm

[0091] Center-to-center distance p2 in the second elastic wave resonator: 1 μm

[0092] Figure 6 is a diagram showing the passing characteristics of the first embodiment and the first comparative example. Figure 6 , the S21 passing characteristic is shown.

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

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

[0095] And, by Figure 6 The double-dashed line in FIG. 1 shows a frequency band on the high-frequency side of the passband in the first embodiment and the first comparative example. Figure 6 As shown, in the first embodiment, the attenuation amount on the high frequency side of the passband is larger than that in the first comparative example. Thus, in the first embodiment, the attenuation characteristic as the filter characteristic can be improved.

[0096] like Figure 1 As in the first embodiment shown, when the second elastic wave resonator 10B is a series arm resonator, p2<p1 is preferably satisfied. Thus, even when the second elastic wave resonator 10B does not have a frequency adjustment film, a notch characteristic can be more reliably formed on the high frequency side of the passband. Thus, the attenuation characteristic can be more reliably improved.

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

[0098] like Figure 1 As shown, connection wiring 28 is provided on first principal surface 14a of piezoelectric layer 14. Connection wiring 28 is connected to a reference potential. Third bus bar 24 serving as a connection electrode of first elastic wave resonator 10A is connected to connection wiring 28. Third bus bar 24 is connected to the reference potential via connection wiring 28.

[0099] In the first embodiment, first bus bar 22 of first elastic wave resonator 10A and fifth bus bar 33 of second elastic wave resonator 10B are integrally formed bus bars. The bus bars are shared by first elastic wave resonator 10A and second elastic wave resonator 10B. However, first bus bar 22 and fifth bus bar 33 may be provided separately.

[0100] like Figure 2 As shown, the support member 13 includes a support substrate 16 and an insulating layer 15. The piezoelectric substrate 12 is a stack of the support substrate 16, the insulating layer 15, and the piezoelectric layer 14. That is, the piezoelectric layer 14 and the support member 13 overlap when viewed from a direction in which the first principal surface 14a and the second principal surface 14b of the piezoelectric layer 14 face each other.

[0101] As the material of the support substrate 16, for example, a semiconductor such as silicon, a ceramic such as aluminum oxide, etc. can be used. As the material of the insulating layer 15, an appropriate dielectric such as silicon oxide or tantalum oxide can be used.

[0102] 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 first embodiment, a supporting member 13 and a piezoelectric film are arranged so that a part of the supporting member 13 and a part of the piezoelectric film are opposed to each other across the cavity 10a. However, the recess in the supporting member 13 may also be provided throughout the insulating layer 15 and the supporting substrate 16. Alternatively, the recess provided only in the supporting substrate 16 may be blocked by the insulating layer 15. The recess may also be provided in the piezoelectric layer 14, for example. It should be noted that the cavity 10a may also be a through hole provided in the supporting member 13.

[0103] The cavity 10a is the acoustic reflection portion in the present invention. The acoustic reflection portion can be used to effectively confine the energy of the elastic wave on the piezoelectric layer 14 side. The acoustic reflection portion can be provided at a position overlapping at least a portion of the functional electrode 11 in the support member 13 when viewed from above. More specifically, when viewed from above, at least a portion of each of the first electrode finger 25, the second electrode finger 26, and the third electrode finger 27 can overlap with the acoustic reflection portion. Preferably, when viewed from above, a plurality of excitation regions C overlap with the acoustic reflection portion.

[0104] In this specification, a top view refers to a view from the direction equivalent to Figure 2 The upper direction in FIG. 1 is viewed along the stacking direction of the support member 13 and the piezoelectric film. Figure 2In the embodiment of the present invention, for example, the piezoelectric layer 14 side of the support substrate 16 side and the piezoelectric layer 14 side is the upper side. In addition, in this specification, the top view has the same meaning as the view from the main surface opposite direction. The main surface opposite direction refers to the direction in which the first main surface 14a and the second main surface 14b of the piezoelectric layer 14 are opposite to each other. More specifically, the main surface opposite direction is, for example, the normal direction of the first main surface 14a.

[0105] Although not shown, Figure 5 The second elastic wave resonator 10B shown in the figure is also provided with an acoustic reflection portion. The acoustic reflection portion of the second elastic wave resonator 10B may be provided at a position in the support member 13 that overlaps with at least a portion of the IDT electrode 31 in a plan view. More specifically, in a plan view, at least a portion of each of the fourth electrode finger 35 and the fifth electrode finger 36 may overlap with the acoustic reflection portion. Preferably, in a plan view, a plurality of excitation regions in the second elastic wave resonator 10B overlap with the acoustic reflection portion.

[0106] It should be noted that the sound reflecting portion may be a sound reflecting film such as a multi-layered film described later. For example, a sound reflecting film may be provided on the surface of the supporting member.

[0107] In the first embodiment, in the first elastic wave resonator 10A, the center-to-center distance p1 is fixed. However, the center-to-center distance p1 between the adjacent first electrode fingers 25 and the third electrode fingers 27 and the center-to-center distance p1 between the adjacent second electrode fingers 26 and the third electrode fingers 27 may not be fixed. In this case, the longest distance among the center-to-center distance p1 between the adjacent first electrode fingers 25 and the third electrode fingers 27 and the center-to-center distance p1 between the adjacent second electrode fingers 26 and the third electrode fingers 27 is set to p. It should be noted that, as in the first embodiment, when the center-to-center distance p1 is fixed, the center-to-center distance p1 between any adjacent electrode fingers is the distance p.

[0108] The first piezoelectric layer of the first elastic wave resonator 10A is the first piezoelectric film in the present invention. When the thickness of the first piezoelectric film is set to d, d / p is preferably less than 0.5, and d / p is more preferably less than 0.24. As a result, in the first elastic wave resonator 10A, the body wave of the thickness shear mode is appropriately excited. It should be noted that in the first embodiment, the thickness d is the thickness of the piezoelectric layer 14 as the first piezoelectric layer.

[0109] In the second elastic wave resonator 10B, when the longest distance among the center-to-center distances p2 of the adjacent fourth electrode fingers 35 and fifth electrode fingers 36 is set to p and the thickness of the piezoelectric layer 14 as the second piezoelectric layer is set to d, d / p is preferably 0.5 or less. More preferably, d / p is 0.24 or less. Thus, in the second elastic wave resonator 10B, the thickness shear mode body wave is appropriately excited. It should be noted that, as in the first embodiment, when the center-to-center distance p2 is fixed, the center-to-center distance p2 between any adjacent electrode fingers is also the distance p.

[0110] It should be noted that the first elastic wave resonator of the present invention may not necessarily be configured to utilize body waves in the thickness shear mode. For example, the first elastic wave resonator of the present invention may also be configured to excite plate waves. In this case, the excitation region is Figure 3 The intersection region E is shown. Similarly, the second elastic wave resonator can also be configured to excite plate waves.

[0111] As described above, in the first embodiment, the piezoelectric layer 14 includes Z-cut LiNbO3. However, the piezoelectric layer 14 may also include rotated Y-cut lithium niobate. In this case, the fractional bandwidth of the first elastic wave resonator 10A depends on the Euler angles (φ, θ, ψ) of the lithium niobate used in the piezoelectric layer 14. When the resonant frequency is fr and the antiresonant frequency is fa, the fractional bandwidth is represented by (|fa-fr| / fr)×100[%].

[0112] The relationship between the fractional bandwidth of first elastic wave resonator 10A and the Euler angles (φ, θ, ψ) of piezoelectric layer 14 was derived when d / p was made as close to 0 as possible. It should be noted that φ in the Euler angles is 0°.

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

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

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

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

[0117] (0°±10°, 180°-40°[(1-(ψ-90) 2 / 8100)] 1 / 2 ~180°, any ψ) …Formula (3)

[0118] The range of the Euler angles of the above-mentioned equation (1), equation (2), or equation (3) is preferably 0. This allows the fractional bandwidth to be sufficiently widened. This allows the elastic wave device 10 including the first elastic wave resonator 10A to be suitably used in a filter device.

[0119] like Figure 3 As shown in the first embodiment, the third electrode 19 has a third bus bar 24 as a connecting electrode and a plurality of third electrode fingers 27. The third electrode 19 is a comb-shaped electrode. However, the third electrode 19 may not be a comb-shaped electrode. For example, Figure 8 In the first modification of the first embodiment shown, the third electrode 49 has a meandering shape. In this modification, the insulating film 29 is not provided on the piezoelectric layer 14. Moreover, the connection electrode 44 includes only a portion equivalent to the plurality of first connection electrodes 24A in the first embodiment. The connection electrode 44 of this modification is not a third bus bar.

[0120] More specifically, the third electrode 39 has a plurality of connection electrodes 44 located on the first bus bar 22 side and a plurality of connection electrodes 44 located on the second bus bar 23 side. The front end portions of two adjacent third electrode fingers 27 on the first bus bar 22 side or the front end portions on the second bus bar 23 side are connected to each other through the connection electrodes 44. For example, a third electrode finger 27 other than the two ends of the electrode finger in the orthogonal direction among the plurality of third electrode fingers 27 is connected to one connection electrode 44 at both the front end portions on the first bus bar 22 side and the front end portions on the second bus bar 23 side. The third electrode finger 27 is connected to the third electrode fingers 27 on both sides through each connection electrode 44. By repeating this structure, the shape of the third electrode 39 becomes a meandering shape.

[0121] In this modification, first elastic wave resonator 40A as an acoustic coupling filter is also connected to second elastic wave resonator 10B similar to the first embodiment. Second elastic wave resonator 10B is a series arm resonator. Thus, when the elastic wave device is used in a filter device, the filter device can be miniaturized and the degradation of the filter characteristics can be suppressed.

[0122] However, the second elastic wave resonator 10B may also include a frequency adjustment film. Fig. 9 In the second modification of the first embodiment shown, a frequency adjustment film 48 is provided on the first principal surface 14a of the piezoelectric layer 14 as the second piezoelectric layer so as to cover the IDT electrode 31. The material of the frequency adjustment film 48 can be silicon oxide or silicon nitride, for example.

[0123] It should be noted that the second elastic wave resonator 40B is a series arm resonator. In this modification, the second elastic wave resonator 40B is also connected to the first elastic wave resonator 10A as the acoustic coupling filter similar to the first embodiment.

[0124] By adjusting the thickness of frequency adjustment film 48, the notch characteristic of second elastic wave resonator 40B can be more reliably formed on the high frequency side of the passband of the elastic wave device. Therefore, the attenuation characteristic can be more reliably improved. Therefore, in this modification, when the elastic wave device is used in a filter device, the miniaturization of the filter device can be promoted, and the attenuation characteristic as a filter characteristic can be more reliably improved.

[0125] Fig.10 FIG. 1 is a schematic plan view of a first elastic wave resonator according to the second embodiment. Fig.11 1 is a schematic front cross-sectional view showing the vicinity of first to third electrode fingers in the second embodiment.

[0126] like Fig.10 and Fig.11 As shown, the present embodiment is different from the first embodiment in that the third electrode 19 is provided on the second principal surface 14b of the piezoelectric layer 14. Except for the above-mentioned aspects, the elastic wave device of the present embodiment has the same structure as the elastic wave device 10 of the first embodiment. It should be noted that the first elastic wave resonator 50A is connected to the second elastic wave resonator 10B which is a series arm resonator similar to the first embodiment.

[0127] The configuration of the third electrode 19 in the present embodiment in a plan view is the same as that in the first embodiment. Therefore, in a plan view, the plurality of third electrode fingers 27 are respectively provided on the second main surface 14b of the piezoelectric layer 14 so as to be arranged with the first electrode fingers 25 and the second electrode fingers 26 in the direction in which the first electrode fingers 25 and the second electrode fingers 26 are arranged. In a plan view, the order in which the plurality of electrode fingers are arranged is the order in which the first electrode fingers 25, the third electrode fingers 27, the second electrode fingers 26, and the third electrode fingers 27 are arranged as one period when starting from the first electrode fingers 25.

[0128] In this embodiment as well, similarly to the first embodiment, when the elastic wave device is used in a filter device, the size of the filter device can be reduced and degradation of the filter characteristics can be suppressed.

[0129] Fig.12 It is a schematic plan view of an elastic wave device according to a third embodiment.

[0130] The present embodiment is different from the first embodiment in that second elastic wave resonator 60B is a parallel arm resonator. The present embodiment is also different from the first embodiment in that the relationship between the center distance p1 of first elastic wave resonator 10A and the center distance p2 of second elastic wave resonator 60B is p2>2p1. Except for the above points, elastic wave device 60 of the present embodiment has the same structure as elastic wave device 10 of the first embodiment.

[0131] In the present embodiment, when elastic wave device 60 is used in a filter device, the filter device can be miniaturized and degradation of filter characteristics can be suppressed. This will be described below by comparing the present embodiment with the second comparative example.

[0132] The second comparative example is different from the third embodiment in that the second elastic wave resonator is not provided. The transmission characteristics of the third embodiment and the second comparative example were derived by simulation. The design parameters of the elastic wave device 60 having the structure of the third embodiment are as follows.

[0133] Piezoelectric layer: Material…Z-cut LiNbO3, thickness…400nm

[0134] First electrode finger, second electrode finger and third electrode finger: material…Al, thickness…400nm, width…420nm

[0135] Fourth electrode finger and fifth electrode finger: material…Al, thickness…400nm, width…420nm

[0136] Center-to-center distance p1 in the first elastic wave resonator: 1.4 μm

[0137] Center-to-center distance p2 in the second elastic wave resonator: 7 μm

[0138] Fig.13 is a diagram showing the passing characteristics of the third embodiment and the second comparative example. Fig.13 , the S21 passing characteristic is shown.

[0139] like Fig.13 As shown, in the third embodiment, a filter waveform can be obtained appropriately. Therefore, when the elastic wave device 60 is used in a filter device, even if the number of elastic wave resonators constituting the filter device is small, a filter waveform can be obtained appropriately. Therefore, the miniaturization of the filter device can be promoted.

[0140] And, by Fig.13 The area surrounded by the double-dashed line in FIG. 1 shows the vicinity of the low-frequency end of the passband in the third embodiment and the second comparative example. Fig.13 As shown, in the third embodiment, the steepness becomes higher near the end of the low-frequency side in the passband compared to the second comparative example. In this specification, high steepness means that the change in frequency relative to a certain fixed attenuation change near the end of the passband is small. In the third embodiment, the steepness as a filter characteristic can be improved.

[0141] like Fig.12 As shown in the third embodiment, when the second elastic wave resonator 60B is a parallel arm resonator, p2>p1 is preferably satisfied, and p2>2p1 is more preferably satisfied. Thus, even when the second elastic wave resonator 60B does not have a frequency adjustment film, a notch characteristic can be more reliably formed on the low-frequency side of the passband. Thus, the steepness can be more reliably improved on the low-frequency side of the passband.

[0142] It should be noted that the second elastic wave resonator 60B may also be connected to Fig. 9 The second variation of the first embodiment shown also has a frequency adjustment film 48. In this case, by adjusting the thickness of the frequency adjustment film 48, a notch characteristic can be more reliably formed on the low-frequency side of the passband. Thus, the steepness can be more reliably improved on the low-frequency side of the passband.

[0143] In the first to third embodiments, examples are shown in which one first elastic wave resonator and one second elastic wave resonator are provided. However, the elastic wave device of the present invention only needs to include at least one first elastic wave resonator and at least one second elastic wave resonator. The fourth embodiment shows an example in which a plurality of first elastic wave resonators and a plurality of second elastic wave resonators are provided.

[0144] Fig.14It is a schematic plan view of an elastic wave device according to a fourth embodiment.

[0145] The elastic wave device 70 includes two first elastic wave resonators 70A and 70C, and two second elastic wave resonators 70B and 70D. The first elastic wave resonators 70A and 70C are configured similarly to the first embodiment. However, the design parameters of the first elastic wave resonators 70A and 70C may be different depending on the desired electrical characteristics.

[0146] Second elastic wave resonator 70B and second elastic wave resonator 70D each have IDT electrode 31. Second elastic wave resonator 70B is a series arm resonator. On the other hand, second elastic wave resonator 70D is a parallel arm resonator. It should be noted that both second elastic wave resonator 70B and second elastic wave resonator 70D may be series arm resonators. Both second elastic wave resonator 70B and second elastic wave resonator 70D may be parallel arm resonators.

[0147] In elastic wave device 70 , second elastic wave resonator 70B, first elastic wave resonator 70A, and first elastic wave resonator 70C are sequentially connected in series with each other. Second elastic wave resonator 70D, which is a parallel arm resonator, is connected to first elastic wave resonator 70C.

[0148] In elastic wave device 70 , the connected elastic wave resonators share a bus bar. However, bus bars may be provided separately for each first elastic wave resonator and each second elastic wave resonator.

[0149] Third bus bar 24 of first elastic wave resonator 70A and third bus bar 24 of first elastic wave resonator 70C are connected to the same connection wiring 28. A bus bar of second elastic wave resonator 70D that is not shared with first elastic wave resonator 70C is connected to connection wiring 28. Connection wiring 28 is connection wiring 28 to which third bus bar 24 is connected. The bus bar of second elastic wave resonator 70D, third bus bar 24 of first elastic wave resonator 70A, and third bus bar 24 of first elastic wave resonator 70C are connected to a reference potential via the same connection wiring 28. However, the arrangement of the elastic wave resonators and connection wiring 28 in elastic wave device 70 is not limited to that described above.

[0150] The plurality of first elastic wave resonators and the plurality of second elastic wave resonators in elastic wave device 70 share piezoelectric substrate 12 and piezoelectric layer 14. It should be noted that each elastic wave resonator may have its own piezoelectric layer. Each elastic wave resonator may have its own piezoelectric substrate.

[0151] In this embodiment, similarly to the first embodiment, when elastic wave device 70 is used in a filter device, even if the number of elastic wave resonators constituting the filter device is small, an appropriate filter waveform can be obtained, thereby promoting miniaturization of the filter device.

[0152] Furthermore, elastic wave device 70 includes both a series arm resonator and a parallel arm resonator having IDT electrode 31. This improves attenuation characteristics on the high-frequency side of the passband and increases steepness on the low-frequency side of the passband.

[0153] The relationship between the center distance p2 of second elastic wave resonator 70B as a series arm resonator and the center distance p1 of at least one of first elastic wave resonator 70A and first elastic wave resonator 70C is preferably p2<p1. This can more reliably improve the attenuation characteristics at higher frequencies than the passband.

[0154] The relationship between the center distance p2 of second elastic wave resonator 70D as a parallel arm resonator and the center distance p1 of at least one of first elastic wave resonator 70A and first elastic wave resonator 70C is preferably p2>p1. The relationship is more preferably p2>2p1. This can more reliably improve the steepness on the low-frequency side of the passband.

[0155] The following describes the details of the thickness shear mode using an example in which the functional electrode is an IDT electrode. The "electrode" in the IDT electrode described later is equivalent to the electrode finger. The elastic wave device in the following example is an elastic wave resonator. The supporting member in the following example is equivalent to the supporting substrate in the present invention. In the following, the reference potential is sometimes recorded as the ground potential.

[0156] Fig.15 (a) is a perspective view showing a schematic diagram of the appearance of an elastic wave device using a thickness shear mode bulk wave, Fig.15 (b) is a top view showing the electrode structure on the piezoelectric layer. Fig.16 It is along Fig.15 (a) A partial cross-sectional view along line AA.

[0157] The elastic wave device 1 has a piezoelectric layer 2 including LiNbO3. The piezoelectric layer 2 may also include LiTaO3. The cutting angle of LiNbO3 and LiTaO3 is Z-cut, but may also be a rotated Y-cut or X-cut. The thickness of the piezoelectric layer 2 is not particularly limited, but in order to effectively excite the thickness shear mode, it is preferably greater than 40nm and less than 1000nm, and more preferably greater than 50nm and less than 1000nm. The piezoelectric layer 2 has a first principal surface 2a and a second principal surface 2b facing each other. An electrode 3 and an electrode 4 are provided on the first principal surface 2a. Here, electrode 3 is an example of a "first electrode", and electrode 4 is an example of a "second electrode". In Fig.15 (a) and Fig.15 In (b), a plurality of electrodes 3 are connected to a first bus bar 5. A plurality of electrodes 4 are connected to a second bus bar 6. The plurality of electrodes 3 and the plurality of electrodes 4 are interlaced with each other. The electrodes 3 and the electrodes 4 have a rectangular shape and a length direction. In a direction orthogonal to the length direction, the electrode 3 is opposed to an adjacent electrode 4. The length directions of the electrodes 3 and 4 and the directions orthogonal to the length directions of the electrodes 3 and 4 are directions intersecting with the thickness direction of the piezoelectric layer 2. Therefore, the electrode 3 and the adjacent electrode 4 can also be said to be opposed 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 replaced with directions orthogonal to the length direction of the electrodes 3 and 4. Fig.15 (a) and Fig.15 The direction is perpendicular to the length direction of the electrodes 3 and 4 shown in (b). That is, Fig.15 (a) and Fig.15 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.15 (a) and Fig.15The electrodes 3 and 4 in (b) extend in the direction in which the electrodes 3 and 4 extend. Moreover, a pair of structures in which multiple pairs of electrodes 3 connected to one potential and electrodes 4 connected to another potential are adjacent are provided in a direction orthogonal to the length direction of the electrodes 3 and 4. Here, the electrodes 3 and 4 being adjacent does not mean that the electrodes 3 and 4 are arranged in direct contact, but means that the electrodes 3 and 4 are arranged with a gap. In addition, when the electrodes 3 and 4 are adjacent, no electrodes including other electrodes 3 and 4 connected to the signal electrode or the ground electrode are arranged between the electrodes 3 and 4. The number of pairs does not need to be an integer pair, and may also be 1.5 pairs or 2.5 pairs. The center-to-center distance between the electrodes 3 and 4, i.e., 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, i.e., the dimension 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. It should be noted that the center-to-center distance between electrodes 3 and 4 is the distance obtained by 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.

[0158] In addition, in the elastic wave device 1, a Z-cut piezoelectric layer is used, and therefore, the direction perpendicular to the length direction of the electrodes 3 and 4 is perpendicular to the polarization direction of the piezoelectric layer 2. This is not limited to the case where a piezoelectric body with another cutting angle is used as the piezoelectric layer 2. Here, "orthogonal" is not limited to the case of being strictly orthogonal, and may 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°).

[0159] On the second main surface 2b side of the piezoelectric layer 2, a support member 8 is stacked via an insulating layer 7. The insulating layer 7 and the support member 8 have a frame-like shape. Fig.16 As shown, there are through holes 7a and 8a. A cavity 9 is formed thereby. 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. It should be noted that the insulating layer 7 may not be provided. Therefore, the support member 8 can be directly or indirectly stacked on the second main surface 2b of the piezoelectric layer 2.

[0160] 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 on the side of the piezoelectric layer 2 can be (100), (110), or (111). The Si constituting the supporting member 8 is preferably a high resistor with a resistivity of more than 4 kΩcm. However, the supporting member 8 can also be composed of suitable insulating materials or semiconductor materials.

[0161] 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.

[0162] The plurality of electrodes 3, 4 and the first bus bar 5 and the second bus bar 6 are made of a suitable metal or alloy such as Al or AlCu alloy. In the elastic wave device 1, the electrodes 3, 4 and the first bus bar 5 and the second bus bar 6 have a structure in which an Al film is stacked on a Ti film. It should be noted that an adhesion layer other than a Ti film may also be used.

[0163] During driving, an AC voltage is applied between the plurality of electrodes 3 and the plurality of electrodes 4. More specifically, an AC voltage is applied between the first bus bar 5 and the second bus bar 6. Thus, it is possible to obtain a resonance characteristic of a body wave utilizing a thickness shear mode excited in the piezoelectric layer 2. In addition, in the elastic wave device 1, when the thickness of the piezoelectric layer 2 is set to d and the center-to-center distance between any adjacent electrodes 3 and 4 in the plurality of pairs of electrodes 3 and 4 is set to p, d / p is less than 0.5. Therefore, it is possible to effectively excite the body wave of the thickness shear mode mentioned above and obtain a good resonance characteristic. More preferably, d / p is less than 0.24, in which case a better resonance characteristic can be obtained.

[0164] 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 for miniaturization, it is difficult to cause a decrease in the Q value. 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.17 (a) and Fig.17 (b) is used to explain the difference between the Lamb wave used in the elastic wave device and the body wave of the thickness shear mode mentioned above.

[0165] Fig.17(a) is a schematic front cross-sectional view for explaining the Lamb wave propagating through the piezoelectric film of the elastic wave device described in the 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 opposite 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.17 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, since the waves propagate in the X direction, reflectors are arranged on both sides to obtain resonance characteristics. Therefore, wave propagation loss occurs, and when miniaturization is achieved, that is, when the number of pairs of electrode fingers is reduced, the Q value decreases.

[0166] In contrast, Fig.17 As shown in (b), in the elastic wave device 1, the vibration displacement is in the thickness shear direction, so the wave propagates and resonates roughly along the direction connecting the first main surface 2a and the second main surface 2b of the piezoelectric layer 2, that is, the Z direction. That is, the X-direction component of the wave is significantly smaller than the Z-direction component. Moreover, the resonance characteristic is 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 difficult to generate propagation loss. Moreover, even if the number of pairs of electrode pairs including electrodes 3 and 4 is reduced in order to promote miniaturization, it is difficult to generate a decrease in the Q value.

[0167] It should be noted that if Fig.18 As shown, the amplitude directions of the body waves in the thickness shear mode are opposite in the first region 451 included in the excitation region C of the piezoelectric layer 2 and the second region 452 included in the excitation region C. Fig.18 , 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.

[0168] As described above, elastic wave device 1 includes at least one pair of electrodes 3 and 4 , but since waves are not propagated in the X direction, there is no need to have a plurality of pairs of electrodes 3 and 4 . In other words, at least one pair of electrodes is sufficient.

[0169] 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, as described above, at least one pair of electrodes is an electrode connected to the signal potential or an electrode connected to the ground potential, and no floating electrode is provided.

[0170] Fig.19 It is shown Fig.16 The resonance characteristics of the elastic wave device shown in FIG. 1 are shown in FIG. 1 . The design parameters of the elastic wave device 1 for obtaining the resonance characteristics are as follows.

[0171] Piezoelectric layer 2: LiNbO3 with Euler angles (0°, 0°, 90°), thickness = 400 nm.

[0172] When observed in a direction orthogonal to the length direction of electrode 3 and electrode 4, the length of the area where electrode 3 and electrode 4 overlap, 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.

[0173] Insulating layer 7: a silicon oxide film having a thickness of 1 μm.

[0174] Supporting member 8: Si.

[0175] It should be noted that 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 .

[0176] In elastic wave device 1 , the inter-electrode distances of the electrode pairs including electrodes 3 and 4 are all equal in a plurality of pairs. In other words, electrodes 3 and electrodes 4 are arranged at equal intervals.

[0177] according to Fig.19 It is clear that, despite the absence of a reflector, a good resonance characteristic with a fractional bandwidth of 12.5% ​​is obtained.

[0178] However, 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. 20 This is explained.

[0179] and get Fig.19 The elastic wave devices having the same resonance characteristics as shown above are obtained by changing d / p. Fig. 20 3 is a graph showing the relationship between d / p and the fractional bandwidth of a resonator as an elastic wave device.

[0180] according to Fig. 20It is clear that when d / p>0.5, even if d / p is adjusted, the fractional bandwidth is less than 5%. In contrast, when d / p≤0.5, if d / p is changed within this range, the fractional 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 fractional bandwidth can be made as high as 7% or more. In addition, if d / p is adjusted within this range, a resonator with a wider fractional 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.

[0181] Fig.21 80 is a top view of an elastic wave device using a thickness shear mode bulk wave. In the elastic wave device 80, a pair of electrodes including an electrode 3 and an electrode 4 are provided on the first principal surface 2a of the piezoelectric layer 2. It should be noted that Fig.21 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 one pair. Even in this case, if the above d / p is 0.5 or less, a thickness shear mode body wave can be effectively excited.

[0182] In the elastic wave device 1, it is preferred that the metallization ratio MR of any adjacent electrodes 3 and 4 among the plurality of electrodes 3 and 4 with respect to the excitation region C satisfies MR≤1.75(d / p)+0.075, and the excitation region C is a region where the adjacent electrodes 3 and 4 overlap when viewed in opposite directions. In this case, the stray light can be effectively reduced. Fig. 22 and Fig.23 This is explained. Fig. 22 This is a reference diagram showing an example of the resonance characteristics of the elastic wave device 1. Spurious signals indicated by arrows B appear between the resonance frequency and the antiresonance frequency. It should be noted that d / p=0.08 and the Euler angles of LiNbO3 are (0°, 0°, 90°). In addition, the metallization ratio MR is set to 0.35.

[0183] Reference Fig.15 (b) will explain the metallization ratio MR. Fig.15In 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 excitation region C refers to the region of electrode 3 that overlaps with electrode 4, the region of electrode 4 that overlaps with electrode 3, and the region between electrode 3 and electrode 4 that overlaps with electrode 3 and electrode 4 when observing electrode 3 and electrode 4 in a direction orthogonal to the length direction of electrodes 3 and 4, that is, in the opposing direction. And, the area of ​​electrodes 3 and 4 in the excitation region C relative to the area of ​​the excitation region C becomes the metallization ratio MR. That is, the metallization ratio MR is the ratio of the area of ​​the metallized portion to the area of ​​the excitation region C.

[0184] It should be noted that, when a plurality of pairs of electrodes are provided, the ratio of the total area of ​​the metallized portions included in the entire excitation region to the area of ​​the excitation region may be defined as MR.

[0185] Fig.23 This is a diagram showing the relationship between the fractional bandwidth and the phase rotation amount of the impedance of the stray normalized by 180 degrees when a plurality of elastic wave resonators are formed according to the structure of the elastic wave device 1. It should be noted that the fractional bandwidth was adjusted by making various changes to the film thickness of the piezoelectric layer and the size of the electrode. In addition, Fig.23 This is the result obtained when a piezoelectric layer composed of LiNbO 3 was used in a Z-cut manner, but the same tendency is observed when a piezoelectric layer having other cut angles is used.

[0186] exist Fig.23 In the area enclosed by the ellipse J in , the spurious value is as large as 1.0. Fig.23 It is clear that when the fractional bandwidth exceeds 0.17, that is, exceeds 17%, even if the parameters constituting the fractional bandwidth are changed, large spurious signals with a spurious level of 1 or more appear in the passband. Fig. 22 As shown in the resonance characteristics, large spurious signals indicated by arrow B appear in the frequency band. Therefore, the fractional bandwidth is preferably 17% or less. In this case, spurious signals can be reduced by adjusting the film thickness of the piezoelectric layer 2, the dimensions of the electrodes 3 and 4, and the like.

[0187] Fig.24 : is a graph showing the relationship between d / 2p, metallization ratio MR, and fractional bandwidth. In the above-mentioned elastic wave device, various elastic wave devices having different d / 2p and MR were constructed, and the fractional bandwidth was measured. Fig.24The hatched portion on the right side of the dotted line D is an area where the fractional 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 fractional bandwidth less than 17%. More preferred is Fig.24 The region to the right of MR=3.5(d / 2p)+0.05 indicated by the dashed line D1 in FIG. In other words, if MR≤1.75(d / p)+0.05, the fractional bandwidth can be reliably made 17% or less.

[0188] Fig.25 This is a diagram showing a mapping of the fractional 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.25 The multiple regions R shown with hatching are regions where the fractional bandwidth is 2% or more. It should be noted that when φ in the Euler angle (φ, θ, ψ) is within the range of 0°±5°, the relationship between θ and ψ and the fractional bandwidth is the same as Fig.25 Even when the piezoelectric layer includes lithium tantalate (LiTaO3), the relationship between θ and ψ in the Euler angle (in the range of 0°±5°, θ, ψ) and BW is the same as Fig.25 The relationships shown are the same.

[0189] Therefore, if the Euler angles (φ, θ, ψ) of lithium niobate or lithium tantalate constituting the piezoelectric layer are within the range of 0°±5°, and θ and φ are Fig.25 If the fractional bandwidth is within the range of any of the plurality of regions R shown, it is possible to sufficiently widen the fractional bandwidth, which is preferable.

[0190] Fig.26 It is a front cross-sectional view of an elastic wave device having an acoustic multilayer membrane.

[0191] In the elastic wave device 81, an acoustic multilayer film 82 is stacked on the second main surface 2b of the piezoelectric layer 2. The acoustic multilayer film 82 has a stacked structure of low acoustic impedance layers 82a, 82c, 82e with relatively low acoustic impedance and high acoustic impedance layers 82b, 82d with relatively high acoustic impedance. When the acoustic multilayer film 82 is used, the bulk wave of the thickness shear mode can be confined in the piezoelectric layer 2 even without using the cavity 9 in the elastic wave device 1. In the elastic wave device 81, by setting the above d / p to 0.5 or less, the resonance characteristics of the bulk wave based on the thickness shear mode can be obtained. It should be noted that in the acoustic multilayer film 82, the number of stacked low acoustic impedance layers 82a, 82c, 82e and high acoustic impedance layers 82b, 82d is not particularly limited. It is sufficient as long as at least one high acoustic impedance layer 82b, 82d is arranged on the side farther from the piezoelectric layer 2 than the low acoustic impedance layers 82a, 82c, 82e.

[0192] The low acoustic impedance layers 82a, 82c, 82e and the high acoustic impedance layers 82b, 82d may be made of any suitable material as long as the above-mentioned acoustic impedance relationship is satisfied. For example, silicon oxide or silicon oxynitride may be used as the material of the low acoustic impedance layers 82a, 82c, 82e. In addition, alumina, silicon nitride or metal may be used as the material of the high acoustic impedance layers 82b, 82d.

[0193] Fig. 27 This is a partially cutaway perspective view for explaining an elastic wave device using Lamb waves.

[0194] The elastic wave device 91 has a support substrate 92. A recessed portion opened on the upper surface of the support substrate 92 is provided. A piezoelectric layer 93 is stacked on the support substrate 92. Thus, a cavity 9 is formed. An IDT electrode 94 is provided on the piezoelectric layer 93 above the cavity 9. Reflectors 95 and 96 are provided on both sides of the IDT electrode 94 in the direction of propagation of elastic waves. Fig. 27 , the outer periphery of the cavity 9 is shown by a dotted line. Here, the IDT electrode 94 has a first bus bar 94a, a second bus bar 94b, and a plurality of first electrode fingers 94c and a plurality of second electrode fingers 94d. The plurality of first electrode fingers 94c are connected to the first bus bar 94a. The plurality of second electrode fingers 94d are connected to the second bus bar 94b. The plurality of first electrode fingers 94c and the plurality of second electrode fingers 94d are interlaced with each other.

[0195] In elastic wave device 91, Lamb waves as plate waves are excited by applying an alternating electric field to IDT electrode 94 on cavity 9. Since reflectors 95 and 96 are provided on both sides, resonance characteristics based on the Lamb waves can be obtained.

[0196] Thus, the elastic wave resonator in the present invention can also utilize plate waves. Fig. 27 In the example shown, Figure 1 The IDT electrode 94, the reflector 95, and the reflector 96 are provided on the principal surface corresponding to the first principal surface 14a of the piezoelectric layer 14 shown in the figure. On the other hand, in the first elastic wave resonator of the present invention, a pair of comb-shaped electrodes and a plurality of third electrode fingers are provided on the first principal surface 14a. In the case where the first elastic wave resonator of the present invention uses plate waves, a pair of comb-shaped electrodes and a plurality of third electrode fingers and the above-mentioned reflectors 95 and 96 may be provided on the first principal surface 14a of the piezoelectric layer 14 in the first to fourth embodiments and each modified example. In this case, the reflectors 95 and 96 may be separated by a pair of comb-shaped electrodes and a plurality of third electrode fingers in the direction orthogonal to the electrode fingers.

[0197] When the second elastic wave resonator of the present invention utilizes plate waves, the IDT electrode and the reflectors 95 and 96 may be provided on the first principal surface 14a of the piezoelectric layer 14 in the first to fourth embodiments and the respective modifications. In this case, the reflectors 95 and 96 may be provided across the IDT electrode in the direction orthogonal to the electrode fingers.

[0198] In the elastic wave devices of the first to fourth 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.26 The acoustic multilayer film 82 shown. Specifically, the supporting member and the piezoelectric film may be configured so that at least a portion of the supporting member and at least a portion of the piezoelectric film are opposed to each other via the acoustic multilayer film 82. In this case, in the acoustic multilayer film 82, low acoustic impedance layers and high acoustic impedance layers may be alternately stacked. The acoustic multilayer film 82 may also be an acoustic reflection portion in an elastic wave device.

[0199] In the first elastic wave resonator of the first to fourth embodiments and their respective modified examples using a thickness shear mode bulk wave, as described above, d / p is preferably 0.5 or less, and more preferably 0.24 or less. This allows for better resonance characteristics to be obtained. The same is true for the second elastic wave resonator of the first to fourth embodiments and their respective modified examples using a thickness shear mode bulk wave.

[0200] Furthermore, in the excitation region of the first elastic wave resonator in the first to fourth embodiments and each modified example using the thickness shear mode body wave, as described above, MR ≤ 1.75 (d / p) + 0.075 is preferably satisfied. More specifically, when the metallization ratios of the first electrode finger and the third electrode finger and the second electrode finger and the third electrode finger with respect to the excitation region are set to MR, MR ≤ 1.75 (d / p) + 0.075 is preferably satisfied. In this case, spurious emission can be suppressed more reliably. The same is true for the excitation region of the second elastic wave resonator in the first to fourth embodiments and each modified example using the thickness shear mode body wave.

[0201] Description of Reference Numerals

[0202] 1…Elastic wave device;

[0203] 2… piezoelectric layer;

[0204] 2a, 2b ... first main surface, second main surface;

[0205] 3, 4…electrodes;

[0206] 5, 6…first bus bar, second bus bar;

[0207] 7…Insulation layer;

[0208] 7a…through hole;

[0209] 8…supporting member;

[0210] 8a…through hole;

[0211] 9…cavity;

[0212] 10…Elastic wave device;

[0213] 10A, 10B ... a first elastic wave resonator, a second elastic wave resonator;

[0214] 10a…cavity;

[0215] 11…Functional electrode;

[0216] 12… piezoelectric substrate;

[0217] 13…supporting member;

[0218] 14… piezoelectric layer;

[0219] 14a, 14b ... a first main surface, a second main surface;

[0220] 15…insulation layer;

[0221] 16...support base plate;

[0222] 17, 18…a first comb-shaped electrode, a second comb-shaped electrode;

[0223] 19 ... a third electrode;

[0224] 22-24…1st bus bar to 3rd bus bar;

[0225] 24A, 24B...a first connecting electrode, a second connecting electrode;

[0226] 24a…bar;

[0227] 24b…protrusion;

[0228] 25-27…first electrode finger to third electrode finger;

[0229] 28…Connection wiring;

[0230] 29…Insulating film;

[0231] 31…IDT electrode;

[0232] 32, 33…the fourth bus bar, the fifth bus bar;

[0233] 35, 36…a fourth electrode finger and a fifth electrode finger;

[0234] 39 ... a third electrode;

[0235] 40A, 40B: a first elastic wave resonator and a second elastic wave resonator;

[0236] 44…connecting electrodes;

[0237] 48…Frequency adjustment membrane;

[0238] 49 ... a third electrode;

[0239] 50A…First elastic wave resonator;

[0240] 60…Elastic wave device;

[0241] 60B…second elastic wave resonator;

[0242] 70…Elastic wave device;

[0243] 70A, 70B: a first elastic wave resonator and a second elastic wave resonator;

[0244] 70C, 70D: a first elastic wave resonator and a second elastic wave resonator;

[0245] 80, 81… elastic wave device;

[0246] 82…Acoustic multilayer film;

[0247] 82a, 82c, 82e ... low acoustic impedance layer;

[0248] 82b, 82d ... high acoustic impedance layer;

[0249] 91…Elastic wave device;

[0250] 92...support base plate;

[0251] 93…Piezoelectric layer;

[0252] 94…IDT electrode;

[0253] 94a, 94b ... a first bus bar, a second bus bar;

[0254] 94c, 94d ... a first electrode finger, a second electrode finger;

[0255] 95, 96…reflector;

[0256] 201…Piezoelectric film;

[0257] 201a, 201b ... a first main surface, a second main surface;

[0258] 451, 452… first area, second area;

[0259] C…Incentive area;

[0260] E…intersection area;

[0261] R…Region;

[0262] VP1…imaginary plane.

Claims

1. An elastic wave device comprising: A first elastic wave resonator having a first piezoelectric film including a first piezoelectric layer including a piezoelectric body; and at least one second elastic wave resonator electrically connected to the first elastic wave resonator, comprising a second piezoelectric film including a second piezoelectric layer and an IDT electrode disposed on the second piezoelectric layer, the second piezoelectric layer including a piezoelectric body, The first elastic wave resonator comprises: A first comb-shaped electrode, which is disposed on the first piezoelectric layer and has a first bus bar and a plurality of first electrode fingers, one end of which is respectively connected to the first bus bar, wherein the first comb-shaped electrode is connected to an input potential; a second comb-shaped electrode, which is disposed on the first piezoelectric layer and has a second bus bar and a plurality of second electrode fingers, one end of which is respectively connected to the second bus bar and interlaced with the plurality of first electrode fingers, and the second comb-shaped electrode is connected to an output potential; and a third electrode having a plurality of third electrode fingers and a connecting electrode connecting adjacent third electrode fingers to each other, wherein the plurality of third electrode fingers are respectively arranged on the first piezoelectric layer so that, in a plan view, the third electrode is arranged with the first electrode fingers and the second electrode fingers in the direction in which the first electrode fingers and the second electrode fingers are arranged, and the third electrode is connected to a potential different from that of the first comb-shaped electrode and the second comb-shaped electrode, The first electrode finger, the second electrode finger, and the third electrode finger are arranged in a sequence that forms a period starting from the first electrode finger. The IDT electrode of the second elastic wave resonator has a plurality of fourth electrode fingers and a plurality of fifth electrode fingers that are interlaced with each other. The second elastic wave resonator is a series arm resonator or a parallel arm resonator.

2. The elastic wave device according to claim 1, wherein: The elastic wave device includes a plurality of the second elastic wave resonators. The plurality of second elastic wave resonators include both the second elastic wave resonators that are series arm resonators and the second elastic wave resonators that are parallel arm resonators.

3. The elastic wave device according to claim 2, wherein: When the center-to-center distance between the adjacent first electrode finger and the third electrode finger and the adjacent second electrode finger and the third electrode finger in the first elastic wave resonator is set to p1, and the center-to-center distance between the adjacent fourth electrode finger and the fifth electrode finger in the second elastic wave resonator is set to p2, the relationship between p1 in the first elastic wave resonator and p2 in the second elastic wave resonator as a parallel arm resonator is p2>p1.

4. The elastic wave device according to claim 2 or 3, wherein: When the center-to-center distance between the adjacent first electrode finger and the third electrode finger and the adjacent second electrode finger and the third electrode finger in the first elastic wave resonator is set to p1, and the center-to-center distance between the adjacent fourth electrode finger and the fifth electrode finger in the second elastic wave resonator is set to p2, the relationship between p1 in the first elastic wave resonator and p2 in the second elastic wave resonator as a series arm resonator is p2<p1.

5. The elastic wave device according to claim 1, wherein: The elastic wave device includes one second elastic wave resonator, wherein the second elastic wave resonator is a parallel arm resonator. When the center-to-center distance between the adjacent first electrode finger and the third electrode finger and the adjacent second electrode finger and the third electrode finger in the first elastic wave resonator is set to p1, and the center-to-center distance between the adjacent fourth electrode finger and the fifth electrode finger in the second elastic wave resonator is set to p2, the relationship between p1 in the first elastic wave resonator and p2 in the second elastic wave resonator is p2>p1.

6. The elastic wave device according to any one of claims 3 to 5, wherein: The relationship between p1 in the first elastic wave resonator and p2 in the second elastic wave resonator as a parallel arm resonator is p2>2p1.

7. The elastic wave device according to claim 1, wherein: The elastic wave device includes one second elastic wave resonator, wherein the second elastic wave resonator is a series arm resonator. When the center-to-center distance between the adjacent first electrode finger and the third electrode finger and the adjacent second electrode finger and the third electrode finger in the first elastic wave resonator is set to p1, and the center-to-center distance between the adjacent fourth electrode finger and the fifth electrode finger in the second elastic wave resonator is set to p2, the relationship between p1 in the first elastic wave resonator and p2 in the second elastic wave resonator is p2<p1.

8. The elastic wave device according to any one of claims 1 to 7, wherein: The first piezoelectric layer and the second piezoelectric layer are the same piezoelectric layer, and the first elastic wave resonator and the at least one second elastic wave resonator share the same piezoelectric layer.

9. The elastic wave device according to any one of claims 1 to 8, wherein: The first elastic wave resonator is configured to utilize a thickness shear mode bulk wave.

10. The elastic wave device according to any one of claims 1 to 8, wherein: The first elastic wave resonator further includes a supporting member stacked on the first piezoelectric film. In a plan view along the stacking direction of the support member and the first piezoelectric film, an acoustic reflection portion is formed at a position of the support member overlapping with the plurality of first electrode fingers, the plurality of second electrode fingers, and the plurality of third electrode fingers, When the longest distance between the centers of the first and third adjacent electrode fingers and the second and third adjacent electrode fingers in the first elastic wave resonator is set to p, and when the thickness of the first piezoelectric film is set to d, d / p is less than 0.

5.

11. The elastic wave device according to claim 10, wherein: d / p is less than 0.

24.

12. The elastic wave device according to claim 10 or 11, wherein: The sound reflecting portion is a cavity portion, and the supporting member and the first piezoelectric film are arranged so that a portion of the supporting member and a portion of the first piezoelectric film face each other with the cavity portion interposed therebetween.

13. The elastic wave device according to claim 10 or 11, 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 first piezoelectric film are configured so that at least a portion of the supporting member and at least a portion of the first piezoelectric film are opposite to each other via the acoustic reflection membrane.

14. The elastic wave device according to any one of claims 10 to 13, wherein: When the direction orthogonal to the direction in which the first electrode finger, the second electrode finger, and the third electrode finger extend is set as the electrode finger orthogonal direction, the area where the adjacent first electrode finger and the third electrode finger overlap in the electrode finger orthogonal direction and the area between the centers of the adjacent first electrode finger and the third electrode finger, and the area where the adjacent second electrode finger and the third electrode finger overlap in the electrode finger orthogonal direction and the area between the centers of the adjacent second electrode finger and the third electrode finger are the excitation area, When the metallization ratio of the first electrode finger and the third electrode finger and the second electrode finger and the third electrode finger with respect to the excitation region is MR, MR≦1.75(d / p)+0.075 is satisfied.

15. The elastic wave device according to any one of claims 1 to 14, wherein: The first piezoelectric layer includes lithium niobate, The Euler angles (φ, θ, ψ) of lithium niobate constituting the first piezoelectric layer are within the range of the following formula (1), formula (2) or formula (3), (within the range of 0°±10°, 0°~25°, arbitrary ψ) …Formula (1) (Within the range of 0°±10°, 25°~100°, 0°~75°[(1-(θ-50) 2 / 2500)] 1 / 2 Or 180°-75°[(1-(θ-50) 2 / 2500)] 1 / 2 ~180°) …Formula (2) (0°±10°, 180°-40°[(1-(ψ-90) 2 / 8100)] 1 / 2 ~180°, arbitrary ψ) …Equation (3).

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