Elastic wave device

Abstract

Provided is an elastic wave device with which it is possible to reduce the size of a filter device and to reduce the resistance of a wiring connected to a reference potential. An elastic wave device (10) according to the present invention is provided with: a piezoelectric substrate (12) including a piezoelectric layer (14) having a first main surface (14a) and a second main surface (14b) that face each other, and a support member laminated on the second main surface (14b) of the piezoelectric layer (14); a first comb electrode (17) that is provided on a first main surface (14a) of the piezoelectric layer (14), has a first bus bar (22) and a plurality of first electrode fingers (25) each of which has one end connected to the first bus bar (22), and is connected to an input potential; a second comb electrode (18) that is provided on the first main surface (14a) of the piezoelectric layer (14), that has a second bus bar (23) and a plurality of second electrode fingers (26) each having one end connected to the second bus bar (23), and that is connected to the output potential, the plurality of second electrode fingers (26) and the plurality of first electrode fingers (25) being interleaved with each other; and a reference potential electrode (19). A plurality of third electrode fingers (27) which are respectively provided on the first main surface (14a) of the piezoelectric layer (14) so as to be aligned 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; a plurality of connection electrodes which are respectively connected to the plurality of third electrode fingers (27); and a third bus bar (24) which is electrically connected to the plurality of third electrode fingers (27) via the plurality of connection electrodes. And is connected to a reference potential. The order in which the first electrode fingers (25), the second electrode fingers (26), and the third electrode fingers (27) are arranged is such that the first electrode fingers (25), the third electrode fingers (27), the second electrode fingers (26), and the third electrode fingers (27) are arranged in one cycle from the first electrode fingers (25). The third bus bar (24) is provided so as to face the plurality of third electrode fingers (27) with at least the piezoelectric layer (14) interposed therebetween. The plurality of connection electrodes connect the third bus bar (24) and the plurality of third electrode fingers (27) by penetrating at least the piezoelectric layer (14).

Description

Technical Field

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

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

[0003] Prior Art Literature

[0004] Patent Literature

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

[0006] Problem that the invention aims to solve

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

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

[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 structure: the structure in which an electrode connected to a reference potential is arranged between an electrode connected to an input potential and an electrode connected to an output potential.

[0010] However, the inventors have also found that, in the above structure, the layout of the electrode connected to the reference potential is greatly restricted, and the width of the electrode is easily narrowed and the length of the electrode is easily lengthened. In this case, the resistance of the electrode connected to the reference potential is easily increased, and the potential of the electrode is easily unstable. Therefore, when used in a filter device, the filter characteristics of the filter device may be degraded.

[0011] An object of the present invention is to provide an elastic wave device that can reduce the size of a filter device and reduce the resistance of a wiring connected to a reference potential.

[0012] Technical solutions to solve problems

[0013] In a broad aspect of the elastic wave device involved in the present invention, it comprises: a piezoelectric substrate, including a piezoelectric layer having a first main surface and a second main surface facing each other, and a supporting member stacked on the second main surface of the piezoelectric layer; a first comb-shaped electrode, arranged on the first main surface of the piezoelectric layer, having a first bus bar and a plurality of first electrode fingers each having one end connected to the first bus bar, and connected to an input potential; a second comb-shaped electrode, arranged on the first main surface of the piezoelectric layer, having a second bus bar and a plurality of second electrode fingers each having one end connected to the second bus bar, and connected to an output potential, the plurality of second electrode fingers being interlaced with the plurality of first electrode fingers; and a reference potential electrode, having a plurality of third electrode fingers, a plurality of connecting electrodes and a third bus bar, and connected to a reference potential, the plurality of third electrode fingers The plurality of connecting electrodes are respectively arranged on the first main surface of the piezoelectric layer so as to be parallel to the first electrode finger and the second electrode finger in the direction in which the first electrode finger and the second electrode finger are arranged. The plurality of connecting electrodes are respectively connected to the plurality of third electrode fingers. The third bus bar is electrically connected to the plurality of third electrode fingers through the plurality of connecting electrodes. The order in which the first electrode finger, the second electrode finger and the third electrode finger are arranged is an order in which the first electrode finger, the third electrode finger, the second electrode finger and the third electrode finger are set as a period when starting from the first electrode finger. The third bus bar is set to be opposite to the plurality of third electrode fingers with at least the piezoelectric layer sandwiched therebetween. The plurality of connecting electrodes connect the third bus bar and the plurality of third electrode fingers by at least penetrating the piezoelectric layer.

[0014] In other broad aspects of the elastic wave device involved in the present invention, it comprises: a piezoelectric substrate including a piezoelectric layer having a first main surface and a second main surface facing each other; a first comb-shaped electrode arranged on the first main surface of the piezoelectric layer, having a first bus bar and a plurality of first electrode fingers each having one end connected to the first bus bar, and connected to an input potential; a second comb-shaped electrode arranged on the first main surface of the piezoelectric layer, having a second bus bar and a plurality of second electrode fingers each having one end connected to the second bus bar, and connected to an output potential, the plurality of second electrode fingers being interlaced with the plurality of first electrode fingers; a reference potential electrode having a plurality of third electrode fingers, a plurality of connecting electrodes and a third bus bar, and connected to a reference potential, the plurality of third electrode fingers being arranged on the first main surface of the piezoelectric layer so as to be aligned with the first electrode fingers in the direction in which the first electrode fingers and the second electrode fingers are arranged. The electrode fingers and the second electrode fingers are arranged side by side, the plurality of connecting electrodes are respectively connected to the plurality of third electrode fingers, and the third bus bar is electrically connected to the plurality of third electrode fingers through the plurality of connecting electrodes; a support body is arranged on the piezoelectric substrate; and a cover member is arranged on the support body, having a third main surface located on the piezoelectric substrate side, and a fourth main surface opposite to the third main surface, the order in which the first electrode finger, the second electrode finger and the third electrode finger are arranged starting from the first electrode finger is the order in which the first electrode finger, the third electrode finger, the second electrode finger and the third electrode finger are set as a period, the third bus bar is arranged on the third main surface of the cover member so as to be opposite to the plurality of third electrode fingers, the plurality of connecting electrodes are at least arranged on the plurality of third electrode fingers, and the third bus bar is connected to the plurality of third electrode fingers.

[0015] In another broad aspect of the elastic wave device involved in the present invention, it comprises: a piezoelectric substrate including a piezoelectric layer having a first main surface and a second main surface facing each other; a first comb-shaped electrode arranged on the first main surface of the piezoelectric layer, having a first bus bar and a plurality of first electrode fingers each having one end connected to the first bus bar, and connected to an input potential; a second comb-shaped electrode arranged on the first main surface of the piezoelectric layer, having a second bus bar and a plurality of second electrode fingers each having one end connected to the second bus bar, and connected to an output potential, the plurality of second electrode fingers being interlaced with the plurality of first electrode fingers; a reference potential electrode having a plurality of third electrode fingers, a plurality of connecting electrodes and a third bus bar, and connected to a reference potential, the plurality of third electrode fingers being respectively arranged on the first main surface of the piezoelectric layer so as to be aligned with the first electrode fingers and the second electrode fingers in the direction in which the first electrode fingers and the second electrode fingers are arranged. The piezoelectric substrate comprises a piezoelectric substrate having a plurality of conductive bonding members, a piezoelectric substrate having a fifth main surface and a sixth main surface opposite to the fifth main surface. The first electrode finger, the second electrode finger and the third electrode finger are arranged in a sequence that forms a period when the first electrode finger is started. The third bus bar is arranged on the fifth main surface of the mounting substrate so as to be opposite to the third electrode fingers. The plurality of connecting electrodes are arranged on at least the third electrode fingers to connect the third bus bar to the third electrode fingers.

[0016] Effects of the Invention

[0017] According to the present invention, it is possible to provide an elastic wave device that can reduce the size of a filter device and reduce the resistance of a wiring connected to a reference potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic front cross-sectional view of the elastic wave device according to the first embodiment of the present invention.

[0019] Figure 2 It is a schematic plan view of the elastic wave device according to the first embodiment of the present invention.

[0020] Figure 3 It is along Figure 2 Schematic cross-sectional view along line II-II in FIG.

[0021] 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.

[0022] Figure 5 It is a diagram showing the transmission characteristics and reflection characteristics of the elastic wave device according to the first embodiment of the present invention.

[0023] Figure 6 It is a schematic plan view of the elastic wave device according to the first reference example.

[0024] Figure 7 It is a schematic plan view of an elastic wave device according to a second reference example.

[0025] Figure 8 1 is a schematic front cross-sectional view showing the vicinity of a portion where the first electrode finger is covered with an insulating film in the second reference example.

[0026] Fig. 9 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.

[0027] Fig.10 This is a diagram showing a modification of the first embodiment of the present invention corresponding to the Figure 2 A schematic cross-sectional view of a portion of the cross section taken along line II-II.

[0028] Fig.11 It is a schematic front cross-sectional view of an elastic wave device according to a second embodiment of the present invention.

[0029] Fig.12 This is a schematic front cross-sectional view showing an enlarged portion of an elastic wave device according to a second embodiment of the present invention.

[0030] Fig.13 It is a schematic plan view showing an electrode structure on the first principal surface of the piezoelectric layer in the second embodiment of the present invention.

[0031] Fig.14 It is a schematic front cross-sectional view of an elastic wave device according to a third embodiment of the present invention.

[0032] Fig.15 This is a schematic front cross-sectional view showing an enlarged portion of an elastic wave device according to a third embodiment of the present invention.

[0033] Fig.16 (a) is a schematic perspective view showing the appearance of an elastic wave device using a thickness shear mode bulk wave, Fig.16 (b) is a top view showing the electrode structure on the piezoelectric layer.

[0034] Fig.17 It is along Fig.16 (a) is a cross-sectional view of a portion taken along line AA.

[0035] Fig.18 (a) is a schematic front cross-sectional view for explaining Lamb waves propagating through a piezoelectric film of an elastic wave device. Fig.18 (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.

[0036] Fig.19 It is a diagram showing the amplitude direction of the body wave in the thickness shear mode.

[0037] Fig. 20 FIG. 1 is a diagram showing the resonance characteristics of an elastic wave device using bulk waves in a thickness shear mode.

[0038] Fig.21 : 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 represented by p and the thickness of the piezoelectric layer is represented by d.

[0039] Fig. 22 This is a top view of an elastic wave device using thickness shear mode bulk waves.

[0040] Fig.23 FIG. 2 is a diagram showing the resonance characteristics of an elastic wave device according to a reference example in which spurious emission occurs.

[0041] Fig.24 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.

[0042] Fig.25 It is a graph showing the relationship between d / 2p and the metallization ratio MR.

[0043] Fig.26 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.

[0044] Fig. 27 It is a front cross-sectional view of an elastic wave device having an acoustic multilayer membrane.

[0045] Fig.28 This is a partially cutaway perspective view for explaining an elastic wave device using Lamb waves. DETAILED DESCRIPTION

[0046] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings to make the present invention clear.

[0047] In addition, it should be noted that each embodiment described in this specification is an example, and some structures can be replaced or combined among different embodiments.

[0048] Figure 1 It is a schematic front cross-sectional view of the elastic wave device according to the first embodiment of the present invention. Figure 2 is a schematic plan view of the elastic wave device according to the first embodiment. Figure 1 It is along Figure 2 Schematic cross-sectional view of line II in FIG. Figure 2 In FIG. 1 , hatching is performed to indicate each electrode. Figure 2 In FIG. 1 , the reference potential symbol is used to schematically indicate that the reference potential electrode described later is connected to the reference potential. Figure 2 Similarly, in other schematic plan views, electrodes may be hatched and reference potential symbols may be used.

[0049] Figure 1 The elastic wave device 10 shown is configured to utilize the thickness shear mode. The elastic wave device 10 is an acoustic coupling filter. The structure of the elastic wave device 10 will be described below.

[0050] The elastic wave device 10 has a piezoelectric substrate 12 and a functional electrode 11. The piezoelectric substrate 12 has a supporting member 13 and a piezoelectric layer 14. In the present embodiment, the supporting member 13 includes a supporting substrate 16 and an insulating layer 15. The insulating layer 15 is provided on the supporting substrate 16. The piezoelectric layer 14 is provided on the insulating layer 15. However, the supporting member 13 may also be composed of only the supporting substrate 16. In addition, the supporting member 13 may not necessarily be provided.

[0051] 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 face each other. Of the first principal surface 14a and the second principal surface 14b, the second principal surface 14b is located on the support member 13 side.

[0052] like Figure 2 As shown, the functional electrode 11 includes a pair of comb-shaped electrodes and a reference potential electrode 19. The reference potential electrode 19 is connected to a reference potential. 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.

[0053] 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.

[0054] The first bus bar 22 and the second bus bar 23 face each other. The plurality of first electrode fingers 25 and the plurality of second electrode fingers 26 are interlaced with each other. The first electrode fingers 25 and the second electrode fingers 26 are alternately arranged in a direction perpendicular to the direction in which the first electrode fingers 25 and the second electrode fingers 26 extend.

[0055] Figure 3 It is along Figure 2 Schematic cross-sectional view along line II-II in FIG.

[0056] The reference potential electrode 19 has a third bus bar 24, a plurality of third electrode fingers 27, and a plurality of connection electrodes 28. 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 extend parallel to the plurality of first electrode fingers 25. Hereinafter, the direction in which the first electrode fingers 25, the second electrode fingers 26, and the third electrode fingers 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.

[0057] The third bus bar 24 is provided on the second main surface 14b of the piezoelectric layer 14. The third bus bar 24 extends in the direction perpendicular to the electrode fingers. The third bus bar 24 is provided to face the plurality of third electrode fingers 27 across the piezoelectric layer 14. However, the direction in which the third bus bar 24 extends is not limited to the above.

[0058] The plurality of connection electrodes 28 are provided so as to penetrate the piezoelectric layer 14 . One connection electrode 28 connects one third electrode finger 27 and the third bus bar 24 . That is, the plurality of third electrode fingers 27 are electrically connected to the third bus bar 24 via the plurality of connection electrodes 28 .

[0059] In addition, the third bus bar 24 only needs to be arranged to face the plurality of third electrode fingers 27 with at least the piezoelectric layer 14 sandwiched therebetween. Specifically, for example, the third bus bar 24 may also face the plurality of third electrode fingers 27 with the piezoelectric layer 14 and other layers sandwiched therebetween. The plurality of connecting electrodes 28 only needs to connect the third bus bar 24 and the plurality of third electrode fingers 27 by penetrating at least the piezoelectric layer 14 in the piezoelectric substrate 12.

[0060] like Figure 2As shown, in the present embodiment, the third electrode fingers 27 are all arranged between the first electrode fingers 25 and the second electrode fingers 26. Therefore, in the direction in which the first electrode fingers 25 and the second electrode fingers 26 are arranged, the first electrode fingers 25, the second electrode fingers 26, and the third electrode fingers 27 are arranged. When the direction in which the first electrode fingers 25, the second electrode fingers 26, and the third electrode fingers 27 are arranged is set as the electrode finger arrangement direction, the electrode finger arrangement direction is the electrode finger orthogonal direction. Hereinafter, the first electrode fingers 25, the second electrode fingers 26, and the third electrode fingers 27 are sometimes collectively referred to as electrode fingers.

[0061] Figure 4 : is a schematic front cross-sectional view showing the vicinity of the first electrode finger to the third electrode finger in the first embodiment. Figure 4 Shows that there is no Figure 3 The cross section of the connecting electrode 28 is shown. Figure 1 The same applies to the parts shown.

[0062] like Figure 4 As shown, the order of arrangement of the plurality of electrode fingers, starting from the first electrode finger 25, is the order of setting the first electrode finger 25, the third electrode finger 27, the second electrode finger 26, and the third electrode finger 27 as one cycle. Therefore, the order of arrangement of the plurality of electrode fingers 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. In the functional electrode 11, the electrode finger at the end in the orthogonal direction of the electrode finger may be any type of electrode finger among the first electrode finger 25, the second electrode finger 26, and the third electrode finger 27. For example, in Figure 2 In the illustrated embodiment, the second electrode fingers 26 are electrode fingers located at both ends in the direction orthogonal to the electrode fingers.

[0063] The elastic wave device 10 has a plurality of terminals electrically connected to the outside. In the present embodiment, these terminals are configured as electrode pads. Each comb-shaped electrode and the reference potential electrode 19 are electrically connected to these terminals via appropriate wiring. Furthermore, the first comb-shaped electrode 17 is connected to the input potential. The second comb-shaped electrode 18 is connected to the output potential. The reference potential electrode 19 is connected to the reference potential. In addition, each of the above-mentioned terminals can also be configured as wiring.

[0064] The elastic wave device 10 is an elastic wave resonator configured to utilize bulk waves in a thickness shear mode. Figure 2 As shown, the elastic wave device 10 has a plurality of excitation regions C. In the plurality of excitation regions C, body waves in the thickness shear mode and elastic waves in other modes are excited. Figure 2 In FIG, only two excitation areas C among multiple excitation areas C are shown.

[0065] A part of the plurality of excitation regions C among all the excitation regions C is an area where adjacent first electrode fingers 25 and third electrode fingers 27 overlap each other when viewed from the direction orthogonal to the electrode fingers, and is an area between the centers of adjacent first electrode fingers 25 and third electrode fingers 27. The remaining plurality of excitation regions C is an area where adjacent second electrode fingers 26 and third electrode fingers 27 overlap each other when viewed from the direction orthogonal to the electrode fingers, and is an area 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. In addition, the excitation region C is an area of ​​the piezoelectric layer 14 defined based on the structure of the functional electrode 11.

[0066] The present embodiment is characterized by the following structures: 1) The third electrode finger 27 of the reference potential electrode 19 is located between the first electrode finger 25 of the first comb-shaped electrode 17 and the second electrode finger 26 of the second comb-shaped electrode 18. 2) Figure 3 The plurality of connecting electrodes 28 shown connect the third bus bar 24 and the plurality of third electrode fingers 27 by penetrating the piezoelectric layer 14. Accordingly, when the elastic wave device 10 is used in a filter device, the filter device can be miniaturized and the resistance of the wiring connected to the reference potential can be reduced. This is described below.

[0067] Depend on Figure 5 An example of the transmission characteristic and reflection characteristic of the elastic wave device 10 is shown.

[0068] Figure 5 : is a diagram showing the transmission characteristic and reflection characteristic of the elastic wave device according to the first embodiment. Figure 5 The results of FEM (Finite Element Method) simulation are shown.

[0069] like Figure 5 As shown in FIG. 1 , it can be seen that a filter waveform can be appropriately obtained even in one elastic wave device 10. The elastic wave device 10 is an acoustic coupling type filter. More specifically, Figure 2 As shown, the elastic wave device 10 includes an excitation region C located between the centers of the adjacent first electrode fingers 25 and third electrode fingers 27, and an excitation region C located between the centers of the adjacent second electrode fingers 26 and third electrode fingers 27. Elastic waves of multiple modes including a body wave of a thickness shear mode are excited in these excitation regions C. By combining these modes, a filter waveform can be appropriately obtained even in one elastic wave device 10.

[0070] When elastic wave device 10 is used as an elastic wave resonator in a filter device, even if the number of elastic wave resonators constituting the filter device is one or less, a suitable filter waveform can be obtained, thereby promoting miniaturization of the filter device.

[0071] In addition, if Figure 3 As shown in FIG. 1 , in this embodiment, the reference potential electrode 19 is three-dimensionally configured. This can shorten the length of the reference potential electrode 19 compared to a structure in which the reference potential electrode 19 is routed only on one main surface of the piezoelectric layer 14 .

[0072] In more detail, for example, Figure 6 In the first reference example shown, the reference potential electrode 109 is provided only on the first principal surface 14a of the piezoelectric layer 14. The portion of the reference potential electrode 109 provided between the first comb-shaped electrode 17 and the second comb-shaped electrode 18 has a meandering shape. Therefore, the entire length of the reference potential electrode 109 is long.

[0073] The reference potential electrode 109 is connected to the reference potential via a terminal electrically connected to the outside. The reference potential electrode 109 has a portion corresponding to a plurality of third electrode fingers. In the reference potential electrode 109, between the portion corresponding to the third electrode finger located near the center and the above-mentioned terminal, there is a portion corresponding to a plurality of third electrode fingers. Therefore, the length of the reference potential electrode 109 from the portion corresponding to the third electrode finger located near the center to the portion connected to the above-mentioned terminal is particularly long.

[0074] In contrast, Figure 2 In the present embodiment shown, one end of each third electrode finger 27 is connected to the third bus bar 24. Furthermore, the third bus bar 24 is connected to a terminal electrically connected to the outside. Therefore, the length of the reference potential electrode 19 from the third electrode finger 27 to the portion of the reference potential electrode 19 connected to the terminal can be shortened regardless of the position of the third electrode finger 27. Therefore, the resistance of the reference potential electrode 19 can be reduced.

[0075] In this case, it is possible to improve the stability of the potential of reference potential electrode 19. According to this, when elastic wave device 10 is used in a filter device, it is possible to suppress degradation of the filter characteristics of the filter device.

[0076] In addition, if Figure 7 As in the second reference example shown in FIG. 1 , it is also possible to three-dimensionally form the reference potential electrode 119 on the first main surface 14a of the piezoelectric layer 14. Specifically, Figure 7 as well as Figure 8As shown, in the second reference example, a portion of the first electrode finger 25 is covered by the insulating film 115. The third bus bar 114 is provided on the first main surface 14a of the piezoelectric layer 14, on the third electrode finger 27, and on the insulating film 115. However, a wiring connected to the signal potential is provided on the first main surface 14a. Therefore, the degree of freedom of the layout of the reference potential electrode 119 is low. Therefore, the length of the wiring connected to the reference potential is sometimes longer as a whole.

[0077] In contrast, Figure 3 In the present embodiment shown, the third bus bar 24 is provided on the second main surface 14b of the piezoelectric layer 14. The second main surface 14b has a high degree of freedom in layout. Therefore, on the second main surface 14b, it is possible to easily provide wiring for connecting the reference potential electrode 19 to the reference potential without increasing the size of the elastic wave device 10.

[0078] like Figure 2 As shown, the width of the third bus bar 24 is preferably wider than the width of the third electrode finger 27. According to this, the resistance of the reference potential electrode 19 can be effectively reduced. In addition, the width of the third bus bar 24 is the dimension of the third bus bar 24 along the direction orthogonal to the direction in which the third bus bar 24 extends. The width of the third electrode finger 27 is the dimension of the third electrode finger 27 along the direction orthogonal to the electrode finger.

[0079] As described above, the second main surface 14 b of the piezoelectric layer 14 has a high degree of freedom in layout. Therefore, the width of the third bus bar 24 can be easily increased.

[0080] Hereinafter, the structure of this embodiment will be described in more detail.

[0081] like Figure 1 As shown, the support member 13 includes a support substrate 16 and an insulating layer 15. The piezoelectric substrate 12 is a stack of the support substrate 16, the insulating layer 15, and the piezoelectric layer 14. That is, when viewed from the direction in which the first principal surface 14a and the second principal surface 14b of the piezoelectric layer 14 are opposite, the piezoelectric layer 14 and the support member 13 overlap.

[0082] As the material of the support substrate 16, for example, semiconductors such as silicon, ceramics such as aluminum oxide, etc. can be used. As the material of the insulating layer 15, appropriate dielectrics such as silicon oxide or tantalum oxide can be used. The piezoelectric layer 14 is, for example, a lithium niobate layer such as a LiNbO3 layer or a lithium tantalate layer such as a LiTaO3 layer.

[0083] The insulating layer 15 is provided with a hollow portion. That is, the insulating layer 15 has a hollow portion as the cavity 10a. In the present embodiment, the insulating layer 15 covers the second main surface 14b of the piezoelectric layer 14. Figure 3As shown, the insulating layer 15 covers the third bus bar 24 in the reference potential electrode 19 .

[0084] but, Figure 1 The structure of the cavity 10a shown is not limited to the above. For example, a recess may be provided in the insulating layer 15. A piezoelectric layer 14 may be provided on the insulating layer 15 so as to block the recess. Thus, the cavity 10a may be formed. In this case, the supporting member 13 and the piezoelectric layer 14 are configured so that a part of the supporting member 13 and a part of the piezoelectric layer 14 are opposed to each other with the cavity 10a sandwiched therebetween. The recess in the supporting member 13 may also be provided to extend over 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. In addition, the cavity 10a may also be a through hole provided in the supporting member 13.

[0085] The cavity 10a is the acoustic reflection portion in the present invention. The acoustic reflection portion can effectively confine the energy of the elastic wave on the piezoelectric layer 14 side. In a plan view, the acoustic reflection portion only needs to be arranged at a position overlapping with at least a portion of the functional electrode 11 in the support member 13. More specifically, in a plan view, at least a portion of each of the first electrode finger 25, the second electrode finger 26, and the third electrode finger 27 overlaps with the acoustic reflection portion. It is preferred that a plurality of excitation regions C overlap with the acoustic reflection portion in a plan view.

[0086] In this specification, the term "top view" refers to a view from the Figure 1 The upper direction in FIG. 1 is viewed along the stacking direction of the support member 13 and the piezoelectric layer 14. Figure 1 For example, the piezoelectric layer 14 side is the upper side of the support substrate 16 side and the piezoelectric layer 14 side. In addition, in this specification, the top view is defined as the same as the observation from the main surface facing direction. The so-called main surface facing direction is the direction in which the first main surface 14a and the second main surface 14b of the piezoelectric layer 14 are facing each other. More specifically, the main surface facing direction is, for example, the normal direction of the first main surface 14a.

[0087] In addition, the sound reflecting portion may be a sound reflecting film such as a sound multilayer film described later. For example, a sound reflecting film may be provided on the surface of the supporting member.

[0088] In the first embodiment, the center-to-center distances of the adjacent multiple pairs of first electrode fingers 25 and third electrode fingers 27 are the same as the center-to-center distances of the adjacent multiple pairs of second electrode fingers 26 and third electrode fingers 27. In this case, when the thickness of the piezoelectric layer 14 is set to d and the center-to-center distances of the adjacent electrode fingers are set to p, it is preferred that d / p is less than 0.5. It is more preferred that d / p is less than 0.24. Thus, the body wave of the thickness shear mode can be appropriately excited.

[0089] However, the distance between the centers of the adjacent first electrode fingers 25 and the third electrode fingers 27 and the distance between the centers of the adjacent second electrode fingers 26 and the third electrode fingers 27 may not be constant. In this case, it is preferred that the longest distance between the distance between the centers of the adjacent first electrode fingers 25 and the third electrode fingers 27 and the distance between the centers of the adjacent second electrode fingers 26 and the third electrode fingers 27 be set to p. In this case, it is preferred that d / p be less than 0.5, and it is more preferred that d / p be less than 0.24. In addition, the elastic wave device of the present invention may not necessarily be configured to utilize the thickness shear mode.

[0090] like Figure 2 As shown, when viewed from the orthogonal direction of the electrode fingers, the area where the adjacent first electrode finger 25 and the third electrode finger 27, or the adjacent second electrode finger 26 and the third electrode finger 27 overlap each other is the intersection area E. The intersection area E includes a plurality of excitation areas C. The elastic wave device according to the present invention can also be configured to utilize plate waves. In this case, the excitation area is the intersection area E.

[0091] In a plan view, the third bus bar 24 overlaps a portion including one end of each third electrode finger 27. Thus, the third electrode finger 27 can be arranged between the first electrode finger 25 and the second electrode finger 26 without making the third electrode finger 27 too long. The length of the third electrode finger 27 is the dimension of the third electrode finger 27 along the electrode finger extending direction.

[0092] In a plan view, the third bus bar 24 is provided in a portion overlapping with an area outside the electrode finger extending direction of the intersection region E. Specifically, in a plan view, the third bus bar 24 overlaps with an area between the first bus bar 22 and the plurality of second electrode fingers 26. Alternatively, in a plan view, the third bus bar 24 may overlap with an area between the second bus bar 23 and the plurality of first electrode fingers 25.

[0093] In the present embodiment, the piezoelectric layer 14 is a lithium niobate layer. Specifically, a rotated Y-cut LiNbO3 is used as the material of the piezoelectric layer 14. In this case, the fractional bandwidth of the elastic wave device 10 depends on the Euler angles (φ, θ, ψ) of the lithium niobate used for the piezoelectric layer 14. The so-called fractional bandwidth is represented by (|fa-fr| / fr)×100[%] when the resonant frequency is fr and the antiresonant frequency is fa.

[0094] The relationship between the fractional bandwidth of elastic wave device 10 and the Euler angles (φ, θ, ψ) of piezoelectric layer 14 was derived when d / p was made as close to 0 as possible. In addition, φ in the Euler angles was set to 0°.

[0095] Fig. 9This 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.

[0096] Fig. 9 The region R indicated by the hatching is the region where the fractional bandwidth of at least 2% can be obtained. In addition, when φ in the Euler angles (φ, θ, ψ) is within the range of 0°±10°, the relationship between θ and ψ and the fractional bandwidth is the same as Fig. 9 When the piezoelectric layer 14 is a lithium tantalate layer, and when φ is in the range of 0°±10°, the relationship between θ and ψ and the fractional bandwidth is the same as Fig. 9 The relationship shown is the same. If the range of the region R is approximated, it becomes a range represented by the following formula (1), formula (2) and formula (3).

[0097] (within the range of 0°±10°, 0°~25°, arbitrary ψ) …Formula (1)

[0098] (0°±10°, 25°~100°, 75°[(1-(θ-50) 2 / 2500)] 1 / 2 or 180°-75°[(1-(θ-50) 2 / 2500)] 1 / 2 ~180°) …Formula (2)

[0099] (0°±10°, 180°-40°[(1-(ψ-90) 2 / 8100)] 1 / 2 ~180°, any ψ) …Formula (3)

[0100] The range of the Euler angles of the above-mentioned formula (1), formula (2), or formula (3) is preferably 0. This can sufficiently widen the fractional bandwidth. Thus, elastic wave device 10 can be appropriately used in a filter device.

[0101] in addition, Figure 3 The position of the third bus bar 24 where the reference potential electrode 19 is provided is not limited to the second main surface 14b of the piezoelectric layer 14. Fig.10 In the variation of the first embodiment shown, the third bus bar 24 is provided on the insulating layer 15. The third bus bar 24 is located in the cavity. The third bus bar 24 faces the piezoelectric layer 14 with the insulating layer 15 interposed therebetween. Furthermore, the third bus bar 24 faces a plurality of third electrode fingers 27 with the insulating layer 15 and the piezoelectric layer 14 interposed therebetween. Each connection electrode 28 penetrates the piezoelectric layer 14 and the insulating layer 15. Each third electrode finger 27 is electrically connected to the third bus bar 24 via each connection electrode 28.

[0102] In addition, the third bus bar 24 may be buried in the insulating layer 15. Specifically, the third bus bar 24 may be provided between the second main surface 14b of the piezoelectric layer 14 and the surface on the cavity side of the insulating layer 15. In this case, the third bus bar 24 and the plurality of third electrode fingers 27 may be electrically connected via the plurality of connection electrodes 28.

[0103] In this modification, when the third bus bar 24 is provided in the insulating layer 15 , similarly to the first embodiment, the filter device can be miniaturized and the resistance of the wiring connected to the reference potential can be reduced.

[0104] In the first embodiment and the present modification, the width of the connection electrode 28 is narrower than the width of the third electrode finger 27. However, the width of the connection electrode 28 may be greater than the width of the third electrode finger 27. The width of the connection electrode 28 refers to the dimension of the connection electrode 28 along the direction orthogonal to the electrode fingers.

[0105] A dielectric film may be provided on the first main surface 14a of the piezoelectric layer 14 so as to cover the plurality of electrode fingers. In this case, the plurality of electrode fingers are protected by the dielectric film, so that the plurality of electrode fingers are less likely to be damaged.

[0106] For example, the elastic wave device according to the present invention may also be a WLP (Wafer Level Package) structure. Alternatively, the elastic wave device according to the present invention may also have a structure in which an elastic wave resonator is mounted on a mounting substrate. In these cases, a third bus bar having a reference potential electrode may also be provided on a portion other than the piezoelectric substrate. These examples are shown in the second embodiment and the third embodiment.

[0107] Fig.11 FIG. 2 is a schematic front cross-sectional view of an elastic wave device according to a second embodiment. Fig.11 In FIG. 1 , a simplified diagram in which two diagonal lines are added to a rectangle shows a portion where each comb-shaped electrode and a plurality of third electrode fingers are provided. Fig.11 The same is true for the other schematic front and sectional views. Fig.11 The cross section of the portion where the third bus bar and the connection electrode are not provided in the reference potential electrode is shown.

[0108] The elastic wave device 30 of this embodiment has a WLP structure. Specifically, a first support 32 as a support in the present invention is provided on the piezoelectric substrate 12. More specifically, the first support 32 is provided on the first principal surface 14a of the piezoelectric layer 14. The first support 32 has a frame shape. Therefore, the first support 32 has an opening 32a.

[0109] The first main surface 14a of the piezoelectric layer 14 is provided with the first comb-shaped electrode, the second comb-shaped electrode, and a plurality of third electrode fingers in the functional electrode 31. When the portion of the piezoelectric layer 14 where the comb-shaped electrodes and the plurality of third electrode fingers are provided is set as the element electrode forming portion F, the element electrode forming portion F is located in the opening 32a.

[0110] A plurality of second supports 33 are provided on the first main surface 14a of the piezoelectric layer 14. The second supports 33 have a columnar shape. The plurality of second supports 33 are located in the opening 32a of the first support 32. In the present embodiment, the first support 32 and the second support 33 are respectively a stack of a plurality of metal layers. In addition, the second support 33 may not necessarily be provided.

[0111] The cover member 34 is provided on the first support 32 and the plurality of second supports 33 so as to close the opening 32a, thereby forming a hollow portion surrounded by the piezoelectric substrate 12, the first support 32, and the cover member 34. The element electrode forming portion F is located in the hollow portion.

[0112] The cover member 34 has a cover member body 34A and an inorganic oxide layer 34B. The cover member body 34A has a pair of main surfaces. The two main surfaces are opposite to each other. One main surface of the cover member body 34A is opposite to the piezoelectric substrate 12. The inorganic oxide layer 34B is provided on both main surfaces of the cover member body 34A. The main surface of the cover member 34 is a surface of the inorganic oxide layer 34B in a portion provided on the main surface of the cover member body 34A.

[0113] More specifically, the cover member 34 has a third main surface 34a and a fourth main surface 34b. The third main surface 34a and the fourth main surface 34b are opposite to each other. Of the third main surface 34a and the fourth main surface 34b, the third main surface 34a is the main surface on the piezoelectric substrate 12 side. However, the inorganic oxide layer 34B may not be provided. In this case, the third main surface 34a and the fourth main surface 34b of the cover member 34 are the main surfaces of the cover member body 34A.

[0114] In the present embodiment, the cover member body 34A is a silicon substrate. In addition, the support substrate 16 in the piezoelectric substrate 12 is also a silicon substrate. However, the materials of the support substrate 16 and the cover member body 34A are not limited to the above.

[0115] The cover member 34 is provided with a through electrode 35. More specifically, the cover member 34 is provided with a through hole. The through hole is provided so as to reach the second support body 33. The through electrode 35 is provided in the through hole. One end of the through electrode 35 is connected to the second support body 33. The external terminal 36 is provided to be connected to the other end of the through electrode 35. The external terminal 36 is configured as an electrode pad. In addition, in the present embodiment, the through electrode 35 and the external terminal 36 are provided as a whole. However, the through electrode 35 and the external terminal 36 may also be provided separately.

[0116] The inorganic oxide layer 34B of the cover member 34 is provided not only on the main surface of the cover member body 34A, but also in the through hole. More specifically, in the through hole, the inorganic oxide layer 34B is located between the through electrode 35 and the cover member body 34A. The inorganic oxide layer 34B is provided to cover the vicinity of the outer peripheral edge of the external terminal 36. The inorganic oxide layer 34B reaches between the external terminal 36 and the cover member body 34A. The inorganic oxide layer 34B is, for example, a silicon oxide layer. However, the material of the inorganic oxide layer 34B is not limited to the above.

[0117] In addition, the inorganic oxide layer 34B may not be provided in the through hole of the cover member main body 34A. The inorganic oxide layer 34B may not be provided on the external terminal 36 or between the external terminal 36 and the cover member main body 34A.

[0118] The portion of the plurality of external terminals 36 that is not covered by the inorganic oxide layer 34B is provided with a protrusion 37 as a conductive bonding member. For example, the protrusion 37 may be a solder protrusion or an Au protrusion. In addition, for example, the conductive bonding member may be a conductive adhesive. The conductive bonding member is electrically connected to an external reference potential or a signal potential.

[0119] Fig.12 This is a schematic front cross-sectional view showing an enlarged portion of the elastic wave device according to the second embodiment.

[0120] The third bus bar 24 of the reference potential electrode 39 in the present embodiment is provided on the third main surface 34 a of the cover member 34 . The third bus bar 24 faces the plurality of third electrode fingers 27 .

[0121] The plurality of connection electrodes 38 in the reference potential electrode 39 are arranged between the first main surface 14a of the piezoelectric layer 14 and the cover member 34. The connection electrode 38 is a columnar electrode. More specifically, each connection electrode 38 is arranged to extend over one third electrode finger 27 and over the piezoelectric layer 14. Moreover, each connection electrode 38 is connected to the third bus bar 24. That is, the plurality of connection electrodes 38 connect the third bus bar 24 and the plurality of third electrode fingers 27. As a result, the resistance of the reference potential electrode 39 is low.

[0122] In addition, each connection electrode 38 only needs to be provided on at least the third electrode finger 27. At least one connection electrode 38 may be provided only on the third electrode finger 27. In this case, the connection electrode 38 is not provided directly on the piezoelectric layer 14.

[0123] Fig.13 is a schematic plan view showing an electrode structure on the first main surface of the piezoelectric layer in the second embodiment.

[0124] In a plan view, the third bus bar 24 is provided in a portion overlapping with an area outside the electrode finger extending direction of the intersection region E. Specifically, in a plan view, the third bus bar 24 overlaps with an area between the first bus bar 22 and the plurality of second electrode fingers 26. Alternatively, in a plan view, the third bus bar 24 may overlap with an area between the second bus bar 23 and the plurality of first electrode fingers 25.

[0125] The third bus bar 24 is connected via other wiring, Fig.11 The through electrode 35 and the protrusion 37 shown are electrically connected to the reference potential. In addition, the layout freedom in the third main surface 34a of the cover member 34 is high. Therefore, on the third main surface 34a, it is possible to easily provide wiring for connecting the reference potential electrode 39 to the reference potential without increasing the size of the elastic wave device 30. In addition, the width of the third bus bar 24 can be easily widened. As a result, the resistance of the reference potential electrode 39 can be easily and effectively reduced.

[0126] In addition, similarly to the first embodiment, the elastic wave device 30 of this embodiment is an acoustic coupling filter. Therefore, when the elastic wave device 30 is used as an elastic wave resonator in a filter device, even if the elastic wave resonator constituting the filter device is one or a small number, a filter waveform can be obtained appropriately. Therefore, the miniaturization of the filter device can be promoted, and the resistance of the wiring connected to the reference potential can be reduced.

[0127] In addition, the first support body 32 may be provided on a layer other than the piezoelectric layer 14 in the piezoelectric substrate 12. More specifically, as in the first embodiment, the support member 13 is a laminate of the support substrate 16 and the insulating layer 15. For example, in a plan view, the outer periphery of the piezoelectric layer 14 may be located at an inner side than the outer periphery of the insulating layer 15 or the support substrate 16. In this case, the first support body 32 may be provided on the insulating layer 15 or the support substrate 16.

[0128] Fig.14 It is a schematic front cross-sectional view of an elastic wave device according to a third embodiment.

[0129] The elastic wave device 40 has a structure in which an elastic wave resonator is mounted on a mounting substrate 45. Specifically, the elastic wave device 40 is a CSP (Chip Size Package) structure. The mounting substrate 45 is a printed circuit board (PCB). In the present embodiment, the material of the mounting substrate 45 is a high temperature co-fired ceramic (HTCC). However, the material of the mounting substrate 45 is not limited to the above.

[0130] On the other hand, the support substrate 16 in the piezoelectric substrate 12 is a silicon substrate. However, the material of the support substrate 16 is not limited to the above.

[0131] A plurality of conductive bonding members are provided on the piezoelectric substrate 12. More specifically, a plurality of electrode pads 48 are provided on the piezoelectric substrate 12. A conductive bonding member is provided on each of the plurality of electrode pads 48. In the present embodiment, the conductive bonding member is a protrusion 47. For example, the protrusion 47 may be a solder protrusion or an Au protrusion.

[0132] The piezoelectric substrate 12 is bonded to the mounting substrate 45 through a plurality of conductive bonding members. The mounting substrate 45 has a fifth principal surface 45a and a sixth principal surface 45b. Of the fifth principal surface 45a and the sixth principal surface 45b, the fifth principal surface 45a is the principal surface on the side of the piezoelectric substrate 12. A sealing resin 44 is provided on the fifth principal surface 45a so as to cover the support substrate 16 in the piezoelectric substrate 12. A hollow portion is formed by the piezoelectric substrate 12, the sealing resin 44, and the mounting substrate 45. The element electrode forming portion F in the piezoelectric layer 14 is located in the hollow portion.

[0133] A plurality of external terminals 46 are provided on the sixth main surface 45b of the mounting substrate 45. A plurality of via electrodes and a plurality of wirings are provided in the mounting substrate 45. Each of the external terminals 46 is electrically connected to the via electrodes and wirings in the mounting substrate 45. Furthermore, each of the plurality of external terminals 46 is electrically connected to an external reference potential or signal potential via a bump or a conductive adhesive or the like.

[0134] Fig.15 This is a schematic front cross-sectional view showing an enlarged portion of the elastic wave device according to the third embodiment.

[0135] The third bus bar 24 of the reference potential electrode 39 in the present embodiment is provided on the fifth main surface 45a of the mounting substrate 45. The third bus bar 24 faces the plurality of third electrode fingers 27.

[0136] The plurality of connection electrodes 38 in the reference potential electrode 39 are arranged between the first principal surface 14a of the piezoelectric layer 14 and the fifth principal surface 45a of the mounting substrate 45. The connection electrodes 38 are columnar electrodes. More specifically, each connection electrode 38 is arranged only on one third electrode finger 27. Moreover, each connection electrode 38 is connected to the third bus bar 24. That is, the plurality of connection electrodes 38 connect the third bus bar 24 and the plurality of third electrode fingers 27. As a result, the resistance of the reference potential electrode 39 is low.

[0137] In addition, each connection electrode 38 only needs to be provided on at least the third electrode finger 27. At least one connection electrode 38 may be provided over the third electrode finger 27 and the piezoelectric layer 14.

[0138] and Fig.13 In the third embodiment shown in the figure, the third bus bar 24 is provided in a portion overlapping with the area outside the electrode finger extending direction of the intersection area E in a plan view. Specifically, in a plan view, the third bus bar 24 overlaps with the area between the first bus bar 22 and the plurality of second electrode fingers 26. Alternatively, in a plan view, the third bus bar 24 may overlap with the area between the second bus bar 23 and the plurality of first electrode fingers 25.

[0139] The third bus bar 24 passes through Fig.14 The wiring on the fifth main surface 45a of the mounting substrate 45 shown, the wiring in the mounting substrate 45, the via electrode, and the external terminal 46 are electrically connected to the reference potential. In addition, the layout in the fifth main surface 45a has a high degree of freedom. Therefore, on the fifth main surface 45a, it is possible to easily set the wiring for connecting the reference potential electrode 39 to the reference potential without increasing the size of the elastic wave device 40. In addition, the width of the third bus bar 24 can be easily widened. As a result, the resistance of the reference potential electrode 39 can be easily and effectively reduced.

[0140] In addition, similarly to the first embodiment, the elastic wave device 40 of this embodiment is an acoustic coupling filter. Therefore, when the elastic wave device 40 is used as an elastic wave resonator in a filter device, even if the elastic wave resonator constituting the filter device is one or a small number, a filter waveform can be obtained appropriately. Therefore, the miniaturization of the filter device can be promoted, and the resistance of the wiring connected to the reference potential can be reduced.

[0141] The following uses an example in which the functional electrode is an IDT electrode to illustrate the details of the thickness shear mode. In addition, the IDT electrode does not have a third electrode finger. The "electrode" in the IDT electrode described later is equivalent to the electrode finger. The supporting member in the following example is equivalent to the supporting substrate in the present invention. In the following, the reference potential is sometimes recorded as the ground potential.

[0142] Fig.16 (a) is a schematic perspective view showing the appearance of an elastic wave device using a thickness shear mode bulk wave, Fig.16 (b) is a top view showing the electrode structure on the piezoelectric layer. Fig.17 It is along Fig.16 (a) is a cross-sectional view of a portion taken along line AA.

[0143] The elastic wave device 1 has a piezoelectric layer 2 including LiNbO3. The piezoelectric layer 2 may also be a piezoelectric layer including LiTaO3. The cutting angle of LiNbO3 and LiTaO3 is Z-cut, but it may also be a rotated Y-cut or X-cut. The thickness of the piezoelectric layer 2 is not particularly limited, but in order to effectively excite the thickness shear mode, it is preferably greater than 40nm and less than 1000nm, and more preferably greater than 50nm and less than 1000nm. The piezoelectric layer 2 has a first principal surface 2a and a second principal surface 2b facing each other. An electrode 3 and an electrode 4 are provided on the first principal surface 2a. Here, electrode 3 is an example of a "first electrode", and electrode 4 is an example of a "second electrode". In Fig.16 (a) and Fig.16 In (b), a plurality of electrodes 3 are connected to a first bus bar 5. A plurality of electrodes 4 are connected to a second bus bar 6. The plurality of electrodes 3 and the plurality of electrodes 4 are interlaced with each other. The electrodes 3 and 4 have a rectangular shape and a length direction. In a direction orthogonal to the length direction, the electrode 3 is opposed to the 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, it can also be said that the electrode 3 is opposed to the adjacent electrode 4 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 opposed to each other in a direction intersecting with the thickness direction of the piezoelectric layer 2. Fig.16 (a) and Fig.16 The lengthwise directions of the electrodes 3 and 4 shown in (b) are reversed. Fig.16 (a) and Fig.16 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.16 (a) and Fig.16(b) becomes extending in the direction in which electrodes 3 and 4 extend. Moreover, a pair of structures in which an electrode 3 connected to one potential and an electrode 4 connected to another potential are adjacent are provided with multiple pairs in a direction orthogonal to the length direction of the electrodes 3 and 4. Here, the so-called electrode 3 and electrode 4 are adjacent refers to the situation in which the electrode 3 and the electrode 4 are arranged with a gap, rather than the situation in which the electrode 3 and the electrode 4 are arranged in direct contact. In addition, when the electrode 3 and the electrode 4 are adjacent, between the electrode 3 and the electrode 4, no electrode including other electrodes 3 and 4 connected to the signal electrode and the ground electrode is arranged. The number of pairs does not need to be an integer pair, and can also be 1.5 pairs, 2.5 pairs, etc. The center-to-center distance between the electrodes 3 and 4, that is, the spacing, is preferably in the range of 1 μm or more and 10 μm or less. In addition, the width of the electrodes 3 and 4, that is, the size of the opposing direction of the electrodes 3 and 4, is preferably in the range of 50 nm or more and 1000 nm or less, and more preferably in the range of 150 nm or more and 1000 nm or less. The center-to-center distance between electrodes 3 and 4 is the distance connecting the center of the dimension (width dimension) of electrode 3 in a direction perpendicular to the length direction of electrode 3 and the center of the dimension (width dimension) of electrode 4 in a direction perpendicular to the length direction of electrode 4.

[0144] In addition, in the elastic wave device 1, since a Z-cut piezoelectric layer is used, the direction orthogonal to the length direction of the electrodes 3 and 4 becomes a direction orthogonal to the polarization direction of the piezoelectric layer 2. In the case where a piezoelectric body with another cutting angle is used as the piezoelectric layer 2, this is not limited to this. Here, the so-called "orthogonal" is not limited to the case of only being strictly orthogonal, and can also be approximately orthogonal (the angle formed by the direction orthogonal to the length direction of the electrodes 3 and 4 and the polarization direction is, for example, within the range of 90°±10°).

[0145] A support member 8 is stacked on the second main surface 2b side of the piezoelectric layer 2 via an insulating layer 7. The insulating layer 7 and the support member 8 have a frame-like shape. Fig.17 As shown, there are through holes 7a and 8a. Accordingly, a cavity 9 is formed. The cavity 9 is provided so as not to hinder the vibration of the excitation region C of the piezoelectric layer 2. Therefore, the support member 8 is stacked on the second main surface 2b via the insulating layer 7 at a position that does not overlap with the portion where at least a pair of electrodes 3 and 4 are provided. In addition, the insulating layer 7 may not be provided. Therefore, the support member 8 may be directly or indirectly stacked on the second main surface 2b of the piezoelectric layer 2.

[0146] 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 plane orientation of the surface of Si on the side of the piezoelectric layer 2 can be (100), (110), or (111). The Si constituting the supporting member 8 is expected to have a high resistance with a resistivity of more than 4 kΩcm. However, the supporting member 8 can also be composed of suitable insulating materials or semiconductor materials.

[0147] 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.

[0148] The plurality of electrodes 3, 4 and the first bus bar 5 and the second bus bar 6 are made of a suitable metal or alloy such as Al or AlCu alloy. In the elastic wave device 1, the electrodes 3, 4 and the first bus bar 5 and the second bus bar 6 have a structure in which an Al film is stacked on a Ti film. Alternatively, a bonding layer other than a Ti film may be used.

[0149] 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. Accordingly, 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 among the plurality of pairs of electrodes 3 and 4 is set to p, d / p is set to be less than 0.5. Therefore, 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 further good resonance characteristic can be obtained.

[0150] In the elastic wave device 1, since it has the above structure, even if the number of pairs of electrodes 3 and 4 is reduced to achieve miniaturization, it is difficult to reduce 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.18 (a) and Fig.18 (b) is used to illustrate the difference between the Lamb wave used in the elastic wave device and the body wave of the thickness shear mode mentioned above.

[0151] Fig.18(a) is a schematic front cross-sectional view for explaining the Lamb wave propagating in the piezoelectric film of the elastic wave device described in the Japanese Patent Gazette No. 2012-257019. Here, the wave propagates in the piezoelectric film 201 as shown by the arrow. Here, in the piezoelectric film 201, the first main surface 201a and the second main surface 201b are opposite to each other, and the thickness direction connecting the first main surface 201a and the second main surface 201b is the Z direction. The X direction is the direction in which the electrode fingers of the IDT electrode are arranged. Fig.18 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, the piezoelectric film 201 vibrates as a whole, and 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.

[0152] In contrast, Fig.18 As shown in (b), in the elastic wave device 1, since the vibration displacement is in the thickness shear direction, the wave propagates almost in the direction connecting the first main surface 2a and the second main surface 2b of the piezoelectric layer 2, that is, the Z direction, and resonance occurs. That is, the X-direction component of the wave is significantly smaller than the Z-direction component. Moreover, since the resonance characteristic is obtained by the propagation of the wave in the Z direction, it is difficult to generate propagation loss even if the number of electrode fingers of the reflector is reduced. Moreover, even if the number of pairs of electrode pairs including electrodes 3 and 4 is reduced to promote miniaturization, it is difficult to reduce the Q value.

[0153] In addition, if Fig.19 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 in the second region 452 included in the excitation region C. Fig.19 , 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.

[0154] 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 more than one pair of electrodes 3 and 4 . In other words, at least one pair of electrodes is sufficient.

[0155] 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.

[0156] Fig. 20 It is shown Fig.17 The resonance characteristics of the elastic wave device are shown in FIG. 1. The design parameters of the elastic wave device 1 for obtaining the resonance characteristics are as follows.

[0157] Piezoelectric layer 2: LiNbO3 with Euler angles (0°, 0°, 90°), thickness = 400nm.

[0158] When observed in a direction orthogonal to the length direction of electrode 3 and electrode 4, the length of the overlapping area of ​​electrode 3 and electrode 4, i.e., the excitation area C, is 40 μm, the number of pairs of electrodes including electrodes 3 and 4 is 21 pairs, the center distance between electrodes is 3 μm, the width of electrodes 3 and 4 is 500 nm, and d / p is 0.133.

[0159] Insulating layer 7: a silicon oxide film with a thickness of 1 μm.

[0160] Supporting member 8: Si.

[0161] 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 .

[0162] In elastic wave device 1 , the inter-electrode distances of the electrode pairs including electrodes 3 and 4 are set equal in all pairs. That is, electrodes 3 and electrodes 4 are arranged at equal intervals.

[0163] As Fig. 20 As can be clearly seen, even without the reflector, a good resonance characteristic with a fractional bandwidth of 12.5% ​​was obtained.

[0164] 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.21 This is explained.

[0165] and get Fig. 20 The elastic wave devices having the same resonant characteristics as shown above are obtained by changing d / p. Fig.21 3 is a graph showing the relationship between d / p and the fractional bandwidth of a resonator as an elastic wave device.

[0166] As Fig.21It can be clearly seen 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 increased to more than 7%. 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.

[0167] Fig. 22 1 is a top view of an elastic wave device using a thickness shear mode bulk wave. In the elastic wave device 80, a pair of electrodes including an electrode 3 and an electrode 4 are provided on the first principal surface 2a of the piezoelectric layer 2. Fig. 22 K in is the crossing width. As described above, in the elastic wave device of the present invention, the number of pairs of electrodes may be 1 pair. In this case, if the above d / p is 0.5 or less, a thickness shear mode bulk wave can be effectively excited.

[0168] In the elastic wave device 1, it is preferred that, among the plurality of electrodes 3 and 4, the metallization ratio MR of any adjacent electrodes 3 and 4 with respect to the excitation region C 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.23 as well as Fig.24 This is explained. Fig.23 : is a reference diagram showing an example of the resonance characteristics of the elastic wave device 1. Spurious signals indicated by arrow B appear between the resonance frequency and the antiresonance frequency. In addition, d / p=0.08 is set, and the Euler angles of LiNbO3 are set to (0°, 0°, 90°). In addition, the metallization ratio MR is set to 0.35.

[0169] Reference Fig.16 (b) is used to illustrate the metallization ratio MR. Fig.16In the electrode structure of (b), when focusing on a pair of electrodes 3 and 4, it is assumed that only the pair of electrodes 3 and 4 are provided. In this case, the portion surrounded by the single-dot chain line becomes the excitation region C. The so-called excitation region C is the region where the electrode 3 overlaps with the electrode 4, the region where the electrode 4 overlaps with the electrode 3, and the region between the electrode 3 and the electrode 4 where the electrode 3 overlaps with the electrode 4 when the electrode 3 and the electrode 4 are observed in the direction perpendicular to the longitudinal direction of the electrodes 3 and 4, that is, in the opposite direction. And, the area of ​​the electrodes 3 and 4 in the excitation region C relative to the area of ​​the excitation region C is the metallization ratio MR. That is, the metallization ratio MR is the ratio of the area of ​​the metallized portion to the area of ​​the excitation region C.

[0170] When a plurality of pairs of electrodes are provided, the ratio of the total area of ​​the metallized portions included in all the excitation regions to the area of ​​the excitation regions may be defined as MR.

[0171] Fig.24 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 when a large number of spurious wave resonators are formed according to the structure of the spurious wave device 1. In addition, the film thickness of the piezoelectric layer and the size of the electrode were variously changed to adjust the fractional bandwidth. In addition, Fig.24 These are the results obtained when a piezoelectric layer including Z-cut LiNbO 3 is used; however, the same tendency is observed when a piezoelectric layer having other cut angles is used.

[0172] exist Fig.24 In the area surrounded by ellipse J, the spurious signal becomes larger and becomes 1.0. Fig.24 As can be clearly seen, if the fractional bandwidth exceeds 0.17, that is, if it exceeds 17%, even if the parameters constituting the fractional bandwidth are changed, large spurs with a spurious level of 1 or more appear in the passband. Fig.23 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.

[0173] Fig.25 : 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.25The 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 set the fractional bandwidth to less than 17%. More preferably, Fig.25 The region to the right of MR=3.5(d / 2p)+0.05 indicated by the dashed line D1 in FIG. 1 is shown in FIG. 1. That is, if MR≤1.75(d / p)+0.05, the fractional bandwidth can be reliably set to 17% or less.

[0174] Fig.26 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.26 The multiple regions R shown by the hatching in the figure are regions where a fractional bandwidth of 2% or more can be obtained. In addition, when φ in the Euler angles (φ, θ, ψ) is within the range of 0°±5°, the relationship between θ and ψ and the fractional bandwidth is the same as Fig.26 In the case where the piezoelectric layer includes lithium tantalate (LiTaO3), the relationship between θ and ψ in the Euler angle (in the range of 0°±5°, θ, ψ) and BW is also the same as Fig.26 The relationship shown is the same.

[0175] 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°, θ and φ are within the range of Fig.26 If the fractional bandwidth is within any range of the plurality of regions R shown, it is possible to sufficiently widen the fractional bandwidth, which is preferable.

[0176] Fig. 27 It is a front cross-sectional view of an elastic wave device having an acoustic multilayer membrane.

[0177] 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-mentioned d / p to 0.5 or less, the resonance characteristics of the bulk wave based on the thickness shear mode can be obtained. In addition, in the acoustic multilayer film 82, the number of stacked layers of the low acoustic impedance layers 82a, 82c, 82e and the high acoustic impedance layers 82b, 82d is not particularly limited. It is sufficient as long as at least one high acoustic impedance layer 82b, 82d is arranged on the side away from the piezoelectric layer 2 compared with the low acoustic impedance layers 82a, 82c, 82e.

[0178] The low acoustic impedance layers 82a, 82c, 82e and the high acoustic impedance layers 82b, 82d can be made of appropriate materials as long as the above-mentioned acoustic impedance relationship is satisfied. For example, silicon oxide or silicon oxynitride can be used as the material of the low acoustic impedance layers 82a, 82c, 82e. In addition, alumina, silicon nitride or metal can be used as the material of the high acoustic impedance layers 82b, 82d.

[0179] Fig.28 This is a partially cutaway perspective view for explaining an elastic wave device using Lamb waves.

[0180] The elastic wave device 91 has a support substrate 92. The support substrate 92 is provided with a recessed portion opened on the upper surface. 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.28 In the figure, the outer periphery of the cavity 9 is shown by a dotted line. Here, the IDT electrode 94 has a first bus bar 94a, a second bus bar 94b, a plurality of first electrode fingers 94c, and a plurality of second electrode fingers 94d. The plurality of first electrode fingers 94c are connected to the first bus bar 94a. The plurality of second electrode fingers 94d are connected to the second bus bar 94b. The plurality of first electrode fingers 94c and the plurality of second electrode fingers 94d are interlaced with each other.

[0181] In the elastic wave device 91, Lamb waves as plate waves are excited by applying an alternating electric field to the IDT electrode 94 on the cavity 9. Furthermore, since the reflectors 95 and 96 are provided on both sides, resonance characteristics based on the Lamb waves can be obtained.

[0182] Thus, the elastic wave device of the present invention may also be an elastic wave device using plate waves. Fig.28 In the example shown, the equivalent Figure 1 The main surface of the first main surface 14a of the piezoelectric layer 14 shown in the figure is provided with an IDT electrode 94, a reflector 95, and a reflector 96. On the other hand, in the elastic wave device of the present invention, a pair of comb-shaped electrodes and a plurality of third electrode fingers are provided on the first main surface 14a. In the case where the elastic wave device of the present invention is an elastic wave device using plate waves, it is sufficient that a pair of comb-shaped electrodes and a plurality of third electrode fingers and the above-mentioned reflectors 95 and 96 are provided on the first main surface 14a of the piezoelectric layer 14 in the first embodiment to the third embodiment and the modified example. In this case, it is sufficient that the reflectors 95 and 96 sandwich the pair of comb-shaped electrodes and a plurality of third electrode fingers in the direction orthogonal to the electrode fingers.

[0183] In the elastic wave devices of the first to third embodiments and the modified examples, for example, an acoustic reflection film may be provided between the support member and the piezoelectric layer. Fig. 27 The acoustic multilayer membrane 82 shown. Specifically, the supporting member and the piezoelectric layer may be arranged so that at least a portion of the supporting member and at least a portion of the piezoelectric layer are opposed to each other with the acoustic multilayer membrane 82 sandwiched therebetween. In this case, it is sufficient to alternately stack low acoustic impedance layers and high acoustic impedance layers in the acoustic multilayer membrane 82. The acoustic multilayer membrane 82 may also be an acoustic reflection portion in an elastic wave device.

[0184] In the elastic wave devices of the first to third embodiments and the modified examples using bulk waves in the thickness shear mode, as described above, d / p is preferably 0.5 or less, and more preferably 0.24 or less. This can provide better resonance characteristics.

[0185] Furthermore, in the excitation region of the elastic wave device in the first to third embodiments and the modified examples using the thickness shear mode body wave, as described above, MR ≤ 1.75 (d / p) + 0.075 is preferably satisfied. More specifically, when the metallization ratio of the first and third electrode fingers and the second and third electrode fingers with respect to the excitation region is MR, MR ≤ 1.75 (d / p) + 0.075 is preferably satisfied. In this case, spurious emission can be suppressed more reliably.

[0186] Description of Reference Numerals

[0187] 1…Elastic wave device

[0188] 2…Piezoelectric layer

[0189] 2a, 2b...1st main surface, 2nd main surface

[0190] 3, 4…Electrode

[0191] 5, 6…1st bus bar, 2nd bus bar

[0192] 7…Insulation layer

[0193] 7a…Through hole

[0194] 8…Supporting member

[0195] 8a…Through hole

[0196] 9…Hollow

[0197] 10…Elastic wave device

[0198] 10a…Cavity

[0199] 11…Functional electrode

[0200] 12…Piezoelectric substrate

[0201] 13…Supporting member

[0202] 14…Piezoelectric layer

[0203] 14a, 14b…1st main surface, 2nd main surface

[0204] 15…Insulation layer

[0205] 16…Support base plate

[0206] 17, 18…1st comb-shaped electrode, 2nd comb-shaped electrode

[0207] 19…Reference potential electrode

[0208] 22-24…1st bus bar to 3rd bus bar

[0209] 25 to 27…1st electrode finger to 3rd electrode finger

[0210] 28…Connect the electrodes

[0211] 30…Elastic wave device

[0212] 31…Functional electrode

[0213] 32…1st support

[0214] 32a…Opening

[0215] 33…Second support

[0216] 34… Cover member

[0217] 34A... Cover member body

[0218] 34B…Inorganic oxide layer

[0219] 34a, 34b…3rd main surface, 4th main surface

[0220] 35…Through electrode

[0221] 36…external terminal

[0222] 37… bulge

[0223] 38…Connect the electrodes

[0224] 39…Reference potential electrode

[0225] 40…Elastic wave device

[0226] 44…Sealing resin

[0227] 45…Mounting base plate

[0228] 45a, 45b…5th main surface, 6th main surface

[0229] 46…external terminal

[0230] 47…raised

[0231] 48…Electrode pad

[0232] 80, 81…Elastic wave device

[0233] 82…Acoustic multilayer film

[0234] 82a, 82c, 82e…low acoustic impedance layer

[0235] 82b, 82d…high acoustic impedance layer

[0236] 91…Elastic wave device

[0237] 92…Support base plate

[0238] 93…Piezoelectric layer

[0239] 94…IDT electrode

[0240] 94a, 94b…1st bus bar, 2nd bus bar

[0241] 94c, 94d ... first electrode finger, second electrode finger

[0242] 95, 96…Reflector

[0243] 109…reference potential electrode

[0244] 114…Bus 3

[0245] 115…Insulation film

[0246] 119…Reference potential electrode

[0247] 201…Piezoelectric film

[0248] 201a, 201b…1st main surface, 2nd main surface

[0249] 451, 452…1st area, 2nd area

[0250] C…Incentive Area

[0251] E…Intersection Area

[0252] F...Equipment electrode forming part

[0253] R…Region

[0254] VP1…imaginary plane.

Claims

1. An elastic wave device comprising: A piezoelectric substrate including a piezoelectric layer having a first main surface and a second main surface facing each other, and a supporting member stacked on the second main surface of the piezoelectric layer; a first comb-shaped electrode, provided on the first main surface of the piezoelectric layer, having a first bus bar and a plurality of first electrode fingers each having one end connected to the first bus bar, and connected to an input potential; a second comb-shaped electrode, disposed on the first main surface of the piezoelectric layer, having a second bus bar and a plurality of second electrode fingers each having one end connected to the second bus bar, and connected to an output potential, wherein the plurality of second electrode fingers are interlaced with the plurality of first electrode fingers; and a reference potential electrode having a plurality of third electrode fingers, a plurality of connecting electrodes and a third bus bar, and connected to a reference potential, wherein the plurality of third electrode fingers are respectively arranged on the first main surface of the piezoelectric layer so as to be arranged side by side with the first electrode finger and the second electrode finger in the direction in which the first electrode finger and the second electrode finger are arranged, the plurality of connecting electrodes are respectively connected to the plurality of third electrode fingers, and the third bus bar is electrically connected to the plurality of third electrode fingers through the plurality of connecting electrodes, The first electrode finger, the second electrode finger, and the third electrode finger are arranged in an order that forms one cycle when starting from the first electrode finger. The third bus bar is provided to face the third electrode fingers across at least the piezoelectric layer, and the connection electrodes penetrate at least the piezoelectric layer to connect the third bus bar and the third electrode fingers.

2. The elastic wave device according to claim 1, wherein: The third bus bar is provided on the second main surface of the piezoelectric layer.

3. The elastic wave device according to claim 2, wherein: The supporting member includes an insulating layer provided on the second main surface of the piezoelectric layer so as to cover the third bus bar.

4. An elastic wave device comprising: A piezoelectric substrate including a piezoelectric layer having a first main surface and a second main surface facing each other; a first comb-shaped electrode, provided on the first main surface of the piezoelectric layer, having a first bus bar and a plurality of first electrode fingers each having one end connected to the first bus bar, and connected to an input potential; A second comb-shaped electrode, disposed on the first main surface of the piezoelectric layer, having a second bus bar and a plurality of second electrode fingers each having one end connected to the second bus bar, and connected to an output potential, wherein the plurality of second electrode fingers are interlaced with the plurality of first electrode fingers; a reference potential electrode having a plurality of third electrode fingers, a plurality of connecting electrodes and a third bus bar, and connected to a reference potential, the plurality of third electrode fingers being respectively arranged on the first main surface of the piezoelectric layer so as to be arranged side by side 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 plurality of connecting electrodes being respectively connected to the plurality of third electrode fingers, and the third bus bar being electrically connected to the plurality of third electrode fingers via the plurality of connecting electrodes; A support body, disposed on the piezoelectric substrate; and a cover member provided on the support body, having a third main surface located on the piezoelectric substrate side and a fourth main surface facing the third main surface, The first electrode finger, the second electrode finger, and the third electrode finger are arranged in an order that forms one cycle when starting from the first electrode finger. The third bus bar is provided on the third main surface of the cover member so as to face the third electrode fingers, and the connection electrodes are provided at least on the third electrode fingers to connect the third bus bar and the third electrode fingers.

5. The elastic wave device according to claim 4, wherein: At least one of the connection electrodes is disposed over the third electrode finger and the piezoelectric layer.

6. The elastic wave device according to claim 4 or 5, wherein: The cover member includes a silicon substrate.

7. An elastic wave device comprising: A piezoelectric substrate including a piezoelectric layer having a first main surface and a second main surface facing each other; a first comb-shaped electrode, provided on the first main surface of the piezoelectric layer, having a first bus bar and a plurality of first electrode fingers each having one end connected to the first bus bar, and connected to an input potential; A second comb-shaped electrode, disposed on the first main surface of the piezoelectric layer, having a second bus bar and a plurality of second electrode fingers each having one end connected to the second bus bar, and connected to an output potential, wherein the plurality of second electrode fingers are interlaced with the plurality of first electrode fingers; a reference potential electrode having a plurality of third electrode fingers, a plurality of connecting electrodes and a third bus bar, and connected to a reference potential, the plurality of third electrode fingers being respectively arranged on the first main surface of the piezoelectric layer so as to be arranged side by side 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 plurality of connecting electrodes being respectively connected to the plurality of third electrode fingers, and the third bus bar being electrically connected to the plurality of third electrode fingers via the plurality of connecting electrodes; A plurality of conductive bonding members are disposed on the piezoelectric substrate; and a mounting substrate, which is bonded to the piezoelectric substrate via the plurality of conductive bonding members, and has a fifth main surface located on the piezoelectric substrate side and a sixth main surface facing the fifth main surface, The first electrode finger, the second electrode finger, and the third electrode finger are arranged in an order that forms one cycle when starting from the first electrode finger. The third bus bar is provided on the fifth main surface of the mounting substrate so as to face the plurality of third electrode fingers, and the plurality of connection electrodes are provided at least on the plurality of third electrode fingers to connect the third bus bar and the plurality of third electrode fingers.

8. The elastic wave device according to claim 7, wherein: A sealing resin is provided on the fifth main surface of the mounting substrate so as to cover the piezoelectric substrate and to form a hollow portion together with the piezoelectric substrate and the mounting substrate.

9. The elastic wave device according to claim 7 or 8, wherein: The plurality of conductive joining members are a plurality of protrusions.

10. The elastic wave device according to any one of claims 1 to 9, wherein: The piezoelectric substrate includes a supporting substrate stacked on the piezoelectric layer.

11. The elastic wave device according to any one of claims 1 to 10, wherein: The elastic wave device is configured to utilize plate waves.

12. The elastic wave device according to any one of claims 1 to 10, wherein: The elastic wave device is configured to utilize thickness shear mode bulk waves.

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

5.

14. The elastic wave device according to claim 13, wherein: d / p is less than 0.

24.

15. The elastic wave device according to claim 13 or 14, wherein: The sound reflecting portion is a cavity portion, and the supporting member and the piezoelectric layer are arranged so that a part of the supporting member and a part of the piezoelectric layer face each other with the cavity portion interposed therebetween.

16. The elastic wave device according to claim 13 or 14, wherein: The sound reflecting portion is a sound reflecting membrane including a high acoustic impedance layer having relatively high acoustic impedance and a low acoustic impedance layer having relatively low acoustic impedance, and the supporting member and the piezoelectric layer are configured so that at least a portion of the supporting member and at least a portion of the piezoelectric layer are opposite to each other with the sound reflecting layer sandwiched therebetween.

17. The elastic wave device according to any one of claims 13 to 16, wherein: When a direction orthogonal to the direction in which the first electrode finger, the second electrode finger, and the third electrode finger extend is set as the electrode finger orthogonal direction, an area where adjacent first electrode fingers and third electrode fingers overlap with each other in the electrode finger orthogonal direction, and an area where adjacent second electrode fingers and third electrode fingers overlap with each other in the electrode finger orthogonal direction are excitation areas. When the metallization ratio of the first electrode finger and the third electrode finger, and the second electrode finger and the third electrode finger with respect to the excitation region is MR, MR≦1.75(d / p)+0.075 is satisfied.

18. The elastic wave device according to any one of claims 1 to 17, wherein: The piezoelectric layer includes lithium tantalate or lithium niobate.

19. The elastic wave device according to claim 18, wherein: The Euler angles (φ, θ, ψ) of lithium niobate or lithium tantalate constituting the piezoelectric layer are within the range of the following formula (1), formula (2) or formula (3), (within the range of 0°±10°, 0°~25°, arbitrary ψ) …Formula (1) (0°±10°, 25°~100°, 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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