Elastic wave device and filter device

Abstract

Provided is an elastic wave device capable of suppressing useless waves and suppressing deterioration of resonance characteristics. This elastic wave device is provided with: a piezoelectric substrate that includes a piezoelectric layer; and an IDT electrode (8) that is provided on the piezoelectric layer. The IDT electrode (8) has first and second bus bars (14, 15) facing each other, a plurality of first electrode fingers (16) each having one end connected to the first bus bar (14), and a plurality of second electrode fingers (17) each having one end connected to the second bus bar (15). The plurality of first electrode fingers and the plurality of second electrode fingers (16, 17) are interleaved and inserted with each other. The portion where the first electrode fingers (16) and the second electrode fingers (17) overlap each other in the elastic wave propagation direction is an intersection region (D). The shape of the plurality of first and second electrode fingers (16, 17) in plan view includes a curved portion. In the intersection region (D), the resonance frequencies or the anti-resonance frequencies substantially coincide with each other.

Description

Technical Field

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

[0002] In the past, elastic wave devices have been widely used in filters of portable phones, etc. An example of an elastic wave device is disclosed in the following patent document 1. In this elastic wave device, an IDT (Interdigital Transducer) electrode is provided on a piezoelectric substrate. The shape of the multiple electrode fingers of the IDT electrode includes a curved shape. More specifically, each electrode finger extends along a curved line from the center of the area where the IDT electrodes intersect to the common electrode.

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2011 / 108229 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] In the IDT electrode of the elastic wave device described in Patent Document 1, the electrode finger pitch in the center portion in the direction in which the plurality of electrode fingers extend is narrower than the electrode finger pitch in the end portion in the direction. Therefore, the effect of suppressing the response of unnecessary waves can be obtained. However, since the resonant frequency varies for each portion of the IDT electrode, there is a possibility that the resonant characteristics may deteriorate.

[0008] An object of the present invention is to provide an elastic wave device and a filter device that can suppress unnecessary waves and can suppress degradation of resonance characteristics.

[0009] Technical solutions to solve problems

[0010] In a broad aspect of the elastic wave device involved in the present invention, it comprises: a piezoelectric substrate including a piezoelectric layer; and an IDT electrode arranged on the piezoelectric layer, the IDT electrode having a first bus bar and a second bus bar facing each other, a plurality of first electrode fingers connected to the first bus bar at one end, and a plurality of second electrode fingers connected to the second bus bar at one end, the plurality of first electrode fingers and the plurality of second electrode fingers are interlaced with each other, the portion where the first electrode fingers and the second electrode fingers overlap in the direction of elastic wave propagation is an intersection region, the shape of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view includes a curved portion, and in the intersection region, the resonant frequencies or anti-resonant frequencies are substantially consistent with each other.

[0011] In other broad aspects of the elastic wave device according to the present invention, there is provided: a piezoelectric substrate including a piezoelectric layer; and an IDT electrode arranged on the piezoelectric layer, wherein the IDT electrode has a first bus bar and a second bus bar facing each other, a plurality of first electrode fingers connected to the first bus bar at one end, and a plurality of second electrode fingers connected to the second bus bar at one end, wherein the plurality of first electrode fingers and the plurality of second electrode fingers are interlaced with each other, and the first electrode fingers and the second electrode fingers overlap with each other in the direction of propagation of the elastic wave. The portion is an intersection region, the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view include a circular arc or an elliptical arc, the center of a circle including the circular arc or the midpoint of two foci of an ellipse including the elliptical arc in the shape of the first electrode fingers and the second electrode fingers is set as a fixed point, a straight line passing through the intersection region in the center in the direction in which the plurality of first electrode fingers and the plurality of second electrode fingers extend is set as a reference line, and an angle formed by the straight line passing through the fixed point and the reference line is set as θ C When C The larger the absolute value of is, the narrower the electrode finger spacing is.

[0012] In another broad aspect of the elastic wave device involved in the present invention, it comprises: a piezoelectric substrate including a piezoelectric layer; and an IDT electrode arranged on the piezoelectric layer, the piezoelectric substrate being one of a substrate in which the piezoelectric layer made of lithium tantalate or lithium niobate and a supporting substrate are stacked, and a substrate including only the piezoelectric layer made of lithium niobate, the IDT electrode having a first bus bar and a second bus bar facing each other, a plurality of first electrode fingers connected to the first bus bar at one end, and a plurality of second electrode fingers connected to the second bus bar at one end, the plurality of first electrode fingers and the plurality of second electrode fingers being connected to each other. The first electrode finger and the second electrode finger are interlaced with each other, and the portion where the first electrode finger and the second electrode finger overlap each other in the direction of propagation of the elastic wave is an intersection region. The shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a top view include a circular arc or an elliptical arc. The center of the circle including the circular arc in the shape of the first electrode finger and the second electrode finger or the midpoint of the two foci of the elliptical arc is set as a fixed point, a straight line passing through the intersection region in the center in the direction in which the plurality of first electrode fingers and the plurality of second electrode fingers extend is set as a reference line, and an angle formed by the straight line passing through the fixed point and the reference line is set as θ. C When the plurality of first electrode fingers and the plurality of second electrode fingers have the angle θ C The larger the absolute value of θ is, the wider the electrode finger pitch is, and the angle θ C One of the structures in which the electrode finger pitch becomes narrower as the absolute value of becomes larger.

[0013] A filter device according to the present invention includes a plurality of elastic wave resonators, and at least one of the elastic wave resonators is an elastic wave device configured according to the present invention.

[0014] Effects of the Invention

[0015] According to the elastic wave device and the filter device according to the present invention, it is possible to suppress unnecessary waves and to suppress degradation of resonance characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0017] Figure 2 It is along Figure 1 Schematic cross-sectional view of line II in FIG.

[0018] Figure 3 It is a schematic plan view for explaining the structure of the IDT electrode in the first embodiment of the present invention.

[0019] Figure 4 This is a schematic plan view showing an enlarged portion of the IDT electrode in the first embodiment of the present invention.

[0020] Figure 5 is an absolute value of the angle |θ of the IDT electrode in the first embodiment of the present invention. C |A graph showing the relationship between 0 and duty cycle.

[0021] Figure 6 It is a schematic top view of an IDT electrode in a comparative example.

[0022] Figure 7 It is a diagram showing the Q value near the frequency of exciting the main mode in the first embodiment of the present invention and the first comparative example.

[0023] Figure 8 It is a graph showing the return loss around the frequency at which Rayleigh waves occur in the first embodiment of the present invention and the first comparative example.

[0024] Fig. 9 It is a diagram showing the inverse velocity surface of the elastic wave propagating through the first piezoelectric substrate and the second piezoelectric substrate.

[0025] Fig.10 It is a diagram showing the inverse velocity surfaces of the longitudinal wave, the fast transverse wave, and the slow transverse wave in the first piezoelectric substrate.

[0026] Fig.11 is an absolute value of the angle |θ of the IDT electrode in the first modification of the first embodiment of the present invention.C |A graph showing the relationship between 0 and duty cycle.

[0027] Fig.12 1 is a diagram showing impedance frequency characteristics when the resonance frequencies substantially match each other and the difference Δf between the resonance frequencies is a negative value, and when the difference Δf between the resonance frequencies is zero.

[0028] Fig.13 1 is a diagram showing impedance frequency characteristics when the resonance frequencies substantially match each other and the difference Δf between the resonance frequencies is a positive value, and when the difference Δf between the resonance frequencies is zero.

[0029] Fig.14 is an absolute value of the angle |θ of the IDT electrode in the second modification of the first embodiment of the present invention. C |A graph showing the relationship between 0 and duty cycle.

[0030] Fig.15 It is a diagram showing the return loss near the frequency at which a higher-order mode occurs in the second modification example of the first embodiment of the present invention and the first comparative example.

[0031] Fig.16 It is a graph showing the relationship between the length of the offset electrode and the impedance ratio.

[0032] Fig.17 It is a graph showing the relationship between the gap width and the impedance ratio.

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

[0034] Fig.19 It is a schematic front cross-sectional view of an elastic wave device according to a fourth modified example of the first embodiment of the present invention.

[0035] Fig. 20 It is a schematic plan view of an elastic wave device according to a second embodiment of the present invention.

[0036] Fig.21 It is a schematic plan view for explaining the structure of an IDT electrode in the second embodiment of the present invention.

[0037] Fig. 22 is an absolute value of the angle |θ of the IDT electrode in the second embodiment of the present invention. C |A diagram showing the relationship between θ and the electrode finger pitch.

[0038] Fig.23 It is a diagram showing the return loss near the frequency at which a higher-order mode occurs in the second embodiment of the present invention and the first comparative example.

[0039] Fig.24 It is a schematic plan view of an elastic wave device according to a third embodiment of the present invention.

[0040] Fig.25 It is a schematic plan view of an elastic wave device according to a fourth embodiment of the present invention.

[0041] Fig.26 It is a diagram showing the impedance frequency characteristics in the first embodiment and the fourth embodiment of the present invention.

[0042] Fig. 27 It is a diagram showing the impedance frequency characteristics near the upper end of the stop band in the first embodiment and the fourth embodiment of the present invention.

[0043] Fig.28 It is a diagram showing the return loss in the first embodiment and the fourth embodiment of the present invention.

[0044] Fig.29 It is a schematic plan view of an elastic wave device according to a fifth embodiment of the present invention.

[0045] Fig.30 It is a diagram showing the impedance frequency characteristics in the first embodiment and the fifth embodiment of the present invention.

[0046] Fig.31 It is a diagram showing the phase characteristics around 2.2 times the resonance frequency in the first embodiment and the fifth embodiment of the present invention.

[0047] Fig.32 It is a diagram showing the return loss in the first embodiment and the fifth embodiment of the present invention.

[0048] Fig.33 is an absolute value of the angle of the IDT electrode in the sixth embodiment of the present invention |θ C |A diagram showing the relationship between the thickness of the electrode fingers.

[0049] Fig.34 It is a schematic front cross-sectional view of an elastic wave device according to a seventh embodiment of the present invention.

[0050] Fig.35 is an absolute value of the angle |θ| of the portion of the IDT electrode covered by the dielectric film in the seventh embodiment of the present invention. C |A graph showing the relationship between and the thickness of the dielectric film.

[0051] Fig.36 is an absolute value of the angle |θ| of the portion of the IDT electrode covered by the dielectric film in the modification of the seventh embodiment of the present invention. C |A graph showing the relationship between and the thickness of the dielectric film.

[0052] Fig.37 It is a schematic plan view of an elastic wave device according to an eighth embodiment of the present invention.

[0053] Fig.38 1 is a schematic plan view showing the vicinity of a first edge region and the vicinity of a second edge region of an elastic wave device according to a ninth embodiment of the present invention.

[0054] Fig.39 1 is a schematic plan view showing the vicinity of a first edge region and the vicinity of a second edge region of an elastic wave device according to a tenth embodiment of the present invention.

[0055] Fig.40 This is a circuit diagram of a filter device according to an eleventh embodiment of the present invention.

[0056] Fig.41 This is a schematic plan view showing an enlarged portion of an IDT electrode in a fifth modification of the first embodiment of the present invention.

[0057] Fig.42 It is a schematic front cross-sectional view of an elastic wave device according to a twelfth embodiment of the present invention.

[0058] Fig.43 It is a schematic front cross-sectional view of an elastic wave device according to a thirteenth embodiment of the present invention.

[0059] Fig.44 It is a schematic front cross-sectional view of an elastic wave device according to a first modified example of the thirteenth embodiment of the present invention.

[0060] Fig.45 It is a schematic front cross-sectional view of an elastic wave device according to a second modified example of the thirteenth embodiment of the present invention.

[0061] Fig.46 It is a schematic front cross-sectional view of an elastic wave device according to a third modified example of the thirteenth embodiment of the present invention. DETAILED DESCRIPTION

[0062] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings to make the present invention clear.

[0063] 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.

[0064] Figure 1 It is a schematic plan view of the elastic wave device according to the first embodiment of the present invention. Figure 2 It is along Figure 1Schematic cross-sectional view of line II in FIG.

[0065] like Figure 1 as well as Figure 2 As shown in FIG. 1 , the elastic wave device 1 includes a piezoelectric substrate 2. The piezoelectric substrate 2 is a substrate having piezoelectricity. Figure 2 As shown, the piezoelectric substrate 2 has a supporting member 3 and a piezoelectric layer 6. More specifically, the supporting member 3 has a supporting substrate 4 and a dielectric layer 5. The dielectric layer 5 includes a first layer 5a and a second layer 5b. The first layer 5a is provided on the supporting substrate 4. The second layer 5b is provided on the first layer 5a. The piezoelectric layer 6 is provided on the second layer 5b. In addition, the layer structure of the piezoelectric substrate 2 is not limited to the above. For example, the piezoelectric substrate 2 may also be a substrate including only the piezoelectric layer 6.

[0066] like Figure 1 As shown in FIG. 1 , an IDT electrode 8 is provided on the piezoelectric layer 6. The IDT electrode 8 includes a plurality of first electrode fingers 16 and a plurality of second electrode fingers 17. In the present embodiment, the plurality of first electrode fingers 16 and the plurality of second electrode fingers 17 are in the shape of arcs when viewed from above. In this specification, the term “viewed from above” refers to a view from a direction equivalent to the direction of the electrode. Figure 2 Observe from the top of the middle. Figure 2 For example, the piezoelectric layer 6 side is the upper side of the support substrate 4 side and the piezoelectric layer 6 side. In addition, the shapes of the plurality of first electrode fingers 16 and the plurality of second electrode fingers 17 in a plan view only need to include a curved portion. However, it is preferred that the shapes of the plurality of first electrode fingers 16 and the plurality of second electrode fingers 17 in a plan view include a circular arc or an elliptical arc, as in the present embodiment. The following describes the details of the structure of the IDT electrode 8.

[0067] Return to Figure 1 In addition to a plurality of first electrode fingers 16 and a plurality of second electrode fingers 17, the IDT electrode 8 also has a first bus bar 14 and a second bus bar 15, and a plurality of first offset electrodes 18 and a plurality of second offset electrodes 19. The first bus bar 14 and the second bus bar 15 are opposite to each other. One end of the plurality of first electrode fingers 16 is respectively connected to the first bus bar 14. One end of the plurality of second electrode fingers 17 is respectively connected to the second bus bar 15. The plurality of first electrode fingers 16 and the plurality of second electrode fingers 17 are interlaced with each other. Moreover, the area where the first electrode fingers 16 and the second electrode fingers 17 overlap with each other in the propagation direction of the elastic wave is an intersection area. In the following, the first electrode fingers 16 and the second electrode fingers 17 are sometimes simply recorded as electrode fingers.

[0068] In other words, the intersection region is the region between the first envelope, which is an imaginary line connecting the top ends of the plurality of second electrode fingers 17, and the second envelope, which is an imaginary line connecting the top ends of the plurality of first electrode fingers 16. More specifically, the region surrounded by the electrode fingers at one end in the direction in which the plurality of electrode fingers are arranged, the electrode fingers at the other end, the first envelope, and the second envelope is the intersection region. Therefore, the first envelope corresponds to the edge portion of the first bus bar 14 side of the intersection region. The second envelope corresponds to the edge portion of the second bus bar 15 side of the intersection region.

[0069] One end of each of the plurality of first offset electrodes 18 is connected to the first bus bar 14. The first electrode fingers 16 and the first offset electrodes 18 are arranged alternately. One end of each of the plurality of second offset electrodes 19 is connected to the second bus bar 15. The second electrode fingers 17 and the second offset electrodes 19 are arranged alternately.

[0070] The plurality of first electrode fingers 16 and the plurality of second electrode fingers 17, and the plurality of first offset electrodes 18 and the plurality of second offset electrodes 19 include base ends and top ends, respectively. The base ends of the first electrode fingers 16 and the first offset electrodes 18 are portions connected to the first bus bar 14. The base ends of the second electrode fingers 17 and the second offset electrodes 19 are portions connected to the second bus bar 15. The top ends of the first electrode fingers 16 and the top ends of the second offset electrodes 19 are opposed to each other with a gap G2 therebetween. Furthermore, the top ends of the first electrode fingers 16 are opposed to the second bus bar 15 with the gap G2 and the second offset electrodes 19 therebetween. On the other hand, the top ends of the second electrode fingers 17 and the top ends of the first offset electrodes 18 are opposed to each other with a gap G1 therebetween. Furthermore, the top ends of the second electrode fingers 17 are opposed to the first bus bar 14 with the gap G1 and the first offset electrodes 18 therebetween.

[0071] Hereinafter, the first offset electrode 18 and the second offset electrode 19 may be simply described as offset electrodes. The first bus bar 14 and the second bus bar 15 may be simply described as bus bars.

[0072] Figure 3 It is a schematic plan view for explaining the structure of the IDT electrode in the first embodiment.

[0073] The shapes of the plurality of electrode fingers in a top view are respectively equivalent to the shapes of the arcs in the plurality of concentric circles. Therefore, the centers of the circles including the arcs in the shapes of the plurality of electrode fingers are consistent. The center is set as a fixed point C. In the present embodiment, the end edge portion on the side of the first bus bar 14 of the intersection region D is adjacent to the plurality of gaps G1. The end edge portion on the side of the second bus bar 15 of the intersection region D is adjacent to the plurality of gaps G2.

[0074] When the ellipticity coefficient of the circle or ellipse of the arc in the shape including the plurality of electrode fingers is set to α2 / α1, the ellipticity coefficient α2 / α1 in the present embodiment is 1. In addition, when the shape of the arc in the shape including the plurality of electrode fingers is an ellipse, the ellipticity coefficient α2 / α1 is other than 1. α1 corresponds to the dimension of the ellipse along the direction of the axis passing through the intersection region D among the major axis and the minor axis. α2 corresponds to the dimension of the ellipse along the direction of the axis not passing through the intersection region D among the major axis and the minor axis.

[0075] A straight line passing through the center of the intersection region D in the direction in which the plurality of first electrode fingers 16 and the plurality of second electrode fingers 17 extend is set as a reference line N. The direction in which the plurality of first electrode fingers 16 and the plurality of second electrode fingers 17 extend here refers to a direction extending along a curve. Or, for example, the reference line N is a straight line passing through the center of the intersection region D in the direction connecting the end edge portions on the first bus bar 14 side and the end edge portions on the second bus bar 15 side in the intersection region D, where the distance between the end edge portions becomes the shortest. In the present embodiment, the reference line N is a straight line corresponding to the axis of symmetry of the end edge portions on the first bus bar 14 side and the second bus bar 15 side of the intersection region D. The above-mentioned fixed point C passes through the reference line N and is located outside the intersection region D.

[0076] The angle between the straight line passing through the fixed point C and the reference line N is set to θ C Although there are countless straight lines passing through the fixed point C, Figure 3 In this specification, the angle θ is C The positive direction is the counterclockwise direction in a plan view. More specifically, the direction from the second bus bar 15 side toward the first bus bar 14 side is the positive direction.

[0077] By applying an AC voltage to the IDT electrode 8, elastic waves are excited in the intersection region D. The intersection region D has portions located on countless straight lines passing through the fixed point C. Figure 3In the figure, straight line M is shown as an example of the countless straight lines passing through the fixed point C and the intersection area D. For example, in the portion of the intersection area D located on the straight line M, an elastic wave is excited. Elastic waves are also excited in the portions of the intersection area D located on the countless other straight lines not shown. That is, each straight line passing through the fixed point C and the intersection area D extends parallel to the direction of the excited elastic wave (a direction perpendicular to the direction in which the electrode fingers of the IDT electrode 8 extend) when the ellipticity coefficient α2 / α1 is 1, and is inclined from the direction of the excited elastic wave when the ellipticity coefficient α2 / α1 is not 1. In addition, the direction in which the electrode fingers extend mentioned here is the direction in which each part of the electrode fingers extends. The above-mentioned elastic wave propagation direction is parallel to the direction perpendicular to the tangent of the curved electrode finger. The angle θ formed by the straight line passing through the fixed point C and the intersection area D and the reference line N is C is the excitation angle θ C_prop In the part where the reference line N passes through, the excitation angle θ C_prop is 0°.

[0078] In addition, a piezoelectric single crystal is used as the material of the piezoelectric layer 6 of the elastic wave device 1. In the piezoelectric layer 6, the propagation axis is the direction of X propagation. In this embodiment, the propagation axis and the reference line N extend in parallel. Therefore, in the elastic wave device 1, the angle θ C It is the angle formed by the straight line passing through the fixed point C and the propagation axis. In addition, the propagation axis may be not only the X propagation direction but also the 90° X propagation direction or any one of the directions perpendicular to the extension direction of the electrode fingers of the IDT electrode 8. The direction in which the electrode fingers extend here refers to the direction in which the tangents of each part of the electrode fingers extend.

[0079] The angle θ formed by the straight line passing through the edge of the first bus bar 14 side of the intersection region D and the fixed point C and the reference line N is C Let the intersection angle θ C_AP1 The angle θ formed by the straight line passing through the edge of the second bus bar 15 side of the intersection region D and the fixed point C and the reference line N is C Let the intersection angle θ C_AP2 In this case, θ C_AP2 ≤θ C ≤θ C_AP1 In this embodiment, the intersection angle θ C_AP1 and the intersection angle θ C_AP2 The absolute value of is the same. Therefore, the angle θ C The absolute value of is 0°≤|θ C |≤|θ C_AP1 |=|θ C_AP2 |.

[0080] In the IDT electrode 8, the edge portion of the intersection region D on the first bus bar 14 side, the imaginary line connecting the plurality of gaps G1, and the first bus bar 14 extend in parallel. Similarly, the edge portion of the intersection region D on the second bus bar 15 side, the imaginary line connecting the plurality of gaps G2, and the second bus bar 15 extend in parallel.

[0081] A pair of reflectors 9A and 9B are provided on the piezoelectric layer 6. The reflectors 9A and 9B are opposed to each other with the IDT electrode 8 sandwiched therebetween in the direction in which the propagation axis extends. The reflector 9A has a plurality of electrode fingers 9a. The reflector 9B has a plurality of electrode fingers 9b. The shapes of the plurality of electrode fingers 9a of the reflector 9A and the shapes of the plurality of electrode fingers 9b of the reflector 9B in a top view are respectively equivalent to the shapes of the arcs in the plurality of concentric circles. The center of the circle including the arcs in the shapes of the plurality of electrode fingers 9a and the plurality of electrode fingers 9b coincides with the fixed point C.

[0082] Figure 4 FIG. 1 is a schematic plan view showing a portion of the IDT electrode in the first embodiment in an enlarged manner. Figure 4 In FIG. 1 , the IDT electrode 8 is shown by hatching.

[0083] In the IDT electrode 8, the duty ratio is determined by the angle θ C More specifically, the angle θ C The larger the absolute value of , the smaller the duty cycle. C In the cross region D, the resonant frequencies are roughly consistent with each other. In addition, the anti-resonant frequencies in the cross region D may also be roughly consistent with each other. In this specification, the so-called roughly consistent frequency and the other frequency means that the absolute value of the difference between the two frequencies is less than 2% relative to the reference frequency. That is, when the ratio of the difference between the two frequencies to the reference frequency is set as the frequency change rate, the so-called roughly consistent frequency means that the absolute value of the frequency change rate is less than 2%. In addition, the so-called reference frequency is the angle θ C The frequency at 0°.

[0084] In IDT electrode 8 of elastic wave device 1 , the electrode finger pitch is fixed. Therefore, when the wavelength defined by the electrode finger pitch is λ, the wavelength λ in IDT electrode 8 does not depend on the angle θ. C The electrode finger pitch is the distance between the centers of adjacent electrode fingers.

[0085] The present embodiment is characterized in that any angle θ in the intersection region D C In the embodiment, the resonance frequencies are substantially the same. This can suppress unnecessary waves and suppress degradation of resonance characteristics. The details are shown below together with the details of the structure of this embodiment.

[0086] Figure 5 is an absolute value of the angle |θ of the IDT electrode in the first embodiment. C |A graph showing the relationship between 0 and duty cycle.

[0087] like Figure 5 As shown, in the first embodiment, the angle θ in the IDT electrode 8 is C In the 0° portion, the duty ratio is 0.5. C More specifically, in this embodiment, when the absolute value of the angle |θ C | is set to x, and the duty cycle is set to y, y=1.057×10 -4 × 3 -2.753×10 -3 × 2 -4.803×10 -4 The relationship of ×x+0.5 holds. Therefore, any angle θ in the intersection area D C The resonant frequencies are roughly consistent with each other.

[0088] Here, the angle θ C The frequency and angle θ of the part with the largest absolute value C The frequency difference of the part with a value of 0° is Δf, and the angle θ C The frequency of the 0° portion is f C0 , set the frequency change rate to Δf / f C0 × 100. In addition, the absolute value of the frequency change rate is |Δf| / f C0 × 100. In the first embodiment, regarding the resonance frequency, |Δf| / f C0 ×100≤2%. More specifically, when the angle θ C The absolute value of θ is the largest. C =θ C_AP1 Or θ C =θ C_AP2 The frequency of the part is set to f C_AP When Δf=f C_AP -f C0 In the first embodiment, |f C_AP -f C0 | / f C0 ×100≤2%.

[0089] In addition, the absolute value of the angle |θ C The relationship between | and duty cycle is set to Figure 5 The design parameters of the elastic wave device 1 having the relationship shown are as follows.

[0090] Support substrate 4: Material: Si, plane orientation: (111), ψ of the Euler angles (φ, θ, ψ): 73°

[0091] First layer 5a: material…SiN, thickness…50nm

[0092] Second layer 5b: Material…SiO2, Thickness…300nm

[0093] Piezoelectric layer 6: Material: LiTaO3 with rotation Y-cut 55° X-propagation, thickness: 400nm

[0094] IDT electrode 8: Material…Al, Thickness…100 nm

[0095] Number of electrode fingers: 60 pairs

[0096] Ellipticity coefficient of electrode finger shape α2 / α1: 1

[0097] Crossing angle: θ C_AP1 ...10°, θ C_AP2 …-10°

[0098] Wavelength λ: 2μm

[0099] Reflector 9A and reflector 9B: Number of pairs of electrode fingers: 20 pairs

[0100] In the first embodiment, the transverse mode and Rayleigh waves, which are unnecessary waves, can be suppressed. This is shown by comparing the first embodiment with the first comparative example. In this comparison, the design parameters of the elastic wave device 1 according to the first embodiment are as described above.

[0101] In the first comparative example, Figure 6 As shown, each electrode finger of the IDT electrode 108, the reflector 109A, and the reflector 109B is linear. In the IDT electrode 108, the intersection region is rectangular. When the direction in which the plurality of electrode fingers extend is set as the electrode finger extension direction, and the dimension of the intersection region along the electrode finger extension direction is set as the intersection width, the intersection width is 41.5λ. The number of pairs of electrode fingers of the IDT electrode 108 is 60 pairs, and the number of pairs of electrode fingers of the reflector 109A and the reflector 109B are 20 pairs respectively. In the IDT electrode 108, the duty ratio is 0.5.

[0102] Figure 7 It is a diagram showing the Q value near the frequency of exciting the main mode in the first embodiment and the first comparative example. Figure 8 It is a graph showing the return loss around the frequency at which Rayleigh waves occur in the first embodiment and the first comparative example.

[0103] like Figure 7As shown in FIG. 1 , in the first comparative example, a large ripple is generated in the frequency characteristic of the Q value. This ripple is caused by the transverse mode. In contrast, in the first embodiment, it can be seen that the ripple caused by the transverse mode is suppressed. Figure 8 As shown, in the first embodiment, it can be seen that the Rayleigh wave, which is an unnecessary wave, is significantly suppressed compared to the first comparative example. As described above, in the first embodiment, the unnecessary wave can be suppressed.

[0104] In the first embodiment, the lengths of the plurality of electrode fingers are different from each other. Therefore, it is difficult for the phases of the transverse modes generated in the respective parts of the IDT electrode 8 to be consistent, and as a whole, it is difficult for the intensity of the transverse mode to be increased. Therefore, the transverse mode can be suppressed. Furthermore, in the first embodiment, the curvatures of the shapes of the electrode fingers in a plan view are different from each other. Therefore, the frequencies of the generated Rayleigh waves are dispersed. Therefore, the Rayleigh waves can be suppressed.

[0105] For example, the IDT electrode 8 only needs to include at least two first electrode fingers 16 or second electrode fingers 17 having different curvatures. In other words, the total number of electrode fingers having different curvatures only needs to be two or more. In this case, Rayleigh waves can be suppressed more reliably.

[0106] On the other hand, in the first embodiment, as described above, the resonant frequencies in each part are substantially consistent with each other. Therefore, since the main mode is properly excited, it is possible to suppress the degradation of the resonance characteristics. In addition, the curvature of the plurality of first electrode fingers 16 and the second electrode fingers 17 may gradually change from one side toward the other side in the direction in which the plurality of first electrode fingers 16 and the plurality of second electrode fingers 17 are arranged.

[0107] The present invention utilizes the propagation characteristics of elastic waves at various angles θ C The following describes the different situations.

[0108] The phase velocity of the elastic wave has a C The dependence of the phase velocity on the substrate shows its inherent characteristics according to the structure of the substrate. In addition, the inverse of the phase velocity is equivalent to the inverse velocity surface. Therefore, the angle θ C The relationship between and phase velocity is roughly the same as the inverse velocity surface of the piezoelectric substrate. Fig. 9 , an example of a reverse velocity surface of piezoelectric substrates having different layer structures is shown. One piezoelectric substrate is a substrate including only LiTaO3 (LT) rotated Y-cut 42°X propagation. This substrate is set as the first piezoelectric substrate. Another piezoelectric substrate is a laminated substrate of a piezoelectric layer / support substrate. This substrate is set as the second piezoelectric substrate. More specifically, the second piezoelectric substrate is a substrate in which a silicon substrate with a plane orientation of (100), a silicon oxide film, and a lithium tantalate layer are stacked in sequence.

[0109] Fig. 9 It is a diagram showing the inverse velocity surface of the elastic wave propagating through the first piezoelectric substrate and the second piezoelectric substrate.

[0110] The reciprocal velocity surfaces of the first piezoelectric substrate and the second piezoelectric substrate are both linearly symmetrical with the x-axis as the symmetry axis. In addition, the direction of the x-axis corresponds to the angle θ C The reciprocal velocity surface in the first piezoelectric substrate is concave. On the other hand, the reciprocal velocity surface in the second piezoelectric substrate is convex. Thus, the angle θ of the elastic wave propagating in the substrate is C The dependence of is different depending on the structure of the substrate. Also, when the elastic wave mode is different, the same substrate has a different dependence on the angle θ. C The dependencies are different. Fig.10 This is shown.

[0111] Fig.10 It is a diagram showing the inverse velocity surfaces of the longitudinal wave, the fast transverse wave, and the slow transverse wave in the first piezoelectric substrate.

[0112] like Fig.10 As shown, the inverse velocity surfaces of the longitudinal wave, the fast shear wave, and the slow shear wave, which are three elastic wave modes, are different from each other. Fig.10 The portions passing through arrows L1 and L2 correspond to angles θ C The example of the case where the angle is other than 0°. The interval between the reversal velocity surfaces of the slow shear wave and the fast shear wave in the portion passing through the arrow L1 is different from the interval between the reversal velocity surfaces of the slow shear wave and the fast shear wave in the portion passing through the arrow L2. Similarly, the interval between the reversal velocity surfaces of the fast shear wave and the longitudinal wave in the portion passing through the arrow L1 is different from the interval between the reversal velocity surfaces of the fast shear wave and the longitudinal wave in the portion passing through the arrow L2. That is, at the angle θ C When they are different from each other, the intervals between the inverse velocity surfaces of the different modes are different from each other. This is also the same in the relationship between the main mode and the unnecessary wave used in the elastic wave device.

[0113] In the first embodiment, at each angle θ C The resonant frequency of the main mode is roughly the same. Therefore, at each angle θ C In this way, the frequencies of the unnecessary waves become different from each other. Therefore, since the unnecessary waves are dispersed, the unnecessary waves can be suppressed.

[0114] The following describes in more detail the case where the resonant frequencies of the main modes are made substantially consistent. As mentioned above, the phase velocity is equivalent to the inverse of the inverse velocity surface. Therefore, the angle θ C The relationship between the phase velocity and Fig.10The inverse velocity surface in the XY plane of the piezoelectric substrate shown in FIG. 1 is substantially equal. That is, the function representing the curved shape of the electrode finger can be said to be determined by the shape of the inverse velocity surface in the XY plane of the piezoelectric substrate. The phase velocity of the elastic wave has a C dependency.

[0115] However, if the electrode fingers are simply shaped into a curve, the impedance frequency characteristic becomes C The impedance frequency characteristic overlaps the characteristics of the resonance frequencies that are greatly different from each other. Therefore, the impedance frequency characteristic is greatly deteriorated. Therefore, as in the first embodiment, by making the duty ratio that affects the frequency according to the angle θ C and change, so that each angle θ C The frequencies of the elastic waves excited in the are roughly the same. Therefore, it is possible to make C In the case of C Therefore, the impedance frequency characteristic is obtained in which the resonant frequency or the anti-resonant frequency is substantially consistent with each other.

[0116] In addition to the duty ratio, parameters that affect the frequency, such as the electrode finger pitch, the thickness of the electrode finger, the thickness of the piezoelectric layer, and the thickness of the intermediate layer in the piezoelectric substrate, can also be adjusted according to the angle θ. C The intermediate layer is, for example, a dielectric layer. When a dielectric film is provided on the piezoelectric substrate so as to cover the IDT electrode, the thickness of the dielectric film may be varied according to the angle θ. C In these cases, it is also possible to make the C However, when a dielectric film is provided on the piezoelectric substrate so as to cover the IDT electrode, it is also possible to adjust parameters other than the thickness of the dielectric film according to the angle θ. C In this case, the thickness of the dielectric film may be fixed.

[0117] In the elastic wave device described in Patent Document 1, the reverse velocity surface is concave. In this case, even if the electrode finger spacing in the central portion in the direction in which the plurality of electrode fingers extend is made narrower than the electrode finger spacing in the end portion in the direction in order to achieve a response that suppresses unnecessary waves, the resonance characteristics will deteriorate because the resonance frequency is different for each portion of the IDT electrode. In contrast, in the first embodiment, the reverse velocity surface is convex. Therefore, the angle θ C The larger the absolute value of becomes, the smaller the duty cycle becomes, thereby making it possible to make the resonant frequencies in the intersection area roughly consistent.

[0118] As mentioned above, each angle θ in the intersection regionC In this modification, the antiresonance frequencies can be made substantially consistent with each other. This example is shown as a first modification of the first embodiment. C Since the relationship with the duty ratio is different from that in the first embodiment, the symbols used in the description of the first embodiment are used in the description of this modification.

[0119] Fig.11 is an absolute value of the angle |θ of the IDT electrode in the first modification of the first embodiment. C |A graph showing the relationship between 0 and duty cycle.

[0120] like Fig.11 As shown, in this modification, the angle θ in the IDT electrode 8 is C In the 0° portion, the duty ratio is 0.5. C More specifically, in this embodiment, when the absolute value of the angle |θ C | is set to x, and the duty cycle is set to y, y=1.585×10 -4 × 3 -4.201×10 -3 × 2 +3.478×10 -4 The relationship of ×x+0.5 holds. Therefore, any angle θ in the intersection area D C In this modification, unnecessary waves can be suppressed, and degradation of resonance characteristics can be suppressed.

[0121] In addition, regarding the resonant frequency or the anti-resonant frequency, it is preferable that the absolute value of the frequency change rate |Δf| / f C0 ×100 is 1% or less. This can more reliably suppress the degradation of the resonance characteristics. Regarding the resonance frequency or the anti-resonance frequency, it is more preferable that the frequency change rate Δf / f C0 ×100 is greater than or equal to -0.66% and less than or equal to 0.82%. This can further reliably suppress the degradation of the resonance characteristics. The following shows that the resonance frequency is -0.66%≤Δf / f C0 In the case of ×100≤0.82%, this is an example in which degradation of the resonance characteristics is suppressed.

[0122] Fig.12 1 is a diagram showing impedance frequency characteristics when the resonance frequencies substantially match each other and the difference Δf between the resonance frequencies is a negative value, and when the difference Δf between the resonance frequencies is zero. Fig.13 1 is a diagram showing impedance frequency characteristics when the resonance frequencies substantially match each other and the difference Δf between the resonance frequencies is a positive value, and when the difference Δf between the resonance frequencies is zero.

[0123] like Fig.12 As shown, it can be seen that in Δf / f C0 ×100=-0.35%, and Δf / f C0 ×100=-0.66%, relative to Δf / f C0 ×100=0%, the characteristics near the resonant frequency do not deteriorate significantly. Fig.13 As shown, it can be seen that in Δf / f C0 ×100=0.39%, and Δf / f C0 ×100=0.82%, relative to Δf / f C0 ×100=0%, the characteristics near the resonance frequency do not deteriorate significantly.

[0124] In the first embodiment, the maximum value of the duty ratio is 0.5. However, the maximum value of the duty ratio is not limited to the above. In the second variation of the first embodiment, the maximum value of the duty ratio is 0.65. In this variation, the angle θ C The relationship between the duty cycle and Fig.14 The relationship shown here shows that any angle θ in the intersection region D C More specifically, in this modification, when the absolute value of the angle |θ C | is set to x, and the duty cycle is set to y, y=8.124×10 -5 × 3 -1.449×10 -3 × 2 -2.101×10 -2 The relationship of ×x+0.6397 holds true.

[0125] In the second variant, as in the first embodiment, it is possible to suppress unnecessary waves and suppress degradation of resonance characteristics. In addition, in the second variant, in addition to the transverse mode and Rayleigh wave, higher-order modes can also be suppressed. The details of this effect are shown below. Figure 6 The first comparative example is shown.

[0126] Fig.15 It is a diagram showing the return loss near the frequency at which a higher-order mode occurs in the second modification example of the first embodiment and the first comparative example.

[0127] like Fig.15As shown, it can be seen that in the second variant, the higher-order mode is suppressed compared to the first comparative example. More specifically, in the second variant, the higher-order mode near the frequency twice the frequency of the exciting main mode can be suppressed. In addition, depending on the reverse velocity surface of the piezoelectric substrate, the relationship between the duty ratio and the frequency of each mode is different. Therefore, depending on the structure of the piezoelectric substrate and the structure on the piezoelectric substrate, the absolute value of the angle |θ C |The larger the duty cycle, the greater the duty cycle. C In the part, sometimes the resonant frequencies or anti-resonant frequencies are roughly consistent with each other. In this case, the straight line passing through the part with the smallest duty cycle and the fixed point C is the reference line N. As an example, an elastic wave device in which an IDT electrode provided on a substrate including only LiNbO3 that propagates by rotating Y cut -4°X is embedded in a thick SiO2 film can be cited. Alternatively, at the angle θ passing through the reference line N C In the excitation portion at 0°, the duty ratio is not necessarily the maximum or minimum.

[0128] Next, the dimension of the offset electrode along the direction connecting the base end portion and the tip end portion is defined as the length of the offset electrode. In the first embodiment, the impedance ratio is calculated each time the length of the offset electrode is changed. In addition, the length of the offset electrode is changed every 0.5λ within a range of 1λ or more and 5λ or less. The results are shown below.

[0129] Fig.16 It is a graph showing the relationship between the length of the offset electrode and the impedance ratio.

[0130] like Fig.16 As shown in FIG. 1 , it can be seen that when the length of the offset electrode is greater than or equal to 1.5λ and less than or equal to 5λ, the impedance ratio becomes greater than or equal to 71 dB. Fig.16 The auxiliary line E in FIG. 1 is a line connecting the plotted points when the length of the offset electrode is 1λ and the plotted points when the length of the offset electrode is 1.5λ. As shown by the auxiliary line E, it can be seen that when the length of the offset electrode is 1.3λ or more, the impedance ratio can be made 71dB or more. The length of the offset electrode is preferably 1.3λ or more, and more preferably 1.5λ or more. Accordingly, the impedance ratio can be increased, and the Q characteristics of the main mode can be improved. On the other hand, the length of the offset electrode is preferably 5λ or less. Accordingly, the impedance ratio can be increased, and the Q characteristics of the main mode can be improved.

[0131] This is based on the following reasons. Figure 3 As shown in FIG. 1 , the angle θ formed by the straight line passing through the edge of the first bus bar 14 side of the intersection region D and the fixed point C and the reference line N is C is the intersection angle θ C_AP1. The straight line passing through the edge and the fixed point C extends in parallel with the imaginary line connecting the plurality of gaps G1. Therefore, the direction in which the imaginary line connecting the plurality of gaps G1 extends intersects with the direction in which the reference line N extends. Moreover, the direction in which the propagation axis of the piezoelectric layer 6 extends is the direction of X propagation and is parallel to the direction in which the reference line N extends. Therefore, the elastic waves excited in the intersection region D tend to leak from the plurality of gaps G1.

[0132] On the other hand, when the length of the first offset electrode 18 is sufficiently long to be equal to or greater than 1.3λ, the leaked elastic wave is reflected by a sufficient number of pairs of the first offset electrode 18 and the first electrode finger 16. Thus, the elastic wave can be effectively confined in the intersection region D. Similarly, the elastic wave leaked from the plurality of gaps G2 can be reflected toward the intersection region D by a sufficient number of pairs of the second offset electrode 19 and the second electrode finger 17. Therefore, in the elastic wave device 1, the Q characteristic of the main mode can be improved.

[0133] like Figure 1 As shown in FIG. 1 and FIG. 2 , the plurality of first offset electrodes 18 in the first embodiment are arc-shaped. In the portion of the IDT electrode 8 where the plurality of first offset electrodes 18 are provided, the closer to the first bus bar 14, the smaller the duty ratio becomes. Similarly, the plurality of second offset electrodes 19 are arc-shaped. In the portion of the IDT electrode 8 where the plurality of second offset electrodes 19 are provided, the closer to the second bus bar 15, the smaller the duty ratio becomes. In addition, the plurality of first offset electrodes 18 and the plurality of second offset electrodes 19 may be linear. In the portion where the plurality of first offset electrodes 18 and the plurality of second offset electrodes 19 are provided, the duty ratio may be fixed.

[0134] Here, the dimension of the gap along the direction in which the top end of the electrode finger and the bus bar are opposite to each other is referred to as the gap width. In the first embodiment, the gap width is synonymous with the dimension of the gap along the direction in which the top end of the electrode finger and the top end of the offset electrode are opposite to each other. Each time the gap width is changed, the impedance ratio is calculated. The results are shown below.

[0135] Fig.17 It is a graph showing the relationship between the gap width and the impedance ratio.

[0136] like Fig.17 As shown in FIG. 1 , it can be seen that when the gap width is 0.56λ or less, the impedance ratio becomes about 70 dB. Therefore, the gap width is preferably 0.56λ or less. This can increase the impedance ratio and improve the Q characteristic.

[0137] like Figure 2As shown, in the first embodiment, the piezoelectric substrate 2 is a stacked substrate of a supporting substrate 4, a first layer 5a and a second layer 5b of a dielectric layer 5, and a piezoelectric layer 6. More specifically, the first layer 5a in the first embodiment is a high-acoustic-velocity film. The high-acoustic-velocity film is a layer with a relatively high-acoustic-velocity. More specifically, the sound velocity of the body wave propagating in the high-acoustic-velocity film is higher than the sound velocity of the elastic wave propagating in the piezoelectric layer 6. On the other hand, the second layer 5b is a low-acoustic-velocity film. The low-acoustic-velocity film is a film with a relatively low-acoustic-velocity. More specifically, the sound velocity of the body wave propagating in the low-acoustic-velocity film is lower than the sound velocity of the body wave propagating in the piezoelectric layer 6.

[0138] In the first embodiment, a high-acoustic-velocity film, a low-acoustic-velocity film, and a piezoelectric layer 6 are sequentially stacked on the piezoelectric substrate 2. This can effectively confine the energy of the elastic wave to the piezoelectric layer 6. Figure 7 as well as Figure 8 The design parameters of the elastic wave device 1 shown in the comparison show examples of materials for the layers of the piezoelectric substrate 2 and the IDT electrode 8 in the elastic wave device 1. However, the materials are not limited to the above materials. The combination of materials for the layers of the piezoelectric substrate 2 and the IDT electrode 8 can be any combination of materials that is appropriate for exciting elastic waves.

[0139] As materials for the high acoustic velocity membrane, for example, piezoelectrics such as aluminum nitride, lithium tantalate, lithium niobate, and quartz, ceramics such as silicon carbide, silicon nitride, sapphire, alumina, zirconium oxide, cordierite, mullite, steatite, forsterite, magnesium oxide, spinel, and sialon, dielectrics such as aluminum oxide, silicon oxynitride, DLC (diamond-like carbon) films, diamond, or semiconductors such as silicon, polycrystalline silicon, and amorphous silicon, or materials with the above materials as the main components can be used.

[0140] As the material of the low acoustic velocity film, for example, a material mainly composed of glass, silicon oxide, silicon oxynitride, lithium oxide, tantalum pentoxide, or a compound in which fluorine, carbon, or boron is added to silicon oxide can be used.

[0141] As a material for the piezoelectric layer 6 , for example, lithium tantalate, lithium niobate, zinc oxide, aluminum nitride, quartz, or PZT (lead zirconate titanate) can be used. As a material for the piezoelectric layer 6 , lithium tantalate or lithium niobate is preferably used.

[0142] As the material of the support substrate 4, for example, piezoelectrics such as aluminum nitride, lithium tantalate, lithium niobate, quartz, alumina, sapphire, magnesium oxide, silicon nitride, silicon carbide, zirconium oxide, cordierite, mullite, steatite, forsterite, spinel, ceramics such as sialon, dielectrics such as aluminum oxide, silicon oxynitride, DLC (diamond-like carbon), diamond, or semiconductors such as silicon, or materials containing the above materials as the main component can also be used. In addition, the above-mentioned spinel listed as an example of the material of the support substrate 4 and the high acoustic velocity film includes aluminum compounds containing one or more elements selected from Mg, Fe, Zn, Mn, etc. and oxygen. As examples of the above-mentioned spinel, MgAl2O4, FeAl2O4, ZnAl2O4, and MnAl2O4 can be listed. As the material of the support substrate 4, silicon is preferably used.

[0143] In this specification, the main component refers to a component that accounts for more than 50% by weight. The material of the main component may be in any state of single crystal, polycrystalline, or amorphous, or in a state of a mixture of these.

[0144] In addition, the relationship between the acoustic velocities in the first layer 5a and the second layer 5b in the dielectric layer 5 is not limited to the above. Furthermore, the layer structure of the piezoelectric substrate 2 is not limited to the above. The third and fourth variants of the first embodiment are shown below, in which only the structure of the piezoelectric substrate 2 is different from that of the first embodiment. In the third and fourth variants, as in the first embodiment, useless waves can be suppressed and degradation of resonance characteristics can be suppressed. Furthermore, the energy of elastic waves can be effectively confined on the piezoelectric layer 6 side.

[0145] exist Fig.18 In the third variation shown, the piezoelectric substrate 2A includes a support substrate 4, an acoustic reflection film 7, a dielectric layer 5A, and a piezoelectric layer 6. The acoustic reflection film 7 is provided on the support substrate 4. The dielectric layer 5A is provided on the acoustic reflection film 7. The piezoelectric layer 6 is provided on the dielectric layer 5A. The dielectric layer 5A is a low acoustic velocity film.

[0146] The acoustic reflection film 7 is a laminate of multiple acoustic impedance layers. Specifically, the acoustic reflection film 7 has multiple low acoustic impedance layers and multiple high acoustic impedance layers. The high acoustic impedance layer is a layer with relatively high acoustic impedance. More specifically, the multiple high acoustic impedance layers of the acoustic reflection film 7 are the high acoustic impedance layer 13a, the high acoustic impedance layer 13b, and the high acoustic impedance layer 13c. On the other hand, the low acoustic impedance layer is a layer with relatively low acoustic impedance. More specifically, the multiple low acoustic impedance layers of the acoustic reflection film 7 are the low acoustic impedance layer 12a and the low acoustic impedance layer 12b. The low acoustic impedance layers and the high acoustic impedance layers are alternately laminated. In addition, the high acoustic impedance layer 13a is the layer located closest to the piezoelectric layer 6 in the acoustic reflection film 7.

[0147] The acoustic reflective film 7 has two low acoustic impedance layers and three high acoustic impedance layers. However, the acoustic reflective film 7 only needs to have at least one low acoustic impedance layer and at least one high acoustic impedance layer.

[0148] As the material of the low acoustic impedance layer, for example, silicon oxide or aluminum can be used. As the material of the high acoustic impedance layer, for example, metals such as platinum or tungsten, and dielectrics such as aluminum nitride or silicon nitride can be used. In addition, the material of the dielectric layer 5A can also be the same as the material of the low acoustic impedance layer.

[0149] exist Fig.19 In the fourth variant shown, the piezoelectric substrate 2B has a supporting substrate 4B and a piezoelectric layer 6. The piezoelectric layer 6 is directly provided on the supporting substrate 4B. More specifically, the supporting substrate 4B has a recess 4c. The piezoelectric layer 6 is provided on the supporting substrate 4B so as to block the recess 4c. Thus, a hollow portion is provided in the piezoelectric substrate 2B. In a plan view, the hollow portion overlaps with at least a portion of the IDT electrode 8.

[0150] Examples other than the first embodiment of the present invention are described below. In each of the following examples, the shape of the reflector is different from that of the first embodiment because the shape of the IDT electrode is different from that of the first embodiment.

[0151] Fig. 20 It is a schematic plan view of an elastic wave device according to a second embodiment.

[0152] The present embodiment differs from the first embodiment in that the shape of the plurality of electrode fingers in a plan view is an elliptical arc shape. The present embodiment also differs from the first embodiment in that the duty cycle is fixed and the electrode finger pitch is not fixed in the IDT electrode 28. Except for the above aspects, the elastic wave device of the present embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0153] The shapes of the plurality of electrode fingers in a plan view are shapes of respective elliptical arcs in a plurality of ellipses corresponding to the positions of the same center of gravity. Fig.21 The midpoint of the focal point A and the focal point B shown is the centroid. When the centroid is set to a fixed point C, the area where the straight line passing through the fixed point C intersects with each of the adjacent electrode fingers is the intersection area D. Regarding the ellipticity coefficient α2 / α1 in this embodiment, α2 / α1<1. More specifically, α2 / α1=0.72. However, the ellipticity coefficient α2 / α1 is not limited to the above.

[0154] Fig. 22 is an absolute value of the angle |θ of the IDT electrode in the second embodiment. C |A diagram showing the relationship between θ and the electrode finger pitch.

[0155] like Fig. 22As shown, in this embodiment, the angle θ in the IDT electrode 28 is C In the portion where the angle is 0°, the electrode finger pitch is 1 μm. C More specifically, in this embodiment, when the absolute value of the angle |θ C | is set to x, and the electrode finger pitch is set to y, y=-1×10 -4 × 2 -4×10 -5 ×x+1 holds true. Therefore, any angle θ in the intersection area D C The resonant frequencies are roughly consistent with each other.

[0156] In this embodiment, as in the first embodiment, it is possible to suppress unnecessary waves and suppress degradation of resonance characteristics. In addition, in this embodiment, in addition to the transverse mode and Rayleigh wave, higher-order modes can also be suppressed. The details of this effect are shown below. In addition, the present embodiment is compared with Figure 6 The first comparative example is shown.

[0157] Fig.23 It is a diagram showing the return loss near the frequency at which a higher-order mode occurs in the second embodiment and the first comparative example.

[0158] like Fig.23 As shown, it can be seen that in the second embodiment, the higher-order mode is suppressed compared to the first comparative example. More specifically, in the second embodiment, the higher-order mode near the frequency twice the frequency of the exciting main mode can be suppressed. This is based on the fact that since the electrode finger spacing is not fixed, the frequency of the mode other than the main mode is dispersed. However, in this embodiment, since the resonant frequency is roughly the same as described above, the frequency of the main mode is almost fixed, and the degradation of the resonance characteristics is suppressed.

[0159] In the second embodiment, similarly to the first embodiment, the reverse speed surface is convex. Fig. 9 In the elastic wave device in which the IDT electrode is formed on the first piezoelectric substrate in the comparison, the reverse velocity surface is concave. In addition, the first piezoelectric substrate is a substrate including only LiTaO3 rotated Y-cut 42°X propagation. In this case, similarly to the second embodiment, the duty ratio is fixed and the angle θ is changed to C When the frequencies are roughly the same, the angle θ C The larger the absolute value of , the narrower the electrode finger pitch becomes. Therefore, when the reverse velocity surface is concave, if the shape of the electrode finger is set to the angle θ C The greater the absolute value of , the wider the shape of the curve of the electrode finger pitch. However, it is not possible to make the electrode finger pitch at each angle θC The intermediate frequency is consistent, and the resonance characteristics are deteriorated. In contrast, the duty cycle is fixed and the angle θ C As the absolute value of becomes larger, the electrode finger pitch becomes narrower, thereby making it possible to make the frequencies roughly uniform, thereby improving the characteristics.

[0160] In the case of an elastic wave device in which an IDT electrode provided on a substrate including only a rotating Y-cut -4°X-propagating LiNbO3 is embedded in a thick SiO2 film, the reverse velocity surface becomes a convex shape. In addition, the thickness of the SiO2 film is, for example, 0.01λ to 1λ. At this time, the duty ratio is fixed and the angle θ is C As the absolute value of becomes larger, the electrode finger pitch becomes wider, thereby making it possible to make the frequencies roughly consistent, and thus the characteristics become better.

[0161] Alternatively, in the case of an elastic wave device in which an IDT electrode provided on a substrate including only LiNbO3 that rotates Y-cut 128.5°X propagation is embedded in a thick SiO2 film, the reverse velocity surface becomes a convex shape. In addition, the thickness of the SiO2 film is, for example, 0.01λ to 1λ. At this time, the duty ratio is fixed and the angle θ is set to C As the absolute value of becomes larger, the electrode finger pitch becomes narrower, thereby making it possible to make the frequencies roughly uniform, thereby improving the characteristics.

[0162] As described above, when the reciprocating surface in the piezoelectric substrate is convex, the plurality of first electrode fingers 16 and the plurality of second electrode fingers 17 have the following structure, thereby suppressing unnecessary waves and suppressing degradation of resonance characteristics. That is, the plurality of first electrode fingers 16 and the plurality of second electrode fingers 17 only need to have an angle θ C The larger the absolute value of is, the wider the electrode finger pitch is, and the angle θ is C The larger the absolute value of is, the narrower the electrode finger pitch is. In addition, the case where the reverse velocity surface in the piezoelectric substrate is convex, as described above, is a case where the piezoelectric substrate is a substrate including only a piezoelectric layer made of lithium niobate.

[0163] Or, if Figure 2 As shown, in the case where the piezoelectric substrate 2 is a substrate formed by stacking a piezoelectric layer 6 and a support substrate 4, the reverse velocity surface of the piezoelectric substrate 2 is convex. In addition, whether the piezoelectric layer 6 and the support substrate 4 are directly stacked or indirectly stacked via a dielectric layer 5, the reverse velocity surface of the piezoelectric substrate 2 can be convex. In this case, as the material of the piezoelectric layer 6, for example, lithium tantalate or lithium niobate can be used.

[0164] Fig.24 It is a schematic plan view of an elastic wave device according to a third embodiment.

[0165] The present embodiment is different from the first embodiment in that the plurality of electrode fingers of the IDT electrode 38 include linear portions. Except for the above point, the elastic wave device of the present embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0166] The intersection region of the IDT electrode 38 includes a first region W1, a second region W2, and a third region W3. The first region W1, the second region W2, and the third region W3 are arranged in a direction in which the first bus bar 14 and the second bus bar 15 are opposed to each other. More specifically, the first region W1 and the second region W2 are opposed to each other with the third region W3 sandwiched therebetween. The first region W1 is located on the first bus bar 14 side. The second region W2 is located on the second bus bar 15 side. The third region W3 includes an angle θ C The part at 0°.

[0167] In the first region W1 and the second region W2, the shapes of the plurality of electrode fingers when viewed from above are elliptical arcs. On the other hand, in the third region W3, the shapes of the plurality of electrode fingers when viewed from above are straight lines. Thus, each electrode finger includes a portion having a different curvature when viewed from above.

[0168] In the present embodiment, in the entire third region W3, the direction in which the propagation axis of the piezoelectric layer 6 extends (the direction of X propagation) is orthogonal to the direction in which the plurality of electrode fingers extend. Therefore, the third region W3 is a region that is stable with respect to the propagation axis. By having the third region W3 in the intersection region, degradation of the fractional bandwidth can be suppressed.

[0169] In this embodiment, as in the first embodiment, any angle θ in the intersection region D C In the embodiment, the resonance frequencies are substantially consistent with each other. In addition, the lengths of the plurality of electrode fingers are different from each other. Furthermore, the curvatures of the arc-shaped portions of the plurality of electrode fingers when viewed from above are different from each other. Thus, it is possible to suppress useless waves and to suppress degradation of the resonance characteristics.

[0170] In this embodiment, each electrode finger includes a portion in the shape of a straight line. However, even when each electrode finger does not include a straight line, each electrode finger may include a portion with a different curvature in the shape when viewed from above. In this case, it is preferred that the curvature of the electrode finger increases with the angle θ. C The absolute value of α increases and changes gradually. As a result, the electrical characteristics of the elastic wave device are unlikely to deteriorate.

[0171] Fig.25 It is a schematic plan view of an elastic wave device according to a fourth embodiment.

[0172] The present embodiment differs from the first embodiment in that the electrode finger pitch in the IDT electrode 48 is not constant and the ellipticity coefficient α2 / α1 is greater than 1. Except for the above, the elastic wave device of the present embodiment has the same structure as the elastic wave device 1 of the first embodiment. In the present embodiment, both the duty ratio and the electrode finger pitch are not constant.

[0173] More specifically, in this embodiment, the angle θ C The larger the absolute value of , the wider the electrode finger spacing. On the other hand, the angle θ C The larger the absolute value of , the smaller the duty cycle. C In this embodiment, as in the first embodiment, unnecessary waves can be suppressed and degradation of resonance characteristics can be suppressed.

[0174] Furthermore, in the present embodiment, the value of the fractional bandwidth can be increased, the value of the fractional stopband width can be increased, and the response at the upper end of the stopband can be suppressed. In addition, when the resonant frequency is set to fr and the anti-resonant frequency is set to fa, the fractional bandwidth is represented by |fr-fa| / fr. The so-called stopband is a region where the wavelength of the elastic wave becomes fixed by enclosing the elastic wave in a metal grating of a periodic structure. The so-called fractional stopband width is the value obtained by dividing the bandwidth of the stopband by the resonant frequency fr. In this specification, the end of the high-frequency side of the stopband is recorded as the upper end. The bandwidth of the stopband is the difference between the frequency of the upper end of the stopband and the resonant frequency fr.

[0175] As details of the above effects, the impedance frequency characteristics and the return loss are shown. The design parameters of the elastic wave device of this embodiment are as follows. In addition, as a reference, the results of the first embodiment are also shown. The design parameters of the elastic wave device 1 of the first embodiment are the same as those of the above embodiment. Figure 5 The relationships shown are when the design parameters are the same.

[0176] Number of pairs of IDT electrode fingers: 60 pairs

[0177] Ellipticity coefficient of electrode finger shape α2 / α1: 1.1

[0178] Length of offset electrode: 3.5λ

[0179] Crossing angle: θ c_AP1 ...10°, θ c_AP2 …-10°

[0180] Number of electrode fingers of reflector: 20 pairs

[0181] Fig.26It is a diagram showing the impedance frequency characteristics in the first embodiment and the fourth embodiment. Fig. 27 It is a diagram showing the impedance frequency characteristics near the upper end of the stop band in the first embodiment and the fourth embodiment. Fig.28 It is a diagram showing the return loss in the first embodiment and the fourth embodiment.

[0182] like Fig.26 As shown in FIG. 1 , in the fourth embodiment, the difference between the resonant frequency and the antiresonant frequency increases. Therefore, it can be seen that the value of the fractional bandwidth increases. Fig. 27 The arrow F1 in FIG. 1 shows the response at the upper end of the stopband in the first embodiment. The arrow F4 shows the response at the upper end of the stopband in the fourth embodiment. Fig. 27 As shown in FIG. 1 , in the fourth embodiment, the frequency of the response at the upper end of the stop band becomes higher than that in the first embodiment. Fig.26 As shown in FIG. 1 , the resonance frequencies are almost the same in the first embodiment and the fourth embodiment. Therefore, in the fourth embodiment, the value of the fractional stopband width is also larger than that in the first embodiment.

[0183] In addition, if Fig.28 As shown, it can be seen that in the fourth embodiment, the response at the upper end of the stop band can be suppressed. In the fourth embodiment, the ellipticity coefficient α2 / α1 of the shape of the plurality of electrode fingers is greater than 1. Accordingly, the frequency at the upper end of the stop band is dispersed. Therefore, the response at the upper end of the stop band can be suppressed.

[0184] Fig.29 It is a schematic plan view of an elastic wave device according to a fifth embodiment.

[0185] The present embodiment differs from the first embodiment in that the electrode finger pitch in the IDT electrode 58 is not constant and the ellipticity coefficient α2 / α1 is less than 1. Except for the above, the elastic wave device of the present embodiment has the same structure as the elastic wave device 1 of the first embodiment. In the present embodiment, both the duty ratio and the electrode finger pitch are not constant.

[0186] More specifically, in this embodiment, the angle θ C The larger the absolute value of , the narrower the electrode finger pitch. On the other hand, the angle θ C The larger the absolute value of , the larger the duty cycle. C In this embodiment, as in the first embodiment, unnecessary waves can be suppressed and degradation of resonance characteristics can be suppressed.

[0187] Furthermore, in this embodiment, the fractional bandwidth can be reduced, the high-order mode can be effectively suppressed, and the response at the upper end of the stopband can be suppressed. As details of the above effects, the impedance frequency characteristics and the return loss are shown. The design parameters of the elastic wave device of this embodiment are as follows. In addition, as a reference, the results of the first embodiment are also shown. The design parameters of the elastic wave device 1 of the first embodiment are the same as those of the above embodiment. Figure 5 The relationships shown are when the design parameters are the same.

[0188] Number of pairs of IDT electrode fingers: 60 pairs

[0189] Ellipticity coefficient of electrode finger shape α2 / α1: 0.9

[0190] Length of offset electrode: 3.5λ

[0191] Crossing angle: θ c_AP1 ...10°, θ c_AP2 …-10°

[0192] Number of electrode fingers of reflector: 20 pairs

[0193] Fig.30 It is a diagram showing the impedance frequency characteristics in the first embodiment and the fifth embodiment. Fig.31 It is a diagram showing the phase characteristics around 2.2 times the resonance frequency in the first embodiment and the fifth embodiment. Fig.32 It is a diagram showing the return loss in the first embodiment and the fifth embodiment.

[0194] like Fig.30 As shown in FIG. 1 , in the fifth embodiment, the difference between the resonant frequency and the anti-resonant frequency becomes smaller. Therefore, it can be seen that the value of the fractional bandwidth becomes smaller. Fig.31 As shown, it can be seen that in the fifth embodiment, the high-order mode generated around 2.2 times the resonance frequency can be effectively suppressed.

[0195] In addition, if Fig.32 As shown, it can be seen that in the fifth embodiment, the response at the upper end of the stop band can be suppressed. In the fifth embodiment, the ellipticity coefficient α2 / α1 of the shape of the plurality of electrode fingers is less than 1. Accordingly, the frequency at the upper end of the stop band is dispersed. Therefore, the response at the upper end of the stop band can be suppressed.

[0196] In the first to fifth embodiments, the duty ratio or the electrode finger pitch is adjusted so that each angle θ in the intersection region D is C However, the thickness of the plurality of electrode fingers may be adjusted so that each angle θ in the intersection region D is approximately equal to the resonant frequency or the anti-resonant frequency. CIn the embodiment, the resonant frequencies or the anti-resonant frequencies are substantially consistent with each other. This example is shown in the sixth embodiment.

[0197] The sixth embodiment differs from the first embodiment in that the duty ratio of the IDT electrode is constant and the thickness of the plurality of electrode fingers is not constant. Except for the above points, the elastic wave device of the present embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0198] Fig.33 is an absolute value of the angle |θ of the IDT electrode in the sixth embodiment. C |A diagram showing the relationship between the thickness of the electrode fingers.

[0199] like Fig.33 As shown, in the sixth embodiment, the absolute value of the angle |θ C | is larger, the thinner the electrode finger is. C The resonant frequencies are roughly consistent with each other.

[0200] In the sixth embodiment, similarly to the first embodiment, the lengths of the plurality of electrode fingers are different from each other. Also, the curvatures of the arc-shaped portions of the plurality of electrode fingers in a plan view are different from each other. This can suppress unnecessary waves and deterioration of resonance characteristics.

[0201] In the first to sixth embodiments, the IDT electrodes are structured so that each angle θ in the intersection region D is C However, the thickness of the dielectric film covering the IDT electrode can be adjusted so that each angle θ in the intersection region D is approximately equal to the resonant frequency or the antiresonant frequency. C In this case, the resonant frequencies or the anti-resonant frequencies are substantially consistent with each other. This example is shown in the seventh embodiment and its modified example.

[0202] Fig.34 : is a schematic front cross-sectional view of an elastic wave device according to the seventh embodiment. Fig.34 is a schematic cross-sectional view along reference line N.

[0203] The present embodiment differs from the first embodiment in that the electrode finger pitch is fixed in the IDT electrode. The present embodiment also differs from the first embodiment in that a dielectric film 65 is provided on the piezoelectric layer 6 so as to cover the IDT electrode 68. Except for the above aspects, the elastic wave device of the present embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0204] The acoustic velocity of the transverse wave propagating through the dielectric film 65 of this embodiment is lower than the acoustic velocity of the main mode propagating through the dielectric film 65. The thickness of the dielectric film 65 is determined by the angle θ. C Specifically, each portion of the dielectric film 65 covers each portion of the IDT electrode 68. Furthermore, the thickness of each portion of the dielectric film 65 varies according to the angle θ of the portion of the IDT electrode 68 covered by each portion of the dielectric film 65. C But different.

[0205] Fig.35 is an absolute value of the angle |θ| of the portion of the IDT electrode covered by the dielectric film in the seventh embodiment. C |A graph showing the relationship between and the thickness of the dielectric film.

[0206] like Fig.35 As shown, in this embodiment, the angle θ of the portion of the IDT electrode 68 covered by the dielectric film 65 is C The larger the value, the thinner the dielectric film 65 is. C The resonant frequencies are roughly consistent with each other.

[0207] In this embodiment, as in the first embodiment, the lengths of the plurality of electrode fingers are different from each other. Also, the curvatures of the arc-shaped portions of the plurality of electrode fingers in a plan view are different from each other. This can suppress unnecessary waves and reduce degradation of resonance characteristics.

[0208] In the seventh embodiment, the acoustic velocity of the transverse wave propagating in the dielectric film 65 is lower than the acoustic velocity of the main mode propagating in the dielectric film 65. However, the relationship between the acoustic velocities of the waves propagating in the dielectric film is not limited to the above. A modified example of the seventh embodiment is shown below, in which only the acoustic velocity of the transverse wave propagating in the dielectric film is different from that of the seventh embodiment.

[0209] In the modified example of the seventh embodiment, the acoustic velocity of the transverse wave propagating in the dielectric film is higher than the acoustic velocity of the main mode propagating in the dielectric film. In this modified example, the absolute value of the angle of the portion of the IDT electrode covered by the dielectric film |θ C | and the thickness of the dielectric film are related as follows Fig.36 More specifically, in this modification, the angle θ of the portion of the IDT electrode covered by the dielectric film is C The larger the value, the thicker the dielectric film. C Thus, in this modification, as in the seventh embodiment, unnecessary waves can be suppressed and degradation of the resonance characteristics can be suppressed.

[0210] In the first to seventh embodiments, the arbitrary angle θ in the intersection region D is shown. C In the present invention, at least one of the duty ratio, the electrode finger pitch, the electrode finger thickness, and the dielectric film thickness is adjusted according to the angle θ. C Therefore, as described above, it is sufficient to make the resonant frequencies or the anti-resonant frequencies substantially coincide with each other.

[0211] Hereinafter, examples of structures utilizing the piston mode are shown in the eighth to tenth embodiments. In the eighth to tenth embodiments, as in the first embodiment, unnecessary waves can be suppressed and degradation of resonance characteristics can be suppressed. In particular, the transverse mode can be further suppressed.

[0212] Fig.37 It is a schematic plan view of an elastic wave device according to the eighth embodiment.

[0213] The present embodiment is different from the first embodiment in that each of the plurality of electrode fingers has a wide portion. Except for the above point, the elastic wave device of the present embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0214] The intersection region D of the IDT electrode 78 includes a central region H and a first edge region E1 and a second edge region E2. The first edge region E1 and the second edge region E2 sandwich the central region H in a direction in which the first bus bar 14 and the second bus bar 15 are opposed to each other. The first edge region E1 is located on the first bus bar 14 side. The second edge region E2 is located on the second bus bar 15 side.

[0215] The portions of the plurality of first electrode fingers 76 located in the first edge region E1 are provided with wide width portions 76a, respectively. The portions of the plurality of first electrode fingers 76 located in the second edge region E2 are provided with wide width portions 76b, respectively. Similarly, the portions of the plurality of second electrode fingers 77 located in the first edge region E1 are provided with wide width portions 77a, respectively. The portions of the plurality of second electrode fingers 77 located in the second edge region E2 are provided with wide width portions 77b, respectively. The width of the wide width portion in the electrode finger is wider than the width of the portion of the electrode finger located in the central region H.

[0216] In the present embodiment, in the first edge region E1, a plurality of electrode fingers are provided with wide width portions. Accordingly, a low sound velocity region is formed in the first edge region E1. In addition, the so-called low sound velocity region is a region where the sound velocity is lower than the sound velocity in the central region H. Similarly, in the second edge region E2, a plurality of electrode fingers are provided with wide width portions. Accordingly, a low sound velocity region is formed in the second edge region E2. However, it is sufficient that at least one electrode finger among the plurality of electrode fingers has a wide width portion in at least one of the first edge region E1 and the second edge region E2.

[0217] In the region where the gap G1 is arranged, only the first electrode fingers 76 and the second electrode fingers 77 are provided. Thus, a high-acoustic-velocity region is formed in this region. In addition, the so-called high-acoustic-velocity region is a region where the acoustic velocity is higher than the acoustic velocity in the central region H. Similarly, in the region where the gap G2 is arranged, only the first electrode fingers 76 and the second electrode fingers 77 are provided. Thus, a high-acoustic-velocity region is formed in this region.

[0218] The central region H, the low acoustic velocity region, and the high acoustic velocity region are sequentially arranged from the inner side to the outer side of the IDT electrode 78. Thus, a piston mode is established, and the transverse mode can be further suppressed.

[0219] Fig.38 FIG. 2 is a schematic plan view showing the vicinity of the first edge region and the vicinity of the second edge region of the elastic wave device according to the ninth embodiment. Fig.38 In FIG. 1 , a mass addition film described later is indicated by hatching.

[0220] This embodiment differs from the first embodiment in that a mass addition film 72 is provided on each of the plurality of electrode fingers in the first edge region E1 and the second edge region E2. Except for the above, the elastic wave device of this embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0221] More specifically, in this embodiment, a plurality of mass addition films 72 are provided in the first edge region E1 and the second edge region, respectively. More specifically, in each of the first edge region E1 and the second edge region E2, a mass addition film 72 is provided on each electrode finger. Thus, a low sound velocity region is formed in the first edge region E1 and the second edge region E2. Thus, a piston mode is established, and the transverse mode can be further suppressed.

[0222] When the mass-adding film 72 does not extend across a plurality of electrode fingers as in the present embodiment, an appropriate metal may be used as the material of the mass-adding film 72. The same type of metal as that of the electrode fingers may be used as the material of the mass-adding film 72. In this case, the thickness of the electrode fingers in the first edge region E1 and the second edge region E2 is substantially thicker than the thickness of the electrode fingers in the central region H. However, a different type of metal from that of the electrode fingers may be used as the material of the mass-adding film 72, or an appropriate dielectric may be used.

[0223] Furthermore, the mass adding film 72 may be provided across a plurality of electrode fingers. In this case, as the material of the mass adding film 72 , any appropriate dielectric may be used.

[0224] In this embodiment, the piezoelectric layer 6, the electrode fingers, and the mass-added film 72 are stacked in sequence. However, the piezoelectric layer 6, the mass-added film 72, and the electrode fingers may be stacked in sequence. That is, the mass-added film 72 may be located between the piezoelectric layer 6 and the electrode fingers. The mass-added film 72 only needs to overlap with the electrode fingers when viewed from above. In addition, at least one electrode finger only needs to overlap with the mass-added film 72 when viewed from above.

[0225] The low sound velocity region may be formed by both the structure in which the mass addition film 72 is provided in the present embodiment and the structure in which the wide width portion is provided in the eighth embodiment.

[0226] Fig.39 1 is a schematic plan view showing the vicinity of a first edge region and the vicinity of a second edge region of an elastic wave device according to a tenth embodiment.

[0227] This embodiment differs from the first embodiment in that a dielectric film 75 is provided on the piezoelectric layer 6 so as to cover the IDT electrode 8 and a plurality of mass addition films 73 are provided on the dielectric film 75. Except for the above points, the elastic wave device of this embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0228] A mass addition film 73 is provided in each of the portions of the dielectric film 75 provided in the first edge region E1 and the second edge region E2. Each mass addition film 73 is provided so as to overlap with a plurality of electrode fingers in a plan view. Metal is used as a material of each mass addition film 73. Accordingly, a low sound velocity region is formed in the first edge region E1 and the second edge region E2. As a result, a piston mode is established, and the lateral mode can be further suppressed.

[0229] However, as the material of each mass addition film 73, an appropriate dielectric may be used. As the material of the mass addition film 73, the same type of dielectric as that of the dielectric film 75 may be used. In this case, the thickness of the portion of the dielectric film 75 provided in the first edge region E1 and the second edge region E2 is substantially thicker than the thickness of the portion provided in the central region H. On the other hand, as the material of the mass addition film 73, a dielectric of a different type from that of the dielectric film 75 may be used. In this case, the thickness of the portion of the dielectric film as a stacked body provided in the first edge region E1 and the second edge region E2 is thicker than the thickness of the portion provided in the central region H.

[0230] In addition, a plurality of mass adding films 73 may be provided in each of the first edge region E1 and the second edge region E2 .

[0231] The low acoustic velocity region may be formed by both the structure in which the dielectric film 75 and the mass added film 73 are provided in the present embodiment and the structure in which the wide width portion is provided in the eighth embodiment.

[0232] For example, the elastic wave device according to the present invention can be used in a filter device. This example is shown below.

[0233] Fig.40 This is a circuit diagram of a filter device according to the eleventh embodiment.

[0234] The filter device 80 of this embodiment is a ladder filter. The filter device 80 has a first signal terminal 82 and a second signal terminal 83, and a plurality of series arm resonators and a plurality of parallel arm resonators. In the filter device 80, all series arm resonators and all parallel arm resonators are elastic wave resonators. Moreover, all series arm resonators and all parallel arm resonators are elastic wave devices according to the present invention. However, as long as at least one of the plurality of elastic wave resonators of the filter device 80 is an elastic wave device according to the present invention, it is sufficient.

[0235] The first signal terminal 82 is an antenna terminal. The antenna terminal is connected to an antenna. However, the first signal terminal 82 may not necessarily be an antenna terminal. For example, the first signal terminal 82 and the second signal terminal 83 may be configured as electrode pads or wiring.

[0236] Specifically, the plurality of series arm resonators of the present embodiment are a series arm resonator S1, a series arm resonator S2, and a series arm resonator S3. The plurality of series arm resonators are connected in series with each other between the first signal terminal 82 and the second signal terminal 83. Specifically, the plurality of parallel arm resonators are a parallel arm resonator P1 and a parallel arm resonator P2. The parallel arm resonator P1 is connected between the connection point between the series arm resonator S1 and the series arm resonator S2 and the ground potential. The parallel arm resonator P2 is connected between the connection point between the series arm resonator S2 and the series arm resonator S3 and the ground potential. In addition, the circuit structure of the filter device 80 is not limited to the above. For example, the filter device 80 may also include a longitudinally coupled resonator type elastic wave filter.

[0237] The elastic wave resonator in the filter device 80 is the elastic wave device according to the present invention. Therefore, in the elastic wave resonator in the filter device 80, unnecessary waves can be suppressed, and degradation of resonance characteristics can be suppressed.

[0238] In addition, the curves in the shapes of the plurality of electrode fingers in the elastic wave device of each of the above-mentioned embodiments when viewed from above are smooth curves. In addition, the curves in the shapes of the plurality of electrode fingers when viewed from above may be shapes formed by connecting straight lines of tiny sizes. The curves in the shapes of the plurality of electrode fingers when viewed from above may also be shapes formed by connecting a plurality of vertices to each other by curves. Alternatively, the curves in the shapes of the plurality of electrode fingers when viewed from above may not necessarily be smooth curves. This example is shown as the fifth variant of the first embodiment.

[0239] In by Fig.41 In the IDT electrode 8A in the fifth variant shown in an enlarged manner, the curve in the shape of each first electrode finger 16A when viewed from above is not a smooth curve. Specifically, the shape of each first electrode finger 16A when viewed from above is a shape formed by connecting straight lines. In addition, the straight lines in this shape are not straight lines of tiny size. More specifically, the length of the straight lines in this shape is, for example, a few % of the total length of the first electrode finger 16A. However, in this shape, the angle formed by the connected straight lines is, for example, as large as 160° or more and less than 180°. Therefore, the shape of each first electrode finger 16A when viewed from above is a shape that can be approximated by a curve.

[0240] The shape of each second electrode finger 17A in plan view is also the same as the shape of each first electrode finger 16A in plan view. In this modification, as in the first embodiment, unnecessary waves can be suppressed and degradation of resonance characteristics can be suppressed.

[0241] Fig.42 It is a schematic front cross-sectional view of an elastic wave device according to a twelfth embodiment.

[0242] The present embodiment is different from the first embodiment in that the IDT electrode 8 is buried in the protective film 99. Except for the above-described point, the elastic wave device of the present embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0243] Specifically, a protective film 99 is provided on the piezoelectric layer 6 so as to cover the IDT electrode 8. The thickness of the protective film 99 is thicker than the thickness of the IDT electrode 8. The IDT electrode 8 is buried in the protective film 99. Thus, the IDT electrode 8 is less likely to be damaged.

[0244] The protective film 99 has a first protective layer 99a and a second protective layer 99b. The IDT electrode 8 is buried in the first protective layer 99a. The second protective layer 99b is provided on the first protective layer 99a. Accordingly, a plurality of effects can be obtained by the protective film 99. Specifically, in the present embodiment, silicon oxide is used as the material of the first protective layer 99a. Thus, the absolute value of the temperature coefficient of frequency (TCF) in the elastic wave device can be reduced. Therefore, the temperature characteristics of the elastic wave device can be improved. For the second protective layer 99b, silicon nitride is used. Thus, the moisture resistance of the elastic wave device can be improved.

[0245] In the present embodiment, the IDT electrode 8 is also configured in the same manner as in the first embodiment. This can suppress unnecessary waves and also suppress degradation of resonance characteristics.

[0246] The materials of the first protective layer 99a and the second protective layer 99b are not limited to those described above. The protective film 99 may be a single layer or a laminate of three or more layers.

[0247] Fig.43 It is a schematic front cross-sectional view of an elastic wave device according to a thirteenth embodiment.

[0248] The present embodiment is different from the first embodiment in that an IDT electrode 8 is provided on both the first principal surface 6a and the second principal surface 6b of the piezoelectric layer 6. In addition, the IDT electrode 8 provided on the second principal surface 6b is embedded in the second layer 5b of the dielectric layer 5. Except for the above-mentioned aspects, the elastic wave device of the present embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0249] The IDT electrode 8 provided on the first principal surface 6a of the piezoelectric layer 6 and the IDT electrode 8 provided on the second principal surface 6b are opposed to each other with the piezoelectric layer 6 interposed therebetween. In the elastic wave device of this embodiment, the IDT electrode 8 on the first principal surface 6a is configured in the same manner as in the first embodiment. Thus, unnecessary waves can be suppressed and degradation of resonance characteristics can be suppressed.

[0250] Furthermore, for example, the IDT electrodes 8 provided on the first principal surface 6 a and the second principal surface 6 b of the piezoelectric layer 6 may have different design parameters.

[0251] The following describes the first to third variants of the 13th embodiment, in which at least one of the structure of the electrode provided on the second main surface of the piezoelectric layer and the stacked structure of the piezoelectric substrate is different from the 13th embodiment. In the first to third variants, as in the 13th embodiment, it is possible to suppress unnecessary waves and suppress degradation of resonance characteristics.

[0252] exist Fig.44 In the first variation shown, the layer structure of the piezoelectric substrate 92 is different from that of the thirteenth embodiment. Specifically, the piezoelectric substrate 92 has a supporting substrate 4, a dielectric layer 95, and a piezoelectric layer 6. The dielectric layer 95 is provided on the supporting substrate 4. The piezoelectric layer 6 is provided on the dielectric layer 95. In this variation, the dielectric layer 95 has a frame shape. That is, the dielectric layer 95 has a through hole.

[0253] The support substrate 4 blocks one side of the through hole of the dielectric layer 95. The piezoelectric layer 6 blocks the other side of the through hole of the dielectric layer 95. Thus, a hollow portion 92c is formed in the piezoelectric substrate 92. A portion of the piezoelectric layer 6 and a portion of the support substrate 4 face each other with the hollow portion 92c sandwiched therebetween. The IDT electrode 8 provided on the second main surface 6b of the piezoelectric layer 6 is located in the hollow portion 92c.

[0254] exist Fig.45 In the second modification shown, a plate-shaped electrode 98 is provided on the second main surface 6b of the piezoelectric layer 6. The IDT electrode 8 and the electrode 98 face each other with the piezoelectric layer 6 interposed therebetween.

[0255] exist Fig.46 In the third modification shown, the piezoelectric substrate 92 is configured similarly to the first modification, and an electrode 98 similar to the second modification is provided on the second principal surface 6b of the piezoelectric layer 6. The electrode 98 is located in the hollow portion 92c.

[0256] In the 12th embodiment, the 13th embodiment and each modified example, an example is shown in which the IDT electrode 8 has the same structure as the first embodiment. However, when the structure of the IDT electrode is set to the structure of the present invention other than the first embodiment, the structures of the 12th embodiment, the 13th embodiment and each modified example can also be adopted.

[0257] Examples of aspects of the elastic wave device and the filter device according to the present invention are summarized and described below.

[0258] <1> An elastic wave device comprises: a piezoelectric substrate including a piezoelectric layer; and an IDT electrode arranged on the piezoelectric layer, the IDT electrode having a first bus bar and a second bus bar facing each other, a plurality of first electrode fingers connected to the first bus bar at one end, and a plurality of second electrode fingers connected to the second bus bar at one end, the plurality of first electrode fingers and the plurality of second electrode fingers are interlaced with each other, the portion where the first electrode fingers and the second electrode fingers overlap in the elastic wave propagation direction is an intersection region, the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view include a curved portion, and in the intersection region, the resonant frequencies or anti-resonant frequencies are substantially consistent with each other.

[0259] <2> exist <1> In the elastic wave device described, the curved portion included in the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers is in the shape of a circular arc or an elliptical arc, the center of a circle including the circular arc in the shape of the first electrode fingers and the second electrode fingers or the midpoint of two foci of an ellipse including the elliptical arc is set as a fixed point, a straight line passing through the center of the intersection region in the direction in which the plurality of first electrode fingers and the plurality of second electrode fingers extend is set as a reference line, and an angle formed by the straight line passing through the fixed point and the reference line is set as θ C When any of the angles θ in the intersection region C In the embodiment, the resonant frequencies or the anti-resonant frequencies are substantially consistent with each other.

[0260] <3> An elastic wave device comprises: a piezoelectric substrate including a piezoelectric layer; and an IDT electrode disposed on the piezoelectric layer, the IDT electrode comprising a first bus bar and a second bus bar facing each other, a plurality of first electrode fingers connected to the first bus bar at one end, and a plurality of second electrode fingers connected to the second bus bar at one end, the plurality of first electrode fingers and the plurality of second electrode fingers being interlaced with each other, a portion where the first electrode fingers and the second electrode fingers overlap in an elastic wave propagation direction being a crossover region, the plurality of first electrode fingers and the plurality of second electrode fingers having a shape of an arc or an elliptical arc in a plan view, the center of a circle including the first electrode fingers and the second electrode fingers or a midpoint of two foci of an elliptical arc in the shape being set as a fixed point, a straight line passing through the center of the crossover region in a direction in which the plurality of first electrode fingers and the plurality of second electrode fingers extend being set as a reference line, and an angle formed by the straight line passing through the fixed point and the reference line being set as θ C When C The larger the absolute value of is, the narrower the electrode finger spacing is.

[0261] <4> exist <2> or <3> In the elastic wave device described above, the electrode finger pitch is determined according to the angle θ C and changes so that any of the angles θ in the intersection region C In the embodiment, the resonant frequencies or the anti-resonant frequencies are substantially consistent with each other.

[0262] <5> exist <1> to <4> In the elastic wave device described in any one of the above, lithium tantalate or lithium niobate is used as the material of the piezoelectric layer.

[0263] <6> exist <1> to <5> In the elastic wave device described in any one of the above, the piezoelectric substrate includes a supporting substrate, and the piezoelectric layer is provided on the supporting substrate.

[0264] <7> exist <6> In the elastic wave device described above, the piezoelectric substrate includes a dielectric layer, and the dielectric layer is provided between the supporting substrate and the piezoelectric layer.

[0265] <8> exist <6> or <7> In the elastic wave device described above, silicon is used as the material of the supporting substrate.

[0266] <9> An elastic wave device comprises: a piezoelectric substrate including a piezoelectric layer; and an IDT electrode disposed on the piezoelectric layer, wherein the piezoelectric substrate is one of a substrate in which the piezoelectric layer made of lithium tantalate or lithium niobate and a supporting substrate are stacked, and a substrate including only the piezoelectric layer made of lithium niobate, wherein the IDT electrode comprises a first bus bar and a second bus bar facing each other, a plurality of first electrode fingers connected to the first bus bar at one end, and a plurality of second electrode fingers connected to the second bus bar at one end, wherein the plurality of first electrode fingers and the plurality of second electrode fingers are arranged in a staggered manner. The portion where the first electrode finger and the second electrode finger overlap each other in the direction of propagation of the elastic wave is an intersection region, the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view include a circular arc or an elliptical arc, the center of the circle including the circular arc in the shape of the first electrode finger and the second electrode finger or the midpoint of the two foci of the elliptical arc is set as a fixed point, a straight line passing through the center of the intersection region in the direction in which the plurality of first electrode fingers and the plurality of second electrode fingers extend is set as a reference line, and an angle formed by the straight line passing through the fixed point and the reference line is set as θ C When the plurality of first electrode fingers and the plurality of second electrode fingers have the angle θ C The larger the absolute value of θ is, the wider the electrode finger pitch is, and the angle θ C One of the structures in which the electrode finger pitch becomes narrower as the absolute value of becomes larger.

[0267] <10> exist <3> or <9> In the elastic wave device described above, any of the angles θ in the intersection region C In the embodiment, the resonant frequencies or the anti-resonant frequencies are substantially consistent with each other.

[0268] <11> exist <1> to <10> In the elastic wave device described in any one of the items, the curved portion included in the shape of the plurality of first electrode fingers and the plurality of second electrode fingers is in the shape of a circular arc or an elliptical arc, the center of the circle including the circular arc in the shape of the first electrode fingers and the second electrode fingers or the midpoint of the two foci of the elliptical arc included in the shape of the elliptical arc is set as a fixed point, a straight line passing through the center of the intersection area in the direction in which the plurality of first electrode fingers and the plurality of second electrode fingers extend is set as a reference line, and an angle formed by the straight line passing through the fixed point and the reference line is set as θ C When the duty ratio and at least one of the thicknesses of the plurality of first electrode fingers and the plurality of second electrode fingers is adjusted according to the angle θ C and changes so that any of the angles θ in the intersection region C In the embodiment, the resonant frequencies or the anti-resonant frequencies are substantially consistent with each other.

[0269] <12> exist <1> to <11> In the elastic wave device described in any one of the items, the elastic wave device further includes a dielectric film, the dielectric film is provided on the piezoelectric layer so as to cover the IDT electrode, the curved portion included in the shape of the plurality of first electrode fingers and the plurality of second electrode fingers is in the shape of a circular arc or an elliptical arc, the center of the circle including the circular arc in the shape of the first electrode fingers and the second electrode fingers or the midpoint of the two foci of the elliptical arc included in the shape of the elliptical arc is set as a fixed point, a straight line passing through the center of the intersection area in the direction in which the plurality of first electrode fingers and the plurality of second electrode fingers extend is set as a reference line, and an angle formed by the straight line passing through the fixed point and the reference line is set as θ C When the thickness of the dielectric film is C and changes so that in the intersection region, at any angle θ C In the embodiment, the resonant frequencies or the anti-resonant frequencies are substantially consistent with each other.

[0270] <13> exist <2> to <4> , <9> as well as <10> In the elastic wave device described in any one of the above, when α2 / α1 is defined as an ellipticity coefficient of the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view, α2 / α1>1.

[0271] <14> exist <2> to <4> , <9> as well as <10> In the elastic wave device described in any one of the above, when α2 / α1 is defined as an ellipticity coefficient of the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view, α2 / α1=1.

[0272] <15> exist <2> to <4> , <9> as well as <10> In the elastic wave device described in any one of the above, when α2 / α1 is defined as an ellipticity coefficient of the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view, α2 / α1<1.

[0273] <16> exist <2> , <3> , <9> , <10> as well as <13> to <15> In the elastic wave device described in any one of the above, the plurality of first electrode fingers and the plurality of second electrode fingers include at least two of the first electrode fingers or the second electrode fingers having shapes with different curvatures in plan view.

[0274] <17> exist <16> In the elastic wave device described above, the curvatures of the plurality of first electrode fingers and the plurality of second electrode fingers gradually change from one side toward the other side in the direction in which the plurality of first electrode fingers and the plurality of second electrode fingers are arranged.

[0275] <18> exist <2> , <3> , <9> , <10> as well as <13> to <17> In the elastic wave device described in any one of the above, each of the first electrode finger and the second electrode finger includes a portion having a different curvature in a plan view.

[0276] <19> exist <18> In the elastic wave device described above, the curvatures of the first electrode fingers and the second electrode fingers increase with the angle θ. C The absolute value of becomes larger and changes gradually.

[0277] <20> exist <18> In the elastic wave device described above, the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view include straight line shapes.

[0278] <21> exist <1> to <20> In the elastic wave device described in any one of the items, a piezoelectric single crystal is used as the material of the piezoelectric layer, the piezoelectric layer has a propagation axis, and the curved portion included in the shape of the multiple first electrode fingers and the multiple second electrode fingers is in the shape of a circular arc or an elliptical arc. When the center of the circle including the circular arc in the shape of the first electrode fingers and the second electrode fingers or the midpoint of the two foci of the elliptical arc included in the elliptical arc is set as a fixed point, and a straight line passing through the center of the intersection area in the direction in which the multiple first electrode fingers and the multiple second electrode fingers extend is set as a reference line, the propagation axis and the reference line extend in parallel.

[0279] <22> exist <1> to <21> In the elastic wave device described in any one of the items, the top ends of the multiple first electrode fingers are respectively opposite to the second bus bar with at least a gap therebetween, the curved portion included in the shapes of the multiple first electrode fingers and the multiple second electrode fingers is in the shape of a circular arc or an elliptical arc, and when the center of the circle including the circular arc in the shape of the first electrode fingers and the second electrode fingers or the midpoint of the two foci of the elliptical arc included in the shape is set as a fixed point, and a straight line passing through the center of the intersection area in the direction in which the multiple first electrode fingers and the multiple second electrode fingers extend is set as a reference line, the direction in which an imaginary line connecting each of the gaps extends intersects with the direction in which the reference line extends.

[0280] <23> exist <1> to <22> In the elastic wave device described in any one of the items, the top ends of the plurality of first electrode fingers are respectively opposed to the second bus bar with at least a gap therebetween, the curved portion included in the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers is in the shape of a circular arc or an elliptical arc, and when the center of the circle including the circular arc in the shape of the first electrode fingers and the second electrode fingers or the midpoint of the two foci of the elliptical arc included in the shape is set as a fixed point, and a straight line passing through the center of the intersection area in the direction in which the plurality of first electrode fingers and the plurality of second electrode fingers extend is set as a reference line, when the wavelength specified by the electrode finger spacing of the portion of the IDT electrode through which the reference line passes is set to λ, the dimension of each of the gaps along the direction in which the top ends of each of the first electrode fingers and the second bus bar are opposed is less than 0.56λ.

[0281] <24> exist <1> to <23> In the elastic wave device described in any one of the items, the IDT electrode includes a plurality of first offset electrodes and a plurality of second offset electrodes, the plurality of first offset electrodes are respectively connected to the first bus bar, the plurality of second offset electrodes are respectively connected to the second bus bar, and the top ends of the first electrode fingers and the top ends of the second offset electrodes are opposed to each other with a gap therebetween.

[0282] <25> exist <1> to <24> In the elastic wave device described in any one of the items, the intersection region has a central region and a first edge region and a second edge region sandwiching the central region in a direction in which the first bus bar and the second bus bar are opposite to each other, and the plurality of first electrode fingers and the plurality of second electrode fingers have at least one of a structure in which the widths in the first edge region and the second edge region are wider than the width in the central region, and a structure in which the thicknesses in the first edge region and the second edge region are thicker than the thickness in the central region.

[0283] <26> exist <1> to <25> In the elastic wave device described in any one of the items, the elastic wave device further includes a dielectric film, the dielectric film is arranged on the piezoelectric layer so as to cover the IDT electrode, the intersection area has a central area and a first edge area and a second edge area sandwiching the central area in a direction in which the first bus bar and the second bus bar are opposite to each other, and the thickness of the portion of the dielectric film arranged in the first edge area and the second edge area is thicker than the thickness of the portion of the dielectric film arranged in the central area.

[0284] <27> exist <1> to <26> In the elastic wave device described in any one of the items, the elastic wave device also includes a dielectric film, the dielectric film is arranged on the piezoelectric layer so as to cover the IDT electrode, the intersection area has a central area and a first edge area and a second edge area sandwiching the central area in the direction in which the first bus bar and the second bus bar are opposite to each other, and a mass addition film is provided in the portion of the dielectric film arranged in the first edge area and the second edge area so as to overlap with the multiple first electrode fingers and the multiple second electrode fingers in a plan view, and metal is used as the material of the mass addition film.

[0285] <28> A filter device comprises a plurality of elastic wave resonators, at least one of which is <1> to <27> An elastic wave device as described in any one of the items.

[0286] Description of Reference Numerals

[0287] 1…Elastic wave device

[0288] 2, 2A, 2B…Piezoelectric substrate

[0289] 3…Supporting member

[0290] 4. 4B…Supporting base plate

[0291] 4c…concave part

[0292] 5.5A…Dielectric layer

[0293] 5a, 5b…1st floor, 2nd floor

[0294] 6…Piezoelectric layer

[0295] 7… Acoustic reflective membrane

[0296] 8, 8A…IDT electrode

[0297] 9A, 9B…Reflector

[0298] 9a, 9b…Electrode fingers

[0299] 12a, 12b…low acoustic impedance layer

[0300] 13a, 13b, 13c... high acoustic impedance layer

[0301] 14, 15…1st bus bar, 2nd bus bar

[0302] 16, 17…1st electrode finger, 2nd electrode finger

[0303] 16A, 17A...1st electrode finger, 2nd electrode finger

[0304] 18, 19 ... first offset electrode, second offset electrode

[0305] 28, 38, 48, 58…IDT electrode

[0306] 65…Dielectric film

[0307] 68…IDT electrode

[0308] 72, 73…Quality additional film

[0309] 75…Dielectric film

[0310] 76, 77…1st electrode finger, 2nd electrode finger

[0311] 76a, 76b, 77a, 77b ... wide width portion

[0312] 78…IDT electrode

[0313] 80…Filter device

[0314] 82, 83…1st signal terminal, 2nd signal terminal

[0315] 92…Piezoelectric substrate

[0316] 92c…Hollow part

[0317] 95…Dielectric layer

[0318] 98…Electrode

[0319] 99…Protective film

[0320] 99a, 99b...1st protective layer, 2nd protective layer

[0321] 108…IDT electrode

[0322] 109A, 109B…Reflector

[0323] C…Fixed point

[0324] D…Crossover area

[0325] E1, E2…1st edge area, 2nd edge area

[0326] G1, G2… Clearance

[0327] H…Central area

[0328] P1, P2…Parallel arm resonator

[0329] S1~S3…Series arm resonator

[0330] W1~W3…1st area to 3rd area.

Claims

1. An elastic wave device comprising: A piezoelectric substrate including a piezoelectric layer; and IDT electrode, disposed on the piezoelectric layer, The IDT electrode includes a first bus bar and a second bus bar facing each other, a plurality of first electrode fingers connected to the first bus bar at one end, and a plurality of second electrode fingers connected to the second bus bar at one end. The plurality of first electrode fingers and the plurality of second electrode fingers are interlaced with each other, and a portion where the first electrode fingers and the second electrode fingers overlap each other in the elastic wave propagation direction is a crossing region. The shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view include curved portions, In the intersection region, the resonant frequencies or the anti-resonant frequencies are substantially consistent with each other.

2. The elastic wave device according to claim 1, wherein: The curved portion included in the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers is in the shape of a circular arc or an elliptical arc, The center of the circle of the arc in the shape including the first electrode finger and the second electrode finger or the midpoint of the two foci of the ellipse including the elliptical arc is set as a fixed point, a straight line passing through the center of the intersection region in the direction in which the plurality of first electrode fingers and the plurality of second electrode fingers extend is set as a reference line, and an angle formed by the straight line passing through the fixed point and the reference line is set as θ C When any of the angles θ in the intersection region C In the embodiment, the resonant frequencies or the anti-resonant frequencies are substantially consistent with each other.

3. An elastic wave device comprising: A piezoelectric substrate including a piezoelectric layer; and IDT electrode, disposed on the piezoelectric layer, The IDT electrode includes a first bus bar and a second bus bar facing each other, a plurality of first electrode fingers connected to the first bus bar at one end, and a plurality of second electrode fingers connected to the second bus bar at one end. The plurality of first electrode fingers and the plurality of second electrode fingers are interlaced with each other, and a portion where the first electrode fingers and the second electrode fingers overlap each other in the elastic wave propagation direction is a crossing region. The shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view include circular arc shapes or elliptical arc shapes. The center of the circle of the arc in the shape including the first electrode finger and the second electrode finger or the midpoint of the two foci of the ellipse including the elliptical arc is set as a fixed point, a straight line passing through the center of the intersection region in the direction in which the plurality of first electrode fingers and the plurality of second electrode fingers extend is set as a reference line, and an angle formed by the straight line passing through the fixed point and the reference line is set as θ C When C The larger the absolute value of is, the narrower the electrode finger spacing is.

4. The elastic wave device according to claim 2 or 3, wherein: The electrode finger pitch is based on the angle θ C and changes so that any of the angles θ in the intersection region C In the embodiment, the resonant frequencies or the anti-resonant frequencies are substantially consistent with each other.

5. The elastic wave device according to any one of claims 1 to 4, wherein: As the material of the piezoelectric layer, lithium tantalate or lithium niobate is used.

6. The elastic wave device according to any one of claims 1 to 5, wherein: The piezoelectric substrate has a supporting substrate. The piezoelectric layer is provided on the supporting substrate.

7. The elastic wave device according to claim 6, wherein: The piezoelectric substrate has a dielectric layer. The dielectric layer is provided between the support substrate and the piezoelectric layer.

8. The elastic wave device according to claim 6 or 7, wherein: Silicon is used as the material of the support substrate.

9. An elastic wave device comprising: A piezoelectric substrate including a piezoelectric layer; and IDT electrode, disposed on the piezoelectric layer, The piezoelectric substrate is one of a substrate in which the piezoelectric layer made of lithium tantalate or lithium niobate and a support substrate are stacked, and a substrate including only the piezoelectric layer made of lithium niobate. The IDT electrode includes a first bus bar and a second bus bar facing each other, a plurality of first electrode fingers connected to the first bus bar at one end, and a plurality of second electrode fingers connected to the second bus bar at one end. The plurality of first electrode fingers and the plurality of second electrode fingers are interlaced with each other, and a portion where the first electrode fingers and the second electrode fingers overlap each other in the elastic wave propagation direction is a crossing region. The shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view include circular arc shapes or elliptical arc shapes. The center of the circle of the arc in the shape including the first electrode finger and the second electrode finger or the midpoint of the two foci of the ellipse including the elliptical arc is set as a fixed point, a straight line passing through the center of the intersection region in the direction in which the plurality of first electrode fingers and the plurality of second electrode fingers extend is set as a reference line, and an angle formed by the straight line passing through the fixed point and the reference line is set as θ C When the plurality of first electrode fingers and the plurality of second electrode fingers have the angle θ C The larger the absolute value of θ is, the wider the electrode finger pitch is, and the angle θ C One of the structures in which the electrode finger pitch becomes narrower as the absolute value of becomes larger.

10. The elastic wave device according to claim 3 or 9, wherein: Any of the angles θ within the intersection region C In the embodiment, the resonant frequencies or the anti-resonant frequencies are substantially consistent with each other.

11. The elastic wave device according to any one of claims 1 to 10, wherein: The curved portion included in the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers is in the shape of a circular arc or an elliptical arc, The center of the circle of the arc in the shape including the first electrode finger and the second electrode finger or the midpoint of the two foci of the ellipse including the elliptical arc is set as a fixed point, a straight line passing through the center of the intersection region in the direction in which the plurality of first electrode fingers and the plurality of second electrode fingers extend is set as a reference line, and an angle formed by the straight line passing through the fixed point and the reference line is set as θ C When the duty ratio and at least one of the thicknesses of the plurality of first electrode fingers and the plurality of second electrode fingers is adjusted according to the angle θ C and changes so that any of the angles θ in the intersection region C In the embodiment, the resonant frequencies or the anti-resonant frequencies are substantially consistent with each other.

12. The elastic wave device according to any one of claims 1 to 11, wherein: The elastic wave device further includes a dielectric film provided on the piezoelectric layer so as to cover the IDT electrode. The curved portion included in the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers is in the shape of a circular arc or an elliptical arc, The center of the circle of the arc in the shape including the first electrode finger and the second electrode finger or the midpoint of the two foci of the ellipse including the elliptical arc is set as a fixed point, a straight line passing through the center of the intersection region in the direction in which the plurality of first electrode fingers and the plurality of second electrode fingers extend is set as a reference line, and an angle formed by the straight line passing through the fixed point and the reference line is set as θ C When the thickness of the dielectric film is C and changes so that in the intersection region, at any angle θ C In the embodiment, the resonant frequencies or the anti-resonant frequencies are substantially consistent with each other.

13. The elastic wave device according to any one of claims 2 to 4, 9 and 10, wherein: When α2 / α1 is defined as the ellipticity coefficient of the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view, α2 / α1>1.

14. The elastic wave device according to any one of claims 2 to 4, 9 and 10, wherein: When α2 / α1 is defined as the ellipticity coefficient of the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view, α2 / α1=1.

15. The elastic wave device according to any one of claims 2 to 4, 9 and 10, wherein: When α2 / α1 is defined as the ellipticity coefficient of the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view, α2 / α1<1.

16. The elastic wave device according to any one of claims 2, 3, 9, 10, and 13 to 15, wherein: The plurality of first electrode fingers and the plurality of second electrode fingers include at least two of the first electrode fingers or the second electrode fingers having shapes with different curvatures in a plan view.

17. The elastic wave device according to claim 16, wherein: The curvatures of the plurality of first electrode fingers and the plurality of second electrode fingers gradually change from one side toward the other side in the direction in which the plurality of first electrode fingers and the plurality of second electrode fingers are arranged.

18. The elastic wave device according to any one of claims 2, 3, 9, 10, and 13 to 17, wherein: Each of the first electrode finger and the second electrode finger includes a portion having a different curvature in a plan view.

19. The elastic wave device according to claim 18, wherein: The curvatures of the first electrode fingers and the second electrode fingers change with the angle θ. C The absolute value of becomes larger and changes gradually.

20. The elastic wave device according to claim 18, wherein The shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view include a straight line shape.

21. The elastic wave device according to any one of claims 1 to 20, wherein: A piezoelectric single crystal is used as a material of the piezoelectric layer. The piezoelectric layer has a propagation axis, The curved portion included in the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers is in the shape of a circular arc or an elliptical arc, When the center of the circle of the arc in the shape of the first electrode finger and the second electrode finger or the midpoint of the two foci of the ellipse including the elliptical arc is set as a fixed point, and a straight line passing through the center of the intersection area in the direction in which the multiple first electrode fingers and the multiple second electrode fingers extend is set as a reference line, the propagation axis and the reference line extend in parallel.

22. The elastic wave device according to any one of claims 1 to 21, wherein: The top ends of the plurality of first electrode fingers are opposed to the second bus bar with at least a gap therebetween. The curved portion included in the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers is in the shape of a circular arc or an elliptical arc, When the center of the circle of the arc in the shape of the first electrode finger and the second electrode finger or the midpoint of the two foci of the ellipse including the elliptical arc is set as a fixed point, and a straight line passing through the center of the intersection area in the direction in which the multiple first electrode fingers and the multiple second electrode fingers extend is set as a baseline, the direction in which the imaginary line connecting the gaps to each other extends intersects with the direction in which the baseline extends.

23. The elastic wave device according to any one of claims 1 to 22, wherein: The top ends of the plurality of first electrode fingers are opposed to the second bus bar with at least a gap therebetween. The curved portion included in the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers is in the shape of a circular arc or an elliptical arc, When the center of the circle of the arc in the shape of the first electrode finger and the second electrode finger or the midpoint of the two foci of the ellipse including the elliptical arc is set as a fixed point, and a straight line passing through the center of the intersection area in the direction in which the multiple first electrode fingers and the multiple second electrode fingers extend is set as a reference line, and when the wavelength specified by the electrode finger spacing of the part of the IDT electrode through which the reference line passes is set to λ, the dimension of each of the gaps along the direction in which the top end of each of the first electrode fingers is opposite to the second bus bar is less than 0.56λ.

24. The elastic wave device according to any one of claims 1 to 23, wherein: The IDT electrode includes a plurality of first offset electrodes and a plurality of second offset electrodes. The plurality of first offset electrodes are connected to the first bus bar, respectively, and the plurality of second offset electrodes are connected to the second bus bar, respectively. The tip portion of the first electrode finger and the tip portion of the second offset electrode face each other with a gap therebetween.

25. The elastic wave device according to any one of claims 1 to 24, wherein: The intersection region includes a central region and a first edge region and a second edge region sandwiching the central region in a direction in which the first bus bar and the second bus bar are opposed to each other. The plurality of first electrode fingers and the plurality of second electrode fingers have at least one of a structure in which the width in the first edge region and the second edge region is wider than the width in the central region, and a structure in which the thickness in the first edge region and the second edge region is thicker than the thickness in the central region.

26. The elastic wave device according to any one of claims 1 to 25, wherein: The elastic wave device further includes a dielectric film provided on the piezoelectric layer so as to cover the IDT electrode. The intersection region includes a central region and a first edge region and a second edge region sandwiching the central region in a direction in which the first bus bar and the second bus bar are opposed to each other. The thickness of the portion of the dielectric film provided in the first edge region and the second edge region is thicker than the thickness of the portion of the dielectric film provided in the central region.

27. The elastic wave device according to any one of claims 1 to 26, wherein: The elastic wave device further includes a dielectric film provided on the piezoelectric layer so as to cover the IDT electrode. The intersection region includes a central region and a first edge region and a second edge region sandwiching the central region in a direction in which the first bus bar and the second bus bar are opposed to each other. A mass addition film is provided in the portion of the dielectric film provided in the first edge region and the second edge region so as to overlap with the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view. Metal is used as a material of the mass adding film.

28. A filter device comprising a plurality of elastic wave resonators, At least one of the elastic wave resonators is the elastic wave device according to any one of claims 1 to 27.

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