Elastic wave device and filter device

Abstract

Provided is an elastic wave device capable of sufficiently suppressing unwanted waves and transverse modes outside a passband. 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: a first bus bar (14) and a second bus bar (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 (16) and the plurality of second electrode fingers (17) are interleaved and inserted with each other. The shapes of the plurality of first electrode fingers (16) and the plurality of second electrode fingers (17) in a plan view include an arc shape or an elliptical arc shape. A virtual line formed by connecting the tips of the plurality of second electrode fingers (17) is defined as a first envelope line (E1), and a virtual line formed by connecting the tips of the plurality of first electrode fingers (16) is defined as a second envelope line (E2). When the center of a circle including an arc in the shape of the first electrode finger (16) and the second electrode finger (17) or the midpoint of two focal points of an ellipse including an elliptical arc is defined as a fixed point (C), a straight line connecting the fixed point (C) and the tip of the second electrode finger (17) is not parallel to the first envelope line (E1), and a straight line connecting the fixed point (C) and the tip of the first electrode finger (16) is not parallel to the second envelope line (E2).

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 at the end portion in the direction. Therefore, there is an effect of suppressing the response of unnecessary waves to a certain extent. However, the unnecessary waves and transverse modes outside the passband cannot be fully suppressed.

[0008] An object of the present invention is to provide an elastic wave device and a filter device capable of sufficiently suppressing unnecessary waves outside a passband and transverse modes.

[0009] Technical solutions to solve problems

[0010] The elastic wave device of the present invention comprises: a piezoelectric substrate including a piezoelectric layer; and an IDT electrode arranged on the piezoelectric layer, wherein the IDT electrode comprises a first bus bar and a second bus bar facing each other, a plurality of first electrode fingers having one end connected to the first bus bar, and a plurality of second electrode fingers having one end connected to the second bus bar, wherein the plurality of first electrode fingers and the plurality of second electrode fingers are interlaced with each other, and the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view include circular arcs or elliptical arcs, and when the first electrode fingers and the second electrode fingers are connected to each other, the first electrode fingers and the second electrode fingers are interlaced with each other. When an imaginary line formed by connecting the top ends of the plurality of second electrode fingers is set as the first envelope, an imaginary line formed by connecting the top ends of the plurality of first electrode fingers is set as the second envelope, and the center of the circle of the arc in the shape including the first electrode fingers and the second electrode fingers or the midpoint of the two foci of the ellipse including the elliptical arc is set as a fixed point, a straight line connecting the fixed point and the top end of the second electrode finger is not parallel to the first envelope, and a straight line connecting the fixed point and the top end of the first electrode finger is not parallel to the second envelope.

[0011] 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.

[0012] Effects of the Invention

[0013] According to the elastic wave device and the filter device according to the present invention, it is possible to sufficiently suppress unnecessary waves and transverse modes outside the passband. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic plan view of the elastic wave device according to the first embodiment of the present invention.

[0015] Figure 2 It is along Figure 1 Schematic cross-sectional view of line II in FIG.

[0016] Figure 3 It is a schematic plan view for explaining the structure of the IDT electrode in the first embodiment of the present invention.

[0017] Figure 4 It is a schematic top view of an IDT electrode in a comparative example.

[0018] Figure 5 It is a graph showing the impedance frequency characteristics in the first embodiment of the present invention and a comparative example.

[0019] Figure 6 It is a diagram showing the phase characteristics in the first embodiment of the present invention and a comparative example.

[0020] Figure 7 It is a diagram showing the inverse velocity surface of the elastic wave propagating through the first piezoelectric substrate and the second piezoelectric substrate.

[0021] Figure 8 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.

[0022] Fig. 9 is an absolute value of the excitation angle |θ of the IDT electrode in the first embodiment, the first modification, and the second modification of the present invention. C_prop |A graph showing the relationship between Ω and duty cycle.

[0023] Fig.10 It is a schematic plan view of an elastic wave device according to a third modified example of the first embodiment of the present invention.

[0024] Fig.11 It is a diagram showing phase characteristics in the vicinity of the resonance frequency in the first embodiment, the third modification, and the comparative example of the present invention.

[0025] Fig.12 It is a diagram showing phase characteristics on the lower frequency side than the resonance frequency in the first embodiment, the third modification, and the comparative example of the present invention.

[0026] Fig.13 It is a diagram showing phase characteristics on the high frequency side compared to the antiresonance frequency in the first embodiment, the third modification, and the comparative example of the present invention.

[0027] Fig.14 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.

[0028] Fig.15 It is a schematic front cross-sectional view of an elastic wave device according to a fifth modified example of the first embodiment of the present invention.

[0029] Fig.16 It is a schematic plan view of an elastic wave device according to a second embodiment of the present invention.

[0030] Fig.17 It is a schematic plan view for explaining the structure of an IDT electrode in the second embodiment of the present invention.

[0031] Fig.18 is an absolute value of the excitation angle |θ of the IDT electrode in the second embodiment of the present invention. C_prop |A graph showing the relationship between Δpitch and the rate of change of the electrode finger pitch.

[0032] Fig.19 It is a schematic plan view of an elastic wave device according to a third embodiment of the present invention.

[0033] Fig. 20 It is a schematic plan view of an elastic wave device according to a fourth embodiment of the present invention.

[0034] Fig.21 is an absolute value of the excitation angle |θ of the IDT electrode in the fifth embodiment of the present invention. C_prop |A diagram showing the relationship between the thickness of the electrode fingers.

[0035] Fig. 22 It is a schematic front cross-sectional view of an elastic wave device according to a sixth embodiment of the present invention.

[0036] Fig.23 is an absolute value of the excitation angle |θ in the excitation portion of the IDT electrode covered with the dielectric film in the sixth embodiment of the present invention. C_prop |A graph showing the relationship between and the thickness of the dielectric film.

[0037] Fig.24 is an absolute value of the excitation angle |θ in the excitation portion of the IDT electrode covered with the dielectric film in the modification of the sixth embodiment of the present invention. C_prop |A graph showing the relationship between and the thickness of the dielectric film.

[0038] Fig.25 It is a schematic plan view showing the vicinity of the gap on the first bus bar side of the IDT electrode in the seventh embodiment of the present invention.

[0039] Fig.26 This is a schematic plan view showing the vicinity of the gap on the first bus bar side of the IDT electrode in the first modification of the seventh embodiment of the present invention.

[0040] Fig. 27 This is a schematic plan view showing the vicinity of the gap on the first bus bar side of the IDT electrode in the second modification of the seventh embodiment of the present invention.

[0041] Fig.28 This is a circuit diagram of a filter device according to an eighth embodiment of the present invention.

[0042] Fig.29 It is a schematic top view of an elastic wave device according to a reference example.

[0043] Fig.30 It is a schematic top view of a filter device according to a ninth embodiment of the present invention.

[0044] Fig.31 It is a schematic plan view of a filter device according to a modified example of the ninth embodiment of the present invention.

[0045] Fig.32This is a schematic plan view showing an enlarged portion of an IDT electrode in a sixth modification of the first embodiment of the present invention.

[0046] Fig.33 It is a schematic front cross-sectional view of an elastic wave device according to a tenth embodiment of the present invention.

[0047] Fig.34 It is a schematic front cross-sectional view of an elastic wave device according to an eleventh embodiment of the present invention.

[0048] Fig.35 It is a schematic front cross-sectional view of an elastic wave device according to a first modified example of the eleventh embodiment of the present invention.

[0049] Fig.36 It is a schematic front cross-sectional view of an elastic wave device according to a second modified example of the eleventh embodiment of the present invention.

[0050] Fig.37 It is a schematic front cross-sectional view of an elastic wave device according to a third modified example of the eleventh embodiment of the present invention. DETAILED DESCRIPTION

[0051] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention will be clarified.

[0052] In addition, it should be noted that each embodiment described in this specification is an example, and some structures can be replaced or combined among different embodiments.

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

[0054] 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. Specifically, 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 an intermediate layer 5. The intermediate 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 intermediate layer 5 may also be a single-layer dielectric film. Alternatively, the piezoelectric substrate 2 may also be a substrate including only the piezoelectric layer 6.

[0055] like Figure 1As 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 shape of the plurality of electrode fingers in a plan view only needs to include a curved portion, particularly a circular arc or an elliptical arc. The structure of the IDT electrode 8 will be described in detail below.

[0056] Back to Figure 1 In addition to the plurality of first electrode fingers 16 and the 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 opposed 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.

[0057] 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.

[0058] 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 face each other with a gap G2 therebetween. On the other hand, the top ends of the second electrode fingers 17 and the top ends of the first offset electrodes 18 face each other with a gap G1 therebetween.

[0059] In the following, the first electrode finger 16 and the second electrode finger 17 are sometimes simply described as electrode fingers. The first offset electrode 18 and the second offset electrode 19 are sometimes simply described as offset electrodes. The first bus bar 14 and the second bus bar 15 are sometimes simply described as bus bars. The pitch or duty ratio of the offset electrodes may be different from the electrode finger pitch or duty ratio of the IDT electrode 8 in the intersection region described later, for example.

[0060] Figure 3 It is a schematic plan view for explaining the structure of the IDT electrode in the first embodiment.

[0061] An imaginary line formed by connecting the top ends of the plurality of second electrode fingers is set as the first envelope E1, and an imaginary line formed by connecting the top ends of the plurality of first electrode fingers is set as the second envelope E2. The area between the first envelope E1 and the second envelope E2 is the intersection area D. More specifically, the area 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 E1, and the second envelope E2 is the intersection area D. Therefore, the first envelope E1 is equivalent to the end edge portion on the first bus bar 14 side of the intersection area D. The second envelope E2 is equivalent to the end edge portion on the second bus bar 15 side of the intersection area D. In the intersection area D, when viewed from the direction in which the first envelope E1 or the second envelope E2 extends, adjacent electrode fingers overlap each other.

[0062] The shapes of the plurality of electrode fingers in a plan view correspond to the shapes of the arcs of the plurality of concentric circles, respectively. Therefore, the centers of the circles including the arcs in the shapes of the plurality of electrode fingers coincide with each other.

[0063] When the ellipticity coefficient of a circle or ellipse of an arc in a shape including a 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 a plurality of electrode fingers is an ellipse, the ellipticity coefficient α2 / α1 becomes other than 1. α1 is equivalent 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 is equivalent 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. In addition, when r is set to an arbitrary constant, the formula for the ellipticity coefficient in the XY plane can be expressed as (x / α1) 2 +(y / α2) 2 =r 2 .

[0064] When the center of the circle including the arc in the shape of the plurality of electrode fingers is set as the fixed point C, in the present embodiment, the extension line of the first envelope E1 and the extension line of the second envelope E2 do not pass through the fixed point C. Therefore, the straight line passing through the fixed point C and the first envelope E1 is not parallel to the first envelope E1. Similarly, the straight line passing through the fixed point C and the second envelope E2 is not parallel to the second envelope E2.

[0065] A piezoelectric single crystal is used as a 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 the present embodiment, the straight line extending parallel to the propagation axis among the straight lines passing through the intersection region D and the fixed point C is the reference line N. However, the reference line N does not necessarily need to extend parallel to the propagation axis.

[0066] In addition, the propagation axis can be not only the direction of X propagation, but also a direction perpendicular to the direction of 90° X propagation or the direction of extension of the electrode fingers of the IDT electrode 8. The direction of extension of the electrode fingers mentioned here is the direction in which the tangent of each part of the electrode fingers extends. In addition, the direction of the excited elastic wave becomes a direction perpendicular to the direction in which the tangent of each part of the electrode fingers extends, or a direction connecting the shortest distance between adjacent electrode fingers, or a direction parallel to the electric field vector generated between the electrode fingers. The direction of extension of the electrode fingers mentioned here, specifically, is the direction in which the tangent of the curve connecting the parts of the electrode fingers extends. In addition, each part of the electrode finger can be represented by the center of gravity or a point in the middle of both ends. Figure 4 In the conventional elastic wave resonator shown, the excitation direction of the elastic wave is the same regardless of the definition. When the curve is an arc centered at the fixed point C, the direction of the excited elastic wave is represented by the direction perpendicular to the direction in which the tangent line of the curve connecting the electrode fingers extends.

[0067] The angle between the straight line passing through the fixed point C and the reference line N is set to θ C There are countless straight lines passing through the fixed point C, but 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.

[0068] 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 3 , a straight line M is shown as an example of the countless straight lines passing through the fixed point C and the intersection region D. For example, in the portion of the intersection region D located on the straight line M, elastic waves are excited. In the portions located on countless straight lines (not shown) passing through the fixed point C and the intersection region D, elastic waves are also excited. That is, the elastic wave device 1 has an excitation portion located on the straight line M and an excitation portion located on countless other straight lines (not shown).

[0069] The angle formed by the straight line passing through the fixed point C and the excitation part and the reference line N is the above-mentioned angle θ CIn addition, the angle formed by the excitation direction of the elastic wave at the intersection point of the straight line passing through the fixed point C and the excitation portion in the intersection region D and the first electrode finger 16 or the second electrode finger 17 and the reference line N is referred to as the excitation angle θ. C_prop In the excitation part through which the reference line N passes, the angle θ C and the excitation angle θ C_prop Between each excitation part, due to the excitation angle θ C_prop Different from each other, the propagation characteristics of the elastic waves are different from each other. In contrast, in the present embodiment, the duty ratios are set to be different between the multiple excitation parts so that the resonant frequencies or anti-resonant frequencies of all the excitation parts are substantially consistent with each other. In addition, the absolute value of the excitation angle |θ C_prop |The duty ratio is the same between the same excitation parts. Since the IDT electrode 8 is configured as described above, the resonance characteristics are unlikely to deteriorate. However, the duty ratio may be fixed.

[0070] Here, the angle θ in the excitation section C and the excitation angle θ C_prop Roughly the same. Below, the angle θ is used C and the excitation angle θ C_prop In addition, when the elliptic coefficient α2 / α1 is 1, that is, when the circle is formed, the angle θ C and the excitation angle θ C_prop become equal.

[0071] In this specification, the phrase "one frequency and another frequency are substantially consistent" means that the absolute value of the difference between the two frequencies is less than 2% relative to the reference frequency. C_prop The frequency when the angle of rotation is 0°. In the intersection region D, the absolute value of the difference between the highest resonant frequency and the lowest resonant frequency of the main mode is preferably less than 1% relative to the reference frequency. Alternatively, in the intersection region D, the absolute value of the difference between the highest anti-resonant frequency and the lowest anti-resonant frequency of the main mode is preferably less than 1% relative to the reference frequency.

[0072] 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 excitation angle θ. C_prop The electrode finger pitch is the distance between the centers of the adjacent first electrode fingers 16 and second electrode fingers 17. When the electrode finger pitch is denoted as p, λ=2p.

[0073] The angle θ formed by the end of the first envelope E1 on the fixed point C side and the straight line passing through the fixed point C and the reference line N isC Let the first inner cross angle θ be C_AP1_in The angle θ formed by the straight line passing through the end of the first envelope E1 on the side away from the fixed point C and the fixed point C and the reference line N is C Let the first outer intersection angle θ C_AP1_out The angle θ formed by the end of the second envelope E2 on the fixed point C side and the straight line passing through the fixed point C and the reference line N is C Let the second inner crossing angle θ be C_AP2_in The angle θ formed by the straight line passing through the end of the second envelope E2 on the side away from the fixed point C and the fixed point C and the reference line N is C Let the second outer intersection angle θ be C_AP2_out As described above, in this embodiment, the straight line connecting the fixed point C and the tip of the second electrode finger 17 is not parallel to the first envelope E1. C_AP1_in ≠θ C_AP1_out Similarly, the straight line connecting the fixed point C and the tip of the first electrode finger 16 is not parallel to the second envelope E2. C_AP2_in ≠θ C_AP2_out .

[0074] In addition, in the IDT electrode 8, the first envelope E1 and the first bus bar 14 extend in parallel. Similarly, the second envelope E2 and the second bus bar 15 extend in parallel. When the angle formed by the reference line N and the bus bar is set as the bus bar inclination angle, the bus bar inclination angles of the first bus bar 14 and the second bus bar 15 are the same. However, the bus bar inclination angles of the first bus bar 14 and the second bus bar 15 may be different from each other. In this specification, the positive direction of the bus bar inclination angle is set to the counterclockwise direction when viewed from above.

[0075] like Figure 1As shown, a pair of reflectors 9A and reflectors 9B are provided on the piezoelectric layer 6. Reflectors 9A and reflectors 9B are opposed to each other with the IDT electrode 8 sandwiched therebetween in the direction in which the plurality of electrode fingers of the IDT electrode 8 are arranged. Reflector 9A has a plurality of electrode fingers 9a. Reflector 9B has a plurality of electrode fingers 9b. The shapes of the plurality of electrode fingers 9a of reflector 9A and the shapes of the plurality of electrode fingers 9b of reflector 9B in a plan 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. In addition, the shape of the electrode fingers of each reflector may be a shape of a curve or a straight line different from the shape of the electrode fingers of the IDT electrode 8 in the excitation portion. The structural parameters such as the electrode finger pitch or the duty ratio of each reflector may also be different from the structural parameters of the electrode fingers of the IDT electrode 8 in the excitation portion. The electrode fingers of each reflector may also be composed of a pattern different from the shape of the electrode fingers of the IDT electrode 8 in the excitation portion.

[0076] The present embodiment is characterized in that the elastic wave device 1 has the following structure. 1) The shape of the plurality of electrode fingers in a plan view includes a circular arc or an elliptical arc. 2) The straight line connecting the fixed point C and the top end of the second electrode finger 17 is not parallel to the first envelope E1, and the straight line connecting the fixed point C and the top end of the first electrode finger 16 is not parallel to the second envelope E2. Accordingly, it is possible to fully suppress unnecessary waves and transverse modes outside the passband. In addition, in this specification, the so-called outside the passband in the elastic wave device refers to the low frequency side compared to the resonant frequency and the high frequency side compared to the anti-resonant frequency. By comparing the present embodiment and the comparative example, the details of the above-mentioned effect are shown below.

[0077] In the comparative example, Figure 4 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. In the first embodiment and the comparative example, the impedance frequency characteristics and the phase characteristics are compared. In addition, the design parameters of the elastic wave device 1 of the first embodiment are as follows. Here, the dimension of the offset electrode along the direction connecting the base end portion and the top end portion is set to the length of the offset electrode.

[0078] Support substrate 4: Material: Si, plane orientation: (111), ψ of the Euler angles (φ, θ, ψ): 73°

[0079] First layer 5a: material…SiN, thickness…0.15λ

[0080] Second layer 5b: material…SiO2, thickness…0.15λ

[0081] Piezoelectric layer 6: Material: LiTaO3 with rotation Y-cut 55° X-propagation, thickness: 0.2λ

[0082] IDT electrode 8: material…Al, thickness…0.05λ,

[0083] Number of pairs of electrode fingers of IDT electrode 8: 60 pairs

[0084] Ellipticity coefficient of electrode finger shape α2 / α1: 1

[0085] First inner crossing angle θ C_AP1_in : 11.1°

[0086] First outer crossing angle θ C_AP1_out :8.6°

[0087] Second inner crossing angle θ C_AP2_in : -6.2°

[0088] Second outer crossing angle θ C_AP2_out : -3.5°

[0089] Wavelength λ: 2μm

[0090] Duty cycle: At the excitation angle θ C_prop 0.5 in the excitation section at 0°

[0091] The bus bar inclination angle of the first bus bar 14 and the second bus bar 15 is 2.5°

[0092] Length of the first offset electrode 18 and the second offset electrode 19: 3.5λ

[0093] Reflector 9A and reflector 9B: Number of pairs of electrode fingers: 20 pairs

[0094] On the other hand, when the direction in which the plurality of electrode fingers extend is defined as the electrode finger extension direction and the dimension of the intersection region along the electrode finger extension direction is defined as the intersection width, the intersection width in the IDT electrode 108 of the elastic wave device of the comparative example is 41.5λ. The number of pairs of electrode fingers of the IDT electrode 108 is 60, and the number of pairs of electrode fingers of the reflector 109A and the reflector 109B are 20, respectively. In the IDT electrode 108, the duty ratio is 0.5.

[0095] Figure 5 It is a graph showing the impedance frequency characteristics in the first embodiment and the comparative example. Figure 6 It is a diagram showing the phase characteristics in the first embodiment and the comparative example.

[0096] like Figure 5As shown in FIG. 1 , in the comparative example, a plurality of ripples are generated between the resonant frequency and the anti-resonant frequency. These ripples are caused by the transverse mode. In contrast, it can be seen that in the first embodiment, the ripples caused by the transverse mode are suppressed. Figure 6 As shown, it can be seen that in the first embodiment, the unnecessary waves outside the passband are suppressed compared with the comparative example. Specifically, in the first embodiment, the unnecessary waves are suppressed on both the low frequency side of the resonant frequency and the high frequency side of the anti-resonant frequency. As described above, in the first embodiment, the unnecessary waves outside the passband can be suppressed, and the transverse mode can be suppressed.

[0097] In the present invention, the above-mentioned effects are obtained by utilizing the fact that propagation characteristics of elastic waves differ in the respective excitation parts. The details are described below.

[0098] The phase velocity of the elastic wave has a value corresponding to the excitation angle θ C_prop The dependence of the excitation angle θ on the substrate structure shows its inherent characteristics. In addition, the inverse of the phase velocity is equivalent to the inverse velocity surface. C_prop The relationship between the phase velocity and the piezoelectric substrate is roughly the same as the reverse velocity surface. Figure 7 An example of a reverse velocity surface of piezoelectric substrates with different layer structures is shown in FIG. One piezoelectric substrate is a substrate consisting only of LiTaO3 (LT) rotated Y-cut 42°X-propagated. 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 having a silicon substrate with a surface orientation of (100), a silicon oxide film, and a lithium tantalate layer stacked in sequence. Even if the surface orientation of the silicon substrate is other surface orientations such as (110) or (111), the concave and convex shape of the reverse velocity surface will not change.

[0099] Figure 7 It is a diagram showing the inverse velocity surface of the elastic wave propagating through the first piezoelectric substrate and the second piezoelectric substrate.

[0100] Figure 7 The x-axis shown corresponds to the result when it is parallel to the propagation axis. That is, it corresponds to the excitation angle θ C_prop The result when the angle of the first piezoelectric substrate and the second piezoelectric substrate are both linearly symmetrical with the x-axis as the axis of symmetry. 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, it can be seen that the elastic wave propagating in the substrate has a linear symmetry with respect to the excitation angle θ. C_prop The dependence of varies depending on the structure of the substrate. In addition, when the elastic wave mode is different, the excitation angle θ in the same substrate C_prop The dependencies are different. This is due to Figure 8 Shown.

[0101] Figure 8 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.

[0102] like Figure 8 As shown, the inverse velocity surfaces of the three elastic wave modes, namely the longitudinal wave, the fast shear wave and the slow shear wave, are different from each other. Figure 8 The portions passing through arrows L1 and L2 correspond to the excitation angles θ C_prop The example of the result when the angle is other than 0°. The interval between the slow shear wave and the fast shear wave in the portion passing through the arrow L1 is different from the interval between the slow shear wave and the fast shear wave in the portion passing through the arrow L2. Similarly, the interval between the fast shear wave and the longitudinal wave in the portion passing through the arrow L1 is different from the interval between the fast shear wave and the longitudinal wave in the portion passing through the arrow L2. That is, at the excitation angle θ C_prop In mutually different excitation parts, the intervals between the reverse velocity surfaces of different modes are different. This is also the case with the relationship between the main mode and the unnecessary wave used in the elastic wave device.

[0103] In this case, in the elastic wave device 1 of the first embodiment, the resonant frequencies of the main modes or the antiresonant frequencies are made substantially consistent in all the excitation parts. Therefore, the frequencies of the unnecessary waves in different excitation parts become different from each other. As a result, the unnecessary waves and transverse modes outside the passband are dispersed. Therefore, the unnecessary waves and transverse modes outside the passband can be suppressed.

[0104] In the first embodiment, since the resonant frequencies or anti-resonant frequencies in the excitation parts are substantially identical to each other, the main mode is appropriately excited, thereby suppressing degradation of the resonance characteristics.

[0105] Furthermore, in the first embodiment, the first inner crossing angle θ C_AP1_in and the first outer intersection angle θ C_AP1_out The second inner cross angle θ is different from each other. C_AP2_in and the second outer intersection angle θ C_AP2_out Therefore, among the electrode fingers, the excitation angle θ of the excitation portion including the electrode finger is C_prop The ranges are different from each other. For example, Figure 5 as well as Figure 6 In the elastic wave device 1 of the first embodiment according to the comparison, the excitation angle θ of the excitation portion including the electrode finger closest to the fixed point C among the plurality of electrode fingers is C_prop On the other hand, the excitation angle θ of the excitation portion including the electrode finger farthest from the fixed point C among the plurality of electrode fingers is C_propis greater than -3.5° and less than 8.6°. Similarly, the excitation angle θ of the excitation portion including each electrode finger is C_prop The ranges are different from each other.

[0106] As mentioned above, at the excitation angle θ C_prop The intervals between the reverse velocity surfaces of the main mode and the unnecessary wave are different in different excitation parts. However, in the first embodiment, the resonant frequency or antiresonant frequency of the main mode is substantially the same in all the excitation parts. In addition, in the first embodiment, the excitation angle θ of the excitation part including each electrode finger is C_prop The ranges of the frequencies of the unwanted waves excited are different from each other. Therefore, the range of the deviation of the frequency of the unwanted waves excited becomes different for each portion where each electrode finger is located. Therefore, the unwanted waves can be effectively dispersed. Therefore, the unwanted waves and transverse modes outside the passband can be effectively suppressed.

[0107] The following describes in more detail the case where the resonant frequencies of the main modes are made substantially consistent. As described above, the phase velocity is equivalent to the inverse of the inverse velocity surface. Therefore, the excitation angle θ C_prop The relationship between the phase velocity and Figure 8 The inverse velocity surface in the XY plane of the piezoelectric substrate shown in FIG. 1 is approximately 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 constant with respect to the excitation angle θ. C_prop dependency.

[0108] However, if the electrode fingers are simply shaped into a curve, the impedance frequency characteristic becomes C_prop The impedance frequency characteristic is formed by overlapping 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 excitation angle θ C_prop The excitation angle θ C_prop The frequencies of the elastic waves excited in the circuit are roughly consistent. Therefore, in each excitation unit, the resonant frequencies can be roughly consistent with each other. In addition, in each excitation unit, the anti-resonant frequencies can also be roughly consistent with each other. Therefore, the impedance frequency characteristic is formed in which the resonant frequency or the anti-resonant frequency is roughly consistent.

[0109] Depend on Fig. 9 The excitation angle θ in the first embodiment is shown. C_prop In addition, examples in which the maximum value of the duty ratio is different from that of the first embodiment are also shown as first and second modified examples of the first embodiment.

[0110] Fig. 9is an absolute value of the excitation angle |θ of the IDT electrode in the first embodiment, the first modification, and the second modification. C_prop |A graph showing the relationship between Ω and duty cycle.

[0111] In the first embodiment, at the excitation angle θ C_prop When the excitation angle θ is 0°, the duty ratio is set to the maximum value. That is, in the first embodiment, the straight line passing through the excitation part with the largest duty ratio among all the excitation parts and the fixed point C is the reference line N. In the first embodiment, C_prop When the excitation angle is 0°, the duty cycle is 0.5. C_prop The larger | is, the smaller the duty ratio is. Thus, in all the excitation parts, the resonant frequencies or anti-resonant frequencies are substantially consistent with each other.

[0112] In the first and second modified examples, the absolute value of the excitation angle |θ C_prop | is larger, the duty ratio is smaller. In the first modification, at the excitation angle θ C_prop When the excitation angle θ is 0°, the duty ratio is 0.64. C_prop When the duty ratio is 0°, the duty ratio is 0.425. In the first variant and the second variant, the resonant frequencies or anti-resonant frequencies in all the excitation parts are roughly consistent with each other. Moreover, in the first variant and the second variant, the configuration is the same as the first embodiment in terms of aspects other than the duty ratio. Therefore, it is possible to suppress unnecessary waves and transverse modes outside the passband.

[0113] When forming the IDT electrode 8, for example, semiconductor photolithography is used. When using semiconductor photolithography to form a resist and metal wiring pattern, if the duty ratio is less than 0.2 or greater than 0.8, pattern formation becomes difficult, and stable pattern processing with small deviation becomes difficult. Fig. 9 , excitation angle θ C_prop The larger the duty cycle when the excitation angle is 0°, the greater the absolute value of the excitation angle |θ C_prop | becomes larger. That is, θ C_prop The larger the duty ratio when it is 0°, the greater the absolute value of the excitation angle |θ C_prop |The larger the curve pattern. For the absolute value of the excitation angle |θ C_prop | The curve pattern in a larger range can further improve the effect of suppressing unnecessary waves. Therefore, the duty ratio of the electrode fingers of the IDT electrode 8 is preferably set in the range of 0.2 to 0.8, and more preferably in the range of 0.25 to 0.75. In addition, regarding the excitation angle θ C_propThe duty ratio at 0° is preferably set to 0.5 rather than 0.425, and more preferably set to 0.64 rather than 0.5.

[0114] In addition, the relationship between the duty ratio and the frequency of each mode varies depending on the reverse velocity surface of the piezoelectric substrate. Therefore, depending on the structure of the piezoelectric substrate and the structure on the piezoelectric substrate, the absolute value of the excitation angle |θ C_prop | When the duty ratio increases, the resonant frequencies or anti-resonant frequencies of all the excitation parts may be roughly the same. In this case, the straight line passing through the excitation part with the smallest duty ratio among all the excitation parts 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 rotates Y-cut -4°X propagates is embedded in a thick SiO2 film can be cited. Alternatively, the excitation angle θ passing through the reference line N C_prop In the excitation portion at 0°, the duty ratio is not necessarily the maximum or minimum.

[0115] exist Figure 1 In the first embodiment shown in FIG. 1 , the first envelope E1 and the second envelope E2 are inclined relative to the direction in which the reference line N extends. However, the present invention is not limited to this. Fig.10 In the IDT electrode 8A in the third modification of the first embodiment shown, the first envelope E1 and the second envelope E2 extend parallel to the reference line N. Furthermore, the inclination angles of the first bus bar and the second bus bar are both 0°.

[0116] However, it is preferred that Figure 1 As shown in the first embodiment, the first bus bar 14 and the second bus bar 15 are inclined with respect to the reference line N. This can effectively suppress the lateral mode. Figure 4 The comparative example shown hereby illustrates this.

[0117] In addition, the design parameters of the elastic wave devices of the first embodiment and the comparative example are set to Figure 5 as well as Figure 6 The same is true for the comparison in . The design parameters of the elastic wave device of the third modification example are the same as the design parameters of the elastic wave device 1 of the first embodiment except for the following points.

[0118] First inner crossing angle θ C_AP1_in : 8.5°

[0119] First outer crossing angle θ C_AP1_out : 6°

[0120] Second inner crossing angle θ C_AP2_in : -8.5°

[0121] Second outer crossing angle θ C_AP2_out : -6°

[0122] Bus bar inclination angle of the 1st bus bar and the 2nd bus bar: 0°

[0123] Fig.11 It is a diagram showing phase characteristics in the vicinity of the resonance frequency in the first embodiment, the third modification example, and the comparative example.

[0124] like Fig.11 As shown, in the comparative example, large ripples caused by the transverse mode are generated near 1950MHz to 2010MHz. In contrast, in the third variant, the ripples caused by the transverse mode become smaller. And it can be seen that in the first embodiment, the ripples caused by the transverse mode are suppressed compared to the third variant. In this way, the transverse mode can be effectively suppressed by tilting the first bus bar and the second bus bar relative to the reference line N. In more detail, this is because, in the first embodiment, the first bus bar and the second bus bar are tilted relative to the reference line N, and the first inner cross angle θ is set to C_AP1_in and the second inner crossing angle θ C_AP2_in Also, the first outer cross angle θ is different from each other. C_AP1_out and the second outer intersection angle θ C_AP2_out Different from each other.

[0125] Fig.12 It is a diagram showing the phase characteristics on the lower frequency side than the resonance frequency in the first embodiment, the third modification example, and the comparative example. Fig.13 It is a diagram showing phase characteristics on the high frequency side compared to the antiresonance frequency in the first embodiment, the third modification example, and the comparative example.

[0126] like Fig.12 As shown in FIG. 1 , it can be seen that in the first embodiment and the third modification example, the unnecessary waves on the lower frequency side than the resonance frequency can be suppressed compared to the comparative example. Fig.13 As shown, it can be seen that in the first embodiment and the third modification, the unnecessary waves on the high frequency side compared to the antiresonance frequency can be suppressed compared to the comparative example. As described above, in the third modification, the unnecessary waves and transverse modes outside the passband can be suppressed as in the first embodiment.

[0127] Back to Figure 1In the first embodiment, the shapes of the plurality of first offset electrodes 18 and the shapes of the plurality of second offset electrodes 19 are shapes corresponding 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 first offset electrodes 18 and the plurality of second offset electrodes 19 coincides with the fixed point C. However, in the case where the shapes of the plurality of electrode fingers in a plan view are in the shape of an elliptical arc, the shapes of the plurality of first offset electrodes 18 and the plurality of second offset electrodes 19 may be in the shape of an elliptical arc included in an ellipse having a focus with the fixed point C as the midpoint. In addition, the center of two foci is the centroid of the two foci, and is the centroid of the ellipse having the two foci. Therefore, in the case where the shapes of the electrode fingers and the offset electrodes of the IDT electrode in a plan view are in the shape of an elliptical arc, the fixed point C is the centroid of the ellipse including the above-mentioned elliptical arc.

[0128] In the IDT electrode 8, the duty ratio changes in the region between the intersection region D and the first bus bar 14 and the region between the intersection region D and the second bus bar 15, similarly to the intersection region D. Therefore, the duty ratio of the portion including the first offset electrode 18 on the extension line of any excitation portion and the excitation portion is constant. Similarly, the duty ratio of the portion including the second offset electrode 19 on the extension line of any excitation portion and the excitation portion is constant.

[0129] However, if we focus on the area between the first bus bar 14 and the intersection area D, in the first embodiment, the duty ratio in this area increases as it is closer to the first bus bar 14. Similarly, in the area between the second bus bar 15 and the intersection area, the duty ratio increases as it is closer to the second bus bar 15.

[0130] In addition, the shapes of the plurality of first offset electrodes 18 and the plurality of second offset electrodes 19 are not limited to the above. For example, in the area between the first bus bar 14 and the intersection area D, the duty cycle may be smaller as it is closer to the first bus bar 14. In the area between the second bus bar 15 and the intersection area D, the duty cycle may be smaller as it is closer to the second bus bar 15. Alternatively, the offset electrodes may not necessarily be provided. In this case, in the present invention, useless waves can also be suppressed. Furthermore, the shapes of the first electrode fingers 16 and the second electrode fingers 17 are not particularly limited in areas other than the intersection area D.

[0131] As described above, the top end portion of the second electrode finger 17 and the top end portion of the first offset electrode 18 are opposed to each other with the gap G1 therebetween. The size of the gap G1 is the distance between the top end portion of the second electrode finger 17 and the top end portion of the first offset electrode 18. Similarly, the size of the gap G2 is the distance between the top end portion of the first electrode finger 16 and the top end portion of the second offset electrode 19. The sizes of the gap G1 and the gap G2 are preferably less than 1λ, and more preferably less than 0.5λ. If the gap G1 is larger than 0.5λ, there is a tendency for the elastic wave to become easier to leak in the direction from the intersection area D toward the first bus bar 14. The same is true when the gap G2 is larger than 0.5λ. If the sizes of the gap G1 and the gap G2 exceed 1λ, the amount of main mode leakage increases, and sometimes the loss cannot be ignored.

[0132] In addition, the length of the first offset electrode 18 and the second offset electrode 19 is preferably 1λ or more, and more preferably 1.3λ or more. If the length of the first offset electrode 18 is shorter than 1.3λ, there is a tendency that the elastic wave becomes easy to leak in the direction from the intersection area D toward the first bus bar 14. The same is true when the length of the second offset electrode 19 is shorter than 1.3λ. If the length of the first offset electrode 18 and the second offset electrode 19 is shorter than 1λ, the amount of main mode leakage increases, and the loss may become non-negligible.

[0133] In addition, if Figure 2 As 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 an intermediate 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.

[0134] In the first embodiment, the high-acoustic-velocity film, the low-acoustic-velocity film, and the piezoelectric layer 6 are sequentially stacked on the piezoelectric substrate 2. This allows the energy of the elastic wave to be effectively confined in the piezoelectric layer 6.

[0135] As materials for the high acoustic velocity membrane, for example, silicon, aluminum oxide, silicon carbide, silicon nitride, silicon oxynitride, sapphire, lithium tantalate, lithium niobate, quartz, alumina, zirconium oxide, cordierite, mullite, steatite, forsterite, magnesium oxide, DLC (diamond-like carbon) film, diamond, spinel or sialon, etc., and media with the above materials as the main components can be used.

[0136] 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.

[0137] 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.

[0138] 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 with the above materials as the main component can also be used. In addition, the above-mentioned spinel includes aluminum compounds containing one or more elements selected from Mg, Fe, Zn, Mn, etc. and oxygen. Examples of the spinel listed as examples of the materials of the support substrate 4 and the high acoustic velocity film mentioned above include MgAl2O4, FeAl2O4, ZnAl2O4, and MnAl2O4. As the material of the support substrate 4, silicon is preferably used.

[0139] 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.

[0140] In addition, the relationship between the acoustic velocities in the first layer 5a and the second layer 5b in the intermediate layer 5 is not limited to the above. Furthermore, the layer structure of the piezoelectric substrate 2 is not limited to the above. Hereinafter, the fourth and fifth variants of the first embodiment are shown, in which only the structure of the piezoelectric substrate 2 is different from that of the first embodiment. In the fourth and fifth variants, as in the first embodiment, it is possible to suppress unnecessary waves and transverse modes outside the passband. Furthermore, it is possible to effectively confine the energy of the elastic wave on the piezoelectric layer 6 side.

[0141] exist Fig.14 In the fourth variation shown, the piezoelectric substrate 2A includes a support substrate 4, an acoustic reflection film 7, an intermediate layer 5A, and a piezoelectric layer 6. The acoustic reflection film 7 is provided on the support substrate 4. The intermediate layer 5A is provided on the acoustic reflection film 7. The piezoelectric layer 6 is provided on the intermediate layer 5A. The intermediate layer 5A is a low acoustic velocity film.

[0142] 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.

[0143] 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.

[0144] 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 intermediate layer 5A can also be the same as that of the low acoustic impedance layer.

[0145] exist Fig.15 In the fifth variation 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.

[0146] In the first embodiment, the duty ratio is adjusted according to the excitation angle θ. C_prop However, it is not limited to the duty ratio, and the 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 excitation angle θ. C_prop 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 excitation angle θ. C_prop It is also possible to make multiple parameters among the above parameters change according to the excitation angle θ C_prop In these cases, the resonant frequencies or anti-resonant frequencies can be made substantially consistent with each other in all the excitation parts.

[0147] In the first embodiment, the shapes of the first electrode finger 16 and the second electrode finger 17 are all curved. This can further suppress unnecessary waves. However, the shapes of the first electrode finger 16 and the second electrode finger 17 may not all be curved. The first electrode finger 16 and the second electrode finger 17 may also include a portion that is a linear shape.

[0148] However, it is particularly preferred that the shapes of the first electrode finger 16 and the second electrode finger 17 in a plan view are circular arc shapes as in the first embodiment. Alternatively, it is particularly preferred that the shapes of the first electrode finger 16 and the second electrode finger 17 in a plan view are elliptical arc shapes. In these cases, unnecessary waves and transverse modes outside the passband can be further effectively suppressed.

[0149] In addition, the duty ratio including the offset electrode located on the extension line of the excitation unit, the center-to-center distance between the offset electrode and the electrode finger, and the thickness of the offset electrode may also be adjusted according to the excitation angle θ of the excitation unit. C_prop And it changes in the same way as the parameters of the electrode fingers.

[0150] The following describes how to adjust parameters other than the duty ratio according to the excitation angle θ. C_prop In 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.16 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 when viewed from above are elliptical arc shapes. In this case, the shapes of the plurality of electrode fingers when viewed from above are shapes of elliptical arcs corresponding to a plurality of ellipses whose centers of gravity are at the same position. Fig.17 As shown, the midpoint between focus A and focus B is the centroid. And, the centroid is fixed point C. In this embodiment, regarding the ellipticity coefficient α2 / α1 of the shape of the plurality of electrode fingers in a plan view, α2 / α1<1. More specifically, α2 / α1=0.72. However, the ellipticity coefficient α2 / α1 is not limited to the above.

[0154] In this embodiment, similarly to the first embodiment, the straight line connecting the fixed point C and the tip of the second electrode finger is not parallel to the first envelope E1. C_AP1_in ≠θ C_AP1_out Moreover, the straight line connecting the fixed point C and the tip of the first electrode finger is not parallel to the second envelope E2. C_AP2_in ≠θ C_AP2_out . According to this, it is possible to suppress unnecessary waves and transverse modes outside the passband.

[0155] As described above, the duty ratio is fixed in the IDT electrode 28. Specifically, the duty ratio is 0.5. In this embodiment, the reference line N is a straight line passing through the excitation portion having the widest electrode finger pitch among all the excitation portions. Furthermore, the absolute value of the excitation angle |θ C_prop The larger the | is, the narrower the electrode finger pitch is. As a result, the resonant frequencies or anti-resonant frequencies are substantially consistent with each other in all the excitation parts. The absolute value of the excitation angle |θ is specifically shown below. C_prop | and the electrode finger pitch. Here, the excitation angle θ C_prop The electrode finger pitch in the excitation portion at 0° is defined as p0, the electrode finger pitch in an arbitrary portion is defined as p1, and {(p1-p0) / p0}×100[%] is defined as the electrode finger pitch change rate Δpitch[%].

[0156] Fig.18 is an absolute value of the excitation angle |θ of the IDT electrode in the second embodiment. C_prop |A graph showing the relationship between Δpitch and the rate of change of the electrode finger pitch.

[0157] like Fig.18 As shown, in this embodiment, the excitation angle θ in the IDT electrode 28 is C_prop In the excitation section with a value of 0°, Δpitch is 0%. C_prop |The larger the value, the more negative Δpitch becomes. That is, the absolute value of the excitation angle |θ C_prop |The larger it is, the narrower the electrode finger spacing is.

[0158] In this embodiment, as in the first embodiment, the straight line connecting the fixed point C and the tip of the second electrode finger is not parallel to the first envelope E1. C_AP1_in ≠θ C_AP1_out . Moreover, the straight line connecting the fixed point C and the top of the first electrode finger is not parallel to the second envelope E2. In other words, the straight line passing through the fixed point C and the first envelope E1 is not parallel to the first envelope E1, and the straight line passing through the fixed point C and the second envelope E2 is not parallel to the second envelope E2. Accordingly, it is possible to suppress unnecessary waves and transverse modes outside the passband.

[0159] Furthermore, an example of design parameters of the elastic wave device according to the present embodiment is shown below.

[0160] Ellipticity coefficient of electrode finger shape α2 / α1: 0.72

[0161] First inner crossing angle θ C_AP1_in : 9.6°

[0162] First outer crossing angle θ C_AP1_out : 7.5°

[0163] Second inner crossing angle θ C_AP2_in : -8.2°

[0164] Second outer crossing angle θ C_AP2_out : -5°

[0165] The longest wavelength λ: 2μm

[0166] Electrode finger spacing: at excitation angle θ C_prop 1μm in the excitation part at 0°

[0167] Duty cycle: 0.5

[0168] The bus bar inclination angle of the first bus bar 14 and the second bus bar 15 is 2.5°

[0169] Length of the first offset electrode and the second offset electrode: 3.5λ

[0170] In addition, the relationship between the electrode finger pitch and the frequency of each mode varies depending on the reciprocal velocity surface of the piezoelectric substrate. Therefore, depending on the structure of the piezoelectric substrate and the structure on the piezoelectric substrate, the absolute value of the excitation angle |θ C_prop | When the electrode finger pitch is wider, the resonant frequencies or anti-resonant frequencies of all the excitation parts may be roughly the same. In this case, the straight line passing through the excitation part with the narrowest electrode finger pitch among all the excitation parts 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 rotates Y-cut -4°X propagates is buried in a thick SiO2 film can be cited. Alternatively, the excitation angle θ passing through the reference line N C_prop In the excitation portion with an angle of 0°, the value of the electrode finger pitch is not necessarily the maximum or the minimum.

[0171] Fig.19 It is a schematic plan view of an elastic wave device according to a third embodiment.

[0172] The present embodiment differs from the first embodiment in that the electrode finger pitch in the IDT electrode 38 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 straight line passing through the excitation part with the narrowest electrode finger pitch among all the excitation parts and the fixed point C is the reference line N. At the same time, the straight line passing through the excitation part with the largest duty ratio among all the excitation parts and the fixed point C is the reference line N. The absolute value of the excitation angle |θ C_prop The larger the |, the wider the electrode finger spacing. Moreover, the absolute value of the excitation angle |θ C_prop | is larger, the duty cycle is smaller. Accordingly, in all the excitation parts, the resonant frequencies or anti-resonant frequencies are roughly consistent with each other. In this embodiment, as in the first embodiment, the straight line passing through the fixed point C and the first envelope E1 is not parallel to the first envelope E1, and the straight line passing through the fixed point C and the second envelope E2 is not parallel to the second envelope E2. Accordingly, it is possible to suppress unnecessary waves and transverse modes outside the passband.

[0174] In the IDT electrode 38, the elliptic coefficient α2 / α1 in the shape of the plurality of electrode fingers is greater than 1. Accordingly, the response at the upper end of the stopband can be suppressed, and the value of the fractional stopband width can be increased. The details are described below. In addition, the so-called stopband is a region where the wavelength of the elastic wave becomes fixed by enclosing the elastic wave in a periodically structured metal grating. The so-called fractional stopband width is a value obtained by dividing the bandwidth of the stopband by the resonant frequency. The so-called upper end of the stopband is the end of the high-frequency side of the stopband. The bandwidth of the stopband is the difference between the frequency at the upper end of the stopband and the resonant frequency.

[0175] When the elliptic coefficient α2 / α1 is greater than 1, the frequency at the upper end of the stopband is dispersed. As a result, the response of the frequency at the upper end of the stopband can be suppressed. Moreover, the dimension of the intersection region along the direction in which the first bus bar 14 and the second bus bar 15 are opposite to each other becomes larger than the dimension of the intersection region along the direction orthogonal to the direction. Therefore, the curvature in the shape of the plurality of electrode fingers in a top view becomes close to 0. In this case, the bandwidth of the stopband becomes wider. Therefore, the value of the fractional stopband width can be increased.

[0176] Furthermore, in this embodiment, the fractional bandwidth can be increased compared to the case where the frequencies of the excitation parts are substantially matched with each other only by the duty ratio. When the resonant frequency is fr and the antiresonant frequency is fa, the fractional bandwidth is represented by |fa-fr| / fr.

[0177] An example of design parameters of the elastic wave device according to the present embodiment is shown below.

[0178] Number of pairs of IDT electrode fingers: 60 pairs

[0179] Ellipticity coefficient of electrode finger shape α2 / α1: 1.1

[0180] First inner crossing angle θ C_AP1_in : 11.8°

[0181] First outer crossing angle θ C_AP1_out :9.1°

[0182] Second inner crossing angle θ C_AP2_in : -6.1°

[0183] Second outer crossing angle θ C_AP2_out : -3.5°

[0184] Duty cycle: At the excitation angle θ C_prop 0.5 in the excitation section at 0°

[0185] The bus bar inclination angle of the first bus bar 14 and the second bus bar 15 is 2.5°

[0186] Length of the first offset electrode and the second offset electrode: 3.5λ

[0187] Number of electrode fingers of reflector: 20 pairs

[0188] Fig. 20 It is a schematic plan view of an elastic wave device according to a fourth embodiment.

[0189] 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 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.

[0190] More specifically, in this embodiment, the straight line passing through the excitation part with the widest electrode finger pitch among all the excitation parts and the fixed point C is the reference line N. At the same time, the straight line passing through the excitation part with the largest duty ratio among all the excitation parts and the fixed point C is the reference line N. The absolute value of the excitation angle |θ C_prop The larger the |, the narrower the electrode finger pitch. Moreover, the absolute value of the excitation angle |θ C_prop| is larger, the duty cycle is smaller. Accordingly, in all the excitation parts, the resonant frequencies or anti-resonant frequencies are roughly consistent with each other. In this embodiment, as in the first embodiment, the straight line passing through the fixed point C and the first envelope E1 is not parallel to the first envelope E1, and the straight line passing through the fixed point C and the second envelope E2 is not parallel to the second envelope E2. Accordingly, it is possible to suppress unnecessary waves and transverse modes outside the passband.

[0191] In the IDT electrode 48 , the ellipticity α2 / α1 of the shape of the plurality of electrode fingers in plan view is smaller than 1. This can suppress the response at the upper end of the stopband and increase the value of the fractional stopband width. The details are described below.

[0192] When the elliptic coefficient α2 / α1 is less than 1, the frequency at the upper end of the stop band is dispersed. Accordingly, the response of the frequency at the upper end of the stop band can be suppressed. Moreover, the dimension of the intersection region along the direction in which the first bus bar 14 and the second bus bar 15 are opposite to each other becomes smaller than the dimension of the intersection region along the direction orthogonal to the direction. Therefore, compared with the case where the shape of the plurality of electrode fingers when viewed from above is an arc shape, the curvature becomes larger. In this case, the interval between the frequency of the main mode and the frequency of the useless wave is widened. Therefore, the useless wave can be effectively suppressed. On the basis of the above-mentioned structure, the frequencies of the respective excitation units are made substantially consistent with each other by both the duty cycle and the electrode finger spacing. Thus, the useless wave can be suppressed compared with the case where the frequencies of the respective excitation units are made substantially consistent with each other only by the duty cycle.

[0193] Furthermore, in the present embodiment, the value of the fractional bandwidth can be reduced compared to a case where the frequencies of the respective excitation parts are made substantially consistent with each other simply by the duty ratio.

[0194] An example of design parameters of the elastic wave device according to the present embodiment is shown below.

[0195] Number of pairs of IDT electrode fingers: 60 pairs

[0196] Ellipticity coefficient of electrode finger shape α2 / α1: 0.9

[0197] First inner crossing angle θ C_AP1_in : 10.8°

[0198] First outer crossing angle θ C_AP1_out :8.1°

[0199] Second inner crossing angle θ C_AP2_in : -7.5°

[0200] Second outer crossing angle θ C_AP2_out : -4.1°

[0201] Duty cycle: At the excitation angle θ C_prop 0.5 in the excitation section at 0°

[0202] The bus bar inclination angle of the first bus bar 14 and the second bus bar 15 is 2.5°

[0203] Length of the first offset electrode and the second offset electrode: 3.5λ

[0204] Number of electrode fingers of reflector: 20 pairs

[0205] In the first to fourth embodiments, the duty ratio or the electrode finger pitch is adjusted so that the resonant frequencies or anti-resonant frequencies in all the excitation parts are roughly consistent with each other. However, the thickness of the plurality of electrode fingers may be adjusted so that the resonant frequencies or anti-resonant frequencies in all the excitation parts are roughly consistent with each other. This example is shown in the fifth embodiment.

[0206] The fifth 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.

[0207] Fig.21 is an absolute value of the excitation angle |θ of the IDT electrode in the fifth embodiment. C_prop |A diagram showing the relationship between the thickness of the electrode fingers.

[0208] In the fifth embodiment, a straight line passing through the excitation portion having the thickest first electrode finger and second electrode finger among all the excitation portions and the fixed point C is the reference line N. Fig.21 As shown, the absolute value of the excitation angle in the IDT electrode |θ C_prop | is larger, the thickness of the first electrode finger and the second electrode finger is thinner. Accordingly, the resonant frequencies in all the excitation parts are substantially consistent with each other. Similarly, the anti-resonant frequencies in all the excitation parts can also be made substantially consistent with each other.

[0209] Furthermore, in the fifth embodiment, similarly to the first embodiment, the straight line passing through the fixed point C and the first envelope E1 is not parallel to the first envelope E1, and the straight line passing through the fixed point C and the second envelope E2 is not parallel to the second envelope E2. Thus, unnecessary waves and transverse modes outside the passband can be suppressed.

[0210] In addition, the relationship between the thickness of the first electrode finger and the second electrode finger and the frequency of each mode is different depending on the reverse velocity surface of the piezoelectric substrate. Therefore, depending on the structure of the piezoelectric substrate and the structure on the piezoelectric substrate, the absolute value of the excitation angle |θ C_prop| When the thickness of the first electrode finger and the second electrode finger is thicker, the resonant frequencies or anti-resonant frequencies of all the excitation parts may be roughly the same. In this case, the straight line passing through the excitation part with the thinnest thickness of the first electrode finger and the second electrode finger among all the excitation parts and the fixed point C is the reference line N. As an example of this, an elastic wave device in which an IDT electrode provided on a substrate including only LiNbO3 that rotates Y-cut -4°X propagates is buried in a thick SiO2 film can be cited. Alternatively, the excitation angle θ passing through the reference line N C_prop In the excitation portion at 0°, the thickness values ​​of the first electrode fingers and the second electrode fingers are not necessarily the maximum or the minimum.

[0211] In the first to fifth embodiments, the resonant frequencies or anti-resonant frequencies in all the excitation parts are made substantially consistent with each other by the structure of the IDT electrode. However, the resonant frequencies or anti-resonant frequencies in all the excitation parts may be made substantially consistent with each other by adjusting the thickness of the dielectric film covering the IDT electrode. This example is shown in the sixth embodiment and its modified example.

[0212] Fig. 22 : is a schematic front cross-sectional view of an elastic wave device according to the sixth embodiment. Fig. 22 is a schematic cross-sectional view along reference line N.

[0213] The present embodiment differs from the first embodiment in that the duty ratio is fixed in the IDT electrode 58. The present embodiment also differs from the first embodiment in that a dielectric film 55 is provided on the piezoelectric layer 6 so as to cover the IDT electrode 58. 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.

[0214] The acoustic velocity of the transverse wave propagating through the dielectric film 55 of this embodiment is lower than the acoustic velocity of the main mode propagating through the dielectric film 55. The thickness of the dielectric film 55 is determined by the excitation angle θ of the excitation portion of the IDT electrode 58 covered by the dielectric film 55. C_prop But different.

[0215] Fig.23 is an absolute value of the excitation angle |θ in the excitation portion of the IDT electrode covered with the dielectric film in the sixth embodiment. C_prop |A graph showing the relationship between and the thickness of the dielectric film.

[0216] In this embodiment, a straight line passing through the excitation portion where the thickest portion of the dielectric film 55 is located among all the excitation portions and the fixed point C is the reference line N. Fig.23 As shown, in this embodiment, the absolute value of the excitation angle |θ in the excitation portion of the IDT electrode 58 covered by the dielectric film 55 isC_prop The larger | is, the thinner the dielectric film 55 is. Thus, the resonant frequencies or anti-resonant frequencies in all the excitation parts are substantially identical to each other.

[0217] In this embodiment, as in the first embodiment, the straight line passing through the fixed point C and the first envelope E1 is not parallel to the first envelope E1, and the straight line passing through the fixed point C and the second envelope E2 is not parallel to the second envelope E2. This can suppress unnecessary waves and transverse modes outside the passband.

[0218] In the sixth embodiment, the acoustic velocity of the transverse wave propagating in the dielectric film 55 is lower than the acoustic velocity of the main mode propagating in the dielectric film 55. 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 sixth embodiment in which the acoustic velocity of the transverse wave propagating in the dielectric film is different from that of the sixth embodiment is shown below.

[0219] In the modified example of the sixth 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 addition, in this modified example, the absolute value of the excitation angle in the excitation portion of the IDT electrode covered by the dielectric film |θ C_prop | and the thickness of the dielectric film are related as follows Fig.24 More specifically, in this modification, a straight line passing through the excitation portion where the thickness of the dielectric film is the thinnest among all the excitation portions and the fixed point C is the reference line N. The absolute value of the excitation angle in the excitation portion of the IDT electrode covered by the dielectric film |θ C_prop |The larger the value, the thicker the dielectric film. Thus, the resonant frequencies or anti-resonant frequencies in all the excitation parts are substantially consistent with each other. Moreover, in this modification, as in the sixth embodiment, it is possible to suppress unnecessary waves and transverse modes outside the passband.

[0220] In addition, depending on the structure of the piezoelectric substrate and the like, the thickness of the portion of the dielectric film covering the excitation portion may not necessarily be the largest or smallest value at the portion through which the reference line N passes.

[0221] Fig.25 It is a schematic plan view showing the vicinity of the gap on the first bus bar side of the IDT electrode in the seventh embodiment.

[0222] The present embodiment is different from the first embodiment in that at least parameters other than the duty ratio are adjusted according to the excitation angle θ. C_propAnd change, so that the resonant frequencies or anti-resonant frequencies in all the excitation parts are roughly consistent with each other. The duty ratio in the portion where the top ends of the plurality of first electrode fingers 66 are arranged is fixed. Similarly, the duty ratio in the portion where the top ends of the plurality of second electrode fingers 67 are arranged is fixed. This embodiment also differs from the first embodiment in the structure of the area between the intersection area and the first bus bar 14, and the area between the intersection area and the second bus bar. Except for the above aspects, the elastic wave device of this embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0223] The width of the plurality of first offset electrodes 68 is fixed. The width of the plurality of first electrode fingers 66 is also fixed in the region outside the intersection region. More specifically, the width of the plurality of first offset electrodes 68 is the same as the width of the top end portions of the plurality of second electrode fingers 67. Moreover, the width of the plurality of first electrode fingers 66 is the same as the width of the plurality of first offset electrodes 68 in the region outside the intersection region. In addition, the shape of the plurality of first offset electrodes 68 when viewed from above is curved. The shape of the plurality of first electrode fingers 66 in the region outside the intersection region when viewed from above is also curved. The duty ratio in the region between the intersection region and the first bus bar 14 is the same as the duty ratio in the portion where the top ends of the plurality of second electrode fingers 67 are arranged.

[0224] Although not shown in the figure, the width of the plurality of second offset electrodes is the same as the width of the top ends of the plurality of first electrode fingers 66 and is constant. The width of the plurality of second electrode fingers 67 is the same as the width of the plurality of second offset electrodes in the region outside the intersection region. The shape of the plurality of second offset electrodes when viewed from above is curved. The shape of the plurality of second electrode fingers 67 in the region outside the intersection region when viewed from above is also curved. The duty ratio in the region between the intersection region and the second bus bar is the same as the duty ratio in the portion where the top ends of the plurality of first electrode fingers 66 are arranged.

[0225] In the present embodiment, the widths of the plurality of first offset electrodes 68 and the plurality of first electrode fingers 66 do not become narrower in the intersection region and the region between the first bus bars 14. The widths of the plurality of second offset electrodes and the plurality of second electrode fingers 67 also do not become narrower in the intersection region and the region between the second bus bars. Thus, the series resistance can be reduced.

[0226] In this embodiment, as in the first embodiment, the straight line passing through the fixed point C and the first envelope E1 is not parallel to the first envelope E1, and the straight line passing through the fixed point C and the second envelope E2 is not parallel to the second envelope E2. This can suppress unnecessary waves and transverse modes outside the passband.

[0227] The following shows a first variant and a second variant of the seventh embodiment in which the structures of only the region between the intersection region and the first bus bar 14 and the region between the intersection region and the second bus bar are different from those of the seventh embodiment. In the first variant and the second variant, as in the seventh embodiment, unnecessary waves and transverse modes outside the passband can be suppressed and the series resistance can be reduced.

[0228] exist Fig.26 In the first modified example shown, the width of the plurality of first offset electrodes 68A is wider than the width of the top end portions of the plurality of second electrode fingers 67A. The width of the plurality of first electrode fingers 66A is the same as the width of the plurality of first offset electrodes 68A in the region outside the intersection region. Although not shown, the width of the plurality of second offset electrodes is wider than the width of the top end portions of the plurality of first electrode fingers 66A. The width of the plurality of second electrode fingers 67B is the same as the width of the plurality of second offset electrodes in the region outside the intersection region.

[0229] Therefore, in this variation, the duty ratio in the region between the intersection region and the first bus bar 14 is greater than the duty ratio in the portion where the top ends of the plurality of second electrode fingers 67A are arranged. Similarly, the duty ratio in the region between the intersection region and the second bus bar is greater than the duty ratio in the portion where the top ends of the plurality of first electrode fingers 66A are arranged.

[0230] exist Fig. 27 In the second modification shown, the first offset electrodes 68B and the second offset electrodes are linear in plan view. Similarly, in this modification, the first electrode fingers 66B and the second electrode fingers 67B are linear in plan view in the region outside the intersection region.

[0231] The elastic wave device according to the present invention can be used in, for example, a filter device. This example is shown below.

[0232] Fig.28 This is a circuit diagram of a filter device according to the eighth embodiment.

[0233] The filter device 70 of this embodiment is a ladder filter. The filter device 70 has a first signal terminal 72 and a second signal terminal 73, and a plurality of series arm resonators and a plurality of parallel arm resonators. In the filter device 70, all the series arm resonators and all the parallel arm resonators are elastic wave resonators. Moreover, all the series arm resonators and all the 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 70 is an elastic wave device according to the present invention, it is sufficient.

[0234] The first signal terminal 72 is an antenna terminal. The antenna terminal is connected to an antenna. However, the first signal terminal 72 may not necessarily be an antenna terminal. For example, the first signal terminal 72 and the second signal terminal 73 may be configured as electrode pads or wiring.

[0235] 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 72 and the second signal terminal 73. 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 70 is not limited to the above. For example, the filter device 70 may also include a longitudinally coupled resonator type elastic wave filter.

[0236] The elastic wave resonator in filter device 70 is the elastic wave device according to the present invention. Therefore, the elastic wave resonator in filter device 70 can suppress unnecessary waves in the transverse mode and outside the passband. Thus, unnecessary waves outside the passband of filter device 70 can also be suppressed.

[0237] In addition, for example, Fig.29 In the elastic wave device of the reference example shown, the total absolute value of the busbar inclination angles of the first busbar and the second busbar in the IDT electrode 118 is greater than 5°. When the elastic wave device is used in a filter device, it is difficult to promote the miniaturization of the filter device. On the other hand, for example, in the elastic wave device 1 of the first embodiment, the total absolute value of the busbar inclination angles of the first busbar and the second busbar is less than 5°. Accordingly, when the elastic wave device 1 is used in a filter device, the miniaturization of the filter device can be promoted. This is illustrated by the ninth embodiment and its modified example.

[0238] Fig.30 FIG. 1 is a schematic top view of a filter device according to a ninth embodiment. Fig.30 In FIG. 1 , an elastic wave resonator is shown by a simplified diagram in which two diagonal lines are added to a quadrilateral. Fig.30 The dotted line in corresponds to the reference line N in each elastic wave resonator. Fig.30 The same is true for other simplified top views.

[0239] In this embodiment, a plurality of elastic wave resonators are formed on a piezoelectric substrate. Each elastic wave resonator is an elastic wave device 1 according to the first embodiment. The total absolute value of the inclination angle of the first bus bar and the second bus bar in each elastic wave resonator is less than 5°. Thus, the plurality of elastic wave resonators can be configured so that the bus bars of adjacent elastic wave resonators extend approximately parallel to each other. Accordingly, the area of ​​the portion constituting the plurality of elastic wave resonators can be reduced. Therefore, the miniaturization of the filter device 80 can be promoted.

[0240] Fig.31 The configuration of each elastic wave resonator in the variation of the 9th embodiment shown is equivalent to a configuration in which the orientation plane is rotated relative to each elastic wave resonator in the 9th embodiment. In addition, the orientation plane is a reference for the direction of the chip when manufacturing the elastic wave device. The piezoelectric layer is formed by dividing the chip. In the case of this variation, each elastic wave resonator can be configured so that the end edge of the piezoelectric substrate and the bus bar of each elastic wave resonator extend in parallel. Therefore, the miniaturization of the filter device 80A can be effectively promoted.

[0241] in addition, Fig.30 In Fig.31 The frame indicated by the two-dot chain line in shows a portion where a plurality of elastic wave resonators are arranged in the modification of the ninth embodiment. Fig.30 The dot-dashed frame in FIG. 1 shows a portion where a plurality of elastic wave resonators are arranged in the ninth embodiment. Fig.30 As shown, it can be seen that in the modified example, the effect of promoting the miniaturization of the filter device is particularly high.

[0242] In the ninth embodiment and its variant, each elastic wave resonator in the filter device is the elastic wave device 1 according to the first embodiment. Therefore, in each elastic wave resonator of the filter device, unnecessary waves in the transverse mode and outside the passband can be suppressed. Thus, unnecessary waves outside the passband of the filter device can also be suppressed.

[0243] 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 also be shapes formed by connecting tiny straight lines. 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 sixth variation of the first embodiment.

[0244] In by Fig.32In the IDT electrode 8A in the sixth 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.

[0245] The shape of each second electrode finger 17A in a plan view is also the same as the shape of each first electrode finger 16A in a plan view. In this modification, as in the first embodiment, unnecessary waves outside the passband and transverse modes can be suppressed.

[0246] Fig.33 It is a schematic front cross-sectional view of an elastic wave device according to a tenth embodiment.

[0247] 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.

[0248] 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.

[0249] 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.

[0250] Furthermore, in this embodiment, the IDT electrode 8 is also configured in the same manner as in the first embodiment. This makes it possible to suppress unnecessary waves and transverse modes outside the passband.

[0251] 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.

[0252] Fig.34 It is a schematic front cross-sectional view of an elastic wave device according to an eleventh embodiment.

[0253] The present embodiment is different from the first embodiment in that IDT electrodes 8 are provided on both principal surfaces of the piezoelectric layer 6. 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.

[0254] The piezoelectric layer 6 has a first principal surface 6a and a second principal surface 6b. The first principal surface 6a and the second principal surface 6b are opposite to each other. It is pointed out in advance that the piezoelectric layer 6 in each of the above-mentioned embodiments also has a first principal surface 6a and a second principal surface 6b. Moreover, in each of the above-mentioned embodiments and the present embodiment, an IDT electrode is provided on the first principal surface 6a. In the present embodiment, an IDT electrode 8 is also provided on the second principal surface 6b. The IDT electrode 8 provided on the second principal surface 6b is buried in the second layer 5b in the intermediate layer 5.

[0255] 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. This can suppress unnecessary waves and transverse modes outside the passband.

[0256] In addition, 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, for example.

[0257] The following describes the first to third variations of the 11th embodiment, in which only the structure of the electrode provided on the second main surface of the piezoelectric layer and at least one of the stacked structures of the piezoelectric substrate are different from the 11th embodiment. In these first to third variations, as in the 11th embodiment, it is possible to suppress unnecessary waves and transverse modes outside the passband.

[0258] exist Fig.35 In the first variation shown, the layer structure of the piezoelectric substrate 92 is different from that of the eleventh embodiment. Specifically, the piezoelectric substrate 92 has a support substrate 4, a dielectric layer 95, and a piezoelectric layer 6. The dielectric layer 95 is provided on the support 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.

[0259] 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.

[0260] exist Fig.36 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.

[0261] exist Fig.37 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.

[0262] In the tenth embodiment, the eleventh embodiment, and each modified example, an example is shown in which the IDT electrode 8 has the same structure as that of 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 tenth embodiment, the eleventh embodiment, and each modified example can also be adopted.

[0263] Examples of aspects of the elastic wave device and the filter device according to the present invention are summarized and described below.

[0264] <1> An elastic wave device comprises: a piezoelectric substrate including a piezoelectric layer; and an IDT electrode disposed on the piezoelectric layer, wherein the IDT electrode comprises a first bus bar and a second bus bar facing each other, a plurality of first electrode fingers having one end connected to the first bus bar, and a plurality of second electrode fingers having one end connected to the second bus bar, wherein the plurality of first electrode fingers and the plurality of second electrode fingers are interlaced with each other, and the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view include circular arcs or elliptical arcs, and when passing through When an imaginary line formed by connecting the top ends of the plurality of second electrode fingers is set as the first envelope, an imaginary line formed by connecting the top ends of the plurality of first electrode fingers is set as the second envelope, and the center of the circle of the arc in the shape including the first electrode fingers and the second electrode fingers or the midpoint of the two foci of the ellipse including the elliptical arc is set as a fixed point, a straight line connecting the fixed point and the top end of the second electrode finger is not parallel to the first envelope, and a straight line connecting the fixed point and the top end of the first electrode finger is not parallel to the second envelope.

[0265] <2> exist <1> In the elastic wave device described, the area between the first envelope and the second envelope in the IDT electrode is an intersection area, and when the part on any straight line passing through the fixed point in the intersection area is set as an excitation part, the resonant frequencies or anti-resonant frequencies in all the excitation parts are roughly consistent with each other.

[0266] <3> exist <2> In the elastic wave device described, among the multiple excitation parts, at least any one of the duty cycle, the electrode finger spacing and the thickness of the multiple first electrode fingers and the multiple second electrode fingers is set to be different from each other, so that the resonant frequencies or anti-resonant frequencies in all the excitation parts are roughly consistent with each other.

[0267] <4> exist <3> In the elastic wave device described, when a straight line passing through an excitation portion having the largest duty cycle among all the excitation portions and the fixed point is set as a baseline, an angle formed by the straight line passing through the fixed point and the excitation portion and the baseline is defined, and an excitation angle formed by the excitation direction of the elastic wave at the intersection of the straight line passing through the fixed point and the excitation portion and the first electrode finger or the second electrode finger and the baseline is defined, the larger the angle or the absolute value of the excitation angle is, the smaller the duty cycle is.

[0268] <5> exist <3> In the elastic wave device described, when a straight line passing through an excitation portion having the smallest duty cycle among all the excitation portions and the fixed point is set as a baseline, an angle formed by the straight line passing through the fixed point and the excitation portion and the baseline is defined, and an excitation angle formed by the excitation direction of the elastic wave at the intersection of the straight line passing through the fixed point and the excitation portion and the first electrode finger or the second electrode finger and the baseline is defined, the larger the angle or the absolute value of the excitation angle, the larger the duty cycle.

[0269] <6> exist <3> to <5> In the elastic wave device described in any one of the items, when a straight line passing through an excitation portion having the widest electrode finger spacing among all the excitation portions and the fixed point is set as a baseline, an angle formed by the straight line passing through the fixed point and the excitation portion and the baseline is defined, and an excitation angle formed by the excitation direction of the elastic wave at the intersection of the straight line passing through the fixed point and the excitation portion and the first electrode finger or the second electrode finger and the baseline is defined, the larger the angle or the absolute value of the excitation angle is, the narrower the electrode finger spacing is.

[0270] <7> exist <3> to <5> In the elastic wave device described in any one of the items, when a straight line passing through an excitation portion having the narrowest electrode finger spacing among all the excitation portions and the fixed point is set as a baseline, an angle formed by the straight line passing through the fixed point and the excitation portion and the baseline is defined, and an excitation angle formed by the excitation direction of the elastic wave at the intersection of the straight line passing through the fixed point and the excitation portion and the first electrode finger or the second electrode finger and the baseline is defined, the larger the angle or the absolute value of the excitation angle is, the wider the electrode finger spacing is.

[0271] <8> exist <3> to <7> In the elastic wave device described in any one of the items, when a straight line passing through the excitation portion where the first electrode finger and the second electrode finger are thickest among all the excitation portions and the fixed point is set as a baseline, an angle formed by the straight line passing through the fixed point and the excitation portion and the baseline is defined, and an excitation angle formed by the excitation direction of the elastic wave at the intersection of the straight line passing through the fixed point and the excitation portion and the first electrode finger or the second electrode finger and the baseline is defined, the larger the angle or the absolute value of the excitation angle is, the thinner the first electrode finger and the second electrode finger are.

[0272] <9> exist <3> to <7> In the elastic wave device described in any one of the items, when a straight line passing through the excitation portion where the thickness of the first electrode finger and the second electrode finger is the thinnest among all the excitation portions and the fixed point is set as a baseline, an angle formed by the straight line passing through the fixed point and the excitation portion and the baseline is defined, and an excitation angle formed by the excitation direction of the elastic wave at the intersection of the straight line passing through the fixed point and the excitation portion and the first electrode finger or the second electrode finger and the baseline is defined, the larger the angle or the absolute value of the excitation angle is, the thicker the first electrode finger and the second electrode finger are.

[0273] <10> exist <2> to <9> In the elastic wave device described in any one of the items, a dielectric film is further provided on the piezoelectric layer, the dielectric film is arranged to cover the IDT electrode, and the thickness of the portions of the dielectric film arranged on the plurality of the excitation portions is set to be different so that the resonant frequencies or anti-resonant frequencies of all the excitation portions are substantially consistent with each other, and when a straight line passing through the excitation portion where the thickest portion of the dielectric film among all the excitation portions is located and the fixed point is set as a baseline, an angle formed by a straight line passing through the fixed point and the excitation portion and the baseline is defined, and an excitation angle formed by an excitation direction of the elastic wave at an intersection of a straight line passing through the fixed point and the excitation portion and the first electrode finger or the second electrode finger and the baseline is defined, the larger the angle or the absolute value of the excitation angle is, the thinner the thickness of the dielectric film is.

[0274] <11> exist <2> to <9> In the elastic wave device described in any one of the items, a dielectric film is further provided on the piezoelectric layer, the dielectric film is arranged to cover the IDT electrode, and the thickness of the portions of the dielectric film arranged on the plurality of the excitation portions is set to be different so that the resonant frequencies or anti-resonant frequencies of all the excitation portions are substantially consistent with each other, and when a straight line passing through the excitation portion where the thickness of the thinnest portion of the dielectric film among all the excitation portions is located and the fixed point is set as a baseline, an angle formed by a straight line passing through the fixed point and the excitation portion and the baseline is defined, and an excitation angle formed by an excitation direction of the elastic wave at an intersection of a straight line passing through the fixed point and the excitation portion and the first electrode finger or the second electrode finger and the baseline is defined, the larger the angle or the absolute value of the excitation angle is, the thicker the dielectric film is.

[0275] <12> exist <4> to <11> In the elastic wave device described in any one of the above, a piezoelectric single crystal is used as a material of the piezoelectric layer, the piezoelectric layer has a propagation axis, and the propagation axis and the reference line extend in parallel.

[0276] <13> exist <4> to <12> In the elastic wave device described in any one of the items, when an angle formed by each of the first bus bar and the second bus bar and the reference line is defined as a bus bar inclination angle, a total of absolute values ​​of the bus bar inclination angles of the first bus bar and the second bus bar is less than or equal to 5°.

[0277] <14> exist <3> to <13> In the elastic wave device described in any one of the above items, the elastic wave device includes a plurality of the excitation parts whose duty ratios are set to be different from each other so that the resonant frequencies or anti-resonant frequencies in all the excitation parts are substantially consistent with each other, the elastic wave device has 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, and the plurality of second offset electrodes are respectively connected to the second bus bar, the top ends of the second electrode fingers and the top ends of the first offset electrodes are opposed to each other with a gap therebetween, 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, the shapes of the plurality of first offset electrodes include a circular arc included in a circle centered at the fixed point, or a shape of an elliptical arc included in an ellipse with the fixed point as the midpoint of two foci, and the duty ratio of a portion of the first offset electrode on an extension line of any of the excitation parts and a portion including the excitation part is fixed.

[0278] <15> exist <3> to <13> In the elastic wave device described in any one of the above items, the elastic wave device includes a plurality of the excitation parts having different duty ratios so that the resonant frequencies or antiresonant frequencies of all the excitation parts are substantially identical to each other, the elastic wave device 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, the tip of the second electrode finger and the tip of the first offset electrode are opposed to each other with a gap therebetween, the tip of the first electrode finger and the tip of the second offset electrode are opposed to each other with a gap therebetween, the shape of the plurality of first offset electrodes includes a circular arc included in a circle centered at the fixed point or an elliptical arc included in an ellipse with the fixed point as the midpoint of two foci, and in a region between the first bus bar or the second bus bar and the intersection region, the duty ratio changes in one of a direction in which it increases and a direction in which it decreases as it approaches the first bus bar or the second bus bar.

[0279] <16> exist <1> to <13> In the elastic wave device described in any one of the items, the elastic wave device 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, the top ends of the second electrode fingers and the top ends of the first offset electrodes are opposed to each other with a gap therebetween, 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, the shape of the plurality of first offset electrodes includes a circular arc included in a circle centered at the fixed point, or a shape of an elliptical arc included in an ellipse with the fixed point as the midpoint of two foci, and the width of each of the first offset electrodes is fixed.

[0280] <17> exist <1> to <13> as well as <16> In the elastic wave device described in any one of the items, the elastic wave device 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, the top ends of the second electrode fingers and the top ends of the first offset electrodes are opposed to each other with a gap therebetween, 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, and the first offset electrodes have a linear shape.

[0281] <18> exist <1> to <17> 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.

[0282] <19> exist <1> to <17> 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.

[0283] <20> exist <1> to <17> 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.

[0284] <21> exist <1> to <20> 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.

[0285] <22> exist <21> In the elastic wave device described above, the piezoelectric substrate includes an intermediate layer provided between the supporting substrate and the piezoelectric layer.

[0286] <23> exist <1> to <20> In the elastic wave device described in any one of the above, the piezoelectric substrate includes only the piezoelectric layer.

[0287] <24> A filter device comprises a plurality of elastic wave resonators, at least one of which is <1> to <23> An elastic wave device as described in any one of the items.

[0288] Description of Reference Numerals

[0289] 1…Elastic wave device

[0290] 2, 2A, 2B…Piezoelectric substrate

[0291] 3…Supporting member

[0292] 4. 4B…Supporting base plate

[0293] 4c…concave part

[0294] 5.5A…Middle layer

[0295] 5a, 5b…1st floor, 2nd floor

[0296] 6…Piezoelectric layer

[0297] 6a, 6b…1st main surface, 2nd main surface

[0298] 7… Acoustic reflective membrane

[0299] 8, 8A…IDT electrode

[0300] 9A, 9B…Reflector

[0301] 9a, 9b…Electrode fingers

[0302] 12a, 12b…low acoustic impedance layer

[0303] 13a~13c…High acoustic impedance layer

[0304] 14, 15…1st bus bar, 2nd bus bar

[0305] 16, 17…1st electrode finger, 2nd electrode finger

[0306] 16A, 17A...1st electrode finger, 2nd electrode finger

[0307] 18, 19 ... first offset electrode, second offset electrode

[0308] 28, 38, 48…IDT electrode

[0309] 55…Dielectric film

[0310] 58…IDT electrode

[0311] 66, 66A, 66B ... first electrode finger

[0312] 67, 67A, 67B ... second electrode finger

[0313] 68, 68A, 68B ... first offset electrode

[0314] 70…Filter device

[0315] 72, 73…1st signal terminal, 2nd signal terminal

[0316] 80, 80A…Filter device

[0317] 92…Piezoelectric substrate

[0318] 92c…Hollow part

[0319] 95…Dielectric layer

[0320] 98…Electrode

[0321] 99…Protective film

[0322] 99a, 99b...1st protective layer, 2nd protective layer

[0323] 108…IDT electrode

[0324] 109A, 109B…Reflector

[0325] 118…IDT electrode

[0326] C…Fixed point

[0327] D…Crossover area

[0328] E1, E2…1st envelope, 2nd envelope

[0329] G1, G2… Clearance

[0330] N…Baseline

[0331] P1, P2…Parallel arm resonator

[0332] S1~S3...series arm resonator.

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 comprises a first bus bar and a second bus bar facing each other, a plurality of first electrode fingers having one end connected to the first bus bar, and a plurality of second electrode fingers having one end connected to the second bus bar, wherein the plurality of first electrode fingers and the plurality of second electrode fingers are interlaced with each other. 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. When an imaginary line formed by connecting the top ends of the plurality of second electrode fingers is set as the first envelope, an imaginary line formed by connecting the top ends of the plurality of first electrode fingers is set as the second envelope, and the center of the circle of the arc in the shape including the first electrode fingers and the second electrode fingers or the midpoint of the two foci of the ellipse including the elliptical arc is set as a fixed point, a straight line connecting the fixed point and the top end of the second electrode finger is not parallel to the first envelope, and a straight line connecting the fixed point and the top end of the first electrode finger is not parallel to the second envelope.

2. The elastic wave device according to claim 1, wherein: The area between the first envelope and the second envelope in the IDT electrode is a crossover area, and when a portion on any straight line passing through the fixed point in the crossover area is set as an excitation portion, the resonant frequencies or anti-resonant frequencies in all the excitation portions are substantially consistent with each other.

3. The elastic wave device according to claim 2, wherein: At least one of the duty ratio, the electrode finger pitch, and the thickness of the first electrode fingers and the second electrode fingers is set to be different between the plurality of excitation parts so that the resonant frequencies or anti-resonant frequencies in all the excitation parts are substantially consistent with each other.

4. The elastic wave device according to claim 3, wherein: In the case where a straight line passing through an excitation portion having the largest duty cycle among all the excitation portions and the fixed point is set as a baseline, an angle formed by the straight line passing through the fixed point and the excitation portion and the baseline is defined, and an excitation angle formed by the excitation direction of the elastic wave at the intersection of the straight line passing through the fixed point and the excitation portion and the first electrode finger or the second electrode finger and the baseline is defined, the larger the angle or the absolute value of the excitation angle is, the smaller the duty cycle is.

5. The elastic wave device according to claim 3, wherein: In the case where a straight line passing through an excitation portion having the smallest duty cycle among all the excitation portions and the fixed point is set as a baseline, an angle formed by the straight line passing through the fixed point and the excitation portion and the baseline is defined, and an excitation angle formed by the excitation direction of the elastic wave at the intersection of the straight line passing through the fixed point and the excitation portion and the first electrode finger or the second electrode finger and the baseline is defined, the larger the angle or the absolute value of the excitation angle is, the larger the duty cycle is.

6. The elastic wave device according to any one of claims 3 to 5, wherein: In a case where a straight line passing through an excitation portion having the widest electrode finger spacing among all the excitation portions and the fixed point is set as a baseline, an angle formed by the straight line passing through the fixed point and the excitation portion and the baseline is defined, and an excitation angle formed by the excitation direction of the elastic wave at the intersection of the straight line passing through the fixed point and the excitation portion and the first electrode finger or the second electrode finger and the baseline is defined, the larger the angle or the absolute value of the excitation angle is, the narrower the electrode finger spacing is.

7. The elastic wave device according to any one of claims 3 to 5, wherein: In a case where a straight line passing through an excitation portion having the narrowest electrode finger spacing among all the excitation portions and the fixed point is set as a baseline, an angle formed by the straight line passing through the fixed point and the excitation portion and the baseline is defined, and an excitation angle formed by the excitation direction of the elastic wave at the intersection of the straight line passing through the fixed point and the excitation portion and the first electrode finger or the second electrode finger and the baseline is defined, the larger the angle or the absolute value of the excitation angle is, the wider the electrode finger spacing is.

8. The elastic wave device according to any one of claims 3 to 7, wherein: When a straight line passing through the excitation portion where the thickness of the first electrode finger and the second electrode finger is the thickest among all the excitation portions and the fixed point is set as a baseline, an angle formed by the straight line passing through the fixed point and the excitation portion and the baseline is defined, and an excitation angle formed by the excitation direction of the elastic wave at the intersection of the straight line passing through the fixed point and the excitation portion and the first electrode finger or the second electrode finger and the baseline is defined, the larger the angle or the absolute value of the excitation angle is, the thinner the thickness of the first electrode finger and the second electrode finger is.

9. The elastic wave device according to any one of claims 3 to 7, wherein: When a straight line passing through the excitation portion where the thickness of the first electrode finger and the second electrode finger is the thinnest among all the excitation portions and the fixed point is set as a baseline, an angle formed by the straight line passing through the fixed point and the excitation portion and the baseline is defined, and an excitation angle formed by the excitation direction of the elastic wave at the intersection of the straight line passing through the fixed point and the excitation portion and the first electrode finger or the second electrode finger and the baseline is defined, the larger the angle or the absolute value of the excitation angle is, the thicker the first electrode finger and the second electrode finger are.

10. The elastic wave device according to any one of claims 2 to 9, wherein: A dielectric film is further provided on the piezoelectric layer, wherein the dielectric film is provided to cover the IDT electrode. The thickness of the dielectric film is set to be different between the portions provided on the plurality of excitation parts so that the resonant frequencies or anti-resonant frequencies of all the excitation parts are substantially consistent with each other. In a case where a straight line passing through an excitation portion where the thickest part of the dielectric film among all the excitation portions is located and the fixed point is set as a baseline, an angle formed by the straight line passing through the fixed point and the excitation portion and the baseline is defined, and an excitation angle formed by the excitation direction of the elastic wave at the intersection of the straight line passing through the fixed point and the excitation portion and the first electrode finger or the second electrode finger and the baseline is defined, the larger the angle or the absolute value of the excitation angle is, the thinner the dielectric film is.

11. The elastic wave device according to any one of claims 2 to 9, wherein: A dielectric film is further provided on the piezoelectric layer, wherein the dielectric film is provided to cover the IDT electrode. The thickness of the dielectric film is set to be different between the portions provided on the plurality of excitation parts so that the resonant frequencies or anti-resonant frequencies of all the excitation parts are substantially consistent with each other. In a case where a straight line passing through an excitation portion where the thickness of the thinnest part of the dielectric film among all the excitation portions is located and the fixed point is set as a baseline, an angle formed by the straight line passing through the fixed point and the excitation portion and the baseline is defined, and an excitation angle formed by the excitation direction of the elastic wave at the intersection of the straight line passing through the fixed point and the excitation portion and the first electrode finger or the second electrode finger and the baseline is defined, the larger the angle or the absolute value of the excitation angle is, the thicker the dielectric film is.

12. The elastic wave device according to any one of claims 4 to 11, wherein: As the material of the piezoelectric layer, a piezoelectric single crystal is used. The piezoelectric layer has a propagation axis, and the propagation axis and the reference line extend in parallel.

13. The elastic wave device according to any one of claims 4 to 12, wherein: When an angle formed by each of the first bus bar and the second bus bar and the reference line is defined as a bus bar inclination angle, the total of absolute values ​​of the bus bar inclination angles of the first bus bar and the second bus bar is 5° or less.

14. The elastic wave device according to any one of claims 3 to 13, wherein: The elastic wave device includes a plurality of the excitation parts having different duty ratios so that the resonant frequencies or anti-resonant frequencies of all the excitation parts are substantially consistent with each other. The elastic wave device 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 of the second electrode finger and the tip of the first offset electrode are opposed to each other with a gap therebetween, and the tip of the first electrode finger and the tip of the second offset electrode are opposed to each other with a gap therebetween. The shapes of the plurality of first offset electrodes include a circular arc included in a circle with the fixed point as the center, or an elliptical arc included in an ellipse with the fixed point as the midpoint of two foci. The duty ratio of a portion of the first offset electrode on an extended line where any of the excitation portions is provided and a portion including the excitation portion is constant.

15. The elastic wave device according to any one of claims 3 to 13, wherein: The elastic wave device includes a plurality of the excitation parts having different duty ratios so that the resonant frequencies or anti-resonant frequencies of all the excitation parts are substantially consistent with each other. The elastic wave device 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 of the second electrode finger and the tip of the first offset electrode are opposed to each other with a gap therebetween, and the tip of the first electrode finger and the tip of the second offset electrode are opposed to each other with a gap therebetween. The shapes of the plurality of first offset electrodes include a circular arc included in a circle with the fixed point as the center, or an elliptical arc included in an ellipse with the fixed point as the midpoint of two foci. In a region between the first bus bar or the second bus bar and the intersection region, the duty ratio changes in one of a direction of increasing and a direction of decreasing as the distance to the first bus bar or the second bus bar increases.

16. The elastic wave device according to any one of claims 1 to 13, wherein: The elastic wave device 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 of the second electrode finger and the tip of the first offset electrode are opposed to each other with a gap therebetween, and the tip of the first electrode finger and the tip of the second offset electrode are opposed to each other with a gap therebetween. The shapes of the plurality of first offset electrodes include a circular arc included in a circle with the fixed point as the center, or an elliptical arc included in an ellipse with the fixed point as the midpoint of two foci. The width of each of the first offset electrodes is fixed.

17. The elastic wave device according to any one of claims 1 to 13 and 16, wherein: The elastic wave device 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 of the second electrode finger and the tip of the first offset electrode are opposed to each other with a gap therebetween, and the tip of the first electrode finger and the tip of the second offset electrode are opposed to each other with a gap therebetween. The first offset electrode has a linear shape.

18. The elastic wave device according to any one of claims 1 to 17, 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.

19. The elastic wave device according to any one of claims 1 to 17, 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.

20. The elastic wave device according to any one of claims 1 to 17, 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.

21. The elastic wave device according to any one of claims 1 to 20, wherein: The piezoelectric substrate has a supporting substrate. The piezoelectric layer is provided on the supporting substrate.

22. The elastic wave device according to claim 21, wherein: The piezoelectric substrate includes an intermediate layer provided between the supporting substrate and the piezoelectric layer.

23. The elastic wave device according to any one of claims 1 to 20, wherein: The piezoelectric substrate includes only the piezoelectric layer.

24. 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 23.

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