Elastic wave device

Abstract

Provided is an elastic wave device capable of more reliably suppressing a transverse mode. An elastic wave device is provided with a piezoelectric layer provided on an acoustic reflection film, an IDT provided on the piezoelectric layer, and a mass addition film provided in an edge region and continuously provided so as to overlap a plurality of electrode fingers and a region between the electrode fingers. And a method for manufacturing the same. The value expressed in percentage by the product of the density and thickness of any layer divided by the density of Al and the wavelength lambda is set as the Al-converted normalized thickness of the layer, the total of the Al-converted normalized thicknesses of the electrode finger layers is set as the Al-converted normalized thickness of the electrode fingers, i.e., TIDT [%], and the Al-converted normalized thickness of the mass-added film 9 is set as Tm [%]. If TR [%] is the value obtained by dividing the thickness ratio of the Al-converted normalized thickness Tm of the mass-added film 9 to the Al-converted normalized thickness TIDT of the electrode finger by 3.15, d is the duty ratio of IDT27, and W is the wavelength ratio width obtained by dividing the dimension of the mass-added film 9 in the direction in which the electrode finger extends by the wavelength [lambda], TR [%] is the value obtained by dividing Tm, TIDT, of the mass-added film 9 by 3.15. And the data are in an ellipse or a rectangle as shown in figures 4-8.

Description

Technical Field

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

[0002] In the past, elastic wave devices have been widely used as filters for 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 electrode is provided on a piezoelectric substrate. The IDT (Interdigital Transducer) electrode has a central region and a pair of low acoustic velocity regions. The pair of low acoustic velocity regions sandwich the central region in the direction in which the electrode fingers of the IDT electrode extend. A mass addition film is provided in each low acoustic velocity region. The product of the wavelength-normalized film thickness of the mass addition film and the density of the mass addition film is set to be less than 13.4631. In addition, the wavelength-normalized film thickness is a film thickness normalized by a wavelength specified by the electrode finger spacing of the IDT electrode. According to the above structure, the suppression of the stray caused by the transverse mode is achieved.

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-092095 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] As a result of studies, the inventors of the present invention have found that the degree of the effect of suppressing spurious emission caused by the transverse mode differs depending on the film thickness and duty ratio of the electrode fingers of the IDT electrode.

[0008] An object of the present invention is to provide an elastic wave device capable of more reliably suppressing a transverse mode.

[0009] Technical solutions to solve problems

[0010] In a broad aspect of the elastic wave device involved in the present invention, it comprises: a high-acoustic-velocity material layer; a piezoelectric layer, which is arranged on the high-acoustic-velocity material layer and contains lithium tantalate; and an IDT, which is arranged on the piezoelectric layer and has a plurality of electrode fingers, wherein the plurality of electrode fingers each contain at least one electrode finger layer, wherein the acoustic velocity of the body wave propagating in the high-acoustic-velocity material layer is higher than the acoustic velocity of the elastic wave propagating in the piezoelectric layer, wherein the direction in which the plurality of electrode fingers extend is set as an electrode finger extension direction, and when the IDT is observed from a direction orthogonal to the electrode finger extension direction, a region in which adjacent electrode fingers overlap with each other is a cross region, wherein the cross region has a central region and is configured as The elastic wave device further comprises a mass-added film in a pair of edge regions sandwiching the central region in the extending direction of the electrode fingers, the mass-added film being arranged in at least one of the edge regions and being continuously arranged to overlap with the plurality of electrode fingers and the region between the electrode fingers in a plan view, with a resonance frequency higher than 1 GHz, and a value obtained by dividing the product of the density and thickness of any layer by the density of Al and the wavelength λ by a percentage as the Al-converted normalized thickness of the layer, and the sum of the Al-converted normalized thicknesses of the electrode finger layers as the Al-converted normalized thickness of the electrode fingers, i.e., T IDT [%], the Al-converted normalized thickness of the mass-added film is set to T m [%], convert the Al of the mass added film into a normalized thickness T m The Al-converted normalized thickness T of the electrode finger portion IDT The value obtained by dividing the thickness ratio by 3.15 is set as T R [%], T R = (1 / 3.15) × (T m / T IDT )×100[%], the duty ratio of the IDT is set to d, the dimension of the mass-added film along the extending direction of the electrode finger is divided by the wavelength λ to be the wavelength ratio width W, the value of x is set to be equivalent to the value of the wavelength ratio width W, and the value of y is set to be equivalent to the thickness ratio T R When the value of the wavelength ratio width W and the thickness ratio T in the xy plane is R is a value within the range of an ellipse and the inside of the ellipse represented by setting θ to be greater than or equal to 0° and less than 360° in the following equations 1 and 2,

[0011] x=0.19×cos(-5.5°)×cosθ-0.021×sin(-5.5°)×sinθ+0.0146×T IDT 2 -0.229×TIDT +1.5611+0.4×(d-0.55) Formula 1

[0012] y=0.19×sin(-5.5°)×cosθ+0.021×cos(-5.5°)×sinθ+10.15 Equation 2.

[0013] In other broad aspects of the elastic wave device involved in the present invention, it comprises: a high-acoustic material layer; a piezoelectric layer, which is arranged on the high-acoustic material layer and contains lithium tantalate; and an IDT, which is arranged on the piezoelectric layer and has a plurality of electrode fingers, wherein the plurality of electrode fingers each include at least one electrode finger layer, wherein the acoustic velocity of the body wave propagating in the high-acoustic material layer is higher than the acoustic velocity of the elastic wave propagating in the piezoelectric layer, and the direction in which the plurality of electrode fingers extend is set as the electrode finger extension direction. When the IDT is observed from a direction orthogonal to the electrode finger extension direction, the region in which adjacent electrode fingers overlap with each other is a cross region, and the cross region has a central region and a configuration The elastic wave device further comprises a mass-added film, which is a pair of edge regions sandwiching the central region in the extending direction of the electrode fingers, and the mass-added film is provided in at least one of the edge regions, and is continuously provided to overlap with the plurality of electrode fingers and the region between the electrode fingers when viewed from above, and the resonant frequency is higher than 1 GHz, and a wavelength specified by the electrode finger pitch of the IDT is set as λ, a value obtained by dividing the product of the density and thickness of any layer by the density of Al and the wavelength λ and expressed as a percentage is set as the Al-converted normalized thickness of the layer, and the total of the Al-converted normalized thicknesses of the electrode finger layers is set as the Al-converted normalized thickness of the electrode fingers, that is, T IDT [%], the Al-converted normalized thickness of the mass-added film is set to T m [%], convert the Al of the mass added film into a normalized thickness T m The Al-converted normalized thickness T of the electrode finger portion IDT The value obtained by dividing the thickness ratio by 3.15 is set as T R [%], T R = (1 / 3.15) × (T m / T IDT )×100[%], when the duty ratio of the IDT is set to d and the value obtained by dividing the dimension of the mass addition film along the extension direction of the electrode finger by the wavelength λ is set to the wavelength ratio width W, the wavelength ratio width W of the mass addition film is: 0.88×{0.0101×T IDT 2 -0.1677×T IDT+1.3201+0.4×(d-0.55)}≤W≤1.12×{0.0101×T IDT 2 -0.1677×T IDT +1.3201+0.4×(d-0.55)}, the thickness ratio T R =0.88×10.7≤T R ≤1.12×10.7.

[0014] In another broad aspect of the elastic wave device according to the present invention, the device comprises: a high-acoustic-velocity material layer; a piezoelectric layer, which is arranged on the high-acoustic-velocity material layer and contains lithium tantalate; and an IDT, which is arranged on the piezoelectric layer and has a plurality of electrode fingers, wherein the plurality of electrode fingers each contain at least one electrode finger layer, wherein the acoustic velocity of the body wave propagating in the high-acoustic-velocity material layer is higher than the acoustic velocity of the elastic wave propagating in the piezoelectric layer, wherein the direction in which the plurality of electrode fingers extend is set as an electrode finger extension direction, and when the IDT is observed from a direction orthogonal to the electrode finger extension direction, a region in which adjacent electrode fingers overlap with each other is a cross region, wherein the cross region has a central region and is configured as The elastic wave device further comprises a mass-added film in a pair of edge regions sandwiching the central region in the extending direction of the electrode fingers, the mass-added film being arranged in at least one of the edge regions and being continuously arranged to overlap with the plurality of electrode fingers and the region between the electrode fingers in a plan view, the resonant frequency being 1 GHz or less, and a value obtained by dividing the product of the density and thickness of any layer by the density of Al and the wavelength λ by a percentage as the Al-converted normalized thickness of the layer, and the sum of the Al-converted normalized thicknesses of the electrode finger layers as the Al-converted normalized thickness of the electrode fingers, i.e., T. IDT [%], the Al-converted normalized thickness of the mass-added film is set to T m [%], convert the Al of the mass added film into a normalized thickness T m The Al-converted normalized thickness T of the electrode finger portion IDT The value obtained by dividing the thickness ratio by 3.15 is set as T R [%], T R = (1 / 3.15) × (T m / T IDT )×100[%], the duty ratio of the IDT is set to d, the dimension of the mass-added film along the extending direction of the electrode finger is divided by the wavelength λ to be the wavelength ratio width W, the value of x is set to be equivalent to the value of the wavelength ratio width W, and the value of y is set to be equivalent to the thickness ratio T RWhen the value of the wavelength ratio width W and the thickness ratio T in the xy plane is R is a value within the range of an ellipse and the inside of the ellipse represented by setting t to be greater than 0° and less than 360° in the following equations 3 and 4,

[0015] x=0.16×cost×cos(1.3°)-25.5×sint×sin(1.3°)+2.22-2.54×d+2.06×d 2 Formula 3

[0016] y=0.16×cost×sin(1.3°)+25.5×cost×sin(1.3°)+25.5-0.033×(T IDT -7.83) Formula 4.

[0017] In another broad aspect of the elastic wave device involved in the present invention, it comprises: a high-acoustic material layer; a piezoelectric layer, which is arranged on the high-acoustic material layer and contains lithium niobate; and an IDT, which is arranged on the piezoelectric layer and has a plurality of electrode fingers, each of which includes at least one electrode finger layer, the acoustic velocity of the body wave propagating in the high-acoustic material layer is higher than the acoustic velocity of the elastic wave propagating in the piezoelectric layer, the direction in which the plurality of electrode fingers extend is set as the electrode finger extension direction, and when the IDT is observed from a direction orthogonal to the electrode finger extension direction, the area where adjacent electrode fingers overlap with each other is a cross area, and the cross area has a central area , and a pair of edge regions arranged to sandwich the central region in the extending direction of the electrode fingers, the elastic wave device further comprising a mass-added film, the mass-added film being arranged in at least one of the edge regions and being continuously arranged to overlap with the plurality of electrode fingers and the region between the electrode fingers in a plan view, wherein a wavelength specified by the electrode finger pitch of the IDT is set to λ, a value obtained by dividing the product of the density and thickness of any layer by the density of Al and the wavelength λ and expressed as a percentage is set as the Al-converted normalized thickness of the layer, and the sum of the Al-converted normalized thicknesses of the electrode finger layers is set as the Al-converted normalized thickness of the electrode fingers, i.e., T IDT [%], the Al-converted normalized thickness of the mass-added film is set to T m [%], convert the Al of the mass added film into a normalized thickness T m The Al-converted normalized thickness T of the electrode finger portion IDT The value obtained by dividing the thickness ratio by 3.15 is set as T R [%], T R = (1 / 3.15) × (T m / T IDT)×100[%], the duty ratio of the IDT is set to d, the dimension of the mass-added film along the extending direction of the electrode finger is divided by the wavelength λ to be the wavelength ratio width W, the value of x is set to be equivalent to the value of the wavelength ratio width W, and the value of y is set to be equivalent to the thickness ratio T R When the value of the wavelength ratio width W and the thickness ratio T in the xy plane is R is a value within the range of an ellipse and the inside of the ellipse represented by setting t to be greater than 0° and less than 360° in the following equations 5 and 6,

[0018] x=0.22×cost×cos(6°)-3.9×sint×sin(6°)+1.0+0.4×(d-0.5)+0.0022×(T IDT -6.9) Formula 5

[0019] y=0.22×cost×sin(6°)+3.9×cost×sin(6°)+7.9-0.033×(T IDT -6.9) Formula 6.

[0020] Effects of the Invention

[0021] According to the elastic wave device according to the present invention, the transverse mode can be suppressed more reliably. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic plan view of the elastic wave device according to the first embodiment of the present invention.

[0023] Figure 2 It is along Figure 1 Schematic cross-sectional view of line II in FIG.

[0024] Figure 3 It is along Figure 1 Schematic cross-sectional view along line II-II in FIG.

[0025] Figure 4 is the Al-converted normalized thickness T of the electrode finger portion. IDT When the duty ratio d is 7.54% and the duty ratio d is 0.55, the magnitude of the ripple caused by the transverse mode becomes 1 dB or 0.1 dB, and the wavelength-to-width W and thickness ratio T of the mass-added film are R Graph of the relationship.

[0026] Figure 5 is the Al-converted normalized thickness T of the electrode finger portion. IDT When the duty ratio d is 6.17% and the duty ratio d is 0.55, the magnitude of the ripple caused by the transverse mode becomes 1 dB or 0.1 dB, and the wavelength-to-width W and thickness ratio T of the mass-added film areR Graph of the relationship.

[0027] Figure 6 is the Al-converted normalized thickness T of the electrode finger portion. IDT When the duty ratio d is 5.22% and the duty ratio d is 0.55, the magnitude of the ripple caused by the transverse mode becomes 1 dB or 0.1 dB, and the wavelength-to-width W and thickness ratio T of the mass-added film are R Graph of the relationship.

[0028] Figure 7 is the Al-converted normalized thickness T of the electrode finger portion. IDT When the duty ratio d is 6.17% and the ripple caused by the transverse mode is 0.5, the wavelength-to-width W and thickness ratio T of the mass-added film are 1 dB or 0.1 dB. R Graph of the relationship.

[0029] Figure 8 is the Al-converted normalized thickness T of the electrode finger portion. IDT When the duty ratio d is 6.17% and the ripple caused by the transverse mode is 0.6, the wavelength-to-width W and thickness ratio T of the mass-added film are 1 dB or 0.1 dB. R Graph of the relationship.

[0030] Fig. 9 (a) is a diagram showing that ripples are generated in the attenuation frequency characteristics of the filter device. Fig. 9 (b) is shown by Fig. 9 (a) is a diagram showing the attenuation-frequency characteristics and the impedance-frequency characteristics of an elastic wave resonator used in a filter device. Fig. 9 (c) is shown by Fig. 9 (b) is a graph showing the impedance-frequency characteristics of the return loss of the elastic wave resonator.

[0031] Fig.10 This is a diagram showing the relationship between the magnitude of the ripple, which is the return loss in the first elastic wave resonator, and the magnitude of the ripple in the attenuation frequency characteristic of the filter device.

[0032] Fig.11 This is a diagram showing the relationship between the magnitude of the ripple, which is the return loss in the second elastic wave resonator, and the magnitude of the ripple in the attenuation frequency characteristic of the filter device.

[0033] Fig.12 The Al-converted normalized thickness T of the electrode finger portion when the piezoelectric layer includes lithium tantalate and the resonance frequency is 1 GHz or less is shown. IDTWhen the duty ratio d is 7.83% and the ripple caused by the transverse mode is 1 dB or 0.3 dB, the wavelength-to-width W and thickness ratio T of the mass-added film are R Graph of the relationship.

[0034] Fig.13 The Al-converted normalized thickness T of the electrode finger portion when the piezoelectric layer includes lithium tantalate and the resonance frequency is 1 GHz or less is shown. IDT When the duty ratio d is 3.77% and the ripple caused by the transverse mode is 1 dB or 0.3 dB, the wavelength-to-width W and thickness ratio T of the mass-added film are R Graph of the relationship.

[0035] Fig.14 The Al-converted normalized thickness T of the electrode finger portion when the piezoelectric layer includes lithium tantalate and the resonance frequency is 1 GHz or less is shown. IDT When the duty ratio d is 7.83% and the ripple caused by the transverse mode is 1 dB or 0.3 dB, the wavelength-to-width W and thickness ratio T of the mass-added film are R Graph of the relationship.

[0036] Fig.15 (a) is a diagram showing that ripples occur in the attenuation frequency characteristics of the filter device in the low frequency band. Fig.15 (b) is shown by Fig.15 (a) is a diagram showing the attenuation-frequency characteristics and the impedance-frequency characteristics of an elastic wave resonator used in a filter device. Fig.15 (c) is shown by Fig.15 (b) is a graph showing the impedance-frequency characteristics of the return loss of the elastic wave resonator.

[0037] Fig.16 : is a graph showing the Al-converted normalized thickness T of the electrode finger portion when the piezoelectric layer includes lithium niobate. IDT When the duty ratio d is 6.9% and the ripple caused by the transverse mode is 1 dB or 0.2 dB, the wavelength-to-width W and thickness ratio T of the mass-added film are R Graph of the relationship.

[0038] Fig.17 : is a graph showing the Al-converted normalized thickness T of the electrode finger portion when the piezoelectric layer includes lithium niobate. IDT When the duty ratio d is 13.7% and the ripple caused by the transverse mode is 0.5, the wavelength-to-width ratio W and thickness ratio T of the mass-added film are 1dB or 0.2dB. R Graph of the relationship.

[0039] Fig.18 : is a graph showing the Al-converted normalized thickness T of the electrode finger portion when the piezoelectric layer includes lithium niobate. IDT When the duty ratio d is 13.7% and the ripple caused by the transverse mode is 1 dB or 0.2 dB, the wavelength-to-width W and thickness ratio T of the mass-added film are R Graph of the relationship. DETAILED DESCRIPTION

[0040] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings to make the present invention clear.

[0041] 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.

[0042] 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. Figure 3 It is along Figure 1 A schematic cross-sectional view of the II-II line in FIG. Figure 1 In the figure, a dielectric film described later is omitted.

[0043] like Figure 1 and Figure 2 As shown, the elastic wave device 1 includes a piezoelectric substrate 2. Figure 2 As shown, the piezoelectric substrate 2 includes a supporting substrate 3, a high-acoustic-velocity film 4 as a high-acoustic-velocity material layer, a low-acoustic-velocity film 5, and a piezoelectric layer 6. The high-acoustic-velocity film 4 is disposed on the supporting substrate 3. The low-acoustic-velocity film 5 is disposed on the high-acoustic-velocity film 4. The piezoelectric layer 6 is disposed on the low-acoustic-velocity film 5. In the present embodiment, the piezoelectric layer 6 is indirectly disposed on the high-acoustic-velocity material layer via the low-acoustic-velocity film 5. However, the piezoelectric layer 6 may also be directly disposed on the high-acoustic-velocity material layer.

[0044] The piezoelectric layer 6 includes, for example, LiTaO 3 In this specification, a member containing a certain material includes a member containing a small amount of impurities to the extent that the electrical characteristics of the elastic wave device are not significantly deteriorated. An IDT electrode 7 is provided on the piezoelectric layer 6. By applying an AC voltage to the IDT electrode 7, elastic waves are excited.

[0045] The high-acoustic-velocity material layer in the piezoelectric substrate 2 is a relatively high-acoustic-velocity layer. More specifically, the acoustic velocity of the body wave propagating in the high-acoustic-velocity material layer is higher than the acoustic velocity of the elastic wave propagating in the piezoelectric layer 6. In the present embodiment, the high-acoustic-velocity material layer is the high-acoustic-velocity film 4. On the other hand, the low-acoustic-velocity film 5 is a relatively low-acoustic-velocity film. More specifically, the acoustic velocity of the body wave propagating in the low-acoustic-velocity film 5 is lower than the acoustic velocity of the body wave propagating in the piezoelectric layer 6.

[0046] like Figure 1 As shown, the IDT electrode 7 has a first bus bar 16 and a second bus bar 17, and a plurality of first electrode fingers 18 and a plurality of second electrode fingers 19. The first bus bar 16 and the second bus bar 17 are opposite to each other. One end of the plurality of first electrode fingers 18 is connected to the first bus bar 16, respectively. One end of the plurality of second electrode fingers 19 is connected to the second bus bar 17, respectively. The plurality of first electrode fingers 18 and the plurality of second electrode fingers 19 are interlaced with each other. The first electrode fingers 18 and the second electrode fingers 19 are connected to different potentials.

[0047] like Figure 2 As shown in FIG. 1 , a dielectric film 8 is provided on the piezoelectric layer 6 so as to cover the IDT electrode 7. In the present embodiment, silicon oxide is used as a material of the dielectric film 8. However, the material of the dielectric film 8 is not limited to the above.

[0048] IDT 27 is formed by stacking IDT electrode 7 and dielectric film 8. The portion where the first electrode finger 18 of IDT electrode 7 and dielectric film 8 are stacked is first electrode finger portion 28 of IDT 27. The portion where the second electrode finger 19 of IDT electrode 7 and dielectric film 8 are stacked is second electrode finger portion 29 of IDT 27. Hereinafter, first electrode finger portion 28 and second electrode finger portion 29 of IDT 27 are sometimes simply described as electrode finger portions. First electrode finger 18 and second electrode finger 19 of IDT electrode 7 are sometimes simply described as electrode fingers.

[0049] Each electrode finger of IDT27 has a plurality of electrode finger layers. The plurality of electrode finger layers include a metal layer 27a and a dielectric layer 27b. The metal layer 27a is a layer included in the IDT electrode 7. Specifically, the metal layer 27a is a portion of the electrode finger of the IDT electrode 7. In addition, in the present embodiment, the IDT electrode 7 includes a stacked metal film. Specifically, the IDT electrode 7 includes an Al layer and a plurality of Ti layers. Therefore, each electrode finger of IDT27 includes a plurality of metal layers 27a. However, the material and layer structure of the IDT electrode 7 are not limited to the above. The IDT electrode 7 may also include a single layer of metal film. In this case, each electrode finger of the IDT27 includes only a single layer of metal layer 27a.

[0050] The dielectric layer 27b of the IDT 27 is a layer included in the dielectric film 8. In addition, the dielectric film 8 may not necessarily be provided. In this case, the IDT 27 is the IDT electrode 7. Therefore, the electrode finger layer may include only the metal layer 27a. Each electrode finger only needs to include at least one electrode finger layer.

[0051] A pair of reflectors 15A and 15B are provided on the piezoelectric layer 6. When the direction in which the plurality of electrode fingers of the IDT 27 extend is set as the electrode finger extension direction, the reflectors 15A and 15B are opposed to each other with the IDT 27 sandwiched in a direction orthogonal to the electrode finger extension direction. In addition, in the present embodiment, the direction orthogonal to the electrode finger extension direction is parallel to the elastic wave propagation direction. The same material as the IDT electrode 7 can be used in each reflector. The elastic wave device 1 of the present embodiment is a surface acoustic wave resonator. The elastic wave device 1 can be appropriately used, for example, for a filter device in a mid-high frequency band (MHB). The frequency band of the mid-high frequency band is 1.7 GHz to 2.7 GHz.

[0052] When the IDT 27 is viewed from a direction perpendicular to the direction in which the electrode fingers extend, the region in which adjacent electrode fingers overlap each other is Figure 1 The intersection region A shown. The intersection region A has a central region C and a pair of edge regions. Specifically, the pair of edge regions are a first edge region Ea and a second edge region Eb. The first edge region Ea and the second edge region Eb are arranged to face each other with the central region C sandwiched therebetween in the extending direction of the electrode finger. The first edge region Ea is located on the first bus bar 16 side. The second edge region Eb is located on the second bus bar 17 side.

[0053] A pair of mass addition films 9 are provided in a pair of edge regions. Specifically, one of the pair of mass addition films 9 is provided in the first edge region Ea. The other of the pair of mass addition films 9 is provided in the second edge region Eb. Each mass addition film 9 has a strip shape. More specifically, in a plan view, each mass addition film 9 is continuously provided to overlap with a plurality of electrode fingers and the region between the electrode fingers. In this specification, the term "plan view" refers to a view from the direction equivalent to Figure 2 The elastic wave device is viewed from the upper direction. Figure 2 For example, between the piezoelectric layer 6 side and the dielectric film 8 side, the dielectric film 8 side is at an upper position.

[0054] like Figure 1 As shown, by providing the mass added film 9 in each edge region, the sound velocity in each edge region becomes lower than the sound velocity in the central region C. Thus, a low sound velocity region is formed in each edge region. In addition, the so-called low sound velocity region refers to a region where the sound velocity is lower than the sound velocity in the central region C.

[0055] The central region C and a pair of low sound velocity regions are arranged in this order from the inside to the outside in the extending direction of the electrode finger portion. This allows a piston mode to be established and the transverse mode to be suppressed.

[0056] In the elastic wave device 1, Ta is used as the material of the mass added film 9. 2 O 5 However, the material of the mass added film 9 is not limited to the above.

[0057] exist Figure 3 , a cross section in the first edge region Ea is shown. In the first edge region Ea, the mass addition film 9 is provided between the IDT electrode 7 and the dielectric film 8. Although not shown, the mass addition film 9 is also provided between the IDT electrode 7 and the dielectric film 8 in the second edge region Eb. However, the IDT 27 does not include the mass addition film 9.

[0058] In addition, the first electrode finger 18 and the second electrode finger 19 of the IDT electrode 7 have a first surface 7a, a second surface 7b and a side surface 7c, respectively. The first surface 7a and the second surface 7b are opposite to each other. Of the first surface 7a and the second surface 7b, the second surface 7b is located on the piezoelectric layer 6 side. The side surface 7c is connected to the first surface 7a and the second surface 7b. In the present embodiment, the side surface 7c extends obliquely relative to the normal direction of the second surface 7b. However, the side surface 7c may also extend parallel to the normal direction of the second surface 7b.

[0059] The dielectric film 8 is provided over the first surface 7a and the side surface 7c of the electrode finger. In addition, in each edge region, the dielectric film 8 is indirectly provided on the electrode finger via the mass addition film 9. The dielectric layer 27b in the electrode finger portion of the IDT 27 is a portion of the dielectric film 8 that is directly or indirectly provided on the first surface 7a of the electrode finger.

[0060] In the following, the wavelength specified by the electrode finger pitch is set to λ. The so-called electrode finger pitch refers to the distance between the centers of adjacent electrode fingers in a direction perpendicular to the electrode finger extension direction. The duty cycle of IDT27 is set to d. In addition, the duty cycle d of IDT27 is the same as the duty cycle of IDT electrode 7. More specifically, the duty cycle d of IDT27 is a duty cycle based on the second surface 7b of each electrode finger in the IDT electrode 7. The value obtained by dividing the dimension of the mass addition film 9 along the electrode finger extension direction by the wavelength λ is set as the wavelength ratio width W.

[0061] The value obtained by dividing the product of the density and thickness of any layer by the density of Al and the wavelength λ is expressed as a percentage and is set as the Al-converted normalized thickness of the layer. The total Al-converted normalized thickness of the electrode finger layer is set as the Al-converted normalized thickness of the electrode finger, i.e., T IDT[%] For example, let n be an arbitrary natural number, let k be a natural number of 1≤k≤n, and let the electrode finger portion have n electrode finger layers. When the density of the k-th electrode finger layer from the piezoelectric layer 6 side is ρ k , set the thickness to t k , set the normalized thickness of Al to T k [%], let the density of Al be ρ Al When the Al-converted normalized thickness T of each electrode finger layer is k is {(ρ k ·t k ) / (ρ Al ·λ)}×100[%]. In addition, when the number of significant figures is set to 3, ρ Al 2.69g / cm 3 . Al-converted normalized thickness T of the electrode finger IDT T IDT =Σ{(ρ k ·T k ) / (ρ Al ·λ)}×100[%] (1≤k≤n).

[0062] When the Al-converted normalized thickness of the mass added film 9 is set to T m [%], the Al of the mass added film 9 is converted into normalized thickness T m Al-converted normalized thickness T relative to the electrode finger IDT The value obtained by dividing the thickness ratio by 3.15 is set as T R [%], T R = (1 / 3.15) × (T m / T IDT )×100[%]. In more detail, the Al-converted normalized thickness T of the mass added film 9 is m This is equivalent to substituting the density and thickness of the mass added film 9 into the Al-converted normalized thickness T of the electrode finger layer. k {(ρ k ·t k ) / (ρ Al ·λ)}×100 k and thickness t k The above "3.15" is the density of tantalum oxide ρ Ta2O5 Relative to the density of Al Al That is, ρ Ta2O5 / ρ Al =3.15.

[0063] The elastic wave device 1 of the present embodiment has at least one of the first feature and the second feature. In the xy plane, the wavelength ratio width W and the thickness ratio T are represented.R More specifically, in the xy plane, let the value of x be equivalent to the value of the wavelength ratio width W. Let the value of y be equivalent to the thickness ratio T R The first feature is as follows. 1) The piezoelectric layer 6 contains lithium tantalate. 2) The resonance frequency of the elastic wave device 1 is higher than 1 GHz. 3) The wavelength ratio width W and thickness ratio T R It is a value within the range of an ellipse represented by setting θ to be greater than or equal to 0° and less than 360° in the following Expressions 1 and 2, and the inside of the ellipse.

[0064] x=0.19×cos(-5.5°)×cosθ-0.021×sin(-5.5°)×sinθ+0.0146×T IDT 2 -0.229×T IDT +1.5611+0.4×(d-0.55) Formula 1

[0065] y=0.19×sin(-5.5°)×cosθ+0.021×cos(-5.5°)×sinθ+10.15 Equation 2

[0066] The second feature is as follows: 1) The piezoelectric layer 6 contains lithium tantalate. 2) The resonance frequency of the elastic wave device 1 is higher than 1 GHz. 3) The wavelength-to-width W and thickness ratio T of the mass addition film 9 are R In other words, the wavelength ratio width W is 0.88×{0.0101×T IDT 2 -0.1677×T IDT +1.3201+0.4×(d-0.55)}≤W≤1.12×{0.0101×T IDT 2 -0.1677×T IDT +1.3201+0.4×(d-0.55)}. Thickness ratio T R 0.88×10.7≤T R ≤1.12×10.7.

[0067] Since elastic wave device 1 has at least one of the first and second characteristics, transverse modes can be suppressed more reliably. More specifically, elastic wave device 1 can more reliably suppress the magnitude of ripples caused by transverse modes in frequency characteristics to 1 dB or less. The details are described below.

[0068] In addition, the transverse mode includes various modes such as the first to eleventh order. According to the present invention, the magnitude of the largest ripple among the ripples caused by the transverse mode in the frequency characteristic can be suppressed to 1 dB or less more reliably.

[0069] The inventors of the present invention have found that by converting the Al of the mass added film 9 into a normalized thickness T m Al-converted normalized thickness T relative to the electrode finger IDT The thickness ratio is divided by 3.15 to get the T R The relationship between the wavelength and the width W of the mass addition film 9 is set to a given relationship, so that the transverse mode can be suppressed. In the elastic wave device, the wavelength-to-width W and the thickness ratio T that can suppress the size of the ripple caused by the transverse mode in the frequency characteristics to less than 1 dB are derived. R The design parameters of the elastic wave device involved in this derivation are as follows.

[0070] Piezoelectric layer: Material…LiTaO 3

[0071] IDT metal layer: Layer structure…Ti layer / Al layer / Ti layer from the piezoelectric layer side, thickness…t from the piezoelectric layer side 1 =12nm / t 2 =100nm / t 3 =4nm

[0072] IDT's dielectric layer: Material…SiO 2 , thickness…t 5 =30nm

[0073] Dielectric film: Material…SiO 2 、Thickness…30nm

[0074] Wavelength λ…1.8μm, 2.2μm or 2.6μm

[0075] Duty cycle d…0.5, 0.55 or 0.6

[0076] Al-converted normalized thickness T of the electrode finger IDT …5.22%, 6.17% or 7.54%

[0077] Material of quality additional film: Ta 2 O 5

[0078] The wavelength ratio width W of the mass added film was changed in the range of 0.4 to 1.1 in increments of 0.02.

[0079] Thickness ratio T R : Changes in 0.2% increments within the range of 6.5% to 14.5%.

[0080] In addition, the normalized thickness T is calculated according to Al IDT , the thickness of the mass-added film is changed, thereby changing the thickness ratio T RAs described above, whenever the thickness ratio T R When the width W is changed compared to the wavelength, the return loss is measured and the size of the ripple caused by the transverse mode is obtained.

[0081] Figure 4 is the Al-converted normalized thickness T of the electrode finger portion. IDT When the duty ratio d is 7.54% and the duty ratio d is 0.55, the magnitude of the ripple caused by the transverse mode becomes 1 dB or 0.1 dB, and the wavelength-to-width W and thickness ratio T of the mass-added film are R The relationship diagram of Figure 4 In the xy plane, the value of x corresponds to the value of the wavelength ratio width W. The value of y corresponds to the thickness ratio T R In the following Figures 5 to 8 The same is true in Chinese.

[0082] exist Figure 4 In the middle, the solid line B 1 The wavelength-to-width ratio W and the thickness ratio T at which the magnitude of the ripple caused by the transverse mode in the frequency characteristics of the elastic wave device becomes 1 dB are shown. R The combination of 1 The wavelength ratio width W and thickness ratio T within the enclosed range R In the case of the combination of , the size of the ripple caused by the transverse mode becomes less than 1dB.

[0083] exist Figure 4 In FIG. 1 , an ellipse D represented by equations 1 and 2 is shown. The ellipse D is located within the solid line B. 1 Moreover, the wavelength ratio width W and thickness ratio T R The first feature is that φ is a value within the range of ellipse D and the inner side of ellipse D. Therefore, elastic wave device 1 has the first feature, and thus the magnitude of the ripple caused by the transverse mode can be more reliably suppressed to 1 dB or less.

[0084] However, if the Al-converted normalized thickness T of the electrode finger IDT The conditions for the ripple caused by the transverse mode to be less than 1 dB are different from those for the duty ratio d. IDT Unlike the duty ratio d, the conditions for the ripple caused by the transverse mode to be less than 1 dB were obtained in each case. The ellipse derived from this is the ellipse D represented by equations 1 and 2. Therefore, the wavelength ratio width W and thickness ratio T R The Al-converted normalized thickness T of the electrode finger portion is 1. IDT Regardless of the duty ratio d, the magnitude of the ripple caused by the transverse mode can be reduced to 1 dB or less.

[0085] exist Figure 4 The range F is shown in FIG. The range F is located between the solid line B 1 Moreover, the wavelength ratio width W and thickness ratio T R The value is within the range F, which is the above-mentioned feature 2. Therefore, since elastic wave device 1 has the second feature, the magnitude of the ripple caused by the transverse mode can be suppressed to 1 dB or less more reliably.

[0086] More specifically, the wavelength ratio width W and thickness ratio T at which the transverse mode is most suppressed R The range of ±12% is the range F. The wavelength ratio width W and thickness ratio T where the transverse mode is most suppressed R Normalized thickness T calculated from Al conversion of electrode fingers IDT Therefore, the Al-converted normalized thickness T of the electrode finger is IDT Different from the duty ratio d, the wavelength ratio width W and thickness ratio T at which the ripple caused by the transverse mode is most suppressed are found in each case. R .

[0087] The wavelength ratio width W in the range F derived from this is 0.88×{0.0101×T IDT 2 -0.1677×T IDT +1.3201+0.4×(d-0.55)}≤W≤1.12×{0.0101×T IDT 2 -0.1677×T IDT +1.3201+0.4×(d-0.55)}. The thickness ratio T derived as above R 0.88×10.7≤T R ≤1.12×10.7, is a fixed range. Therefore, by the wavelength ratio width W and thickness ratio T R is within the range F, so regardless of the Al-converted normalized thickness T of the electrode finger portion IDT Regardless of the duty ratio d, the magnitude of the ripple caused by the transverse mode can be reduced to 1 dB or less.

[0088] In addition, Figure 4 In the middle, the solid line B 0.1 The wavelength ratio W and thickness ratio T at which the size of the ripple caused by the transverse mode becomes 0.1 dB are shown. R The combination of wavelength ratio width W and thickness ratio T R The value of is given by the solid line B 0.1 The value within the range surrounded by , can suppress the size of the ripple caused by the transverse mode to less than 0.1dB. Figure 4 As shown, the wavelength ratio width W and thickness ratio T of the quality-added film 9 R In the case of range F, the wavelength ratio width W and thickness ratio T R is close to the solid line B 0.1 The value of 0.1 Therefore, when elastic wave device 1 has the above-described feature 2, the transverse mode can be suppressed more reliably and effectively.

[0089] Depend on Figures 5 to 8 The Al-converted normalized thickness T of the electrode finger is shown. IDT and the duty cycle d is Figure 4 Except for the conditions in Figures 5 to 8 The solid line B is also shown. 1 , solid line B 0.1 , ellipse D and range F.

[0090] Figure 5 is the Al-converted normalized thickness T of the electrode finger portion. IDT When the duty ratio d is 6.17% and the duty ratio d is 0.55, the magnitude of the ripple caused by the transverse mode becomes 1 dB or 0.1 dB, and the wavelength-to-width W and thickness ratio T of the mass-added film are R Graph of the relationship. Figure 6 is the Al-converted normalized thickness T of the electrode finger portion. IDT When the duty ratio d is 5.22% and the duty ratio d is 0.55, the magnitude of the ripple caused by the transverse mode becomes 1 dB or 0.1 dB, and the wavelength-to-width W and thickness ratio T of the mass-added film are R Graph of the relationship. Figure 7 is the Al-converted normalized thickness T of the electrode finger portion. IDT When the duty ratio d is 6.17% and the ripple caused by the transverse mode is 0.5, the wavelength-to-width W and thickness ratio T of the mass-added film are 1 dB or 0.1 dB. R Graph of the relationship. Figure 8 is the Al-converted normalized thickness T of the electrode finger portion. IDT When the duty ratio d is 6.17% and the ripple caused by the transverse mode is 0.6, the wavelength-to-width W and thickness ratio T of the mass-added film are 1 dB or 0.1 dB. R Graph of the relationship.

[0091] like Figures 5 to 8 As shown, the wavelength ratio width W of the mass-added film 9 is calculated by taking the value of x as the value and the thickness ratio T as the value of y as the value. RThe ripple caused by the transverse mode can be more reliably suppressed to 1 dB or less by becoming a value within the range of ellipse D and the inner side of ellipse D. As described above, ellipse D is an ellipse represented by setting θ to be greater than 0° and less than 360° in equations 1 and 2.

[0092] Or, by the wavelength ratio width W and thickness ratio T R The value within the range F can more reliably suppress the magnitude of the ripple caused by the transverse mode to be less than 1 dB. Specifically, the wavelength ratio width W is 0.88×{0.0101×T IDT 2 -0.1677×T IDT +1.3201+0.4×(d-0.55)}≤W≤1.12×{0.0101×T IDT 2 -0.1677×T IDT +1.3201+0.4×(d-0.55)}. Thickness ratio T R 0.88×10.7≤T R ≤1.12×10.7 is sufficient.

[0093] In addition, Figures 4 to 8 In the conditions shown, strictly speaking, the wavelength ratio width W and thickness ratio T of the mass-added film 9 are R The transverse mode is most suppressed when the value is as follows. Based on these results, the range F is derived.

[0094] T IDT =7.54%, d=0.55; W=0.62, T R =10.7%

[0095] T IDT =6.17%, d=0.55; W=0.66, T R =10.7%

[0096] T IDT =5.22%, d=0.55; W=0.72, T R =10.7%

[0097] T IDT =6.17%, d=0.5; W=0.64, T R =10.7%

[0098] T IDT =6.17%, d=0.6; W=0.68, T R =10.7%

[0099] The elastic wave device according to the present invention can be used as an elastic wave resonator of a filter device, for example. In the elastic wave device 1 of the present embodiment, the transverse mode can be suppressed more reliably. Thus, the ripple in the frequency characteristics of the filter device can be suppressed more reliably. The details are described below.

[0100] Fig. 9 (a) is a diagram showing that ripples are generated in the attenuation frequency characteristics of the filter device. Fig. 9 (b) is shown by Fig. 9 (a) is a diagram showing the attenuation-frequency characteristics and the impedance-frequency characteristics of an elastic wave resonator used in a filter device. Fig. 9 (c) is shown by Fig. 9 (b) is a graph showing the impedance-frequency characteristics of the return loss of the elastic wave resonator.

[0101] like Fig. 9 As shown in (a) of FIG. 1 , multiple ripples are generated in the attenuation frequency characteristics of the filter device. In addition, multiple ripples are generated in the passband of the filter device. At the frequencies where these ripples are generated, Fig. 9 As shown in (b), ripples are also generated in the impedance frequency characteristics of the elastic wave resonator. Therefore, it can be seen that the unnecessary waves generated in the elastic wave resonator used in the filter device cause ripples to be generated in the attenuation frequency characteristics of the filter device. In addition, Fig. 9 The multiple useless waves shown in (b) are transverse modes. Fig. 9 The return loss of the elastic wave resonator shown in (c) is larger than the ripple caused by the transverse mode. Fig. 9 The larger the ripple in the filter device shown in (a).

[0102] The following is a more detailed description of the relationship between the ripples in the frequency characteristics of the elastic wave resonator and the filter device. A plurality of elastic wave resonators and a plurality of filter devices are prepared. In each elastic wave resonator, the size of the ripple caused by the transverse mode, which is the return loss, is adjusted. Thus, the size of the ripple is made different between each elastic wave resonator. Each filter device includes one of these elastic wave resonators and other elastic wave resonators. In addition, the configuration of the elastic wave resonator whose ripple size is adjusted in the filter device is set to two types. Hereinafter, the elastic wave resonator set to one configuration is set to the first elastic wave resonator. The elastic wave resonator set to another configuration is set to the second elastic wave resonator. Specifically, the first elastic wave resonator is a series arm resonator in the filter device. The second elastic wave resonator is a parallel arm resonator in the filter device.

[0103] Fig.10This is a diagram showing the relationship between the magnitude of the ripple, which is the return loss in the first elastic wave resonator, and the magnitude of the ripple in the attenuation frequency characteristic of the filter device. Fig.11 This is a diagram showing the relationship between the magnitude of the ripple, which is the return loss in the second elastic wave resonator, and the magnitude of the ripple in the attenuation frequency characteristic of the filter device.

[0104] Fig.10 The plotted points in show the relationship between the magnitude of the ripple in the return loss of each first elastic wave resonator and the magnitude of the ripple in the attenuation frequency characteristic of each filter device. Based on these plotted points, the relationship between the magnitude of the ripple in the frequency characteristic of the first elastic wave resonator and the filter device is derived. Fig.10 The solid straight line in FIG. 1 shows this relationship.

[0105] on the other hand, Fig.10 The dashed-dotted straight line in is a straight line that passes through any plotted point and has the maximum intercept when the slope is the same as that of the solid straight line. The dashed-dotted straight line shows a relationship in which the ripple in the attenuation frequency characteristic of the filter device is maximized relative to the ripple as the return loss in the first elastic wave resonator.

[0106] Here, in the filter device, the magnitude of the ripple in the attenuation frequency characteristic is often required to be less than 0.5 dB. Fig.10 According to the relationship shown by the dashed-dotted straight line in , by making the magnitude of the ripple as the return loss in the first elastic wave resonator 1.8 dB or less, the magnitude of the ripple in the attenuation frequency characteristic of the filter device can be made 0.5 dB or less.

[0107] on the other hand, Fig.11 The straight solid line in shows the relationship between the second elastic wave resonator and the magnitude of the ripple in the frequency characteristics of the filter device. Fig.11 The slope of the solid line in Fig.10 As described above, the relationship between the magnitude of the ripples of the elastic wave resonator and the filter device varies depending on the arrangement of the elastic wave resonator and the like. Fig.11 The dashed-dotted straight line in shows a relationship in which the ripple in the attenuation frequency characteristic of the filter device is assumed to be maximum with respect to the ripple as the return loss in the second elastic wave resonator. According to the relationship shown by the dashed-dotted straight line, the size of the ripple in the attenuation frequency characteristic of the filter device can be made 0.5 dB or less by making the size of the ripple as the return loss in the second elastic wave resonator 1 dB or less.

[0108] According to the above, by making the size of the ripple in the frequency characteristic of the elastic wave device used as an elastic wave resonator in the filter device less than 1 dB, the size of the ripple in the attenuation frequency characteristic of the filter device can be more reliably made less than 0.5 dB. As described above, in this embodiment, the size of the ripple caused by the transverse mode can be more reliably suppressed to less than 1 dB. Therefore, when the elastic wave device 1 is used in a filter device, the ripple in the attenuation frequency characteristic of the filter device can also be more reliably suppressed to less than 0.5 dB. Therefore, the degradation of the filter characteristics of the filter device can be suppressed.

[0109] The following is a further description of the structure of this embodiment. Figure 1 As shown, in this embodiment, a pair of gap regions are arranged between the intersection region A and the pair of bus bars. Specifically, the pair of gap regions are the first gap region Ga and the second gap region Gb. The first gap region Ga is located on the first bus bar 16 side. The second gap region Gb is located on the second bus bar 17 side.

[0110] In the first gap region Ga, only the first electrode fingers 18 among the first electrode fingers 18 and the second electrode fingers 19 are provided. Thus, a high-acoustic-velocity region is formed in the first gap region Ga. In addition, the so-called high-acoustic-velocity region refers to a region where the acoustic velocity is higher than the acoustic velocity in the central region C. A high-acoustic-velocity region is also formed in the second gap region Gb.

[0111] The central region C, a pair of low acoustic velocity regions, and a pair of high acoustic velocity regions are arranged in this order from the inside to the outside in the extending direction of the electrode finger. This makes it possible to more reliably suppress the transverse mode.

[0112] In the present embodiment, each mass addition film 9 is provided in each edge region. In addition, the mass addition film 9 may be provided in at least one of the first edge region Ea and the second edge region Eb. However, it is preferred that the mass addition film 9 is provided in both the first edge region Ea and the second edge region Eb. Accordingly, the transverse mode can be suppressed more reliably and effectively.

[0113] like Figure 3 As shown, the mass addition film 9 is provided between the IDT electrode 7 and the dielectric film 8. However, for example, the mass addition film 9, the IDT electrode 7, and the dielectric film 8 may be stacked in this order from the piezoelectric layer 6 side. Alternatively, the IDT electrode 7, the dielectric film 8, and the mass addition film 9 may be stacked in this order from the piezoelectric layer 6 side.

[0114] like Figure 2 As shown in FIG. 1 , piezoelectric substrate 2 of elastic wave device 1 is a multilayer substrate. Examples of materials of each layer in piezoelectric substrate 2 are as follows.

[0115] In this embodiment, LiTaO is used as the material of the piezoelectric layer 6. 3 And other lithium tantalate.

[0116] As the material of the low acoustic velocity film 5, for example, dielectrics such as glass, silicon oxide, silicon oxynitride, lithium oxide, tantalum oxide, or compounds obtained by adding fluorine, carbon, or boron to silicon oxide, or materials containing the above materials as main components can be used. In this specification, the so-called main component refers to a component that accounts for more than 50wt%. The above-mentioned main component material can also exist in any state of single crystal, polycrystalline, and amorphous, or in a state of mixing them.

[0117] As described above, in the present embodiment, the high-acoustic-velocity material layer is a high-acoustic-velocity film 4. As the high-acoustic-velocity material, for example, piezoelectrics such as aluminum nitride, lithium tantalate, lithium niobate, and 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), and diamond, or semiconductors such as silicon, or materials containing the above materials as main components can also be used. In addition, the above-mentioned spinel contains aluminum compounds containing one or more elements selected from Mg, Fe, Zn, Mn, etc. and oxygen. As examples of the above-mentioned spinel, MgAl 2 O 4 、FeAl 2 O 4 、ZnAl 2 O 4 、MnAl 2 O 4 .

[0118] As the material of the supporting substrate 3, for example, piezoelectrics such as aluminum nitride, lithium tantalate, lithium niobate, and quartz, ceramics such as alumina, sapphire, magnesium oxide, silicon nitride, silicon carbide, zirconium oxide, cordierite, mullite, steatite, and forsterite, dielectrics such as diamond and glass, semiconductors such as silicon and gallium nitride, or resins, or materials containing the above materials as the main components can be used.

[0119] The high-acoustic-velocity film 4, which is a high-acoustic-velocity material layer, the low-acoustic-velocity film 5, 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.

[0120] In addition, the stacked structure of the piezoelectric substrate is not limited to the above. For example, the piezoelectric substrate can also be a stacked substrate of a supporting substrate, a high acoustic velocity film, and a piezoelectric layer. Alternatively, the high acoustic velocity material layer can also be a high acoustic velocity supporting substrate. In this case, the piezoelectric substrate can also be a stacked substrate of a high acoustic velocity supporting substrate, a low acoustic velocity film, and a piezoelectric layer, or a stacked substrate of a high acoustic velocity supporting substrate and a piezoelectric layer. In these cases, the energy of the elastic wave can also be effectively confined on the piezoelectric layer side.

[0121] Table 1 shows examples of metal materials and dielectric materials, and the density of each material. Figure 3 The metal layer 27a in the IDT 27 shown may be made of the metal listed in Table 1. The dielectric layer 27b may be made of the dielectric listed in Table 1. The mass-added film 9 may be made of the dielectric listed in Table 1. The metal material used for the metal layer 27a, the dielectric layer 27b, or the dielectric material used for the mass-added film 9 may contain a small amount of a different material. For example, the Al layer may contain a small amount of Cu.

[0122] [Table 1]

[0123]

[0124] The density of the material of the mass adding film 9 is preferably higher than that of the dielectric layer 27 b of the electrode finger portion. This allows the thickness of the mass adding film 9 to be thinner than that of the dielectric film 8. This allows the mass adding film 9 to be more reliably covered by the dielectric film 8.

[0125] For example, by trimming the surface of the dielectric film 8 and adjusting the thickness of the dielectric film 8, the frequency of the elastic wave device 1 can be adjusted. In the above structure, the mass addition film 9 can be more reliably covered by the dielectric film 8. Therefore, when trimming the dielectric film 8, the mass addition film 9 can be prevented from being trimmed. Therefore, the trimming can be prevented from affecting the frequency of the elastic wave device 1. Figure 1 The difference between the acoustic velocity in the central region C and the acoustic velocity in the pair of edge regions shown is affected. Therefore, the transverse mode can be appropriately suppressed.

[0126] When the dimension of the intersection region A along the electrode finger extension direction is defined as the intersection width, the intersection width is preferably 10λ or more. In this case, the transverse mode can be more reliably and appropriately suppressed. In addition, the intersection width is preferably 30λ or less. This can suppress the size of the elastic wave device 1.

[0127] exist Figure 1In the example shown, the end edge portion on the first bus bar 16 side of the mass addition film 9 located in the first edge region Ea overlaps with the front end of the second electrode finger 19 in a plan view. However, the end edge portion on the first bus bar 16 side of the mass addition film 9 located in the first edge region Ea may not overlap with the front end of the second electrode finger 19 in a plan view. In this case, the end edge portion on the first bus bar 16 side of the mass addition film 9 may be located in the first edge region Ea. Specifically, the distance in the electrode finger extension direction between the end edge portion on the first bus bar 16 side of the mass addition film 9 located in the first edge region Ea and the front end of the second electrode finger 19 in a plan view is preferably less than 0.1λ.

[0128] exist Figure 1 In the example shown, the end edge portion on the second bus bar 17 side of the mass addition film 9 located in the second edge region Eb overlaps with the front end of the first electrode finger 18 in a plan view. However, the end edge portion on the second bus bar 17 side of the mass addition film 9 located in the second edge region Eb may not overlap with the front end of the first electrode finger 18 in a plan view. In this case, the end edge portion on the second bus bar 17 side of the mass addition film 9 may be located in the second edge region Eb. Specifically, the distance in the electrode finger extension direction between the end edge portion on the second bus bar 17 side of the mass addition film 9 located in the second edge region Eb and the front end of the first electrode finger 18 in a plan view is preferably less than 0.1λ.

[0129] Furthermore, the preferred structures, the structure of the piezoelectric substrate, the structure of the mass added film, and the structure of the IDT listed in the description of the first embodiment can also be applied to structures of the present invention other than the first embodiment.

[0130] Here, the inventors of the present invention have conducted intensive research and found that the transverse mode can be suppressed by the resonant frequency of the elastic wave device, the material of the piezoelectric layer, the thickness and duty ratio of the electrode finger, and the wavelength ratio width W and thickness ratio T of the mass added film. R The relationship is different.

[0131] As described above, in the first embodiment, the piezoelectric layer 14 includes lithium tantalate. Furthermore, the resonance frequency of the elastic wave device 1 is higher than 1 GHz. In this case, the wavelength ratio width W and the thickness ratio T R The value may be within the range of the ellipse and the inner side of the ellipse represented by setting θ to be greater than 0° and less than 360° in the above formula 1 and formula 2. Alternatively, the wavelength ratio width W and thickness ratio T R It only needs to be within the above range F. According to this, the transverse mode can be suppressed more reliably.

[0132] Furthermore, the following examples are given in the second and third embodiments in which the piezoelectric layer includes lithium tantalate and the resonance frequency of the elastic wave device is less than 1 GHz, and in which the piezoelectric layer includes lithium niobate. In addition, the stacked structure in the second and third embodiments is the same as the stacked structure in the first embodiment. Therefore, when describing the second and third embodiments, the figure numerals and drawings used in the description of the first embodiment are used.

[0133] The second embodiment is different from the first embodiment in that the resonant frequency of the elastic wave device is 1 GHz or less. Figure 2 The piezoelectric substrate 2 and IDT 27 are shown. In addition, the piezoelectric substrate 2 only needs to have a high acoustic velocity material layer and a piezoelectric layer 6. Figure 1 As shown, the mass addition film 9 is provided in each of the first edge region Ea and the second edge region Eb. However, the mass addition film 9 may be provided in at least one of the first edge region Ea and the second edge region Eb.

[0134] The piezoelectric layer 6 includes, for example, LiTaO 3 The elastic wave device according to the second embodiment can be suitably used in, for example, a low-band (LB) filter device or the like.

[0135] The second embodiment is characterized by the following structures. 1) The piezoelectric layer 6 contains lithium tantalate. 2) The resonance frequency of the elastic wave device is 1 GHz or less. 3) The wavelength ratio width W and thickness ratio T R The value is a value within the range of an ellipse and the inner side of the ellipse represented by setting t to be greater than 0° and less than 360° in the following formulas 3 and 4. In addition, it is pointed out in advance that t in formulas 3 and 4 is an angle and is different from the thickness t k different.

[0136] x=0.16×cost×cos(1.3°)-25.5×sint×sin(1.3°)+2.22-2.54×d+2.06×d 2 Formula 3

[0137] y=0.16×cost×sin(1.3°)+25.5×cost×sin(1.3°)+25.5-0.033×(T IDT -7.83) Formula 4

[0138] More specifically, the inventors of the present invention derived the wavelength-to-width ratio W and thickness ratio T of the mass-added film in an elastic wave device having a resonance frequency of 1 GHz or less. RThe relationship between the magnitude of the ripples caused by the transverse mode in the frequency characteristics The design parameters of the elastic wave device involved in this derivation are as follows.

[0139] Piezoelectric layer: Material…LiTaO 3

[0140] IDT metal layer: Layer structure…Ti layer / Al layer / Ti layer from the piezoelectric layer side, thickness…t from the piezoelectric layer side 1 =30nm / t 2 =415nm / t 3 =4nm

[0141] IDT's dielectric layer: Material…SiO 2 , thickness…t 5 =30nm

[0142] Dielectric film: Material…SiO 2 , thickness…50nm

[0143] Wavelength λ…5.3μm

[0144] The duty ratio d... changes in 0.05 increments within a range of 0.4 to 0.8.

[0145] Al-converted normalized thickness T of the electrode finger IDT …3.77% or 7.83%

[0146] Material of quality additional film: Ta 2 O 5

[0147] The wavelength ratio width W of the mass added film is changed in the range of 0.8 to 2 in increments of 0.1.

[0148] Thickness ratio T R : Changes in 3% increments within the range of 10% to 40%.

[0149] In addition, the normalized thickness T is calculated according to Al IDT , the thickness of the mass-added film is changed, thereby changing the thickness ratio T R As described above, whenever the thickness ratio T R When the width W is changed compared to the wavelength, the return loss is measured and the size of the ripple caused by the transverse mode is obtained.

[0150] Fig.12 The Al-converted normalized thickness T of the electrode finger portion when the piezoelectric layer includes lithium tantalate and the resonance frequency is 1 GHz or less is shown. IDTWhen the duty ratio d is 7.83% and the ripple caused by the transverse mode is 1 dB or 0.3 dB, the wavelength-to-width W and thickness ratio T of the mass-added film are R The relationship diagram of Fig.12 In the xy plane, the value of x corresponds to the value of the wavelength ratio width W. The value of y corresponds to the thickness ratio T R The value of Fig.12 In the following, lithium tantalate is recorded as LT and the resonance frequency is recorded as fr. Fig.13 and Fig.14 The same is true in Chinese.

[0151] exist Fig.12 In FIG. 1 , a solid ellipse Da represented by equations 3 and 4 is shown. Specifically, the ellipse Da is the wavelength ratio width W of the mass added film as the value of x, and the thickness ratio T as the value of y. R The ellipse Da is represented by setting t to be greater than 0° and less than 360° in the above-mentioned equations 3 and 4. Fig.12 The size of the ripple caused by the transverse mode in the (x, y) becomes 1dB and roughly overlaps. Fig.12 In FIG. 1 , the ellipse Da shows (x, y) where the magnitude of the ripple becomes 1 dB.

[0152] Therefore, the wavelength ratio width W is the value of x, and the thickness ratio T is the value of y. R The transverse mode can be suppressed more reliably by making the value within the range of the ellipse Da and the inner side of the ellipse Da. More specifically, the magnitude of the ripple caused by the transverse mode can be suppressed to 1 dB or less more reliably.

[0153] However, if the Al-converted normalized thickness T of the electrode finger IDT The conditions for the ripple caused by the transverse mode to be less than 1 dB are different from those for the duty ratio d. IDT Different from the duty ratio d, the condition for the ripple caused by the transverse mode to be less than 1 dB was obtained in each case. The ellipse derived from this is the ellipse Da represented by equations 3 and 4. Therefore, the wavelength ratio width W and thickness ratio T R The Al-converted normalized thickness T of the electrode finger portion is 1.33mm, which is within the range of the ellipse Da and the inner side of the ellipse Da. IDT Regardless of the duty cycle d, the ripple caused by the transverse mode can be kept below 1 dB. Fig.13 and Fig.14 This example is shown.

[0154] Fig.13The Al-converted normalized thickness T of the electrode finger portion when the piezoelectric layer includes lithium tantalate and the resonance frequency is 1 GHz or less is shown. IDT When the duty ratio d is 3.77% and the ripple caused by the transverse mode is 1 dB or 0.3 dB, the wavelength-to-width W and thickness ratio T of the mass-added film are R Graph of the relationship. Fig.14 The Al-converted normalized thickness T of the electrode finger portion when the piezoelectric layer includes lithium tantalate and the resonance frequency is 1 GHz or less is shown. IDT When the duty ratio d is 7.83% and the ripple caused by the transverse mode is 1 dB or 0.3 dB, the wavelength-to-width W and thickness ratio T of the mass-added film are R Graph of the relationship.

[0155] exist Fig.13 and Fig.14 , the Al-converted normalized thickness T of the electrode finger portion is shown. IDT or duty cycle d and Fig.12 The results for different situations are shown. Fig.13 and Fig.14 In FIG. 1 , an ellipse Da represented by setting t to be greater than or equal to 0° and less than 360° in Formula 3 and Formula 4 is also shown. Fig.13 The ellipse Da shown is within the range of the above design parameters. Fig.13 The magnitude of the ripple caused by the transverse mode in the (x, y) becomes 1dB and roughly overlaps. Fig.14 The ellipse Da shown is within the range of the above design parameters. Fig.14 The size of the ripple caused by the transverse mode in the (x, y) becomes 1dB and roughly overlaps. Fig.13 and Fig.14 In FIG. 1 , the ellipse Da shows (x, y) where the magnitude of the ripple becomes 1 dB.

[0156] Therefore, in Fig.13 and Fig.14 In the case shown, the wavelength ratio width W of the mass-added film is calculated by taking the value of x and the thickness ratio T as the value of y. R The value is within the range of the ellipse Da and the inner side of the ellipse Da, so that the transverse mode can be suppressed more reliably. More specifically, the size of the ripple caused by the transverse mode can be suppressed to less than 1 dB more reliably. In this way, regardless of the Al-converted normalized thickness T of the electrode finger portion IDT Regardless of the duty ratio d, the transverse mode can be suppressed.

[0157] In addition, Fig.12 The dotted ellipse Ha is shown in FIG. The ellipse Ha is within the range of the above design parameters. Fig.12The size of the ripple caused by the transverse mode in the (x, y) is approximately 0.3dB. Fig.12 In the figure, the ellipse Ha shows the (x, y) at which the ripple size becomes 0.3 dB. The ellipse Ha is the ratio of the wavelength to the width W as x and the thickness ratio T as y. R An ellipse represented by setting t to be greater than or equal to 0° and less than 360° in the following Formula 3A and Formula 4A.

[0158] x=0.08×cost×cos(1.3°)-12.8×sint×sin(1.3°)+2.22-2.54×d+2.06×d 2 Formula 3A

[0159] y=0.08×cost×sin(1.3°)+12.8×cost×sin(1.3°)+25.5-0.033×(T IDT -7.83) Formula 4A

[0160] The wavelength ratio width W is the value of x, and the thickness ratio T is the value of y. R By setting the value to be within the range of the ellipse Ha and the inner side of the ellipse Ha, the magnitude of the ripple caused by the transverse mode can be suppressed to 0.3 dB or less more reliably.

[0161] exist Fig.13 and Fig.14 , the ellipse Ha represented by setting t to be greater than or equal to 0° and less than 360° in Formula 3A and Formula 4A is also shown. Fig.13 The ellipse Ha shown is within the range of the above design parameters. Fig.13 The magnitude of the ripple caused by the transverse mode in the (x, y) is approximately 0.3 dB. Fig.14 The ellipse Ha shown is within the range of the above design parameters. Fig.14 The size of the ripple caused by the transverse mode in the (x, y) is approximately 0.3dB. Fig.13 and Fig.14 In FIG. 1 , the ellipse Ha shows (x, y) where the magnitude of the ripple becomes 0.3 dB.

[0162] Therefore, in Fig.13 and Fig.14 In the case shown, the wavelength ratio width W of the mass-added film is calculated by taking the value of x and the thickness ratio T as the value of y. R The value is within the range of the ellipse Ha and the inner side of the ellipse Ha, so that the transverse mode can be suppressed more reliably and effectively. More specifically, the size of the ripple caused by the transverse mode can be suppressed to less than 0.3 dB more reliably. In this way, regardless of the Al-converted normalized thickness T of the electrode finger portionIDT Regardless of the duty cycle d, the transverse mode can be effectively suppressed.

[0163] In addition, Formula 3 and Formula 4, as well as Formula 3A and Formula 4A can be expressed by the following determinant.

[0164] [Mathematical formula 1]

[0165]

[0166] [Mathematical formula 2]

[0167]

[0168] In Formula 3 and Formula 4, in the above determinant, a=0.16, b=25.5, θ=1.3[°]. In Formula 3A and Formula 4A, in the above determinant, a=0.08, b=12.8, θ=1.3[°].

[0169] The elastic wave device of the second embodiment can be appropriately used as an elastic wave resonator, for example, in a low-frequency filter device. In the elastic wave device of the second embodiment, the transverse mode can be more reliably suppressed. Accordingly, the ripple in the frequency characteristics of the filter device can be more reliably suppressed. The details are described below.

[0170] Fig.15 (a) is a diagram showing that ripples occur in the attenuation frequency characteristics of the filter device in the low frequency band. Fig.15 (b) is shown by Fig.15 (a) is a diagram showing the attenuation-frequency characteristics and the impedance-frequency characteristics of an elastic wave resonator used in a filter device. Fig.15 (c) is shown by Fig.15 (b) is a graph showing the impedance-frequency characteristics of the return loss of the elastic wave resonator.

[0171] like Fig.15 As shown in (a) of FIG. 1 , multiple ripples are generated in the attenuation frequency characteristics of the filter device. In addition, multiple ripples are generated in the passband of the filter device. At the frequencies where these ripples are generated, Fig.15 As shown in (b), ripples are also generated in the impedance frequency characteristics of the elastic wave resonator. Therefore, it can be seen that the unnecessary waves generated in the elastic wave resonator used in the filter device cause ripples to be generated in the attenuation frequency characteristics of the filter device. In addition, Fig.15 The multiple unwanted waves generated between the resonant frequency and the antiresonant frequency shown in (b) are transverse modes. Fig.15 The return loss of the elastic wave resonator shown in (c) is larger than the ripple caused by the transverse mode. Fig.15 The ripple in the filter device shown in (a) is more likely to become larger.

[0172] The relationship between the ripple in the frequency characteristics of the elastic wave resonator and the filter device is determined by Fig.10 and Fig.11 The relationship shown is the same.

[0173] As described above, in a filter device, the magnitude of the ripple in the attenuation frequency characteristic is often required to be less than 0.5 dB. Fig.10 According to the relationship shown by the dashed line in FIG, the ripple size of the return loss in the elastic wave resonator is 1.8 dB or less, so that the ripple size in the attenuation frequency characteristic of the filter device can be 0.5 dB or less. Fig.11 According to the relationship shown by the dashed-dotted straight line in , by making the magnitude of the ripple, which is the return loss in the elastic wave resonator, 1 dB or less, the magnitude of the ripple in the attenuation frequency characteristic of the filter device can be made 0.5 dB or less.

[0174] According to the above, by making the size of the ripple in the frequency characteristic of the elastic wave device used as an elastic wave resonator in the filter device less than 1 dB, the size of the ripple in the attenuation frequency characteristic of the filter device can be more reliably made less than 0.5 dB. As described above, in the second embodiment, the size of the ripple caused by the transverse mode can be more reliably suppressed to less than 1 dB. Therefore, when the elastic wave device of the second embodiment is used in the filter device, the ripple in the attenuation frequency characteristic of the filter device can be more reliably suppressed to less than 0.5 dB. Therefore, the degradation of the filter characteristics of the filter device can be suppressed.

[0175] The third embodiment differs from the first embodiment in that Figure 2 The piezoelectric layer 6 shown contains, for example, LiNbO 3 Specifically, the elastic wave device of the third embodiment includes a piezoelectric substrate 2 and an IDT 27. In addition, the piezoelectric substrate 2 may include at least a high acoustic velocity material layer and a piezoelectric layer 6. Figure 1 As shown, the mass addition film 9 is provided in each of the first edge region Ea and the second edge region Eb. However, the mass addition film 9 may be provided in at least one of the first edge region Ea and the second edge region Eb.

[0176] The third embodiment is characterized by having the following structures: 1) The piezoelectric layer 6 contains lithium niobate. 2) The wavelength ratio width W and thickness ratio T RThe value is a value within the range of an ellipse and the inside of the ellipse represented by setting t to be greater than 0° and less than 360° in the following equations 5 and 6. In addition, it is pointed out in advance that t in equations 3 and 4 is an angle and is different from the thickness t k different.

[0177] x=0.22×cost×cos(6°)-3.9×sint×sin(6°)+1.0+0.4×(d-0.5)+0.0022×(T IDT -6.9) Formula 5

[0178] y=0.22×cost×sin(6°)+3.9×cost×sin(6°)+7.9-0.033×(T IDT -6.9) Formula 6

[0179] More specifically, the inventors of the present invention derived the wavelength-to-width ratio W and the thickness ratio T of the mass-added film in an elastic wave device whose piezoelectric layer includes lithium niobate. R The relationship between the magnitude of the ripples caused by the transverse mode in the frequency characteristics The design parameters of the elastic wave device involved in this derivation are as follows.

[0180] Piezoelectric layer: Material…LiNbO 3

[0181] IDT metal layer: Layer structure…Ti layer / Al layer / Ti layer from the piezoelectric layer side, thickness…t from the piezoelectric layer side 1 =12nm / t 2 =100nm / t 3 =4nm

[0182] IDT's dielectric layer: Material…SiO 2 , thickness…t 5 =30nm

[0183] Dielectric film: Material…SiO 2 、Thickness…30nm

[0184] Wavelength λ…1.3μm, 1.45μm or 1.6μm

[0185] Duty cycle d…0.5 or 0.7

[0186] Al-converted normalized thickness T of the electrode finger IDT …7.24% or 7.9%

[0187] Material of quality additional film: Ta 2 O 5

[0188] The wavelength ratio width W of the mass added film was changed in 0.1 increments within a range of 0.6 to 1.3.

[0189] Thickness ratio T R : Changes in 2% increments within the range of 4% to 10%.

[0190] In addition, the normalized thickness T is calculated according to Al IDT , the thickness of the mass-added film is changed, thereby changing the thickness ratio T R As described above, whenever the thickness ratio T R When the width W is changed compared to the wavelength, the return loss is measured and the size of the ripple caused by the transverse mode is obtained.

[0191] Fig.16 : is a graph showing the Al-converted normalized thickness T of the electrode finger portion when the piezoelectric layer includes lithium niobate. IDT When the duty ratio d is 6.9% and the ripple caused by the transverse mode is 1 dB or 0.2 dB, the wavelength-to-width W and thickness ratio T of the mass-added film are R The relationship diagram of Fig.16 In the following, lithium niobate is recorded as LN. Fig.17 and Fig.18 The same is true in Chinese.

[0192] exist Fig.16 In FIG. 5 , a solid line ellipse Db represented by equations 5 and 6 is shown. Specifically, the ellipse Db is the wavelength ratio width W of the mass added film as the value of x, and the thickness ratio T as the value of y. R The ellipse Db is represented by setting t to be greater than 0° and less than 360° in the above-mentioned equations 5 and 6. Fig.16 In the figure, the magnitude of the ripple caused by the transverse mode becomes 1 dB and the (x, y) is roughly overlapped.

[0193] Therefore, the wavelength ratio width W is the value of x, and the thickness ratio T is the value of y. R By making it a value within the range of the ellipse Db and the inner side of the ellipse Db, the transverse mode can be suppressed more reliably. More specifically, the magnitude of the ripple caused by the transverse mode can be suppressed to 1 dB or less more reliably.

[0194] However, if the Al-converted normalized thickness T of the electrode finger IDT The conditions for the ripple caused by the transverse mode to be less than 1 dB are different from those for the duty ratio d. IDTUnlike the duty cycle d, the conditions for the ripple caused by the transverse mode to be less than 1 dB were obtained in each case. The ellipse derived from this is the ellipse Db expressed by equations 5 and 6. Therefore, the wavelength ratio width W and thickness ratio T R The Al-converted normalized thickness T of the electrode finger portion is not affected by the Al-converted normalized thickness T of the electrode finger portion. IDT Regardless of the duty cycle d, the ripple caused by the transverse mode can be kept below 1 dB. Fig.16 and Fig.17 This example is shown.

[0195] Fig.17 : is a graph showing the Al-converted normalized thickness T of the electrode finger portion when the piezoelectric layer includes lithium niobate. IDT When the duty ratio d is 13.7% and the ripple caused by the transverse mode is 0.5, the wavelength-to-width ratio W and thickness ratio T of the mass-added film are 1dB or 0.2dB. R Graph of the relationship. Fig.18 : is a graph showing the Al-converted normalized thickness T of the electrode finger portion when the piezoelectric layer includes lithium niobate. IDT When the duty ratio d is 13.7% and the ripple caused by the transverse mode is 1 dB or 0.2 dB, the wavelength-to-width W and thickness ratio T of the mass-added film are R Graph of the relationship.

[0196] exist Fig.17 and Fig.18 , the Al-converted normalized thickness T of the electrode finger portion is shown. IDT or duty cycle d and Fig.16 The results for different situations are shown. Fig.17 and Fig.18 , an ellipse Db represented by setting t to be greater than or equal to 0° and less than 360° in Expressions 5 and 6 is also shown. Fig.17 The ellipse Db shown is within the range of the above design parameters. Fig.17 The magnitude of the ripple caused by the transverse mode in the (x, y) becomes 1dB and roughly overlaps. Fig.18 The ellipse Db shown is within the range of the above design parameters. Fig.18 The size of the ripple caused by the transverse mode in the (x, y) becomes 1dB and roughly overlaps. Fig.17 and Fig.18 In FIG. 1 , the ellipse Db shows the (x, y) at which the magnitude of the ripple becomes 1 dB.

[0197] Therefore, in Fig.17 and Fig.18In the case shown, the wavelength ratio width W of the mass-added film is calculated by taking the value of x and the thickness ratio T as the value of y. R The value is within the range of the ellipse Db and the inner side of the ellipse Db, so that the transverse mode can be suppressed more reliably. More specifically, the size of the ripple caused by the transverse mode can be suppressed to less than 1 dB more reliably. In this way, regardless of the Al-converted normalized thickness T of the electrode finger portion IDT Regardless of the duty ratio d, the transverse mode can be suppressed.

[0198] In addition, Fig.16 The dotted ellipse Hb is shown in FIG. The ellipse Hb is within the range of the above design parameters. Fig.16 The size of the ripple caused by the transverse mode in the (x, y) is approximately 0.2dB. Fig.16 In the figure, the ellipse Hb shows the (x, y) at which the ripple size becomes 0.2 dB. The ellipse Hb is the ratio of the wavelength to the width W as x and the thickness to the ratio T as y. R An ellipse represented by setting t to be greater than or equal to 0° and less than 360° in the following Formula 5A and Formula 6A.

[0199] x=0.088×cost×cos(6°)-1.56×sint×sin(6°)+1.0+0.4×(d-0.5)+0.0022×(T IDT -6.9) Formula 5A

[0200] y=0.088×cost×sin(6°)+1.56×cost×sin(6°)+7.9-0.033×(T IDT -6.9) Formula 6A

[0201] The wavelength ratio width W is the value of x, and the thickness ratio T is the value of y. R By setting the value to be within the range of the ellipse Hb and the inner side of the ellipse Hb, the magnitude of the ripple caused by the transverse mode can be suppressed to 0.2 dB or less more reliably.

[0202] exist Fig.17 and Fig.18 , an ellipse Hb represented by setting t to be greater than or equal to 0° and less than 360° in Formula 5A and Formula 6A is also shown. Fig.17 The ellipse Hb shown is within the range of the above design parameters. Fig.17 The magnitude of the ripple caused by the transverse mode in the (x, y) is approximately 0.2 dB. Similarly, Fig.18 The ellipse Hb shown is within the range of the above design parameters. Fig.18 The size of the ripple caused by the transverse mode in the (x, y) is approximately 0.2dB. Fig.17 and Fig.18 In FIG. 1 , the ellipse Hb shows (x, y) where the magnitude of the ripple becomes 0.2 dB.

[0203] Therefore, in Fig.17 and Fig.18 In the case shown, the wavelength ratio width W of the mass-added film is calculated by taking the value of x and the thickness ratio T as the value of y. R The value is within the range of the ellipse Hb and the inner side of the ellipse Hb, so that the transverse mode can be suppressed more reliably and effectively. More specifically, the size of the ripple caused by the transverse mode can be suppressed to less than 0.2 dB more reliably. In this way, regardless of the Al-converted normalized thickness T of the electrode finger portion IDT Regardless of the duty cycle d, the transverse mode can be effectively suppressed.

[0204] In addition, Formula 5 and Formula 6, as well as Formula 5A and Formula 6A can be expressed by the following determinant.

[0205] [Mathematical formula 3]

[0206]

[0207] [Formula 4]

[0208]

[0209] In Formula 5 and Formula 6, in the above determinant, a=0.22, b=3.9, θ=6[°]. In Formula 5A and Formula 6A, in the above determinant, a=0.088, b=1.56, θ=6[°].

[0210] The elastic wave device of the third embodiment can be suitably used as an elastic wave resonator, for example, in a filter device. In the elastic wave device of the third embodiment, the transverse mode can be suppressed more reliably. Fig.10 As shown in FIG. 1 , by making the magnitude of the ripple as the return loss in the elastic wave resonator 1.8 dB or less, the magnitude of the ripple in the attenuation frequency characteristic of the filter device can be made 0.5 dB or less. Fig.11 As shown, by making the magnitude of the ripple, which is the return loss in the elastic wave resonator, 1 dB or less, the magnitude of the ripple in the attenuation frequency characteristic of the filter device can be made 0.5 dB or less.

[0211] In the third embodiment, the size of the ripple caused by the transverse mode can be more reliably suppressed to less than 1 dB. Therefore, when the elastic wave device of the third embodiment is used in a filter device, the ripple in the attenuation frequency characteristic of the filter device can be more reliably suppressed to less than 0.5 dB. Therefore, the degradation of the filter characteristics of the filter device can be suppressed.

[0212] Examples of aspects of the elastic wave device according to the present invention are summarized below.

[0213] <1> An elastic wave device comprises: a high-acoustic-velocity material layer; a piezoelectric layer, which is disposed on the high-acoustic-velocity material layer and contains lithium tantalate; and an IDT, which is disposed on the piezoelectric layer and has a plurality of electrode fingers, wherein each of the plurality of electrode fingers contains at least one electrode finger layer, wherein the acoustic velocity of a body wave propagating in the high-acoustic-velocity material layer is higher than the acoustic velocity of an elastic wave propagating in the piezoelectric layer, wherein the direction in which the plurality of electrode fingers extend is set as an electrode finger extension direction, and when the IDT is observed from a direction orthogonal to the electrode finger extension direction, a region in which adjacent electrode fingers overlap each other is a cross region, wherein the cross region has a central region and a region configured to extend between the electrode fingers. The elastic wave device further comprises a pair of edge regions sandwiching the central region in an extending direction of the IDT, the elastic wave device further comprising a mass-added film, the mass-added film being arranged in at least one of the edge regions and being continuously arranged to overlap with the plurality of electrode fingers and the region between the electrode fingers in a plan view, the resonant frequency being higher than 1 GHz, and the value obtained by dividing the product of the density and thickness of any layer by the density of Al and the wavelength λ by a percentage as the Al-converted normalized thickness of the layer as the sum of the Al-converted normalized thicknesses of the electrode finger layers as the Al-converted normalized thickness of the electrode fingers, i.e., T IDT [%], the Al-converted normalized thickness of the mass-added film is set to T m [%], convert the Al of the mass added film into a normalized thickness T m The Al-converted normalized thickness T of the electrode finger portion IDT The value obtained by dividing the thickness ratio by 3.15 is set as T R [%], T R = (1 / 3.15) × (T m / T IDT )×100[%], the duty ratio of the IDT is set to d, the dimension of the mass-added film along the extending direction of the electrode finger is divided by the wavelength λ to be the wavelength ratio width W, the value of x is set to be equivalent to the value of the wavelength ratio width W, and the value of y is set to be equivalent to the thickness ratio T RWhen the value of the wavelength ratio width W and the thickness ratio T in the xy plane is R is a value within the range of an ellipse and the inside of the ellipse represented by setting θ to be greater than or equal to 0° and less than 360° in the following equations 1 and 2,

[0214] x=0.19×cos(-5.5°)×cosθ-0.021×sin(-5.5°)×sinθ+0.0146×T IDT 2 -0.229×T IDT +1.5611+0.4×(d-0.55) Formula 1

[0215] y=0.19×sin(-5.5°)×cosθ+0.021×cos(-5.5°)×sinθ+10.15 Equation 2.

[0216] <2> An elastic wave device comprises: a high-acoustic-velocity material layer; a piezoelectric layer, which is disposed on the high-acoustic-velocity material layer and contains lithium tantalate; and an IDT, which is disposed on the piezoelectric layer and has a plurality of electrode fingers, wherein each of the plurality of electrode fingers contains at least one electrode finger layer, wherein the acoustic velocity of a body wave propagating in the high-acoustic-velocity material layer is higher than the acoustic velocity of an elastic wave propagating in the piezoelectric layer, wherein the direction in which the plurality of electrode fingers extend is set as an electrode finger extension direction, and when the IDT is observed from a direction orthogonal to the electrode finger extension direction, a region in which adjacent electrode fingers overlap each other is a cross region, wherein the cross region has a central region and a region configured to extend between the electrode fingers. The elastic wave device further comprises a pair of edge regions sandwiching the central region in an extending direction of the IDT, the elastic wave device further comprising a mass-added film, the mass-added film being arranged in at least one of the edge regions and being continuously arranged to overlap with the plurality of electrode fingers and the region between the electrode fingers in a plan view, the resonant frequency being higher than 1 GHz, and the value obtained by dividing the product of the density and thickness of any layer by the density of Al and the wavelength λ by a percentage as the Al-converted normalized thickness of the layer as the sum of the Al-converted normalized thicknesses of the electrode finger layers as the Al-converted normalized thickness of the electrode fingers, i.e., T IDT [%], the Al-converted normalized thickness of the mass-added film is set to T m [%], convert the Al of the mass added film into a normalized thickness T m The Al-converted normalized thickness T of the electrode finger portion IDT The value obtained by dividing the thickness ratio by 3.15 is set as T R [%], T R = (1 / 3.15) × (T m / T IDT )×100[%], when the duty ratio of the IDT is set to d and the value obtained by dividing the dimension of the mass addition film along the extension direction of the electrode finger by the wavelength λ is set to the wavelength ratio width W, the wavelength ratio width W of the mass addition film is: 0.88×{0.0101×T IDT 2 -0.1677×T IDT +1.3201+0.4×(d-0.55)}≤W≤1.12×{0.0101×T IDT 2 -0.1677×T IDT +1.3201+0.4×(d-0.55)}, the thickness ratio T R =0.88×10.7≤T R ≤1.12×10.7.

[0217] <3> An elastic wave device comprises: a high-acoustic-velocity material layer; a piezoelectric layer, which is disposed on the high-acoustic-velocity material layer and contains lithium tantalate; and an IDT, which is disposed on the piezoelectric layer and has a plurality of electrode fingers, wherein each of the plurality of electrode fingers contains at least one electrode finger layer, wherein the acoustic velocity of a body wave propagating in the high-acoustic-velocity material layer is higher than the acoustic velocity of an elastic wave propagating in the piezoelectric layer, wherein the direction in which the plurality of electrode fingers extend is set as an electrode finger extension direction, and when the IDT is observed from a direction orthogonal to the electrode finger extension direction, a region in which adjacent electrode fingers overlap each other is a cross region, wherein the cross region has a central region and a region configured to extend between the electrode fingers. The elastic wave device further comprises a pair of edge regions sandwiching the central region in an extending direction of the IDT, the elastic wave device further comprising a mass-added film, the mass-added film being arranged in at least one of the edge regions and being continuously arranged to overlap with the plurality of electrode fingers and the region between the electrode fingers in a plan view, the resonant frequency being 1 GHz or less, and a wavelength defined by the electrode finger pitch of the IDT being set to λ, a value obtained by dividing the product of the density and thickness of any layer by the density of Al and the wavelength λ and expressed as a percentage being set as the Al-converted normalized thickness of the layer, and the sum of the Al-converted normalized thicknesses of the electrode finger layers being set as the Al-converted normalized thickness of the electrode fingers, i.e., T IDT [%], the Al-converted normalized thickness of the mass-added film is set to T m [%], convert the Al of the mass added film into a normalized thickness T m The Al-converted normalized thickness T of the electrode finger portion IDT The value obtained by dividing the thickness ratio by 3.15 is set as T R [%], T R = (1 / 3.15) × (Tm / T IDT )×100[%], the duty ratio of the IDT is set to d, the dimension of the mass-added film along the extending direction of the electrode finger is divided by the wavelength λ to be the wavelength ratio width W, the value of x is set to be equivalent to the value of the wavelength ratio width W, and the value of y is set to be equivalent to the thickness ratio T R When the value of the wavelength ratio width W and the thickness ratio T in the xy plane is R is a value within the range of an ellipse and the inside of the ellipse represented by setting θ to be greater than or equal to 0° and less than 360° in the following equations 3 and 4,

[0218] x=0.16×cost×cos(1.3°)-25.5×sint×sin(1.3°)+2.22-2.54×d+2.06×d 2 Formula 3

[0219] y=0.16×cost×sin(1.3°)+25.5×cost×sin(1.3°)+25.5-0.033×(T IDT -7.83) Formula 4.

[0220] <4> An elastic wave device comprises: a high-acoustic-velocity material layer; a piezoelectric layer, which is arranged on the high-acoustic-velocity material layer and contains lithium niobate; and an IDT, which is arranged on the piezoelectric layer and has a plurality of electrode fingers, wherein the plurality of electrode fingers each contain at least one electrode finger layer, wherein the acoustic velocity of a body wave propagating in the high-acoustic-velocity material layer is higher than the acoustic velocity of an elastic wave propagating in the piezoelectric layer, wherein the direction in which the plurality of electrode fingers extend is set as an electrode finger extension direction, and when the IDT is observed from a direction orthogonal to the electrode finger extension direction, a region in which adjacent electrode fingers overlap each other is a cross region, wherein the cross region has a central region and a region configured as The elastic wave device further comprises a mass-added film in a pair of edge regions sandwiching the central region in the extending direction of the electrode fingers, the mass-added film being provided in at least one of the edge regions and being continuously provided so as to overlap with the plurality of electrode fingers and the region between the electrode fingers in a plan view, wherein a wavelength defined by the electrode finger pitch of the IDT is defined as λ, a value obtained by dividing the product of the density and thickness of any layer by the density of Al and the wavelength λ and expressed as a percentage is defined as the Al-converted normalized thickness of the layer, and the sum of the Al-converted normalized thicknesses of the electrode finger layers is defined as the Al-converted normalized thickness of the electrode fingers, i.e., T. IDT [%], the Al-converted normalized thickness of the mass-added film is set to T m [%], convert the Al of the mass added film into a normalized thickness T mThe Al-converted normalized thickness T of the electrode finger portion IDT The value obtained by dividing the thickness ratio by 3.15 is set as T R [%], T R = (1 / 3.15) × (T m / T IDT )×100[%], the duty ratio of the IDT is set to d, the dimension of the mass-added film along the extending direction of the electrode finger is divided by the wavelength λ to be the wavelength ratio width W, the value of x is set to be equivalent to the value of the wavelength ratio width W, and the value of y is set to be equivalent to the thickness ratio T R When the value of the wavelength ratio width W and the thickness ratio T in the xy plane is R is a value within the range of an ellipse and the inside of the ellipse represented by setting θ to be greater than or equal to 0° and less than 360° in the following equations 5 and 6,

[0221] x=0.22×cost×cos(6°)-3.9×sint×sin(6°)+1.0+0.4×(d-0.5)+0.0022×(T IDT -6.9) Formula 5

[0222] y=0.22×cost×sin(6°)+3.9×cost×sin(6°)+7.9-0.033×(T IDT -6.9) Formula 6.

[0223] <5> exist <1> ~ <4> In the elastic wave device described in any one of the above, the elastic wave device includes a plurality of the mass addition films, and the mass addition films are provided in each of the both edge regions.

[0224] <6> exist <1> ~ <5> In the elastic wave device described in any one of the items, the IDT includes an IDT electrode, and the elastic wave device also has a dielectric film, the dielectric film is arranged on the piezoelectric layer to cover the IDT electrode, and the at least one electrode finger layer of the electrode finger portion includes: a metal layer included in the IDT electrode, and a dielectric layer included in the dielectric film.

[0225] <7> exist <6> In the elastic wave device described above, the mass-added film is provided between the metal layer and the dielectric layer in the edge region.

[0226] <8> exist <7> In the elastic wave device described above, density of the mass addition film is higher than density of the dielectric layer of the electrode finger portion.

[0227] <9> exist <1> ~ <8> In the elastic wave device described in any one of the above, tantalum oxide is used as a material of the mass addition film.

[0228] <10> exist <1> ~ <9> In the elastic wave device described in any one of the above, the high-acoustic-velocity material layer is a high-acoustic-velocity supporting substrate.

[0229] <11> exist <1> ~ <9> In the elastic wave device described in any one of the above, the elastic wave device further includes a supporting substrate, and the high-acoustic-velocity material layer is a high-acoustic-velocity film provided between the supporting substrate and the piezoelectric layer.

[0230] <12> exist <1> ~ <11> In the elastic wave device described in any one of the items, the elastic wave device further includes a low acoustic velocity membrane, the low acoustic velocity membrane is arranged between the high acoustic velocity material layer and the piezoelectric layer, and the acoustic velocity of the bulk wave propagating through the low acoustic velocity membrane is lower than the acoustic velocity of the bulk wave propagating through the piezoelectric layer.

[0231] Description of Reference Numerals

[0232] 1…Elastic wave device

[0233] 2…Piezoelectric substrate

[0234] 3…Support base plate

[0235] 4…High sound velocity membrane

[0236] 5…Low sound velocity membrane

[0237] 6…Piezoelectric layer

[0238] 7…IDT electrode

[0239] 7a, 7b…Side 1, Side 2

[0240] 7c…side

[0241] 8…Dielectric film

[0242] 9…Quality additional film

[0243] 15A, 15B…Reflector

[0244] 16, 17…1st bus bar, 2nd bus bar

[0245] 18, 19…1st electrode finger, 2nd electrode finger

[0246] 27…IDT

[0247] 27a…Metal layer

[0248] 27b…Dielectric layer

[0249] 28, 29 ... first electrode finger portion, second electrode finger portion

[0250] A…Intersection Area

[0251] C…Central Area

[0252] Ea, Eb...1st edge region, 2nd edge region

[0253] Ga, Gb...first gap region, second gap region.

Claims

1. An elastic wave device comprising: High sound velocity material layer; a piezoelectric layer, disposed on the high acoustic velocity material layer, comprising lithium tantalate; and The IDT is provided on the piezoelectric layer and has a plurality of electrode fingers, each of the plurality of electrode fingers includes at least one electrode finger layer. The acoustic velocity of the body wave propagating in the high-acoustic-velocity material layer is higher than the acoustic velocity of the elastic wave propagating in the piezoelectric layer. The direction in which the plurality of electrode fingers extend is defined as an electrode finger extension direction, and when the IDT is observed from a direction orthogonal to the electrode finger extension direction, a region where adjacent electrode fingers overlap each other is a crossing region, and the crossing region includes a central region and a pair of edge regions arranged to sandwich the central region in the electrode finger extension direction. The elastic wave device further includes a mass-added film, the mass-added film being provided in at least one of the edge regions and being continuously provided to overlap with the plurality of electrode fingers and a region between the electrode fingers in a plan view. The resonant frequency is higher than 1GHz. The wavelength defined by the electrode finger pitch of the IDT is λ, the value obtained by dividing the product of the density and thickness of any layer by the density of Al and the wavelength λ is expressed as a percentage as the Al-converted normalized thickness of the layer, and the total Al-converted normalized thickness of the electrode finger layer is the Al-converted normalized thickness of the electrode finger, i.e., T. IDT [%], the Al-converted normalized thickness of the mass-added film is set to T m [%], convert the Al of the mass added film into a normalized thickness T m The Al-converted normalized thickness T of the electrode finger portion IDT The value obtained by dividing the thickness ratio by 3.15 is set as T R [%], T R = (1 / 3.15) × (T m / T IDT )×100[%], The duty ratio of the IDT is d, the dimension of the mass-added film along the extending direction of the electrode finger is divided by the wavelength λ, the value of x is equivalent to the value of the wavelength ratio width W, and the value of y is equivalent to the thickness ratio T R When the value of the wavelength ratio width W and the thickness ratio T in the xy plane is R is a value within the range of an ellipse and the inside of the ellipse represented by setting θ to be greater than or equal to 0° and less than 360° in the following equations 1 and 2, x=0.19×cos(-5.5°)×cosθ-0.021×sin(-5.5°)×sinθ+0.0146×T IDT 2 -0.229×T IDT +1.5611+0.4×(d-0.55) Formula 1 y=0.19×sin(-5.5°)×cosθ+0.021×cos(-5.5°)×sinθ+10.15 Equation 2.

2. An elastic wave device comprising: High sound velocity material layer; a piezoelectric layer, disposed on the high acoustic velocity material layer, comprising lithium tantalate; and The IDT is provided on the piezoelectric layer and has a plurality of electrode fingers, each of the plurality of electrode fingers includes at least one electrode finger layer. The acoustic velocity of the body wave propagating in the high-acoustic-velocity material layer is higher than the acoustic velocity of the elastic wave propagating in the piezoelectric layer. The direction in which the plurality of electrode fingers extend is defined as an electrode finger extension direction, and when the IDT is observed from a direction orthogonal to the electrode finger extension direction, a region where adjacent electrode fingers overlap each other is a crossing region, and the crossing region includes a central region and a pair of edge regions arranged to sandwich the central region in the electrode finger extension direction. The elastic wave device further includes a mass-added film, the mass-added film being provided in at least one of the edge regions and being continuously provided to overlap with the plurality of electrode fingers and a region between the electrode fingers in a plan view. The resonant frequency is higher than 1GHz. The wavelength defined by the electrode finger pitch of the IDT is λ, the value obtained by dividing the product of the density and thickness of any layer by the density of Al and the wavelength λ is expressed as a percentage as the Al-converted normalized thickness of the layer, and the total Al-converted normalized thickness of the electrode finger layer is the Al-converted normalized thickness of the electrode finger, i.e., T. IDT [%], the Al-converted normalized thickness of the mass-added film is set to T m [%], convert the Al of the mass added film into a normalized thickness T m The Al-converted normalized thickness T of the electrode finger portion IDT The value obtained by dividing the thickness ratio by 3.15 is set as T R [%], T R = (1 / 3.15) × (T m / T IDT )×100[%], When the duty ratio of the IDT is d and the value obtained by dividing the dimension of the mass addition film along the extending direction of the electrode finger by the wavelength λ is defined as the wavelength ratio width W, the wavelength ratio width W of the mass addition film is: 0.88×{0.0101×T IDT 2 -0.1677×T IDT +1.3201+0.4×(d-0.55)}≤W≤1.12×{0.0101×T IDT 2 -0.1677×T IDT +1.3201+0.4×(d-0.55)}, The thickness ratio T R =0.88×10.7≤T R ≤1.12×10.

7.

3. An elastic wave device comprising: High sound velocity material layer; a piezoelectric layer, disposed on the high acoustic velocity material layer, comprising lithium tantalate; and The IDT is provided on the piezoelectric layer and has a plurality of electrode fingers, each of the plurality of electrode fingers includes at least one electrode finger layer. The acoustic velocity of the body wave propagating in the high-acoustic-velocity material layer is higher than the acoustic velocity of the elastic wave propagating in the piezoelectric layer. The direction in which the plurality of electrode fingers extend is defined as an electrode finger extension direction, and when the IDT is observed from a direction orthogonal to the electrode finger extension direction, a region where adjacent electrode fingers overlap each other is a crossing region, and the crossing region includes a central region and a pair of edge regions arranged to sandwich the central region in the electrode finger extension direction. The elastic wave device further includes a mass-added film, the mass-added film being provided in at least one of the edge regions and being continuously provided to overlap with the plurality of electrode fingers and a region between the electrode fingers in a plan view. The resonant frequency is below 1 GHz. The wavelength defined by the electrode finger pitch of the IDT is λ, the value obtained by dividing the product of the density and thickness of any layer by the density of Al and the wavelength λ is expressed as a percentage as the Al-converted normalized thickness of the layer, and the total Al-converted normalized thickness of the electrode finger layer is the Al-converted normalized thickness of the electrode finger, i.e., T. IDT [%], the Al-converted normalized thickness of the mass-added film is set to T m [%], convert the Al of the mass added film into a normalized thickness T m The Al-converted normalized thickness T of the electrode finger portion IDT The value obtained by dividing the thickness ratio by 3.15 is set as T R [%], T R = (1 / 3.15) × (T m / T IDT )×100[%], The duty ratio of the IDT is d, the dimension of the mass-added film along the extending direction of the electrode finger is divided by the wavelength λ, the value of x is equivalent to the value of the wavelength ratio width W, and the value of y is equivalent to the thickness ratio T R When the value of the wavelength ratio width W and the thickness ratio T in the xy plane is R is a value within the range of an ellipse and the inside of the ellipse represented by setting t to be greater than or equal to 0° and less than 360° in the following equations 3 and 4, x=0.16×cost×cos(1.3°)-25.5×sint×sin(1.3°)+2.22-2.54×d+2.06×d 2 Formula 3 y=0.16×cost×sin(1.3°)+25.5×cost×sin(1.3°)+25.5-0.033×(T IDT -7.83) Equation 4.

4. An elastic wave device comprising: High sound velocity material layer; a piezoelectric layer, disposed on the high acoustic velocity material layer, comprising lithium niobate; and The IDT is provided on the piezoelectric layer and has a plurality of electrode fingers, each of the plurality of electrode fingers includes at least one electrode finger layer. The acoustic velocity of the body wave propagating in the high-acoustic-velocity material layer is higher than the acoustic velocity of the elastic wave propagating in the piezoelectric layer. The direction in which the plurality of electrode fingers extend is defined as an electrode finger extension direction, and when the IDT is observed from a direction orthogonal to the electrode finger extension direction, a region where adjacent electrode fingers overlap each other is a crossing region, and the crossing region includes a central region and a pair of edge regions arranged to sandwich the central region in the electrode finger extension direction. The elastic wave device further includes a mass-added film, the mass-added film being provided in at least one of the edge regions and being continuously provided to overlap with the plurality of electrode fingers and a region between the electrode fingers in a plan view. The wavelength defined by the electrode finger pitch of the IDT is λ, the value obtained by dividing the product of the density and thickness of any layer by the density of Al and the wavelength λ is expressed as a percentage as the Al-converted normalized thickness of the layer, and the total Al-converted normalized thickness of the electrode finger layer is the Al-converted normalized thickness of the electrode finger, i.e., T. IDT [%], the Al-converted normalized thickness of the mass-added film is set to T m [%], convert the Al of the mass added film into a normalized thickness T m The Al-converted normalized thickness T of the electrode finger portion IDT The value obtained by dividing the thickness ratio by 3.15 is set as T R [%], T R = (1 / 3.15) × (T m / T IDT )×100[%], The duty ratio of the IDT is d, the dimension of the mass-added film along the extending direction of the electrode finger is divided by the wavelength λ, the value of x is equivalent to the value of the wavelength ratio width W, and the value of y is equivalent to the thickness ratio T R When the value of the wavelength ratio width W and the thickness ratio T in the xy plane is R is a value within the range of an ellipse and the inside of the ellipse represented by setting t to be greater than 0° and less than 360° in the following equations 5 and 6, x=0.22×cost×cos(6°)-3.9×sint×sin(6°)+1.0+0.4×(d-0.5)+0.0022×(T IDT -6.9) Formula 5 y=0.22×cost×sin(6°)+3.9×cost×sin(6°)+7.9-0.033×(T IDT -6.9) Equation 6.

5. The elastic wave device according to any one of claims 1 to 4, wherein: The elastic wave device includes a plurality of mass-added films. The mass adding films are respectively provided in the edge regions on both sides.

6. The elastic wave device according to any one of claims 1 to 5, wherein: The IDT comprises an IDT electrode, The elastic wave device further includes a dielectric film provided on the piezoelectric layer so as to cover the IDT electrode. The at least one electrode finger layer of the electrode finger portion includes a metal layer included in the IDT electrode and a dielectric layer included in the dielectric film.

7. The elastic wave device according to claim 6, wherein: The mass-adding film is arranged between the metal layer and the dielectric layer in the edge region.

8. The elastic wave device according to claim 7, wherein: The mass-added film has a density higher than a density of the dielectric layer of the electrode finger portion.

9. The elastic wave device according to any one of claims 1 to 8, wherein: As a material of the mass additional film, tantalum oxide was used.

10. The elastic wave device according to any one of claims 1 to 9, wherein: The high-acoustic-velocity material layer is a high-acoustic-velocity supporting substrate.

11. The elastic wave device according to any one of claims 1 to 9, wherein: The elastic wave device further includes a supporting substrate. The high-acoustic-velocity material layer is a high-acoustic-velocity film provided between the support substrate and the piezoelectric layer.

12. The elastic wave device according to any one of claims 1 to 11, wherein: The elastic wave device further includes a low acoustic velocity film provided between the high acoustic velocity material layer and the piezoelectric layer. The acoustic velocity of the bulk wave propagating through the low-acoustic-velocity film is lower than the acoustic velocity of the bulk wave propagating through the piezoelectric layer.

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