Acoustic wave devices and communication devices

Abstract

In the present invention, the size of an elastic wave device is reduced. The elastic wave device includes: a support substrate; a piezoelectric body layer that directly, or indirectly, contacts the support substrate; and an IDT electrode that is positioned on the piezoelectric body layer. The elastic wave device excites asymmetrical zero-order-mode Lamb waves.

Description

[Technical Field]

[0001] The present disclosure relates to an acoustic wave device and a communication device. [Background technology]

[0002] Conventionally, acoustic wave elements having a structure in which an IDT (Interdigital Transducer) electrode is formed on a piezoelectric crystal have been known. The acoustic wave elements can be used, for example, as filters (SAW filters) that excite surface acoustic waves (SAW) near a specific frequency and receive electrical signals near a specific frequency, and are used as bandpass filters in communication devices (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2012-257019 Summary of the Invention

[0004] An elastic wave device according to one embodiment of the present disclosure includes a support substrate, a piezoelectric layer in direct or indirect contact with the support substrate, and an IDT electrode located on the piezoelectric layer, and excites an asymmetric zeroth-mode Lamb wave. [Brief explanation of the drawings]

[0005] [Figure 1] 1 is a perspective view illustrating a configuration example of an elastic wave device according to an embodiment of the present disclosure. [Figure 2] 1 is a cross-sectional view illustrating a configuration example of an elastic wave device according to an embodiment of the present disclosure. [Figure 3] FIG. 1 is a diagram illustrating an outline of an FEM simulation model of an elastic wave device. [Figure 4] 1 is a table showing FEM simulation conditions. [Figure 5A]1 is a table showing FEM simulation conditions related to the thickness of an Al electrode in Study Example 1. [Figure 5B] 10 is a graph showing the results of an FEM simulation of the relationship between the Al electrode thickness and the fractional bandwidth Δf in Study Example 1. [Figure 5C] 10 is a graph showing the results of an FEM simulation of the relationship between the thickness of the Al electrode and the sound velocity V in Study Example 1. [Figure 6A] 10 is a table showing FEM simulation conditions related to LT thickness in Study Example 1. [Figure 6B] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LT thickness and the fractional bandwidth Δf in Study Example 1. [Figure 6C] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LT thickness and the sound velocity V in Study Example 1. [Figure 7A] 10 is a table showing FEM simulation conditions related to the LT cut angle in Study Example 1. [Figure 7B] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LT cut angle and the fractional bandwidth Δf in Study Example 1. [Figure 7C] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LT cut angle and the sound velocity V in Study Example 1. [Figure 8A] 10 is a table showing FEM simulation conditions related to the LT propagation angle in Study Example 1. [Figure 8B] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LT propagation angle and the fractional bandwidth Δf in Study Example 1. [Figure 8C] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LT propagation angle and the sound speed V in Study Example 1. [Figure 9A] 10 is a table showing FEM simulation conditions related to the Cu electrode thickness in Study Example 2. [Figure 9B]10 is a graph showing the results of an FEM simulation of the relationship between the Cu electrode thickness and the fractional bandwidth Δf in Study Example 2. [Figure 9C] 10 is a graph showing the results of an FEM simulation regarding the relationship between the Cu electrode thickness and the sound velocity V in Study Example 2. [Figure 10A] 10 is a table showing FEM simulation conditions related to LT thickness in Study Example 2. [Figure 10B] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LT thickness and the fractional bandwidth Δf in Study Example 2. [Figure 10C] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LT thickness and the sound velocity V in Study Example 2. [Figure 11A] 10 is a table showing FEM simulation conditions related to the LT cut angle in Study Example 2. [Figure 11B] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LT cut angle and the fractional bandwidth Δf in Study Example 2. [Figure 11C] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LT cut angle and the sound velocity V in Study Example 2. [Figure 12A] 10 is a table showing FEM simulation conditions related to the LT propagation angle in Study Example 2. [Figure 12B] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LT propagation angle and the fractional bandwidth Δf in Study Example 2. [Figure 12C] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LT propagation angle and the sound speed V in Study Example 2. [Figure 13A] 10 is a table showing FEM simulation conditions related to the thickness of a Pt electrode in Study Example 3. [Figure 13B] 10 is a graph showing the results of an FEM simulation of the relationship between the Pt electrode thickness and the fractional bandwidth Δf in Study Example 3. [Figure 13C]10 is a graph showing the results of an FEM simulation of the relationship between the Pt electrode thickness and the sound velocity V in Study Example 3. [Figure 14A] 10 is a table showing FEM simulation conditions related to LT thickness in Study Example 3. [Figure 14B] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LT thickness and the fractional bandwidth Δf in Study Example 3. [Figure 14C] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LT thickness and the sound velocity V in Study Example 3. [Figure 15A] 10 is a table showing FEM simulation conditions related to the LT cut angle in Study Example 3. [Figure 15B] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LT cut angle and the fractional bandwidth Δf in Study Example 3. [Figure 15C] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LT cut angle and the sound velocity V in Study Example 3. [Figure 16A] 10 is a table showing FEM simulation conditions related to the LT propagation angle in Study Example 3. [Figure 16B] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LT propagation angle and the fractional bandwidth Δf in Study Example 3. [Figure 16C] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LT propagation angle and the sound speed V in Study Example 3. [Figure 17A] 1 is a table showing the shear wave acoustic velocities of major metallic materials. [Figure 17B] FIG. 10 is a diagram showing a calculation formula for shear wave sound velocity. [Figure 18A] 1 is a graph showing the relationship between the shear wave acoustic velocity of the electrode material and the center point CP of the electrode thickness in the results of Study Examples 1 to 3. [Figure 18B] 1 is a graph showing the relationship between the shear wave acoustic velocity and the acoustic velocity (elastic wave acoustic velocity) V of the electrode material in the results of Study Examples 1 to 3. [Figure 18C]1 is a graph showing the relationship between shear wave acoustic velocity and fractional bandwidth Δf of electrode materials in the results of Study Examples 1 to 3. [Figure 19A] 10 is a table showing FEM simulation conditions related to the thickness of the Al electrode in Study Example 5. [Figure 19B] 10 is a graph showing the results of an FEM simulation regarding the relationship between the Al electrode thickness and the fractional bandwidth Δf in Study Example 5. [Figure 19C] 10 is a graph showing the results of an FEM simulation regarding the relationship between the thickness of the Al electrode and the sound velocity V in Study Example 5. [Figure 20A] 10 is a table showing FEM simulation conditions related to LN thickness in Study Example 5. [Figure 20B] 10 is a graph showing the results of an FEM simulation of the relationship between the LN thickness and the fractional bandwidth Δf in Study Example 5. [Figure 20C] 10 is a graph showing the results of an FEM simulation of the relationship between the LN thickness and the sound velocity V in Study Example 5. [Figure 21A] 10 is a table showing FEM simulation conditions related to the LN cut angle in Study Example 5. [Figure 21B] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LN cut angle and the fractional bandwidth Δf in Study Example 5. [Figure 21C] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LN cut angle and the sound velocity V in Study Example 5. [Figure 22A] 10 is a table showing FEM simulation conditions related to the LN propagation angle in Study Example 5. [Figure 22B] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LN propagation angle and the fractional bandwidth Δf in Study Example 5. [Figure 22C] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LN propagation angle and the sound speed V in Study Example 5. [Figure 23A]10 is a table showing FEM simulation conditions related to the Cu electrode thickness in Study Example 6. [Figure 23B] 10 is a graph showing the results of an FEM simulation of the relationship between the Cu electrode thickness and the fractional bandwidth Δf in Study Example 6. [Figure 23C] 10 is a graph showing the results of an FEM simulation of the relationship between the Cu electrode thickness and the sound velocity V in Study Example 6. [Figure 24A] 10 is a table showing FEM simulation conditions related to LN thickness in Study Example 6. [Figure 24B] 10 is a graph showing the results of an FEM simulation of the relationship between the LN thickness and the fractional bandwidth Δf in Study Example 6. [Figure 24C] 10 is a graph showing the results of an FEM simulation of the relationship between the LN thickness and the sound velocity V in Study Example 6. [Figure 25A] 10 is a table showing FEM simulation conditions related to the LN cut angle in Study Example 6. [Figure 25B] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LN cut angle and the fractional bandwidth Δf in Study Example 6. [Figure 25C] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LN cut angle and the sound velocity V in Study Example 6. [Figure 26A] 10 is a table showing FEM simulation conditions for the LN propagation angle in Study Example 6. [Figure 26B] 13 is a graph showing the results of an FEM simulation regarding the relationship between the LN propagation angle and the fractional bandwidth Δf in Study Example 6. [Figure 26C] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LN propagation angle and the sound speed V in Study Example 6. [Figure 27A] 10 is a table showing FEM simulation conditions related to the thickness of a Pt electrode in Study Example 7. [Figure 27B]13 is a graph showing the results of an FEM simulation of the relationship between the Pt electrode thickness and the fractional bandwidth Δf in Study Example 7. [Figure 27C] 13 is a graph showing the results of an FEM simulation of the relationship between the Pt electrode thickness and the sound velocity V in Study Example 7. [Figure 28A] 10 is a table showing FEM simulation conditions related to LN thickness in Study Example 7. [Figure 28B] 13 is a graph showing the results of an FEM simulation of the relationship between the LN thickness and the fractional bandwidth Δf in Study Example 7. [Figure 28C] 10 is a graph showing the results of an FEM simulation of the relationship between the LN thickness and the sound velocity V in Study Example 7. [Figure 29A] 10 is a table showing FEM simulation conditions related to the LN cut angle in Study Example 7. [Figure 29B] 13 is a graph showing the results of an FEM simulation regarding the relationship between the LN cut angle and the fractional bandwidth Δf in Study Example 7. [Figure 29C] 10 is a graph showing the results of an FEM simulation regarding the relationship between the LN cut angle and the sound velocity V in Study Example 7. [Figure 30A] 10 is a table showing FEM simulation conditions related to the LN propagation angle in Study Example 7. [Figure 30B] 13 is a graph showing the results of an FEM simulation regarding the relationship between the LN propagation angle and the fractional bandwidth Δf in Study Example 7. [Figure 30C] 13 is a graph showing the results of an FEM simulation regarding the relationship between the LN propagation angle and the sound speed V in Study Example 7. [Figure 31A] 10 is a graph showing the relationship between the shear wave acoustic velocity of the electrode material and the center point CP of the electrode thickness in the results of Study Examples 5 to 7. [Figure 31B] 10 is a graph showing the relationship between the shear wave acoustic velocity and the acoustic velocity (elastic wave acoustic velocity) V of the electrode material in the results of Study Examples 5 to 7. [Figure 31C]10 is a graph showing the relationship between the shear wave acoustic velocity and the fractional bandwidth Δf of the electrode material in the results of Study Examples 5 to 7. [Figure 32] FIG. 10 is a perspective view illustrating another exemplary structure of an elastic wave device according to an embodiment of the present disclosure. [Figure 33] FIG. 10 is a cross-sectional view illustrating another exemplary configuration of an elastic wave device according to an embodiment of the present disclosure. [Figure 34] FIG. 10 is a cross-sectional view illustrating another exemplary configuration of an elastic wave device according to an embodiment of the present disclosure. [Figure 35] FIG. 1 is a diagram illustrating a schematic configuration of a communication device. DETAILED DESCRIPTION OF THE INVENTION

[0006] An elastic wave device according to an embodiment of the present disclosure will be described in detail below with reference to the drawings. However, the following description is intended to facilitate a better understanding of the spirit of the invention and is not intended to limit the present disclosure unless otherwise specified. Unless otherwise specified, the term "A to B" used to represent a numerical range means "A or greater and B or less." Furthermore, for the sake of convenience, the figures referenced in the following description show simplified views of only the main components necessary to describe the embodiments, and descriptions of well-known technical matters are omitted as appropriate for brevity. Therefore, the elastic wave device according to the present embodiment may optionally include well-known components not shown in the figures. Furthermore, the dimensions of the components in the figures do not faithfully represent the actual dimensions of the components or the dimensional ratios of the components.

[0007] <Outline of the configuration of the elastic wave device> FIG. 1 is a perspective view illustrating an example configuration of elastic wave device 100 according to this preferred embodiment. FIG. 2 is a cross-sectional view illustrating an example configuration of elastic wave device 100 according to this preferred embodiment. The specific shape of IDT electrode 3 included in elastic wave device 100 according to this preferred embodiment is not particularly limited, and electrode fingers 32 of IDT electrode 3 may be formed in various known shapes. Therefore, in FIG. 1, electrode fingers 32 of IDT electrode 3 are simply illustrated with diagonal hatching. Furthermore, in FIG. 2 and the cross-sectional views referred to in the following description, for clarity of illustration, components behind the cross section are omitted (cross-sectional views of a cut portion).

[0008] 1 and 2 , an elastic wave device 100 according to an embodiment of the present disclosure may include at least one resonator 1. In one example of elastic wave device 100, an input terminal Tin and an output terminal Tout may be connected to resonator 1. Resonator 1 may be configured as a frequency filter (SAW filter) that filters an electrical signal input to input terminal Tin and outputs the filtered electrical signal to output terminal Tout.

[0009] The acoustic wave device 100 may include a support substrate 5, a piezoelectric layer 2 that is in direct or indirect contact with the support substrate 5, and an IDT electrode 3 that is located on the piezoelectric layer 2. The IDT electrode 3 is also referred to as an excitation electrode. The acoustic wave device 100 of this preferred embodiment is configured to effectively excite an asymmetric zeroth-order mode Lamb wave. This will be described in more detail below.

[0010] When the acoustic wave device 100 includes multiple resonators 1, each of the multiple resonators 1 may share the support substrate 5 and the piezoelectric layer 2. Each of the multiple resonators 1 may have an individual IDT electrode 3.

[0011] Support substrate 5 supports each component of acoustic wave device 100. The material of support substrate 5 is not particularly limited, and may be, for example, a Si substrate.

[0012] The piezoelectric layer 2 may be made of a single crystal material having piezoelectric properties. For example, the material of the piezoelectric layer 2 may be lithium tantalate (also called LiTaO3:LT) or lithium niobate (also called LiNbO3:LN).

[0013] The acoustic wave device 100 may have an intermediate layer 6 located between the support substrate 5 and the piezoelectric layer 2. The support substrate 5 and the piezoelectric layer 2 may be bonded to each other via the intermediate layer 6. The intermediate layer 6 is typically made of silicon oxide (SiO x ) As an example, intermediate layer 6 may be a SiO2 film. Acoustic wave device 100 does not necessarily have to include intermediate layer 6. Acoustic wave device 100 with intermediate layer 6 may be easier to manufacture than acoustic wave device 100 without intermediate layer 6. Furthermore, if acoustic wave device 100 does not include intermediate layer 6, a bonding layer formed between support substrate 5 and piezoelectric layer 2 by bonding them during the manufacturing process of acoustic wave device 100 may adversely affect the filter characteristics of acoustic wave device 100. This is because the bonding layer is relatively close to the surface of piezoelectric layer 2 that is farther from support substrate 5.

[0014] The IDT electrode 3 is typically an interdigital electrode in which electrode pairs, each consisting of a first electrode finger 32a of positive polarity and a second electrode finger 32b of negative polarity, are periodically arranged. On the surface of the piezoelectric layer 2, the propagation direction of the SAW excited by the IDT electrode 3 is perpendicular to the extension directions of the first electrode fingers 32a and the second electrode fingers 32b.

[0015] 1, the propagation direction of the SAW propagating on the surface of piezoelectric layer 2 in acoustic wave device 100 is designated as the x-direction, the thickness direction of each component of acoustic wave device 100 is designated as the z-direction, and the direction perpendicular to the x-direction and z-direction is designated as the y-direction. Hereinafter, the positive z-direction may be referred to as the upward direction, and the negative z-direction may be referred to as the downward direction. The Cartesian coordinate system (xyz coordinate system) shown in FIG. 1 is also shown in the drawings referred to in the following description, as appropriate.

[0016] The IDT electrode 3 may have two bus bars 31 (a first bus bar 31a and a second bus bar 31b) facing each other in the y direction. The IDT electrode 3 may have a plurality of first electrode fingers 32a connected to the first bus bar 31a and a plurality of second electrode fingers 32b connected to the second bus bar 31b. The first electrode fingers 32a may extend in the y direction from the first bus bar 31a toward the second bus bar 31b. The second electrode fingers 32b may extend in the y direction from the second bus bar 31b toward the first bus bar 31a.

[0017] 2, the first electrode fingers 32a and the second electrode fingers 32b may be alternately and repeatedly positioned on the piezoelectric layer 2 at approximately constant intervals in the x direction. In this specification, the first electrode fingers 32a and the second electrode fingers 32b may be collectively referred to as electrode fingers 32. The electrode finger pitch (electrode finger pitch) p in the IDT electrode 3 may be the distance between the centers of two adjacent electrode fingers 32 in the x direction (in other words, the repetition interval of the electrode fingers 32). In general, the wavelength λ of the SAW excited by the IDT electrode 3 may be defined as twice the electrode finger pitch p. Hereinafter, λ is defined as 2p.

[0018] In this specification, the length in the x-direction of one of the electrode fingers 32 (first electrode finger 32a or second electrode finger 32b) is referred to as width w. The first electrode finger 32a and the second electrode finger 32b may have the same or approximately the same width w. In this specification, "approximately the same" means that they are substantially the same, and a dimensional difference (error) of about ±5% is allowed. This also applies to the following description, so repeated explanation will be omitted.

[0019] The width w may be set appropriately depending on, for example, the electrical characteristics required of the acoustic wave device 100. As an example, the width w may be set corresponding to the electrode finger pitch p. In this specification, the ratio of the width w to the electrode finger pitch p (w / p) is referred to as the duty. In the resonator 1, the width w and electrode finger pitch p may be constant across all of the electrode fingers 32 (i.e., the duty may be constant). In this specification, the term "constant" does not necessarily mean that there is no strict change, but rather means that an error of about ±5 degrees is allowed.

[0020] The electrode fingers 32 may be formed of, for example, a thin, flat plate extending in the y direction and made of a metal material. As an example, the metal may be aluminum (Al), copper (Cu), or platinum (Pt). The configuration (material and thickness) of the electrode fingers 32 will be described in more detail later.

[0021] The IDT electrode 3 may further include a protective layer that covers the electrode fingers 32. The material of the protective layer may be, for example, SiO2, or any insulating material that is generally used as a protective film may be used as appropriate.

[0022] Acoustic wave device 100 may include a pair of reflectors 4a and 4b corresponding to IDT electrode 3. In this specification, reflectors 4a and 4b are also collectively referred to as reflectors 4. Reflectors 4 may be positioned on either side of IDT electrode 3 in the x-direction.

[0023] <Summary of the findings of this disclosure> In communication devices and the like, a relatively low frequency band, for example, a frequency band of 700 MHz to 900 MHz (hereinafter, for convenience of explanation, sometimes referred to as the "target frequency band") is used for communication. A value calculated by dividing the bandwidth (passband width) by the center frequency (resonant frequency) is called the fractional bandwidth (sometimes referred to as the "fractional bandwidth Δf" in this specification). Of the fractional bandwidths Δf of various current communication bands that use the target frequency band, the smallest value is 1.1% for downstream communication of Band 6. Therefore, the inventors have set the following conditions for the filter characteristics of elastic wave device 100: a bandwidth in the target frequency band and a fractional bandwidth Δf of 1.1% or greater.

[0024] Furthermore, further miniaturization is required for acoustic wave devices 100 that are installed in communication devices and the like that use the above-mentioned target frequency bands. Generally, Lamb waves, which have a vibration plane perpendicular to the surface of piezoelectric layer 2, are one of the various propagation modes of SAWs and are known to have multimode properties. Among Lamb waves, the asymmetric zeroth-order mode Lamb wave (also referred to as the "A0 mode Lamb wave") has a lower acoustic velocity than various general SAWs. In this specification, "acoustic velocity" refers to the propagation velocity of the acoustic wave used in acoustic wave device 100, and can also be considered as the phase velocity.

[0025] The inventors came up with the idea of ​​miniaturizing acoustic wave device 100 by using A0 mode Lamb waves to reduce the acoustic velocity V. The acoustic velocity V of A0 mode Lamb waves decreases as the thickness of piezoelectric layer 2 decreases. However, no acoustic wave device 100 using A0 mode Lamb waves that satisfies the condition of a fractional bandwidth Δf of 1.1% or greater in a target frequency band is known, and the specific conditions required for acoustic wave device 100 are unclear.

[0026] The inventors evaluated the relationship between the specific structure and filter characteristics of the elastic wave device 100 having the above-described basic structure (bonded structure) using finite element method (FEM) simulation. Then, they found the conditions defined for the structure of the elastic wave device 100 and arrived at the present invention. Hereinafter, the results explored by the inventors using FEM simulation, that is, the structure of the resonator 1 in the elastic wave device 100 where the characteristics of the specific bandwidth Δf and the sound velocity V satisfy predetermined conditions will be described.

[0027] <Basic Structure of FEM Simulation> FIG. 3 is a diagram showing an outline of an FEM simulation model of an elastic wave device. FIG. 4 is a table showing FEM simulation conditions. As shown in FIG. 3, in the FEM simulation model SM of the elastic wave device, the piezoelectric layer 2 is bonded via the intermediate layer 6 above the support substrate 5, and has the first electrode finger 32a and the second electrode finger 32b located on the surface of the piezoelectric layer 2.

[0028] FEM simulation was performed under the conditions as shown in FIG. 4. The material of the electrode finger 32 was Al, Cu, or Pt. The material of the piezoelectric layer 2 was LT (LiTaO3) or LN (LiNbO3). The thickness of the electrode finger 32, as well as the thickness, cut angle, and propagation angle of the piezoelectric layer 2 were used as variables. Also, in the FEM simulation, the electrode finger pitch p was fixed at 1.0 μm and the duty was fixed at 0.5. The wavelength λ of the asymmetric 0th mode drum wave was 2.0 μm, which is twice the electrode finger pitch p.

[0029] Here, in the preliminary FEM simulation, the thickness of the intermediate layer 6 did not significantly affect the filter characteristics. Therefore, in the FEM simulation described below, the material of the intermediate layer 6 was SiO2 and the thickness was fixed at 0.5λ as a general value.

[0030] The Euler angles of the piezoelectric layer 2 can generally be expressed as (φ, θ, ψ). In the FEM simulation described below, φ is fixed at 0°, and θ and ψ are variables. The meanings of φ, θ, and ψ in the Euler angles of the piezoelectric layer 2 can be understood based on common technical knowledge. For the sake of brevity, a detailed description of the Euler angles of the piezoelectric layer 2 will be omitted.

[0031] In each of the multiple FEM simulation results described below, the condition range required for each variable and the center point CP within that range were specified. In this specification, the "center point CP" is not the median value of the range, but a value selected in consideration of the balance of both the fractional bandwidth Δf and the sound speed V characteristics, and the reason for its selection will be described later in each individual FEM simulation result.

[0032] <Study example 1: LT film and Al electrode> In Study Example 1, an FEM simulation was performed using Al as the electrode material and an LT film as the piezoelectric layer 2.

[0033] (Al electrode thickness) FIG. 5A is a table showing FEM simulation conditions related to the Al electrode thickness in Study Example 1. FIG. 5B is a graph showing the results of an FEM simulation of the relationship between the Al electrode thickness and the fractional bandwidth Δf in Study Example 1. FIG. 5C is a graph showing the results of an FEM simulation of the relationship between the Al electrode thickness and the sound velocity V in Study Example 1. In the FEM simulation of the Al electrode thickness in Study Example 1, the Euler angles of the piezoelectric layer 2 were fixed to typical values ​​(0°, 36°, 0°). The LT thickness was also fixed to 50%λ.

[0034] As shown in Figures 5A to 5C, when the Al electrode thickness is in the range of 0.6%λ or more and 50.0%λ or less, the relative bandwidth Δf is 1.1%fr or more. Regarding the relationship between the sound velocity V and the Al electrode thickness, it can be seen that the sound velocity V generally tends to decrease as the Al electrode thickness increases. The maximum point in the fitting curve of the plot of the relative bandwidth Δf shown in Figure 5B was selected as the center point CP. In other words, the center point CP of the Al electrode thickness in Study Example 1 was set to 30%λ.

[0035] In this specification, the unit of the fractional bandwidth Δf may be expressed as "%fr," which means that the value calculated by dividing the passband width by the resonant frequency (fr) is expressed as a percentage.

[0036] (LT thickness) Fig. 6A is a table showing FEM simulation conditions related to LT thickness in Study Example 1. Fig. 6B is a graph showing the results of an FEM simulation of the relationship between LT thickness and fractional bandwidth Δf in Study Example 1. Fig. 6C is a graph showing the results of an FEM simulation of the relationship between LT thickness and sound velocity V in Study Example 1. In the FEM simulation of LT thickness in Study Example 1, the Euler angles of the piezoelectric layer 2 were fixed to typical values ​​(0°, 36°, 0°), and the Al electrode thickness was fixed to 30%λ, which is the center point CP in the above-mentioned FEM simulation results.

[0037] As shown in Figures 6A to 6C, it can be seen that the relative bandwidth Δf is 1.1%fr or more when the LT thickness is in the range of 20.0%λ or more. Furthermore, in the range of LT thickness of 20.0%λ or more, the sound velocity V increases as the LT thickness increases, and the value of the sound velocity V is saturated at an LT thickness of 87.5%λ. Based on this result, it can be seen that the relative bandwidth Δf is relatively large and the sound velocity V The point where the LT thickness was relatively slow was selected as the center point CP. That is, the center point CP of the LT thickness in Study Example 1 was set to 32.5%λ.

[0038] (LT cut angle) Fig. 7A is a table showing FEM simulation conditions related to the LT cut angle in Study Example 1. Fig. 7B is a graph showing the results of an FEM simulation of the relationship between the LT cut angle and the fractional bandwidth Δf in Study Example 1. Fig. 7C is a graph showing the results of an FEM simulation of the relationship between the LT cut angle and the sound velocity V in Study Example 1. In the FEM simulation of the LT cut angle in Study Example 1, the Al electrode thickness was fixed to 30% λ, which is the center point CP in the above-mentioned FEM simulation results, and the LT thickness was fixed to 32.5% λ, which is the center point CP in the above-mentioned FEM simulation results.

[0039] As shown in Figures 7A to 7C, when the LT cut angle is in the range of 8° to 74°, the fractional bandwidth Δf is 1.1% fr or more. To be consistent with the search in other FEM simulations, the center point CP of the LT cut angle was set to 36°. As shown in Figure 7B, the center point CP of the LT cut angle is located near the maximum point in the fitting curve of the plot of the fractional bandwidth Δf.

[0040] (LT propagation angle) FIG. 8A is a table showing FEM simulation conditions for the LT propagation angle in Study Example 1. FIG. 8B is a graph showing the results of an FEM simulation of the relationship between the LT propagation angle and the fractional bandwidth Δf in Study Example 1. FIG. 8C is a graph showing the results of an FEM simulation of the relationship between the LT propagation angle and the sound speed V in Study Example 1. In the FEM simulation of the LT propagation angle in Study Example 1, the Al electrode thickness was fixed to 30%λ, which is the center point CP in the above-mentioned FEM simulation results. In addition, the LT thickness was fixed to 32.5%λ, which is the center point CP in the above-mentioned FEM simulation results, and the LT cut angle was fixed to 36°.

[0041] As shown in Figures 8A to 8C, it can be seen that the fractional bandwidth Δf is 1.1% fr or more when the LT propagation angle is in the range of 0° to 26° and 154° to 180°, in other words, when the LT propagation angle is in the range of -26° to 26°. The fitting curve of the plot of fractional bandwidth Δf shown in Figure 8B actually has an upwardly convex peak because the LT propagation angles of 0° and 180° are equivalent. The maximum point of the fitting curve was selected as the center point CP. In other words, the center point CP of the LT propagation angle was set to 0°.

[0042] <Configuration example 1> In acoustic wave device 100 according to Configuration Example 1 of this embodiment, which is based on the FEM simulation results of Study Example 1 described above, the piezoelectric layer 2 is primarily made of lithium tantalate (LT) and has a thickness of 20.0%λ or more and 87.5%λ or less. Furthermore, the Euler angles of piezoelectric layer 2 are (φ, θ, ψ), where φ is between -5° and 5°, θ is between 8° and 74°, and ψ is between -26° and 26°. The IDT electrode 3 is primarily made of Al and has a thickness of 0.6%λ or more and 50.0%λ or less. λ is the wavelength λ of the A0-mode Lamb wave and is defined as twice the pitch p of the electrode fingers 32 included in the IDT electrode 3. The definition of λ is the same throughout the remainder of this specification, and will not be repeated.

[0043] To allow for errors in the manufacturing process, the Euler angles φ of piezoelectric layer 2 are set to a range of −5° to 5°. When φ is in the range of −5° to 5°, the characteristics of acoustic wave device 100 hardly change.

[0044] In elastic wave device 100 according to configuration example 1, A0 mode Lamb waves can be effectively excited or received by resonator 1. Elastic wave device 100 according to configuration example 1 functions as a SAW filter that utilizes the A0 mode Lamb waves, and has frequency characteristics in which the fractional bandwidth Δf is 1.1% fr or greater.

[0045] Here, the acoustic velocity V of a conventional SAW is approximately 4000 m / s, and the acoustic velocity V of an A0-mode Lamb wave is slower than that of a conventional SAW. For example, when acoustic wave device 100 having a certain resonant frequency is compared with an acoustic wave device (a conventional acoustic wave device) having the same resonant frequency using a conventional SAW, the following can be said. That is, because the acoustic velocity V of the A0-mode Lamb wave is smaller than that of a conventional SAW, acoustic wave device 100 can have a smaller electrode finger pitch p than the conventional acoustic wave device, based on V = fλ (f: constant) and λ = 2p. For example, if the resonant frequency fr is 1000 MHz, when V = 4000 m / s, the electrode finger pitch p is 2 μm, and when V = 2000 m / s, the electrode finger pitch p is 1 μm. For a given total number of electrode fingers 32, the smaller the electrode finger pitch p, the more compact the IDT electrode 3 can be.

[0046] According to elastic wave device 100 of Configuration Example 1, by utilizing A0 mode Lamb waves that propagate at a sound velocity V slower than that of conventional SAWs, it is possible to reduce the size of resonator 1. As a result, elastic wave device 100 can be effectively reduced in size while maintaining frequency characteristics with a fractional bandwidth Δf of 1.1% fr or greater.

[0047] (Additional notes) In this embodiment, "the main component of the constituent materials is component A" means that the proportion of component A in the entire constituent materials is greater than 50 mass %. This also applies to the following explanations in this specification, and will not be repeated.

[0048] In elastic wave device 100 according to Configuration Example 1 of this embodiment, piezoelectric layer 2 may be made of LT or may consist essentially of LT. Furthermore, IDT electrode 3 may be made of Al or may consist essentially of Al. In this embodiment, "consisting essentially of component B" means that the proportion of component B relative to the total mass of the constituent materials is 90 mass % or more. This also applies to the following description in this specification, and will not be repeated.

[0049] Without being limited to the above example, in elastic wave device 100 according to Configuration Example 1 of this preferred embodiment, piezoelectric layer 2 may contain 70 mass % or more, or 80 mass % or more, of LT. The remainder of the constituent material of piezoelectric layer 2 other than LT may be composed of any additive components and unavoidable impurities.

[0050] In acoustic wave device 100 according to Configuration Example 1 of this preferred embodiment, IDT electrode 3 may contain 70 mass % or more, or 80 mass % or more, of Al. The remainder of the constituent material of IDT electrode 3 other than Al may be composed of optional additive components and unavoidable impurities.

[0051] <Study example 2: LT film and Cu electrode> In Study Example 2, an FEM simulation was performed using Cu as the electrode material and an LT film as the piezoelectric layer 2.

[0052] (Cu electrode thickness) 9A is a table showing FEM simulation conditions for the Cu electrode thickness in Study Example 2. FIG. 9B is a graph showing the results of an FEM simulation of the relationship between the Cu electrode thickness and the fractional bandwidth Δf in Study Example 2. FIG. 9C is a graph showing the results of an FEM simulation of the relationship between the Cu electrode thickness and the sound velocity V in Study Example 2. In the FEM simulation of the Cu electrode thickness in Study Example 2, the Euler angles of the piezoelectric layer 2 were fixed to typical values ​​of (0°, 36°, 0°).

[0053] As shown in Figures 9A to 9C, when the Cu electrode thickness is in the range of 0.2%λ or more and 50.0%λ or less, the relative bandwidth Δf is 1.1%fr or more. Regarding the relationship between the sound velocity V and the Cu electrode thickness, it can be seen that the greater the Cu electrode thickness, the smaller the sound velocity V tends to be. The maximum point in the fitting curve of the plot of the relative bandwidth Δf shown in Figure 9B was selected as the center point CP. In other words, the center point CP of the Cu electrode thickness in Study Example 2 was set to 20%λ.

[0054] (LT thickness) Fig. 10A is a table showing FEM simulation conditions related to LT thickness in Study Example 2. Fig. 10B is a graph showing the results of an FEM simulation of the relationship between LT thickness and fractional bandwidth Δf in Study Example 2. Fig. 10C is a graph showing the results of an FEM simulation of the relationship between LT thickness and sound velocity V in Study Example 2. In the FEM simulation of LT thickness in Study Example 2, the Euler angles of the piezoelectric layer 2 were fixed to typical values ​​(0°, 36°, 0°), and the Cu electrode thickness was fixed to 20%λ, which is the center point CP in the above-mentioned FEM simulation results.

[0055] As shown in Figures 10A to 10C, it can be seen that the relative bandwidth Δf is 1.1%fr or more when the LT thickness is in the range of 17.5%λ or more. Furthermore, in the range of 17.5%λ or more, the sound velocity V increases as the LT thickness increases, and the value of the sound velocity V is saturated when the LT thickness is 90.0%λ. Based on this result, it can be seen that the relative bandwidth Δf is relatively large and the sound velocity V The point where the LT thickness was relatively slow was selected as the center point CP. That is, the center point CP of the LT thickness in Study Example 2 was set to 37.5%λ.

[0056] (LT cut angle) Fig. 11A is a table showing FEM simulation conditions related to the LT cut angle in Study Example 2. Fig. 11B is a graph showing the results of an FEM simulation regarding the relationship between the LT cut angle and the fractional bandwidth Δf in Study Example 2. Fig. 11C is a graph showing the results of an FEM simulation regarding the relationship between the LT cut angle and the sound velocity V in Study Example 2. In the FEM simulation regarding the LT cut angle in Study Example 2, the Cu electrode thickness was fixed to 20% λ, which is the center point CP in the above-mentioned FEM simulation results, and the LT thickness was fixed to 37.5% λ, which is the center point CP in the above-mentioned FEM simulation results.

[0057] 11A to 11C, the fractional bandwidth Δf is 1.1% fr or more when the LT cut angle is in the range of 0° to 80° and 160° to 180°, in other words, when the LT cut angle is in the range of -20° to 80°. For consistency with other FEM simulations, the center point CP of the LT cut angle was set to 36°. As shown in FIG. 11B, the center point CP of the LT cut angle is located near the maximum point in the fitting curve of the plot of the fractional bandwidth Δf.

[0058] (LT propagation angle) FIG. 12A is a table showing FEM simulation conditions for the LT propagation angle in Study Example 2. FIG. 12B is a graph showing the results of an FEM simulation of the relationship between the LT propagation angle and the fractional bandwidth Δf in Study Example 2. FIG. 12C is a graph showing the results of an FEM simulation of the relationship between the LT propagation angle and the sound speed V in Study Example 2. In the FEM simulation of the LT propagation angle in Study Example 2, the Cu electrode thickness was fixed to 20%λ, which is the center point CP in the above-mentioned FEM simulation results. In addition, the LT thickness was fixed to 37.5%λ, which is the center point CP in the above-mentioned FEM simulation results, and the LT cut angle was fixed to 36°.

[0059] As shown in Figures 12A to 12C, the fractional bandwidth Δf is 1.1% fr or more when the LT propagation angle is in the range of 0° to 40° and 140° to 180°, in other words, when the LT propagation angle is in the range of -40° to 40°. The fitting curve of the plot of fractional bandwidth Δf shown in Figure 12B has an upwardly convex peak because the LT propagation angles of 0° and 180° are equivalent. The maximum point of the fitting curve was selected as the center point CP. In other words, the center point CP of the LT propagation angle was set to 0°.

[0060] <Configuration example 2> In elastic wave device 100 according to Configuration Example 2 of this embodiment, which is based on the FEM simulation results of Study Example 2 described above, the piezoelectric layer 2 is primarily made of lithium tantalate (LT) and has a thickness of 17.5%λ or more and 90.0%λ or less. Furthermore, the Euler angles of piezoelectric layer 2 are (φ, θ, ψ), where φ is between -5° and 5°, θ is between -20° and 80°, and ψ is between -40° and 40°. The IDT electrode 3 is primarily made of Cu and has a thickness of 0.2%λ or more and 58.0%λ or less. The Euler angles of piezoelectric layer 2, φ, are specified to be between -5° and 5° to allow for tolerances for manufacturing errors.

[0061] In elastic wave device 100 according to Configuration Example 2 of this preferred embodiment, piezoelectric layer 2 may be the same as that in Configuration Example 1. IDT electrode 3 may be made of Cu, or may consist essentially of Cu. IDT electrode 3 may contain 70% by mass or more of Cu, or may contain 80% by mass or more of Cu. The remainder of the constituent material of IDT electrode 3 other than Cu may consist of optional additive components and unavoidable impurities.

[0062] In elastic wave device 100 of Configuration Example 2, A0 mode Lamb waves can also be effectively excited or received by resonator 1. By utilizing A0 mode Lamb waves, which propagate at a sound velocity V slower than that of conventional SAWs, resonator 1 can be made smaller. As a result, elastic wave device 100 can be effectively made smaller while maintaining frequency characteristics with a fractional bandwidth Δf of 1.1% fr or greater. This also applies to Configuration Examples 3 to 8 below, although a repeated explanation will be omitted.

[0063] <Study example 3: LT film and Pt electrode> In Study Example 3, an FEM simulation was performed using Pt as the electrode material and an LT film as the piezoelectric layer 2.

[0064] (Pt electrode thickness) Fig. 13A is a table showing FEM simulation conditions related to the Pt electrode thickness in Study Example 3. Fig. 13B is a graph showing the results of an FEM simulation of the relationship between the Pt electrode thickness and the fractional bandwidth Δf in Study Example 3. Fig. 13C is a graph showing the results of an FEM simulation of the relationship between the Pt electrode thickness and the sound velocity V in Study Example 3. In the FEM simulation of the Pt electrode thickness in Study Example 3, the Euler angles of the piezoelectric layer 2 were fixed to typical values ​​of (0°, 36°, 0°).

[0065] As shown in Figures 13A to 13C, when the Pt electrode thickness is in the range of 0.3%λ or more and 74.0%λ or less, the relative bandwidth Δf is 1.1%fr or more. Regarding the relationship between the sound velocity V and the Pt electrode thickness, it can be seen that the sound velocity V generally tends to decrease as the Pt electrode thickness increases. The maximum point in the fitting curve of the plot of the relative bandwidth Δf shown in Figure 13B was selected as the center point CP. In other words, the center point CP of the Pt electrode thickness in Study Example 3 was set to 13%λ.

[0066] (LT thickness) Fig. 14A is a table showing FEM simulation conditions related to LT thickness in Study Example 3. Fig. 14B is a graph showing the results of an FEM simulation of the relationship between LT thickness and fractional bandwidth Δf in Study Example 3. Fig. 14C is a graph showing the results of an FEM simulation of the relationship between LT thickness and sound velocity V in Study Example 3. In the FEM simulation of LT thickness in Study Example 3, the Euler angles of the piezoelectric layer 2 were fixed to typical values ​​(0°, 36°, 0°), and the Pt electrode thickness was fixed to 13%λ, which is the center point CP in the above-mentioned FEM simulation results.

[0067] As shown in Figures 14A to 14C, it can be seen that the relative bandwidth Δf is 1.1%fr or more when the LT thickness is in the range of 15.0%λ or more. Furthermore, in the range of 15.0%λ or more, the sound velocity V increases as the LT thickness increases, and the value of the sound velocity V is saturated when the LT thickness is 85.0%λ. Based on this result, it can be seen that the relative bandwidth Δf is relatively large and the sound velocity V The point where the LT thickness was relatively slow was selected as the center point CP. That is, the center point CP of the LT thickness in Study Example 3 was set to 40.0%λ.

[0068] (LT cut angle) FIG. 15A is a table showing FEM simulation conditions related to the LT cut angle in Study Example 3. FIG. 15B is a graph showing the results of an FEM simulation of the relationship between the LT cut angle and the fractional bandwidth Δf in Study Example 3. FIG. 15C is a graph showing the results of an FEM simulation of the relationship between the LT cut angle and the sound velocity V in Study Example 3. In the FEM simulation of the LT cut angle in Study Example 3, the Pt electrode thickness was fixed to 13%λ, which is the center point CP in the above-mentioned FEM simulation results. In addition, the LT thickness was fixed to 40.0%λ, which is the center point CP in the above-mentioned FEM simulation results.

[0069] 15A to 15C, the fractional bandwidth Δf is 1.1% fr or more when the LT cut angle is in the range of 0° to 86° and 140° to 180°, in other words, when the LT cut angle is in the range of -40° to 86°. For consistency with other FEM simulations, the center point CP of the LT cut angle was set to 36°. As shown in FIG. 15B, the center point CP of the LT cut angle is located near the maximum point in the fitting curve of the plot of the fractional bandwidth Δf.

[0070] (LT propagation angle) FIG. 16A is a table showing the FEM simulation conditions for the LT propagation angle in Study Example 3. FIG. 16B is a graph showing the results of an FEM simulation of the relationship between the LT propagation angle and the fractional bandwidth Δf in Study Example 3. FIG. 16C is a graph showing the results of an FEM simulation of the relationship between the LT propagation angle and the sound speed V in Study Example 3. In the FEM simulation of the LT propagation angle in Study Example 3, the Pt electrode thickness was fixed to 13%λ, which is the center point CP in the above-mentioned FEM simulation results. In addition, the LT thickness was fixed to 40.0%λ, which is the center point CP in the above-mentioned FEM simulation results, and the LT cut angle was fixed to 36°.

[0071] As shown in Figures 16A to 16C, it can be seen that the fractional bandwidth Δf is 1.1% fr or more when the LT propagation angle is in the range of 0° to 50° and 130° to 180°, in other words, when the LT propagation angle is in the range of -50° to 50°. The fitting curve of the plot of fractional bandwidth Δf shown in Figure 16B actually has an upwardly convex peak because the LT propagation angles of 0° and 180° are equivalent. The maximum point of the fitting curve was selected as the center point CP. In other words, the center point CP of the LT propagation angle was set to 0°.

[0072] <Configuration example 3> In elastic wave device 100 according to Configuration Example 3 of this embodiment, which is based on the FEM simulation results of Study Example 3 described above, the piezoelectric layer 2 is primarily made of lithium tantalate (LT) and has a thickness of 15.0%λ or more and 85.0%λ or less. Furthermore, the Euler angles of piezoelectric layer 2 are (φ, θ, ψ), where φ is between -5° and 5°, θ is between -40° and 86°, and ψ is between -50° and 50°. The IDT electrode 3 is primarily made of Pt and has a thickness of 0.3%λ or more and 74.0%λ or less. The Euler angles of piezoelectric layer 2, φ, are specified to be between -5° and 5° to allow for tolerances for manufacturing errors.

[0073] In elastic wave device 100 according to Configuration Example 3 of this preferred embodiment, piezoelectric layer 2 may be the same as that in Configuration Example 1. Furthermore, IDT electrode 3 may be made of Pt or may consist essentially of Pt. IDT electrode 3 may contain 70% by mass or more, or 80% by mass or more, of Pt. The remainder of the constituent material of IDT electrode 3 other than Pt may consist of optional additive components and unavoidable impurities.

[0074] <Study Example 4: LT film and metal electrode> In the above-mentioned study examples 1 to 3, the electrode materials were Al, Cu, and Pt, respectively, and the piezoelectric layer 2 was an LT film. In contrast, in study example 4, based on the results of the above-mentioned study examples 1 to 3, the electrode material constituting the IDT electrode 3 was further studied when the piezoelectric layer 2 was an LT film.

[0075] FIG. 17A is a table showing the shear wave acoustic velocity of major metal materials. FIG. 17B is a diagram showing a formula for calculating the shear wave acoustic velocity. In the formula shown in FIG. 17B, V is the shear wave acoustic velocity (m / s), E is Young's modulus (Pa), and ρ is density (kg / m 3 ), and γ is Poisson's ratio.

[0076] As shown in FIG. 17A, the shear wave acoustic velocities of Al, Cu, and Pt used in the above-mentioned study examples 1 to 3 are 2571 m / s, 1804 m / s, and 1244 m / s, respectively.

[0077] In the aforementioned study example 1, the center point CP of the Al electrode thickness was 30% λ, the sound velocity (acoustic wave velocity) V at the center point CP was approximately 3000 m / s, and the fractional bandwidth Δf at the center point CP was approximately 1.6 (see FIGS. 5A to 5C). In the aforementioned study example 2, the center point CP of the Cu electrode thickness was 20% λ, the sound velocity (acoustic wave velocity) V at the center point CP was approximately 2500 m / s, and the fractional bandwidth Δf at the center point CP was approximately 2.1 (see FIGS. 9A to 9C). In the aforementioned study example 3, the center point CP of the Pt electrode thickness was 13% λ, the sound velocity (acoustic wave velocity) V at the center point CP was approximately 2300 m / s, and the fractional bandwidth Δf at the center point CP was approximately 2.5 (see FIGS. 13A to 13C).

[0078] Fig. 18A is a graph showing the relationship between the shear wave acoustic velocity of the electrode material and the center point CP of the electrode thickness for the results of Study Examples 1 to 3. Fig. 18B is a graph showing the relationship between the shear wave acoustic velocity of the electrode material and the acoustic velocity (elastic wave acoustic velocity) V for the results of Study Examples 1 to 3. Fig. 18C is a graph showing the relationship between the shear wave acoustic velocity of the electrode material and the fractional bandwidth Δf for the results of Study Examples 1 to 3. Figs. 18A to 18C show a straight line and a coefficient of determination calculated by approximating the plots corresponding to the results of Study Examples 1 to 3 with a linear function. As shown in Figs. 18A to 18C, it can be seen that the shear wave acoustic velocity of the electrode material, the acoustic velocity (elastic wave acoustic velocity) V, and the fractional bandwidth Δf are related to one another by a linear function.

[0079] As shown in Figure 18C, when the shear wave acoustic velocity of the electrode material is 3473 m / s or less, the relative bandwidth Δf is 1.1% fr or more. When an electrode is made of an electrode material with a low shear wave acoustic velocity, energy tends to concentrate around the electrode, resulting in a large relative bandwidth Δf. Furthermore, as shown in Figure 17A, among the major metal materials, Au has the slowest shear wave acoustic velocity, at 658 m / s. Based on this, the lower limit of the shear wave acoustic velocity of the electrode material was set at 500 m / s.

[0080] <Configuration Example 4> In acoustic wave device 100 according to Configuration Example 4 of this embodiment, which was based on the FEM simulation results of Study Examples 1 to 3 and the above-described study results, piezoelectric layer 2 is primarily composed of lithium tantalate and has a thickness of 15.0%λ or more and 90.0%λ or less. Furthermore, piezoelectric layer 2 has Euler angles (φ, θ, ψ) of -5° or more and 5° or less, θ of -40° or more and 86° or less, and ψ of -50° or more and 50° or less. IDT electrode 3 is primarily composed of a metal having a shear wave acoustic velocity of 500 m / s or more and 3473 m / s or less, and has a thickness of 0.2%λ or more and 74.0%λ or less.

[0081] In addition, in an elastic wave device 100 according to another example of Structural Example 4 of the present embodiment, which was based on the FEM simulation results of Study Examples 1 to 3 and the above-described study results, the piezoelectric layer 2 is primarily made of lithium tantalate and has a thickness of 20.0%λ or more and 85.0%λ or less. Furthermore, where the Euler angles of the piezoelectric layer 2 are (φ, θ, ψ), φ is -5° or more and 5° or less, θ is 8° or more and 74° or less, and ψ is -26° or more and 26° or less. The IDT electrode 3 is primarily made of a metal having a shear wave acoustic velocity of 500 m / s or more and 3473 m / s or less, and has a thickness of 0.6%λ or more and 50.0%λ or less.

[0082] In elastic wave device 100 according to Configuration Example 4 or another example of this embodiment, piezoelectric layer 2 may be the same as that in Configuration Example 1. IDT electrode 3 may be made of a metal having a shear wave acoustic velocity of 500 m / s or more and 3473 m / s or less (hereinafter referred to as "specific metal M1"), may be made essentially of specific metal M1, or may be composed mainly of specific metal M1.

[0083] The main component of the material constituting the IDT electrode 3 may be determined depending on the electrode structure of the IDT electrode 3. For example, if the electrode has a laminated structure, the main component may be the material with the highest concentration in the thickest layer of the laminated structure. Alternatively, the average value of the shear wave acoustic velocity of each material of the multiple layers constituting the laminated structure may be regarded as the shear wave acoustic velocity of the material constituting the IDT electrode 3. In this case, the average value may be, for example, in the range of 500 m / s to 3473 m / s. If the electrode has a laminated structure, the acoustic velocity may also be calculated based on, for example, a volume average.

[0084] Alternatively, the electrode in the IDT electrode 3 may be an alloy. When the electrode is an alloy, the material with the highest concentration in the alloy's composition may be the main component. The concentration in the alloy's composition can be measured using, for example, EDX (Energy Dispersive X-ray Spectroscopy) or WDX (Wavelength-Dispersive X-ray Spectroscopy). Alternatively, the shear wave acoustic velocity of the material constituting the IDT electrode 3, calculated based on the alloy's density, Young's modulus, and Poisson's ratio, may be in the range of, for example, 500 m / s to 3473 m / s. The Poisson's ratio is, for example, 0.3 in various alloys.

[0085] <Study example 5: LN film and Al electrode> Next, in Study Example 5, an FEM simulation was performed using Al as the electrode material and an LN film as the piezoelectric layer 2.

[0086] (Al electrode thickness) FIG. 19A is a table showing FEM simulation conditions related to the Al electrode thickness in Study Example 5. FIG. 19B is a graph showing the results of an FEM simulation of the relationship between the Al electrode thickness and the fractional bandwidth Δf in Study Example 5. FIG. 19C is a graph showing the results of an FEM simulation of the relationship between the Al electrode thickness and the sound velocity V in Study Example 5. In the FEM simulation of the Al electrode thickness in Study Example 5, the Euler angles of the piezoelectric layer 2 were fixed to typical values ​​of (0°, 36°, 0°).

[0087] As shown in Figures 19A to 19C, it can be seen that the relative bandwidth Δf is 1.1% fr or more when the Al electrode thickness is in the range of 100% λ or less. An Al electrode thickness exceeding 100% λ is not practical, and an Al electrode thickness that is too thin is also not practical. Therefore, the range of Al electrode thickness can be specified as 0.05% λ or more and 100.0% λ or less. The range of Al electrode thickness may also be specified as 0.05% λ or more and 50.0% λ or less, so that the value of the relative bandwidth Δf is greater than or equal to the value when the Al electrode thickness is 0.05% λ.

[0088] The maximum point in the fitting curve of the plot of the relative bandwidth Δf shown in Fig. 19B was selected as the center point CP. That is, the center point CP of the Al electrode thickness in Study Example 5 was set to 24%λ.

[0089] (LN thickness) FIG. 20A is a table showing FEM simulation conditions related to LN thickness in Study Example 5. FIG. 20B is a graph showing the results of an FEM simulation of the relationship between LN thickness and fractional bandwidth Δf in Study Example 5. FIG. 20C is a graph showing the results of an FEM simulation of the relationship between LN thickness and sound velocity V in Study Example 5. In the FEM simulation of LN thickness in Study Example 5, the Euler angles of the piezoelectric layer 2 were fixed to typical values ​​(0°, 36°, 0°), and the Al electrode thickness was fixed to 24%λ, which is the center point CP in the above-mentioned FEM simulation results.

[0090] As shown in Figures 20A to 20C, it can be seen that the relative bandwidth Δf is 1.1%fr or more when the LN thickness is in the range of 10.0%λ or more. Furthermore, in the range of 10.0%λ or more, the sound velocity V increases as the LN thickness increases, and the value of the sound velocity V saturates when the LN thickness is 92.5%λ. Based on this result, it can be seen that the relative bandwidth Δf is relatively large and the sound velocity V The point where the temperature was relatively slow was selected as the center point CP. That is, the center point CP of the LN thickness in Study Example 5 was set to 35.0%λ.

[0091] (LN cut angle) 21A is a table showing FEM simulation conditions related to the LN cut angle in Study Example 5. FIG. 21B is a graph showing the results of an FEM simulation of the relationship between the LN cut angle and the fractional bandwidth Δf in Study Example 5. FIG. 21C is a graph showing the results of an FEM simulation of the relationship between the LN cut angle and the sound velocity V in Study Example 5. In the FEM simulation of the LN cut angle in Study Example 5, the Al electrode thickness was fixed at 24% λ, which is the center point CP in the above-mentioned FEM simulation results, and the LN thickness was fixed at 35.0% λ, which is the center point CP in the above-mentioned FEM simulation results.

[0092] 21A to 21C, the fractional bandwidth Δf is 1.1% fr or more when the LN cut angle is in the range of 0° to 90° and 142° to 180°, in other words, when the LN cut angle is in the range of -38° to 90°. For consistency with other FEM simulations, the center point CP of the LN cut angle was set to 36°. As shown in FIG. 21B, the center point CP of the LN cut angle is located near the maximum point in the fitting curve of the plot of the fractional bandwidth Δf.

[0093] (LN propagation angle) FIG. 22A is a table showing FEM simulation conditions for the LN propagation angle in Study Example 5. FIG. 22B is a graph showing the results of an FEM simulation of the relationship between the LN propagation angle and the fractional bandwidth Δf in Study Example 5. FIG. 22C is a graph showing the results of an FEM simulation of the relationship between the LN propagation angle and the sound speed V in Study Example 5. In the FEM simulation of the LN propagation angle in Study Example 5, the Al electrode thickness was fixed at 24%λ, which is the center point CP in the above-mentioned FEM simulation results. In addition, the LN thickness was fixed at 35.0%λ, which is the center point CP in the above-mentioned FEM simulation results, and the LN cut angle was fixed at 36°.

[0094] As shown in Figures 22A to 22C, the fractional bandwidth Δf is 1.1% fr or more when the LN propagation angle is in the range of 0° to 50° and 130° to 180°, in other words, when the LN propagation angle is in the range of -50° to 50°. The fitting curve of the plot of fractional bandwidth Δf shown in Figure 22B has an upwardly convex peak because the LN propagation angles of 0° and 180° are equivalent. The maximum point of the fitting curve was selected as the center point CP. In other words, the center point CP of the LN propagation angle was set to 0°.

[0095] <Configuration example 5> In acoustic wave device 100 according to Configuration Example 5 of this embodiment, which is based on the FEM simulation results of Study Example 5 described above, the piezoelectric layer 2 is made primarily of lithium niobate and has a thickness of 10.0%λ or more and 92.5%λ or less. Furthermore, where the Euler angles of piezoelectric layer 2 are (φ, θ, ψ), φ is -5° or more and 5° or less, θ is -38° or more and 90° or less, and ψ is -50° or more and 50° or less. The IDT electrode 3 is made primarily of Al and has a thickness of 0.05%λ or more and 100.0%λ or less.

[0096] In elastic wave device 100 according to Configuration Example 5 of this preferred embodiment, piezoelectric layer 2 may be made of LN or may consist essentially of LN. Piezoelectric layer 2 may contain 70 mass % or more, or 80 mass % or more, of LN. The remainder of the constituent material of piezoelectric layer 2 other than LN may consist of optional additive components and unavoidable impurities.

[0097] The IDT electrode 3 may be made of Al or may consist essentially of Al. The IDT electrode 3 may contain 70 mass % or more, or 80 mass % or more, of Al. The remainder of the constituent material of the IDT electrode 3 other than Al may consist of optional additive components and unavoidable impurities.

[0098] <Study Example 6: LN film and Cu electrode> In Study Example 6, an FEM simulation was performed using Cu as the electrode material and an LN film as the piezoelectric layer 2.

[0099] (Cu electrode thickness) Fig. 23A is a table showing FEM simulation conditions for the Cu electrode thickness in Study Example 6. Fig. 23B is a graph showing the results of an FEM simulation of the relationship between the Cu electrode thickness and the fractional bandwidth Δf in Study Example 6. Fig. 23C is a graph showing the results of an FEM simulation of the relationship between the Cu electrode thickness and the sound velocity V in Study Example 6. In the FEM simulation of the Cu electrode thickness in Study Example 6, the Euler angles of the piezoelectric layer 2 were fixed to typical values ​​of (0°, 36°, 0°).

[0100] As shown in Figures 23A to 23C, the relative bandwidth Δf is 1.1% fr or more when the Cu electrode thickness is in the range of 100% λ or less. A Cu electrode thickness exceeding 100% λ is not practical, and a Cu electrode thickness that is too thin is also not practical. Therefore, the range of Cu electrode thickness can be specified as 0.05% λ or more and 100.0% λ or less. The range of Cu electrode thickness may also be specified as 0.05% λ or more and 66.0% λ or less, so that the value of the relative bandwidth Δf is greater than or equal to the value when the Cu electrode thickness is 0.05% λ.

[0101] The maximum point in the fitting curve of the plot of the relative bandwidth Δf shown in Fig. 23B was selected as the center point CP. That is, the center point CP of the Cu electrode thickness in Study Example 6 was set to 18%λ.

[0102] (LN thickness) FIG. 24A is a table showing FEM simulation conditions related to LN thickness in Study Example 6. FIG. 24B is a graph showing the results of an FEM simulation of the relationship between LN thickness and fractional bandwidth Δf in Study Example 6. FIG. 24C is a graph showing the results of an FEM simulation of the relationship between LN thickness and sound velocity V in Study Example 6. In the FEM simulation of LN thickness in Study Example 6, the Euler angles of the piezoelectric layer 2 were fixed to typical values ​​(0°, 36°, 0°), and the Cu electrode thickness was fixed to 18%λ, which is the center point CP in the above-mentioned FEM simulation results.

[0103] As shown in Figures 24A to 24C, it can be seen that the relative bandwidth Δf is 1.1%fr or more when the LN thickness is in the range of 7.5%λ or more. Furthermore, in the range of 7.5%λ or more, the sound velocity V increases as the LN thickness increases, and the value of the sound velocity V saturates when the LN thickness is 85.0%λ. Based on this result, it can be seen that the relative bandwidth Δf is relatively large and the sound velocity V The point where the temperature was relatively slow was selected as the center point CP. That is, the center point CP of the LN thickness in Study Example 6 was set to 32.5%λ.

[0104] (LN cut angle) 25A is a table showing FEM simulation conditions related to the LN cut angle in Study Example 6. FIG. 25B is a graph showing the results of an FEM simulation of the relationship between the LN cut angle and the fractional bandwidth Δf in Study Example 6. FIG. 25C is a graph showing the results of an FEM simulation of the relationship between the LN cut angle and the sound velocity V in Study Example 6. In the FEM simulation of the LN cut angle in Study Example 6, the Cu electrode thickness was fixed at 18%λ, which is the center point CP in the above-mentioned FEM simulation results, and the LN thickness was fixed at 32.5%λ, which is the center point CP in the above-mentioned FEM simulation results.

[0105] 25A to 25C, the fractional bandwidth Δf is 1.1% fr or more when the LN cut angle is in the range of 0° to 84° and 128° to 180°, in other words, when the LN cut angle is in the range of -52° to 84°. For consistency with other FEM simulations, the center point CP of the LN cut angle was set to 36°. As shown in FIG. 25B, the center point CP of the LN cut angle is located near the maximum point in the fitting curve of the plot of the fractional bandwidth Δf.

[0106] (LN propagation angle) FIG. 26A is a table showing FEM simulation conditions for the LN propagation angle in Study Example 6. FIG. 26B is a graph showing the results of an FEM simulation of the relationship between the LN propagation angle and the fractional bandwidth Δf in Study Example 6. FIG. 26C is a graph showing the results of an FEM simulation of the relationship between the LN propagation angle and the sound speed V in Study Example 6. In the FEM simulation of the LN propagation angle in Study Example 6, the Cu electrode thickness was fixed at 18%λ, which is the center point CP in the above-mentioned FEM simulation results. In addition, the LN thickness was fixed at 32.5%λ, which is the center point CP in the above-mentioned FEM simulation results, and the LN cut angle was fixed at 36°.

[0107] As shown in Figures 26A to 26C, the fractional bandwidth Δf is 1.1% fr or more when the LN propagation angle is in the range of 0° to 58° and 122° to 180°, in other words, when the LN propagation angle is in the range of -58° to 58°. The fitting curve of the plot of fractional bandwidth Δf shown in Figure 26B actually has an upwardly convex peak because the LN propagation angles of 0° and 180° are equivalent. The maximum point of the fitting curve was selected as the center point CP. In other words, the center point CP of the LN propagation angle was set to 0°.

[0108] <Configuration Example 6> In elastic wave device 100 according to Configuration Example 6 of this embodiment, which is based on the results of the FEM simulation described above, the piezoelectric layer 2 is made primarily of lithium niobate and has a thickness of 7.5%λ or more and 85.0%λ or less. Furthermore, where the Euler angles of piezoelectric layer 2 are (φ, θ, ψ), φ is -5° or more and 5° or less, θ is -52° or more and 84° or less, and ψ is -58° or more and 58° or less. The IDT electrode 3 is made primarily of Cu and has a thickness of 0.05%λ or more and 100.0%λ or less.

[0109] In elastic wave device 100 according to Configuration Example 6 of this preferred embodiment, piezoelectric layer 2 may be the same as that in Configuration Example 5. Furthermore, IDT electrode 3 may be made of Cu, or may be made essentially of Cu. IDT electrode 3 may contain 70% by mass or more of Cu, or may contain 80% by mass or more of Cu. The remainder of the constituent material of IDT electrode 3 other than Cu may be made of optional additive components and unavoidable impurities.

[0110] <Study Example 7: LN film and Pt electrode> In Study Example 7, an FEM simulation was performed using Pt as the electrode material and an LN film as the piezoelectric layer 2.

[0111] (Pt electrode thickness) FIG. 27A is a table showing FEM simulation conditions related to the Pt electrode thickness in Study Example 7. FIG. 27B is a graph showing the results of an FEM simulation of the relationship between the Pt electrode thickness and the fractional bandwidth Δf in Study Example 7. FIG. 27C is a graph showing the results of an FEM simulation of the relationship between the Pt electrode thickness and the sound velocity V in Study Example 7. In the FEM simulation of the Pt electrode thickness in Study Example 7, the Euler angles of the piezoelectric layer 2 were fixed to typical values ​​of (0°, 36°, 0°).

[0112] As shown in Figures 27A to 27C, the relative bandwidth Δf is 1.1% fr or more when the Pt electrode thickness is in the range of 100% λ or less. A Pt electrode thickness exceeding 100% λ is not practical, and a Pt electrode thickness that is too thin is also not practical. Therefore, the Pt electrode thickness range can be specified as 0.05% λ or more and 100.0% λ or less. The Pt electrode thickness range may also be specified as 0.05% λ or more and 86.0% λ or less, as a range within which the relative bandwidth Δf value is greater than or equal to the value when the Pt electrode thickness is 0.05% λ.

[0113] The maximum point in the fitting curve of the plot of the relative bandwidth Δf shown in Fig. 27B was selected as the center point CP. That is, the center point CP of the Pt electrode thickness in Study Example 7 was set to 12%λ.

[0114] (LN thickness) FIG. 28A is a table showing FEM simulation conditions related to LN thickness in Study Example 7. FIG. 28B is a graph showing the results of an FEM simulation of the relationship between LN thickness and fractional bandwidth Δf in Study Example 7. FIG. 28C is a graph showing the results of an FEM simulation of the relationship between LN thickness and sound velocity V in Study Example 7. In the FEM simulation of LN thickness in Study Example 7, the Euler angles of the piezoelectric layer 2 were fixed to typical values ​​(0°, 36°, 0°), and the Pt electrode thickness was fixed to 12%λ, which is the center point CP in the above-mentioned FEM simulation results.

[0115] As shown in Figures 28A to 28C, it can be seen that the relative bandwidth Δf is 1.1%fr or more when the LN thickness is in the range of 7.5%λ or more. Furthermore, in the range of 7.5%λ or more, the sound velocity V increases as the LN thickness increases, and the value of the sound velocity V saturates at an LN thickness of 82.5%λ. Based on this result, it can be seen that the relative bandwidth Δf is relatively large and the sound velocity V The point where the temperature was relatively slow was selected as the center point CP. That is, the center point CP of the LN thickness in Study Example 7 was set to 32.5%λ.

[0116] (LN cut angle) FIG. 29A is a table showing FEM simulation conditions related to the LN cut angle in Study Example 7. FIG. 29B is a graph showing the results of an FEM simulation of the relationship between the LN cut angle and the fractional bandwidth Δf in Study Example 7. FIG. 29C is a graph showing the results of an FEM simulation of the relationship between the LN cut angle and the sound velocity V in Study Example 7. In the FEM simulation of the LN cut angle in Study Example 7, the Pt electrode thickness was fixed at 12%λ, which is the center point CP in the above-mentioned FEM simulation results. In addition, the LN thickness was fixed at 32.5%λ, which is the center point CP in the above-mentioned FEM simulation results.

[0117] 29A to 29C, the fractional bandwidth Δf is 1.1% fr or more when the LN cut angle is in the range of 0° to 86° and 122° to 180°, in other words, when the LN cut angle is in the range of -58° to 86°. For consistency with other FEM simulations, the center point CP of the LN cut angle was set to 36°. As shown in FIG. 29B, the center point CP of the LN cut angle is located near the maximum point in the fitting curve of the plot of the fractional bandwidth Δf.

[0118] (LN propagation angle) FIG. 30A is a table showing FEM simulation conditions for the LN propagation angle in Study Example 7. FIG. 30B is a graph showing the results of an FEM simulation of the relationship between the LN propagation angle and the fractional bandwidth Δf in Study Example 7. FIG. 30C is a graph showing the results of an FEM simulation of the relationship between the LN propagation angle and the sound speed V in Study Example 7. In the FEM simulation of the LN propagation angle in Study Example 7, the Pt electrode thickness was fixed to 12%λ, which is the center point CP in the above-mentioned FEM simulation results. In addition, the LN thickness was fixed to 32.5%λ, which is the center point CP in the above-mentioned FEM simulation results, and the LN cut angle was fixed to 36°.

[0119] As shown in Figures 30A to 30C, the fractional bandwidth Δf is 1.1% fr or more when the LN propagation angle is in the range of 0° to 64° and 116° to 180°, in other words, when the LN propagation angle is in the range of -64° to 64°. The fitting curve of the plot of fractional bandwidth Δf shown in Figure 30B has an upwardly convex peak because the LN propagation angles of 0° and 180° are equivalent. The maximum point of the fitting curve was selected as the center point CP. In other words, the center point CP of the LN propagation angle was set to 0°.

[0120] <Configuration Example 7> In elastic wave device 100 according to Configuration Example 7 of this embodiment, which is based on the results of the FEM simulation described above, the piezoelectric layer 2 is made primarily of lithium niobate and has a thickness of 7.5%λ or more and 82.5%λ or less. Furthermore, where the Euler angles of piezoelectric layer 2 are (φ, θ, ψ), φ is -5° or more and 5° or less, θ is -58° or more and 86° or less, and ψ is -64° or more and 64° or less. The IDT electrode 3 is made primarily of Pt and has a thickness of 0.05%λ or more and 100.0%λ or less.

[0121] In elastic wave device 100 according to Configuration Example 7 of this preferred embodiment, piezoelectric layer 2 may be the same as that in Configuration Example 5. Furthermore, IDT electrode 3 may be made of Pt, or may consist essentially of Pt. IDT electrode 3 may contain 70% by mass or more, or 80% by mass or more, of Pt. The remainder of the constituent material of IDT electrode 3 other than Pt may consist of optional additive components and unavoidable impurities.

[0122] <Study Example 8: LN film and metal electrode> In the above-mentioned study examples 5 to 7, the electrode materials were Al, Cu, and Pt, respectively, and the piezoelectric layer 2 was an LN film. In contrast, in study example 8, based on the results of the above-mentioned study examples 5 to 7, the electrode material constituting the IDT electrode 3 was further studied when the piezoelectric layer 2 was an LN film.

[0123] The explanation of Study Example 4 above using FIGS. 17A and 17B is also applicable to Study Example 8, and therefore will not be repeated.

[0124] In Study Example 5, the center point CP of the Al electrode thickness was 24% λ, the sound velocity (acoustic wave velocity) V at the center point CP was approximately 3100 m / s, and the fractional bandwidth Δf at the center point CP was approximately 4.2 (see FIGS. 19A to 19C). In Study Example 6, the center point CP of the Cu electrode thickness was 18% λ, the sound velocity (acoustic wave velocity) V at the center point CP was approximately 2600 m / s, and the fractional bandwidth Δf at the center point CP was approximately 5.3 (see FIGS. 23A to 23C). In Study Example 7, the center point CP of the Pt electrode thickness was 12% λ, the sound velocity (acoustic wave velocity) V at the center point CP was approximately 2300 m / s, and the fractional bandwidth Δf at the center point CP was approximately 6.0 (see FIGS. 27A to 27C).

[0125] FIG. 31A is a graph showing the relationship between the shear wave acoustic velocity of the electrode material and the center point CP of the electrode thickness for the results of Study Examples 5 to 7. FIG. 31B is a graph showing the relationship between the shear wave acoustic velocity of the electrode material and the acoustic velocity (elastic wave acoustic velocity) V for the results of Study Examples 5 to 7. FIG. 31C is a graph showing the relationship between the shear wave acoustic velocity of the electrode material and the fractional bandwidth Δf for the results of Study Examples 5 to 7. FIGS. 31A to 31C show a straight line and a coefficient of determination calculated by approximating the plots corresponding to the results of Study Examples 5 to 7 with a linear function. As shown in FIGS. 31A to 31C, it can be seen that the shear wave acoustic velocity of the electrode material, the acoustic velocity (elastic wave acoustic velocity) V, and the fractional bandwidth Δf are all related by a linear function.

[0126] As shown in Figure 31C, when the shear wave acoustic velocity of the electrode material is approximately 5000 m / s or less, the relative bandwidth Δf is 1.1% fr or more. Here, the acoustic velocity of conventional SAW is approximately 4000 m / s. Conventional SAW includes Rayleigh waves and leaky waves. The acoustic velocity of leaky waves propagating through the LT film is approximately 4000 m / s. Therefore, as shown in Figure 31B, the upper limit of the shear wave acoustic velocity of the electrode material was set to 4005 m / s, which is the range in which the acoustic velocity (acoustic wave velocity) V is slower than that of conventional SAW. Furthermore, as in the above-mentioned Study Example 4, the lower limit of the shear wave acoustic velocity of the electrode material was set to 500 m / s.

[0127] <Configuration Example 8> In acoustic wave device 100 according to Configuration Example 8 of this preferred embodiment, which was based on the FEM simulation results of Study Examples 5 to 7 and the above-described study results, piezoelectric layer 2 is primarily composed of lithium niobate and has a thickness of 7.5%λ or more and 92.5%λ or less. Furthermore, piezoelectric layer 2 has Euler angles (φ, θ, ψ) of -5° or more and 5° or less, θ of -58° or more and 90° or less, and ψ of -64° or more and 64° or less. IDT electrode 3 is primarily composed of a metal having a shear wave acoustic velocity of 500 m / s or more and 4005 m / s or less, and has a thickness of 0.05%λ or more and 100.0%λ or less.

[0128] In acoustic wave device 100 according to another example of configuration example 8 of the present embodiment, which was based on the FEM simulation results of study examples 5 to 7 and the above-described study results, piezoelectric layer 2 is primarily composed of lithium niobate and has a thickness of 10.0%λ or more and 82.5%λ or less. Furthermore, piezoelectric layer 2 has Euler angles (φ, θ, ψ) of -5° or more and 5° or less, θ of -38° or more and 84° or less, and ψ of -50° or more and 50° or less. IDT electrode 3 is primarily composed of a metal having a shear wave acoustic velocity of 500 m / s or more and 4005 m / s or less, and has a thickness of 0.05%λ or more and 100.0%λ or less.

[0129] In elastic wave device 100 according to Configuration Example 8 of this preferred embodiment or another example thereof, piezoelectric layer 2 may be the same as that in Configuration Example 5. Furthermore, IDT electrode 3 may be made of a metal having a shear wave acoustic velocity of 500 m / s or more and 4005 m / s or less (hereinafter referred to as "specific metal M2"), may be made essentially of specific metal M2, or may be made mainly of specific metal M2. The relationship between the material of IDT electrode 3 and the range of shear wave acoustic velocity is the same as that described above for Configuration Example 4, and therefore will not be described again.

[0130] <Other structural examples> 32 is a perspective view showing another example structure of elastic wave device 100 according to this preferred embodiment. As described above, elastic wave device 100 according to this preferred embodiment may be configured to excite A0 mode Lamb waves, and the specific shape of IDT electrode 3 is not particularly limited. For example, as shown in FIG. 32, elastic wave device 100 may include a transversal resonator 1.

[0131] 32, the resonator 1 may have a first IDT electrode 130 (input IDT electrode) and a second IDT electrode 230 (output IDT electrode) arranged in the X direction. The first IDT electrode 130 may have two bus bars 131 (first bus bar 131a and second bus bar 131b) facing each other in the y direction. The second IDT electrode 230 may have two bus bars 231 (first bus bar 231a and second bus bar 231b) facing each other in the y direction.

[0132] For example, the input terminal Tin may be connected to the first bus bar 131a of the first IDT electrode 130, and the output terminal Tout may be connected to the second bus bar 231b of the second IDT electrode 230. The second bus bar 131b of the first IDT electrode 130 and the first bus bar 231a of the second IDT electrode 230 may each be connected to a ground terminal.

[0133] 32, acoustic wave device 100 may include third electrode 14 in the propagation path between first IDT electrode 130 and second IDT electrode 230. Third electrode 14 may be, for example, an aluminum electrode film and has the function of improving the propagation efficiency of a signal (A0 mode Lamb wave) from first IDT electrode 130 to second IDT electrode 230. Third electrode 14 may or may not be connected to a ground terminal. Acoustic wave device 100 does not necessarily require third electrode 14.

[0134] In the acoustic wave device 100, the first IDT electrode 130 and the second IDT electrode 230 may each have the same shape and component ratio as the aforementioned IDT electrode 3. A known configuration may be adopted for the third electrode 14.

[0135] <Other configuration 1> 33 is a cross-sectional view showing another example configuration of elastic wave device 100 according to this preferred embodiment. In the example shown in Fig. 33, resonator 1 included in elastic wave device 100 may have an acoustic reflection film between support substrate 5 and piezoelectric layer 2. The specific structure of the acoustic reflection film is not particularly limited, and elastic wave device 100 may have a reflective multilayer film 60 between support substrate 5 and piezoelectric layer 2, for example.

[0136] The reflective multilayer film 60 may include first layers 61 and second layers 62 stacked alternately. The material of the first layer 61 may have a lower acoustic impedance than the material of the second layer 62. For example, the first layer 61 may be mainly composed of silicon dioxide (SiO2). For example, the second layer 62 may be mainly composed of hafnium oxide (HfO2). The second layer 62 may be mainly composed of any of tantalum pentoxide (Ta2O5), zirconium dioxide (ZrO2), titanium oxide (TiO2), and magnesium oxide (MgO). The reflective multilayer film 60 may include at least one first layer 61 and at least one second layer 62. The layer in contact with the piezoelectric layer 2 in the reflective multilayer film 60 is the first layer 61. On the other hand, the layer in the reflective multilayer film 60 that is closest to the support substrate 5 may be either the first layer 61 or the second layer 62. For example, the reflective multilayer film 60 may include a total of three to twelve first layers 61 and second layers 62.

[0137] <Other configuration 2> 34 is a cross-sectional view showing another modified example of elastic wave device 100 according to this preferred embodiment. In the example shown in Fig. 34, resonator 1 included in elastic wave device 100 may have at least a portion of IDT electrode 3 embedded in piezoelectric layer 2.

[0138] 34, the top surfaces of the electrode fingers 32 and the top surface of the piezoelectric layer 2 are aligned (flush), but this is not limiting. For example, the IDT electrode 3 may be embedded in the piezoelectric layer 2 so that the top surfaces of the electrode fingers 32 are convex or concave relative to the top surface of the piezoelectric layer 2. This can effectively reduce spurious emissions.

[0139] <Other configuration 3> The resonant frequency of the acoustic wave device 100 may be, for example, 700 MHz or more and 900 MHz or less. When the cross-sectional thicknesses (expressed as %λ) of the piezoelectric layer 2 and the IDT electrode 3 are constant, the acoustic velocity V of the A0 mode Lamb wave is also constant. Since V = fλ (V: constant), the resonant frequency can be adjusted by varying λ (in other words, the electrode finger pitch p). Conversely, λ is set to achieve the desired resonant frequency, and the cross-sectional thicknesses (expressed as %λ) of the piezoelectric layer 2 and the IDT electrode 3 are calculated based on the set λ. A resonator 1 having a piezoelectric layer 2 and an IDT electrode 3 with the calculated thicknesses can then be fabricated.

[0140] <Communication Device> FIG. 35 is a diagram illustrating a schematic configuration of a communication device 151. The communication device 151 is an application example of the elastic wave device 100 according to one embodiment of the present disclosure and performs wireless communication using radio waves. The communication device 151 may include one duplexer 101 as the transmit filter 109 and another duplexer 101 as the receive filter 111. Each of the two duplexers 101 may include an elastic wave device 100 according to one embodiment of the present disclosure. In this manner, the communication device 151 may include an elastic wave device 100 according to one embodiment of the present disclosure.

[0141] In communication device 151, a transmission information signal TIS containing information to be transmitted may be modulated and frequency-raised (converted into a high-frequency signal having a carrier frequency) by RF-IC (Radio Frequency-Integrated Circuit) 153, and converted into a transmission signal TS. Bandpass filter 155 may remove unnecessary components from the TS outside the transmission passband. Next, the TS after removing the unnecessary components may be amplified by amplifier 157 and input to transmission filter 109.

[0142] The transmission filter 109 may remove unnecessary components outside the transmission passband from the input transmission signal TS. The transmission filter 109 may output the TS after removing the unnecessary components to the antenna 159 via the antenna terminal. The antenna 159 may convert the TS, which is an electrical signal input thereto, into radio waves as a wireless signal and transmit the radio waves to the outside of the communication device 151.

[0143] Furthermore, the antenna 159 may convert the received external radio waves into a received signal RS, which is an electrical signal, and input the RS to the receiving filter 111 via the antenna terminal. The receiving filter 111 may remove unwanted components outside the receiving passband from the input RS. The receiving filter 111 may output the received signal RS after the unwanted components have been removed to the amplifier 161. The output RS may be amplified by the amplifier 161. The bandpass filter 163 may remove unwanted components outside the receiving passband from the amplified RS. The RS after the unwanted components have been removed may be frequency-downshifted and demodulated by the RF-IC 153, and converted into a received information signal RIS.

[0144] The TIS and RIS may be low-frequency signals (baseband signals) containing appropriate information. For example, the TIS and RIS may be analog audio signals or digitized audio signals. The passband of the wireless signals may be set appropriately and may comply with various known standards.

[0145] [Additional notes] The invention according to the present disclosure has been described above based on various drawings and examples. However, the invention according to the present disclosure is not limited to the above-described embodiments and examples. In other words, the invention according to the present disclosure can be modified in various ways within the scope of the present disclosure, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments and examples are also included in the technical scope of the invention according to the present disclosure. In other words, it should be noted that a person skilled in the art can easily make various modifications or corrections based on the present disclosure. It should also be noted that these modifications or corrections are included in the scope of the present disclosure. [Explanation of symbols]

[0146] 1 resonator 2 Piezoelectric layer 3 IDT electrode 31 Busbar 32 Electrode finger 4 reflector 5 Support substrate 6. Middle class 100 Elastic Wave Device

Claims

1. A support substrate; a piezoelectric layer that is in direct or indirect contact with the support substrate; an IDT electrode located on the piezoelectric layer, Exciting an asymmetrical zeroth mode Lamb wave as the main mode, The wavelength λ of the asymmetric zeroth mode Lamb wave is defined as twice the length of the pitch of the plurality of electrode fingers included in the IDT electrode, The piezoelectric layer is The main component of the material is lithium tantalate. The thickness is 17.5%λ or more and 90.0%λ or less, where the Euler angles are (φ, θ, ψ), φ is between −5° and 5°, θ is between −20° and 80°, and ψ is between −40° and 40°, The IDT electrode is The main component of the constituent material is Cu, An elastic wave device having a thickness of 0.2%λ or more and 58.0%λ or less.

2. A support substrate; a piezoelectric layer that is in direct or indirect contact with the support substrate; an IDT electrode located on the piezoelectric layer, Exciting an asymmetric zeroth mode Lamb wave, The wavelength λ of the asymmetric zeroth mode Lamb wave is defined as twice the length of the pitch of the plurality of electrode fingers included in the IDT electrode, The piezoelectric layer is The main component of the material is lithium tantalate. The thickness is 20.0%λ or more and 87.5%λ or less, where the Euler angles are (φ, θ, ψ), φ is between -5° and 5°, θ is between 8° and 74°, and ψ is between -26° and 26°, The IDT electrode is The main component of the constituent material is Al, An elastic wave device having a thickness of 0.6%λ or more and 50.0%λ or less.

3. A support substrate; a piezoelectric layer that is in direct or indirect contact with the support substrate; an IDT electrode located on the piezoelectric layer, Exciting an asymmetrical zeroth mode Lamb wave as the main mode, The wavelength λ of the asymmetric zeroth mode Lamb wave is defined as twice the length of the pitch of the plurality of electrode fingers included in the IDT electrode, The piezoelectric layer is The main component of the material is lithium tantalate. The thickness is 15.0%λ or more and 85.0%λ or less, where the Euler angles are (φ, θ, ψ), φ is between -5° and 5°, θ is between -40° and 86°, and ψ is between -50° and 50°, The IDT electrode is The main component of the constituent material is Pt, An elastic wave device having a thickness of 0.3%λ or more and 74.0%λ or less.

4. A support substrate; a piezoelectric layer that is in direct or indirect contact with the support substrate; an IDT electrode located on the piezoelectric layer, Exciting an asymmetrical zeroth mode Lamb wave as the main mode, The wavelength λ of the asymmetric zeroth mode Lamb wave is defined as twice the length of the pitch of the plurality of electrode fingers included in the IDT electrode, The piezoelectric layer is The main component of the material is lithium tantalate. The thickness is 15.0%λ or more and 90.0%λ or less, where the Euler angles are (φ, θ, ψ), φ is between -5° and 5°, θ is between -40° and 86°, and ψ is between -50° and 50°, The IDT electrode is The main component of the constituent material is a metal having a shear wave velocity of 500 m / s or more and 3473 m / s or less, An elastic wave device having a thickness of 0.2%λ or more and 74.0%λ or less.

5. A support substrate; a piezoelectric layer that is in direct or indirect contact with the support substrate; an IDT electrode located on the piezoelectric layer, Exciting an asymmetric zeroth mode Lamb wave, The wavelength λ of the asymmetric zeroth mode Lamb wave is defined as twice the length of the pitch of the plurality of electrode fingers included in the IDT electrode, The piezoelectric layer is The main component of the material is lithium tantalate. The thickness is 20.0%λ or more and 85.0%λ or less, where the Euler angles are (φ, θ, ψ), φ is between -5° and 5°, θ is between 8° and 74°, and ψ is between -26° and 26°, The IDT electrode is The main component of the constituent material is a metal having a shear wave velocity of 500 m / s or more and 3473 m / s or less, An elastic wave device having a thickness of 0.6%λ or more and 50.0%λ or less.

6. A support substrate; a piezoelectric layer that is in direct or indirect contact with the support substrate; an IDT electrode located on the piezoelectric layer, Exciting an asymmetrical zeroth mode Lamb wave as the main mode, The wavelength λ of the asymmetric zeroth mode Lamb wave is defined as twice the length of the pitch of the plurality of electrode fingers included in the IDT electrode, The piezoelectric layer is The main component of the material is lithium niobate. The thickness is 10.0%λ or more and 92.5%λ or less, where the Euler angles are (φ, θ, ψ), φ is between −5° and 5°, θ is between −38° and 90°, and ψ is between −50° and 50°, The IDT electrode is The main component of the constituent material is Al, An elastic wave device having a thickness of 0.05% λ or more and 100.0% λ or less.

7. A support substrate; a piezoelectric layer that is in direct or indirect contact with the support substrate; an IDT electrode located on the piezoelectric layer, Exciting an asymmetrical zeroth mode Lamb wave as the main mode, The wavelength λ of the asymmetric zeroth mode Lamb wave is defined as twice the length of the pitch of the plurality of electrode fingers included in the IDT electrode, The piezoelectric layer is The main component of the material is lithium niobate. The thickness is 7.5%λ or more and 85.0%λ or less, where the Euler angles are (φ, θ, ψ), φ is between −5° and 5°, θ is between −52° and 84°, and ψ is between −58° and 58°, The IDT electrode is The main component of the constituent material is Cu, An elastic wave device having a thickness of 0.05% λ or more and 100.0% λ or less.

8. A support substrate; a piezoelectric layer that is in direct or indirect contact with the support substrate; an IDT electrode located on the piezoelectric layer, Exciting an asymmetrical zeroth mode Lamb wave as the main mode, The wavelength λ of the asymmetric zeroth mode Lamb wave is defined as twice the length of the pitch of the plurality of electrode fingers included in the IDT electrode, The piezoelectric layer is The main component of the material is lithium niobate. The thickness is 7.5%λ or more and 82.5%λ or less, where the Euler angles are (φ, θ, ψ), φ is between −5° and 5°, θ is between −58° and 86°, and ψ is between −64° and 64°, The IDT electrode is The main component of the constituent material is Pt, An elastic wave device having a thickness of 0.05% λ or more and 100.0% λ or less.

9. A support substrate; a piezoelectric layer that is in direct or indirect contact with the support substrate; an IDT electrode located on the piezoelectric layer, Exciting an asymmetrical zeroth mode Lamb wave as the main mode, The wavelength λ of the asymmetric zeroth mode Lamb wave is defined as twice the length of the pitch of the plurality of electrode fingers included in the IDT electrode, The piezoelectric layer is The main component of the material is lithium niobate. The thickness is 7.5%λ or more and 92.5%λ or less, where the Euler angles are (φ, θ, ψ), φ is between -5° and 5°, θ is between -58° and 90°, and ψ is between -64° and 64°, The IDT electrode is The main component of the constituent material is a metal having a shear wave velocity of 500 m / s or more and 4005 m / s or less, An elastic wave device having a thickness of 0.05% λ or more and 100.0% λ or less.

10. A support substrate; a piezoelectric layer that is in direct or indirect contact with the support substrate; an IDT electrode located on the piezoelectric layer, Exciting an asymmetrical zeroth mode Lamb wave as the main mode, The wavelength λ of the asymmetric zeroth mode Lamb wave is defined as twice the length of the pitch of the plurality of electrode fingers included in the IDT electrode, The piezoelectric layer is The main component of the material is lithium niobate. The thickness is 10.0%λ or more and 82.5%λ or less, where the Euler angles are (φ, θ, ψ), φ is between −5° and 5°, θ is between −38° and 84°, and ψ is between −50° and 50°, The IDT electrode is The main component of the constituent material is a metal having a shear wave velocity of 500 m / s or more and 4005 m / s or less, An elastic wave device having a thickness of 0.05% λ or more and 100.0% λ or less.

11. The acoustic wave device according to claim 1 , further comprising an intermediate layer between the support substrate and the piezoelectric layer.

12. The acoustic wave device according to claim 1 , further comprising an acoustic reflection film between the support substrate and the piezoelectric layer.

13. The acoustic wave device according to claim 1 , wherein the relative bandwidth is 1.1% or greater.

14. The acoustic wave device according to claim 1 , wherein at least a portion of the IDT electrode is embedded in the piezoelectric layer.

15. A communication device comprising the acoustic wave device according to claim 1 .

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