Acoustic wave devices and communication devices

Abstract

In order to reduce the spurious emission from an acoustic wave device using lamb waves, in this acoustic wave device using lamb waves at least a portion of an electrode is embedded in a piezoelectric substance.

Description

[Technical Field]

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

[0002] Patent Document 1 discloses an elastic wave device that utilizes Lamb waves, particularly the antisymmetric A1 mode.

[0003] Furthermore, for example, Patent Documents 2 to 12 disclose acoustic wave devices in which electrodes are embedded in a piezoelectric body. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. WO2012 / 086441 [Patent Document 2] International Publication No. WO2020 / 204045 [Patent Document 3] Japanese Patent Publication No. 2019-062441 [Patent Document 4] International Publication No. WO2014 / 054580 [Patent Document 5] International Publication No. WO2012 / 099083 [Patent Document 6] International Publication No. WO2009 / 090714 [Patent Document 7] International Publication No. WO2006 / 011417 [Patent Document 8] International Publication No. WO2010 / 058570 [Patent Document 9] International Publication No. WO2010 / 058544 [Patent Document 10] International Publication No. WO2007 / 080734 [Patent Document 11] Japanese Patent Publication No. 2013-066250 [Patent Document 12] Japanese Patent Publication No. 2013-214789 Summary of the Invention

[0005] An acoustic wave device according to one aspect of the present disclosure utilizes Lamb waves and includes a piezoelectric body and an electrode, wherein at least a portion of the electrode is embedded in the piezoelectric body.

[0006] An elastic wave device according to one embodiment of the present disclosure includes a piezoelectric body and an electrode, wherein a groove is formed in the piezoelectric body, and the electrode is an IDT electrode having electrode fingers, at least a portion of which is located inside the groove. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a cross-sectional view illustrating a schematic configuration of an elastic wave device according to a first embodiment of the present disclosure. [Figure 2] FIG. 10 is a cross-sectional view showing a schematic configuration of an elastic wave device according to a comparative embodiment of the present disclosure. [Figure 3] 1 is a table showing various configurations of embedded structure A and normal structure A. [Figure 4] 1 is a graph showing the relationship of Δf to θ for embedded structure A and normal structure A, and a table summarizing the median values ​​of θ and the maximum values ​​of Δf. [Figure 5] 10 is a graph showing the relationship between frequency and phase for embedded structure A and normal structure A. [Figure 6] Four types of graphs showing the relationship between frequency and impedance for embedded structure A are shown. [Figure 7] 10 is a graph showing the relationship of Δf to φ for the embedded structure A. [Figure 8] 10 is a graph showing the relationship of Δf to ψ for the embedded structure A. [Figure 9] Four types of graphs showing the relationship between frequency and impedance for embedded structure A are shown. [Figure 10]10 is a table showing various configurations of the embedded structure B and the normal structure B. [Figure 11] 10 is a graph showing the relationship of Δf to θ for embedded structure B and normal structure B, and a table summarizing the median values ​​of θ and the maximum values ​​of Δf. [Figure 12] 10 is a graph showing the relationship between frequency and phase for embedded structure B and normal structure B. [Figure 13] 10 is a graph showing the relationship of Δf to φ for embedded structure B. [Figure 14] 10 is a graph showing the relationship of Δf to ψ for embedded structure B. [Figure 15] 10 is a table summarizing the ranges and center values ​​of φ, θ, and ψ derived for each piezoelectric material. [Figure 16] 10 is a graph showing the relationship between frequency and phase for a membrane-embedded structure A and a normal membrane structure A. [Figure 17] 10 is a graph showing the relationship between frequency and phase for a membrane-embedded structure B and a membrane-normal structure B. [Figure 18] Formulas (1) to (6) are shown. [Figure 19] Three types of graphs related to equation (7) are shown below. [Figure 20] Formula (7) is shown. [Figure 21] Three types of graphs related to equation (8) described below are shown. [Figure 22] Formula (8) is shown. [Figure 23] Three types of structures of elastic wave devices are shown. [Figure 24] Four graphs showing the phase versus frequency relationship for three types of acoustic wave device structures are shown. [Figure 25] FIG. 2 is a cross-sectional view of a first simulation structure. [Figure 26] 10 is a table showing various configurations of the first simulation structure used in a simulation of the positional relationship between the upper surface of the electrode and the upper surface of the piezoelectric body. [Figure 27]FIG. 10 is a diagram illustrating the definition of a variable Y in a convex structure. [Figure 28] 1 shows a graph illustrating the phase versus frequency relationship of a convex structure in which the piezoelectric material is lithium niobate, along with cross-sectional views of the corresponding piezoelectric body and electrodes. [Figure 29] 10 is a graph showing the relationship between the value of Y and Δf for a convex structure in which the piezoelectric material is lithium niobate. [Figure 30] 10 is a graph showing the relationship between the value of Y and the resonance frequency fr for a convex structure in which the piezoelectric material is lithium niobate. [Figure 31] 1 shows a graph illustrating the phase versus frequency relationship of a convex structure in which the piezoelectric material is lithium tantalate, along with cross-sectional views of the corresponding piezoelectric body and electrodes. [Figure 32] 10 is a graph showing the relationship between the value of Y and Δf for a convex structure in which the piezoelectric material is lithium tantalate. [Figure 33] 10 is a graph showing the relationship between the value of Y and the resonance frequency fr for a convex structure in which the piezoelectric material is lithium tantalate. [Figure 34] FIG. 10 is a diagram illustrating the definition of a variable X in a concave structure. [Figure 35] 1 shows a graph of the phase versus frequency relationship for a recessed structure in which the piezoelectric material is lithium niobate, along with cross-sectional views of the corresponding piezoelectric body and electrodes. [Figure 36] 10 is a graph showing the relationship between the value of X and Δf for a concave structure in which the piezoelectric material is lithium niobate. [Figure 37] 10 is a graph showing the relationship between the value of X and the resonance frequency fr for a concave structure in which the piezoelectric material is lithium niobate. [Figure 38] 1 shows a graph of the phase versus frequency relationship for a recessed structure in which the piezoelectric material is lithium tantalate, along with cross-sectional views of the corresponding piezoelectric body and electrodes. [Figure 39] 10 is a graph showing the relationship between the value of X and Δf for a concave structure in which the piezoelectric material is lithium tantalate. [Figure 40]10 is a graph showing the relationship between the value of X and the resonance frequency fr for a concave structure in which the piezoelectric material is lithium tantalate. [Figure 41] FIG. 10 is a cross-sectional view of a second simulation structure. [Figure 42] 10 is a table showing various configurations of the second simulation structure used in the simulation of the electrode thickness. [Figure 43] FIG. 1 is a cross-sectional view of a piezoelectric body and an electrode for explaining the expression of the thickness of the electrode as a percentage of the thickness of the piezoelectric body. [Figure 44] 10 is a graph showing the relationship between Δf and the electrode thickness when the piezoelectric material is lithium tantalate. [Figure 45] 10 is a graph showing the relationship between Δf and the electrode thickness when the piezoelectric material is lithium niobate. [Figure 46] 10 is a graph showing the relationship between frequency and impedance when the piezoelectric material is lithium niobate. [Figure 47] 10 is a graph showing the relationship between frequency and phase when the piezoelectric material is lithium niobate. [Figure 48] 10 is another graph showing the relationship between frequency and phase when the piezoelectric material is lithium niobate. [Figure 49] 1 is a table summarizing useful electrode thickness configurations. [Figure 50] 10 is a graph showing the relationship between duty and Δf when the material of the piezoelectric body is lithium tantalate. [Figure 51] 10 is a graph showing the relationship between duty and Δf when the material of the piezoelectric body is lithium niobate. [Figure 52] This is a table summarizing useful configurations of Duty. [Figure 53] FIG. 10 is a cross-sectional view of a third simulation structure. [Figure 54] 10 is a table showing various configurations of the third simulation structure used in the simulation of the derived structure. [Figure 55]10 is a graph showing the relationship between frequency and phase when the piezoelectric material is lithium niobate. [Figure 56] 10 is a graph showing the relationship between frequency and phase when the material of the piezoelectric body is lithium tantalate. [Figure 57] FIG. 10 is a cross-sectional view of a fourth simulation structure. [Figure 58] 10 is a table showing various configurations of the fourth simulation structure used in the simulation of the derived structure. [Figure 59] 1A and 1B are cross-sectional views of back surface filling and full surface filling. [Figure 60] 10 is a graph showing the relationship between Δf and θ for a backside buried piezoelectric element in which the material of the piezoelectric body is lithium niobate. [Figure 61] 10 is a graph showing the relationship between Δf and θ for a backside buried piezoelectric device in which the material of the piezoelectric body is lithium tantalate. [Figure 62] 1 is a table summarizing useful configurations of θ in backside burying. [Figure 63] 10 is a graph showing the relationship between Δf and θ when the piezoelectric material is lithium niobate and is fully embedded. [Figure 64] 10 is a graph showing the relationship between Δf and θ when the piezoelectric material is lithium tantalate and is fully embedded. [Figure 65] 1 is a table summarizing useful configurations of θ in full embedding. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Embodiment 1] FIG. 1 is a cross-sectional view illustrating a schematic configuration of an elastic wave device 101 according to a first embodiment of the present disclosure.

[0009] Acoustic wave device 101 is an acoustic wave device that utilizes Lamb waves. Specifically, acoustic wave device 101 is an acoustic wave device that excites Lamb waves in piezoelectric body 1. Acoustic wave device 101 may utilize the A1 mode, which is an antisymmetric mode. Specifically, acoustic wave device 101 may excite the A1 mode in piezoelectric body 1.

[0010] A supplementary explanation of Lamb waves and A1 modes: Plate waves are classified into Lamb waves, whose vibration plane is perpendicular to the plate surface, and SH waves, whose vibration plane is parallel to the plate surface. Lamb waves are classified into S mode, which is a symmetric mode, and A mode, which is an antisymmetric mode. A1 mode is the first-order antisymmetric mode.

[0011] Acoustic wave device 101 includes a piezoelectric body 1, an electrode 2, a protective film 3, a multilayer film 4, and a support substrate 5. At least a portion of electrode 2 is embedded in piezoelectric body 1. Protective film 3 covers piezoelectric body 1 and electrode 2. Multilayer film 4 is disposed below piezoelectric body 1 and electrode 2.

[0012] The piezoelectric body 1 may be made of lithium tantalate or lithium niobate. Lithium tantalate may be represented as LiTaO3, hereinafter also referred to as LT. Lithium niobate may be represented as LiNbO3, hereinafter also referred to as LN. The piezoelectric body 1 has grooves formed therein for embedding the electrodes 2, and the electrodes 2 are formed in these grooves.

[0013] The electrode 2 may contain aluminum. The side surface of the electrode 2 is in contact with the piezoelectric body 1.

[0014] Electrode 2 may be a so-called IDT (interdigital transducer) electrode. One of the electrode fingers constituting the IDT electrode may be considered to be electrode finger 2f shown in FIG. 1. In acoustic wave device 101, the top surface of electrode 2 is flush with the top surface of piezoelectric body 1. The top surfaces of electrode 2 and piezoelectric body 1 do not have to be flush with each other. The top surface of electrode 2 may be convex or concave with respect to the top surface of piezoelectric body 1. Even in the case of a convex or concave top surface, the inventors of the present application have confirmed that the effect of reducing spurious emissions is achieved by embedding at least a portion of electrode 2.

[0015] Grooves 1g are formed in the piezoelectric body 1. When the electrode 2 is an IDT electrode and has electrode fingers 2f, at least a part of the electrode fingers 2f is located inside the grooves 1g.

[0016] The electrode 2 includes a single layer or a laminated structure of multiple layers. These multiple layers include a first layer 2a and a second layer 2b disposed on the first layer 2a. Alternatively, the electrode 2 may include a third layer or even more layers. The first layer 2a may be made of titanium. Various conductive materials are used for the first layer 2a to improve adhesion between the electrode 2 and the piezoelectric body 1. The second layer 2b may be made of aluminum.

[0017] The side surface of the uppermost layer of these multiple layers, i.e., the side surface of the second layer 2b, is in contact with the piezoelectric body 1. Alternatively, the side surface of the thickest layer of these multiple layers may be in contact with the piezoelectric body 1. The first layer 2a may cover the bottom and side surfaces of the second layer 2b. Another layer may be interposed between the side surface of the second layer 2b and the side surface of the piezoelectric body 1.

[0018] The piezoelectric body 1 does not need to be present on the bottom side of the electrode 2. The bottom surface of the electrode 2 may be in contact with the multilayer film 1. In other words, the first layer 2a may be in contact with the low acoustic impedance layer of the multilayer film 1. In the case of a membrane structure described later, the bottom surface of the electrode 2 may be exposed to the space.

[0019] The protective film 3 may be made of SiO2, or may be made of an insulating material that is generally used as a protective film.

[0020] The multilayer film 4 has a low acoustic impedance layer 4a and a high acoustic impedance layer 4b. The acoustic impedance of the low acoustic impedance layer 4a is lower than the acoustic impedance of the high acoustic impedance layer 4b.

[0021] The low acoustic impedance layer 4a and the high acoustic impedance layer 4b are stacked in this order from the support substrate 5 side: high acoustic impedance layer 4b, low acoustic impedance layer 4a. The multilayer film 4 has one or more of these stacked structures, and in FIG. 1, has four. The piezoelectric body 1 and the low acoustic impedance layer 4a are in contact with each other. A layer made of a high acoustic impedance material that is thin enough not to function as a high acoustic impedance layer may be interposed between the piezoelectric body 1 and the low acoustic impedance layer 4a. The low acoustic impedance layer 4a may contain SiO2. The high acoustic impedance layer 4b may contain at least one of HfO2, Ta2O5, and ZrO2.

[0022] Multilayer film 4 may be an acoustically reflective film. In this case, Lamb waves propagating from above acoustic wave device 101 are reflected at the interface between low acoustic impedance layer 4a and high acoustic impedance layer 4b.

[0023] The support substrate 5 is a substrate that supports from below the piezoelectric body 1, the electrode 2, the protective film 3, and the multilayer film 4. The support substrate 5 may be made of silicon, or various materials such as sapphire or glass may be used.

[0024] The piezoelectric body 1 is formed to be relatively thin. The thickness W of the piezoelectric body 1 may be 1.5 times or less the pitch of the electrodes 2 described below, or may be 0.3 times or more and 0.6 times or less.

[0025] 2 is a cross-sectional view showing a schematic configuration of an elastic wave device 101′ according to a comparative embodiment of the present disclosure. The schematic configuration of elastic wave device 101′ is the same as that of elastic wave device 101 except that electrode 2 is not embedded in piezoelectric body 1. That is, in elastic wave device 101′, no groove for embedding electrode 2 is formed in piezoelectric body 1, and electrode 2 is formed on the upper surface of plate-shaped piezoelectric body 1.

[0026] The first example of acoustic wave device 101 is referred to as "embedded structure A," and the first example of acoustic wave device 101' is referred to as "normal structure A."

[0027] Figure 3 is a table showing various configurations of buried structure A and normal structure A. The electrode 2 is an IDT electrode. The material of the protective film 3 is SiO2. The material of the second layer 2b is aluminum. The material of the first layer 2a is titanium. The material of the low acoustic impedance layer 4a is SiO2. The material of the high acoustic impedance layer 4b is HfO2.

[0028] The pitch of the electrode 2 is the pitch between the electrode finger 2f of the electrode 2 and another electrode finger (not shown) adjacent to the electrode finger 2f. The duty is the value obtained by dividing the width of the electrode finger 2f of the electrode 2 by the pitch of the electrode 2.

[0029] Fig. 4 is a graph showing the relationship between θ (unit: degrees) on the horizontal axis and Δf (unit: %fr) on the vertical axis for the embedded structure A and the normal structure A, as well as a table summarizing the median value of θ and the maximum value of Δf. The graph in Fig. 4 shows the relationship when φ=0° and ψ=0°.

[0030] The Euler angles of the piezoelectric body 1 are expressed as (φ, θ, ψ). φ is the φ in the Euler angles (φ, θ, ψ) of the piezoelectric body 1, θ is the θ in the Euler angles (φ, θ, ψ) of the piezoelectric body 1, and ψ is the ψ in the Euler angles (φ, θ, ψ) of the piezoelectric body 1.

[0031] Δf is the difference between the resonant frequency and the antiresonant frequency of the elastic wave device. The unit "%fr" indicates this difference expressed as a percentage of the resonant frequency of the elastic wave device.

[0032] The central value is the value at which the value of Δf is maximum.

[0033] 4, when θ is between 0° and 90° inclusive, Δf of the buried structure A generally exceeds 3.3%fr, which is the maximum value of Δf of the normal structure A. It can be seen that the buried structure A has a wider bandwidth than the normal structure A.

[0034] According to the characteristics of the embedding structure A, spurious signals 6 and 7 occur at θ=0° and θ=70°, respectively. It can be seen that in the embedding structure A, θ may be within the range of 1 to 69°.

[0035] Figure 5 is a graph showing the relationship between frequency (MHz) on the horizontal axis and phase (degrees) on the vertical axis for the embedded structure A and the normal structure A. Figure 5 shows the relationship when θ=31°.

[0036] In the graph of Figure 5, when comparing the characteristics of buried structure A with those of normal structure A, spurious signals 8 and 9 in particular are not present in the characteristics of buried structure A, but are present only in the characteristics of normal structure A. It can be seen that the buried structure A has reduced spurious signals compared to the normal structure A.

[0037] 6 shows four graphs showing the relationship between frequency (MHz) on the horizontal axis and impedance (ohms) on the vertical axis for the embedded structure A. The four graphs are as follows:

[0038] Upper left: Characteristics at θ=0° and θ=1° in the frequency range of 5000 to 5750 MHz Bottom left: Characteristics at θ=0° and θ=1° when the frequency range is 5100 to 5400 MHz Upper right: Characteristics at θ=69° and θ=70° when the frequency range is 5000 to 5750 MHz Bottom right: Characteristics at θ=69° and θ=70° when the frequency range is 5200 to 5500 MHz The minimum point of impedance is the resonant frequency fr. According to the lower left of Figure 6, when θ = 0°, the resonant frequency fr is represented by reference numeral 10, and spurious response 11 occurs. According to the lower left of Figure 6, when θ = 1°, the resonant frequency fr is represented by reference numeral 12, and spurious response 13 occurs. According to the lower right of Figure 6, when θ = 69°, the resonant frequency fr is represented by reference numeral 14, and spurious response 15 occurs. According to the lower right of Figure 6, when θ = 70°, the resonant frequency fr is represented by reference numeral 16, and spurious response 17 occurs.

[0039] The pass / fail criterion for the characteristics of the embedding structure A is that the spurious peak frequency is smaller than the resonance frequency fr. According to Fig. 6, the spurious peak frequency is smaller than the resonance frequency fr at θ=1° and θ=69°, while it is larger than the resonance frequency fr at θ=0° and θ=70°.

[0040] 7 is a graph showing the relationship between φ (unit: degrees) on the horizontal axis and Δf (unit: %fr) on the vertical axis for the embedded structure A. The graph in FIG. 7 shows the relationship when θ=31° and ψ=0°.

[0041] 7, when φ is greater than or equal to -23° and less than or equal to 23°, Δf of embedded structure A exceeds 3.3% fr, which is the maximum value of Δf of normal structure A. It can be seen that φ may be in the range of -23 to 23° in embedded structure A. According to FIG. 7, the median value of φ in embedded structure A is 0°.

[0042] 8 is a graph showing the relationship between ψ (unit: degrees) on the horizontal axis and Δf (unit: %fr) on the vertical axis for the embedded structure A. The graph in FIG. 8 shows the relationship when φ=0° and θ=31°.

[0043] 8, spurious signals 18 and 19 occur at points where ψ=-43° and ψ=43°, respectively. It can be seen that in buried structure A, ψ may be in the range of -42 to 42°. According to FIG. 8, the central value of ψ in buried structure A is 0°.

[0044] 9 shows four graphs showing the relationship between frequency (MHz) on the horizontal axis and impedance (ohms) on the vertical axis for the embedded structure A. The four graphs are as follows:

[0045] Upper left: Characteristics at ψ=-43° and ψ=-42° in the frequency range of 5000 to 5750 MHz Bottom left: Characteristics at ψ=-43° and ψ=-42° in the frequency range of 5100 to 5400 MHz Upper right: Characteristics at ψ=42° and ψ=43° in the frequency range of 5000 to 5750 MHz Bottom right: Characteristics at ψ=42° and ψ=43° when the frequency range is 5100 to 5400 MHz According to the lower left of Fig. 9, when ψ = -43°, the resonance frequency fr is represented by reference numeral 20, and a spurious response 21 occurs. According to the lower left of Fig. 9, when ψ = -42°, the resonance frequency fr is represented by reference numeral 22, and a spurious response 23 occurs. According to the lower right of Fig. 9, when ψ = 42°, the resonance frequency fr is represented by reference numeral 24, and a spurious response 25 occurs. According to the lower right of Fig. 9, when ψ = 43°, the resonance frequency fr is represented by reference numeral 26, and a spurious response 27 occurs.

[0046] The pass / fail criterion for the characteristics of the embedding structure A is that the spurious peak frequency is smaller than the resonance frequency fr. According to Fig. 9, the spurious peak frequency is smaller than the resonance frequency fr at ψ = -42° and ψ = 42°, while the spurious peak frequency is larger than the resonance frequency fr at ψ = -43° and ψ = 43°.

[0047] The second example of acoustic wave device 101 is referred to as "embedded structure B," and the second example of acoustic wave device 101' is referred to as "normal structure B."

[0048] FIG. 10 is a table showing various configurations of the buried structure B and the normal structure B. The electrode 2 is an IDT electrode. The material of the protective film 3 is SiO2. The material of the second layer 2b is aluminum. The material of the first layer 2a is titanium. The material of the low acoustic impedance layer 4a is SiO2. The material of the high acoustic impedance layer 4b is HfO2. The various definitions in FIG. 10 are the same as those in FIG. 3.

[0049] Fig. 11 is a graph showing the relationship between θ (unit: degrees) on the horizontal axis and Δf (unit: %fr) on the vertical axis for the embedded structure B and the normal structure B, as well as a table summarizing the median value of θ and the maximum value of Δf. The graph in Fig. 11 shows the relationship when φ=0° and ψ=0°.

[0050] 11, when θ is 1° or more and 78° or less in embedded structure B, Δf of embedded structure B generally exceeds 7.8%fr, which is the maximum value of Δf of normal structure B. It can be seen that embedded structure B has a wider bandwidth than normal structure B. It can also be seen that θ can be in the range of 1 to 78° in embedded structure B.

[0051] Fig. 12 is a graph showing the relationship between frequency (MHz) on the horizontal axis and phase (degrees) on the vertical axis for the buried structure B and the normal structure B. Fig. 12 shows the relationship when θ = 35°.

[0052] 12, when the characteristics of the buried structure B are compared with those of the normal structure B, spurious signals 28 to 30 are not present in the characteristics of the buried structure B, but are present only in the characteristics of the normal structure B. It can be seen that the buried structure B has reduced spurious signals compared to the normal structure B.

[0053] Fig. 13 is a graph showing the relationship between φ (unit: deg) on ​​the horizontal axis and Δf (unit: %fr) on the vertical axis for the embedded structure B. The graph in Fig. 13 shows the relationship when θ = 35° and ψ = 0°.

[0054] 13, when φ is equal to or larger than -17° and equal to or smaller than 17°, Δf of embedded structure B exceeds 7.8%fr, which is the maximum value of Δf of normal structure B. It can be seen that φ may be in the range of -17 to 17° in embedded structure B. According to FIG. 13, the median value of φ in embedded structure B is 0°.

[0055] Fig. 14 is a graph showing the relationship between ψ (unit: deg) on ​​the horizontal axis and Δf (unit: %fr) on the vertical axis for the embedded structure B. The graph in Fig. 14 shows the relationship when φ=0° and θ=35°.

[0056] 14, when ψ is equal to or larger than -21° and equal to or smaller than 21°, Δf of embedded structure B exceeds 7.8%fr, which is the maximum value of Δf of normal structure B. It can be seen that ψ may be in the range of -21 to 21° in embedded structure B. According to FIG. 14, the median value of ψ in embedded structure B is 0°.

[0057] Fig. 15 is a table summarizing the ranges and center values ​​of φ, θ, and ψ derived for each material of the piezoelectric body 1. According to Fig. 15, the following can be said.

[0058] In the embedding structure A, the piezoelectric body 1 is made of lithium tantalate. In the embedding structure A, when the Euler angles of the piezoelectric body 1 are (φ, θ, ψ), φ may be in the range of -23 to 23°, θ may be in the range of 1 to 69°, and ψ may be in the range of -42 to 42°.

[0059] In the embedding structure B, the piezoelectric body 1 is made of lithium niobate. In the embedding structure B, when the Euler angles of the piezoelectric body 1 are (φ, θ, ψ), φ may be in the range of -17 to 17°, θ may be in the range of 1 to 78°, and ψ may be in the range of -21 to 21°.

[0060] Each of acoustic wave devices 101 and 101′ may have a membrane structure instead of providing multilayer film 4. The membrane structure is a structure in which a recess is formed on supporting substrate 5 facing piezoelectric body 1, and piezoelectric body 1 is disposed to cover this recess.

[0061] The embedded structure A to which a membrane structure is applied is referred to as a "membrane embedded structure A," and the normal structure A to which a membrane structure is applied is referred to as a "membrane normal structure A."

[0062] Fig. 16 is a graph showing the relationship between frequency (unit: MHz) on the horizontal axis and phase (unit: degrees) on the vertical axis for membrane-embedded structure A and normal membrane structure A. The graph in Fig. 16 shows the relationship when φ = 0°, θ = 31°, and ψ = 0°. Fig. 16 shows that membrane-embedded structure A also has a spurious reduction effect similar to that of buried structure A.

[0063] The embedded structure B to which the membrane structure is applied is referred to as a "membrane embedded structure B," and the normal structure B to which the membrane structure is applied is referred to as a "membrane normal structure B."

[0064] Fig. 17 is a graph showing the relationship between frequency (unit: MHz) on the horizontal axis and phase (unit: degrees) on the vertical axis for membrane-embedded structure B and normal membrane structure B. The graph in Fig. 17 shows the relationship when φ = 0°, θ = 32°, and ψ = 0°. Fig. 17 shows that membrane-embedded structure B also has a spurious reduction effect similar to that of buried structure B.

[0065] Embedded structure A, embedded structure B, membrane embedded structure A, and membrane embedded structure B are collectively referred to as the "embedded structures." The vibration excited by the embedded structures is the antisymmetric A1 mode.

[0066] Figure 18 shows equations (1) to (6). The values ​​of b1, b2, b3, and b4 are variables. tPiezo is the thickness W (m) of piezoelectric body 1, and P is the pitch (m) of electrode 2, which are determined by the structure of the acoustic wave device. Equation (5) applies to LT, and equation (6) applies to LN.

[0067] 19 shows three types of graphs when the piezoelectric body 1 is LT. The three types of graphs are as follows:

[0068] Left: Dependence of B on the inverse of the pitch of electrode 2 in m Middle: Dependence of the slope of B on the thickness W of the piezoelectric body 1 in m units Right: Dependence of the intercept of B on the thickness W of the piezoelectric body 1 in m 19, it can be seen that in equation (4), B has a linear dependency on the inverse of the pitch of the electrodes 2, and that the slope and intercept of B each have a linear dependency on the thickness W of the piezoelectric body 1.

[0069] Figure 20 shows Equation (7). Equation (7) is fitted to match the resonance frequency obtained from FEM, assuming that the piezoelectric body 1 is made of LT. When the piezoelectric body 1 is made of LT, A = 5600 m / s (meters per second), b1 = -1015 m / s, and b2 = 2.201 x 10 -4 m 2 / s, b3=2.345×10 9 / s, b4=3001m / s.

[0070] 21 shows three types of graphs when the piezoelectric body 1 is made of LN. The three types of graphs are as follows:

[0071] Left: Dependence of B on the inverse of the pitch of electrode 2 in m Middle: Dependence of the slope of B on the thickness W of the piezoelectric body 1 in m units Right: Dependence of the intercept of B on the thickness W of the piezoelectric body 1 in m 21, it can be seen that in equation (4), B has a linear dependency on the inverse of the pitch of the electrodes 2, and that the slope and intercept of B each have a linear dependency on the thickness W of the piezoelectric body 1.

[0072] Figure 22 shows Equation (8). Equation (8) is fitted to match the resonance frequency obtained from FEM, assuming that the piezoelectric body 1 is made of LN. When the piezoelectric body 1 is made of LN, A = 6550 m / s, b1 = -950 m / s, and b2 = 3.979 x 10 -4 m 2 / s, b3=3.456×10 9 / s, b4=2340m / s.

[0073] In acoustic wave device 101, frequency f obtained by formulas (1) to (8) may be 3 GHz or higher.

[0074] 23 shows three types of structures of the acoustic wave device. The three types of structures are structures 201 to 203, respectively.

[0075] The structure 201 includes a piezoelectric body 1 and an electrode 2 , and at least a portion of the electrode 2 is embedded in the piezoelectric body 1 .

[0076] The structure 202 includes a piezoelectric body 1, an electrode 2, and a non-piezoelectric LT film 31. In the structure 202, the electrode 2 is not embedded in the piezoelectric body 1. In the structure 202, the electrode 2 and the LT film 31 are formed on the upper surface of the plate-shaped piezoelectric body 1. In the structure 202, the electrode 2 is embedded in the LT film 31.

[0077] The structure 203 includes a piezoelectric body 1, an electrode 2, and a film 32. The film 32 is made of SiO2. In the structure 203, the electrode 2 is not embedded in the piezoelectric body 1. In the structure 203, the electrode 2 and the film 32 are formed on the upper surface of the plate-shaped piezoelectric body 1. In the structure 203, the electrode 2 is embedded in the film 32.

[0078] Each of the structures 201 to 203 utilizes Lamb waves in an antisymmetric mode such as the A1 mode. The following conditions are determined for each of the structures 201 to 203. The material of the piezoelectric body 1 is LT. The thickness of the piezoelectric body 1 is 400 nm. The Euler angles of the piezoelectric body 1 are φ=0° and ψ=0°. The material of the first layer 2a is titanium. The thickness of the first layer 2a is 6 nm. The material of the second layer 2b is aluminum. The thickness of the second layer 2b is 124 nm.

[0079] Fig. 24 shows four types of graphs illustrating the relationship between frequency (unit: MHz) on the horizontal axis and phase (unit: degrees) on the vertical axis for structures 201 to 203. In each graph in Fig. 24, the dotted line indicates the characteristics of structure 201, the dashed line indicates the characteristics of structure 202, and the solid line indicates the characteristics of structure 203.

[0080] 24, in structure 201, Δf can be made larger than in structures 202 and 203. It can be seen that a configuration in which at least a portion of electrode 2 is embedded in piezoelectric body 1 is effective. In structure 203, the loss is also increased because of the absence of the so-called Z-ratio.

[0081] [Embodiment 2] The upper end of electrode 2 may include a peak portion, which is the highest point of electrode 2 when the acoustic wave device is in an upright position, and a semi-peak portion, which is lower than the peak portion. This means that the height of the upper end of electrode 2 may be uneven. Examples of cross-sectional shapes of the upper end of electrode 2 include a mountain shape (convex shape), a recessed shape (concave shape), an M shape which is a combination of a convex shape and a concave shape, and a W shape which is a combination of a convex shape and a concave shape.

[0082] The upper end of the electrode 2 may be rounded, and a smooth line may connect the upper end of the electrode 2 to the upper end of the piezoelectric body 1. Examples of a smooth line include a single straight line, a single curved line, a line connecting two straight lines and two curved lines, and a line connecting two curved lines.

[0083] The first layer 2a may be in contact with the side surface of the second layer 2b. A typical example is a configuration in which the first layer 2a covers at least a part of the side surface of the second layer 2b.

[0084] Acoustic wave device 101 may include an underlying layer of electrode 2 that includes a dielectric.

[0085] [Embodiment 3] A communication device including the acoustic wave device 101 is also included in the scope of the present disclosure. The communication device may perform wireless communication using radio waves. In the communication device, the acoustic wave device 101 may be used, for example, as a filter in a duplexer.

[0086] [Embodiment 4] A simulation using a simulation structure simulating the elastic wave device 101 was performed to explore an advantageous configuration of the elastic wave device 101. The simulation items were the positional relationship between the upper surface of the electrode 2 and the upper surface of the piezoelectric body 1, the thickness of the electrode 2, the duty, and the derived structure. The advantageous configuration of the elastic wave device 101 can be considered to be essentially the same as the advantageous configuration of the simulation structure.

[0087] (Positional relationship between the top surface of the electrode 2 and the top surface of the piezoelectric body 1) 25 is a cross-sectional view of a first simulation structure 102. The first simulation structure 102 differs from the acoustic wave device 101 in that it does not include a protective film 3 and that the multilayer film 4 includes a mixed layer 33. The mixed layer 33 is formed below the low acoustic impedance layer 4a and below the high acoustic impedance layer 4b, and is a layer that contains both the material of the low acoustic impedance layer 4a and the material of the high acoustic impedance layer 4b. The presence or absence of the mixed layer 33 does not significantly change the essential characteristics of the acoustic wave device 101.

[0088] FIG. 26 is a table showing various configurations of the first simulation structure 102 used in a simulation of the positional relationship between the upper surface of the electrode 2 and the upper surface of the piezoelectric body 1. FIG. 26 shows the case where the material of the piezoelectric body 1 is LT and the case where the material of the piezoelectric body 1 is LN. In the first simulation structure 102, the electrode 2 is made of the same material as the second layer 2b. The numerical values ​​shown in FIG. 26 are basic values ​​and can be changed as appropriate when performing the simulation.

[0089] A configuration in which at least a portion of the electrode 2 is embedded in the piezoelectric body 1 can be classified into a convex structure in which the upper surface of the electrode 2 protrudes from the upper surface of the piezoelectric body 1, and a concave structure in which the upper surface of the electrode 2 is recessed from the upper surface of the piezoelectric body 1.

[0090] 27 is a diagram illustrating the definition of the variable Y in a convex structure. The variable Y is expressed as 100×s / r, where r is the thickness of electrode 2 and s is the distance between the upper end of electrode 2 and the upper end of piezoelectric body 1 in the thickness direction of piezoelectric body 1. Y=0 occurs when the upper surface of electrode 2 is flush with the upper surface of piezoelectric body 1. Y=100 occurs when electrode 2 is not embedded in piezoelectric body 1, as in acoustic wave device 101′.

[0091] Fig. 28 shows a graph illustrating the relationship between frequency and phase for a convex structure in which the material of the piezoelectric body 1 is LN, along with cross-sectional views of the corresponding piezoelectric body 1 and electrode 2. Fig. 28 shows graphs for Y = 0, Y = approximately 50 (5 / 0.11), and Y = 100. Fig. 28 shows that the smaller Y is, the more spurious is reduced.

[0092] Fig. 29 is a graph showing the relationship between the value of Y (unitless) on the horizontal axis and Δf (units: %fr) on the vertical axis for a convex structure in which the material of the piezoelectric body 1 is LN. Fig. 30 is a graph showing the relationship between the value of Y (unitless) on the horizontal axis and the resonance frequency fr (units: MHz) on the vertical axis for a convex structure in which the material of the piezoelectric body 1 is LN.

[0093] 29, it can be seen that the smaller Y is, the larger Δf is. According to Fig. 30, when Y exceeds approximately 50, fr becomes smaller, indicating a tendency for the sound speed to decrease.

[0094] Fig. 31 shows a graph illustrating the relationship between frequency and phase for a convex structure in which the material of the piezoelectric body 1 is LT, along with cross-sectional views of the corresponding piezoelectric body 1 and electrode 2. Fig. 31 shows graphs for Y = 0, Y = 50, and Y = 100. Fig. 31 shows that the smaller Y is, the more spurious is reduced.

[0095] Fig. 32 is a graph showing the relationship between the value of Y (unitless) on the horizontal axis and Δf (units: % fr) on the vertical axis for a convex structure in which the material of the piezoelectric body 1 is LT. Fig. 33 is a graph showing the relationship between the value of Y (unitless) on the horizontal axis and the resonance frequency fr (units: MHz) on the vertical axis for a convex structure in which the material of the piezoelectric body 1 is LT.

[0096] According to Fig. 32, it can be seen that the smaller Y is, the larger Δf is. According to Fig. 33, when Y is below about 25 or exceeds 75, fr becomes smaller, indicating a tendency for the sound speed to decrease.

[0097] 34 is a diagram illustrating the definition of the variable X in a concave structure. The variable X is expressed as 100×c / (ba), where a is the thickness of the electrode 2, b is the thickness of the piezoelectric body 1, and c is the distance between the top end of the electrode 2 and the top end of the piezoelectric body 1 in the thickness direction of the piezoelectric body 1. X=0 is when the top surface of the electrode 2 and the top surface of the piezoelectric body 1 are flush with each other. X=100 is when the bottom surface of the electrode 2 and the bottom surface of the piezoelectric body 1 are flush with each other.

[0098] Fig. 35 shows a graph illustrating the relationship between frequency and phase for a concave structure in which the material of the piezoelectric body 1 is LN, along with cross-sectional views of the corresponding piezoelectric body 1 and electrode 2. Fig. 35 shows graphs for the cases of X=0, X=69, and X=99.6. Fig. 35 shows that the smaller X is, the more spurious is reduced.

[0099] Fig. 36 is a graph showing the relationship between the value of X (unitless) on the horizontal axis and Δf (units: %fr) on the vertical axis for a concave structure whose piezoelectric body 1 is made of LN. Fig. 37 is a graph showing the relationship between the value of X (unitless) on the horizontal axis and the resonance frequency fr (units: MHz) on the vertical axis for a concave structure whose piezoelectric body 1 is made of LN.

[0100] FIG. 36 shows that when X exceeds approximately 25, the larger X, the smaller Δf becomes. Dotted line 34 in FIG. 36 indicates Δf when Y=100 for a convex structure in which the piezoelectric body 1 is made of LN. When we checked the condition for X where Δf falls above dotted line 34, we found that X≦69. In other words, when the piezoelectric body 1 is made of LN in a concave structure, 100×c / (ba)≦69 may be satisfied. FIG. 37 shows that when X exceeds approximately 50, fr becomes smaller, indicating a tendency toward a lower sound velocity.

[0101] Fig. 38 shows a graph illustrating the relationship between frequency and phase for a concave structure in which the material of the piezoelectric body 1 is LT, along with cross-sectional views of the corresponding piezoelectric body 1 and electrode 2. Fig. 38 shows graphs for the cases of X=0, X=36, and X=99.6. Fig. 38 shows that the smaller X is, the more spurious is reduced.

[0102] Fig. 39 is a graph showing the relationship between the value of X (unitless) on the horizontal axis and Δf (units: %fr) on the vertical axis for a concave structure in which the material of the piezoelectric body 1 is LT. Fig. 40 is a graph showing the relationship between the value of X (unitless) on the horizontal axis and the resonance frequency fr (units: MHz) on the vertical axis for a concave structure in which the material of the piezoelectric body 1 is LT.

[0103] According to FIG. 39, when X exceeds approximately 20, the larger X, the smaller Δf becomes. Dotted line 35 in FIG. 39 indicates Δf when Y=100 for a convex structure in which the material of piezoelectric body 1 is LT. When the condition for X where Δf falls above dotted line 35 was checked, it was found that X≦36. In other words, when the piezoelectric body 1 is made of LT in a concave structure, 100×c / (ba)≦36 may be satisfied. According to FIG. 40, roughly speaking, the larger X, the smaller fr becomes, indicating a tendency for the sound velocity to decrease.

[0104] (Thickness of electrode 2) 41 is a cross-sectional view of the second simulation structure 103. The second simulation structure 103 differs from the acoustic wave device 101 in that it does not include the protective film 3.

[0105] FIG. 42 is a table showing various configurations of the second simulation structure 103 used in a simulation of the thickness of the electrode 2. FIG. 42 shows the case where the material of the piezoelectric body 1 is LT and the case where the material of the piezoelectric body 1 is LN. In the second simulation structure 103, the electrode 2 is made of the same material as the second layer 2b. The numerical values ​​shown in FIG. 42 are basic values ​​and can be changed as appropriate when performing the simulation.

[0106] The thickness of the electrode 2 may be expressed either as a dimension in units of nm or as a percentage of the thickness of the piezoelectric body 1 in units of %tPiezo.

[0107] FIG. 43 is a cross-sectional view of the piezoelectric body 1 and the electrode 2 for explaining the expression of the thickness of the electrode 2 as a percentage of the thickness of the piezoelectric body 1. When the thickness of the electrode 2 is 100% tPiezo or less, the top surface of the electrode 2 is flush with the top surface of the piezoelectric body 1. When the thickness of the electrode 2 is 100% tPiezo, the bottom surface of the electrode 2 is flush with the bottom surface of the piezoelectric body 1. When the thickness of the electrode 2 exceeds 100% tPiezo, the bottom surface of the electrode 2 protrudes from the bottom surface of the piezoelectric body 1. The bottom surface of the electrode 2 is located, for example, inside the low acoustic impedance layer 4a located closest to the piezoelectric body 1.

[0108] Fig. 44 is a graph showing the relationship between the thickness of electrode 2, shown on the horizontal axis in %tPiezo, and Δf, shown on the vertical axis in %fr, when the material of piezoelectric body 1 is LT. Fig. 45 is a graph showing the relationship between the thickness of electrode 2, shown on the horizontal axis in %tPiezo, and Δf, shown on the vertical axis in %fr, when the material of piezoelectric body 1 is LN.

[0109] When the material of the piezoelectric body 1 is LT, the thickness of the electrode 2 under which Δf falls above the dotted line 35 was checked and found to be 161% tPiezo or less. When the material of the piezoelectric body 1 is LN, the thickness of the electrode 2 under which Δf falls above the dotted line 34 was checked and found to be approximately 160% tPiezo or less. However, when the material of the piezoelectric body 1 is LN, spurious responses increased when the thickness of the electrode 2 was 127% tPiezo or more.

[0110] Fig. 46 is a graph showing the relationship between frequency (MHz) on the horizontal axis and impedance (ohms) on the vertical axis when the material of the piezoelectric body 1 is LN. Fig. 47 is a graph showing the relationship between frequency (MHz) on the horizontal axis and phase (degrees) on the vertical axis when the material of the piezoelectric body 1 is LN. Fig. 48 is another graph showing the relationship between frequency (MHz) on the horizontal axis and phase (degrees) on the vertical axis when the material of the piezoelectric body 1 is LN.

[0111] 46 to 48 respectively show the characteristics when the thickness of electrode 2 is 124% tPiezo and the characteristics when the thickness of electrode 2 is 127% tPiezo. Note the depth of the valley in the graph located near 5850 MHz shown in FIG. 48. If the depth is less than 1 degree, it is considered good, and if the depth is 1 degree or more, it is considered bad because it can be considered that this may have an adverse effect on spurious reduction. If the thickness of electrode 2 is 124% tPiezo, it is good, and if the thickness of electrode 2 is 127% tPiezo, it is bad.

[0112] In addition, the thickness of the electrode 2 is generally 20 nm or more.

[0113] FIG. 49 is a table summarizing useful configurations for the thickness of electrode 2. The thickness of electrode 2 may be within range 1 of FIG. 49 or within range 2 of FIG. 49. When piezoelectric body 1 is made of LT, the thickness of electrode 2 may be 0.2% or more and 161% or less of the thickness of piezoelectric body 1, or may be 20 nm or more and 161% or less of the thickness of piezoelectric body 1. When piezoelectric body 1 is made of LN, the thickness of electrode 2 may be 3% or more and 124% or less of the thickness of piezoelectric body 1, or may be 20 nm or more and 124% or less of the thickness of piezoelectric body 1.

[0114] (Duty) Fig. 50 is a graph showing the relationship between duty (unitless) shown on the horizontal axis and Δf (unitless) shown on the vertical axis when the material of the piezoelectric body 1 is LT. Fig. 51 is a graph showing the relationship between duty (unitless) shown on the horizontal axis and Δf (unitless) shown on the vertical axis when the material of the piezoelectric body 1 is LN.

[0115] When the material of the piezoelectric body 1 is LT, the duty conditions for which Δf falls above dotted line 35 were checked and found to be 0.76 or less. When the material of the piezoelectric body 1 is LN, the duty conditions for which Δf falls above dotted line 34 were checked and found to be 0.74 or less. In addition, the width of the electrode fingers 2f of the electrode 2 is generally 0.3 μm or more.

[0116] FIG. 52 is a table summarizing useful configurations of the duty. The duty may be within range 1 in FIG. 52. The duty and the width of the electrode fingers 2f of the electrode 2 may be within range 2 in FIG. 52. When the piezoelectric body 1 is made of LT, the duty may be 0.01 or more and 0.76 or less. When the piezoelectric body 1 is made of LT, the width of the electrode fingers 2f of the electrode 2 may be 0.3 μm or more, and the duty may be 0.76 or less. When the piezoelectric body 1 is made of LN, the duty may be 0.01 or more and 0.74 or less. When the piezoelectric body 1 is made of LN, the width of the electrode fingers 2f of the electrode 2 may be 0.3 μm or more, and the duty may be 0.74 or less.

[0117] (derived structure) 53 is a cross-sectional view of the third simulation structure 104. The third simulation structure 104 differs from the first simulation structure 102 in that the electrode 2 includes a first layer 2a and a second layer 2b. In the third simulation structure 104, the second layer 2b is disposed on the first layer 2a, and the first layer 2a contacts the side surface of the second layer 2b.

[0118] Fig. 54 is a table showing various configurations of the third simulation structure 104 used in the simulation of the derived structure. Fig. 54 shows the case where the material of the piezoelectric body 1 is LT and the case where the material of the piezoelectric body 1 is LN. The numerical values ​​shown in Fig. 54 are basic values ​​and can be changed as appropriate when performing the simulation.

[0119] Fig. 55 is a graph showing the relationship between frequency (MHz) on the horizontal axis and phase (degrees) on the vertical axis when the material of the piezoelectric body 1 is LN. Fig. 56 is a graph showing the relationship between frequency (MHz) on the horizontal axis and phase (degrees) on the vertical axis when the material of the piezoelectric body 1 is LT.

[0120] 55 and 56 respectively show the characteristics of the first simulation structure 102 and the characteristics of the third simulation structure 104. There is no significant difference between the characteristics of the first simulation structure 102 and the characteristics of the third simulation structure 104.

[0121] 57 is a cross-sectional view of the fourth simulation structure 105. The fourth simulation structure 105 differs from the first simulation structure 102 in that it is back-surface buried or full-surface buried, as will be described later. Since the arrangement of the electrode 2 differs between back-surface buried and full-surface buried, the electrode 2 is not shown in FIG.

[0122] FIG. 58 is a table showing various configurations of the fourth simulation structure 105 used in the simulation of the derived structure. FIG. 58 shows the case where the material of the piezoelectric body 1 is LT and the case where the material of the piezoelectric body 1 is LN. In the fourth simulation structure 105, the electrode 2 is made of the same material as the second layer 2b. The numerical values ​​listed in FIG. 58 are basic values ​​and can be changed as appropriate when performing the simulation.

[0123] 59 is a cross-sectional view of back-surface embedding and full-surface embedding. Back-surface embedding is a structure in which at least a portion of the electrode 2 is embedded in the piezoelectric body 1 so that the bottom surface of the electrode 2 is not in contact with the piezoelectric body 1 and all surfaces of the electrode 2 other than the bottom surface are in contact with the piezoelectric body 1. Full-surface embedding is a structure in which at least a portion of the electrode 2 is embedded in the piezoelectric body 1 so that the entire surface of the electrode 2 is in contact with the piezoelectric body 1.

[0124] Fig. 60 is a graph showing the relationship between θ (in degrees) on the horizontal axis and Δf (in % fr) on the vertical axis for backside embedding where the material of the piezoelectric body 1 is LN. Fig. 61 is a graph showing the relationship between θ (in degrees) on the horizontal axis and Δf (in % fr) on the vertical axis for backside embedding where the material of the piezoelectric body 1 is LT. In backside embedding and full surface embedding, φ=0° and ψ=0° are assumed.

[0125] When the piezoelectric body 1 is made of LN and is mounted on the backside, the conditions for θ where Δf falls above dotted line 34 were checked and found to be 10° or more and 50° or less. When the piezoelectric body 1 is made of LT and is mounted on the backside, the conditions for θ where Δf falls stably above dotted line 35 were checked and found to be 5° or more and 59° or less.

[0126] 62 is a table summarizing useful configurations of θ in backside embedding. When the piezoelectric body 1 is made of LT in backside embedding, and its Euler angles are (0°, θ, 0°), θ may be in the range of 5 to 59°. When the piezoelectric body 1 is made of LN in backside embedding, and its Euler angles are (0°, θ, 0°), θ may be in the range of 10 to 50°.

[0127] Furthermore, to ensure that Δf is a sufficiently large value, θ may be within a range of 10° or less from the center value. In backside embedding where the material of the piezoelectric body 1 is LT, θ may be within a range of 23 to 43°. In backside embedding where the material of the piezoelectric body 1 is LN, θ may be within a range of 19 to 39°.

[0128] Fig. 63 is a graph showing the relationship between θ on the horizontal axis in degrees and Δf on the vertical axis in % fr for a full-surface embedding of piezoelectric body 1 made of LN. Fig. 64 is a graph showing the relationship between θ on the horizontal axis in degrees and Δf on the vertical axis in % fr for a full-surface embedding of piezoelectric body 1 made of LT.

[0129] When the piezoelectric body 1 is fully embedded and the material is LN, the conditions for θ where Δf falls above dotted line 34 were checked, and it was found to be 1° or more and 64° or less. When the piezoelectric body 1 is fully embedded and the material is LT, the conditions for θ where Δf stably falls above dotted line 35 were checked, and it was found to be 5° or more and 67° or less.

[0130] Figure 65 is a table summarizing useful configurations of θ in full-surface embedding. When the piezoelectric body 1 is made of LT and its Euler angles are (0°, θ, 0°), θ may be in the range of 5 to 67°. When the piezoelectric body 1 is made of LN and its Euler angles are (0°, θ, 0°), θ may be in the range of 1 to 64°.

[0131] Furthermore, to ensure that Δf is a sufficiently large value, θ may be within a range of 10° or less from the center value. In the case of full-surface embedding in which the material of the piezoelectric body 1 is LT, θ may be within a range of 19 to 39°. In the case of full-surface embedding in which the material of the piezoelectric body 1 is LN, θ may be within a range of 19 to 39°.

[0132] [Summary] The acoustic wave device according to the present disclosure includes a piezoelectric body 1 and an electrode 2, and can be interpreted as utilizing Lamb waves, with at least a portion of the electrode 2 being embedded in the piezoelectric body 1.

[0133] On the other hand, the elastic wave device according to the present disclosure comprises a piezoelectric body 1 and an electrode 2, in which a groove 1g is formed in the piezoelectric body 1, and the electrode 2 is an IDT electrode having electrode fingers 2f, at least a portion of which is located inside the groove 1g.

[0134] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure. [Explanation of symbols]

[0135] 1. Piezoelectric 1g groove 2 electrodes 2a 1st layer 2b 2nd layer 2f electrode finger 3 Protective film 4 Multilayer film 4a Low acoustic impedance layer 4b High acoustic impedance layer 5 Support substrate 101 Elastic Wave Device

Claims

1. The piezoelectric element includes a piezoelectric body and an electrode. an elastic wave device utilizing Lamb waves, wherein at least a portion of the electrode is embedded in the piezoelectric body, The piezoelectric body is It is made of lithium tantalate, In the elastic wave device, where the Euler angles are (φ, θ, ψ), φ is in the range of -23 to 23°, θ is in the range of 1 to 69°, and ψ is in the range of -42 to 42°.

2. A piezoelectric element comprising a piezoelectric body and an electrode, an elastic wave device utilizing Lamb waves, wherein at least a portion of the electrode is embedded in the piezoelectric body, The piezoelectric body is It is made of lithium niobate, In the elastic wave device, where the Euler angles are (φ, θ, ψ), φ is in the range of −17 to 17°, θ is in the range of 1 to 78°, and ψ is in the range of −21 to 21°.

3. A piezoelectric element comprising a piezoelectric body and an electrode, A groove is formed in the piezoelectric body, the electrode is an IDT electrode and has electrode fingers; an elastic wave device utilizing Lamb waves, wherein at least a portion of the electrode fingers is located inside the groove; The piezoelectric body is It is made of lithium tantalate, In the elastic wave device, where the Euler angles are (φ, θ, ψ), φ is in the range of -23 to 23°, θ is in the range of 1 to 69°, and ψ is in the range of -42 to 42°.

4. A piezoelectric element comprising a piezoelectric body and an electrode, A groove is formed in the piezoelectric body, the electrode is an IDT electrode and has electrode fingers; an elastic wave device utilizing Lamb waves, wherein at least a portion of the electrode fingers is located inside the groove; The piezoelectric body is It is made of lithium niobate, In the elastic wave device, where the Euler angles are (φ, θ, ψ), φ is in the range of −17 to 17°, θ is in the range of 1 to 78°, and ψ is in the range of −21 to 21°.

5. Antisymmetric mode A １ The acoustic wave device according to claim 1 , wherein the acoustic wave device utilizes a mode.

6. The piezoelectric body is When the material is lithium tantalate, the frequency f obtained by the formulas (1) to (5) is 3 GHz or more, 5. The acoustic wave device according to claim 1, wherein when the material is lithium niobate, the frequency f obtained by formulas (1) to (4) and (6) is 3 GHz or higher. [Equation 1] [Equation 2] [Equation 3] [Equation 4] [Equation 5] [Equation 6] tPiezo: Thickness of the piezoelectric body, in m P: the pitch of the electrodes, in m When the piezoelectric body is made of lithium tantalate, b １ =-1015m / s b ２ =2.201×10 －４ m ２ / s b ３ =2.345×10 ９ / s b ４ =3001m / s When the piezoelectric body is made of lithium niobate, b １ =-950m / s b ２ =3.979×10 －４ m ２ / s b ３ =3.456×10 ９ / s b ４ =2340m / s

7. The acoustic wave device according to claim 1 , wherein the electrodes contain aluminum.

8. The acoustic wave device according to claim 1 , wherein an upper surface of the electrode and an upper surface of the piezoelectric element are flush with each other.

9. 5. The elastic wave device according to claim 1, wherein the upper end of the electrode includes a highest portion that is the highest position of the electrode when the elastic wave device is in an upright state, and a semi-high portion that is lower than the highest portion.

10. The upper end of the electrode is rounded, The acoustic wave device according to claim 9 , wherein the upper end of the electrode and the upper end of the piezoelectric element can be connected by a smooth line.

11. The acoustic wave device according to claim 1 , wherein a side surface of the electrode is in contact with the piezoelectric element.

12. The acoustic wave device according to claim 1 , wherein the electrode includes a laminated structure of a plurality of layers.

13. The acoustic wave device according to claim 12 , wherein a side surface of an uppermost layer of the plurality of layers is in contact with the piezoelectric body.

14. the plurality of layers includes a first layer and a second layer disposed on the first layer; The acoustic wave device according to claim 12 , wherein the first layer is in contact with a side surface of the second layer.

15. The acoustic wave device according to claim 1 , further comprising a protective film that covers the piezoelectric body and the electrode.

16. The acoustic wave device according to claim 1 , further comprising a multilayer film disposed below the piezoelectric body and the electrode.

17. The multilayer film is SiO ２ a low acoustic impedance layer comprising: HfO ２ , Ta ２ O ５ , and ZrO ２ and a high acoustic impedance layer including at least one of the following:

18. The acoustic wave device according to claim 1 , which has a membrane structure.

19. The acoustic wave device according to claim 1 , wherein the thickness of the piezoelectric body is 1.5 times or less the pitch of the electrodes.

20. The acoustic wave device according to claim 1 , wherein an upper surface of the electrode protrudes beyond an upper surface of the piezoelectric element.

21. The acoustic wave device according to claim 1 , wherein an upper surface of the electrode is recessed with respect to an upper surface of the piezoelectric element.

22. the piezoelectric body is made of lithium tantalate, The thickness of the electrode is defined as a, the thickness of the piezoelectric body is defined as b, and the distance between the upper end of the electrode and the upper end of the piezoelectric body along the thickness direction of the piezoelectric body is defined as c, 100×c / (ba)≦36 The acoustic wave device according to claim 21 , wherein

23. the piezoelectric body is made of lithium niobate, The thickness of the electrode is defined as a, the thickness of the piezoelectric body is defined as b, and the distance between the upper end of the electrode and the upper end of the piezoelectric body along the thickness direction of the piezoelectric body is defined as c, 100×c / (ba)≦69 The acoustic wave device according to claim 21 , wherein

24. An elastic wave device as described in claim 1 or 3, wherein the thickness of the electrode is 0.2% or more of the thickness of the piezoelectric body and 161% or less of the thickness of the piezoelectric body.

25. An elastic wave device as described in claim 1 or 3, wherein the thickness of the electrode is 20 nm or more and 161% or less of the thickness of the piezoelectric body.

26. An elastic wave device as described in claim 2 or 4, wherein the thickness of the electrode is 3% or more of the thickness of the piezoelectric body and 124% or less of the thickness of the piezoelectric body.

27. ​​An elastic wave device as described in claim 2 or 4, wherein the thickness of the electrode is 20 nm or more and 124% or less of the thickness of the piezoelectric body.

28. An elastic wave device as described in claim 1 or 3, wherein Duty is 0.01 or more and 0.76 or less.

29. The width of the electrode fingers of the electrode is 0.3 μm or more, The acoustic wave device according to claim 1 , wherein a duty is equal to or less than 0.

76.

30. The width of the electrode fingers is 0.3 μm or more, The acoustic wave device according to claim 3 , wherein a duty is equal to or less than 0.

76.

31. An elastic wave device as described in claim 2 or 4, wherein Duty is 0.01 or more and 0.74 or less.

32. The width of the electrode fingers of the electrode is 0.3 μm or more, The acoustic wave device according to claim 2 , wherein a duty is equal to or less than 0.

74.

33. The width of the electrode fingers is 0.3 μm or more, The acoustic wave device according to claim 4 , wherein a duty is equal to or less than 0.

74.

34. The acoustic wave device according to claim 1 , wherein a bottom surface of the electrode is not in contact with the piezoelectric body, and all surfaces of the electrode other than the bottom surface are in contact with the piezoelectric body.

35. The piezoelectric body is It is made of lithium tantalate, The elastic wave device according to claim 34, wherein θ is in the range of 5 to 59°, where the Euler angles are (0°, θ, 0°).

36. The acoustic wave device according to claim 35, wherein θ is in the range of 23 to 43 degrees.

37. The piezoelectric body is It is made of lithium niobate, The elastic wave device according to claim 34, wherein θ is in the range of 10 to 50°, where the Euler angles are (0°, θ, 0°).

38. The acoustic wave device according to claim 37, wherein θ is in the range of 19 to 39 degrees.

39. The acoustic wave device according to claim 1 , wherein the entire surface of the electrode is in contact with the piezoelectric element.

40. The piezoelectric body is It is made of lithium tantalate, The elastic wave device of claim 39, wherein θ is in the range of 5 to 67°, where the Euler angles are (0°, θ, 0°).

41. The piezoelectric body is It is made of lithium niobate, The elastic wave device of claim 39, wherein θ is in the range of 1 to 64°, where the Euler angles are (0°, θ, 0°).

42. The acoustic wave device according to claim 40, wherein θ is in the range of 19 to 39 degrees.

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

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