Piezoelectric device

Abstract

According to the present invention, unwanted waves are suppressed. This piezoelectric device comprises: a piezoelectric stacked body layer that has a thickness in a first direction and has an upper surface and a lower surface; a supporting member that is provided on the lower surface side of the piezoelectric stacked body; an upper electrode that is provided on the upper surface side of the piezoelectric stacked body; and a lower electrode that is provided on the lower surface side of the piezoelectric stacked body. The piezoelectric stacked body includes a plurality of piezoelectric portions. The plurality of piezoelectric portions include: a first piezoelectric portion, which is the piezoelectric portion closest to the upper electrode; a second piezoelectric portion, which is the piezoelectric portion closest to the lower electrode; and one or more central piezoelectric portions, which are the piezoelectric portions between the first piezoelectric portion and the second piezoelectric portion. Among the plurality of piezoelectric portions, two piezoelectric portions that are adjacent to one another in the first direction have displacement directions in a first mode that are different directions. At least one of the first piezoelectric portion and the second piezoelectric portion has a plurality of piezoelectric films that have the same displacement direction in the first mode. Among the plurality of piezoelectric films, two piezoelectric films that are adjacent to one another in the first direction have displacement directions in a second mode that are different directions.

Description

Piezoelectric Devices

[0001] The present invention relates to a piezoelectric device.

[0002] Patent Document 1 discloses a thin-film resonator having three or more piezoelectric layers between a first electrode and a second electrode, wherein the polarization vector in each piezoelectric layer is oriented so as to be inclined with respect to the normal to a plane parallel to the thin-film resonator, the polarization vectors in each piezoelectric layer are projected onto the normal in the same direction, and the polarization vectors in odd-numbered piezoelectric layers counting from the first electrode side are projected onto the plane in the opposite direction to the polarization vectors in even-numbered piezoelectric layers counting from the first electrode side.

[0003] JP 2010-178543 A

[0004] In each piezoelectric layer of the thin film resonator disclosed in Patent Document 1, an imbalance in displacement may occur between the piezoelectric portion in contact with the electrode and the piezoelectric portion not in contact with the electrode. In this case, when the thin film resonator disclosed in Patent Document 1 is incorporated into a filter, unwanted waves near the resonance point may be generated near the passband. Therefore, the piezoelectric portion of the thin film resonator disclosed in Patent Document 1 may not be able to sufficiently suppress unwanted waves.

[0005] The present invention is intended to solve the above-mentioned problems, and has an object to provide a piezoelectric device that suppresses unwanted waves.

[0006] A piezoelectric device according to one aspect of the present invention includes a piezoelectric stack having a thickness in a first direction and having an upper surface that is a surface on one side in the first direction and a lower surface that is a surface on the other side in the first direction; a support member provided on the lower surface side of the piezoelectric stack; an upper electrode provided on the upper surface side of the piezoelectric stack; and a lower electrode provided on the lower surface side of the piezoelectric stack, wherein the piezoelectric stack has a plurality of piezoelectric portions, the plurality of piezoelectric portions including a first piezoelectric portion that is the piezoelectric portion closest to the upper electrode, a second piezoelectric portion that is the piezoelectric portion closest to the lower electrode, and a second piezoelectric portion that is between the first piezoelectric portion and the second piezoelectric portion. and one or more central piezoelectric portions which are piezoelectric portions each including one of the plurality of piezoelectric portions and adjacent to each other in the first direction, the displacement direction of thickness-extensional vibration of one of the piezoelectric portions is different from the displacement direction of thickness-extensional vibration of the other piezoelectric portion, at least one of the first piezoelectric portion and the second piezoelectric portion has a plurality of piezoelectric films having the same displacement direction of thickness-extensional vibration, and the plurality of piezoelectric films include two piezoelectric films each adjacent to each other in the first direction, the displacement direction of thickness-extensional vibration of one of the piezoelectric films is different from the displacement direction of thickness-extensional vibration of the other piezoelectric film.

[0007] According to the present invention, a piezoelectric device that suppresses unwanted waves can be provided.

[0008] FIG. 1 is a schematic plan view showing an example of a piezoelectric device according to the first embodiment. FIG. 2 is a schematic cross-sectional view taken along line II-II in FIG. 1 . FIG. 3 is a schematic cross-sectional view of a piezoelectric device according to the second embodiment. FIG. 4 is a schematic cross-sectional view of a piezoelectric device according to the third embodiment. FIG. 5 is a schematic cross-sectional view of a piezoelectric device according to a first modified example. FIG. 6 is a schematic cross-sectional view of a piezoelectric device according to Comparative Example 1-1. FIG. 7 is a schematic cross-sectional view of a piezoelectric device according to Comparative Example 1-2. FIG. 8 is a schematic cross-sectional view of a piezoelectric device according to Comparative Example 2-1. FIG. 9 is a schematic cross-sectional view of a piezoelectric device according to Comparative Example 2-2. FIG. 10 is a schematic cross-sectional view of a piezoelectric device according to Comparative Example 3-1. FIG. 11 is a schematic cross-sectional view of a piezoelectric device according to Comparative Example 3-2. FIG. 12 is a graph showing the resonance characteristics of the piezoelectric device according to Example 1-1. FIG. 13 is a graph showing the resonance characteristics of the piezoelectric device according to Comparative Example 1-1. FIG. 14 is a graph showing the resonance characteristics of the piezoelectric device according to Comparative Example 1-2. FIG. 15 is a graph showing the resonance characteristics of the piezoelectric device according to Example 2-1. Fig. 16 is a diagram showing the resonance characteristics of a piezoelectric device according to Comparative Example 2-1. Fig. 17 is a diagram showing the resonance characteristics of a piezoelectric device according to Comparative Example 2-2. Fig. 18 is a diagram showing the resonance characteristics of a piezoelectric device according to Example 3-1. Fig. 19 is a diagram showing the resonance characteristics of a piezoelectric device according to Comparative Example 3-1. Fig. 20 is a diagram showing the resonance characteristics of a piezoelectric device according to Comparative Example 3-2. Fig. 21 is a schematic cross-sectional view of a piezoelectric device according to a second modified example.

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. However, the present disclosure is not limited to these embodiments. Note that each embodiment described in the present disclosure is an example, and in the second and subsequent embodiments, descriptions of modifications in which partial substitution or combination of configurations is possible between different embodiments, and of matters common to the first embodiment will be omitted, and only differences will be described. In particular, similar effects resulting from similar configurations will not be mentioned sequentially for each embodiment. Furthermore, in the present disclosure, numerical values ​​include the range of rounding.

[0010] In this disclosure, unless otherwise specified, the positive and negative values ​​of angles are distinguished, with counterclockwise rotation being positive and clockwise rotation being negative. Furthermore, in this disclosure, unless otherwise specified, one direction and the opposite direction (reverse direction) of that direction are distinguished. That is, "one direction is the same as another direction" means that that one direction is parallel to that other direction and that that one direction and that other direction are the same direction. Furthermore, when one direction and another direction are opposite directions (reverse directions), that one direction and that other direction are different directions. In this disclosure, "two directions are the same" includes when the angle between the two directions is between -3° and +3°. In other words, "two directions are opposite directions" includes when the angle between the opposite direction of one of the two directions and the other direction is between -3° and +3°. Furthermore, when describing directions in a Cartesian coordinate system in this disclosure, the right-handed system is used.

[0011] First Embodiment FIG. 1 is a schematic plan view illustrating an example of a piezoelectric device according to a first embodiment. FIG. 2 is a schematic cross-sectional view taken along line II-II in FIG. 1. The piezoelectric device 1 according to the first embodiment includes a support member 10, a piezoelectric stack 20, an upper electrode 31, and a lower electrode 32. The piezoelectric device 1 is a resonator that utilizes bulk waves, i.e., a BAW (Bulk Acoustic Wave) element. In the first embodiment, the piezoelectric device 1 is, for example, a piezoelectric element configured to utilize thickness-longitudinal vibration of the piezoelectric stack 20. In the following description, the thickness direction of the piezoelectric stack 20 is referred to as the Z0 direction, the direction perpendicular to the Z0 direction is referred to as the X0 direction, and the direction perpendicular to the Z0 and X0 directions is referred to as the Y0 direction. In other words, the X0 direction, the Y0 direction, and the Z0 direction are directions that form a Cartesian coordinate system. In the present disclosure, the Z0 direction is an example of a "first direction." In the following description, the Z0 direction may be referred to as "up" and the direction opposite to the Z0 direction as "down." Here, the X0 direction is a direction along the side of the piezoelectric device 1 according to this embodiment, as shown in FIG. 1, for example. If the upper electrode 31 and the lower electrode 32 are rectangular, the X0 direction may be a side direction of the upper electrode 31 and the lower electrode 32. In this disclosure, the first mode refers to the main mode of the piezoelectric device, and the second mode refers to a mode different from the first mode. In the first embodiment, the first mode is thickness extensional vibration, and the second mode is thickness shear vibration.

[0012] (Piezoelectric laminate) The piezoelectric laminate 20 is a flat laminate having a thickness in the Z0 direction. The piezoelectric laminate 20 has an upper surface 20a and a lower surface 20b. The upper surface 20a and the lower surface 20b are examples of the "main surfaces of the piezoelectric laminate" in the present disclosure. The thickness of the piezoelectric laminate 20 is not particularly limited, but is preferably 1 μm or less. This allows for good resonance characteristics.

[0013] The piezoelectric laminate 20 is a laminate including a plurality of piezoelectric portions. In the present disclosure, the term "piezoelectric portion" refers to a portion of the piezoelectric laminate 20 that includes a piezoelectric body and has the same continuous displacement direction in the first mode. That is, in the first embodiment, the term "piezoelectric portion" refers to a portion of the piezoelectric laminate 20 that includes a piezoelectric body and has the same continuous displacement direction in thickness longitudinal vibration. In other words, in the first embodiment, one piezoelectric portion does not include a portion with a different displacement direction in thickness longitudinal vibration. In the first embodiment, the piezoelectric laminate 20 includes a first piezoelectric portion 21, a second piezoelectric portion 22, and a third piezoelectric portion 23 as piezoelectric portions. The first piezoelectric portion 21, the second piezoelectric portion 22, and the third piezoelectric portion 23 are stacked in the Z0 direction to form a laminate. In the present disclosure, the piezoelectric portion is a single layer or a laminate. In the first embodiment, the first piezoelectric portion 21 and the second piezoelectric portion 22 are laminates having a plurality of piezoelectric films, and the third piezoelectric portion 23 is a single layer. The first piezoelectric portion 21 is the piezoelectric portion of the piezoelectric stack 20 that is closest to the upper electrode 31. That is, the first piezoelectric portion 21 is the uppermost piezoelectric portion of the piezoelectric stack 20. The second piezoelectric portion 22 is the piezoelectric portion of the piezoelectric stack 20 that is closest to the lower electrode 32. That is, the second piezoelectric portion 22 is the lowermost piezoelectric portion of the piezoelectric stack 20. The third piezoelectric portion 23 is a piezoelectric portion located between the first piezoelectric portion 21 and the second piezoelectric portion 22. That is, the third piezoelectric portion 23 is an example of a "central piezoelectric portion" in the present disclosure. In the example of FIG. 2 , the upper surface of the first piezoelectric portion 21 corresponds to the upper surface 20a of the piezoelectric stack 20. The lower surface of the second piezoelectric portion 22 corresponds to the lower surface 20b of the piezoelectric stack 20. In addition, the stack is formed by stacking the first piezoelectric portion 21, the third piezoelectric portion 23, and the second piezoelectric portion 22 in this order. This improves the mechanical strength and voltage resistance of the piezoelectric stack 20. The first piezoelectric portion 21, the second piezoelectric portion 22, and the third piezoelectric portion 23 will be described in detail later.

[0014] At least one of the first piezoelectric portion 21 and the second piezoelectric portion 22 includes multiple piezoelectric films. That is, at least one of the first piezoelectric portion 21 and the second piezoelectric portion 22 is a laminate having multiple piezoelectric films. In the present disclosure, a piezoelectric film refers to a film that includes a piezoelectric material and in which the displacement direction of the first mode and the displacement direction of the second mode are continuously the same. That is, in the first embodiment, a piezoelectric film refers to a film that includes a piezoelectric material and in which the displacement direction of thickness-extensional vibration and the displacement direction of thickness-shear vibration are continuously the same. In other words, in the first embodiment, one piezoelectric film does not include a portion in which the displacement direction of thickness-extensional vibration or the displacement direction of thickness-shear vibration differs. In the first embodiment, the first piezoelectric portion 21 is a laminate having a first piezoelectric film 211 and a second piezoelectric film 212 as piezoelectric films. Furthermore, the second piezoelectric portion 22 is a laminate having a first piezoelectric film 221 and a second piezoelectric film 222 as piezoelectric films. The first piezoelectric film 211 is the piezoelectric film closest to the upper electrode 31 among the multiple piezoelectric films included in the first piezoelectric portion 21, and the first piezoelectric film 221 is the piezoelectric film closest to the lower electrode 32 among the multiple piezoelectric films included in the second piezoelectric portion 22. That is, the first piezoelectric films 211, 221 are the piezoelectric films located on the outer side in the direction parallel to the Z0 direction among the multiple piezoelectric films included in the first piezoelectric portion 21 or the second piezoelectric portion 22. The second piezoelectric films 212, 222 are the piezoelectric films located on the central piezoelectric portion (third piezoelectric portion 23) side of each of the first piezoelectric films 211, 221 in the direction parallel to the Z0 direction among the multiple piezoelectric films included in the first piezoelectric portion 21 or the second piezoelectric portion 22. That is, the first piezoelectric films 211, 221 are the piezoelectric films located on the inner side in the direction parallel to the Z0 direction among the multiple piezoelectric films included in the first piezoelectric portion 21 or the second piezoelectric portion 22. The first piezoelectric films 211 and 221 and the second piezoelectric films 212 and 222 will be described in detail later.

[0015] The piezoelectric laminate may be provided with a through hole communicating with a space 13, which will be described later. In this case, the through hole is provided at a position overlapping the space 13 in plan view in the Z0 direction. The through hole may or may not penetrate the upper electrode and the lower electrode.

[0016] (Functional Electrode) The upper electrode 31 is provided on the upper surface 20a of the piezoelectric stack 20. The lower electrode 32 is provided on the lower surface 20b of the piezoelectric stack 20. The upper electrode 31 and the lower electrode 32 are examples of "functional electrodes" in the present disclosure. The upper electrode 31 and the lower electrode 32 are made of a metal or alloy such as aluminum (Al), platinum (Pt), copper (Cu), tungsten (W), or molybdenum (Mo). The upper electrode 31 and the lower electrode 32 may be a laminate of two or more layers made of different materials, and may have an adhesion layer made of titanium (Ti), a nickel-chromium alloy (NiCr), or the like.

[0017] As shown in FIG. 1 , the upper electrode 31 has a circular main electrode portion 31a and an extension portion 31b extending from the main electrode portion 31a in a direction perpendicular to the Z0 direction. The lower electrode 32 has a circular main electrode portion 32a and an extension portion 32b extending from the main electrode portion 32a in a direction perpendicular to the Z0 direction. In a plan view in the Z0 direction, the circular main electrode portion 31a of the upper electrode 31 and the circular main electrode portion 32a of the lower electrode 32 overlap each other. In other words, the piezoelectric stack 20 is sandwiched between the circular main electrode portion 31a of the upper electrode 31 and the circular main electrode portion 32a of the lower electrode 32. As a result, bulk waves are excited in the region between the circular main electrode portion 31a of the upper electrode 31 and the circular main electrode portion 32a of the lower electrode 32. Note that the shapes of the upper electrode 31 and the lower electrode 32 are merely examples and are not limited thereto. In the following description, the region where the upper electrode 31 and the lower electrode 32 overlap when viewed in a plan view in the Z0 direction may be referred to as an excitation region C.

[0018] (Support Member) The support member 10 is provided opposite the lower surface 20b of the piezoelectric stack 20. In the first embodiment, the support member 10 includes a support substrate 11 and an intermediate layer 12. The support substrate 11 is a substrate made of silicon (Si), quartz crystal, or the like. The intermediate layer 12 is provided on the piezoelectric stack 20 side of the support substrate 11. The intermediate layer 12 is made of a dielectric material such as silicon oxide.

[0019] The support member 10 has a space 13. In the example of Fig. 2, the space 13 is the space inside a recess provided on the piezoelectric laminate 20 side of the intermediate layer 12. The space 13 is provided so as to overlap with the excitation region C when viewed in a plan view in the Z0 direction. This allows bulk waves generated when the piezoelectric device 1 is driven to be reflected by the space 13. In the example of Fig. 1, the region overlapping with the space 13 when viewed in a plan view in the Z0 direction is circular, but this is merely an example and may be any other shape, such as rectangular.

[0020] (Piezoelectric portions and piezoelectric films) The first piezoelectric portion 21, the second piezoelectric portion 22, the third piezoelectric portion 23, and the first piezoelectric films 211, 221, and the second piezoelectric films 212, 222 will be described in detail below. In the following description, all of the piezoelectric portions included in the piezoelectric stack 20 may be collectively referred to as "plurality of piezoelectric portions." Furthermore, all of the piezoelectric films included in one piezoelectric portion may be collectively referred to as "plurality of piezoelectric films." Furthermore, in the present disclosure, the thickness of the piezoelectric portions and piezoelectric films refers to the average length of the piezoelectrics or piezoelectric portions in the excitation region C in the Z0 direction.

[0021] 2, the thickness d3 of the third piezoelectric portion 23 is larger than at least one of the thickness d1 of the first piezoelectric portion 21 and the thickness d2 of the second piezoelectric portion 22, and is preferably larger than both of them. This makes it possible to suppress imbalance in the displacement of the first piezoelectric portion 21 caused by the upper electrode 31 or imbalance in the displacement of the thickness-extensional vibration of the second piezoelectric portion 22 caused by the lower electrode 32, and to suppress unwanted waves of the thickness-extensional vibration.

[0022] As shown in FIG. 2 , the thickness d11 of the first piezoelectric film 211 is preferably equal to the thickness d21 of the first piezoelectric film 221, and the thickness d12 of the second piezoelectric film 212 is preferably equal to the thickness d22 of the second piezoelectric film 222. This improves the symmetry of the piezoelectric stack 20 in the Z0 direction, thereby improving the resonance characteristics. Note that in the example of FIG. 2 , the thicknesses d11 and d21 of the first piezoelectric film 211 are equal to the thicknesses d12 and d22 of the second piezoelectric film 212, but this is not limited thereto. For example, the thicknesses d12 and d22 of the second piezoelectric film 212 may be smaller than the thicknesses d11 and d21 of the first piezoelectric film 211. Even in this case, the imbalance in displacement of thickness shear vibration can be suppressed, and unwanted waves can be further suppressed. Furthermore, the thicknesses d12 and d22 of the second piezoelectric film 212 may be greater than the thicknesses d11 and d21 of the first piezoelectric film 211.

[0023] (Displacement of Thickness-Extended Vibration) Of two piezoelectric portions included in the plurality of piezoelectric portions and adjacent to each other in the Z0 direction, the displacement direction of the thickness-extensional vibration of one piezoelectric portion is different from the displacement direction of the thickness-extensional vibration of the other piezoelectric portion. Of two piezoelectric portions included in the plurality of piezoelectric portions and adjacent to each other in the Z0 direction, the displacement direction of the thickness-extensional vibration of one piezoelectric portion is preferably opposite to the displacement direction of the thickness-extensional vibration of the other piezoelectric portion. In the present disclosure, the displacement direction of the thickness-extensional vibration refers to the direction of the thickness-extensional vibration mode. The displacement direction TL1 of the thickness-extensional vibration of the first piezoelectric portion 21 and the displacement direction TL3 of the thickness-extensional vibration of the third piezoelectric portion 23 are opposite directions, and the displacement direction TL3 of the thickness-extensional vibration of the third piezoelectric portion 23 and the displacement direction TL2 of the thickness-extensional vibration of the second piezoelectric portion 22 are opposite directions. Here, the displacement direction TL1 of the thickness-longitudinal vibration of the first piezoelectric portion 21 refers to the displacement directions TL11 and TL12 of the thickness-longitudinal vibration of the piezoelectric films (the first piezoelectric film 211 and the second piezoelectric film 212) included in the first piezoelectric portion 21. Similarly, the displacement direction TL2 of the thickness-longitudinal vibration of the second piezoelectric portion 22 refers to the displacement directions TL21 and TL22 of the thickness-longitudinal vibration of the piezoelectric films (the first piezoelectric film 221 and the second piezoelectric film 222) included in the second piezoelectric portion 22.

[0024] In the following description, one of the displacement directions of the thickness-extensional vibration of a piezoelectric portion or a piezoelectric film is referred to as the first displacement direction of the thickness-extensional vibration, and a direction different from the first displacement direction of the thickness-extensional vibration is referred to as the second displacement direction of the thickness-extensional vibration. In the first embodiment, the piezoelectric stack 20 has either the first displacement direction of the thickness-extensional vibration or the second displacement direction of the thickness-extensional vibration. In other words, in the piezoelectric stack 20 according to the first embodiment, piezoelectric portions having the first displacement direction of the thickness-extensional vibration and piezoelectric portions having the second displacement direction of the thickness-extensional vibration are alternately stacked. In the example of FIG. 2 , the thickness-extensional vibration displacement direction TL1 and the thickness-extensional vibration displacement direction TL2 are the same and correspond to the first displacement direction of the thickness-extensional vibration. Also, in the example of FIG. 2 , the thickness-extensional vibration displacement direction TL3 is different from the thickness-extensional vibration displacement directions TL1 and TL2 and corresponds to the second displacement direction of the thickness-extensional vibration. In the example of Fig. 2, the displacement direction of the first thickness-longitudinal vibration and the displacement direction of the second thickness-longitudinal vibration are opposite to each other. Note that in the example of Fig. 2, the displacement direction of the first thickness-longitudinal vibration is downward and the displacement direction of the second thickness-longitudinal vibration is upward, but this is merely an example and is not limiting. For example, the displacement direction of the first thickness-longitudinal vibration may be upward and the displacement direction of the second thickness-longitudinal vibration may be downward.

[0025] The displacement direction of the thickness-extensional vibration of the piezoelectric portion can be measured by X-ray diffraction measurement of the cross section of the piezoelectric laminate 20 along the Z0 direction. More specifically, the crystal axis direction of the piezoelectric portion is measured by X-ray diffraction measurement, and the direction of the thickness-extensional vibration mode is determined for each piezoelectric portion based on the measured crystal axis direction. This allows the direction of the thickness-extensional mode for each piezoelectric portion to be measured as the displacement direction of the thickness-extensional vibration.

[0026] (Displacement of Thickness Shear Vibration) Of two piezoelectric films included in a plurality of piezoelectric films and adjacent to each other in the Z0 direction, the displacement direction of the thickness shear vibration of one piezoelectric film is different from the displacement direction of the thickness shear vibration of the other piezoelectric film. Of two piezoelectric films included in a plurality of piezoelectric films and adjacent to each other in the Z0 direction, the displacement direction of the thickness shear vibration of one piezoelectric film is preferably opposite to the displacement direction of the thickness shear vibration of the other piezoelectric film. In the present disclosure, the displacement direction of the thickness shear vibration refers to the direction of the thickness shear vibration mode. The displacement direction TS11 of the thickness shear vibration of the first piezoelectric film 211 and the displacement direction TS12 of the thickness shear vibration of the second piezoelectric film 212 are opposite directions, and the displacement direction TS21 of the thickness shear vibration of the first piezoelectric film 221 and the displacement direction TS22 of the thickness shear vibration of the second piezoelectric film 222 are opposite directions.

[0027] It is preferable that the displacement direction of the thickness-shear vibration of the piezoelectric film on the central piezoelectric portion side among the plurality of piezoelectric films is the same as the displacement direction of the thickness-shear vibration of the central piezoelectric portion adjacent in the Z0 direction of the piezoelectric film on the central piezoelectric portion side. The displacement directions TS12 and TS22 of the thickness-shear vibration of the second piezoelectric films 212 and 222 and the displacement direction TS3 of the thickness-shear vibration of the third piezoelectric portion 23 are the same direction.

[0028] In the following description, one of the thickness-shear vibration displacement directions of the piezoelectric portion or piezoelectric film is referred to as the first thickness-shear vibration displacement direction, and a direction different from the first thickness-shear vibration displacement direction is referred to as the second thickness-shear vibration displacement direction. In the first embodiment, the piezoelectric laminate 20 has either the first thickness-shear vibration displacement direction or the second thickness-shear vibration displacement direction. In the example of FIG. 2 , the thickness-shear vibration displacement direction TS11 and the thickness-shear vibration displacement direction TS21 are the same and correspond to the first thickness-shear vibration displacement direction. Also, in the example of FIG. 2 , the thickness-shear vibration displacement directions TS12, TS22, and TS3 are different from the thickness-shear vibration displacement directions TS11 and TS21 and correspond to the second thickness-shear vibration displacement direction. In the example of FIG. 2 , the first thickness-shear vibration displacement direction and the second thickness-shear vibration displacement direction are opposite directions. In the example of Figure 2, the displacement direction of the first thickness shear vibration is the X0 direction, and the displacement direction of the second thickness shear vibration is the opposite direction to the X0 direction, but this is just one example and is not limited to this.For example, the displacement direction of the first thickness shear vibration may be the opposite direction to the X0 direction, and the displacement direction of the second thickness shear vibration may be the X0 direction, or the displacement directions of the first thickness shear vibration and the second thickness shear vibration may be directions perpendicular to the Z0 direction and intersect with the X0 direction.

[0029] The displacement direction of the thickness-shear vibration of the piezoelectric film or piezoelectric part can be measured by X-ray diffraction measurement of the cross section of the piezoelectric stack 20 along the Z0 direction. More specifically, the crystal axis direction of the piezoelectric film or piezoelectric part is measured by X-ray diffraction measurement, and the direction of the thickness-shear vibration mode is determined for each piezoelectric film or piezoelectric part based on the measured crystal axis direction. This allows the direction of the thickness-shear mode for each piezoelectric film or piezoelectric part to be measured as the displacement direction of the thickness-shear vibration.

[0030] (Piezoelectric Body) The piezoelectric laminate 20 is preferably made of the same material. The piezoelectric laminate 20 is preferably made of lithium niobate (LiNbO ３ ) or lithium tantalate (LiTaO ３The crystal direction of the piezoelectric portion will be described in detail below. In the following description, the piezoelectric portion or the piezoelectric material constituting the piezoelectric film will be simply referred to as the piezoelectric material. In the first embodiment, the piezoelectric material is preferably made of lithium niobate (LiNbO ３ ) or lithium tantalate (LiTaO ３ )

[0031] Lithium niobate (LiNbO ３ ) and lithium tantalate (LiTaO ３ ) has a trigonal crystal structure and has an a-axis and a c-axis as crystal axes. Here, the directions of the a-axis and c-axis of the crystal of the piezoelectric body can be determined by X-ray diffraction measurement of a cross section of the piezoelectric stack 20 along the Z0 direction. In the following explanation, the crystal axes of the piezoelectric body may be described as the a-axis being the x-axis, the c-axis being the z-axis, and the axis perpendicular to the a-axis and c-axis that forms a right-handed system with the x-axis and z-axis being the y-axis. In other words, the x-axis direction, y-axis direction, and z-axis direction are perpendicular to each other and form a Cartesian coordinate system.

[0032] (Euler Angles) In the present disclosure, the Euler angles of the piezoelectric body of the piezoelectric section being (α, β, γ) refers to the directions of the crystal axes (x-axis direction, y-axis direction, z-axis direction) of the piezoelectric body satisfying the condition that "the directions of the axes (x'''-axis direction, y'''-axis direction, z'''-axis direction obtained by rotating and moving the x-axis direction, y-axis direction, and z-axis direction in the following order (A), (B), and (C) are the same as the directions of the spatial coordinate axes (X0 direction, Y0 direction, Z0 direction)." In other words, the top surface of the piezoelectric section (the surface on the Z0 direction side) is a surface whose normal is the z'''-axis and contains the x'''-axis. Incidentally, the definition of right-handed Euler angles is given in "Acoustic Wave Device Technology Handbook" (edited by the 150th Committee on Acoustic Wave Device Technology of the Japan Society for the Promotion of Science, 1st Edition, 1st Printing, published November 30, 1991, Ohmsha, p. 549). In this disclosure, the definition of right-handed Euler angles described in the document is used, and the X0 direction in this disclosure corresponds to the propagation direction of the surface waves of the surface acoustic wave filter described in the document. (A) Using the z-axis as the rotation axis, the x-axis is rotated counterclockwise as viewed from the z-axis direction by a rotation angle α. As a result, the x'-axis, y'-axis, and z'-axis are defined as axes after rotation. Here, the z-axis is not rotated, so the z'-axis is in the same direction as the z-axis. (B) Using the x'-axis as the rotation axis, the z'-axis is rotated counterclockwise as viewed from the x'-axis direction by a rotation angle β. As a result, the x"-axis, y"-axis, and z"-axis are defined as axes after rotation. Here, because the x'-axis is not rotated, the x"-axis is in the same direction as the x'-axis. (C) Using the z"-axis as the rotation axis, the x"-axis is rotated counterclockwise as viewed from the z"-axis direction by a rotation angle γ. As a result, the x'"-axis, y'"-axis, and z'"-axis are defined as axes after rotation. Here, the z'' axis does not rotate, so the z''' axis is in the same direction as the z'' axis.

[0033] In the following description, the rotation angle α from the x-axis to the x'-axis may be described as the first component of the Euler angle, the rotation angle β from the z'-axis to the z"-axis may be described as the second component of the Euler angle, and the rotation angle γ from the x"-axis to the x'"-axis may be described as the third component of the Euler angle. In the present disclosure, the first component of the Euler angle will be described assuming that the counterclockwise rotation is positive when viewed from the z-axis direction and the clockwise rotation is negative when viewed from the z-axis direction. Similarly, the second component of the Euler angle will be described assuming that the counterclockwise rotation is positive when viewed from the x'-axis direction and the clockwise rotation is negative when viewed from the x'-axis direction. Similarly, the third component of the Euler angle will be described assuming that the counterclockwise rotation is positive when viewed from the z"-axis direction and the clockwise rotation is negative when viewed from the z"-axis direction.

[0034] In the following description, the piezoelectric portion or the piezoelectric film has a displacement direction of the first thickness longitudinal vibration and a displacement direction of the first thickness shear vibration. ３ or LiTaO ３ ) Euler angles are (φ １１ , θ １１ , ψ １１ ) and the piezoelectric portion or the piezoelectric film having the displacement direction of the first thickness longitudinal vibration and the displacement direction of the second thickness shear vibration. ３ or LiTaO ３ ) Euler angles are (φ １２ , θ １２ , ψ １２ ) and the piezoelectric portion or the piezoelectric film having the displacement direction of the second thickness longitudinal vibration and the displacement direction of the second thickness shear vibration. ３ or LiTaO ３ ) Euler angles are (φ ２２ , θ ２２ , ψ ２２ ) and the piezoelectric body of the first piezoelectric portion 21 (LiNbO ３ or LiTaO ３ The x-axis direction (a-axis direction), y-axis direction, and z-axis direction (c-axis direction) of the crystal of the second piezoelectric portion 22 are represented as the X1 direction, the Y1 direction, and the Z1 direction, respectively. Here, the X1 direction, the Y1 direction, and the Z1 direction are perpendicular to each other. Similarly, the piezoelectric body (LiNbO ３ or LiTaO ３The x-axis direction (a-axis direction), y-axis direction, and z-axis direction (c-axis direction) of the crystal are represented as the X2 direction, the Y2 direction, and the Z2 direction, respectively. Here, the X2 direction, the Y2 direction, and the Z2 direction are perpendicular to each other.

[0035] As described above, the piezoelectric laminate 20 is preferably made of a rotated Y-cut lithium niobate or lithium tantalate single crystal. The rotated Y-cut is a piezoelectric portion or a piezoelectric film having a first component φ of the Euler angle of the piezoelectric material. １１ , φ １２ , φ ２２ The first component φ of the Euler angles of the piezoelectric elements of the piezoelectric stack 20 is equal to or larger than −3° and equal to or smaller than +3°. １１ , φ １２ , φ ２２ It is more preferable that the angle is 0°. This can improve the resonance characteristics.

[0036] When the piezoelectric laminate 20 is made of a single crystal of lithium niobate, θ １１ is preferably 123° or more and 129° or less, or 303° or more and 309° or less, and is preferably 126° or 306°. １１ If is in this range, θ １１ -3°≦θ １２ ≦θ １１ +3° is preferable, and θ １２ = θ １１ It is more preferable that θ １１ and θ １２ If is in this range, θ １１ +177°≦θ ２２ ≦θ １１ Preferably, θ is +183°. ２２ = θ １１ It is more preferable that the angle is +180°. １１ , θ １２ and θ ２２ If is in this range, ψ １１ can be any value, and ψ １２ and ψ ２２ is ψ １１ +177°≦ψ １２ ≦ψ １１ +183° and ψ １１ -3°≦ψ ２２ ≦ψ１１ It is preferable that the angle satisfies +3°, and ψ １１ = ψ １２ +180°=ψ ２２ As a result, the displacement direction of the first thickness-extensional vibration is opposite to the displacement direction of the second thickness-extensional vibration, so that unwanted waves of the thickness-extensional vibration can be suppressed, and the displacement direction of the first thickness-shear vibration is opposite to the displacement direction of the second thickness-shear vibration, so that unwanted waves of the thickness-shear vibration can be suppressed.

[0037] Although an example of the piezoelectric device according to the first embodiment has been described above, the piezoelectric device according to the first embodiment is not limited to the one described above.

[0038] For example, a silicon oxide (SiO ２ ) or an adhesive layer, or other layer different from the first piezoelectric portion 21 and the second piezoelectric portion 22 may be provided.

[0039] For example, the support member 10 may be provided with an acoustic multilayer film instead of the space 13. The acoustic multilayer film has a laminated structure of a low acoustic impedance layer with a relatively low acoustic impedance and a high acoustic impedance layer with a relatively high acoustic impedance. The low acoustic impedance layer may be made of, for example, SiO ２ The high acoustic impedance layer is, for example, a metal layer such as W, Pt, or Mo, or a dielectric layer such as tantalum oxide, tungsten oxide, or aluminum nitride. When an acoustic multilayer film is used, bulk waves can be confined within the piezoelectric laminate 20 without using the space 13.

[0040] As described above, the piezoelectric device 1 according to the first embodiment includes a piezoelectric stack 20 having a thickness in a first direction (Z0 direction) and having an upper surface 20a that is a surface on one side in the first direction and a lower surface 20b that is a surface on the other side in the first direction, a support member 10 provided on the lower surface 20b side of the piezoelectric stack 20, an upper electrode 31 provided on the upper surface 20a side of the piezoelectric stack 20, and a lower electrode 32 provided on the lower surface 20b side of the piezoelectric stack 20. The piezoelectric stack 20 has a plurality of piezoelectric portions. The plurality of piezoelectric portions include a first piezoelectric portion 21 that is the piezoelectric portion closest to the upper electrode 31, a second piezoelectric portion 22 that is the piezoelectric portion closest to the lower electrode 32, and one or more central piezoelectric portions that are piezoelectric portions between the first piezoelectric portion 21 and the second piezoelectric portion 22. Of two piezoelectric parts included in the plurality of piezoelectric parts and adjacent to each other in the first direction, the displacement direction of the first mode (thickness longitudinal vibration) of one piezoelectric part is different from the displacement direction of the first mode (thickness longitudinal vibration) of the other piezoelectric part. At least one of the first piezoelectric part 21 and the second piezoelectric part 22 has a plurality of piezoelectric films having the same displacement direction of the first mode (thickness longitudinal vibration). Of two piezoelectric films included in the plurality of piezoelectric films and adjacent to each other in the first direction, the displacement direction of the second mode (thickness shear vibration) of one piezoelectric film is different from the displacement direction of the second mode (thickness shear vibration) of the other piezoelectric film. This makes it possible to suppress imbalance in the displacement of the second mode (thickness shear vibration) of the first piezoelectric part 21 due to the upper electrode 31 or imbalance in the displacement of the second mode (thickness shear vibration) of the second piezoelectric part 22 due to the lower electrode 32, thereby suppressing unwanted waves.

[0041] In a preferred embodiment, the thickness d1 of the first piezoelectric portion 21 is smaller than the thickness of the central piezoelectric portion (thickness d3 of the third piezoelectric portion 23), and the thickness d2 of the second piezoelectric portion 22 is smaller than the thickness of the central piezoelectric portion (thickness d3 of the third piezoelectric portion 23). This makes it possible to suppress imbalance in the displacement of the first mode (thickness longitudinal vibration) of the first piezoelectric portion 21 caused by the upper electrode 31 or imbalance in the displacement of the first mode (thickness longitudinal vibration) of the second piezoelectric portion 22 caused by the lower electrode 32, thereby further suppressing unwanted waves.

[0042] In a preferred embodiment, of two piezoelectric films included in the plurality of piezoelectric films and adjacent to each other in the first direction, the thickness of one of the piezoelectric films on the central piezoelectric portion side is equal to or less than the thickness of the other piezoelectric film, which can further suppress imbalance in the second mode (thickness shear vibration) displacement of the first piezoelectric portion 21 due to the upper electrode 31 or imbalance in the second mode (thickness shear vibration) displacement of the second piezoelectric portion 22 due to the lower electrode 32, thereby further suppressing unwanted waves.

[0043] In a preferred embodiment, of two piezoelectric portions included in the plurality of piezoelectric portions and adjacent to each other in the first direction, the displacement direction of the first mode (thickness longitudinal vibration) of one piezoelectric portion is opposite to the displacement direction of the first mode (thickness longitudinal vibration) of the other piezoelectric portion, thereby suppressing imbalance in the displacement of the first mode (thickness longitudinal vibration) of the first piezoelectric portion 21 due to the upper electrode 31 or imbalance in the displacement of the first mode (thickness longitudinal vibration) of the second piezoelectric portion 22 due to the lower electrode 32, thereby further suppressing unwanted waves.

[0044] In a preferred embodiment, the displacement direction of the second mode (thickness shear vibration) of one of two piezoelectric films that are included in the plurality of piezoelectric films and adjacent to each other in the first direction is opposite to the displacement direction of the second mode (thickness shear vibration) of the other piezoelectric film, thereby further suppressing imbalance in the displacement of the second mode (thickness shear vibration) of the first piezoelectric portion 21 due to the upper electrode 31 or imbalance in the displacement of the second mode (thickness shear vibration) of the second piezoelectric portion 22 due to the lower electrode 32, thereby further suppressing unwanted waves.

[0045] In a preferred embodiment, the thickness d1 of the first piezoelectric portion 21 is equal to the thickness d2 of the second piezoelectric portion 22. This improves the symmetry of the piezoelectric laminate 20 from top to bottom, thereby achieving good resonance characteristics.

[0046] In a preferred embodiment, both the first piezoelectric portion 21 and the second piezoelectric portion 22 have multiple piezoelectric films, which can further suppress imbalance in the second mode (thickness shear vibration) displacement of the first piezoelectric portion 21 caused by the upper electrode 31 and imbalance in the second mode (thickness shear vibration) displacement of the second piezoelectric portion 22 caused by the lower electrode 32, thereby further suppressing unwanted waves.

[0047] In a more preferable embodiment, the plurality of piezoelectric films included in each of the first piezoelectric portion 21 and the second piezoelectric portion 22 are composed of first piezoelectric films 211, 221 and second piezoelectric films 212, 222 adjacent to the first piezoelectric films 211, 221 on the central piezoelectric portion side in the first direction. This further suppresses imbalance in the second mode (thickness shear vibration) displacement of the first piezoelectric portion 21 caused by the upper electrode 31 and imbalance in the second mode (thickness shear vibration) displacement of the second piezoelectric portion 22 caused by the lower electrode 32, thereby further suppressing unwanted waves.

[0048] In a more desirable embodiment, the thickness of the first piezoelectric film 211 of the first piezoelectric portion 21 is equal to the thickness of the first piezoelectric film 221 of the second piezoelectric portion 22, and the thickness of the second piezoelectric film 212 of the first piezoelectric portion 21 is equal to the thickness of the second piezoelectric film 222 of the second piezoelectric portion 22. This improves the symmetry of the piezoelectric stack 20 from top to bottom, thereby achieving good resonance characteristics.

[0049] In a preferred embodiment, the piezoelectric stack 20 has one central piezoelectric portion (third piezoelectric portion 23). Even in this case, imbalance in the second mode (thickness shear vibration) displacement of the first piezoelectric portion 21 due to the upper electrode 31 or imbalance in the second mode (thickness shear vibration) displacement of the second piezoelectric portion 22 due to the lower electrode 32 can be suppressed, thereby suppressing unwanted waves.

[0050] In a preferred embodiment, the displacement direction of the second mode (thickness shear vibration) of the piezoelectric film (second piezoelectric film 212, 222) closest to the central piezoelectric portion among the plurality of piezoelectric films is the same as the displacement direction of the second mode (thickness shear vibration) of the central piezoelectric portion. This can further suppress imbalance in the second mode (thickness shear vibration) displacement of the first piezoelectric portion 21 due to the upper electrode 31 or imbalance in the second mode (thickness shear vibration) displacement of the second piezoelectric portion 22 due to the lower electrode 32, thereby further suppressing unwanted waves.

[0051] Preferably, the piezoelectric laminate 20 is made of a single crystal of lithium niobate or lithium tantalate, which provides good resonance characteristics.

[0052] More preferably, the piezoelectric laminate 20 is made of a rotated Y-cut lithium niobate or lithium tantalate single crystal, which provides better resonance characteristics.

[0053] In a more preferable embodiment, the piezoelectric device 1 according to the first embodiment is a piezoelectric device that utilizes a thickness-extensional vibration mode. The first mode is thickness-extensional vibration, and the second mode is thickness-shear vibration. The plurality of piezoelectric portions and the plurality of piezoelectric films have a first thickness-extensional vibration displacement direction or a second thickness-extensional vibration displacement direction that is a direction different from the first thickness-extensional vibration displacement direction as a displacement direction of the thickness-extensional vibration. The plurality of piezoelectric portions and the plurality of piezoelectric films have a first thickness-extensional vibration displacement direction or a second thickness-extensional vibration displacement direction that is a direction different from the first thickness-extensional vibration displacement direction as a displacement direction of the thickness-extensional vibration. The Euler angles of lithium niobate of the piezoelectric portions or piezoelectric films having the first thickness-extensional vibration displacement direction and the first thickness-extensional vibration displacement direction are (φ １１ , θ １１ , ψ １１ ), then φ １１ is between -3° and 3°, and θ １１ is 123° or more and 129° or less or 303° or more and 309° or less, and ψ １１ is an arbitrary value. The Euler angles of the lithium niobate of the piezoelectric portion or piezoelectric film having the displacement direction of the first thickness longitudinal vibration and the displacement direction of the second thickness shear vibration are defined as (φ １２ , θ １２ , ψ １２ ), then φ １２ is between -3° and 3°, and θ １１ -3°≦θ １２ ≦θ １１ +3° is satisfied, ψ １１ +177°≦ψ １２ ≦ψ １１ +183°. The Euler angles of the lithium niobate of the piezoelectric portion or the piezoelectric film having the displacement direction of the second thickness longitudinal vibration and the displacement direction of the second thickness shear vibration are (φ ２２ , θ ２２ , ψ ２２ ), then φ ２２ is between -3° and 3°, and θ １１ +177°≦θ ２２ ≦θ １１ +183°, and ψ １１ -3°≦ψ ２２ ≦ψ １１This satisfies +3°. This makes it possible to suppress imbalances in the displacement of the thickness-extensional vibration and the thickness-shear vibration of the first piezoelectric portion 21 caused by the upper electrode 31, and in the displacement of the thickness-extensional vibration and the thickness-shear vibration of the second piezoelectric portion 22 caused by the lower electrode 32, thereby further suppressing unwanted waves.

[0054] Second Embodiment Fig. 3 is a schematic cross-sectional view of a piezoelectric device according to a second embodiment. Like Fig. 2, Fig. 3 is a cross-sectional view taken along line II-II in Fig. 1. As shown in Fig. 3, the piezoelectric device 1A according to the second embodiment differs from the piezoelectric device 1 according to the first embodiment in that it further includes a fourth piezoelectric portion 24 located between the third piezoelectric portion 23 and the second piezoelectric portion 22. That is, the piezoelectric stack 20A of the piezoelectric device 1A according to the second embodiment has the third piezoelectric portion 23 and the fourth piezoelectric portion 24 as multiple central piezoelectric portions.

[0055] In the second embodiment, the piezoelectric laminate 20A includes a first piezoelectric portion 21, a second piezoelectric portion 22, a third piezoelectric portion 23, and a fourth piezoelectric portion 24 as piezoelectric portions. The first piezoelectric portion 21, the second piezoelectric portion 22, the third piezoelectric portion 23, and the fourth piezoelectric portion 24 are stacked in the Z0 direction to form a laminate. In the second embodiment, the first piezoelectric portion 21 and the second piezoelectric portion 22 are laminates having multiple piezoelectric films, and the third piezoelectric portion 23 and the fourth piezoelectric portion 24 are single layers. The fourth piezoelectric portion 24 is a piezoelectric portion located between the first piezoelectric portion 21 and the second piezoelectric portion 22. In the example of FIG. 3 , the fourth piezoelectric portion 24 is located between the third piezoelectric portion 23 and the second piezoelectric portion 22. In other words, the third piezoelectric portion 23 and the fourth piezoelectric portion 24 are examples of the "central piezoelectric portion" of the present disclosure. 3, the laminate is formed by laminating the first piezoelectric portion 21, the third piezoelectric portion 23, the fourth piezoelectric portion 24, and the second piezoelectric portion 22 in this order, thereby improving the mechanical strength and voltage resistance of the piezoelectric laminate 20.

[0056] In the example of Figure 3, the thicknesses d12 and d22 of the second piezoelectric film 212 are smaller than the thicknesses d11 and d21 of the first piezoelectric film 211. This makes it possible to suppress imbalance in displacement due to thickness shear vibration, and to further suppress unwanted waves. Note that, as in Figure 2, the thicknesses d11 and d21 of the first piezoelectric film 211 and the thicknesses d12 and d22 of the second piezoelectric film 212 may be equal. Even in this case, it is possible to suppress imbalance in displacement due to thickness shear vibration, and to further suppress unwanted waves. Furthermore, the thicknesses d12 and d22 of the second piezoelectric film 212 may be larger than the thicknesses d11 and d21 of the first piezoelectric film 211.

[0057] In the second embodiment, the thickness d4 of the fourth piezoelectric portion 24 is preferably equal to the thickness d3 of the third piezoelectric portion 23. This improves the symmetry of the piezoelectric stack 20A in the Z0 direction, and further suppresses imbalances in displacement between the piezoelectric portions, thereby further suppressing unwanted waves.

[0058] 3 , the piezoelectric device 1A is a piezoelectric device that utilizes a thickness-extensional vibration mode. The displacement direction TL1 of the thickness-extensional vibration of the first piezoelectric portion 21 and the displacement direction TL3 of the thickness-extensional vibration of the third piezoelectric portion 23 are opposite directions, the displacement direction TL3 of the thickness-extensional vibration of the third piezoelectric portion 23 are opposite directions, and the displacement direction TL4 of the thickness-extensional vibration of the fourth piezoelectric portion 24 are opposite directions, and the displacement direction TL4 of the thickness-extensional vibration of the fourth piezoelectric portion 24 is opposite directions, and the displacement direction TL2 of the thickness-extensional vibration of the second piezoelectric portion 22 are opposite directions. Therefore, the displacement directions TL1 and TL4 of the thickness-extensional vibration are the same direction and correspond to the displacement direction of the first thickness-extensional vibration, and the displacement directions TL3 and TL2 of the thickness-extensional vibration are different directions from the first thickness-extensional vibration and correspond to the displacement direction of the second thickness-extensional vibration.

[0059] The displacement direction TS12 of the thickness shear vibration of the second piezoelectric film 212 of the first piezoelectric portion 21 and the displacement direction TS3 of the thickness shear vibration of the third piezoelectric portion 23 are the same direction, the displacement direction TS3 of the thickness shear vibration of the third piezoelectric portion 23 and the displacement direction TS4 of the thickness shear vibration of the fourth piezoelectric portion 24 are opposite directions, and the displacement direction TS4 of the thickness shear vibration of the fourth piezoelectric portion 24 and the displacement direction TS22 of the thickness shear vibration of the second piezoelectric film 222 of the second piezoelectric portion 22 are the same direction. Note that, as in the first embodiment, the displacement direction TS11 of the thickness shear vibration of the first piezoelectric film 211 and the displacement direction TS12 of the thickness shear vibration of the second piezoelectric film 212 are opposite directions, and the displacement direction TS21 of the thickness shear vibration of the first piezoelectric film 221 and the displacement direction TS22 of the thickness shear vibration of the second piezoelectric film 222 are opposite directions. Therefore, the displacement directions TS11, TS4, and TS22 of the thickness-shear vibrations are the same direction and correspond to the displacement direction of the first thickness-shear vibration. Furthermore, the displacement directions TS12, TS3, and TS21 of the thickness-shear vibrations are different from the displacement direction of the first thickness-shear vibration and correspond to the displacement direction of the second thickness-shear vibration.

[0060] In the following description, the piezoelectric portion or the piezoelectric film has a displacement direction of the second thickness longitudinal vibration and a displacement direction of the first thickness shear vibration. ３ or LiTaO ３ ) Euler angles are (φ ２１ , θ ２１ , ψ ２１ )

[0061] Here, similarly to the first embodiment, it is preferable that the piezoelectric portion or the piezoelectric film having the displacement direction of the second thickness longitudinal vibration and the displacement direction of the first thickness shear vibration is a rotated Y-cut. That is, the first component φ of the Euler angle of the piezoelectric portion or the piezoelectric film described above is １１ , φ １２ , φ ２２ Similarly, the first component φ of the Euler angle of the piezoelectric part or the piezoelectric film ２１ is preferably between −3° and +3°. ２１ It is more preferable that the angle is 0°. This can improve the resonance characteristics.

[0062] When the piezoelectric laminate 20A is made of a single crystal of lithium niobate, θ １１ is preferably 123° or more and 129° or less, or 303° or more and 309° or less, and is preferably 126° or 306°. １１ If is in this range, θ １１ -3°≦θ １２ ≦θ １１ +3° is preferable, and θ １２ = θ １１ It is more preferable that θ １１ and θ １２ If is in this range, θ １１ +177°≦θ ２１ ≦θ １１ +183° and θ １１ +177°≦θ ２２ ≦θ １１ Preferably, θ is +183°. ２１ = θ ２２ = θ １１ It is more preferable that the angle is +180°. １１ , θ １２ , θ ２１ and θ ２２ If is in this range, ψ １１ can be any value, and ψ １２ , ψ ２１ and ψ ２２ is ψ １１ +177°≦ψ １２ ≦ψ １１ +183°, ψ １１ +177°≦ψ ２１ ≦ψ １１ +183° and ψ １１ -3°≦ψ ２２ ≦ψ １１ It is preferable that the angle satisfies +3°, and ψ １１ = ψ １２ +180°=ψ ２１ +180°=ψ ２２ As a result, the displacement direction of the first thickness-extensional vibration is opposite to the displacement direction of the second thickness-extensional vibration, so that unwanted waves of the thickness-extensional vibration can be suppressed, and the displacement direction of the first thickness-shear vibration is opposite to the displacement direction of the second thickness-shear vibration, so that unwanted waves of the thickness-shear vibration can be suppressed.

[0063] As described above, in the piezoelectric device 1A according to the second embodiment, the piezoelectric stack 20A has multiple central piezoelectric portions (the third piezoelectric portion 23 and the fourth piezoelectric portion 24), which can improve the strength of the piezoelectric stack 20A.

[0064] In a preferred embodiment, the displacement direction of the second mode (thickness shear vibration) of one of the two central piezoelectric portions adjacent to each other in the first direction is different from the displacement direction of the second mode (thickness shear vibration) of the other central piezoelectric portion, thereby suppressing the generation of unwanted waves.

[0065] In a more preferred embodiment, the displacement direction of the second mode (thickness shear vibration) of one of the two central piezoelectric portions adjacent to each other in the first direction is opposite to the displacement direction of the second mode (thickness shear vibration) of the other central piezoelectric portion, thereby further suppressing the generation of unwanted waves.

[0066] In a preferred embodiment, the first piezoelectric portion 21 has a plurality of piezoelectric films. The displacement direction of the second mode (thickness shear vibration) of the piezoelectric film (second piezoelectric film 212) closest to the central piezoelectric portion of the first piezoelectric portion 21 is the same as the displacement direction of the second mode (thickness shear vibration) of the central piezoelectric portion (third piezoelectric portion 23) closest to the first piezoelectric portion 21. This can further suppress imbalance in the second mode (thickness shear vibration) displacement of the first piezoelectric portion 21 due to the upper electrode 31 or imbalance in the second mode (thickness shear vibration) displacement of the second piezoelectric portion 22 due to the lower electrode 32, thereby further suppressing unwanted waves.

[0067] In a preferred embodiment, the second piezoelectric portion 22 includes a plurality of piezoelectric films. The displacement direction of the second mode (thickness shear vibration) of the piezoelectric film (second piezoelectric film 222) closest to the central piezoelectric portion of the second piezoelectric portion 22 is the same as the displacement direction of the second mode (thickness shear vibration) of the central piezoelectric portion (third piezoelectric portion 23) closest to the second piezoelectric portion 22. This can further suppress imbalance in the second mode (thickness shear vibration) of the first piezoelectric portion 21 due to the upper electrode 31 or imbalance in the second mode (thickness shear vibration) of the second piezoelectric portion 22 due to the lower electrode 32, thereby further suppressing unwanted waves. This improves the vertical symmetry of the piezoelectric stack 20, thereby achieving good resonance characteristics.

[0068] The thicknesses of the plurality of central piezoelectric portions are all equal, which improves the symmetry of the piezoelectric stack 20 from top to bottom, thereby achieving good resonance characteristics.

[0069] In a more preferable embodiment, the piezoelectric device 1 according to the first embodiment is a piezoelectric device that utilizes a thickness-extensional vibration mode. The first mode is thickness-extensional vibration, and the second mode is thickness-shear vibration. The plurality of piezoelectric portions and the plurality of piezoelectric films have a first thickness-extensional vibration displacement direction or a second thickness-extensional vibration displacement direction that is a direction different from the first thickness-extensional vibration displacement direction as a displacement direction of the thickness-extensional vibration. The plurality of piezoelectric portions and the plurality of piezoelectric films have a first thickness-extensional vibration displacement direction or a second thickness-extensional vibration displacement direction that is a direction different from the first thickness-extensional vibration displacement direction as a displacement direction of the thickness-extensional vibration. The Euler angles of lithium niobate of the piezoelectric portions or piezoelectric films having the first thickness-extensional vibration displacement direction and the first thickness-extensional vibration displacement direction are (φ １１ , θ １１ , ψ １１ ), then φ １１ is between -3° and 3°, and θ １１ is 123° or more and 129° or less or 303° or more and 309° or less, and ψ １１ is an arbitrary value. The Euler angles of the lithium niobate of the piezoelectric portion or piezoelectric film having the displacement direction of the first thickness longitudinal vibration and the displacement direction of the second thickness shear vibration are defined as (φ １２ , θ １２ , ψ １２), then φ １２ is between -3° and 3°, and θ １１ -3°≦θ １２ ≦θ １１ +3° is satisfied, ψ １１ +177°≦ψ １２ ≦ψ １１ +183°. The Euler angles of the lithium niobate of the piezoelectric portion or the piezoelectric film having the displacement direction of the second thickness longitudinal vibration and the displacement direction of the first thickness shear vibration are (φ ２１ , θ ２１ , ψ ２１ ), then φ ２１ is between -3° and 3°, and θ １１ +177°≦θ ２１ ≦θ １１ +183°, and ψ １１ +177°≦ψ ２１ ≦ψ １１ +183°. The Euler angles of the lithium niobate of the piezoelectric portion or the piezoelectric film having the displacement direction of the second thickness longitudinal vibration and the displacement direction of the second thickness shear vibration are (φ ２２ , θ ２２ , ψ ２２ ), then φ ２２ is between -3° and 3°, and θ １１ +177°≦θ ２２ ≦θ １１ +183°, and ψ １１ -3°≦ψ ２２ ≦ψ １１ This satisfies +3°. This makes it possible to suppress imbalances in the displacement of the thickness-extensional vibration and the thickness-shear vibration of the first piezoelectric portion 21 caused by the upper electrode 31, and in the displacement of the thickness-extensional vibration and the thickness-shear vibration of the second piezoelectric portion 22 caused by the lower electrode 32, thereby further suppressing unwanted waves.

[0070] Third Embodiment Fig. 4 is a schematic cross-sectional view of a piezoelectric device according to a third embodiment. Like Fig. 2, Fig. 4 is a cross-sectional view taken along line II-II in Fig. 1. As shown in Fig. 4, the piezoelectric device 1B according to the third embodiment differs from the piezoelectric device 1 according to the first embodiment in that it further includes a fourth piezoelectric portion 24 and a fifth piezoelectric portion 25 located between the third piezoelectric portion 23 and the second piezoelectric portion 22. That is, the piezoelectric stack 20B of the piezoelectric device 1B according to the third embodiment has the third piezoelectric portion 23, the fourth piezoelectric portion 24, and the fifth piezoelectric portion 25 as multiple central piezoelectric portions.

[0071] In the third embodiment, the piezoelectric laminate 20B includes a first piezoelectric portion 21, a second piezoelectric portion 22, a third piezoelectric portion 23, a fourth piezoelectric portion 24, and a fifth piezoelectric portion 25 as piezoelectric portions. The first piezoelectric portion 21, the second piezoelectric portion 22, the third piezoelectric portion 23, the fourth piezoelectric portion 24, and the fifth piezoelectric portion 25 are stacked in the Z0 direction to form a laminate. In the third embodiment, the first piezoelectric portion 21 and the second piezoelectric portion 22 are laminates having multiple piezoelectric films, and the third piezoelectric portion 23, the fourth piezoelectric portion 24, and the fifth piezoelectric portion are single layers. The fourth piezoelectric portion 24 and the fifth piezoelectric portion 25 are piezoelectric portions located between the first piezoelectric portion 21 and the second piezoelectric portion 22. In the example of FIG. 4 , the fourth piezoelectric portion 24 is located between the third piezoelectric portion 23 and the fifth piezoelectric portion 25, and the fifth piezoelectric portion 25 is located between the fourth piezoelectric portion 24 and the second piezoelectric portion 22. That is, the third piezoelectric portion 23, the fourth piezoelectric portion 24, and the fifth piezoelectric portion 25 are an example of a "central piezoelectric portion" in the present disclosure. In the example of Fig. 4, the laminate is formed by laminating the first piezoelectric portion 21, the third piezoelectric portion 23, the fourth piezoelectric portion 24, the fifth piezoelectric portion 25, and the second piezoelectric portion 22 in this order. This improves the mechanical strength and voltage resistance of the piezoelectric laminate 20.

[0072] In the example of Figure 4, the thicknesses d12 and d22 of the second piezoelectric film 212 are smaller than the thicknesses d11 and d21 of the first piezoelectric film 211. This makes it possible to suppress imbalance in displacement in the second mode (thickness shear vibration), and to further suppress unwanted waves. Note that, as in Figure 2, the thicknesses d11 and d21 of the first piezoelectric film 211 and the thicknesses d12 and d22 of the second piezoelectric film 212 may be equal. Even in this case, it is possible to suppress imbalance in displacement in the second mode (thickness shear vibration), and to further suppress unwanted waves. Furthermore, the thicknesses d12 and d22 of the second piezoelectric film 212 may be larger than the thicknesses d11 and d21 of the first piezoelectric film 211.

[0073] In the third embodiment, it is preferable that the thickness d5 of the fifth piezoelectric portion 25 and the thickness d4 of the fourth piezoelectric portion 24 are equal to the thickness d3 of the third piezoelectric portion 23. This improves the symmetry of the piezoelectric stack 20B in the Z0 direction, and further suppresses imbalances in displacement between the piezoelectric portions, thereby further suppressing unwanted waves.

[0074] 4 , the piezoelectric device 1B is a piezoelectric device that utilizes a thickness-extensional vibration mode. The displacement direction TL1 of the thickness-extensional vibration of the first piezoelectric portion 21 and the displacement direction TL3 of the thickness-extensional vibration of the third piezoelectric portion 23 are opposite directions. The displacement direction TL3 of the thickness-extensional vibration of the third piezoelectric portion 23 and the displacement direction TL4 of the thickness-extensional vibration of the fourth piezoelectric portion 24 are opposite directions. The displacement direction TL4 of the thickness-extensional vibration of the fourth piezoelectric portion 24 and the displacement direction TL5 of the thickness-extensional vibration of the fifth piezoelectric portion 25 are opposite directions. The displacement direction TL5 of the thickness-extensional vibration of the fifth piezoelectric portion 25 and the displacement direction TL2 of the thickness-extensional vibration of the second piezoelectric portion 22 are opposite directions. Therefore, the displacement directions TL1, TL4, and TL2 of the thickness-extensional vibration are the same direction and correspond to the displacement direction of the first thickness-extensional vibration. The displacement directions TL3 and TL5 of the thickness-extensional vibration are different directions from the first thickness-extensional vibration and correspond to the displacement direction of the second thickness-extensional vibration.

[0075] The displacement direction TS12 of the thickness shear vibration of the second piezoelectric film 212 of the first piezoelectric portion 21 and the displacement direction TS3 of the thickness shear vibration of the third piezoelectric portion 23 are in the same direction, the displacement direction TS3 of the thickness shear vibration of the third piezoelectric portion 23 and the displacement direction TS4 of the thickness shear vibration of the fourth piezoelectric portion 24 are in opposite directions, the displacement direction TS4 of the thickness shear vibration of the fourth piezoelectric portion 24 and the displacement direction TS5 of the thickness shear vibration of the fifth piezoelectric portion 25 are in opposite directions, and the displacement direction TS5 of the thickness shear vibration of the fifth piezoelectric portion 25 and the displacement direction TS22 of the thickness shear vibration of the second piezoelectric film 222 of the second piezoelectric portion 22 are in the same direction. As in the first embodiment, the displacement direction TS11 of the thickness-shear vibration of the first piezoelectric film 211 and the displacement direction TS12 of the thickness-shear vibration of the second piezoelectric film 212 are opposite directions, and the displacement direction TS21 of the thickness-shear vibration of the first piezoelectric film 221 and the displacement direction TS22 of the thickness-shear vibration of the second piezoelectric film 222 are opposite directions. Therefore, the thickness-shear vibration displacement directions TS11, TS4, and TS21 are in the same direction and correspond to the displacement direction of the first thickness-shear vibration. Furthermore, the thickness-shear vibration displacement directions TS12, TS3, TS5, and TS22 are in a direction different from the displacement direction of the first thickness-shear vibration and correspond to the displacement direction of the second thickness-shear vibration.

[0076] The piezoelectric devices 1, 1A, and 1B according to the first to third embodiments have been described above, but the piezoelectric devices according to the present disclosure are not limited to these and may also be those according to the modified examples shown below.

[0077] (First Modification) Fig. 5 is a schematic cross-sectional view of a piezoelectric device according to a first modification. Like Fig. 2, Fig. 5 is a cross-sectional view taken along line II-II in Fig. 1. As shown in Fig. 5, the piezoelectric device 1C according to the second embodiment differs from the piezoelectric device 1 according to the first embodiment in that a third piezoelectric film 213 is provided between the second piezoelectric film 212 of the first piezoelectric portion 21 and the third piezoelectric portion 23. That is, in the piezoelectric stack 20C of the piezoelectric device 1C according to the first modification, the first piezoelectric portion 21 further includes a third piezoelectric film 213.

[0078] The third piezoelectric film 213 is a very thin film, 1 nm or less, compared to the first piezoelectric film 211 and the second piezoelectric film 212. The displacement direction TL13 of the thickness longitudinal vibration of the third piezoelectric film 213 is the same as the displacement directions TL11, TL12 of the thickness longitudinal vibration of the first piezoelectric film 211 and the second piezoelectric film 212. The displacement direction TS13 of the thickness shear vibration of the third piezoelectric film 213 is different from the displacement directions TS11, TS12 of the thickness shear vibration of the first piezoelectric film 211 and the second piezoelectric film 212.

[0079] When a very thin third piezoelectric film 213 is included between the second piezoelectric film 212 and the third piezoelectric portion 23, as in the first modification, the third piezoelectric film 213 has only a slight effect on the resonance characteristics of the piezoelectric device 1C. Therefore, the piezoelectric device 1C according to the first modification can also suppress unwanted waves. Note that the first modification can be combined with other embodiments or modifications.

[0080] In the above description, the number of central piezoelectric portions is one to three, but the number of central piezoelectric portions may be four or more. Even when the number of central piezoelectric portions is four or more, by setting the displacement direction of the first mode (thickness longitudinal vibration) and the displacement direction of the second mode (thickness shear vibration) of the piezoelectric portions or piezoelectric films to the same as above, it is possible to suppress unwanted waves in the first mode (thickness longitudinal vibration) and the second mode (thickness shear vibration).

[0081] Here, when the first piezoelectric portion and the second piezoelectric portion are both made of the first piezoelectric film and the second piezoelectric film, and the number of central piezoelectric portions is odd, the Euler angle (φ １１ , θ １１ , ψ １１ ), (φ １２ , θ １２ , ψ １２ ), (φ ２２ , θ ２２ , ψ ２２ ) preferably satisfies the condition according to the first embodiment. In addition, when the first piezoelectric portion and the second piezoelectric portion are both made of the first piezoelectric film and the second piezoelectric film, and when the number of central piezoelectric portions is even, the Euler angle (φ １１ , θ １１ , ψ １１ ), (φ １２ , θ１２ , ψ １２ ), (φ ２１ , θ ２１ , ψ ２１ ), (φ ２２ , θ ２２ , ψ ２２ ) preferably satisfies the conditions according to the second embodiment. This makes it possible to suppress imbalance between the displacement of the first mode (thickness longitudinal vibration) and the displacement of the second mode (thickness shear vibration) of the first piezoelectric portion 21 caused by the upper electrode 31, and between the displacement of the first mode (thickness longitudinal vibration) and the displacement of the second mode (thickness shear vibration) of the second piezoelectric portion 22 caused by the lower electrode 32, thereby suppressing unwanted waves.

[0082] For example, when the direction of a crystal axis is expressed as an Euler angle, the direction of the crystal axis includes directions in which the x'''-axis direction, y'''-axis direction, and z'''-axis direction relative to the x-axis direction are the same, although notation may differ. For example, when l, m, and n are any integers, the direction of a crystal whose Euler angles are (α + 360° × l, β + 360° × m, γ + 360° × n) is the same direction as the direction of a crystal whose Euler angles are (α, β, γ).

[0083] For example, when the direction of a crystal axis is expressed as an Euler angle, the direction includes directions in which the x''' axis, y''' axis, and z''' axis directions are the same relative to the a-axis direction of the crystal, although the notation is different. ３ , LiNbO ３ The crystal of LiTaO according to the present disclosure is trigonal. ３ , LiNbO ３ There are three a-axis directions in the crystal. Here, the angle between each a-axis direction when viewed from the c-axis direction is 120°. Therefore, for example, when k is an arbitrary integer, the direction of the crystal where the Euler angles are (α + 120° × k, β, γ) is the same direction as the direction of the crystal where the Euler angles are (α, β, γ). Here, α, β, and γ are arbitrary.

[0084] Examples and comparative examples will be described below.

[0085] Example 1-1 The piezoelectric device according to Example 1-1 is the piezoelectric device 1 according to the first embodiment. In Example 1-1, the piezoelectric laminate 20 is a rotated Y-cut LiNbO ３ Three piezoelectric layers (first piezoelectric layer 21, second piezoelectric layer 22, third piezoelectric layer 23) made of single crystals of LiNbO were laminated in the order of first piezoelectric layer 21, third piezoelectric layer 23, and second piezoelectric layer 22, and both the first piezoelectric layer 21 and the second piezoelectric layer 22 were layers made of first piezoelectric films 211, 221 and second piezoelectric films 212, 222 laminated together. The functional electrodes were platinum (Pt) electrodes with a thickness of 100 nm. Table 1 shows the design of the piezoelectric laminate according to Example 1-1. The thicknesses of the piezoelectric layers and the piezoelectric layers and the LiNbO ３ The Euler angles were as shown in Table 1. With the above settings, a simulation was performed on the piezoelectric device according to Example 1-1 to determine the resonance characteristics.

[0086]

[0087] Comparative Example 1-1 FIG. 6 is a schematic cross-sectional view of a piezoelectric device according to Comparative Example 1-1. Like FIG. 2, FIG. 6 is a view corresponding to the cross-sectional view taken along II-II in FIG. 1. Table 2 is a table showing the design of a piezoelectric laminate 20X according to Comparative Example 1-1. As shown in FIG. 6 and Table 2, a piezoelectric device 1X according to Comparative Example 1-2 was simulated to determine its resonance characteristics in the same manner as Example 1-1, except that the first piezoelectric portion 21 and the second piezoelectric portion 22 were single layers rather than layers including multiple piezoelectric films, and the thicknesses of the piezoelectric portions were equal.

[0088]

[0089] Comparative Example 1-2 Fig. 7 is a schematic cross-sectional view of a piezoelectric device according to Comparative Example 1-2. Like Fig. 2, Fig. 7 is a view corresponding to the cross-sectional view taken along II-II in Fig. 1. Table 3 is a table showing the design of a piezoelectric laminate 20Y according to Comparative Example 1-2. As shown in Fig. 7 and Table 3, a simulation was performed to determine the resonance characteristics of the piezoelectric device 1Y according to Comparative Example 1-2 in the same manner as in Example 1-1, except that the first piezoelectric portion 21 and the second piezoelectric portion 22 were single layers rather than layers including multiple piezoelectric films.

[0090]

[0091] Example 2-1 The piezoelectric device according to Example 2-1 is the piezoelectric device 1A according to the second embodiment. In Example 2-1, the piezoelectric laminate 20A is a rotated Y-cut LiNbO ３ Four piezoelectric layers (first piezoelectric layer 21, second piezoelectric layer 22, third piezoelectric layer 23, fourth piezoelectric layer 24) each made of a single crystal of LiNbO were laminated in the order of first piezoelectric layer 21, third piezoelectric layer 23, fourth piezoelectric layer 24, and second piezoelectric layer 22, and both the first piezoelectric layer 21 and the second piezoelectric layer 22 were layers made of first piezoelectric films 211, 221 and second piezoelectric films 212, 222 laminated together. The functional electrodes were platinum (Pt) electrodes with a thickness of 100 nm. Table 4 shows the design of the piezoelectric laminate according to Example 2-1. The thicknesses of the piezoelectric layers and the piezoelectric layers and the thickness of the LiNbO ３ The Euler angles were as shown in Table 4. With the above settings, a simulation was performed on the piezoelectric device according to Example 2-1 to determine the resonance characteristics.

[0092]

[0093] Comparative Example 2-1 FIG. 8 is a schematic cross-sectional view of a piezoelectric device according to Comparative Example 2-1. Like FIG. 2, FIG. 8 is a view corresponding to the cross-sectional view taken along II-II in FIG. 1. Table 5 is a table showing the design of a piezoelectric laminate 20AX according to Comparative Example 2-1. As shown in FIG. 8 and Table 5, a piezoelectric device 1AX according to Comparative Example 2-2 was simulated to determine its resonance characteristics in the same manner as Example 2-1, except that the first piezoelectric portion 21 and the second piezoelectric portion 22 were single layers rather than layers including multiple piezoelectric films, and the thicknesses of the piezoelectric portions were equal.

[0094]

[0095] Comparative Example 2-2 FIG. 9 is a schematic cross-sectional view of a piezoelectric device according to Comparative Example 2-2. Like FIG. 2, FIG. 9 is a view corresponding to the cross-sectional view taken along II-II in FIG. 1. Table 6 is a table showing the design of a piezoelectric laminate 20AY according to Comparative Example 2-2. As shown in FIG. 9 and Table 6, a simulation was performed to determine the resonance characteristics of the piezoelectric device 1AY according to Comparative Example 2-2 in the same manner as in Example 2-1, except that the first piezoelectric portion 21 and the second piezoelectric portion 22 were single layers rather than layers including multiple piezoelectric films.

[0096]

[0097] Example 3-1 The piezoelectric device according to Example 3-1 is the piezoelectric device 1B according to the third embodiment. In Example 3-1, the piezoelectric laminate 20B is a rotated Y-cut LiNbO ３ Five piezoelectric sections (first piezoelectric section 21, second piezoelectric section 22, third piezoelectric section 23, fourth piezoelectric section 24, fifth piezoelectric section 25) made of single crystals of LiNbO were laminated in the order of first piezoelectric section 21, third piezoelectric section 23, fourth piezoelectric section 24, fifth piezoelectric section 25, and second piezoelectric section 22, and both the first piezoelectric section 21 and the second piezoelectric section 22 were layers formed by laminating first piezoelectric films 211, 221 and second piezoelectric films 212, 222. The functional electrodes were platinum (Pt) electrodes with a thickness of 100 nm. Table 7 shows the design of the piezoelectric laminate according to Example 3-1. The thicknesses of the piezoelectric sections and piezoelectric films and the thickness of the LiNbO ３ The Euler angles were as shown in Table 7. With the above settings, a simulation was performed on the piezoelectric device according to Example 3-1 to determine the resonance characteristics.

[0098]

[0099] Comparative Example 3-1 FIG. 10 is a schematic cross-sectional view of a piezoelectric device according to Comparative Example 3-1. Like FIG. 2, FIG. 10 is a view corresponding to the cross-sectional view taken along II-II in FIG. 1. Table 8 is a table showing the design of a piezoelectric laminate 20BX according to Comparative Example 3-1. As shown in FIG. 10 and Table 8, a piezoelectric device 1BX according to Comparative Example 3-2 was simulated to determine its resonance characteristics in the same manner as Example 3-1, except that the first piezoelectric portion 21 and the second piezoelectric portion 22 were single layers rather than layers including multiple piezoelectric films, and the thicknesses of the piezoelectric portions were equal.

[0100]

[0101] Comparative Example 3-2 FIG. 11 is a schematic cross-sectional view of a piezoelectric device according to Comparative Example 3-2. Like FIG. 2, FIG. 11 is a view corresponding to the cross-sectional view taken along II-II in FIG. 1. Table 9 is a table showing the design of a piezoelectric laminate 20BY according to Comparative Example 3-2. As shown in FIG. 11 and Table 9, a simulation was performed to determine the resonance characteristics of the piezoelectric device 1BY according to Comparative Example 3-2 in the same manner as in Example 3-1, except that the first piezoelectric portion 21 and the second piezoelectric portion 22 were single layers rather than layers including multiple piezoelectric films.

[0102]

[0103] Fig. 12 is a diagram showing the resonance characteristics of the piezoelectric device according to Example 1-1, Fig. 13 is a diagram showing the resonance characteristics of the piezoelectric device according to Comparative Example 1-1, and Fig. 14 is a diagram showing the resonance characteristics of the piezoelectric device according to Comparative Example 1-2.

[0104] 12 and 13, the unwanted thickness-extensional vibration waves S1 did not appear in Example 1-1, whereas the unwanted thickness-extensional vibration waves S1 appeared in Comparative Example 1-1. Therefore, it can be seen that the unwanted thickness-extensional vibration waves S1 can be suppressed by making the first and second piezoelectric portions thinner than the intermediate piezoelectric portion (third piezoelectric portion).

[0105] 12 to 14, the unwanted thickness-shear vibration waves S2 did not appear in Example 1-1, whereas the unwanted thickness-shear vibration waves S2 appeared in Comparative Examples 1-1 and 1-2. Therefore, it can be seen that the unwanted thickness-shear vibration waves S2 can be suppressed by providing the first piezoelectric part and the second piezoelectric part with multiple piezoelectric films having different thickness-shear vibration displacement directions.

[0106] Fig. 15 is a diagram showing the resonance characteristics of the piezoelectric device according to Example 2-1, Fig. 16 is a diagram showing the resonance characteristics of the piezoelectric device according to Comparative Example 2-1, and Fig. 17 is a diagram showing the resonance characteristics of the piezoelectric device according to Comparative Example 2-2.

[0107] 15 and 16, the unwanted thickness-extensional vibration waves S1 did not appear in Example 2-1 and Comparative Example 2-2, whereas the unwanted thickness-extensional vibration waves S1 appeared in Comparative Example 2-1. Therefore, it can be seen that the unwanted thickness-extensional vibration waves S1 can be suppressed by making the first and second piezoelectric portions thinner than the intermediate piezoelectric portions (the third and fourth piezoelectric portions).

[0108] 15 to 17, the unwanted thickness-shear vibration waves S2 did not appear in Example 2-1, whereas the unwanted thickness-shear vibration waves S2 appeared in Comparative Examples 2-1 and 2-2. Therefore, it can be seen that the unwanted thickness-shear vibration waves S2 can be suppressed by providing the first piezoelectric part and the second piezoelectric part with multiple piezoelectric films having different thickness-shear vibration displacement directions.

[0109] Fig. 18 is a diagram showing the resonance characteristics of the piezoelectric device according to Example 3-1, Fig. 19 is a diagram showing the resonance characteristics of the piezoelectric device according to Comparative Example 3-1, and Fig. 20 is a diagram showing the resonance characteristics of the piezoelectric device according to Comparative Example 3-2.

[0110] 18 and 19, the unwanted thickness-extensional vibration waves S1 did not appear in Example 3-1 and Comparative Example 3-2, whereas the unwanted thickness-extensional vibration waves S1 appeared in Comparative Example 3-1. Therefore, it can be seen that the unwanted thickness-extensional vibration waves S1 can be suppressed by making the first and second piezoelectric portions thinner than the intermediate piezoelectric portions (the third and fourth piezoelectric portions and the fifth example).

[0111] 18 to 20, the unwanted thickness-shear vibration waves S2 did not appear in Example 3-1, whereas the unwanted thickness-shear vibration waves S2 appeared in Comparative Examples 3-1 and 3-2. Therefore, it can be seen that the unwanted thickness-shear vibration waves S2 can be suppressed by providing the first piezoelectric part and the second piezoelectric part with multiple piezoelectric films having different thickness-shear vibration displacement directions.

[0112] The above-described embodiments are provided to facilitate understanding of the present invention and are not intended to limit the present invention. The present invention may be modified or improved without departing from the spirit and scope of the present invention, and equivalents thereof are also included in the present invention.

[0113] For example, in the above embodiments and modifications, a piezoelectric device in which the first mode is thickness-extensional vibration and the second mode is thickness-shear vibration has been described, but this is not limited thereto, and the first mode may be thickness-shear vibration and the second mode may be thickness-extensional vibration. Below, as a second modification, a piezoelectric device in which the first mode is thickness-shear vibration and the second mode is thickness-extensional vibration will be described.

[0114] (Second Modification) FIG. 21 is a schematic cross-sectional view of a piezoelectric device according to a second modification. Like FIG. 2, FIG. 21 is a cross-sectional view taken along line II-II in FIG. 1. In the second modification, the first mode is thickness-shear vibration, and the second mode is thickness-extensional vibration. In the second modification, a piezoelectric portion refers to a portion of the piezoelectric stack 20 that includes a piezoelectric body and in which the displacement direction of the thickness-extensional vibration is continuously the same. In other words, in the second modification, one piezoelectric portion does not include a portion in which the displacement direction of the thickness-extensional vibration is different. In the second modification, a piezoelectric film refers to a film that includes a piezoelectric body and in which the displacement direction of the thickness-extensional vibration and the displacement direction of the thickness-extensional vibration are continuously the same. In other words, in the second modification, one piezoelectric film does not include a portion in which the displacement direction of the thickness-extensional vibration or the displacement direction of the thickness-extensional vibration is different.

[0115] (Displacement of Thickness Shear Vibration) Of two piezoelectric portions included in the plurality of piezoelectric portions and adjacent to each other in the Z0 direction, the displacement direction of the thickness shear vibration of one piezoelectric portion is different from the displacement direction of the thickness shear vibration of the other piezoelectric portion. Of two piezoelectric portions included in the plurality of piezoelectric portions and adjacent to each other in the Z0 direction, the displacement direction of the thickness shear vibration of one piezoelectric portion is preferably opposite to the displacement direction of the thickness shear vibration of the other piezoelectric portion. The displacement direction TS1 of the thickness shear vibration of the first piezoelectric portion 21 and the displacement direction TS3 of the thickness shear vibration of the third piezoelectric portion 23 are opposite directions, and the displacement direction TS3 of the thickness shear vibration of the third piezoelectric portion 23 and the displacement direction TS2 of the thickness shear vibration of the second piezoelectric portion 22 are opposite directions. Here, the displacement direction TS1 of the thickness shear vibration of the first piezoelectric portion 21 refers to the displacement directions TS11 and TS12 of the thickness shear vibration of the piezoelectric films (first piezoelectric film 211 and second piezoelectric film 212) included in the first piezoelectric portion 21. Similarly, the displacement direction TS2 of the thickness shear vibration of the second piezoelectric part 22 refers to the displacement directions TS21, TS22 of the thickness shear vibration of the piezoelectric films (first piezoelectric film 221 and second piezoelectric film 222) included in the second piezoelectric part 22.

[0116] In the second modification, the piezoelectric stack 20 has a first thickness-shear vibration displacement direction or a second thickness-shear vibration displacement direction. In other words, in the piezoelectric stack 20 according to the second modification, piezoelectric portions having a first thickness-shear vibration displacement direction and piezoelectric portions having a second thickness-shear vibration displacement direction are alternately stacked. In the example of FIG. 21 , the thickness-shear vibration displacement direction TS1 and the thickness-shear vibration displacement direction TS2 are the same and correspond to the first thickness-shear vibration displacement direction. Also, in the example of FIG. 21 , the thickness-shear vibration displacement direction TS3 is different from the thickness-shear vibration displacement directions TS1 and TS2 and corresponds to the second thickness-shear vibration displacement direction. In the example of FIG. 21 , the first thickness-shear vibration displacement direction and the second thickness-shear vibration displacement direction are opposite to each other. In the example of Figure 21, the displacement direction of the first thickness shear vibration is the X0 direction, and the displacement direction of the second thickness shear vibration is the opposite direction to the X0 direction, but this is just one example and is not limited to this.For example, the displacement direction of the first thickness shear vibration may be the opposite direction to the X0 direction, and the displacement direction of the second thickness shear vibration may be the X0 direction, or the displacement directions of the first thickness shear vibration and the second thickness shear vibration may be directions perpendicular to the Z0 direction and intersect with the X0 direction.

[0117] (Displacement of Thickness-Extended Vibration) Of two piezoelectric films included in a plurality of piezoelectric films and adjacent to each other in the Z0 direction, the displacement direction of the thickness-extensional vibration of one piezoelectric film is different from the displacement direction of the thickness-extensional vibration of the other piezoelectric film. Of two piezoelectric films included in a plurality of piezoelectric films and adjacent to each other in the Z0 direction, the displacement direction of the thickness-extensional vibration of one piezoelectric film is preferably opposite to the displacement direction of the thickness-extensional vibration of the other piezoelectric film. The displacement direction TL11 of the thickness-extensional vibration of the first piezoelectric film 211 and the displacement direction TL12 of the thickness-extensional vibration of the second piezoelectric film 212 are opposite directions, and the displacement direction TL21 of the thickness-extensional vibration of the first piezoelectric film 221 and the displacement direction TL22 of the thickness-extensional vibration of the second piezoelectric film 222 are opposite directions.

[0118] It is preferable that the displacement directions of the thickness longitudinal vibration of the piezoelectric film on the central piezoelectric portion side among the plurality of piezoelectric films are the same as the displacement directions of the thickness longitudinal vibration of the central piezoelectric portion adjacent in the Z0 direction to the piezoelectric film on the central piezoelectric portion side. The displacement directions TL12 and TL22 of the thickness longitudinal vibration of the second piezoelectric films 212 and 222 and the displacement direction TL3 of the thickness longitudinal vibration of the third piezoelectric portion 23 are the same direction.

[0119] In the second modification, the piezoelectric laminate 20 has a displacement direction of the first thickness-longitudinal vibration or a displacement direction of the second thickness-longitudinal vibration. In the example of FIG. 21 , the displacement direction TL11 of the thickness-longitudinal vibration and the displacement direction TL21 of the thickness-longitudinal vibration are the same and correspond to the displacement direction of the first thickness-longitudinal vibration. Also, in the example of FIG. 21 , the displacement directions TL12, TL22, and TL3 of the thickness-longitudinal vibration are different from the displacement directions TL11 and TL21 of the thickness-longitudinal vibration and correspond to the displacement direction of the second thickness-longitudinal vibration. In the example of FIG. 21 , the displacement direction of the first thickness-longitudinal vibration and the displacement direction of the second thickness-longitudinal vibration are opposite directions. Note that in the example of FIG. 21 , the displacement direction of the first thickness-longitudinal vibration is upward and the displacement direction of the second thickness-longitudinal vibration is downward. However, this is merely an example and is not limited thereto. For example, the displacement direction of the first thickness-longitudinal vibration may be downward and the displacement direction of the second thickness-longitudinal vibration may be upward.

[0120] As described above, the piezoelectric device 1 according to the second modification includes a piezoelectric stack 20 having a thickness in a first direction (Z0 direction) and having an upper surface 20a that is a surface on one side in the first direction and a lower surface 20b that is a surface on the other side in the first direction, a support member 10 provided on the lower surface 20b side of the piezoelectric stack 20, an upper electrode 31 provided on the upper surface 20a side of the piezoelectric stack 20, and a lower electrode 32 provided on the lower surface 20b side of the piezoelectric stack 20. The piezoelectric stack 20 has a plurality of piezoelectric portions. The plurality of piezoelectric portions include a first piezoelectric portion 21 that is the piezoelectric portion closest to the upper electrode 31, a second piezoelectric portion 22 that is the piezoelectric portion closest to the lower electrode 32, and one or more central piezoelectric portions that are piezoelectric portions located between the first piezoelectric portion 21 and the second piezoelectric portion 22. Of two piezoelectric parts included in the plurality of piezoelectric parts and adjacent to each other in the first direction, the displacement direction of the first mode (thickness-shear vibration) of one piezoelectric part is different from the displacement direction of the first mode (thickness-shear vibration) of the other piezoelectric part. At least one of the first piezoelectric part 21 and the second piezoelectric part 22 has a plurality of piezoelectric films having the same displacement direction of the first mode (thickness-shear vibration). Of two piezoelectric films included in the plurality of piezoelectric films and adjacent to each other in the first direction, the displacement direction of the second mode (thickness-longitudinal vibration) of one piezoelectric film is different from the displacement direction of the second mode (thickness-longitudinal vibration) of the other piezoelectric film. This makes it possible to suppress imbalance in the displacement of the second mode (thickness-longitudinal vibration) of the first piezoelectric part 21 due to the upper electrode 31 or imbalance in the displacement of the second mode (thickness-longitudinal vibration) of the second piezoelectric part 22 due to the lower electrode 32, thereby suppressing unwanted waves.

[0121] The present disclosure may also have the following configurations.

[0122] (1) A piezoelectric laminate having a thickness in a first direction and having an upper surface that is a surface on one side in the first direction and a lower surface that is a surface on the other side in the first direction; a support member provided on the lower surface side of the piezoelectric laminate; an upper electrode provided on the upper surface side of the piezoelectric laminate; and a lower electrode provided on the lower surface side of the piezoelectric laminate, wherein the piezoelectric laminate has a plurality of piezoelectric parts, the plurality of piezoelectric parts including a first piezoelectric part that is the piezoelectric part closest to the upper electrode, a second piezoelectric part that is the piezoelectric part closest to the lower electrode, and one or more central piezoelectric parts that are piezoelectric parts between the first piezoelectric part and the second piezoelectric part, wherein the plurality of piezoelectric parts include two piezoelectric parts that are adjacent to each other in the first direction, and the displacement direction of a first mode of one piezoelectric part is different from the displacement direction of the first mode of the other piezoelectric part, and at least one of the first piezoelectric part and the second piezoelectric part has a plurality of piezoelectric films having the same displacement direction of the first mode, (2) The piezoelectric device according to (1), wherein, of two piezoelectric films included in the plurality of piezoelectric films and adjacent to each other in the first direction, the displacement direction of the second mode of one piezoelectric film is different from the displacement direction of the second mode of the other piezoelectric film. (2) The piezoelectric device according to (1), wherein the thickness of the first piezoelectric portion is smaller than the thickness of the central piezoelectric portion, and the thickness of the second piezoelectric portion is smaller than the thickness of the central piezoelectric portion. (3) The piezoelectric device according to (1) or (2), wherein, of two piezoelectric films included in the plurality of piezoelectric films and adjacent to each other in the first direction, the thickness of one piezoelectric film closer to the central piezoelectric portion is equal to or smaller than the thickness of the other piezoelectric film. (4) The piezoelectric device according to any one of (1) to (3), wherein, of two piezoelectric films included in the plurality of piezoelectric portions and adjacent to each other in the first direction, the displacement direction of the first mode of one piezoelectric portion is opposite to the displacement direction of the first mode of the other piezoelectric portion. (5) The piezoelectric device according to any one of (1) to (4), wherein the displacement direction of the second mode of one of the piezoelectric films included in the plurality of piezoelectric films and adjacent to each other in the first direction is opposite to the displacement direction of the second mode of the other piezoelectric film. (6) The piezoelectric device according to any one of (1) to (5), wherein the thickness of the first piezoelectric portion is equal to the thickness of the second piezoelectric portion.(7) The piezoelectric device according to any one of (1) to (6), wherein both the first piezoelectric portion and the second piezoelectric portion have the plurality of piezoelectric films. (8) The piezoelectric device according to (7), wherein the plurality of piezoelectric films of each of the first piezoelectric portion and the second piezoelectric portion consist of a first piezoelectric film and a second piezoelectric film adjacent to the first piezoelectric film on the side of the central piezoelectric portion in the first direction. (9) The piezoelectric device according to (8), wherein the thickness of the first piezoelectric film of the first piezoelectric portion is equal to the thickness of the first piezoelectric film of the second piezoelectric portion, and the thickness of the second piezoelectric film of the first piezoelectric portion is equal to the thickness of the second piezoelectric film of the second piezoelectric portion. (10) The piezoelectric device according to any one of (1) to (9), wherein the piezoelectric stack has one central piezoelectric portion. (11) The piezoelectric device according to (10), wherein the second mode displacement direction of the piezoelectric film closest to the central piezoelectric portion among the plurality of piezoelectric films is the same as the second mode displacement direction of the central piezoelectric portion. (12) The piezoelectric device according to any one of (1) to (9), wherein the piezoelectric stack has a plurality of the central piezoelectric portions. (13) The piezoelectric device according to (12), wherein, of two central piezoelectric portions included in the plurality of central piezoelectric portions and adjacent to each other in the first direction, the second mode displacement direction of one central piezoelectric portion is a direction different from the second mode displacement direction of the other central piezoelectric portion. (14) The piezoelectric device according to (13), wherein, of two central piezoelectric portions included in the plurality of central piezoelectric portions and adjacent to each other in the first direction, the second mode displacement direction of one central piezoelectric portion is a direction opposite to the second mode displacement direction of the other central piezoelectric portion. (15) The piezoelectric device according to any one of (12) to (14), wherein the first piezoelectric portion has the plurality of piezoelectric films, and the second mode displacement direction of the piezoelectric film closest to the central piezoelectric portion among the plurality of piezoelectric films of the first piezoelectric portion is the same as the second mode displacement direction of the central piezoelectric portion closest to the first piezoelectric portion. (16) The piezoelectric device according to any one of (12) to (15), wherein the second piezoelectric portion has the plurality of piezoelectric films, and the second mode displacement direction of the piezoelectric film closest to the central piezoelectric portion among the plurality of piezoelectric films of the second piezoelectric portion is the same as the second mode displacement direction of the central piezoelectric portion closest to the second piezoelectric portion.(17) The piezoelectric device according to any one of (12) to (16), wherein the thicknesses of the plurality of central piezoelectric portions are all equal. (18) The piezoelectric device according to any one of (1) to (17), wherein the piezoelectric stack is made of a single crystal of lithium niobate or lithium tantalate. (19) The piezoelectric device according to (18), wherein the piezoelectric stack is made of a rotated Y-cut single crystal of lithium niobate or lithium tantalate. (20) A piezoelectric device utilizing a thickness-extensional vibration mode, wherein the first mode is thickness-extensional vibration and the second mode is thickness-shear vibration, the plurality of piezoelectric portions and the plurality of piezoelectric films have a first thickness-extensional vibration displacement direction or a second thickness-extensional vibration displacement direction that is a direction different from the first thickness-extensional vibration displacement direction as a displacement direction of the thickness-extensional vibration, the plurality of piezoelectric portions and the plurality of piezoelectric films have a first thickness-extensional vibration displacement direction or a second thickness-extensional vibration displacement direction that is a direction different from the first thickness-extensional vibration displacement direction as a displacement direction of the thickness-extensional vibration, and the Euler angle of lithium niobate of the piezoelectric portions or piezoelectric films having the first thickness-extensional vibration displacement direction and the first thickness-extensional vibration displacement direction is (φ. １１ , θ １１ , ψ １１ ), then φ １１ is between -3° and 3°, and θ １１ is 123° or more and 129° or less or 303° or more and 309° or less, and ψ １１ is an arbitrary value, and the Euler angle of the lithium niobate of the piezoelectric portion or piezoelectric film having the displacement direction of the first thickness longitudinal vibration and the displacement direction of the second thickness shear vibration is (φ １２ , θ １２ , ψ １２ ), then φ １２ is between -3° and 3°, and θ １１ -3°≦θ １２ ≦θ １１ +3° is satisfied, ψ １１ +177°≦ψ １２ ≦ψ １１+183°, and the Euler angles of the lithium niobate of the piezoelectric portion or piezoelectric film having the displacement direction of the second thickness longitudinal vibration and the displacement direction of the second thickness shear vibration are (φ ２２ , θ ２２ , ψ ２２ ), then φ ２２ is between -3° and 3°, and θ １１ +177°≦θ ２２ ≦θ １１ +183°, and ψ １１ -3°≦ψ ２２ ≦ψ １１ (21) A piezoelectric device according to (19), which uses a thickness-extensional vibration mode, wherein the first mode is thickness-extensional vibration and the second mode is thickness-shear vibration, the plurality of piezoelectric portions and the plurality of piezoelectric films have a first thickness-extensional vibration displacement direction or a second thickness-extensional vibration displacement direction that is a direction different from the first thickness-extensional vibration displacement direction as a displacement direction of the thickness-extensional vibration, the plurality of piezoelectric portions and the plurality of piezoelectric films have a first thickness-extensional vibration displacement direction or a second thickness-extensional vibration displacement direction that is a direction different from the first thickness-extensional vibration displacement direction as a displacement direction of the thickness-extensional vibration, and the Euler angles of lithium niobate of the piezoelectric portions or piezoelectric films having the first thickness-extensional vibration displacement direction and the first thickness-extensional vibration displacement direction are defined as (φ １１ , θ １１ , ψ １１ ), then φ １１ is between -3° and 3°, and θ １１ is 123° or more and 129° or less or 303° or more and 309° or less, and ψ １１ is an arbitrary value, and the Euler angle of the lithium niobate of the piezoelectric portion or piezoelectric film having the displacement direction of the first thickness longitudinal vibration and the displacement direction of the second thickness shear vibration is (φ １２ , θ １２ , ψ １２ ), then φ １２ is between -3° and 3°, and θ １１ -3°≦θ １２ ≦θ １１ +3° is satisfied, ψ １１ +177°≦ψ １２ ≦ψ１１ +183°, and the Euler angles of the lithium niobate of the piezoelectric portion or piezoelectric film having the displacement direction of the second thickness longitudinal vibration and the displacement direction of the first thickness shear vibration are (φ ２１ , θ ２１ , ψ ２１ ), then φ ２１ is between -3° and 3°, and θ １１ +177°≦θ ２１ ≦θ １１ +183°, and ψ １１ +177°≦ψ ２１ ≦ψ １１ +183°, and the Euler angles of the lithium niobate of the piezoelectric portion or piezoelectric film having the displacement direction of the second thickness longitudinal vibration and the displacement direction of the second thickness shear vibration are (φ ２２ , θ ２２ , ψ ２２ ), then φ ２２ is between -3° and 3°, and θ １１ +177°≦θ ２２ ≦θ １１ +183°, and ψ １１ -3°≦ψ ２２ ≦ψ １１ (22) The piezoelectric device according to any one of (1) to (19), wherein the first mode is thickness-extensional vibration and the second mode is thickness-shear vibration. (23) The piezoelectric device according to any one of (1) to (19), wherein the first mode is thickness-shear vibration and the second mode is thickness-extensional vibration.

[0123] 1, 1A, 1B, 1C, 1X, 1Y, 1AX, 1AY, 1BX, 1BY Piezoelectric device 10 Support member 11 Support substrate 12 Intermediate layer 13 Space portion 20, 20A, 20B, 20C, 20X, 20Y, 20AX, 20AY, 20BX, 20BY Piezoelectric laminate 20a Upper surface 20b Lower surface 21 First piezoelectric portion 22 Second piezoelectric portion 23 Third piezoelectric portion 24 Fourth piezoelectric portion 25 Fifth piezoelectric portion 211, 221 First piezoelectric film 212, 222 Second piezoelectric film 213 Third piezoelectric film 31 Upper electrode 32 Lower electrode 31a, 32a Main electrode portion 31b, 32b Extension portion C Excitation region d1 to d5, d11, d12, d21, d22 Thickness TL1 to TL5, TL11 to TL13, TL21, TL22 Displacement direction of thickness longitudinal vibration TS3 to TS5, TS11 to TS13, TS21, TS22 Displacement direction of thickness shear vibration

Claims

1. A piezoelectric laminate having a thickness in a first direction and having an upper surface which is a surface on one side in the first direction and a lower surface which is a surface on the other side in the first direction; a support member provided on the lower surface side of the piezoelectric laminate; an upper electrode provided on the upper surface side of the piezoelectric laminate; and a lower electrode provided on the lower surface side of the piezoelectric laminate, wherein the piezoelectric laminate has a plurality of piezoelectric parts, the plurality of piezoelectric parts including a first piezoelectric part which is the piezoelectric part closest to the upper electrode, a second piezoelectric part which is the piezoelectric part closest to the lower electrode, and one or more central piezoelectric parts which are piezoelectric parts between the first piezoelectric part and the second piezoelectric part, wherein the first mode displacement direction of one of two piezoelectric parts which are adjacent to each other in the first direction is different from the first mode displacement direction of the other piezoelectric part, and at least one of the first piezoelectric part and the second piezoelectric part has a plurality of piezoelectric films whose first mode displacement direction is the same, A piezoelectric device, wherein the displacement direction of the second mode of one of two piezoelectric films included in the plurality of piezoelectric films and adjacent to each other in the first direction is different from the displacement direction of the second mode of the other piezoelectric film.

2. The piezoelectric device according to claim 1, wherein the thickness of the first piezoelectric portion is smaller than the thickness of the central piezoelectric portion, and the thickness of the second piezoelectric portion is smaller than the thickness of the central piezoelectric portion.

3. A piezoelectric device as described in claim 1 or 2, wherein, of two piezoelectric films included in the plurality of piezoelectric films and adjacent to each other in the first direction, the thickness of one piezoelectric film located on the central piezoelectric portion side is equal to or less than the thickness of the other piezoelectric film.

4. A piezoelectric device according to any one of claims 1 to 3, wherein, of two piezoelectric sections included in the plurality of piezoelectric sections and adjacent to each other in the first direction, the displacement direction of the first mode of one piezoelectric section is opposite to the displacement direction of the first mode of the other piezoelectric section.

5. A piezoelectric device described in any one of claims 1 to 4, wherein, of two piezoelectric films included in the plurality of piezoelectric films and adjacent to each other in the first direction, the displacement direction of the second mode of one piezoelectric film is opposite to the displacement direction of the second mode of the other piezoelectric film.

6. A piezoelectric device according to any one of claims 1 to 5, wherein the thickness of the first piezoelectric portion is equal to the thickness of the second piezoelectric portion.

7. A piezoelectric device according to any one of claims 1 to 6, wherein both the first piezoelectric portion and the second piezoelectric portion have the plurality of piezoelectric films.

8. A piezoelectric device as described in claim 7, wherein the plurality of piezoelectric films each of the first piezoelectric portion and the second piezoelectric portion comprises a first piezoelectric film and a second piezoelectric film adjacent to the first piezoelectric film on the central piezoelectric portion side in the first direction.

9. A piezoelectric device as described in claim 8, wherein the thickness of the first piezoelectric film of the first piezoelectric portion is equal to the thickness of the first piezoelectric film of the second piezoelectric portion, and the thickness of the second piezoelectric film of the first piezoelectric portion is equal to the thickness of the second piezoelectric film of the second piezoelectric portion.

10. A piezoelectric device according to any one of claims 1 to 9, wherein the piezoelectric stack has one central piezoelectric portion.

11. The piezoelectric device according to claim 10, wherein the second mode displacement direction of the piezoelectric film closest to the central piezoelectric portion among the plurality of piezoelectric films is the same as the second mode displacement direction of the central piezoelectric portion.

12. The piezoelectric device according to any one of claims 1 to 9, wherein the piezoelectric stack has a plurality of the central piezoelectric portions.

13. A piezoelectric device as described in claim 12, wherein, of two central piezoelectric portions included in the plurality of central piezoelectric portions and adjacent to each other in the first direction, the second mode displacement direction of one central piezoelectric portion is different from the second mode displacement direction of the other central piezoelectric portion.

14. A piezoelectric device as described in claim 13, wherein, of two central piezoelectric portions included in the plurality of central piezoelectric portions and adjacent to each other in the first direction, the displacement direction of the second mode of one central piezoelectric portion is opposite to the displacement direction of the second mode of the other central piezoelectric portion.

15. A piezoelectric device as described in any one of claims 12 to 14, wherein the first piezoelectric portion has the plurality of piezoelectric films, and the second mode displacement direction of the piezoelectric film closest to the central piezoelectric portion among the plurality of piezoelectric films of the first piezoelectric portion is the same as the second mode displacement direction of the central piezoelectric portion closest to the first piezoelectric portion.

16. A piezoelectric device as described in any one of claims 12 to 15, wherein the second piezoelectric portion has the plurality of piezoelectric films, and the second mode displacement direction of the piezoelectric film closest to the central piezoelectric portion among the plurality of piezoelectric films of the second piezoelectric portion is the same as the second mode displacement direction of the central piezoelectric portion closest to the second piezoelectric portion.

17. The piezoelectric device according to any one of claims 12 to 16, wherein the thicknesses of the plurality of central piezoelectric portions are all equal.

18. A piezoelectric device according to any one of claims 1 to 17, wherein the piezoelectric laminate is made of a single crystal of lithium niobate or lithium tantalate.

19. The piezoelectric device of claim 18, wherein the piezoelectric stack is made of rotated Y-cut lithium niobate or lithium tantalate single crystal.

20. A piezoelectric device utilizing a thickness-extensional vibration mode, wherein the first mode is thickness-extensional vibration and the second mode is thickness-shear vibration, the plurality of piezoelectric portions and the plurality of piezoelectric films have a first thickness-extensional vibration displacement direction or a second thickness-extensional vibration displacement direction that is a direction different from the first thickness-extensional vibration displacement direction as a displacement direction of the thickness-extensional vibration, the plurality of piezoelectric portions and the plurality of piezoelectric films have a first thickness-extensional vibration displacement direction or a second thickness-extensional vibration displacement direction that is a direction different from the first thickness-extensional vibration displacement direction as a displacement direction of the thickness-extensional vibration, and the Euler angles of lithium niobate of the piezoelectric portions or piezoelectric films having the first thickness-extensional vibration displacement direction and the first thickness-extensional vibration displacement direction are (φ １１ , θ １１ , ψ １１ ), then φ １１ is between -3° and 3°, and θ １１ is 123° or more and 129° or less or 303° or more and 309° or less, and ψ １１ is an arbitrary value, and the Euler angle of the lithium niobate of the piezoelectric portion or piezoelectric film having the displacement direction of the first thickness longitudinal vibration and the displacement direction of the second thickness shear vibration is (φ １２ , θ １２ , ψ １２ ), then φ １２ is between -3° and 3°, and θ １１ -3°≦θ １２ ≦θ １１ +3° is satisfied, and ψ １１ +177°≦ψ １２ ≦ψ １１ +183°, and the Euler angles of the lithium niobate of the piezoelectric portion or piezoelectric film having the displacement direction of the second thickness longitudinal vibration and the displacement direction of the second thickness shear vibration are (φ ２２ , θ ２２ , ψ ２２ ), then φ ２２ is between -3° and 3°, and θ １１ +177°≦θ ２２ ≦θ １１ +183°, and ψ １１ -3°≦ψ ２２ ≦ψ １１ The piezoelectric device of claim 19, wherein the angle satisfies +3°.

21. A piezoelectric device utilizing a thickness-extensional vibration mode, wherein the first mode is thickness-extensional vibration and the second mode is thickness-shear vibration, the plurality of piezoelectric portions and the plurality of piezoelectric films have a first thickness-extensional vibration displacement direction or a second thickness-extensional vibration displacement direction that is a direction different from the first thickness-extensional vibration displacement direction as a displacement direction of the thickness-extensional vibration, the plurality of piezoelectric portions and the plurality of piezoelectric films have a first thickness-extensional vibration displacement direction or a second thickness-extensional vibration displacement direction that is a direction different from the first thickness-extensional vibration displacement direction as a displacement direction of the thickness-extensional vibration, and the Euler angles of lithium niobate of the piezoelectric portions or piezoelectric films having the first thickness-extensional vibration displacement direction and the first thickness-extensional vibration displacement direction are defined as (φ １１ , θ １１ , ψ １１ ), then φ １１ is between -3° and 3°, and θ １１ is 123° or more and 129° or less or 303° or more and 309° or less, and ψ １１ is an arbitrary value, and the Euler angle of the lithium niobate of the piezoelectric portion or piezoelectric film having the displacement direction of the first thickness longitudinal vibration and the displacement direction of the second thickness shear vibration is (φ １２ , θ １２ , ψ １２ ), then φ １２ is between -3° and 3°, and θ １１ -3°≦θ １２ ≦θ １１ +3° is satisfied, and ψ １１ +177°≦ψ １２ ≦ψ １１ +183°, and the Euler angles of the lithium niobate of the piezoelectric portion or piezoelectric film having the displacement direction of the second thickness longitudinal vibration and the displacement direction of the first thickness shear vibration are (φ ２１ , θ ２１ , ψ ２１ ), then φ ２１ is between -3° and 3°, and θ １１ +177°≦θ ２１ ≦θ １１ +183°, and ψ １１ +177°≦ψ ２１ ≦ψ １１ +183°, and the Euler angles of the lithium niobate of the piezoelectric portion or piezoelectric film having the displacement direction of the second thickness longitudinal vibration and the displacement direction of the second thickness shear vibration are (φ ２２ , θ ２２ , ψ ２２ ), then φ ２２ is between -3° and 3°, and θ １１ +177°≦θ ２２ ≦θ １１ +183°, and ψ １１ -3°≦ψ ２２ ≦ψ １１ The piezoelectric device of claim 19, wherein the angle satisfies +3°.

22. A piezoelectric device according to any one of claims 1 to 19, wherein the first mode is thickness extensional vibration and the second mode is thickness shear vibration.

23. A piezoelectric device according to any one of claims 1 to 19, wherein the first mode is thickness-shear vibration and the second mode is thickness-extension vibration.

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