Elastic wave device

Abstract

Provided is an elastic wave device capable of sufficiently suppressing spurious even when a piezoelectric body having anisotropy is used. An elastic wave device (1) includes a piezoelectric body (2), a first electrode (3) provided on a first main surface (2a) of the piezoelectric body, a second electrode (4) provided on a second main surface (2b), an acoustic reflection portion having an air gap (G), and a mass additional film (6) provided on at least one of the first electrode (3) or the second electrode (4) and outside the first electrode (3) or the second electrode (4), wherein, in a plan view, a region in which the first electrode and at least one of the mass additional film overlap each other with the second electrode has a first region and a second region surrounding the first region, and, with respect to the mass additional film (6), in the second region, a structure of mass additional film portions (6b, 6d) on both sides of a first direction (A) in a plane of the piezoelectric body is different from a structure of mass additional film portions (6a, 6c) on both sides of a second direction (B).

Description

TECHNICAL FIELD

[0001] The present application relates to an elastic wave device having a configuration in which electrodes are layered on both main surfaces of a piezoelectric body. BACKGROUND

[0002] Conventionally, various elastic wave devices utilizing bulk waves propagating in a piezoelectric body are known. For example, in the elastic wave device described in Patent Document 1, a configuration is disclosed in which a layered body including a lower electrode, a piezoelectric body, and an upper electrode is layered on an air gap and an acoustic reflector. In Patent Document 1, a structure is disclosed in which, in order to suppress spurious, the thickness of the upper electrode on a central first region that generates a main resonance is made thinner than the thickness of the upper electrode in a second region that surrounds the first region, or conversely, the thickness of the upper electrode on the central first region that generates a main resonance is made thicker than the thickness of the upper electrode in the second region that surrounds the first region.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT DOCUMENT

[0005] Patent Document 1: Japanese Patent Application Publication No. 2005-159402 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] In an elastic wave device like that described in Patent Document 1, in the case where a piezoelectric body having anisotropy in a direction parallel to the main surface of the piezoelectric body is used as the piezoelectric body, sometimes spurious cannot be sufficiently suppressed.

[0008] An object of the present application is to provide an elastic wave device that can sufficiently suppress spurious even in the case where a piezoelectric body having anisotropy in a plane parallel to a first main surface and a second main surface is used.

[0009] TECHNICAL SOLUTION FOR SOLVING THE PROBLEM

[0010] The first invention of this application relates to an elastic wave device comprising: a piezoelectric body having a first main surface and a second main surface facing each other, and having anisotropy in a plane parallel to the first main surface and the second main surface; a first electrode disposed on the first main surface of the piezoelectric body; a second electrode disposed on the second main surface of the piezoelectric body and facing the first electrode across the piezoelectric body; an acoustic reflection portion disposed on the surface of the second electrode opposite to the piezoelectric body; and a mass-adding membrane disposed on at least one of the first electrode and the second electrode. At least one of the first electrode or the second electrode and the outer side of the first electrode or the second electrode, when viewed from above, the area where the first electrode and at least one of the mass-added films overlap with the second electrode includes a first region and a second region surrounding the first region. Regarding the mass-added film, in the second region, the structure of the mass-added film portions on both sides of the plane of the piezoelectric body in a first direction is different from the structure of the mass-added film portions on both sides of the plane of the piezoelectric body in a second direction, where the second direction is different from the first direction.

[0011] The second invention relates to an elastic wave device comprising: a piezoelectric body having a first main surface and a second main surface facing each other, and having anisotropy in a plane parallel to the first main surface and the second main surface; a first electrode disposed on the first main surface of the piezoelectric body; a second electrode disposed on the second main surface of the piezoelectric body, facing the first electrode across the piezoelectric body; and an acoustic reflection portion disposed on the surface of the second electrode opposite to the piezoelectric body, wherein the excitation region facing the first electrode and the second electrode has a first region and an area surrounding the first electrode. The second region of the first region is described above. In the second region, the thickness of at least one of the first electrode and the second electrode is thinner than that of at least one of the first electrode and the second electrode in the first region. Furthermore, in the second region, the structure of at least one of the first electrode and the second electrode on both sides of the plane of the piezoelectric body in a first direction is different from the structure of at least one of the first electrode and the second electrode on both sides of the plane of the piezoelectric body in a second direction, where the second direction is different from the first direction.

[0012] Hereinafter, the first invention and the second invention will be collectively referred to as the present invention.

[0013] Invention Effects

[0014] According to the first and second inventions of this application, even when a piezoelectric material with anisotropy in a plane parallel to the first and second main surfaces is used as a piezoelectric material, stray emissions can be sufficiently suppressed. Attached Figure Description

[0015] Figure 1 (a) is a top view of the elastic wave device according to the first embodiment of the present invention. Figure 1 (b) and Figure 1 (c) are respectively along Figure 1 A cross-sectional view of line II and line II-II in (a).

[0016] Figure 2 This is a schematic front sectional view used to illustrate the construction of a two-dimensional model of an elastic wave device without a mass-added membrane.

[0017] Figure 3 (a) is shown in Figure 2 The diagram shows the resonance characteristics of the elastic wave device without a mass-added membrane in the first direction A. Figure 3 (b) is a diagram showing the resonance characteristics of an elastic wave device without a frame-like portion in the second direction B.

[0018] Figure 4 This is a schematic front sectional view showing the structure of a two-dimensional model of an elastic wave device with a frame-shaped section.

[0019] Figure 5 (a) is shown in Figure 4 The diagram shows the resonance characteristics of the two-dimensional model of the elastic wave device, in which the optimal frame structure is set in the first direction A. Figure 5 (b) is a diagram showing the resonant characteristics of a structure in which the optimal frame portion in the second direction B is provided in the first direction A.

[0020] Figure 6 (a) is shown in Figure 4 The diagram shows the resonance characteristics of a two-dimensional model of an elastic wave device, in which the optimal frame-like structure in the first direction A is set in the second direction B. Figure 6 (b) is a diagram showing the resonant characteristics of a structure with the optimal frame portion set in the second direction B.

[0021] Figure 7 It is a perspective view used to illustrate the construction of a three-dimensional model of an elastic wave device without a frame.

[0022] Figure 8 It shows that it was used Figure 7 The diagram shows the resonance characteristics of the structure without a frame in the case of the three-dimensional model shown.

[0023] Figure 9 (a) is a perspective view of a model illustrating the three-dimensional structure of an elastic wave device with a frame-like section. Figure 9(b) is a diagram showing the resonance characteristics when a three-dimensional model with the frame-shaped part is used.

[0024] Figure 10 (a) is a schematic top view illustrating an elastic wave device with a frame-like portion perpendicular to the 130° direction having a width of 1.6 μm and a frame-like portion perpendicular to the 40° direction having a width of 3.1 μm. Figure 10 (b) is a diagram showing the resonant characteristics of an elastic wave device with an optimal frame portion in the second direction B provided in the first direction A and an optimal frame portion in the first direction A provided in the second direction B.

[0025] Figure 11 (a) shows in Figure 7 The diagram shows the resonance characteristics of a three-dimensional model of an elastic wave device with optimal frame-like sections in both the first direction A and the second direction B. Figure 11 (b) is a diagram showing the resonant characteristics of an elastic wave device with an optimal frame-shaped portion of the second direction B provided in both the first direction A and the second direction B.

[0026] Figure 12 (a) is a top view of the elastic wave device according to the second embodiment of the present invention. Figure 12 (b) is the front sectional view of the elastic wave device. Figure 12 (c) is the right sectional view.

[0027] Figure 13 (a) is a top view of the elastic wave device according to the third embodiment of the present invention. Figure 13 (b) is along Figure 13 A cross-sectional view of the VV line in (a).

[0028] Figure 14 (a) and Figure 14 (b) is a front sectional view and a right sectional view of the elastic wave device according to the fourth embodiment of the present invention.

[0029] Figure 15 (a) and Figure 15 (b) is a front sectional view and a right sectional view of the elastic wave device according to the fifth embodiment of the present invention.

[0030] Figure 16 (a)~ Figure 16 (c) is a partially cut front sectional view used to illustrate various modified examples in which an insulating film is provided in the frame-shaped recess constituting the second region.

[0031] Figure 17 (a) and Figure 17(b) is a top view and a front sectional view used to illustrate the elastic wave device according to the sixth embodiment.

[0032] Figure 18 This is a partially cut front sectional view used to illustrate the elastic wave device according to the seventh embodiment of the present invention.

[0033] Figure 19 (a) and Figure 19 (b) are the main sectional views of the elastic wave device used to illustrate the modified examples of the frame section.

[0034] Figure 20 This is a front sectional view used to illustrate the elastic wave device according to the eighth embodiment of the present invention.

[0035] Figure 21 (a)~ Figure 21 (d) are schematic top views illustrating variations of the planar shape of the frame section.

[0036] Figure 22 (a) and Figure 22 (b) is a schematic top view used to illustrate another variation of the frame-shaped part.

[0037] Figure 23 This is a circuit diagram of the elastic wave filter according to the ninth embodiment of the present invention. Detailed Implementation

[0038] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings, thereby clarifying the present invention.

[0039] In addition, it should be noted that the embodiments described in this specification are illustrative and that partial substitutions or combinations of structures can be made between different embodiments.

[0040] Figure 1 (a) is a top view of the elastic wave device according to the first embodiment of the present invention. Figure 1 (b) and Figure 1 (c) is along Figure 1 Sectional views of line II and line II-II in (a).

[0041] The elastic wave device 1 has a piezoelectric element 2. The piezoelectric element 2 has a first main surface 2a and a second main surface 2b. The first main surface 2a and the second main surface 2b are opposite to each other.

[0042] The piezoelectric material 2 exhibits anisotropy in a plane parallel to the first principal surface 2a and the second principal surface 2b. This anisotropy refers to the difference in crystallinity between the first direction and the second direction (different from the first direction) within the aforementioned plane, resulting in different propagation characteristics of the elastic waves in the elastic wave device. Examples of such anisotropic materials include single-crystal piezoelectric materials such as LiTaO3 or LiNbO3. In this embodiment, the piezoelectric material 2 comprises LiTaO3.

[0043] A first electrode 3 is disposed on the first main surface 2a of the piezoelectric body 2. A second electrode 4 is disposed on the second main surface 2b. The first electrode 3 and the second electrode 4 are positioned opposite each other across the piezoelectric body 2. The region where the first electrode 3 and the second electrode 4 are positioned opposite each other is the excitation region. By applying an alternating voltage between the first electrode 3 and the second electrode 4, a volume wave is excited as an elastic wave.

[0044] Furthermore, in this case, as a volume wave, various modes of volume waves can be used. For example, by selecting the cutting angle of LiTaO3 or LiNbO3, it is possible to obtain the resonance characteristics of volume waves using thickness shear mode and thickness longitudinal mode.

[0045] A support member 5 is stacked on the second main surface 2b. The support member 5 has an opening 5a. The second electrode 4 is located within this opening 5a. As a result, an air gap G is formed below the second electrode 4. This air gap G is provided as an acoustic reflection part for confining the elastic waves generated in the excitation region of the piezoelectric body 2 within the piezoelectric body 2. Furthermore, due to the provision of the air gap G, vibration in the excitation region is less likely to be hindered.

[0046] The aforementioned support member 5 is made of a suitable material. Examples of such materials include insulators and semiconductors. More specifically, examples include insulators such as bauxite and silicon nitride, and semiconductors such as Si.

[0047] In the elastic wave device 1, a mass-adding film 6 is provided on the upper surface of the first electrode 3. In the elastic wave device 1, when viewed from above, the area where at least one of the first electrode 3 and the mass-adding film 6 overlaps with the second electrode 4 has a first region C1 and a second region surrounding the first region C1. In the elastic wave device 1, the mass-adding film 6 is configured to surround the first region C1. That is, the area surrounded by the frame-like mass-adding film 6 is the first region C1, and the area below the mass-adding film 6 when viewed from above is the second region. In this embodiment, the mass-adding film 6 provided in the second region is integrally formed with the first electrode 3 using the same material. However, the mass-adding film 6 may also be made of a different material than the first electrode 3. Alternatively, the mass-adding film 6 may be provided only in a portion of the second region. That is, the area where the mass-adding film 6 is provided and the second region may not be the same.

[0048] likeFigure 1 As shown in (a), the excitation region has a rectangular shape. The mass-attached membrane 6 is a frame-shaped protrusion having a pair of mass-attached membrane portions 6a and 6c on the long sides and a pair of mass-attached membrane portions 6b and 6d on the short sides. Figure 1 In (a), the direction in which the mass-added membrane portions 6a and 6c extend is designated as the first direction A, and the direction in which the mass-added membrane portions 6b and 6d extend is designated as the second direction B.

[0049] like Figure 1 (a)~ Figure 1 As shown in (c), the widths of the mass-added film portions 6a and 6c extending in the first direction A are different from the widths of the mass-added film portions 6b and 6d extending in the second direction B. That is, the widths of the mass-added film portions 6b and 6d are set to be wider than the widths of the mass-added film portions 6a and 6c. The mass-added film 6 surrounding the first region C1 can also be a segmented shape. That is, in Figure 1 In (a), it is also possible that the four sides of the mass-added membrane portions 6a to 6d are not all connected, and at least one gap is formed in the second region.

[0050] As previously described, the piezoelectric material 2 is anisotropic in a plane parallel to the first principal surface 2a and the second principal surface 2b. When using such an anisotropic piezoelectric material 2, if a frame structure similar to that used in conventional isotropic piezoelectric materials is formed, large stray particles may sometimes appear in the resonance characteristics when a resonator is constructed. In contrast, in the elastic wave device 1, a mass-added membrane 6 is provided in the second region within the aforementioned plane, and the widths of the mass-added membrane portions 6b and 6d are wider than the widths of the mass-added membrane portions 6a and 6c, thus effectively suppressing the aforementioned stray particles. That is, since the widths of the mass-added membrane portions 6b and 6d on both sides in the first direction A and the widths of the mass-added membrane portions 6a and 6c on both sides in the second direction B are different, the effects caused by the anisotropy of the piezoelectric material 2 can be mitigated, thereby suppressing stray particles. (Refer to...) Figures 2-12 To provide a more specific explanation.

[0051] right Figure 2 The characteristics of the two-dimensional model of the elastic wave device 21 were evaluated. Figure 2 In the elastic wave device 21 shown, the measurement conditions are set as follows.

[0052] Piezoelectric material 2: LiTaO3, X-cut with an orientation of ψ = 40°. Here, ψ is defined as the angle relative to the Y-axis, and is set to 40°. In Euler angles, this is equivalent to (90°, 90°, 40°). Thickness = 2 μm.

[0053] Electrode 3 and Electrode 4: are made of Al film with a thickness of 0.2 μm and a planar shape of 50 μm × 50 μm square.

[0054] Imagine the elastic wave device 21 of the above two-dimensional model, and calculate the resonance characteristics in the first direction A without the addition of a mass membrane 6. Figure 3 As can be clearly seen from (a), in this resonant characteristic, there are many large strays between the resonant frequency and the anti-resonant frequency.

[0055] On the other hand, for the second direction B, the resonance characteristics were obtained when no mass-added membranes 6 were placed on either side of the second direction B. The conditions for the two-dimensional model in this case are set as follows.

[0056] Piezoelectric material 2: LiTaO3, orientation ψ = 130°, thickness = 2μm.

[0057] Electrode 3 and Electrode 4: are composed of an Al film with a thickness of 0.2 μm and a planar shape of 50 μm × 50 μm square.

[0058] exist Figure 3 (b) shows the resonance characteristics with respect to the second direction B in the absence of the mass-added membrane 6. It can be seen that in this case, three large stray frequencies also appear between the resonant and anti-resonant frequencies. However, compared... Figure 3 The resonant characteristics of (a) and Figure 3 As can be seen from the resonance characteristics of (b), the stray phenomena appear in very different ways in the first direction A and the second direction B. That is, it can be seen that due to the in-plane anisotropy of the piezoelectric material 2, the characteristics are different depending on the direction in that plane.

[0059] In view of the above circumstances, if Figure 4 As shown, a two-dimensional model is envisioned in which mass-added film portions 6b and 6d are provided on both sides of the first electrode 3 in the first direction A. Here, the premise is set as follows.

[0060] Piezoelectric material 2: LiTaO3, orientation ψ = 40°, thickness = 2μm.

[0061] Electrode 3 and Electrode 4: are composed of an Al film with a thickness of 0.2 μm and a planar shape of 50 μm × 50 μm square.

[0062] The material of the mass-added membrane 6 is A1 membrane, and the thickness of the mass-added membrane portions 6b and 6d is 0.22 μm, and the width is 1.6 μm.

[0063] The resonance characteristics of the above two-dimensional model are shown in... Figure 5(a) This resonance characteristic is obtained by varying the thickness and width of the aforementioned mass-added film portions 6b and 6d to measure the resonance characteristic and determine the optimal resonance characteristic. Figure 5 As shown in (a), in this resonance characteristic, almost no strays are observed between the resonant frequency and the anti-resonant frequency.

[0064] Figure 5 The resonant characteristic of (b) is the characteristic of changing the width of the mass-added film portions 6b and 6d by the structure of the mass-added portion with spurious suppression effect in the first direction A. The thickness of the mass-added film portions 6b and 6d is set to 0.22 μm and the width is set to 3.1 μm.

[0065] like Figure 5 As shown in (b), considerable spurious emissions appear between the resonant frequency and the anti-resonant frequency, and near the resonant frequency. Therefore, it can be concluded that even if the optimal value in the first direction A is applied to the second direction B, there is no spurious emission suppression effect.

[0066] Next, for the following two-dimensional model of the elastic wave device, we seek to optimize the resonance characteristics in the second direction B.

[0067] Piezoelectric material 2: LiTaO3, orientation ψ = 130°, thickness = 2μm.

[0068] Electrode 3 and Electrode 4: are composed of an Al film with a thickness of 0.2 μm and a planar shape of 50 μm × 50 μm square.

[0069] The thickness of the mass-added membrane portions 6b and 6d is 0.22 μm, and the width is 1.6 μm.

[0070] like Figure 6 As shown in (a), in the resonance characteristics of the two-dimensional model with respect to the second direction B, even if the construction of the mass-added membrane portions 6b and 6d, which are the portions of the mass-added membrane 6 on both sides of the first direction A, is optimized, straying occurs between the resonant frequency and the anti-resonant frequency.

[0071] Next, by adjusting the structure of the mass-added membrane portions 6b and 6d on both sides of the first direction A, the conditions for obtaining the optimal resonance characteristics in the second direction B were determined.

[0072] The thickness of the mass-added film portions 6b and 6d is set to 0.22 μm, and the width is set to 3.1 μm. Other settings are set to the same as those obtained. Figure 6 The characteristics of (a) are the same in the two-dimensional model.

[0073] exist Figure 6 In the resonant characteristics shown in (b), no straying occurs between the resonant frequency and the anti-resonant frequency.

[0074] According to the above Figure 5 of (a), Figure 5 (b) and Figure 6 of (a), Figure 6 As can be seen from the results of (b), the structures of the mass-added membrane portions without stray particles differ depending on the first direction A and the second direction B.

[0075] Therefore, based on the research results using the above-mentioned two-dimensional model, the inventors of this application studied the structure of the mass-added membrane portion based on the elastic wave device 31 of the following three-dimensional model.

[0076] like Figure 7 As shown, the three-dimensional model has a first electrode 3 disposed on the upper surface of the piezoelectric body 2. Although in Figure 7 Although not shown in the figure, a second electrode is provided on the second main surface of the piezoelectric body 2, so that it is opposite to the first electrode 3.

[0077] Direction 1 A and direction 2 B are set as Figure 7 The directions shown are as follows. That is, the direction extending along one of the adjacent sides of the first electrode 3 of the square is the first direction A, and the direction extending along the other side is the second direction B. Therefore, similar to the elastic wave device 1, the second direction B is a direction perpendicular to the first direction A.

[0078] Furthermore, in this invention, the angle between the first direction A and the second direction B is not limited to 90°. That is, it is sufficient as long as the second direction B is a different direction relative to the first direction A.

[0079] The conditions for the 3D model are as follows.

[0080] Piezoelectric material 2: LiTaO3, X-cut with the first direction A being ψ = 130°, thickness = 2 μm. First electrode 3 and second electrode 4: composed of an Al film, thickness 0.2 μm, with a planar shape of a 50 μm × 50 μm square. No mass-added film 6.

[0081] The resonance characteristics of the three-dimensional model under the above conditions are shown in... Figure 8 Large stray frequencies appear between the resonant frequency and the anti-resonant frequency.

[0082] Next, as Figure 9As shown in (a), mass-added membrane portions 33a to 33d are provided in the elastic wave device 31 of the above-described three-dimensional model. Here, the mass-added membrane portions 33a to 33d form a rectangular frame. Furthermore, the width of the mass-added membrane portions 33a and 33c extending along the first direction A and located on both sides of the second direction B is set to 1.6 μm. The width of the mass-added membrane portions 33b and 33d extending along the second direction B and located on both sides of the first direction A is also set to 1.6 μm. In addition, the thickness of these mass-added membrane portions 33a to 33d is set to 0.22 μm. The resonance characteristics under this condition are shown in… Figure 9 (b)

[0083] Because of the aforementioned mass-added membrane portions 33a to 33d, thus... Figure 8 Compared to the resonant characteristics shown, the spurious emissions are smaller. However, three additional large spurious emissions appear between the resonant frequency and the anti-resonant frequency.

[0084] Next, in the 3D model, such as Figure 10 As shown in (a), in the three-dimensional model of the elastic wave device 31, the widths of the mass-added membrane portions 33b and 33d on both sides of the first direction A (ψ = 130°) are set to 1.6 μm. Furthermore, the widths of the mass-added membrane portions 33a and 33c perpendicular to the second direction B (ψ = 40°) are set to 3.1 μm. This is equivalent to a configuration where the widths of the mass-added membrane portions 33a and 33c on both sides of the second direction B are optimized for the first direction A, and the widths of the mass-added membrane portions 33b and 33d on both sides of the first direction A are optimized for the second direction B. The resonance characteristics under this condition are shown in... Figure 10 (b) shows that stray emissions still occur between the resonant frequency and the anti-resonant frequency.

[0085] Next, in the aforementioned three-dimensional model, the widths of the mass-added film portions 33b and 33d on both sides of the ψ = 130° direction, i.e., direction A, are set to 3.1 μm, and the widths of the mass-added film portions 33a and 33c on both sides of the ψ = 40° direction, i.e., direction B, are set to 1.6 μm. The resonance characteristics under this condition are shown below. Figure 11 (a)

[0086] according to Figure 11 As can be clearly seen from (a), if the optimal mass-added film portion obtained in the two-dimensional model is formed in each direction, the stray between the resonant frequency and the anti-resonant frequency disappears.

[0087] Furthermore, regarding the aforementioned three-dimensional model, when the widths of all the mass-added membrane portions 33a to 33d are set to be equal at 3.1 μm, it becomes... Figure 11The resonant characteristics shown in (b) are as follows. In terms of the resonant characteristics, large spurious signals still appear near the resonant frequency, and several small spurious signals appear between the resonant frequency and the anti-resonant frequency.

[0088] As described above, it is known that if the structures of the mass-added film portions on both sides of the first direction A and the mass-added film portions on both sides of the second direction B are adjusted according to the propagation conditions of the elastic waves in the first direction A and the second direction B, respectively, stray noise in the resonance characteristics can be sufficiently suppressed. Therefore, in this invention, by making the structures of the mass-added film portions on both sides of the first direction A and the mass-added film portions on both sides of the second direction B in the plane of the piezoelectric body different in the second region, the in-plane anisotropy of the piezoelectric body is compensated, and good resonance characteristics are obtained.

[0089] Alternatively, in this invention, the structures of the mass-added film portions on both sides of the first direction A and the mass-added film portions on both sides of the second direction B in the aforementioned second region may not only be provided on the first electrode 3 side, but also as... Figure 1 (b) and Figure 1 The mass-added film 6 is disposed on the side of the second electrode 4 as shown by the dashed line in (c). Alternatively, it may be disposed only on the side of the second electrode 4, without being disposed on the side of the first electrode 3. That is, the mass-added film 6 may be laminated on at least one of the first electrode 3 and the second electrode 4.

[0090] In addition, Figure 10 Regarding the widths of the mass-added film portions 33a to 33d, the relationship can also be as follows: the width of mass-added film portion 33b < the width of mass-added film portion 33d < the width of mass-added film portion 33a < the width of mass-added film portion 33c. That is, the widths of the mass-added film portions in the same direction can also be different. Similarly, the mass-added film portions in the same direction can also have different shapes. The shapes of the mass-added film portions can also be arranged asymmetrically with respect to the first region.

[0091] Furthermore, the widths of the mass-added film portion 33b and 33d can be opposite, as can the widths of the mass-added film portion 33a and 33c.

[0092] Figure 12 (a) is a top view showing the elastic wave device according to the second embodiment. Figure 12 (b) and Figure 12 (c) are respectively along Figure 12The cross-sectional view along lines III-III and IV-IV in (a). In the elastic wave device 41, the structure of the mass-added membrane 6 differs from that of the elastic wave device 1 in the first embodiment. Regarding other structures, the elastic wave device 41 is the same as the elastic wave device 1.

[0093] In the elastic wave device 41, the mass-adding membrane 6 is made of the same material as the first electrode 3. Alternatively, the mass-adding membrane 6 can be made of a different material than the first electrode 3. Suitable metals or alloys, or insulators, can be used as such different materials.

[0094] In the mass-added membrane 6, the heights of the mass-added membrane portions 6b and 6d on the short sides located on both sides in the first direction A are higher than the heights of the mass-added membrane portions 6a and 6c on both sides in the second direction B. In this way, the structure can be different by making the heights of the mass-added membrane portions 6b and 6d on the short sides and the mass-added membrane portions 6a and 6c on the long sides different on both sides in the first direction A and on both sides in the second direction B. In this case, similar to the elastic wave device 1 of the first embodiment, stray noise in the resonance characteristics can be effectively suppressed.

[0095] Furthermore, in the first embodiment, the width of the mass-attached film portion varies depending on the direction; in the second embodiment, the height of the mass-attached film portion varies depending on the direction. However, it is also possible to have different materials for the mass-attached film portion instead of different widths and heights. That is, the materials of the mass-attached film portions 6b and 6d on the shorter sides of the mass-attached film portions on both sides of the first direction A can be different from the materials of the mass-attached film portions 6a and 6c on the longer sides of the mass-attached film portions on both sides of the second direction B. Moreover, as a way to make the above-mentioned structures different, two or more of the width, thickness, and material of the mass-attached film portion can be different. That is, it is possible to configure the mass-attached film portions on both sides of the first direction A and the mass-attached film portions on both sides of the second direction B to have at least one different width, thickness, and material.

[0096] Figure 13 (a) is a top view of the elastic wave device according to the third embodiment. Figure 13 (b) is along Figure 13 A cross-sectional view of the VV line in (a).

[0097] In the elastic wave device 51, when viewed from above, the height of the corner portion 6e becomes higher than the other portions of the mass-adding membrane 6. That is, the height of the corner portion 6e is higher than the heights of the mass-adding membrane portions 6a and 6c on the long side and the mass-adding membrane portions 6b and 6d on the short side, which are sandwiched by the corner portion 6e. In addition, in this case, the width of the mass-adding membrane portions 6b and 6d on the short side is also set to be wider than the width of the mass-adding membrane portions 6a and 6c on the long side. Therefore, similar to the elastic wave device 1 of the first embodiment, stray noise that appears in the resonance characteristics can be effectively suppressed.

[0098] Figure 14 (a) and Figure 14 (b) is a front sectional view and a side sectional view of the elastic wave device according to the fourth embodiment of the present invention.

[0099] In the elastic wave device 61, a first electrode 3 is provided on the first main surface 2a of the piezoelectric body 2, and a second electrode 4 is provided on the second main surface 2b. Both the first electrode 3 and the second electrode 4 have a rectangular shape when viewed from above. Furthermore, the thickness of the first electrode 3 decreases in the second region, which is configured to surround the first region. That is, when viewed from above, the rectangular frame-like portion around the first region is recessed. Therefore, compared with… Figure 14 (a) and Figure 14 Compared to the thickness T1 of the first region shown in (b), the thicknesses T2A and T3A of the first electrode 3 in the second region are thinner.

[0100] In addition, T2A > T3A. Thus, the thickness T2A of the first electrode 3 portions on both sides of the first direction A is different from the thickness T3A of the first electrode 3 portions on both sides of the second direction B. Therefore, although the piezoelectric material 2 is anisotropic, the thickness of the first electrode 3 in this second region is set to be different as described above, thus, similar to the elastic wave device 1, it is possible to effectively suppress stray noise in the resonance characteristics.

[0101] Furthermore, the other structural configurations of the elastic wave device 61 are the same as those of the elastic wave device 1.

[0102] Figure 15 (a) and Figure 15(b) is a front sectional view and a side sectional view illustrating the elastic wave device according to the fifth embodiment of the present invention. In the elastic wave device 61A, the width of the frame-shaped recess constituting the second region is different on both sides in the first direction A and on both sides in the second direction B. That is, the width WB of the frame-shaped recess on both sides in the second direction B becomes greater than the width WA of the frame-shaped recess on both sides in the first direction A. In this way, the width of the recess can also be different on both sides in the first direction A and on both sides in the second direction B. In this case, similarly to the elastic wave device 1, stray noise appearing in the resonance characteristics can be effectively suppressed.

[0103] Alternatively, the structure of the fourth embodiment can also be used in conjunction with... Figure 15 of (a), Figure 15 The structure of the elastic wave device 61A shown in (b) is shown.

[0104] Figure 16 (a)~ Figure 16 (c) is a partially cut front sectional view illustrating the structure in which an insulating film is disposed within a frame-shaped recess. Figure 16 In (a), an insulating film 62 with a thickness less than the depth of the recess is stacked. Figure 16 In (b), an insulating film 63 with a thickness equal to the depth of the recess is stacked. Figure 16 In (c), an insulating film 64 is laminated, with a thickness greater than the depth of the recess. Similarly, insulating films 62, 63, or 64 can also be disposed within the recess. Alternatively, materials different from the first electrode 3 and the second electrode 4 can be used instead of insulating films 62, 63, and 64.

[0105] Figure 17 (a) and Figure 17(b) is a top view and a front sectional view of the elastic wave device according to the sixth embodiment of the present invention. In the elastic wave device 65, the first electrode 3 is composed of a stack of layers 3A to 3C. The first layer 3A has a rectangular shape and is disposed on the first main surface 2a of the piezoelectric body 2. The second layer 3B has a rectangular frame shape. Moreover, the outer periphery of the rectangular frame overlaps with the outer periphery of the first layer 3A. The third layer 3C has a rectangular frame shape. The outer shape of the third layer 3C is smaller than the outer shape of the second layer 3B. The inner periphery of the second layer 3B overlaps with the inner periphery of the third layer 3C. In the elastic wave device 65, the second layer 3B and the third layer 3C of the first electrode 3 function as a mass-added film. Moreover, in the top view, the area where the first electrode 3 and the second electrode 4 overlap each other has a first region, a second region, and a third region. More specifically, the area surrounded by the second layer 3B and the third layer 3C is the first region. Furthermore, the region where the third layer 3C is provided is the second region. In this embodiment, in this second region, the widths of the third layer 3C, which are the mass-added film portions on both sides in the first direction A, and the widths of the third layer 3C, which are the mass-added film portions on both sides in the second direction B, are different. Therefore, similar to the elastic wave device 1 of the first embodiment, the anisotropy of the piezoelectric body 2 can be compensated, and stray noise appearing in the resonance characteristics can be effectively suppressed.

[0106] In this embodiment, a rectangular frame-shaped third region, located outside the third layer 3C and overlapping the second layer 3B, is provided outside the second region. Similarly, a third region may also be provided outside the second region.

[0107] Figure 18 This is a partially cut front sectional view used to illustrate the elastic wave device according to the seventh embodiment. In the elastic wave device 71, an insulating layer 72 is provided on the first main surface 2a of the piezoelectric body 2. The insulating layer 72 is made of a suitable insulator such as silicon oxide.

[0108] Furthermore, a first electrode 3 is provided such that an insulating layer 72 is covered. The insulating layer 72 has a rectangular planar shape.

[0109] The first electrode 3, when viewed from above, has a shape larger than the insulating layer 72. That is, when viewed from above, the insulating layer 72 is located inside the first electrode 3. Therefore, a rectangular frame-shaped second region is formed around the insulating layer 72. Here, the portion where the insulating layer 72 is provided corresponds to the first region. Moreover, in the second region located outside the first region, the thickness of the first electrode 3 is made different on both sides in the first direction A and on both sides in the second direction B. In this case, the portion of the first electrode 3 located in the second region corresponds to the aforementioned mass-added film.

[0110] Figure 19 (a) and Figure 19(b) are the main sectional views of the elastic wave device used to illustrate the modified examples of the frame section.

[0111] like Figure 19 As shown in (a), the frame-like portion formed by the mass-added film 6 can also be disposed on the outside of the first electrode 3. Figure 19 In (a), viewed from above, the region where at least one of the first electrode 3 and the mass-added film 6 overlaps with the second electrode 4 has a first region and a second region. The region where the first electrode 3 and the second electrode 4 face each other across the piezoelectric element 2 is the first region. The mass-added film 6 is disposed in the second region outside the first region. Here, mass-added film portions 6b and 6d are disposed outside the first electrode 3 in the first direction A. Although not specifically illustrated, mass-added film portions are also disposed outside the first electrode 3 in the second direction B.

[0112] In addition, such as Figure 19 As shown in (b), the frame-like portion formed by the mass-added film 6 can also be configured to extend from the first electrode 3 to the outside of the first electrode 3. Although in Figure 19 In (b), the mass-added membrane portions 6b and 6d on both sides of the first direction A are shown, but the mass-added membrane portions on both sides of the second direction B can also be constructed in the same way.

[0113] Therefore, in this invention, the mass-added film only needs to be disposed on at least one of the first electrode or the second electrode and on the outside of the first electrode or the second electrode.

[0114] Figure 20 This is a front cross-sectional view of the elastic wave device according to the eighth embodiment. In the elastic wave device 81, an acoustic reflector 82 is provided on the second main surface 2b side of the piezoelectric body 2. Here, a support substrate 83 is provided around the acoustic reflector 82. The acoustic reflector 82 is stacked on the lower surface of the second electrode 4. The acoustic reflector 82 is composed of a stack of low acoustic impedance layers 82a, 82c, 82e, which are low acoustic impedance films and have relatively low acoustic impedance, and high acoustic impedance layers 82b, 82d, 82f, which are high acoustic impedance films. In this way, the acoustic reflecting part in the present invention is not limited to an air gap, and the acoustic reflector 82 can also be used.

[0115] There are no particular limitations on the materials used to form the low acoustic impedance layers 82a, 82c, 82e and the high acoustic impedance layers 82b, 82d, 82f, as long as the acoustic impedance relationship described above is satisfied.

[0116] In the elastic wave device 81, the structure of the mass-added film 6 disposed on the first electrode 3 is the same as in the first embodiment. Therefore, similar to the first embodiment, stray noise appearing in the resonance characteristics can be effectively suppressed.

[0117] Furthermore, in the above embodiments, the excitation region is rectangular, and the second region is a rectangular frame-like portion. However, in the elastic wave device of the present invention, the excitation region may also have a polygonal shape other than a rectangle. In this case, the planar shape of the second region becomes a frame-like portion corresponding to the aforementioned polygon.

[0118] exist Figure 21 (a)~ Figure 21 (d) and Figure 22 of (a), Figure 22 (b) shows a variation of such a frame-like part.

[0119] exist Figure 21 In the mass-added membrane 6 shown in (a), the widths of the mass-added membrane portions 6a and 6c that are opposite each other are different. The widths of the mass-added membrane portions 6b and 6d that are opposite each other are also different. In this way, the widths of the mass-added membrane portions that are opposite each other can also be different.

[0120] In addition, such as Figure 21 As shown in (b), the mass-added membrane portions 6a and 6c may not be parallel, and the mass-added membrane portions 6b and 6d may not be parallel.

[0121] Furthermore, it could also be like... Figure 21 As shown in the variant example (c), the mass-added membrane portion 6d is curved instead of having a straight shape.

[0122] like Figure 21 As shown in (d), it is also possible that in the generally rectangular mass-added membrane 6, the corners of the part where the mass-added membrane portion 6a and the mass-added membrane portion 6b are connected are cut off, and an inclined portion 6f is provided in top view.

[0123] Furthermore, it is also possible to Figure 22 The linear mass-added membrane portion 6a shown in (a) is provided with a recess 6g that opens outwards. Alternatively, it can be as follows... Figure 22 As shown in (b), a protrusion 6h protruding outward is provided in the mass-added membrane portion 6a.

[0124] Furthermore, the elastic wave device of the present invention can be suitably used as an elastic wave resonator. The present invention can also be applied to elastic wave filters having such an elastic wave resonator.

[0125] Figure 23This is a circuit diagram of the elastic wave filter according to the ninth embodiment. The elastic wave filter 151 has series arm resonators S1 to S4 and parallel arm resonators P1 to P3. The series arm resonators S1 to S4 and the parallel arm resonators P1 to P3 are each composed of elastic wave resonators. As at least one of the multiple elastic wave resonators constituting a trapezoidal filter, the elastic wave device of the present invention can be used.

[0126] Furthermore, the elastic wave filter involved in this invention is not limited to... Figure 23 The trapezoidal filter shown is an example. This invention can also be applied to a wide variety of elastic wave filters with multiple elastic wave resonators.

[0127] Explanation of reference numerals in the attached figures

[0128] 1, 21, 31, 41, 51, 61, 61A, 65, 71, 81: Elastic wave device;

[0129] 2: Piezoelectric element;

[0130] 2a, 2b: First principal face, second principal face;

[0131] 3, 4: Electrode 1 and Electrode 2;

[0132] 3A~3C: Floors 1 to 3;

[0133] 5: Supporting components;

[0134] 5a: Opening;

[0135] 6: Quality-added film;

[0136] 6a~6d: Mass-added membrane portion;

[0137] 6e: Corner portion;

[0138] 6f: Inclined portion;

[0139] 6g: concave part;

[0140] 6h: Protrusion;

[0141] 33a~33d: Mass-added membrane portion;

[0142] 62, 63, 64: Insulating film;

[0143] 72: Insulation layer;

[0144] 82: Sound reflector;

[0145] 82a, 82c, 82e: Low acoustic impedance layers;

[0146] 82b, 82d, 82f: High acoustic impedance layers;

[0147] 83: Support base plate;

[0148] 151: Elastic wave filter.

Claims

1. An elastic wave device, comprising: A piezoelectric material having a first principal surface and a second principal surface opposite to each other, and having anisotropy in a plane parallel to the first principal surface and the second principal surface; The first electrode is disposed on the first main surface of the piezoelectric body; The second electrode is disposed on the second main surface of the piezoelectric body and is opposite to the first electrode across the piezoelectric body; An acoustic reflector is disposed on the surface of the second electrode opposite to the piezoelectric element; as well as A mass-added film, wherein at least one of the first electrode and the second electrode is disposed on the first electrode or the second electrode, and at least one of the first electrode or the second electrode is disposed on the outer side of the second electrode. When viewed from above, the region where at least one of the first electrode and the mass-added film overlaps with the second electrode includes a first region and a second region surrounding the first region. Regarding the mass-added film, in the second region, the structure of the mass-added film portions on both sides of the first direction within the plane of the piezoelectric body differs from the structure of the mass-added film portions on both sides of the second direction within the plane of the piezoelectric body, wherein the second direction differs from the first direction. The mass-adding membrane is disposed in the second region, forming a frame-shaped protrusion. The width, thickness, and material of the frame-shaped protrusion are different in the mass-adding membrane portions on both sides of the first direction and the mass-adding membrane portions on both sides of the second direction.

2. The elastic wave device according to claim 1, wherein, The second region is the frame-shaped protrusion, and the thickness of the mass-added film at the corner of the frame-shaped protrusion is greater than the thickness of the other mass-added film portions in the second region.

3. The elastic wave device according to claim 1 or 2, wherein, The mass-added membrane is integrally formed of the same material as at least one of the first electrode and the second electrode.

4. The elastic wave device according to claim 1 or 2, wherein, The mass-added film is made of a different material than the first electrode and the second electrode.

5. The elastic wave device according to claim 1 or 2, wherein, The piezoelectric material is a single-crystal piezoelectric material.

6. The elastic wave device according to claim 5, wherein, The piezoelectric material is LiTaO3 or LiNbO3.

7. The elastic wave device according to claim 1 or 2, wherein, The second direction is a direction orthogonal to the first direction.

8. The elastic wave device according to claim 1 or 2, wherein, The region where the first electrode and the second electrode face each other is the excitation region. The excitation region is rectangular in shape when viewed from above.

9. The elastic wave device according to claim 1 or 2, wherein, Body waves utilizing thickness shearing modes.

10. The elastic wave device according to claim 1 or 2, wherein, The body wave of the thickness longitudinal mode was utilized.

11. The elastic wave device according to claim 1 or 2, wherein, The sound reflecting part is an air gap. The elastic wave device has a support member stacked on the second main surface side of the piezoelectric body to provide the air gap.

12. The elastic wave device according to claim 1 or 2, wherein, The acoustic reflector is an acoustic reflector composed of a stack of low acoustic impedance films with relatively low acoustic impedance and high acoustic impedance films with relatively high acoustic impedance.

13. An elastic wave device, comprising: A piezoelectric material having a first principal surface and a second principal surface opposite to each other, and having anisotropy in a plane parallel to the first principal surface and the second principal surface; The first electrode is disposed on the first main surface of the piezoelectric body; The second electrode is disposed on the second main surface of the piezoelectric body and is opposite to the first electrode across the piezoelectric body; as well as An acoustic reflector is disposed on the surface of the second electrode opposite to the piezoelectric element. The excitation region where the first electrode and the second electrode face each other has a first region and a second region surrounding the first region. In the second region, at least one of the first electrode and the second electrode is thinner than at least one of the first electrode and the second electrode in the first region. Furthermore, in the second region, the structure of at least one of the first electrode and the second electrode on both sides of the piezoelectric body in a first direction differs from the structure of at least one of the first electrode and the second electrode on both sides of the piezoelectric body in a second direction, where the second direction differs from the first direction. The first electrode and the second electrode have rectangular shapes, and the second region forms a frame-shaped recess. In the second region, at least one of the thickness of the side surfaces on both sides of the first electrode and the second electrode in the first direction and the thickness of the side surfaces on both sides of the second direction, and at least one of the width on both sides of the first direction and the width on both sides of the second direction are different.

14. The elastic wave device according to claim 13, wherein, The piezoelectric material is a single-crystal piezoelectric material.

15. The elastic wave device according to claim 14, wherein, The piezoelectric material is LiTaO3 or LiNbO3.

16. The elastic wave device according to any one of claims 13 to 15, wherein, The second direction is a direction orthogonal to the first direction.

17. The elastic wave device according to any one of claims 13 to 15, wherein, The region where the first electrode and the second electrode face each other is the excitation region. The excitation region is rectangular in shape when viewed from above.

18. The elastic wave device according to any one of claims 13 to 15, wherein, Body waves utilizing thickness shearing modes.

19. The elastic wave device according to any one of claims 13 to 15, wherein, The body wave of the thickness longitudinal mode was utilized.

20. The elastic wave device according to any one of claims 13 to 15, wherein, The sound reflecting part is an air gap. The elastic wave device has a support member stacked on the second main surface side of the piezoelectric body to provide the air gap.

21. The elastic wave device according to any one of claims 13 to 15, wherein, The acoustic reflector is an acoustic reflector composed of a stack of low acoustic impedance films with relatively low acoustic impedance and high acoustic impedance films with relatively high acoustic impedance.

22. An elastic wave filter having multiple elastic wave resonators, wherein, At least one elastic wave resonator is an elastic wave device as described in any one of claims 1 to 21.

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