Elastic wave resonator, elastic wave filter, multiplexer, high frequency front end circuit, and communication device

Abstract

This elastic wave resonator uses bulk waves in a shear vibration mode and comprises: a piezoelectric body; an upper electrode provided on the piezoelectric body; and a lower electrode provided below the piezoelectric body. When a direction parallel to the surface of the piezoelectric body and parallel to the direction of shear vibration is defined as a first direction, and a direction parallel to the surface of the piezoelectric body and perpendicular to the direction of shear vibration is defined as a second direction, the aspect ratio (Wy1 / Wx1) that is the ratio of the length (Wx1) in the first direction and the length (Wy1) in the second direction of at least one of the upper electrode and the lower electrode is greater than one.

Description

Acoustic wave resonator, acoustic wave filter, multiplexer, high frequency front-end circuit and communication device

[0001] The present invention relates to an acoustic wave resonator, an acoustic wave filter, a multiplexer, a high-frequency front-end circuit, and a communication device.

[0002] Patent Document 1 describes a ladder filter including parallel resonators and series resonators, in which the ratio (b / a) of the length a of a short side to the length b of a long side of at least one of the parallel resonators and the series resonators is set within a predetermined range.

[0003] Japanese Unexamined Patent Publication No. 7-154198

[0004] In such a resonator, it is required to improve the resonator characteristics such as Q. In Patent Document 1, the direction of the shear vibration in the shear vibration mode is not taken into consideration.

[0005] An object of the present invention is to provide an acoustic wave resonator, an acoustic wave filter, a multiplexer, a high-frequency front-end circuit, and a communication device that can improve the resonator characteristics.

[0006] An elastic wave resonator according to one embodiment is an elastic wave resonator that utilizes bulk waves in a shear vibration mode, and has a piezoelectric body, an upper electrode provided on the piezoelectric body, and a lower electrode provided below the piezoelectric body, and when a direction parallel to the surface of the piezoelectric body and parallel to the direction of shear vibration is defined as a first direction, and a direction parallel to the surface of the piezoelectric body and perpendicular to the direction of shear vibration is defined as a second direction, the aspect ratio (Wy1 / Wx1) of at least one of the upper electrode and the lower electrode, which is the ratio of the length (Wx1) in the first direction to the length (Wy1) in the second direction, is greater than 1.

[0007] An acoustic wave filter according to one aspect includes the acoustic wave resonator described above.

[0008] A multiplexer according to one aspect includes a plurality of filters including the acoustic wave filter described above, and one of the input terminal and one of the output terminal of each of the plurality of filters are electrically connected to each other.

[0009] A high-frequency front-end circuit according to one aspect includes the acoustic wave filter described above.

[0010] A high-frequency front-end circuit according to one embodiment includes the above multiplexer.

[0011] A communication device according to one aspect includes the above-described high-frequency front-end circuit.

[0012] According to the acoustic wave resonator, acoustic wave filter, multiplexer, high-frequency front-end circuit, and communication device of the present invention, it is possible to improve the resonator characteristics.

[0013] FIG. 1 is a plan view showing an elastic wave resonator according to a first preferred embodiment. FIG. 2 is a cross-sectional view taken along line II-II' of FIG. 1 . FIG. 3 is a plan view showing the configuration of an upper electrode and a frame electrode. FIG. 4 is a plan view showing the configuration of an upper electrode and a frame electrode according to a first modified example. FIG. 5 is a plan view showing the configuration of an upper electrode and a frame electrode according to a second modified example. FIG. 6 is a plan view showing the configuration of an upper electrode and a frame electrode according to a third modified example. FIG. 7 is a cross-sectional view showing the configuration of an upper electrode and a frame electrode according to a fourth modified example. FIG. 8 is a graph showing the relationship between the aspect ratio of the upper electrode and the resonance resistance of elastic wave resonators according to Example 1 and Comparative Example 1. FIG. 9 is a graph showing the relationship between the aspect ratio of the upper electrode and the Qmax of elastic wave resonators according to Example 1 and Comparative Example 1. FIG. 10 is a graph showing the relationship between impedance and frequency of elastic wave resonators according to Example 1-2 and Comparative Examples 1-1 and 1-3. FIG. 11 is a graph showing the relationship between the real part of impedance and frequency of elastic wave resonators according to Example 1-2 and Comparative Examples 1-1 and 1-3. FIG. 12 is a graph showing the relationship between Q and frequency for the elastic wave resonators according to Example 1-2 and Comparative Examples 1-1 and 1-3. FIG. 13A is a graph showing the relationship between impedance and frequency for the elastic wave resonator according to Example 2-1. FIG. 13B is a graph showing the relationship between the real part of the impedance and frequency for the elastic wave resonator according to Example 2-1. FIG. 13C is a graph showing the relationship between Q and frequency for the elastic wave resonator according to Example 2-1. FIG. 14A is a graph showing the relationship between impedance and frequency for the elastic wave resonator according to Example 2-2. FIG. 14B is a graph showing the relationship between the real part of the impedance and frequency for the elastic wave resonator according to Example 2-2. FIG. 14C is a graph showing the relationship between Q and frequency for the elastic wave resonator according to Example 2-2. FIG. 15A is a graph showing the relationship between impedance and frequency for the elastic wave resonator according to Example 2-3. FIG. 15B is a graph showing the relationship between the real part of the impedance and frequency for the elastic wave resonator according to Example 2-3. Fig. 15C is a graph showing the relationship between Q and frequency for the elastic wave resonator according to Example 2-3. Fig. 16 is a plan view showing the elastic wave resonator according to Example 3. Fig. 17 is a graph showing the relationship between impedance and frequency for the elastic wave resonators according to Examples 1-1 and 3.FIG. 18 is a graph showing the relationship between the real part of the impedance and the frequency for the elastic wave resonators according to Examples 1-1 and 3. FIG. 19 is a graph showing the relationship between the Q and the frequency for the elastic wave resonators according to Examples 1-1 and 3. FIG. 20 is a graph showing the relationship between the resonance resistance Zr and the ratio S / t for the elastic wave resonator according to Example 4. FIG. 21 is a graph showing the relationship between the Qmax and the ratio S / t for the elastic wave resonator according to Example 4. FIG. 22 is a graph showing the relationship between the impedance and the frequency for the elastic wave resonator according to Example 4 for different ratios S / t. FIG. 23 is a graph showing the relationship between the real part of the impedance and the frequency for the elastic wave resonator according to Example 4 for different ratios S / t. FIG. 24 is a graph showing the relationship between the Q and the frequency for the elastic wave resonator according to Example 4 for different ratios S / t. FIG. 25 is a graph showing the relationship between the Euler angles and the fractional bandwidth of a piezoelectric body using lithium niobate for the elastic wave resonator according to Example 5-1. FIG. 26 is a graph showing the relationship between the Euler angles of a piezoelectric body using lithium tantalate and the fractional bandwidth of an elastic wave resonator according to Example 5-2. FIG. 27 is a circuit diagram showing an elastic wave filter according to a second embodiment. FIG. 28 is a cross-sectional view schematically showing the configuration of an elastic wave filter according to the second embodiment. FIG. 29 is a plan view schematically showing the configuration of a resonator chip in the elastic wave filter according to the second embodiment. FIG. 30 is a plan view showing the configuration of a series arm resonator in FIG. 29. FIG. 31 is a cross-sectional view taken along the XXXI-XXXI' line in FIG. 30. FIG. 32 is a plan view schematically showing the front surface of a module substrate in the elastic wave filter according to the second embodiment. FIG. 33 is a plan view schematically showing inner layers of a module substrate in the elastic wave filter according to the second embodiment. FIG. 34 is a plan view schematically showing the rear surface of a module substrate in the elastic wave filter according to the second embodiment. FIG. 35 is a plan view showing the configuration of a series arm resonator according to a fifth modification. Fig. 36 is a graph showing the filter characteristics of the acoustic wave filter in accordance with Example 6-1. Fig. 37 is a graph showing the relationship between the aspect ratio and the relative bandwidth of the acoustic wave resonator included in the acoustic wave filter in accordance with Example 6. Fig. 38 is a graph showing the filter characteristics of the acoustic wave filters in accordance with Examples 6-1 and 6-2.FIG. 39 is a diagram showing the configuration of a communication device according to the third embodiment.

[0014] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to these embodiments. Note that each embodiment described in the present disclosure is illustrative, and partial substitution or combination of configurations between different embodiments is possible. In modified examples and the second and subsequent embodiments, descriptions 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 in each embodiment.

[0015] First Embodiment Fig. 1 is a plan view showing an elastic wave resonator according to a first embodiment. Fig. 2 is a cross-sectional view taken along line II-II' of Fig. 1. An elastic wave resonator 10 according to the first embodiment is a resonator that utilizes bulk waves in a shear vibration mode, i.e., a BAW (Bulk Acoustic Wave) element.

[0016] 1 and 2, the elastic wave resonator 10 includes a support member 13, a piezoelectric body 20, an upper electrode 31, a lower electrode 32, a frame electrode 33, lead wires 34 and 35, and connection electrodes 41 and 42. As shown in Fig. 2, the lower electrode 32 and lead wire 35, the piezoelectric body 20, the upper electrode 31 and lead wire 34, the frame electrode 33, and the connection electrodes 41 and 42 are layered in this order on the support member 13.

[0017] In the following description, the thickness direction of the piezoelectric body 20 is referred to as the Z direction, the direction perpendicular to the Z direction is referred to as the X direction, and the direction perpendicular to the Z direction and the X direction is referred to as the Y direction. The X direction and the Y direction are each parallel to the surface (first main surface 20a) of the piezoelectric body 20. In the following description, a plan view refers to the positional relationship when viewed from a direction perpendicular to the first main surface 20a of the piezoelectric body 20 (Z direction).

[0018] The support member 13 is provided opposite the second main surface 20b of the piezoelectric body 20. The support member 13 includes a support substrate 11 and an intermediate layer 12. The support substrate 11 is made of silicon (Si), quartz crystal, or the like. The intermediate layer 12 is provided between the support substrate 11 and the piezoelectric body 20. The intermediate layer 12 is formed of an insulating material such as silicon oxide. Note that the support member 13 may be configured without the intermediate layer 12, with the piezoelectric body 20 provided on the support substrate 11. In other words, the piezoelectric body 20 is bonded to the support substrate 11 directly or via the intermediate layer 12 (insulating layer).

[0019] A recess 14 (hollow portion) is formed on the surface of the support member 13 (intermediate layer 12) facing the second main surface 20b of the piezoelectric body 20. The recess 14 is provided so as to overlap, in plan view, with the excitation region of the resonator formed by overlapping the piezoelectric body 20, the upper electrode 31, and the lower electrode 32. This reduces energy loss of the bulk wave during excitation, resulting in good resonance characteristics.

[0020] The piezoelectric body 20 is in the form of a flat plate having a first main surface 20a and a second main surface 20b opposite to the first main surface 20a. The piezoelectric body 20 is made of lithium niobate (LiNbO ３ ) or lithium tantalate (LiTaO ３ The piezoelectric body 20 is a substrate made of a single crystal of aluminum nitride (AlN). The piezoelectric body 20 is not limited to this, and aluminum nitride (AlN), zinc oxide (ZnO), lead zirconate titanate (PZT), etc. may also be used. The thickness of the piezoelectric body 20 is not particularly limited, but is preferably 1 μm or less. Furthermore, the piezoelectric body 20 may have a structure in which multiple layers of piezoelectric bodies with different crystal orientations are stacked.

[0021] The upper electrode 31 is provided on the top (first main surface 20a) of the piezoelectric body 20. The lower electrode 32 is provided on the bottom (second main surface 20b) of the piezoelectric body 20. As shown in FIGS. 1 and 2 , the upper electrode 31 and the lower electrode 32 overlap in a region overlapping with the recess 14. In other words, in the region overlapping with the recess 14, the piezoelectric body 20 is disposed between the upper electrode 31 and the lower electrode 32 in the Z direction. This allows bulk waves to propagate between the upper electrode 31 and the lower electrode 32. In the following description, the region where the upper electrode 31 and the lower electrode 32 overlap in a planar view may be described as the excitation region of the resonator.

[0022] The names "upper electrode 31" and "lower electrode 32" are used simply to define the respective portions, and do not limit the spatial arrangement or position of the BAW resonator. In addition, although the upper electrode 31, the lower electrode 32, and the recess 14 are each rectangular in plan view, they are not limited to this and may be circular or have other shapes.

[0023] The lead wiring 34 is provided in the same layer as the upper electrode 31, and is connected to one side of the upper electrode 31 in the X direction. The lead wiring 34 extends in one side of the X direction from the region overlapping with the recess 14, and is connected to a connection electrode 41 different from the upper electrode 31. The lead wiring 35 is provided in the same layer as the lower electrode 32, and is connected to the other side of the lower electrode 32 in the X direction. The lead wiring 35 extends from the region overlapping with the recess 14 to the opposite side of the lead wiring 34, and is connected to the connection electrode 42 through an opening OP formed in the piezoelectric body 20.

[0024] The upper electrode 31 and the lower electrode 32 are formed of a conductive material such as aluminum (Al), platinum (Pt), gold (Au), copper (Cu), molybdenum (Mo), tungsten (W), titanium (Ti), chromium (Cr), ruthenium (Ru), tantalum (Ta), or iridium (Ir), or an alloy containing at least one of these materials. The upper electrode 31 and the lower electrode 32 may be a laminate film containing these materials. An adhesion layer of Ti, NiCr, or the like may be provided between the upper electrode 31 and the lower electrode 32 and the support member 13 (intermediate layer 12). The lead-out wiring 34 is formed of the same material as the upper electrode 31. The lead-out wiring 35 is formed of the same material as the lower electrode 32. However, the lead-out wirings 34 and 35 may be formed of a different material from the upper electrode 31 and the lower electrode 32.

[0025] As described above, the elastic wave resonator 10 of this embodiment is a film bulk acoustic resonator (FBAR). That is, the recess 14 (cavity) is formed in the support member 13 (intermediate layer 12) in a portion overlapping the excitation region, and the piezoelectric body 20, upper electrode 31, and lower electrode 32 have a membrane structure. However, without being limited thereto, the elastic wave resonator 10 may also be a solidly mounted resonator (SMR) in which multiple low-impedance layers and multiple high-impedance layers are stacked instead of the recess 14 (cavity).

[0026] Next, the configuration of the upper electrode 31 and the frame electrode 33 will be described with reference to Figures 2 and 3. Figure 3 is a plan view showing the configuration of the upper electrode and the frame electrode. In Figure 3, arrow A indicates the direction of sliding vibration of the piezoelectric body 20. In this embodiment, the direction of sliding vibration of the piezoelectric body 20 indicated by arrow A is parallel to the X direction. In other words, the X direction (first direction) is parallel to the surface (first main surface 20a) of the piezoelectric body 20 and parallel to the direction of sliding vibration. Furthermore, the Y direction (second direction) is parallel to the surface (first main surface 20a) of the piezoelectric body 20 and perpendicular to the direction of sliding vibration.

[0027] 2, the frame electrode 33 is in contact with the upper electrode 31 and is provided on the upper surface of the upper electrode 31 (the surface opposite the piezoelectric body 20). As shown in Fig. 3, the frame electrode 33 is provided on the outer periphery of the upper electrode 31. The frame electrode 33 is rectangular and has a first portion 33a extending in the X direction and a second portion 33b extending in the Y direction.

[0028] In this embodiment, the outer shape of the upper electrode 31 is defined by the frame electrode 33. That is, the length Wx1 of the upper electrode 31 in the X direction is equal to the maximum length of the frame electrode 33 in the X direction. More specifically, the length Wx1 of the upper electrode 31 in the X direction is equal to the maximum length in the X direction between the outer edges of two adjacent second portions 33b of the frame electrode 33. Furthermore, the length Wy1 of the upper electrode 31 in the Y direction is equal to the maximum length in the Y direction of the frame electrode 33. More specifically, the length Wy1 of the upper electrode 31 in the Y direction is equal to the maximum length in the Y direction between the outer edges of two adjacent first portions 33a of the frame electrode 33.

[0029] The upper electrode 31 and the frame electrode 33 are rectangular with their short sides aligned with the direction of shear vibration (arrow A) of the piezoelectric body 20. That is, the length Wy1 of the upper electrode 31 in the Y direction is longer than its length Wx1 in the X direction. The aspect ratio (Wy1 / Wx1), which is the ratio of the length Wx1 of the upper electrode 31 in the X direction to the length Wy1 in the Y direction, is greater than 1. More preferably, the aspect ratio (Wy1 / Wx1) of the upper electrode 31 is 3 or greater.

[0030] In this way, because the upper electrode 31 is formed short along the direction of shear vibration (arrow A) of the piezoelectric body 20, the number of standing waves generated along the direction of shear vibration (arrow A) is reduced compared to when the length Wx1 of the upper electrode 31 in the X direction is longer than the length Wy1 in the Y direction. This reduces the response due to standing waves, especially near the anti-resonance frequency, and enhances the energy trapping effect of the frame electrode 33. As a result, the Q of the elastic wave resonator 10 is improved.

[0031] Furthermore, the width Wx2 in the X direction of the second portion 33b of the frame electrode 33 extending along the Y direction is larger than the width Wy2 in the Y direction of the first portion 33a of the frame electrode 33 extending along the X direction. In other words, the width Wy2 of the first portion 33a of the frame electrode 33 extending in a direction parallel to the direction of sliding vibration of the piezoelectric body 20 is smaller than the width Wx2 of the second portion 33b extending in a direction perpendicular to the direction of sliding vibration of the piezoelectric body 20.

[0032] In this embodiment, the area of ​​the frame electrode 33 can be reduced compared to a configuration in which the frame electrode 33 has the same width around its entire circumference. This prevents bulk wave energy from leaking outside the excitation region and reduces loss due to the boundary ring mode. In this embodiment, the boundary ring mode refers to a standing wave mode that exists in the frame electrode 33 in a configuration in which the frame electrode 33 is disposed on the upper electrode 31. In this embodiment, by reducing the width Wy2 of the first portion 33a extending in a direction parallel to the direction of shear vibration of the piezoelectric body 20, it is possible to suppress the occurrence of the boundary ring mode at a predetermined frequency and reduce loss.

[0033] Although the present embodiment has described the outer shape of the upper electrode 31, the outer shape of the lower electrode 32 may have a similar configuration. That is, the length Wy1 of the lower electrode 32 in the Y direction is longer than the length Wx1 of the lower electrode 32 in the X direction. Alternatively, the aspect ratio (Wy1 / Wx1), which is the ratio of the length Wx1 of the lower electrode 32 in the X direction to the length Wy1 of the lower electrode 32 in the Y direction, is greater than 1. Furthermore, while the configuration in which the frame electrode 33 is provided on the upper electrode 31 has been described, this is not limiting. The frame electrode 33 may be provided on the lower electrode 32, or on both the upper electrode 31 and the lower electrode 32. In this case, the description of the shapes of the various parts of the frame electrode 33 in FIG. 3 also applies to the frame electrode 33 provided on the lower electrode 32.

[0034] Furthermore, the phrase "arranged along the periphery" of the frame electrode 33 includes a configuration in which the frame electrode 33 is arranged in contact with the outer peripheral edge of the upper electrode 31 or the lower electrode 32, and a configuration in which the frame electrode 33 is arranged slightly inward from and spaced a predetermined distance from the outer peripheral edge of the upper electrode 31 or the lower electrode 32. More specifically, for example, when the area of ​​the lower electrode 32 is smaller than that of the upper electrode 31 (see FIGS. 7 and 8 ), the frame electrode 33 needs to be arranged along the periphery of the lower electrode 32. Alternatively, when the area of ​​the lower electrode 32 is smaller than that of the upper electrode 31 and the frame electrode 33 is arranged on the upper electrode 31, the frame electrode 33 needs to be arranged along the portion of the upper electrode 31 that overlaps the periphery of the lower electrode 32. Furthermore, when the shapes of the upper electrode 31 and the lower electrode 32 are different, the periphery of the upper electrode 31 can be rephrased as the periphery of the region where the upper electrode 31 and the lower electrode 32 overlap (excitation region). In this case, the frame electrode 33 is provided along the outer periphery of the region where the upper electrode 31 and the lower electrode 32 overlap (excitation region).

[0035] Furthermore, the direction of sliding vibration of the piezoelectric body 20 (arrow A) is parallel to the first portion 33a of the frame electrode 33 and perpendicular to the second portion 33b. This is not limiting, and the direction of sliding vibration of the piezoelectric body 20 (arrow A) may be at an angle of approximately ±30° with respect to the extension direction of the first portion 33a of the frame electrode 33. In this case, the length Wy1 of the upper electrode 31 is defined by the maximum length of the frame electrode 33 in the direction parallel to the direction of sliding vibration of the piezoelectric body 20 (Y direction). Furthermore, the length Wx1 of the upper electrode 31 is defined by the maximum length of the frame electrode 33 in the direction perpendicular to the direction of sliding vibration of the piezoelectric body 20 (X direction).

[0036] 3, for ease of understanding, the frame electrode 33 has a rectangular shape, i.e., the outer shape of the upper electrode 31 is rectangular. However, this is not limiting, and the frame electrode 33 and the upper electrode 31 may have other shapes.

[0037] FIG. 4 is a plan view showing the configuration of the upper electrode and frame electrode according to the first modification. As shown in FIG. 4, the upper electrode 31 and frame electrode 33A according to the first modification are elliptical. More specifically, the upper electrode 31 and frame electrode 33A have an elliptical shape with their minor axis oriented along the direction of shear vibration (arrow A) of the piezoelectric body 20. That is, the length Wx1 of the upper electrode 31 is defined by the maximum length of the elliptical shape in the X direction. Furthermore, the length Wy1 of the upper electrode 31 is defined by the maximum length of the elliptical shape in the Y direction. Furthermore, in the first modification, the aspect ratio (Wy1 / Wx1) of the upper electrode 31 is greater than 1.

[0038] Also, in this modified example, the width Wx2 in the X direction of the portion of the frame electrode 33A extending along the Y direction (the portion intersecting with the short axis direction) is smaller than the width Wy2 in the Y direction of the portion of the frame electrode 33A extending along the X direction (the portion intersecting with the long axis direction).

[0039] 5 is a plan view showing the configuration of the upper electrode and frame electrode according to the second modification. As shown in FIG. 5, the upper electrode 31 and frame electrode 33B according to the second modification are rectangular with arc-shaped corners. In other words, the first portion 33Ba and the second portion 33Bb of the frame electrode 33B are smoothly connected in an arc-like manner. Alternatively, the upper electrode 31 and frame electrode 33B may be elliptical. The definitions of the lengths Wx1 and Wy1 of the upper electrode 31 and the aspect ratio (Wy1 / Wx1) of the frame electrode 33B in the second modification, and the width Wx2 in the X direction and the width Wy2 in the Y direction of the frame electrode 33B are the same as those in the first embodiment.

[0040] FIG. 6 is a plan view showing the configuration of the upper electrode and frame electrode according to the third modification. As shown in FIG. 6, the upper electrode 31 and frame electrode 33C according to the third modification are polygonal. The first portion 33Ca, the second portion 33Cb, and the third portion 33Cc of the frame electrode 33C each extend in a direction inclined at an angle relative to the direction of shear vibration of the piezoelectric body 20. In this modification, the length Wy1 of the upper electrode 31 is also the maximum length of the frame electrode 33C in the direction perpendicular to the direction of shear vibration of the piezoelectric body 20 (Y direction). The length Wx1 of the upper electrode 31 is also the maximum length of the frame electrode 33C in the direction parallel to the direction of shear vibration of the piezoelectric body 20 (X direction).

[0041] In the third modification, the width Wx2 of the frame electrode 33C in the X direction is the width Wx2 in the X direction of a portion of the first portion 33Ca, the second portion 33Cb, and the third portion 33Cc that extends along a direction perpendicular to the direction of sliding vibration of the piezoelectric body 20 (for example, the second portion 33Cb that forms the smallest angle with the direction perpendicular to the direction of sliding vibration). The width Wy2 of the frame electrode 33C in the Y direction is the width Wy2 in the Y direction of a portion of the first portion 33Ca, the second portion 33Cb, and the third portion 33Cc that extends along a direction parallel to the direction of sliding vibration of the piezoelectric body 20 (for example, the first portion 33Ca that forms the smallest angle with the direction of sliding vibration).

[0042] 7 is a cross-sectional view showing the configuration of the upper electrode and frame electrode according to the fourth modification. As shown in FIG. 7, the peripheral edge of the upper electrode 31 according to the fourth modification is spaced apart from the piezoelectric body 20 via the insulating layer 22. In this case, the length Wy1 of the upper electrode 31 is determined by the portion of the upper electrode 31 that contacts the piezoelectric body 20 and is provided with the frame electrode 33 (the portion in which the piezoelectric body 20, the upper electrode 31, and the frame electrode 33 are stacked in this order). The portion of the upper electrode 31 that is spaced apart from the piezoelectric body 20 (the portion in which the piezoelectric body 20, the insulating layer 22, the upper electrode 31, and the frame electrode 33 are stacked in this order) is not included in the length Wy1. In other words, the length Wy1 of the upper electrode 31 is the length of the portion of the upper electrode 31 that contacts the piezoelectric body 20 and is provided with the frame electrode 33 in the direction perpendicular to the direction of shear vibration of the piezoelectric body 20 (the Y direction).

[0043] The width Wy2 of the frame electrode 33 in the Y direction is also determined by the portion of the frame electrode 33 that overlaps the region where the upper electrode 31 and the piezoelectric body 20 are in contact (the portion where the piezoelectric body 20, the upper electrode 31, and the frame electrode 33 are stacked in this order). The width Wy2 does not include the portion of the frame electrode 33 that overlaps the region where the upper electrode 31 and the piezoelectric body 20 are separated (the portion where the piezoelectric body 20, the insulating layer 22, the upper electrode 31, and the frame electrode 33 are stacked in this order). In other words, the width Wy2 of the frame electrode 33 in the Y direction is the length of the portion of the frame electrode 33 that overlaps the region where the upper electrode 31 and the piezoelectric body 20 are in contact, in the direction perpendicular to the direction of shear vibration of the piezoelectric body 20 (the Y direction). Note that, although the length Wy1 of the upper electrode 31 in the Y direction and the width Wy2 of the frame electrode 33 in the Y direction have been described in FIG. 7 , the description of FIG. 7 can also be applied to the X direction.

[0044] Next, the resonator characteristics of elastic wave resonator 10 when various conditions such as the aspect ratio (Wy1 / Wx1) of upper electrode 31 and widths Wx2 and Wy2 of frame electrode 33 are changed will be described.

[0045] In the following examples and comparative examples, a single crystal of lithium niobate was used as the material of the piezoelectric body 20. The Euler angles (φ, θ, ψ) of the lithium niobate constituting the piezoelectric body 20 were (φ, θ, ψ) = (0°, 73°, 0°).

[0046] The upper electrode 31 was laminated in the order of Ti / Pt / Ti / Al / Ti from the first main surface 20a of the piezoelectric body 20. The film thicknesses of Ti / Pt / Ti / Al / Ti were 4 / 10 / 14 / 120 / 10 nm, respectively. The lower electrode 32 was laminated in the order of Ti / Pt / Ti / Al / Ti from the second main surface 20b of the piezoelectric body 20. The film thicknesses of Ti / Pt / Ti / Al / Ti were 4 / 10 / 14 / 120 / 10 nm, respectively.

[0047] The frame electrode 33 was formed by laminating Ti / Pt / Ti in this order on the surface of the upper electrode 31. The film thicknesses of Ti / Pt / Ti were 4 / 13 / 4 nm, respectively.

[0048] In the support member 13, the intermediate layer 12 is made of silicon oxide (SiO ２ ), and the support substrate 11 is made of silicon (Si).

[0049] Example 1 In Example 1 and Comparative Example 1, the resonator characteristics of elastic wave resonator 10 when the aspect ratio (Wy1 / Wx1) of the upper electrode is changed will be described. FIG. 8 is a graph showing the relationship between the aspect ratio of the upper electrode and the resonance resistance for elastic wave resonators according to Example 1 and Comparative Example 1. FIG. 9 is a graph showing the relationship between the aspect ratio of the upper electrode and Qmax for elastic wave resonators according to Example 1 and Comparative Example 1. Table 1 shows the relationship between the aspect ratio of the upper electrode and the resonance resistance and Qmax for elastic wave resonators according to Example 1 and Comparative Example 1. In the following description, "Qmax" represents the maximum value of Q.

[0050] In Table 1 and FIGS. 8 and 9, Examples 1-1, 1-2, and 1-3 show resonator characteristics when the aspect ratio (Wy1 / Wx1) of the upper electrode 31 is greater than 1 and the aspect ratio (Wy1 / Wx1) is varied. The aspect ratio (Wy1 / Wx1) of Example 1-1 is Wy1 / Wx1 = 2.0. The aspect ratio (Wy1 / Wx1) of Example 1-2 is Wy1 / Wx1 = 3.0. The aspect ratio (Wy1 / Wx1) of Example 1-3 is Wy1 / Wx1 = 4.52. Comparative Examples 1-1, 1-2, and 1-3 show resonator characteristics when the aspect ratio (Wy1 / Wx1) of the upper electrode 31 is 1 or less and the aspect ratio (Wy1 / Wx1) is varied. The aspect ratio (Wy1 / Wx1) of Comparative Example 1-1 is Wy1 / Wx1 = 1.0. The aspect ratio (Wy1 / Wx1) of Comparative Example 1-2 is Wy1 / Wx1 = 0.66. The aspect ratio (Wy1 / Wx1) of Comparative Example 1-3 is Wy1 / Wx1 = 0.50.

[0051] Furthermore, in Examples 1-1, 1-2, and 1-3 and Comparative Examples 1-1, 1-2, and 1-3, the area of ​​the upper electrode 31 is constant. That is, the impedance of the acoustic wave resonators 10 according to Examples 1-1, 1-2, and 1-3 and Comparative Examples 1-1, 1-2, and 1-3 is constant. However, Table 1 and FIGS. 8 and 9 include variations in the resonator characteristics due to variations in processing during the manufacturing process.

[0052]

[0053] 8, in Examples 1-1, 1-2, and 1-3, as the aspect ratio (Wy1 / Wx1) of upper electrode 31 increases, the resonant resistance (Zr), which is correlated with the series resistance of elastic wave resonator 10, decreases. In Comparative Examples 1-1, 1-2, and 1-3, when the aspect ratio (Wy1 / Wx1) becomes 1 or less, the resonant resistance (Zr) increases sharply.

[0054] As shown in Table 1 and graph 2 of FIG. 9, in Examples 1-1, 1-2, and 1-3, Q increases as the aspect ratio (Wy1 / Wx1) of the upper electrode 31 increases. When the aspect ratio (Wy1 / Wx1) exceeds 3, Q tends to saturate (the increase becomes smaller). Furthermore, in Comparative Examples 1-1, 1-2, and 1-3, Q decreases when the aspect ratio (Wy1 / Wx1) becomes 1 or less.

[0055] Fig. 10 is a graph showing the relationship between impedance and frequency for the elastic wave resonators according to Example 1-2 and Comparative Examples 1-1 and 1-3. Fig. 11 is a graph showing the relationship between the real part of impedance and frequency for the elastic wave resonators according to Example 1-2 and Comparative Examples 1-1 and 1-3. Fig. 12 is a graph showing the relationship between Q and frequency for the elastic wave resonators according to Example 1-2 and Comparative Examples 1-1 and 1-3.

[0056] As described above, in the elastic wave resonator 10 according to Example 1-2 shown in FIGS. 10 to 12, the aspect ratio (Wy1 / Wx1) of the upper electrode 31 is 3.0. In the elastic wave resonator 10 according to Comparative Example 1-1 shown in FIGS. 10 to 12, the aspect ratio (Wy1 / Wx1) of the upper electrode 31 is 1.0. In the elastic wave resonator 10 according to Comparative Example 1-3 shown in FIGS. 10 to 12, the aspect ratio (Wy1 / Wx1) of the upper electrode 31 is 0.5.

[0057] As shown in Fig. 10, the frequency characteristics of impedance (|Z|) of Example 1-2 and Comparative Examples 1-1 and 1-3 all show similar trends. As shown in Fig. 11, Example 1-2 has a smaller real part of impedance than Comparative Examples 1-1 and 1-3. Furthermore, as shown in Fig. 12, Example 1-2 has a larger Q than Comparative Examples 1-1 and 1-3.

[0058] From the above results, it is possible to reduce the resonance resistance (Zr) of the elastic wave resonator 10 and improve the Q by increasing the aspect ratio (Wy1 / Wx1), which is the ratio of the length Wx1 in the X direction to the length Wy1 in the Y direction of the upper electrode 31, to more than 1. More preferably, by setting the aspect ratio (Wy1 / Wx1) to 3 or more, it is possible to further reduce the resonance resistance (Zr) and increase the Q.

[0059] Example 2 In Example 2, the resonator characteristics of the elastic wave resonator 10 when the width Wx2 in the X direction and the width Wy2 in the Y direction of the frame electrode 33 are changed will be described. Fig. 13A is a graph showing the relationship between impedance and frequency for the elastic wave resonator in Example 2-1. Fig. 13B is a graph showing the relationship between the real part of the impedance and frequency for the elastic wave resonator in Example 2-1. Fig. 13C is a graph showing the relationship between Q and frequency for the elastic wave resonator in Example 2-1.

[0060] FIG. 14A is a graph showing the relationship between impedance and frequency for the elastic wave resonator in accordance with Example 2-2. FIG. 14B is a graph showing the relationship between the real part of the impedance and frequency for the elastic wave resonator in accordance with Example 2-2. FIG. 14C is a graph showing the relationship between Q and frequency for the elastic wave resonator in accordance with Example 2-2. FIG. 15A is a graph showing the relationship between impedance and frequency for the elastic wave resonator in accordance with Example 2-3. FIG. 15B is a graph showing the relationship between the real part of the impedance and frequency for the elastic wave resonator in accordance with Example 2-3. FIG. 15C is a graph showing the relationship between Q and frequency for the elastic wave resonator in accordance with Example 2-3.

[0061] The aspect ratio (Wy1 / Wx1) of the upper electrode 31 in Examples 2-1, 2-2, and 2-3 shown in Figures 13A, 13B, 13C, 14A, 14B, 14C, 15A, 15B, and 15C was set to Wy1 / Wx1 = 1.11. The length Wx1 of the upper electrode 31 in the X direction in Examples 2-1, 2-2, and 2-3 was Wx1 = 54.2 μm. The length Wy1 of the upper electrode 31 in the Y direction was Wy1 = 60.0 μm.

[0062] In Example 2-1 shown in Figures 13A, 13B, and 13C, the width Wx2 of the second portion 33b of the frame electrode 33 in the X direction was 1.5 μm, and the width Wy2 of the first portion 33a in the Y direction was 0.7 μm. In Example 2-2 shown in Figures 14A, 14B, and 14C, the width Wx2 of the second portion 33b of the frame electrode 33 in the X direction was 1.5 μm, and the width Wy2 of the first portion 33a in the Y direction was 1.5 μm. In Example 2-3 shown in Figures 15A, 15B, and 15C, the width Wx2 of the second portion 33b of the frame electrode 33 in the X direction was 0 μm, and the width Wy2 of the first portion 33a in the Y direction was 0 μm. In other words, Example 2-3 was configured without the frame electrode 33.

[0063] As shown in FIGS. 13A, 14A, and 15A, Examples 2-1, 2-2, and 2-3 all have equivalent impedance frequency characteristics.

[0064] 15B, in Example 2-3, which does not have the frame electrode 33, many unwanted responses occur between the resonant frequency and the antiresonant frequency (for example, the region surrounded by the dashed-dotted line D in FIG. 15B) due to a mode (transverse mode) that stands in the planar direction. As shown in FIGS. 13B and 14B, in Examples 2-1 and 2-2, the unwanted responses can be suppressed by providing the frame electrode 33 along the outer periphery of the upper electrode 31.

[0065] Furthermore, in Example 2-2, the width Wy2 of the frame electrode 33 in the Y direction is larger than that of Example 2-1. Therefore, as shown in Fig. 14B , in Example 2-2, ripples occur on the low-frequency side of the resonance frequency (see arrow C in Fig. 14B ). This is because the width Wy2 in the Y direction of the first portion 33a (see Fig. 3 ), which extends along the direction of shear vibration, is large, which increases loss at a certain frequency due to the mode of a standing wave (border ring mode (BRM)) that stands in the frame electrode 33.

[0066] In Example 2-1, the width Wy2 of the frame electrode 33 in the Y direction is smaller than the width Wx2 in the X direction. This makes it possible to reduce ripples that occur on the low-frequency side of the resonant frequency, as indicated by arrow B in Figure 13B. That is, in Example 2-1, by reducing the width Wy2 in the Y direction of the first portion 33a (see Figure 3) that extends along the direction of shear vibration, it is possible to suppress loss due to the boundary ring mode.

[0067] Furthermore, as shown in FIGS. 13C, 14C, and 15C, Examples 2-1 and 2-2 having the frame electrode 33 have a larger Q than Example 2-3 not having the frame electrode 33.

[0068] As described above, it has been shown that ripples on the low frequency side of the resonant frequency can be suppressed by making the width Wx2 in the X direction of the second portion 33b of the frame electrode 33 extending along the Y direction larger than the width Wy2 in the Y direction of the first portion 33a of the frame electrode 33 extending along the X direction.

[0069] Example 3 In Example 3, the connection direction between the upper electrode 31 and the lower electrode 32 and the lead wirings 34 and 35 will be described. FIG. 16 is a plan view showing an elastic wave resonator according to Example 3. FIG. 17 is a graph showing the relationship between impedance and frequency for the elastic wave resonators according to Examples 1-1 and 3. FIG. 18 is a graph showing the relationship between the real part of the impedance and frequency for the elastic wave resonators according to Examples 1-1 and 3. FIG. 19 is a graph showing the relationship between Q and frequency for the elastic wave resonators according to Examples 1-1 and 3.

[0070] 16 , in the elastic wave resonator 10A according to the third embodiment, the lead wiring 34A is connected to one side of the upper electrode 31 in the Y direction (the upper side in FIG. 16 ), and the lead wiring 35A is connected to the other side of the lower electrode 32 in the Y direction (the lower side in FIG. 16 ). That is, in the elastic wave resonator 10A according to the third embodiment, the lead wirings 34A and 35A are connected to the short sides of the resonator and extend in a direction perpendicular to the direction of shear vibration.

[0071] 17 to 19 show the elastic wave resonator 10 according to Example 1-1 together with Example 3. In the elastic wave resonator according to Example 1-1, as described above with reference to FIGS. 1 and 2 , the lead wiring 34 is connected to one end of the upper electrode 31 in the X direction. The lead wiring 35 is connected to the other end of the lower electrode 32 in the X direction. That is, in the elastic wave resonator 10 according to Example 1-1, the lead wirings 34 and 35 are connected to the long sides of the resonator and extend in a direction parallel to the direction of shear vibration.

[0072] The configurations of the upper electrode 31 and the frame electrode 33 of Example 3 are the same as those of Example 1-1. That is, the aspect ratio (Wy1 / Wx1) of the upper electrode 31 of Example 3 is Wy1 / Wx1 = 2.0. The length Wx1 of the upper electrode 31 in the X direction is 40.3 μm, and the length Wy1 in the Y direction is 80.6 μm (see Example 1-1 in Table 1). The width Wx2 of the frame electrode 33 in the X direction is 1.5 μm, and the width Wy2 in the Y direction is 0.7 μm. Other conditions such as film thickness and area are the same as those described in Example 1.

[0073] As shown in FIG. 17, the frequency characteristics of the impedance of Example 3 are substantially the same as those of Example 1-1.

[0074] 18, the real part of the impedance in Example 3 is larger than the real part of the impedance in Example 1-1. That is, in Example 3, the lead wirings 34A and 35A are connected to the short sides of the resonator, so the series resistance of the resonator is larger than that in Example 1-1.

[0075] As shown in FIG. 19, the Q of Example 3 is smaller than the Q of Example 1-1.

[0076] From the above results, it is preferable that the lead-out wirings 34, 35 are connected in the X direction (i.e., the long side of the resonator) of at least one of the upper electrode 31 and the lower electrode 32. It is also preferable that the lead-out wirings 34, 35 are provided extending in a direction parallel to the direction of shear vibration from at least one of the upper electrode 31 and the lower electrode 32. This reduces the resonance resistance, which is correlated with the series resistance of the resonator, and also increases the Q.

[0077] Example 4 In Example 4, the resonator characteristics of the elastic wave resonator 10 will be described when the aspect ratio (Wy1 / Wx1) of the upper electrode 31 is fixed and the area S of the upper electrode 31 is changed. FIG. 20 is a graph showing the relationship between the resonance resistance Zr and the ratio S / t for the elastic wave resonator according to Example 4. FIG. 21 is a graph showing the relationship between the Qmax and the ratio S / t for the elastic wave resonator according to Example 4. FIG. 22 is a graph showing the relationship between the impedance and the frequency for the elastic wave resonator according to Example 4 at different ratios S / t. FIG. 23 is a graph showing the relationship between the real part of the impedance and the frequency for the elastic wave resonator according to Example 4 at different ratios S / t. FIG. 24 is a graph showing the relationship between the Q and the frequency for the elastic wave resonator according to Example 4 at different ratios S / t.

[0078] Table 2 shows the relationship between the dimensions, area, and other configurations of the upper electrode and frame electrode of the elastic wave resonator according to Example 4 and the resonance resistance and Q. In Table 2, fr is the resonance frequency of elastic wave resonator 10, fa is the anti-resonance frequency, Δf is the frequency difference (fa-fr) between the resonance frequency and the anti-resonance frequency, and ΔfR is the fractional bandwidth (fa-fr) / fr of elastic wave resonator 10.

[0079]

[0080] As shown in Table 2, in Examples 4-1 to 4-6, the aspect ratio (Wy1 / Wx1) of the upper electrode 31 is fixed to Wy1 / Wx1=3.0, and the area S of the upper electrode 31 is set to 9747 μm ２ to 303.0 μm ２ The thicknesses of the upper electrode 31 and the frame electrode 33 were varied. In Examples 4-1 to 4-4, the ratio S / t of the area of ​​the upper electrode 31 to the film thickness of the piezoelectric body 20, where S is the area of ​​the upper electrode 31 and t is the film thickness, was 2000 μm or more. In Examples 4-5 and 4-6, the ratio S / t of the area of ​​the upper electrode 31 to the film thickness of the piezoelectric body 20 was less than 2000 μm. The layered structure and film thickness of the upper electrode 31 and the frame electrode 33 were the same as those in Example 1 described above. Note that Figures 20, 21, 22 and Table 2 include variations in resonator characteristics due to processing variations in the manufacturing process.

[0081] The horizontal axis of the graph shown in Fig. 20 is the ratio S / t of the area (S) of the upper electrode 31 to the film thickness (t) of the piezoelectric body 20. The vertical axis is the resonant resistance Zr, which is correlated with the series resistance of the resonator. The horizontal axis of the graph shown in Fig. 21 is the ratio S / t, and the vertical axis is Qmax.

[0082] 20 and 21, when the ratio S / t is smaller than 2000 (Examples 4-5 and 4-6), the resonant resistance Zr increases and Qmax decreases. In contrast, when the ratio S / t is 2000 or more (Examples 4-1 to 4-4), the resonant resistance Zr decreases and Qmax increases.

[0083] 22 , in Examples 4-1 to 4-4 (where the ratio S / t is 2000 or greater), the impedance decreases as the area S of the upper electrode 31 increases, i.e., as the ratio S / t increases. In Examples 4-5 and 4-6 (where the ratio S / t is less than 2000), the resonant frequency fr of the elastic wave resonator 10 shifts to a higher frequency side, and the antiresonant frequency fa shifts to a lower frequency side. That is, Examples 4-1 to 4-4, where the ratio S / t is 2000 or greater, have larger frequency difference Δf and fractional bandwidth ΔfR than Examples 4-5 and 4-6.

[0084] As shown in Fig. 23, the real part of the impedance is smaller in Examples 4-1 to 4-4 (ratio S / t is 2000 or more) than in Examples 4-5 and 4-6 (ratio S / t is less than 2000). Also, as shown in Fig. 24, the Q is larger in Examples 4-1 to 4-4 (ratio S / t is 2000 or more) than in Examples 4-5 and 4-6 (ratio S / t is less than 2000).

[0085] The above results indicate that in Example 4, the ratio S / t of the area S of the upper electrode 31 to the thickness t of the piezoelectric body 20 is preferably 2000 μm or more. This enables the elastic wave resonator 10 to reduce the resonance resistance Zr, which is correlated with the series resistance of the resonator, and to improve the Q factor.

[0086] Example 5 describes the fractional bandwidth ΔfR and the piezoelectric constant when the Euler angles of lithium niobate or lithium tantalate used in the piezoelectric body 20 are varied. Fig. 25 is a graph showing the relationship between the Euler angles and the fractional bandwidth of a piezoelectric body using lithium niobate in an elastic wave resonator according to Example 5-1. In the elastic wave resonator 10 according to Example 5-1, lithium niobate was used as the piezoelectric body 20.

[0087] The horizontal axis of the graph shown in FIG. 25 represents the Euler angle θ of lithium niobate. As shown in FIG. 25 , in elastic wave resonator 10 according to Example 5-1, which utilizes bulk waves in a shear vibration mode, the fractional bandwidth ΔfR of the shear vibration (transverse wave) is larger than the fractional bandwidth ΔfR of the thickness vibration (longitudinal wave). More specifically, as indicated by arrow E1 in FIG. 25 , the Euler angles (φ, θ, ψ) of lithium niobate constituting piezoelectric body 20 are preferably in the range of (φ, θ, ψ) = (0°, 67.5 to 92°, 0°). As a result, elastic wave resonator 10 according to Example 5-1 can achieve a fractional bandwidth ΔfR of 18% or more.

[0088] 25, the Euler angles (φ, θ, ψ) of the lithium niobate constituting piezoelectric body 20 are preferably set in the range of (φ, θ, ψ) = (0°, 67.5 to 79°, 0°). Within this range, the fractional bandwidth ΔfR of the longitudinal wave (thickness direction) is 0.5% or less, and elastic wave resonator 10 in accordance with Example 5-1 can reduce unwanted waves due to longitudinal waves.

[0089] 26 is a graph showing the relationship between the Euler angles and the fractional bandwidth of the piezoelectric body using lithium tantalate in the elastic wave resonator according to Example 5-2. In elastic wave resonator 10 according to Example 5-2, lithium tantalate was used for piezoelectric body 20.

[0090] The horizontal axis of the graph shown in Fig. 26 represents the Euler angle θ of lithium tantalate. As shown in Fig. 26, in elastic wave resonator 10 according to Example 5-2, which utilizes bulk waves in a shear vibration mode, the fractional bandwidth ΔfR of the shear vibration (transverse wave) is larger than the fractional bandwidth ΔfR of the thickness vibration (longitudinal wave). More specifically, as indicated by arrow F1 in Fig. 26, it is preferable that the Euler angles (φ, θ, ψ) of lithium tantalate constituting piezoelectric body 20 be in the range of (φ, θ, ψ) = (0°, 66 to 92.5°, 0°). This allows elastic wave resonator 10 according to Example 5-2 to have a wide fractional bandwidth ΔfR of 7% or more.

[0091] 26, the Euler angles (φ, θ, ψ) of the lithium tantalate constituting piezoelectric body 20 are preferably set in the range of (φ, θ, ψ) = (0°, 67-80°, 0°). In this range, the fractional bandwidth ΔfR of the longitudinal wave (thickness direction) is 0.5% or less, and elastic wave resonator 10 in accordance with Example 5-2 can reduce unwanted waves due to longitudinal waves.

[0092] In Example 5-1, when lithium niobate (transverse wave) is used as the piezoelectric body 20, the piezoelectric constant e ３４ In Example 5-2, when lithium tantalate (transverse wave) is used as the piezoelectric body 20, the piezoelectric constant e ３４ Here, unlike Examples 5-1 and 5-2, in elastic wave resonator 10 using aluminum nitride (AlN) as the material of piezoelectric body 20, longitudinal waves are generally used as the fundamental mode, and the longitudinal piezoelectric constant e ３３ Therefore, the longitudinal piezoelectric constant e of the elastic wave resonator 10 using AlN with longitudinal vibration (longitudinal wave) as the fundamental mode is ３３ On the other hand, the piezoelectric constant e in the slip direction of the elastic wave resonator 10 using lithium niobate or lithium tantalate with shear vibration (transverse wave) as the fundamental mode is ３４ is sufficiently large, a wideband resonator can be obtained.

[0093] The configurations of the above-described embodiments can be combined as appropriate. The specific configurations and numerical values ​​of the embodiments (e.g., the lengths Wx1 and Wy1 of the upper electrode 31, the widths Wx2 and Wy2 of the frame electrode 33, the area S of each electrode, etc.) are merely examples and are not intended to be limiting.

[0094] 27 is a circuit diagram illustrating an acoustic wave filter according to a second embodiment. In the second embodiment, an acoustic wave filter 50 including the acoustic wave resonator 10 according to the first embodiment or the acoustic wave resonator 10 according to any of the examples will be described.

[0095] 27 , the elastic wave filter 50 according to the second embodiment includes a plurality of series arm resonators 61, 62, 63, and 64, a plurality of parallel arm resonators 65, 66, and 67, and inductors 68A and 68B. At least one of the plurality of series arm resonators 61, 62, 63, and 64 and the plurality of parallel arm resonators 65, 66, and 67 is the elastic wave resonator 10 according to the first embodiment or any one of the elastic wave resonators 10 according to each of the examples. That is, at least one of the plurality of series arm resonators 61, 62, 63, and 64 is the above-described elastic wave resonator 10, and the aspect ratio (Wy1 / Wx1) of the upper electrode 31 of at least one of the plurality of series arm resonators 61, 62, 63, and 64 is greater than 1. At least one of the parallel arm resonators 65, 66, and 67 is the elastic wave resonator 10 described above, and the aspect ratio (Wy1 / Wx1) of the upper electrode 31 of at least one of the parallel arm resonators 65, 66, and 67 is greater than one.

[0096] The plurality of series arm resonators 61, 62, 63, and 64 are connected in series to a signal path between an input terminal 60A and an output terminal 60B. The plurality of parallel arm resonators 65, 66, and 67 are connected in parallel between the signal path between the input terminal 60A and the output terminal 60B and grounds 69A, 69B, and 69C. The acoustic wave filter 50 according to the second embodiment is a so-called ladder filter.

[0097] One terminal of each of the series-connected series arm resonators 61, 62, 63, and 64 is electrically connected to an input terminal 60A, and the other terminal is electrically connected to an output terminal 60B. One terminal of a parallel arm resonator 65 is electrically connected to a signal path connecting the series arm resonators 61 and 62, and the other terminal is electrically connected to ground 69A via an inductor 68A. One terminal of a parallel arm resonator 66 is electrically connected to a signal path connecting the series arm resonators 62 and 63, and the other terminal is electrically connected to ground 69B. One terminal of a parallel arm resonator 67 is electrically connected to a signal path connecting the series arm resonators 63 and 64, and the other terminal is electrically connected to ground 69C via an inductor 68B.

[0098] The inductor 68A is connected in series to a signal path connecting the parallel arm resonator 65 and ground 69A. The inductor 68B is connected in series to a signal path connecting the parallel arm resonator 67 and ground 69C.

[0099] The acoustic wave filter 50 may include capacitors or the like as impedance elements, without being limited to the inductors 68A and 68B. Furthermore, the impedance elements, such as the inductors 68A and 68B and the capacitors, are not limited to being connected to the parallel arm resonators 65, 66, and 67, but may be connected to the series arm resonators 61, 62, 63, and 64. Furthermore, the impedance elements, such as the inductors 68A and 68B and the capacitors, may be connected to switch elements. In this case, the acoustic wave filter 50 can vary the frequency of the filter characteristics by switching the switch elements on and off.

[0100] The series arm resonators 61, 62, 63, and 64 are each configured to include a plurality of resonators s1, s2, s3, and s4 divided in series. The number of divisions in each of the series arm resonators 61, 62, 63, and 64 is an even number. The number of divisions in each of the series arm resonators 61, 62, 63, and 64 is not limited to two, and may be zero or four or more. In the following description, "divided in series" refers to a configuration in which a plurality of resonators having the same resonant frequency are connected in series. Furthermore, the description of "divided in series" is not limited to the series arm resonators 61, 62, 63, and 64, but also applies to the parallel arm resonators 65, 66, and 67.

[0101] Each of the parallel arm resonators 65, 66, and 67 includes a plurality of resonators p1, p2, and p3 that are divided in series. The number of divisions in each of the parallel arm resonators 65, 66, and 67 is an even number. The number of divisions in each of the parallel arm resonators 65, 66, and 67 is not limited to two, and each of the parallel arm resonators 65, 66, and 67 may have no divisions or four or more divisions.

[0102] 27 , all of the series arm resonators 61, 62, 63, and 64 and all of the parallel arm resonators 65, 66, and 67 are divided in series. However, this is not limiting, and it is sufficient that at least the series arm resonator 64 closest to the output terminal 60B among the multiple series arm resonators 61, 62, 63, and 64 is divided in series. Alternatively, it is sufficient that at least the parallel arm resonator 67 closest to the output terminal 60B among the multiple parallel arm resonators 65, 66, and 67 is divided in series.

[0103] In this embodiment, the plurality of series arm resonators 61, 62, 63, and 64 and the plurality of parallel arm resonators 65, 66, and 67 are divided in series, so that when the impedance of the resonant circuit is high, the ratio (S / t) of the area S of one of the upper electrode 31 and the lower electrode 32 to the thickness t of the piezoelectric body 20 increases, thereby improving the Q. Alternatively, the plurality of series arm resonators 61, 62, 63, and 64 and the plurality of parallel arm resonators 65, 66, and 67 have a smaller power density per unit area, thereby improving the power handling performance.

[0104] The plurality of series arm resonators 61, 62, 63, and 64 and the plurality of parallel arm resonators 65, 66, and 67 are not limited to being divided in series, but may be divided in parallel. In this case, particularly when the impedance of the resonant circuit is low, dividing them in parallel can prevent the area of ​​the recess 14 (see FIG. 2) from becoming larger, thereby preventing a decrease in the mechanical strength of each resonator.

[0105] The configurations and numbers of the series arm resonators 61, 62, 63, and 64 and the parallel arm resonators 65, 66, and 67 in the acoustic wave filter 50 can be changed as appropriate depending on the required filter characteristics. For example, the acoustic wave filter 50 may include at least one series arm resonator and at least one parallel arm resonator.

[0106] FIG. 28 is a cross-sectional view schematically illustrating the configuration of an acoustic wave filter according to a second embodiment. FIG. 29 is a plan view schematically illustrating the configuration of a resonator chip in the acoustic wave filter according to the second embodiment. FIG. 30 is a plan view schematically illustrating the configuration of a series arm resonator in FIG. 29. FIG. 31 is a cross-sectional view taken along XXXI-XXXI' in FIG. 30. FIG. 32 is a plan view schematically illustrating the front surface of a module substrate in the acoustic wave filter according to the second embodiment. FIG. 33 is a plan view schematically illustrating inner layers of the module substrate in the acoustic wave filter according to the second embodiment. FIG. 34 is a plan view schematically illustrating the rear surface of a module substrate in the acoustic wave filter according to the second embodiment.

[0107] 28 , an acoustic wave filter 50 according to the second embodiment includes a resonator chip 51, a module substrate 52, bumps 55, and a sealing resin 56. The resonator chip 51 is mounted on the module substrate 52 via the bumps 55. The resonator chip 51 includes a plurality of series arm resonators 61, 62, 63, and 64 and a plurality of parallel arm resonators 65, 66, and 67, etc., as shown in FIG.

[0108] The module substrate 52 is a laminated substrate having a plurality of dielectric layers 53 and 54. The module substrate 52 may be, for example, a printed circuit board made of resin or a ceramic substrate such as LTCC (Low Temperature Co-fired Ceramics) or HTCC (High Temperature Co-fired Ceramics). The module substrate 52 is not limited to the two dielectric layers 53 and 54, and may have three or more dielectric layers, or may be a single-layer substrate.

[0109] 29 , the resonator chip 51 has a plurality of series arm resonators 61, 62, 63, and 64, a plurality of parallel arm resonators 65, 66, and 67, and a plurality of terminals (an input terminal 60A, an output terminal 60B, and ground terminals 69A, 69B, 69C, and 69D) provided on a support member 13A. The input terminal 60A and the output terminal 60B are located at diagonally opposite corners of the support member 13A. The ground terminals 69A, 69B, 69C, and 69D are located on the periphery of the support member 13A. The connections of the plurality of series arm resonators 61, 62, 63, and 64, the plurality of parallel arm resonators 65, 66, and 67, and the plurality of terminals (the input terminal 60A, the output terminal 60B, and the ground terminals 69A, 69B, 69C, and 69D) are the same as those in FIG. 27 , and therefore, repeated description will be omitted. The through holes 15 are provided to etch the sacrificial layer when forming the recesses 14A. The positions, number, etc. of the through holes 15 are not limited to the example shown in Fig. 29 and can be changed as appropriate. Furthermore, the through holes 15 are omitted from the illustration of the above-described embodiment.

[0110] 30 and 31 show an enlarged view of the configuration of the series arm resonator 64 of the multiple resonators included in the resonator chip 51. That is, Fig. 30 and 31 show the configuration of the series arm resonator 64 located on the output terminal 60B side of the multiple resonators. However, the configurations of the other resonators are similar to the series arm resonator 64 shown in Fig. 30 and 31, and the explanation of the configuration of the series arm resonator 64 in Fig. 30 and 31 can also be applied to the configurations of the other resonators.

[0111] As shown in FIG. 31 , the support member 13A includes a support substrate 11A and an intermediate layer 12A. A recess 14A (hollow portion) is formed on the surface of the support member 13A (intermediate layer 12A) facing the second main surface 20Ab of the piezoelectric body 20A. The recess 14A is shared by two resonators s4 that constitute the series arm resonator 64. In other words, one recess 14A is provided for each of the two resonators s4. The support member 13A, the piezoelectric body 20A, and each electrode may be made of the materials described in the first embodiment. A through-hole 15 is provided in the region of the piezoelectric body 20A that overlaps with the recess 14A.

[0112] 30 and 31 , each of the two resonators s4 constituting the series arm resonator 64 includes an upper electrode 31, a lower electrode 32, and a piezoelectric body 20A. The upper electrodes 31 of the two resonators s4 are provided on the first main surface 20Aa of the piezoelectric body 20A, and are spaced apart in the X direction.

[0113] The lower electrode 32 is provided in common to the two resonators s4 and is provided on the second main surface 20Ab of the piezoelectric body 20A. In other words, one region in the X direction of the lower electrode 32 (the right-hand portion in FIG. 31 ) faces the upper electrode 31 of one of the resonators s4 across the piezoelectric body 20A. The other region in the X direction of the lower electrode 32 (the left-hand portion in FIG. 31 ) faces the upper electrode 31 of the other resonator s4 across the piezoelectric body 20A.

[0114] The frame electrode 33 is provided on the outer periphery of each of the upper electrodes 31 of the two resonators s4. The lead-out wiring 34A is connected to the upper electrode 31 of one of the resonators s4. The lead-out wiring 34B is connected to the upper electrode 31 of the other resonator s4. The lead-out wiring 34A and the lead-out wiring 34B extend in opposite directions to each other in the X direction.

[0115] In the acoustic wave filter 50 using BAW resonators, a second harmonic spectrum may be output due to nonlinear operation of the BAW resonators. In the acoustic wave filter 50, the second harmonic spectrum of each resonator is attenuated by the output-side resonator and output from the output terminal 60B. However, the second harmonic spectrum of a resonator close to the output terminal 60B (e.g., the series arm resonator 64) may be output from the output terminal 60B with almost no attenuation.

[0116] In this embodiment, among the multiple resonators, at least the series arm resonator 64 located closest to the output terminal 60B has two resonators s4 split in series, or alternatively, among the multiple resonators, at least the parallel arm resonator 67 located closest to the output terminal 60B has two resonators p3 split in series.

[0117] As a result, for example, if a resonator is divided into n parts in series (n is an integer), the energy density will be n ２ Therefore, in this embodiment, the nonlinear effect is reduced by 6 dB compared to the configuration without division.

[0118] Furthermore, since the series arm resonator 64 is divided into an even number, the upper electrode 31 and the leading wiring 34A of the input-side resonator s4 and the upper electrode 31 and the leading wiring 34A of the output-side resonator s4 are formed in the same layer. Therefore, compared to when the series arm resonator 64 is divided into an odd number, a via hole for connecting the lower electrode 32 and the first main surface 20Aa of the piezoelectric body 20A is not required, thereby reducing manufacturing costs.

[0119] 30 and 31, the relationship between the voltages of the resonators s4 is indicated by arrows G1 and G2, the relationship between the polarization axes of the piezoelectric bodies 20 is indicated by arrows G3 and G4, and the direction of displacement of the piezoelectric bodies 20 is indicated by arrows G5 and G6. In this embodiment, since the number of divisions of the series arm resonator 64 is even, the relationship between the voltage and polarization axis of one resonator s4 (e.g., the right side in FIGS. 30 and 31) (see arrows G1 and G3) is opposite to the relationship between the voltage and polarization axis of the other resonator (e.g., the left side in FIGS. 30 and 31) (see arrows G2 and G4). This cancels out the second-order nonlinear signal, thereby reducing the second-order harmonic spectrum.

[0120] It is preferable that the two resonators s4 of the series arm resonator 64 divided in series have the same resonant frequency and the same impedance (the same damping capacitance), so that the nonlinear signals of the series-connected resonators s4 have the same magnitude and cancel out the second-order nonlinear signals.

[0121] 32, the module substrate 52 has a plurality of connection pads 57 and vias 58A. The plurality of connection pads 57 are electrically connected to the input terminal 60A, output terminal 60B, and grounds 69A, 69B, 69C, and 69D of the resonator chip 51 via bumps 55. The plurality of connection pads 57 are also electrically connected to the inner layer and back surface side of the module substrate 52 via vias 58A.

[0122] 33, inductors 68A and 68B are formed in an inner layer of the module substrate 52. One end of the inductors 68A and 68B is electrically connected to the front surface side of the module substrate 52 through the connection pad 57 and the via 58A (see FIG. 32), respectively, and the other end is electrically connected to the back surface side of the module substrate 52 through the via 58B.

[0123] 34, a plurality of connection pads 59 are provided on the back surface of the module substrate 52. The acoustic wave filter 50 is mounted on an external device such as a high-frequency front-end circuit 101 (see FIG. 39) through the plurality of connection pads 59.

[0124] Fig. 35 is a plan view showing the configuration of a series arm resonator according to a fifth modification. In the examples shown in Figs. 30 and 31, one recess 14 is formed in each of the two series-divided resonators s4 of the series arm resonator 64, but this is not limiting. As shown in Fig. 35, in a series arm resonator 64A according to the fifth modification, recesses 14a and 14b are provided in each of the two series-divided resonators s4.

[0125] The two recesses 14a, 14b are spaced apart in the X direction. The upper electrode 31 of one resonator s4 of the series arm resonator 64A (e.g., on the right side in FIG. 35 ) is arranged to overlap one recess 14a. The upper electrode 31 of the other resonator s4 of the series arm resonator 64A (e.g., on the left side in FIG. 35 ) is arranged to overlap the other recess 14b. The lower electrode 32 is provided continuously across the two recesses 14a, 14b.

[0126] In the fifth modification, the portion of the lower electrode 32 located between the two recesses 14 a and 14 b contacts the support member 13A (intermediate layer 12A), which improves the heat dissipation effect from the lower electrode 32 to the support member 13A and improves the power resistance.

[0127] 36 is a graph showing the filter characteristics of an acoustic wave filter according to Example 6-1. Table 3 shows an example of the configuration of each resonator of the acoustic wave filter according to Example 6-1.

[0128]

[0129] As shown in Table 3, in the acoustic wave filter 50 in accordance with Example 6-1, the aspect ratio (Wy1 / Wx1) of the upper electrodes 31 of the series arm resonators 61, 62, 63, and 64 (resonators s1, s2, s3, and s4) is greater than the aspect ratio (Wy1 / Wx1) of the upper electrodes 31 of the parallel arm resonators 65, 66, and 67 (resonators p1, p2, and p3). The aspect ratio (Wy1 / Wx1) of the upper electrodes 31 of the series arm resonators 61, 62, 63, and 64 (resonators s1, s2, s3, and s4) is 3.0. The aspect ratio (Wy1 / Wx1) of the upper electrodes 31 of the parallel arm resonators 65, 66, and 67 (resonators p1, p2, and p3) is 2.0.

[0130] Furthermore, a single crystal of lithium niobate was used as the material for the piezoelectric body 20A. The Euler angles (φ, θ, ψ) of the lithium niobate constituting the piezoelectric body 20A were (φ, θ, ψ) = (0°, 73°, 0°). As shown in Table 3, in the series arm resonators 61, 62, 63, and 64 (resonators s1, s2, s3, and s4) and the parallel arm resonators 65, 66, and 67 (resonators p1, p2, and p3), the ratio (S / t) of the area S of the upper electrode 31 to the thickness t of the piezoelectric body 20 was 2000 μm or greater.

[0131] In the acoustic wave filter 50 in accordance with the preferred embodiment 6-1, the number of divisions of each of the series arm resonators 61, 62, 63, and 64 (resonators s1, s2, s3, and s4) and the parallel arm resonators 65, 66, and 67 (resonators p1, p2, and p3) is an even number.

[0132] The film thickness of the piezoelectric body 20 is constant for the series arm resonators 61, 62, 63, and 64 (resonators s1, s2, s3, and s4) and the parallel arm resonators 65, 66, and 67 (resonators p1, p2, and p3). However, the present invention is not limited to this, and the film thickness of each resonator may be different depending on the desired filter characteristics.

[0133] The series arm resonators 61, 62, 63, and 64 (resonators s1, s2, s3, and s4) and the parallel arm resonators 65, 66, and 67 (resonators p1, p2, and p3) share the same material for the upper electrode 31, the lower electrode 32, and the frame electrode 33. However, the thickness of the Pt film in the series arm resonators 61, 62, 63, and 64 (resonators s1, s2, s3, and s4) is thinner than the thickness of the Pt film in the parallel arm resonators 65, 66, and 67 (resonators p1, p2, and p3).

[0134] As shown in FIG. 36, the acoustic wave filter 50 in accordance with Example 6-1 has a loss of 2.25 dB or less in the band indicated by the arrow H1 (n77 band: 3300 MHz or more and 4200 MHz or less).

[0135] Furthermore, the acoustic wave filter 50 in accordance with Example 6-1 achieves an attenuation of 25 dB or more in the band indicated by the arrow H2 (LTE band: 2690 MHz or less).

[0136] Furthermore, the acoustic wave filter 50 according to Example 6-1 achieves attenuation of 30 dB or more in the band indicated by arrow H3 (n79 band: 4400 MHz or more and 5000 MHz or less) and the band indicated by arrow H4 (WiFi7 band: 5150 MHz or more and 7125 MHz or less).

[0137] As described above, it has been shown that the acoustic wave filter 50 in accordance with Example 6-1 has excellent filter characteristics.

[0138] Next, the relationship between the aspect ratio (Wy1 / Wx1) of the upper electrode 31 of the series arm resonators 61, 62, 63, and 64 (resonators s1, s2, s3, and s4) and the parallel arm resonators 65, 66, and 67 (resonators p1, p2, and p3) in the acoustic wave filter 50 and the filter characteristics will be described.

[0139] 37 is a graph showing the relationship between the aspect ratio and the relative bandwidth of an elastic wave resonator included in an elastic wave filter in accordance with Example 6. The horizontal axis of the graph shown in FIG. 37 represents the aspect ratio (Wy1 / Wx1) of the upper electrode 31. The horizontal axis of the graph also represents the relative bandwidth of the elastic wave resonator 10. Note that the aspect ratio (Wy1 / Wx1) of the elastic wave resonator 10 in FIG. 37 and various conditions such as the dimensions and area of ​​the upper electrode 31 are the same as those in Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-3 shown in Table 1.

[0140] As shown in FIG. 37, the fractional bandwidth ΔfR tends to decrease as the aspect ratio (Wy1 / Wx1) of the upper electrode 31 of the acoustic wave resonator 10 increases.

[0141] FIG. 38 is a graph showing the filter characteristics of elastic wave filters 50 according to Examples 6-1 and 6-2. The elastic wave filter 50 according to Example 6-1 shown in FIG. 38 has the same filter configuration and filter characteristics as those shown in FIG. 36 . Unlike Example 6-1, the elastic wave filter 50 according to Example 6-2 has the same aspect ratio (Wy1 / Wx1) of the upper electrodes 31 of the series arm resonators 61, 62, 63, and 64 (resonators s1, s2, s3, and s4) as the parallel arm resonators 65, 66, and 67 (resonators p1, p2, and p3). The aspect ratios (Wy1 / Wx1) of the upper electrodes 31 of the resonators s1, s2, s3, and s4 and the resonators p1, p2, and p3 are all 3.0.

[0142] 38 , the acoustic wave filter 50 according to Example 6-1 has approximately 3 dB greater attenuation than Example 6-2 in the band indicated by arrow H2 (LTE band: 2690 MHz or less). Also, the acoustic wave filter 50 according to Example 6-1 has approximately 3 dB greater attenuation than Example 6-2 in the band indicated by arrow H3 (n79 band: 4400 MHz or more and 5000 MHz or less).

[0143] This is because the fractional bandwidth ΔfR of the parallel arm resonators 65, 66, and 67 in Example 6-1 is larger than that in Example 6-2 (that is, the aspect ratio (Wy1 / Wx1) of the upper electrode 31 is smaller).

[0144] As described above, it has been shown that the acoustic wave filter according to Example 6-1 can improve the filter characteristics compared to Example 6-2 by making the aspect ratio (Wy1 / Wx1) of the upper electrodes 31 of the series arm resonators 61, 62, 63, and 64 (resonators s1, s2, s3, and s4) larger than the aspect ratio (Wy1 / Wx1) of the upper electrodes 31 of the parallel arm resonators 65, 66, and 67 (resonators p1, p2, and p3).

[0145] (Third embodiment) Figure 39 is a diagram showing the configuration of a communication device according to a third embodiment. The communication device 100 according to the third embodiment is, for example, a mobile terminal such as a mobile phone, a smartphone, or a tablet terminal, or a personal computer equipped with a communication function. Alternatively, the communication device 100 may be a backhaul communication device that performs communication between base stations and communication between a base station and a core network.

[0146] As shown in FIG. 39, a communication device 100 includes a high-frequency front-end circuit 101, an antenna 102, an RF-IC (Radio Frequency Integrated Circuit) 104, and a BB-IC (Baseband Integrated Circuit) 105.

[0147] The BB-IC 105 constitutes a baseband signal processing circuit and supplies a baseband signal to the RF-IC 104. The RF-IC 104 performs high-frequency signal processing of transmission and reception signals.

[0148] The high-frequency front-end circuit 101 is connected between the antenna 102 and the RF-IC 104. In the communication device 100, a high-frequency transmission signal is output from the high-frequency front-end circuit 101 to the antenna 102, and a high-frequency reception signal from the antenna 102 can be received by the high-frequency front-end circuit 101.

[0149] Specifically, the high-frequency front-end circuit 101 includes a switch SW, power amplifiers 111a and 111b, matching circuits 112a and 112b, transmit filters 113a and 113b, a multiplexer 114, matching circuits 115a and 115b, and low-noise amplifiers 116a and 116b.

[0150] When transmitting a high-frequency signal, the switch SW is switched to the side of the transmission filter 113a or the transmission filter 113b. The high-frequency transmission signal output from the RF-IC 104 is amplified by the power amplifier 111a or the power amplifier 111b, and input to the transmission filter 113a or the transmission filter 113b through the matching circuits 112a, 112b.

[0151] The band of the transmit filter 113a is, for example, n77 of the 5G NR (New Radio) standard. The frequency range of n77 of 5G NR is 3.3 GHz or higher and 4.2 GHz or lower. The band of the transmit filter 113b is, for example, n79 of the 5G NR standard. The frequency range of n79 of 5G NR is 4.4 GHz or higher and 5.0 GHz or lower.

[0152] The high frequency transmission signal that has passed through the transmission filter 113 a or 113 b is fed to the antenna 102 .

[0153] When receiving a high-frequency signal, the switch SW is switched to the side of the multiplexer 114. The multiplexer 114 includes receive filters 117a and 117b and a matching circuit 118. In the multiplexer 114, the input terminals of the plurality of receive filters 117a and 117b are electrically connected via the matching circuit 118. The band of the receive filter 117a is, for example, n77 of the 5G NR standard. The band of the receive filter 117b is, for example, n79 of the 5G NR standard.

[0154] A received signal from the antenna 102 passes through the receiving filter 117a or 117b via the matching circuit 118. The high-frequency received signal that has passed through the receiving filter 117a or 117b is transmitted to the RF-IC 104 via the matching circuits 115a, 115b and the low-noise amplifier 116a or 116b.

[0155] In the communication device 100 of this embodiment, at least one of the transmit filters 113a and 113b is an acoustic wave filter 50 including the above-described acoustic wave resonator 10. In addition, in the multiplexer 114, at least one of the receive filters 117a and 117b is an acoustic wave filter 50 including the above-described acoustic wave resonator 10. The high-frequency front-end circuit 101 includes the transmit filters 113a and 113b and at least one of the receive filters 117a and 117b of the multiplexer 114. In addition, the communication device 100 includes the high-frequency front-end circuit 101.

[0156] Note that the configuration of the communication device 100 shown in Figure 39 is merely a schematic diagram and can be modified as appropriate. Furthermore, the bands of the transmit filters 113a and 113b and the receive filters 117a and 117b are merely examples, and other communication standards can also be applied. The configuration of the multiplexer 114 is merely an example and can be modified as appropriate. For example, the output terminals of the multiple filters included in the multiplexer 114 may be electrically connected to each other depending on the device in which it is installed.

[0157] The above-described embodiment is intended to facilitate understanding of the present invention, and is 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.

[0158] The present disclosure may also have the following configurations.

[0159] (1) An elastic wave resonator that utilizes bulk waves in a shear vibration mode, comprising: a piezoelectric body; an upper electrode provided on the piezoelectric body; and a lower electrode provided below the piezoelectric body, wherein, when a direction parallel to a surface of the piezoelectric body and parallel to a direction of shear vibration is defined as a first direction, and a direction parallel to the surface of the piezoelectric body and perpendicular to the direction of shear vibration is defined as a second direction, an aspect ratio (Wy1 / Wx1) of at least one of the upper electrode and the lower electrode, which is a ratio of a length (Wx1) in the first direction to a length (Wy1) in the second direction, is greater than 1. (2) The elastic wave resonator according to (1), wherein the aspect ratio (Wy1 / Wx1) is 3 or greater. (3) The elastic wave resonator according to (1) or (2), further comprising: a frame electrode provided on the outer periphery of at least one of the upper electrode and the lower electrode; wherein a width (Wx2) in the first direction of a portion of the frame electrode extending along the second direction is greater than a width (Wy2) in the second direction of a portion of the frame electrode extending along the first direction. (4) The elastic wave resonator according to any one of (1) to (3), further comprising: a lead-out wiring connected in the first direction to at least one of the upper electrode and the lower electrode. (5) The elastic wave resonator according to any one of (1) to (4), further comprising: a ratio (S / t) of an area (S) of one of the upper electrode and the lower electrode to a film thickness (t) of the piezoelectric body is 2000 μm or greater. (6) The elastic wave resonator according to any one of (1) to (5), further comprising: a piezoelectric body including lithium niobate or lithium tantalate. (7) The elastic wave resonator according to any one of (1) to (5), wherein the piezoelectric body contains lithium niobate, and the lithium niobate constituting the piezoelectric body has Euler angles (φ, θ, ψ) in the ranges of (φ, θ, ψ) = (0°, 67.5 to 92°, 0°). (8) The elastic wave resonator according to any one of (1) to (5), wherein the piezoelectric body contains lithium niobate, and the lithium niobate constituting the piezoelectric body has Euler angles (φ, θ, ψ) in the ranges of (φ, θ, ψ) = (0°, 67.5 to 79°, 0°).(9) The elastic wave resonator according to any one of (1) to (5), wherein the piezoelectric body includes lithium tantalate, and the Euler angles (φ, θ, ψ) of the lithium tantalate constituting the piezoelectric body are in the ranges of (φ, θ, ψ) = (0°, 66 to 92.5°, 0°). (10) The elastic wave resonator according to any one of (1) to (5), wherein the piezoelectric body includes lithium tantalate, and the Euler angles (φ, θ, ψ) of the lithium tantalate constituting the piezoelectric body are in the ranges of (φ, θ, ψ) = (0°, 67 to 80°, 0°). (11) An elastic wave filter comprising the elastic wave resonator according to any one of (1) to (10). (12) The elastic wave filter according to (11), comprising a series arm resonator and a parallel arm resonator, wherein at least the series arm resonator of the series arm resonator and the parallel arm resonator includes the elastic wave resonator, and the aspect ratio (Wy1 / Wx1) of the series arm resonator is greater than 1. (13) The elastic wave filter according to (12), wherein the parallel arm resonator includes the elastic wave resonator, and the aspect ratio (Wy1 / Wx1) of the parallel arm resonator is greater than 1. (14) The elastic wave filter according to (13), wherein the aspect ratio of the series arm resonator is equal to or greater than the aspect ratio of the parallel arm resonator. (15) The elastic wave filter according to any one of (11) to (14), including an input terminal, an output terminal, a plurality of series arm resonators and a plurality of parallel arm resonators connected between the input terminal and the output terminal, wherein the series arm resonator closest to the output terminal among the plurality of series arm resonators is divided in series, and the number of divisions of the series arm resonator is an even number. (16) The elastic wave filter according to any one of (11) to (15), including an input terminal, an output terminal, a plurality of series arm resonators and a plurality of parallel arm resonators connected between the input terminal and the output terminal, wherein the parallel arm resonator closest to the output terminal among the plurality of parallel arm resonators is divided in series, and the number of divisions of the parallel arm resonator is an even number. (17) A multiplexer, including a plurality of filters including the elastic wave filter according to any one of (11) to (16), wherein one of the input terminal and one of the output terminal of each of the plurality of filters are electrically connected to each other.(18) A high-frequency front-end circuit comprising the acoustic wave filter according to any one of (11) to (16). (19) A high-frequency front-end circuit comprising the multiplexer according to (17). (20) A communication device comprising the high-frequency front-end circuit according to (18) or (19).

[0160] 10, 10A Acoustic wave resonator 11, 11A Support substrate 12, 12A Intermediate layer 13, 13A Support member 14, 14a, 14b, 14A Recess 20, 20A Piezoelectric body 20a, 20Aa First main surface 20b, 20Ab Second main surface 31 Upper electrode 32 Lower electrode 33, 33A, 33B, 33C Frame electrode 33a, 33Ba, 33Ca First portion 33b, 33Bb, 33Cb Second portion 33Cc Third portion 34, 34A, 34B, 35, 35A Lead wiring 50 Acoustic wave filter 51 Resonator chip 52 Module substrate 53, 54 Dielectric layer 55 Bump 56 Sealing resin 61, 62, 63, 64, 64A Series arm resonators 65, 66, 67 Parallel arm resonators 100 Communication device 101 High frequency front end circuit Wx1, Wy1 Length Wx2, Wy2 Width

Claims

1. An elastic wave resonator that utilizes bulk waves in a shear vibration mode, comprising: a piezoelectric body; an upper electrode provided on the piezoelectric body; and a lower electrode provided below the piezoelectric body, wherein when a direction parallel to the surface of the piezoelectric body and parallel to the direction of shear vibration is defined as a first direction, and a direction parallel to the surface of the piezoelectric body and perpendicular to the direction of shear vibration is defined as a second direction, the aspect ratio (Wy1 / Wx1) of at least one of the upper electrode and the lower electrode, which is the ratio of the length in the first direction (Wx1) to the length in the second direction (Wy1), is greater than 1.

2. The elastic wave resonator according to claim 1, wherein the aspect ratio (Wy1 / Wx1) is 3 or greater.

3. The elastic wave resonator according to claim 1 or 2, further comprising a frame electrode provided on the outer periphery of at least one of the upper electrode and the lower electrode, wherein the width (Wx2) in the first direction of a portion of the frame electrode extending along the second direction is greater than the width (Wy2) in the second direction of the portion of the frame electrode extending along the first direction.

4. The elastic wave resonator according to any one of claims 1 to 3, further comprising: a lead-out wiring connected in the first direction to at least one of the upper electrode and the lower electrode.

5. An elastic wave resonator according to any one of claims 1 to 4, wherein the ratio (S / t) of the area (S) of one of the upper electrode and the lower electrode to the film thickness (t) of the piezoelectric body is 2000 µm or more.

6. An elastic wave resonator according to any one of claims 1 to 5, wherein the piezoelectric element contains lithium niobate or lithium tantalate.

7. The elastic wave resonator according to any one of claims 1 to 5, wherein the piezoelectric body contains lithium niobate, and the Euler angles (φ, θ, ψ) of the lithium niobate constituting the piezoelectric body are in the range of (φ, θ, ψ) = (0°, 67.5 to 92°, 0°).

8. The elastic wave resonator according to any one of claims 1 to 5, wherein the piezoelectric body contains lithium niobate, and the Euler angles (φ, θ, ψ) of the lithium niobate constituting the piezoelectric body are in the range of (φ, θ, ψ) = (0°, 67.5 to 79°, 0°).

9. The elastic wave resonator according to any one of claims 1 to 5, wherein the piezoelectric body contains lithium tantalate, and the Euler angles (φ, θ, ψ) of the lithium tantalate constituting the piezoelectric body are in the range of (φ, θ, ψ) = (0°, 66 to 92.5°, 0°).

10. The elastic wave resonator according to any one of claims 1 to 5, wherein the piezoelectric body contains lithium tantalate, and the Euler angles (φ, θ, ψ) of the lithium tantalate constituting the piezoelectric body are in the range of (φ, θ, ψ) = (0°, 67 to 80°, 0°).

11. An acoustic wave filter comprising an acoustic wave resonator according to any one of claims 1 to 10.

12. The acoustic wave filter according to claim 11, comprising a series arm resonator and a parallel arm resonator, wherein at least the series arm resonator of the series arm resonator and the parallel arm resonator includes the acoustic wave resonator, and the aspect ratio (Wy1 / Wx1) of the series arm resonator is greater than 1.

13. The acoustic wave filter according to claim 12, wherein the parallel arm resonator includes the acoustic wave resonator, and the aspect ratio (Wy1 / Wx1) of the parallel arm resonator is greater than 1.

14. The acoustic wave filter according to claim 13, wherein the aspect ratio of the series arm resonator is equal to or greater than the aspect ratio of the parallel arm resonator.

15. The acoustic wave filter according to any one of claims 11 to 14, comprising an input terminal, an output terminal, a plurality of series arm resonators connected between the input terminal and the output terminal, and a plurality of parallel arm resonators, wherein the series arm resonator closest to the output terminal among the plurality of series arm resonators is divided in series, and the number of divisions of the series arm resonator is an even number.

16. The acoustic wave filter according to any one of claims 11 to 15, comprising an input terminal, an output terminal, a plurality of series arm resonators and a plurality of parallel arm resonators connected between the input terminal and the output terminal, wherein the parallel arm resonator closest to the output terminal among the plurality of parallel arm resonators is configured by being divided in series, and the number of divisions of the parallel arm resonator is an even number.

17. A multiplexer comprising a plurality of filters, each including an acoustic wave filter according to any one of claims 11 to 16, wherein one of the input terminal and one of the output terminal of each of the plurality of filters are electrically connected to each other.

18. A high-frequency front-end circuit comprising an acoustic wave filter according to any one of claims 11 to 16.

19. A high frequency front-end circuit comprising the multiplexer according to claim 17.

20. A communication device comprising the high-frequency front-end circuit according to claim 18 or 19.

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