Acoustic wave resonator, filter device, and communication apparatus

Abstract

To provide an elastic wave resonator, a filter device, and a communication device which are improved in power resistance and distortion characteristics.SOLUTION: The elastic wave resonator 10 is a split elastic wave resonator including a first resonator 1, a second resonator 2, and a third resonator 3 that are connected in series, and the first, second, and third resonators include a first electrode 11 having first, second, and third IDT electrodes 111, 211, and 311 including a plurality of first, second, and third electrode fingers 112, 212, and 312, respectively, and first and second reflectors 12 and 22 located on both sides of the first, second, and third IDT electrodes in an arrangement direction of the first electrode fingers. The second resonator is located between the first resonator and the third resonator, and the first, second, and third reflectors have a single pattern. An anti-resonant frequency obtained from the pitch and duty of the second electrode fingers is higher than an anti-resonant frequency obtained from the pitch and duty of the first electrode fingers and an anti-resonant frequency obtained from the pitch and duty of the third electrode fingers.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an acoustic wave resonator, which is an electronic component that utilizes acoustic waves, a filter device including the acoustic wave resonator, and a communication device including the acoustic wave resonator. [Background technology]

[0002] An elastic wave resonator having electrodes divided in series can have improved power durability. Patent Document 1 discloses an elastic wave resonator in which a first divided resonator and a second divided resonator divided in series are provided on a main surface of a piezoelectric substrate, and the reflector of the first divided resonator and the reflector of the second divided resonator are shared. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6004143 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a need for acoustic wave resonators, filter devices and communication devices that have good power handling and distortion characteristics. [Means for solving the problem]

[0005] (1) According to an embodiment of the present disclosure, there is provided an elastic wave resonator that is a split elastic wave resonator including a first resonator, a second resonator, and a third resonator connected in series, wherein the first resonator includes a first electrode having a first IDT electrode including a plurality of first electrode fingers, and first reflectors located on both sides of the first IDT electrode in an arrangement direction of the first electrode fingers, the second resonator includes a second electrode having a second IDT electrode including a plurality of second electrode fingers, and second reflectors located on both sides of the second IDT electrode in an arrangement direction of the second electrode fingers, and the third resonator includes a plurality of a third electrode having a third IDT electrode including third electrode fingers, and third reflectors located on both sides of the third IDT electrode in the arrangement direction of the third electrode fingers, wherein the second resonator is located between the first resonator and the third resonator, the first reflector, the second reflector and the third reflector are a single pattern, and the anti-resonant frequency obtained from the pitch and duty of the second electrode fingers is higher than the anti-resonant frequency obtained from the pitch and duty of the first electrode fingers and the anti-resonant frequency obtained from the pitch and duty of the third electrode fingers.

[0006] (2) An acoustic wave resonator according to an embodiment of the present disclosure is the acoustic wave resonator described above in (1), wherein the pitch of the second electrode fingers is smaller than the pitch of the first electrode fingers and the pitch of the third electrode fingers.

[0007] (3) An acoustic wave resonator according to an embodiment of the present disclosure is the acoustic wave resonator described in (1) or (2) above, wherein the duty of the second electrode finger is smaller than the duty of the first electrode finger and the duty of the third electrode finger.

[0008] (4) An elastic wave resonator according to an embodiment of the present disclosure is an elastic wave resonator according to any one of the above (1) to (3). In a polarized wave resonator, if the total area where the first electrode fingers face each other is S1, the total area where the second electrode fingers face each other is S2, and the total area where the third electrode fingers face each other is S3, then 0.95×S2≦S1≦1.05×S2, 0.95×S3≦S2≦1.05×S3, and 0.95×S1≦S3≦1.05×S1 are satisfied.

[0009] (5) An elastic wave resonator according to one embodiment of the present disclosure is an elastic wave resonator according to any one of (1) to (4) above, further comprising a fourth resonator connected in series to the second resonator and the third resonator, the fourth resonator having a fourth electrode having a fourth IDT electrode including a plurality of fourth electrode fingers, and fourth reflectors located on both sides of the fourth IDT electrode in the arrangement direction of the fourth electrode fingers, the fourth resonator being located between the second resonator and the third resonator, the first reflector, the second reflector, the third reflector and the fourth reflector being a single pattern, and the pitch of the fourth electrode fingers being smaller than the pitch of the first electrode fingers and the pitch of the third electrode fingers.

[0010] (6) An acoustic wave resonator according to an embodiment of the present disclosure is a split acoustic wave resonator including a first resonator, a second resonator, and a third resonator connected in series, in which the first resonator includes a first electrode having a first IDT electrode including a plurality of first electrode fingers, and first reflectors located on both sides of the first IDT electrode in an arrangement direction of the first electrode fingers, the second resonator includes a second electrode having a second IDT electrode including a plurality of second electrode fingers, and second reflectors located on both sides of the second IDT electrode in the arrangement direction of the second electrode fingers, and the third resonator includes a third electrode having a third IDT electrode including a plurality of third electrode fingers, and second reflectors located on both sides of the third IDT electrode in the arrangement direction of the third electrode fingers. the second resonator is located between the first resonator and the third resonator; the first reflector, the second reflector, and the third reflector are a single pattern; the length of the second electrode facing the second reflector is smaller than the length of the first electrode facing the first reflector and the length of the third electrode facing the third reflector; and, assuming that the total area of ​​the first electrode fingers facing each other is S1, the total area of ​​the second electrode fingers facing each other is S2, and the total area of ​​the third electrode fingers facing each other is S3, the following relationships hold: 0.95×S2≦S1≦1.05×S2, 0.95×S3≦S2≦1.05×S3, and 0.95×S1≦S3≦1.05×S1.

[0011] (7) An elastic wave resonator according to one embodiment of the present disclosure is an elastic wave resonator as described in (6) above, wherein the length over which the second electrode fingers cross is smaller than the length over which the first electrode fingers cross and the length over which the third electrode fingers cross, and the number of the second electrode fingers is greater than the number of the first electrode fingers and the number of the third electrode fingers.

[0012] (8) An elastic wave resonator according to one embodiment of the present disclosure is the elastic wave resonator described in (6) or (7) above, wherein the first electrode further has a first additional capacitance portion facing the first reflector, and the third electrode further has a third additional capacitance portion facing the third reflector.

[0013] (9) An elastic wave resonator according to an embodiment of the present disclosure is the elastic wave resonator described in any one of (6) to (8), wherein the first IDT electrode is located on both sides in a direction intersecting with the arrangement direction of the first electrode fingers and further includes first bus bars connected to the first electrode fingers, the second IDT electrode is located on both sides in a direction intersecting with the arrangement direction of the second electrode fingers and further includes second bus bars connected to the second electrode fingers, and the third IDT electrode is located on both sides in a direction intersecting with the arrangement direction of the third electrode fingers and further includes third bus bars connected to the third electrode fingers. a length of the second bus bar facing the second reflector is shorter than a length of the first bus bar facing the first reflector and a length of the third bus bar facing the third reflector.

[0014] (10) An acoustic wave resonator according to an embodiment of the present disclosure is a split acoustic wave resonator including a first resonator, a second resonator, and a third resonator connected in series, in which the first resonator includes a first electrode having a first IDT electrode including a plurality of first electrode fingers and first reflectors located on both sides of the first IDT electrode in an arrangement direction of the first electrode fingers, the second resonator includes a second electrode having a second IDT electrode including a plurality of second electrode fingers and second reflectors located on both sides of the second IDT electrode in an arrangement direction of the second electrode fingers, and the third resonator includes a third IDT electrode including a plurality of third electrode fingers. the second resonator is located between the first resonator and the third resonator; the first reflector, the second reflector, and the third reflector have mutually separated patterns; when a pitch of the first electrode fingers is defined as P1, the distance between the first reflector and the second reflector is 4×P1 or more and is greater than the distance between the first reflector and the first IDT electrode; and the distance between the second reflector and the third reflector is 4×P1 or more and is greater than the distance between the third reflector and the third IDT electrode.

[0015] (11) An elastic wave resonator according to one embodiment of the present disclosure is an elastic wave resonator as described in any one of (1) to (10) above, wherein, in the first IDT electrode, electrode fingers located at both ends in the arrangement direction of the first electrode fingers extend from different bus bars, and in the third IDT electrode, electrode fingers located at both ends in the arrangement direction of the third electrode fingers extend from different bus bars.

[0016] (12) An elastic wave resonator according to one embodiment of the present disclosure is an elastic wave resonator as described in any one of (1) to (11) above, wherein, when the pitch of the first electrode fingers is defined as P1, the pitch of the second electrode fingers is defined as P2, and the pitch of the third electrode fingers is defined as P3, 0.99×P2≦P1≦1.01×P2, 0.99×P3≦P2≦1.01×P3, and 0.99×P1≦P3≦1.01×P1 are satisfied.

[0017] (13) An elastic wave resonator according to one embodiment of the present disclosure is an elastic wave resonator as described in any one of (1) to (12) above, wherein the first reflector, the second reflector, and the third reflector are at floating potential and not connected to GND potential.

[0018] (14) A filter device according to one embodiment of the present disclosure comprises an input terminal and an output terminal, a ground terminal connected to a ground potential, a series resonator connected to a series arm connecting the input terminal and the output terminal, and a parallel resonator connected to a parallel arm connecting the series arm and the ground terminal, wherein the series resonator has an acoustic wave resonator according to any one of (1) to (14) above.

[0019] (15) A filter device according to an embodiment of the present disclosure includes a 90° hybrid coupler having a first port and a second port, and a third port and a fourth port to which a signal input to the first port or the second port is distributed, and a filter having a first passband connected to the second port. The filter comprises a first filter, a second filter connected to the third port and having a second passband different from the first passband, and a third filter connected to the fourth port and having the second passband, wherein the first filter has an acoustic wave resonator according to any one of (1) to (14) above.

[0020] (16) A communication device according to one embodiment of the present disclosure includes an antenna, a filter device connected to the antenna, and an IC connected to the filter device, wherein the filter device has an acoustic wave resonator according to any one of (1) to (14) above. [Effects of the Invention]

[0021] According to the above configuration, it is possible to provide an acoustic wave resonator, a filter device, and a communication device with improved power durability and distortion characteristics. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic plan view of an acoustic wave resonator according to an embodiment of the present disclosure. [Figure 2A] FIG. 2 is a schematic cross-sectional view of a first resonator according to an embodiment of the present disclosure. [Figure 2B] FIG. 3 is a schematic cross-sectional view of a second resonator according to an embodiment of the present disclosure. [Figure 2C] FIG. 4 is a schematic cross-sectional view of a third resonator according to an embodiment of the present disclosure. [Figure 3A] FIG. 1 is a schematic circuit diagram of an acoustic wave resonator according to an embodiment of the present disclosure. [Figure 3B] FIG. 1 is a schematic circuit diagram of an acoustic wave resonator according to an embodiment of the present disclosure. [Figure 4] 10 shows simulation results of electromagnetic field calculation in an acoustic wave resonator according to an embodiment of the present disclosure. [Figure 5] FIG. 1 is a schematic plan view of an acoustic wave resonator according to an embodiment of the present disclosure. [Figure 6A] FIG. 2 is a schematic cross-sectional view of a first resonator according to an embodiment of the present disclosure. [Figure 6B] FIG. 3 is a schematic cross-sectional view of a second resonator according to an embodiment of the present disclosure. [Figure 6C] FIG. 4 is a schematic cross-sectional view of a third resonator according to an embodiment of the present disclosure. [Figure 7] FIG. 1 is a schematic plan view of an acoustic wave resonator according to an embodiment of the present disclosure. [Figure 8] FIG. 1 is a schematic plan view of an acoustic wave resonator according to an embodiment of the present disclosure. [Figure 9] FIG. 1 is a schematic plan view of an acoustic wave resonator according to an embodiment of the present disclosure. [Figure 10] FIG. 1 is a schematic plan view of an acoustic wave resonator according to an embodiment of the present disclosure. [Figure 11A] 3 shows the pitch of electrode fingers in each resonator according to an embodiment of the present disclosure. [Figure 11B] 10 shows a simulation of the voltage across each resonator versus the change in frequency for each resonator according to one embodiment of the present disclosure. [Figure 12A] 10 shows the pitch of the electrode fingers in each resonator of the comparative example. [Figure 12B] 10 shows a simulation of the voltage applied to each resonator in the comparative example with respect to a change in frequency. [Figure 13] FIG. 1 is a schematic plan view of an acoustic wave resonator according to an embodiment of the present disclosure. [Figure 14A] FIG. 1 is a schematic circuit diagram of an acoustic wave resonator according to an embodiment of the present disclosure. [Figure 14B] FIG. 1 is a schematic circuit diagram of an acoustic wave resonator according to an embodiment of the present disclosure. [Figure 15] 1 is a schematic diagram of a filter device according to one embodiment of the present disclosure. [Figure 16] 1 is a schematic diagram of a filter device according to one embodiment of the present disclosure. [Figure 17] FIG. 10 is a comparison diagram of simulation results of PIM characteristics between a filter device according to an embodiment of the present disclosure and a comparative example. [Figure 18] 1 is a block diagram illustrating a main part of a communication device according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0023] An acoustic wave resonator, a filter device, and a communication device according to an embodiment of the present disclosure will be described below with reference to the drawings. Note that the drawings used in the following description are schematic diagrams, and the dimensional ratios and the like in the drawings may differ from those of the actual acoustic wave resonator, filter device, and communication device. It doesn't match either.

[0024] For convenience, the drawings may be illustrated with a Cartesian coordinate system consisting of an X-axis, a Y-axis, and a Z-axis. In an embodiment of the present disclosure, any direction of the acoustic wave resonator 10 may be considered to be upward or downward. However, for convenience, the terms upper surface and lower surface may be used, with the Z-axis direction being the up-down direction. The X-axis is defined to be parallel to the propagation direction of an acoustic wave used as the primary resonance among the acoustic waves propagating through the piezoelectric layer 7, the Y-axis is defined to be parallel to the upper surface of the piezoelectric layer 7 and orthogonal to the X-axis, and the Z-axis is defined to be orthogonal to the upper surface of the piezoelectric layer 7.

[0025] It should be noted that the embodiments described in this specification are merely examples, and different embodiments may be partially substituted for each other. Also, different embodiments may be partially combined.

[0026] 1 is a schematic plan view of an acoustic wave resonator 10 according to an embodiment of the present disclosure, as viewed from the Z-axis direction. As shown in FIG. 1, the acoustic wave resonator 10 is a split acoustic wave resonator, and includes three split resonators: a first resonator 1, a second resonator 2, and a third resonator 3. The second resonator 2 is located between the first resonator 1 and the third resonator 3. Here, a split resonator refers to resonators that are connected in series with each other without a parallel resonator connected to ground between them.

[0027] The first resonator 1 has a first electrode 11 and a first reflector 12. The first electrode 11 has a first IDT electrode 111. The first IDT electrode 111 includes, for example, a plurality of first electrode fingers 112. The first IDT electrode 111 also includes a pair of first bus bars 113 that are positioned in a direction intersecting the arrangement direction of the first electrode fingers 112 and are connected to the first electrode fingers 112. The plurality of first electrode fingers 112 are arranged such that the first electrode finger 112a connected to one first bus bar 113a and the first electrode finger 112b connected to the other first bus bar 113b interdigitate with each other.

[0028] The first IDT electrode 111 may also include a plurality of first dummy electrode fingers 114. The first dummy electrode fingers 114 protrude from one of the first bus bars 113 between the respective first electrode fingers 112, and face the first electrode fingers 112 extending from the other first bus bar 113. In the present disclosure, "facing" does not necessarily mean that the opposing surfaces are parallel to each other; for example, one surface may face the other surface at an angle.

[0029] The first reflectors 12 are located on both sides of the first IDT electrode 111 in the arrangement direction of the first electrode fingers 112. The first reflectors 12 include a pair of first reflector bus bars 123 facing each other and a plurality of first reflector strip electrodes 122 extending between the pair of first reflector bus bars 123.

[0030] The second resonator 2 has a second electrode 21 and a second reflector 22. The second electrode 21 has a second IDT electrode 211. The second IDT electrode 211 includes, for example, a plurality of second electrode fingers 212. The second IDT electrode 211 also includes a pair of second bus bars 213 that are positioned in a direction intersecting the arrangement direction of the second electrode fingers 212 and are connected to the second electrode fingers 212. The plurality of second electrode fingers 212 are arranged such that the second electrode finger 212a connected to one second bus bar 213a and the second electrode finger 212b connected to the other second bus bar 213b interdigitate with each other.

[0031] The second IDT electrode 211 may also include a plurality of second dummy electrode fingers 214. The second dummy electrode fingers 214 protrude from one of the second bus bars 213 between the plurality of second electrode fingers 212, and face the first electrode fingers 212 extending from the other second bus bar 213.

[0032] The second reflectors 22 are located on both sides of the second IDT electrode 211 in the arrangement direction of the second electrode fingers 212. The second reflectors 22 include a pair of second reflector bus bars 223 facing each other and a plurality of second reflector strip electrodes 222 extending between the pair of second reflector bus bars 223.

[0033] The third resonator 3 has a third electrode 31 and a third reflector 32. The third electrode 31 has a third IDT electrode 311. The third IDT electrode 311 includes, for example, a plurality of third electrode fingers 312. The third IDT electrode 311 also includes a pair of third bus bars 313 that are positioned in a direction intersecting the arrangement direction of the third electrode fingers 312 and are connected to the third electrode fingers 312. The plurality of third electrode fingers 312 are arranged such that the third electrode finger 312a connected to one third bus bar 313a and the third electrode finger 312b connected to the other third bus bar 313b interdigitate with each other.

[0034] The third IDT electrode 311 may also include a plurality of third dummy electrode fingers 314. The third dummy electrode fingers 314 protrude from one of the third bus bars 313 between the respective third electrode fingers 312, and face the third electrode fingers 312 extending from the other third bus bar 313.

[0035] The third reflectors 32 are located on both sides of the third IDT electrode 311 in the arrangement direction of the third electrode fingers 312. The third reflectors 32 include a pair of third reflector bus bars 323 facing each other and a plurality of third reflector strip electrodes 322 extending between the pair of third reflector bus bars 323.

[0036] The numbers of first electrode fingers 112, second electrode fingers 212, and third electrode fingers 312 may be set appropriately, for example, to be the same. In the first IDT electrode 111, the electrode fingers located at both ends of the first electrode fingers 112 in the arrangement direction may extend from different first bus bars 113. In other words, one of the electrode fingers located at both ends of the first electrode fingers 112 in the arrangement direction extends from first bus bar 113a, and the other extends from first bus bar 113b. In the third IDT electrode 311, the electrode fingers located at both ends of the third electrode fingers 312 in the arrangement direction may extend from different third bus bars 313. In other words, one of the electrode fingers located at both ends of the third electrode fingers 312 in the arrangement direction extends from third bus bar 313a, and the other extends from third bus bar 313b.

[0037] The first electrode 11, the second electrode 21, and the third electrode 31 contain various conductive materials. Examples of such materials include aluminum (Al), copper (Cu), platinum (Pt), molybdenum (Mo), gold (Au), and alloys thereof. The first electrode 11, the second electrode 21, and the third electrode 31 may be formed by stacking multiple layers containing the various conductive materials described above. When the first electrode 11, the second electrode 21, and the third electrode 31 are formed by stacking multiple layers, an underlayer may be interposed at the stacking interface. In one embodiment of the present disclosure, the first electrode 11, the second electrode 21, and the third electrode 31 specifically contain Al.

[0038] In the acoustic wave resonator 10 according to the embodiment of the present disclosure, the first electrode 11, the second electrode 21, and the third electrode 31 may be referred to as electrodes 101 for convenience.

[0039] The first reflector 12, the second reflector 22, and the third reflector 32 may include various conductive materials, and may include, for example, the same materials as the materials of the first electrode 11, the second electrode 21, and the third electrode 31. The first reflector 12, the second reflector 22, and the third reflector 32 may also be configured by stacking multiple layers made of the various conductive materials described above. In one embodiment of the present disclosure, Specifically, the first reflector 12, the second reflector 22 and the third reflector 32 contain Al.

[0040] In the acoustic wave resonator 10 according to an embodiment of the present disclosure, the first reflector 12, the second reflector 22, and the third reflector 32 are integrally formed using a single pattern. For convenience, the first reflector 12, the second reflector 22, and the third reflector 32 integrally formed using a single pattern may be referred to as a shared reflector 102. The shared reflectors 102 are located on both sides of the second IDT electrode 211 in the arrangement direction of the second electrode fingers 212, for example.

[0041] In one embodiment of the present disclosure, the shared reflector 102 is not connected to the GND potential and is at a floating potential, but is not limited to this example. For example, the shared reflector 102 may be connected to the GND or to another part of the circuit.

[0042] 2A is a schematic cross-sectional view of the elastic wave resonator 10 according to the embodiment shown in FIG. 1 , taken along line IIA-IIA. In other words, FIG. 2A is a schematic cross-sectional view of the first resonator 1. FIG. 2B is a schematic cross-sectional view of the elastic wave resonator 10 according to the embodiment shown in FIG. 1 , taken along line IIB-IIB. In other words, FIG. 2B is a schematic cross-sectional view of the second resonator 2. FIG. 2C is a schematic cross-sectional view of the elastic wave resonator 10 according to the embodiment shown in FIG. 1 , taken along line IIC-IIC. In other words, FIG. 2C is a schematic cross-sectional view of the third resonator 3. As shown in FIGS. 2A to 2C , the elastic wave resonator 10 according to the embodiment of the present disclosure includes a piezoelectric layer 7.

[0043] The piezoelectric layer 7 has an upper surface 7a and a lower surface 7b that are perpendicular to the Z axis, with the Z axis being the up-down direction. An electrode 101 and a shared reflector 102 are located on the upper surface 7a of the piezoelectric layer 7.

[0044] The piezoelectric layer 7 may include various materials having piezoelectricity. Examples of materials having piezoelectricity include a single crystal of lithium tantalate (LiTaO3; hereinafter referred to as LT) and a single crystal of lithium niobate (LiNbO3; hereinafter referred to as LN). In one embodiment of the present disclosure, the piezoelectric layer 7 is specifically a single crystal of LT.

[0045] The piezoelectric layer 7 has piezoelectric properties, and when a high-frequency signal is applied to the electrode 101, an elastic wave is excited that propagates through the piezoelectric layer 7. Of the excited elastic waves, which type of elastic wave is used as the main resonance may be set according to the desired frequency characteristics, etc.

[0046] The thickness of the piezoelectric layer 7 may be appropriately designed depending on the desired frequency characteristics or the type of elastic wave used as the main resonance. For example, the thickness of the piezoelectric layer 7 may be 2λ or less when expressed using a wavelength λ. In this case, Lamb waves can be effectively used as the main resonance.

[0047] Furthermore, the thickness of the piezoelectric layer 7 in the region overlapping with the electrode 101 may be constant in plan view. Such a configuration can provide an elastic wave resonator 10 with good frequency characteristics. Note that the thickness of the piezoelectric layer 7 being constant does not necessarily mean that the thickness is strictly constant, and some variation is allowed as long as it does not significantly affect the characteristics of the elastic waves propagating through the piezoelectric layer 7.

[0048] In the acoustic wave resonator 10 according to an embodiment of the present disclosure, the propagation mode of the acoustic wave used as the primary resonance is not particularly limited and may be set according to the desired frequency characteristics. The Euler angles (φ, θ, ψ) of the piezoelectric single crystal used as the piezoelectric layer 7 may be appropriately designed according to the type and propagation mode of the acoustic wave used as the primary resonance.

[0049] The acoustic wave resonator 10 according to the embodiment of the present disclosure has a support substrate 8 on the lower surface 7b of the piezoelectric layer 7. The thickness of the support substrate 8 is not particularly limited, and the support substrate 8 may be thicker than the piezoelectric layer 7, for example.

[0050] Furthermore, the material of the support substrate 8 is not particularly limited. For example, the material of the support substrate 8 may be a material with a linear expansion coefficient smaller than that of the piezoelectric layer 7. By using such a material for the support substrate 8, deformation of the piezoelectric layer 7 due to temperature changes is reduced. As a result, changes in the resonance characteristics of the acoustic wave resonator 10 due to temperature changes are reduced. Examples of such materials for the support substrate 8 include sapphire (Al2O3), silicon carbide (SiC), and silicon (Si).

[0051] The acoustic wave resonator 10 according to an embodiment of the present disclosure may have an acoustic reflection layer between the piezoelectric layer 7 and the support substrate 8. The acoustic reflection layer includes at least a low acoustic impedance layer. The acoustic impedance of the low acoustic impedance layer is lower than the acoustic impedance of the piezoelectric layer 7. By providing the low acoustic impedance layer on the lower surface 7b side of the piezoelectric layer 7 in this manner, acoustic waves propagating through the piezoelectric layer 7 are reflected by the low acoustic impedance layer and confined within the piezoelectric layer 7, thereby reducing leakage of the acoustic waves from the lower surface 7b side. An example of such a low acoustic impedance layer is silicon oxide (SiO2).

[0052] The acoustic reflection layer may also be configured by alternately stacking multiple low acoustic impedance layers and multiple high acoustic impedance layers, each having an acoustic impedance higher than that of the low acoustic impedance layers. Such a configuration of the acoustic reflection layer allows acoustic waves leaking from the lower surface 7b of the piezoelectric layer 7 to be reflected back toward the piezoelectric layer 7 at the interface between the low acoustic impedance layer and the high acoustic impedance layer, thereby more effectively reducing the leakage of acoustic waves. Examples of such high acoustic impedance layers include hafnium oxide (HfO2), tantalum oxide (Ta2O5), and zirconium oxide (ZrO2).

[0053] The low acoustic impedance layer of the acoustic reflection layer may be a solid layer, but is not limited to this example. For example, the low acoustic impedance layer may be a gas present in a void provided in the support substrate 8. The void is present on the piezoelectric layer 7 side of the support substrate 8, at a position overlapping the electrode 101 in a plan view. The void is covered by the piezoelectric layer 7, leaving an internal space, in which a gas is present. The gas may be ordinary air or an inert gas such as nitrogen or argon. In this case, the gas present in the void acts as an acoustic reflection layer, effectively reducing the leakage of acoustic waves from the lower surface 7b of the piezoelectric layer 7. The size and depth of the void may be set as appropriate.

[0054] As shown in FIG. 2A , the pitch of first electrode fingers 112 is P1, and the width of first electrode fingers 112 is W1. The duty of first electrode fingers 112 is D1. The duty of first electrode fingers 112 is the width of first electrode fingers 112 divided by the pitch of first electrode fingers 112. The pitch of first electrode fingers 112 does not need to be precisely constant; some variation is allowed within a range that does not significantly affect the characteristics of the resonator. If the pitch of first electrode fingers 112 is not constant, P1 may be defined as the average value of the pitch, or as the representative largest pitch. The width of first electrode fingers 112 does not need to be precisely constant; some variation is allowed within a range that does not significantly affect the characteristics of the resonator. If the width of first electrode fingers 112 is not constant, W1 may be defined as the average value of the width, or as the representative largest width.

[0055] 2B , the pitch of second electrode fingers 212 is P2, and the width of second electrode fingers 212 is W2. Furthermore, the duty of second electrode fingers 212 is D2. The duty of second electrode fingers 212 is the value obtained by dividing the width of second electrode fingers 212 by the pitch of second electrode fingers 212. The pitch of the second electrode fingers 212 does not need to be exactly constant, and some variation is allowed as long as it does not significantly affect the characteristics of the resonator. When the pitch of the second electrode fingers 212 is not constant, the average value of the pitch may be defined as P2, or the largest pitch may be defined as P2 as a representative. Also, the width of the second electrode fingers 212 does not need to be exactly constant, and some variation is allowed as long as it does not significantly affect the characteristics of the resonator. When the width of the second electrode fingers 212 is not constant, the average value of the width may be defined as W2, or the largest width may be defined as W2 as a representative.

[0056] As shown in FIG. 2C, let the pitch of the third electrode fingers 312 be P3 and the width of the third electrode fingers 312 be W3. Also, let the duty of the third electrode fingers 312 be D3. The duty of the third electrode fingers 312 is the value obtained by dividing the width of the third electrode fingers 312 by the pitch of the third electrode fingers 312. The pitch of the third electrode fingers 312 does not need to be exactly constant, and some variation is allowed as long as it does not significantly affect the characteristics of the resonator. When the pitch of the third electrode fingers 312 is not constant, the average value of the pitch may be defined as P3, or the largest pitch may be defined as P3 as a representative. Also, the width of the third electrode fingers 312 does not need to be exactly constant, and some variation is allowed as long as it does not significantly affect the characteristics of the resonator. When the width of the third electrode fingers 312 is not constant, the average value of the width may be defined as W3, or the largest width may be defined as W3 as a representative.

[0057] In the surface acoustic wave resonator 10 according to an embodiment of the present disclosure, the anti-resonance frequency fr2 obtained from the pitch and duty of the second electrode fingers 212 is designed to be higher than the anti-resonance frequency fr1 obtained from the pitch and duty of the first electrode fingers 112 and the anti-resonance frequency fr3 obtained from the pitch and duty of the third electrode fingers 312. For example, in the embodiments described in FIGS. 2A to 2C, the pitch of the second electrode fingers 212 is designed to be smaller than the pitch of the first electrode fingers 112 and the pitch of the third electrode fingers 312. In other words, it is designed such that P2 < P1 and P2 < P3 hold.

[0058] In addition, in one embodiment of the present disclosure, if the relationship of P2 < P1 and P2 < P3 holds, the magnitudes of P1, P2, and P3 are not particularly limited. For example, P1, P2, and P3 may be within a range including a difference of 10% or less from each other. In other words, 0.99×P2 ≤ P1 ≤ 1.01×P2 and 0.99×P3 ≤ P2 ≤ 1.01×P3 and 0.99×P1 ≤ P3 ≤ 1.01×P1 may also hold. In this case, variations in the characteristics of each resonator can be reduced.

[0059] FIGS. 3A and 3B are schematic circuit diagrams of the elastic wave resonator 10 which is one embodiment of the present disclosure. FIG. 3A is a circuit diagram showing the parasitic capacitance C generated between the electrode 101 and the shared reflector 102. FIG. 3B is a circuit diagram obtained by omitting and simplifying the portions at the same potential in the circuit diagram of FIG. 3A. As shown in FIG. 3B, more parasitic capacitance is applied to the second resonator 2 than to the first resonator 1 and the third resonator 3.

[0060] FIG. 4 shows the simulation results of electromagnetic field calculations in the elastic wave resonator 10 which is one embodiment of the present disclosure. The shading of the color represents the level of the electric potential, and the closer the color is to white, the higher the electric potential, and the closer the color is to black, the lower the electric potential. As can be seen from FIG. 4, the electric potential of the second reflector 22 is lower than the electric potentials of the first reflector 12 and the third reflector 32. Therefore, the capacitance between the second reflector 22 and the second electrode 21 is larger than the capacitance between the first reflector 12 and the first electrode 11 and the capacitance between the third reflector 32 and the third electrode 31.

[0061] When more parasitic capacitance is applied to the second resonator 2 than to the first resonator 1 and the third resonator 3, the anti-resonance frequency of the second resonator 2 becomes smaller than the anti-resonance frequencies of the first resonator 1 and the third resonator 3. As a result, variations occur in the impedance at the anti-resonance frequency in each of the first resonator 1, the second resonator, and the third resonator that constitute the elastic wave resonator ①, and variations occur in the voltage applied to each resonator.

[0062] In the elastic wave resonator 10 according to an embodiment of the present disclosure, the pitch of the second electrode fingers 212 is designed to be smaller than the pitch of the first electrode fingers 112 and the pitch of the third electrode fingers 312. Therefore, the anti-resonance frequency fr2 obtained from the pitch of the second electrode fingers 212 is higher than the anti-resonance frequency fr1 obtained from the pitch of the first electrode fingers 112 and the anti-resonance frequency fr3 obtained from the pitch of the third electrode fingers 312. As a result, the variation in the anti-resonance frequencies of the first resonator 1, the second resonator 2, and the third resonator 3 due to parasitic capacitance is reduced, and the variation in the voltage applied to each resonator is reduced. Thus, according to an embodiment of the present disclosure, an elastic wave resonator with improved power resistance and strain characteristics can be provided.

[0063] In the embodiment described in FIGS. 2A to 2C, the pitch of the second electrode fingers 212 is configured to be smaller than the pitch of the first electrode fingers 112 and the pitch of the third electrode fingers 312. However, the present disclosure is not limited to this example. For example, as another embodiment of the present disclosure, the duty of the second electrode fingers 212 may be designed to be smaller than the duty of the first electrode fingers 112 and the duty of the third electrode fingers 312. In other words, it may be designed such that D2 < D1 and D2 < D3 are satisfied. A schematic plan view of the elastic wave resonator 10 according to another embodiment of the present disclosure as viewed from the Z-axis direction is shown in FIG. 5.

[0064] FIG. 6A is a schematic cross-sectional view taken along the cut line VIA-VIA of the elastic wave resonator 10 according to the embodiment described in FIG. 5. FIG. 6B is a schematic cross-sectional view taken along the cut line VIB-VIB of the elastic wave resonator 10 according to the embodiment described in FIG. 5. FIG. 6C is a schematic cross-sectional view taken along the cut line VIC-VIC of the elastic wave resonator 10 according to the embodiment described in FIG. 5.

[0065] 6A to 6C , in an acoustic wave resonator 10 according to another embodiment of the present disclosure, the duty of the second electrode finger 212 is designed to be smaller than the duty of the first electrode finger 112 and the duty of the third electrode finger 312. As a result, in an acoustic wave resonator 10 according to another embodiment of the present disclosure, the antiresonant frequency fr2 determined from the duty of the second electrode finger 212 is designed to be higher than the antiresonant frequency fr1 determined from the duty of the first electrode finger 112 and the antiresonant frequency fr3 determined from the duty of the third electrode finger 312. Therefore, variations in the antiresonant frequencies of the first resonator 1, the second resonator 2, and the third resonator 3 due to parasitic capacitance are reduced, and variations in the voltages applied to the resonators are also reduced.

[0066] Furthermore, in one embodiment of the present disclosure, the capacitance of the first IDT electrode 111, the capacitance of the second IDT electrode 211, and the capacitance of the third IDT electrode 311 may be set as appropriate and may be, for example, approximately the same. The capacitances of the first IDT electrode 111, the second IDT electrode 211, and the third IDT electrode 311 being approximately the same means that the first IDT electrode 111, the second IDT electrode 211, and the third IDT electrode 311 are formed to have the same capacitance.

[0067] The capacitance of the first IDT electrode 111 may be determined, for example, by the total area over which the first electrode fingers 112 face each other, the capacitance of the second IDT electrode 211 may be determined, for example, by the total area over which the second electrode fingers 212 face each other, and the capacitance of the third IDT electrode 311 may be determined, for example, by the total area over which the third electrode fingers 312 face each other. Therefore, as an example of the "form having the same capacitance," it is sufficient that the total area over which the first electrode fingers 112 face each other, the total area over which the second electrode fingers 212 face each other, and the total area over which the third electrode fingers 312 face each other are approximately the same. Note that "the total opposing areas are approximately the same" does not necessarily mean that they are exactly the same. For example, the total area S1 over which the first electrode fingers 112 face each other, the total area S2 over which the second electrode fingers 212 face each other, and the total area S3 over which the third electrode fingers 312 face each other may each include a manufacturing error of 5% or less. exchange In other words, 0.95×S2≦S1≦1.05×S2, 0.95×S3≦S2≦1.05×S3, and 0.95×S1≦S3≦1.05×S1. In this way, when the capacitances of the first IDT electrode 111, the second IDT electrode 211, and the third IDT electrode 311 are approximately the same, the variation in voltage applied to each resonator is more effectively reduced.

[0068] As an example of the "form having the same capacitance," the distances between first electrode fingers 112, second electrode fingers 212, and third electrode fingers 312 may be approximately the same. Note that "approximately the same distances" does not necessarily mean that the distances are exactly the same; for example, the distances between first electrode fingers 112, second electrode fingers 212, and third electrode fingers 312 may have a difference of 1% or less. In this way, when the capacitances of first IDT electrode 111, second IDT electrode 211, and third IDT electrode 311 are approximately the same, the variation in voltage applied to each resonator is more effectively reduced.

[0069] In the embodiment described above, by designing the antiresonant frequency fr2 to be higher than the antiresonant frequency fr1 and the antiresonant frequency fr3, it is possible to reduce the variation in the antiresonant frequencies of the resonators, which occurs when the second resonator 2 has more parasitic capacitance than the other resonators. However, the method for reducing the variation in the antiresonant frequencies of the resonators is not limited to this example. For example, in another embodiment of the present disclosure, the opposing length between the second electrode 21 and the second reflector 22 may be shorter than the opposing length between the first electrode 11 and the first reflector 12 and the opposing length between the third electrode 31 and the third reflector 32. In this case, the opposing area between the second reflector 22 and the second electrode 21, which generates more parasitic capacitance, can be relatively reduced, thereby reducing the influence of the variation in the parasitic capacitance generated in each resonator.

[0070] FIG. 7 shows a schematic plan view of a part of an embodiment of the present disclosure. In one embodiment described in FIG. 7, the length L2 at which the second electrode fingers 212 cross each other may be smaller than the length L1 at which the first electrode fingers 112 cross each other and the length L3 at which the third electrode fingers 312 cross each other. In other words, L2 < L1 and L2 < L3 may be satisfied. In this case, the length of the second reflector 22 facing the second electrode 21 becomes smaller than the length of the first reflector 12 facing the first electrode 11 and the length of the third reflector 32 facing the third electrode 31. Therefore, the area of the opposing surface of the second reflector 12 and the second electrode 22 where more parasitic capacitance occurs can be relatively reduced, and the influence of variations in parasitic capacitance generated in each resonator can be reduced.

[0071] Note that, in one embodiment described in FIG. 7, the case where the length L1 at which the first electrode fingers 112 cross each other is constant is shown, but it is not limited to this example. For example, when the length at which the first electrode fingers 112 cross each other is not constant, the largest length among a plurality of lengths may be defined as L1. This definition method can also be applied to L2 and L3 in the same way.

[0072] Also, when L2 < L1 and L2 < L3, the number of the second electrode fingers 212 may be larger than the number of the first electrode fingers 112 and the number of the third electrode fingers 312. When L2 < L1 and L2 < L3, the total area where the second electrode fingers 212 face each other becomes smaller than the total area where the first electrode fingers 112 face each other and the total area where the third electrode fingers 312 face each other. As a result, the capacitance of the second IDT electrode 211 becomes smaller than the capacitance of the first IDT electrode 111 and the capacitance of the third IDT electrode 311, so variations occur in the capacitance of each resonator. When the number of the second electrode fingers 212 is larger than the number of the first electrode fingers 112 and the number of the third electrode fingers 312, the total area where the second electrode fingers 212 face each other increases, so variations in the capacitance of each resonator can be reduced.

[0073] Fig. 8 shows a schematic plan view of a portion of an embodiment of the present disclosure. In the embodiment shown in Fig. 8, the first electrode 11 may have a first additional capacitance 115 facing the first reflector 12. In addition, the third electrode 31 has a third additional capacitance 315 facing the third reflector 32. In this case, the opposing length between the first electrode 11 and the first reflector 12 increases by the amount of the first additional capacitance 115, and the opposing length between the third electrode 31 and the third reflector 32 increases by the amount of the third additional capacitance 315. As a result, the opposing length between the first reflector 12 and the first electrode 11 and the opposing length between the third reflector 32 and the third electrode 31 become shorter than the opposing length between the second reflector 22 and the second electrode 21. Therefore, the opposing area between the second reflector 22 and the second electrode 21, where more parasitic capacitance is generated, can be made relatively small, and the influence of variations in the parasitic capacitance generated in each resonator can be reduced.

[0074] FIG. 9 is a schematic plan view of a portion of an embodiment of the present disclosure. In the embodiment illustrated in FIG. 9 , the opposing length between the second busbar 213 and the second reflector 22 may be shorter than the opposing length between the first busbar 113 and the first reflector 12 and the opposing length between the third busbar 313 and the third reflector 32. For example, by including the cutout 9 in the second busbar 213, the opposing length between the second busbar 213 and the second reflector 22 becomes shorter than the opposing length between the first busbar 113 and the first reflector 12 and the opposing length between the third busbar 313 and the third reflector 32. Therefore, the opposing area between the second reflector 12 and the second electrode 22, which generates more parasitic capacitance, can be relatively reduced, thereby reducing the effects of variations in the parasitic capacitance generated in each resonator. Note that the size and shape of the cutout 9 may be changed as appropriate.

[0075] In the above-described embodiment, the acoustic wave resonator 10 is configured to include only the first resonator 1, the second resonator 2, and the third resonator 3. However, the present invention is not limited to this example. For example, the acoustic wave resonator 10 may include four or more resonators in total.

[0076] FIG. 10 shows a surface acoustic wave resonator 10 according to an embodiment of the present disclosure. In one embodiment described in FIG. 10, the surface acoustic wave resonator 10 has a total of six resonators. For example, from the direction in which a signal is input, they are defined as the first resonator 1, the second resonator 2, the fourth resonator 4, the fifth resonator 5, the sixth resonator 6, and the third resonator 3.

[0077] The fourth resonator 4 has a fourth electrode 41 and a fourth reflector 42. The fifth resonator 5 has a fifth electrode 51 and a fifth reflector 52. The sixth resonator 6 has a sixth electrode 61 and a sixth reflector 62. The first reflectors 12 to the sixth reflectors 62 are integrally formed by a single pattern.

[0078] The fourth electrode 41, the fifth electrode 51, and the sixth electrode 61 each have a fourth IDT electrode 411 including a plurality of fourth electrode fingers 412, a fifth IDT electrode 511 including a plurality of fifth electrode fingers 512, and a sixth IDT electrode 611 including a plurality of sixth electrode fingers 612.

[0079] Let the pitch of the fourth electrode fingers 412 be P4, the width be W4, and the duty be D4. Let the pitch of the fifth electrode fingers 512 be P5, the width be W5, and the duty be D5. Let the pitch of the sixth electrode fingers 612 be P6, the width be W6, and the duty be D6. The method of defining the pitch, width, and duty may be the same as the method for the first electrode fingers 112, the second electrode fingers 212, and the third electrode fingers 312 described above.

[0080] FIG. 11A shows the pitch of the electrode fingers in each resonator according to one embodiment described in FIG. 10. In one embodiment described in FIG. 10, the pitch of the electrode fingers is smaller for the resonators located more centrally. In other words, P1 > P2 > P4 and P3 > P6 > P5. Also, P4 < P3 and P5 < P1. FIG. 11B shows a simulation of the voltage applied to each resonator with respect to a change in frequency in each resonator according to one embodiment described in FIG. 10. The horizontal axis in FIG. 11B represents frequency, and the vertical axis represents voltage. FIG. 12A shows the pitch of the electrode fingers in each resonator in Comparative Example 900. In Comparative Example 900, each The pitch of the resonators is the same. Figure 12B shows a simulation of the voltage across each resonator in the comparative example 900 versus the change in frequency.

[0081] As shown in FIG. 4 , the parasitic capacitance between the reflector and electrode of a resonator located at the center is larger than the parasitic capacitance between the reflector and electrode of a resonator located at an edge. In the embodiment described in FIG. 10 , the electrode finger pitch of a resonator located closer to the center is smaller. Therefore, compared to comparative example 900, the antiresonant frequency calculated from the electrode finger pitch of a resonator located at the center is higher than the antiresonant frequency calculated from the electrode finger pitch of a resonator located at an edge. As a result, the variation in antiresonant frequency due to the parasitic capacitance of each resonator is reduced, and the variation in voltage applied to each resonator is reduced as shown in FIG. 11B . As such, according to one embodiment of the present disclosure, an acoustic wave resonator with improved power durability and distortion characteristics can be provided.

[0082] 7 to 9, the influence of variations in the parasitic capacitance generated in each resonator can be reduced by relatively reducing the opposing area between the second reflector 12, which generates more parasitic capacitance, and the second electrode 22. However, the method for reducing the influence of variations in the parasitic capacitance generated in each resonator is not limited to this example.

[0083] For example, in another embodiment of the present disclosure, the first reflector 12, the second reflector 22, and the third reflector 32 may be formed so as to be separated from one another by different patterns, as shown in Fig. 13. Fig. 14A is a schematic circuit diagram of an acoustic wave resonator 10 according to the embodiment shown in Fig. 13. Fig. 14A shows parasitic capacitances C generated between the first electrode 11 and the first reflector 12, between the second electrode 21 and the second reflector 22, and between the third electrode 31 and the third reflector 32, as well as parasitic capacitances C' generated between the first reflector 12 and the second reflector 22 and between the second reflector 22 and the third reflector 32. Fig. 14B is a simplified circuit diagram of the circuit diagram of Fig. 14A , omitting parts at the same potential.

[0084] 13 , if the pitch of the first electrode fingers 112 is P1, the distance between the first reflector 12 and the second reflector 22 may be 4×P1 or more and greater than the distance between the first reflector 12 and the first IDT electrode 112. Furthermore, the distance between the second reflector 22 and the third reflector 32 may be 4×P1 or more and greater than the distance between the third reflector 32 and the third IDT electrode 311. In this case, the parasitic capacitance C′ generated between the reflectors is relatively smaller than the parasitic capacitance C generated between the reflector and the IDT electrode, and the overall parasitic capacitance is reduced. As a result, the influence of the parasitic capacitance is reduced, and the influence of variations in the parasitic capacitance generated in each resonator can be reduced.

[0085] (Example of use of acoustic wave resonator 10: filter device) Fig. 15 is a circuit diagram schematically illustrating a configuration of a filter device 701 according to an embodiment of the present disclosure. The filter device 701 is an example of use of the acoustic wave resonator 10. As can be seen from the symbols shown in the upper left of Fig. 15, in Fig. 15, the electrode 101 is schematically represented by a two-pronged fork shape, and the shared reflector 102 is represented by a single line bent at both ends.

[0086] The filter device 701 includes, for example, a transmit filter 705 that filters a transmit signal from a transmit terminal 703 and outputs the filtered signal to an antenna terminal 702, and a receive filter 706 that filters a receive signal from the antenna terminal 702 and outputs the filtered signal to a receive terminal 704. The transmit filter 705 has a first passband. The receive filters 706a and 706b have second passbands that are different from the first passband.

[0087] The transmission filter 705 and the reception filter 706 are each configured as a ladder filter, in which a plurality of resonators are connected in a ladder configuration. and one or more parallel resonators connecting the series arms of the series resonators to a GND potential. For example, the acoustic wave resonator 10 according to an embodiment of the present disclosure may be used as either a series resonator or a parallel resonator included in at least the transmit filter 705 and the receive filter 706.

[0088] 15, both the transmit filter 705 and the receive filter 706 are acoustic wave filters, but the present invention is not limited to this configuration. For example, one of the transmit filter 705 and the receive filter 706 may be an acoustic wave filter that uses the acoustic wave resonator 10, and the other may be an LC filter that includes one or more inductors and one or more capacitors.

[0089] Furthermore, the filter device 701 may include a plurality of transmit filters 705, and may include a plurality of receive filters 706. Fig. 16 shows a case where the filter device 701 according to an embodiment of the present disclosure includes a plurality of receive filters 706.

[0090] 16, the filter device 701 includes a transmit filter 705 and two receive filters 706a and 706b. The transmit filter 705 has a first passband. The receive filters 706a and 706b have second passbands different from the first passband.

[0091] 16 includes two 90° hybrid couplers 800a and 800b. The 90° hybrid coupler 800a has a first port 801a, a second port 802a, a third port 803a, and a fourth port 804a, and a signal input to the first port 801a or the second port 802a is distributed and output to the third port 803a and the fourth port 804a. The 90° hybrid coupler 800b has a first port 801b, a second port 802b, a third port 803b, and a fourth port 804b.

[0092] The first port 801a of the 90° hybrid coupler 800a is connected to the antenna terminal 702, the second port 802a is connected to the transmit filter 705, the third port 803a is connected to the receive filter 706, and the fourth port 804a is connected to the receive filter 706b. The first port 801b of the 90° hybrid coupler 800b is connected to the receive filter 706b, the second port 802b is connected to the receive filter 706a, the third port 803b is connected to the receive terminal 704, and the fourth port 804b is connected to the termination resistor 707.

[0093] For example, the acoustic wave resonator 10 according to an embodiment of the present disclosure may be used as at least one of the transmit filter 705 and the receive filter 706. Alternatively, the acoustic wave resonator 10 may be used as both the transmit filter 705 and the receive filter 706.

[0094] 16, when signals of two different frequencies flow from the transmitting terminal 703 of the filter device 701 according to one embodiment, the signals combine to generate a new signal called PIM (Passive Inter Modulation). The generated PIM is ultimately input to the termination resistor 707, and if the frequency of the generated PIM is within the second passband of the receiving filter 706, it may affect the frequency characteristics of the filter.

[0095] FIG. 17 compares the simulation results of the PIM characteristics of filter device 701 according to an embodiment of the present disclosure and comparative example 901. The vertical axis of FIG. 17 indicates PIM intensity, with the PIM intensity increasing downward. The horizontal axis of FIG. 17 indicates PIM frequency. Comparative example 901 is a filter device that does not include acoustic wave resonator 10 according to an embodiment of the present disclosure, but instead includes the acoustic wave resonator shown in comparative example 900. As shown in FIG. 17, the PIM intensity of filter device 701 according to an embodiment of the present disclosure is smaller than that of comparative example 901. The distortion characteristics are improved.

[0096] (Example of use of acoustic wave resonator 10: communication device) 18 is a block diagram showing a main part of a communication device 711 as an example of using acoustic wave resonator 10 and filter device 701. Communication device 711 includes filter device 701 and performs wireless communication using radio waves.

[0097] In the communication device 711, a transmission information signal TIS containing information to be transmitted is modulated and frequency-raised by an RF-IC (Radio Frequency Integrated Circuit) 713 to generate a transmission signal TS. Unwanted components outside the transmission passband are removed from the transmission signal TS by a bandpass filter 715a, amplified by an amplifier 714a, and input to the filter device 701. The filter device 701 then removes the unwanted components outside the transmission passband from the input transmission signal TS, and outputs the removed transmission signal TS from an antenna terminal 702 to an antenna 712. The antenna 712 converts the input transmission signal TS into a wireless signal and transmits it.

[0098] Furthermore, in the communication device 711, a radio signal received by an antenna 712 is converted by the antenna 712 into a received signal RS and input to the filter device 701. The filter device 701 removes unnecessary components outside the reception passband from the input received signal RS and outputs the signal from a receiving terminal 704 to an amplifier 714b. The output received signal RS is amplified by the amplifier 714b, and unnecessary components outside the reception passband are removed by a bandpass filter 715b. The received signal RS is then frequency-downshifted and demodulated by the RF-IC 713 to become a received information signal RIS.

[0099] The transmit information signal TIS and the receive information signal RIS may be low-frequency signals containing appropriate information, such as analog audio signals or digitized audio signals. The passband of the radio signal may be set as appropriate, and in one embodiment of the present disclosure, a relatively high-frequency passband is also possible. The modulation method may be phase modulation, amplitude modulation, frequency modulation, or a combination of two or more of these. While FIG. 18 illustrates a direct conversion system as an example of the circuit system, the present invention is not limited to this example and may also be, for example, a double superheterodyne system. Furthermore, FIG. 18 schematically illustrates only the essential parts; low-pass filters or isolators may be added at appropriate positions, and the positions of amplifiers and other components may be changed. [Explanation of symbols]

[0100] 1: 1st resonator 11: 1st electrode 111: First IDT electrode 112: 1st electrode finger 113: First bus bar 114: First dummy electrode finger 115: First additional capacitance section 12: 1st reflector 122: First reflector strip electrode 123: First reflector bus bar 2: Second resonator 21:Second electrode 211: 2nd IDT electrode 212:Second electrode finger 213: Second bus bar 214: Second dummy electrode finger 22:Second reflector 222: Second reflector strip electrode 223: Second reflector bus bar 3: Third resonator 31: Third electrode 311: 3rd IDT electrode 312:Third electrode finger 313: 3rd bus bar 314: Third dummy electrode finger 315: Third additional capacitance section 32: Third reflector 322: Third reflector strip electrode 323: Third reflector busbar 4: 4th resonator 41: 4th electrode 411: Fourth IDT electrode 412: 4th electrode finger 42: 4th reflector 5: 5th resonator 6: 6th resonator 7: Piezoelectric layer 7a:Top surface 7b: Bottom surface 8: Support substrate 9: Notch 10: Elastic wave resonator 101: Electrode 102: Shared reflector 701: Filter device 702: Antenna terminal 703: Transmit terminal 704: Receiving terminal 705: Outbound filter 706: Receive filter 707: Termination resistor 800a, 800b: 90° hybrid coupler 711:Communication equipment 712: Antenna 713: RF-IC 714: Amplifier 715: Bandpass filter

Claims

1. An elastic wave resonator that is a split elastic wave resonator including a first resonator, a second resonator, and a third resonator connected in series, The first resonator is a first electrode having a first IDT electrode including a plurality of first electrode fingers; first reflectors located on both sides of the first IDT electrode in the arrangement direction of the first electrode fingers, The second resonator is a second electrode having a second IDT electrode including a plurality of second electrode fingers; second reflectors located on both sides of the second IDT electrode in the arrangement direction of the second electrode fingers, The third resonator is a third electrode having a third IDT electrode including a plurality of third electrode fingers; third reflectors located on both sides of the third IDT electrode in the arrangement direction of the third electrode fingers, the second resonator is located between the first resonator and the third resonator, the first reflector, the second reflector, and the third reflector are a single pattern; an anti-resonance frequency determined from the pitch and duty of the second electrode fingers is higher than an anti-resonance frequency determined from the pitch and duty of the first electrode fingers and an anti-resonance frequency determined from the pitch and duty of the third electrode fingers; Elastic wave resonator.

2. the pitch of the second electrode fingers is smaller than the pitch of the first electrode fingers and the pitch of the third electrode fingers; The elastic wave resonator according to claim 1 .

3. a duty of the second electrode finger is smaller than a duty of the first electrode finger and a duty of the third electrode finger; The elastic wave resonator according to claim 1 .

4. If the total area where the first electrode fingers face each other is S1, the total area where the second electrode fingers face each other is S2, and the total area where the third electrode fingers face each other is S3, then: 0.95×S2≦S1≦1.05×S2, 0.95×S3≦S2≦1.05×S3, 0.95 × S1 ≦ S3 ≦ 1.05 × S1; The elastic wave resonator according to claim 1 .

5. further comprising a fourth resonator connected in series to the second resonator and the third resonator; The fourth resonator is a fourth electrode having a fourth IDT electrode including a plurality of fourth electrode fingers; fourth reflectors located on both sides of the fourth IDT electrode in the arrangement direction of the fourth electrode fingers, the fourth resonator is located between the second resonator and the third resonator, the first reflector, the second reflector, the third reflector, and the fourth reflector are a single pattern; the pitch of the fourth electrode fingers is smaller than the pitch of the first electrode fingers and the pitch of the third electrode fingers; The elastic wave resonator according to claim 1 .

6. An elastic wave resonator that is a split elastic wave resonator including a first resonator, a second resonator, and a third resonator connected in series, The first resonator is a first electrode having a first IDT electrode including a plurality of first electrode fingers; first reflectors located on both sides of the first IDT electrode in the arrangement direction of the first electrode fingers, The second resonator is a second electrode having a second IDT electrode including a plurality of second electrode fingers; second reflectors located on both sides of the second IDT electrode in the arrangement direction of the second electrode fingers, The third resonator is a third electrode having a third IDT electrode including a plurality of third electrode fingers; third reflectors located on both sides of the third IDT electrode in the arrangement direction of the third electrode fingers, the second resonator is located between the first resonator and the third resonator, the first reflector, the second reflector, and the third reflector are a single pattern; a length of the second electrode facing the second reflector is smaller than a length of the first electrode facing the first reflector and a length of the third electrode facing the third reflector; If the total area where the first electrode fingers face each other is S1, the total area where the second electrode fingers face each other is S2, and the total area where the third electrode fingers face each other is S3, then: 0.95×S2≦S1≦1.05×S2, 0.95×S3≦S2≦1.05×S3, 0.95 × S1 ≦ S3 ≦ 1.05 × S1; Elastic wave resonator.

7. an overlapping length between the second electrode fingers is shorter than an overlapping length between the first electrode fingers and an overlapping length between the third electrode fingers; the number of the second electrode fingers is greater than the number of the first electrode fingers and the number of the third electrode fingers; The elastic wave resonator according to claim 6 .

8. the first electrode further includes a first additional capacitance portion facing the first reflector, the third electrode further includes a third additional capacitance portion facing the third reflector; The elastic wave resonator according to claim 6 .

9. the first IDT electrode further includes first bus bars located on both sides in a direction intersecting an arrangement direction of the first electrode fingers and connected to the first electrode fingers; the second IDT electrode further includes second bus bars located on both sides in a direction intersecting the arrangement direction of the second electrode fingers and connected to the second electrode fingers, the third IDT electrode further includes third bus bars located on both sides in a direction intersecting an arrangement direction of the third electrode fingers and connected to the third electrode fingers, a length of the second bus bar facing the second reflector is shorter than a length of the first bus bar facing the first reflector and a length of the third bus bar facing the third reflector; The elastic wave resonator according to claim 6 .

10. An elastic wave resonator that is a split elastic wave resonator including a first resonator, a second resonator, and a third resonator connected in series, The first resonator is a first electrode having a first IDT electrode including a plurality of first electrode fingers; First reflectors located on both sides of the first IDT electrode in the arrangement direction of the first electrode fingers and The second resonator is a second electrode having a second IDT electrode including a plurality of second electrode fingers; second reflectors located on both sides of the second IDT electrode in the arrangement direction of the second electrode fingers, The third resonator is a third electrode having a third IDT electrode including a plurality of third electrode fingers; third reflectors located on both sides of the third IDT electrode in the arrangement direction of the third electrode fingers, the second resonator is located between the first resonator and the third resonator, the first reflector, the second reflector, and the third reflector are patterns separated from one another; When the pitch of the first electrode fingers is defined as P1, a distance between the first reflector and the second reflector is equal to or greater than 4×P1 and is greater than a distance between the first reflector and the first IDT electrode; a distance between the second reflector and the third reflector is equal to or greater than 4×P1 and is greater than a distance between the third reflector and the third IDT electrode; Elastic wave resonator.

11. In the first IDT electrode, electrode fingers located at both ends in an arrangement direction of the first electrode fingers extend from different bus bars, In the third IDT electrode, electrode fingers located at both ends in an arrangement direction of the third electrode fingers extend from different bus bars.

11. The elastic wave resonator according to claim 1, 6 or 10.

12. If the pitch of the first electrode fingers is defined as P1, the pitch of the second electrode fingers is defined as P2, and the pitch of the third electrode fingers is defined as P3, then 0.99 × P2 ≦ P1 ≦ 1.01 × P2, 0.99 × P3 ≦ P2 ≦ 1.01 × P3, and 0.99 × P1 ≦ P3 ≦ 1.01 × P1; 11. The elastic wave resonator according to claim 1, 6 or 10.

13. the first reflector, the second reflector, and the third reflector are at a floating potential and are not connected to a GND potential; 11. The elastic wave resonator according to claim 1, 6 or 10.

14. input and output terminals; a ground terminal connected to a ground potential; a series resonator connected to a series arm connecting the input terminal and the output terminal; a parallel resonator connected to a parallel arm connecting the series arm and the ground terminal; Equipped with The series resonator has an elastic wave resonator according to any one of claims 1, 6 and 10. Filter device.

15. a 90° hybrid coupler having a first port and a second port, and a third port and a fourth port to which a signal input to the first port or the second port is distributed; a first filter connected to the second port and having a first passband; a second filter connected to the third port and having a second passband different from the first passband; a third filter connected to the fourth port and having the second passband; The first filter includes an elastic wave resonator according to any one of claims 1, 6, and 10. Filter device.

16. The antenna and a filter device connected to the antenna; an IC connected to the filter device; The filter device includes an acoustic wave resonator according to any one of claims 1, 6 and 10. Communication equipment.

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