Elastic wave resonator and electronic device

Abstract

An elastic wave resonator according to the present invention includes: a piezoelectric layer having a first main surface and a second main surface; a first electrode; a second electrode; a support member provided facing the second main surface of the piezoelectric layer; a first acoustic reflecting portion provided on the first main surface side of the piezoelectric layer and consisting of a laminate of a first low acoustic impedance layer and a first high acoustic impedance layer; and a second acoustic reflecting portion provided on the second main surface side of the piezoelectric layer between the piezoelectric layer and the support member and consisting of a laminate of a second low acoustic impedance layer and a second high acoustic impedance layer. In the first acoustic reflecting portion, the first low acoustic impedance layer is made of an insulating material, and the first high acoustic impedance layer is made of a conductive material. In the second acoustic reflecting portion, the second low acoustic impedance layer and the second high acoustic impedance layer are both made of an insulating material.

Description

Acoustic wave resonator and electronic device

[0001] The present invention relates to an acoustic wave resonator and an electronic device.

[0002] Patent Document 1 describes an acoustic wave resonator (referred to in Patent Document 1 as a bulk acoustic wave (BAW) device) that includes a piezoelectric layer, top and bottom electrodes, an acoustic reflector (referred to in Patent Document 1 as a Bragg mirror), and an external terminal (referred to in Patent Document 1 as a connector) for connecting to an external circuit.

[0003] Special table 2018-514156 publication

[0004] The acoustic wave resonator disclosed in Patent Document 1 is provided on a support substrate made of a semiconductor material such as silicon. Because the acoustic reflecting portion provided on the support substrate side includes a conductor (titanium tungsten), when heat generated in the acoustic wave exciting portion is transmitted to the support substrate, the electrical properties of the support substrate change, which may result in degradation of the resonator characteristics.

[0005] An object of the present invention is to provide an acoustic wave resonator and an electronic device that can suppress deterioration of the resonator characteristics.

[0006] an elastic wave resonator according to one aspect, comprising: a piezoelectric layer having a first principal surface and a second principal surface opposite the first principal surface; a first electrode provided on the first principal surface of the piezoelectric layer; a second electrode provided on the second principal surface of the piezoelectric layer and facing the first electrode with the piezoelectric layer sandwiched therebetween; a support member provided opposite the second principal surface of the piezoelectric layer; a first acoustic reflecting portion provided on the first principal surface side of the piezoelectric layer and consisting of a laminate of a first low acoustic impedance layer and a first high acoustic impedance layer having an acoustic impedance higher than that of the first low acoustic impedance layer; and a second acoustic reflecting portion provided on the second principal surface side of the piezoelectric layer, between the piezoelectric layer and the support member, and consisting of a laminate of a second low acoustic impedance layer and a second high acoustic impedance layer having an acoustic impedance higher than that of the second low acoustic impedance layer, wherein the first low acoustic impedance layer and the first high acoustic impedance layer of the first acoustic reflecting portion are made of an insulating material and a conductive material, and the second low acoustic impedance layer and the second high acoustic impedance layer of the second acoustic reflecting portion are both made of an insulating material.

[0007] An elastic wave resonator according to one aspect includes: a piezoelectric layer having a first main surface and a second main surface opposite the first main surface; a first electrode provided on the first main surface of the piezoelectric layer; a second electrode provided on the second main surface of the piezoelectric layer and facing the first electrode across the piezoelectric layer; a support member provided opposite the second main surface of the piezoelectric layer; and a first acoustic reflecting portion provided on the first main surface side of the piezoelectric layer and consisting of a laminate of a first low acoustic impedance layer and a first high acoustic impedance layer having an acoustic impedance higher than that of the first low acoustic impedance layer, wherein the first low acoustic impedance layer of the first acoustic reflecting portion is made of an insulating material and the first high acoustic impedance layer is made of a conductive material, and the support member is provided with a cavity portion that is open to the piezoelectric layer side.

[0008] An electronic device according to one embodiment includes the above-described acoustic wave resonator, a module substrate on which the acoustic wave resonator is mounted, and a sealing resin that covers the acoustic wave resonator and contacts at least each side surface of the piezoelectric layer and the first acoustic reflector.

[0009] According to the acoustic wave resonator and electronic device of the present invention, deterioration of the resonator characteristics can be suppressed.

[0010] FIG. 1 is a circuit diagram illustrating an acoustic wave filter according to a first preferred embodiment of the present invention. FIG. 2 is a plan view illustrating the acoustic wave filter according to the first preferred embodiment of the present invention. FIG. 3 is a cross-sectional view illustrating a configuration of an acoustic wave resonator included in the acoustic wave filter according to the first preferred embodiment of the present invention. FIG. 4 is a cross-sectional view illustrating a configuration of an acoustic wave resonator according to a first modified example of the first preferred embodiment. FIG. 5 is a cross-sectional view illustrating a configuration of an acoustic wave resonator according to a second modified example of the first preferred embodiment. FIG. 6 is a cross-sectional view illustrating a portion of an electronic device including an acoustic wave resonator according to the second modified example of the first preferred embodiment. FIG. 7 is an explanatory diagram illustrating a method for manufacturing an acoustic wave resonator according to the second modified example of the first preferred embodiment. FIG. 8 is an explanatory diagram illustrating a method for manufacturing an acoustic wave resonator according to the second modified example of the first preferred embodiment. FIG. 9 is a cross-sectional view illustrating a configuration of an acoustic wave resonator according to a third modified example of the first preferred embodiment. FIG. 10 is an explanatory diagram illustrating a method for manufacturing an acoustic wave resonator according to the third modified example of the first preferred embodiment. FIG. 11 is a cross-sectional view illustrating a configuration of an acoustic wave resonator according to a second preferred embodiment of the present invention. FIG. 12 is an explanatory diagram illustrating a method for manufacturing an acoustic wave resonator according to the second preferred embodiment of the present invention. FIG. 13 is a cross-sectional view illustrating an electronic device according to a third preferred embodiment of the present invention.

[0011] 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.

[0012] 1 is a circuit diagram illustrating an acoustic wave filter according to a first embodiment. As shown in FIG. 1 , an acoustic wave filter 51 according to the first embodiment includes a plurality of series arm resonators 61 a, 61 b, 61 c, 61 d, and 61 e, a plurality of parallel arm resonators 62 a, 62 b, 62 c, and 62 d, an input terminal 60A, an output terminal 60B, and external terminals 63 and 64. At least one of the series arm resonators 61 a, 61 b, 61 c, 61 d, and 61 e and the parallel arm resonators 62 a, 62 b, 62 c, and 62 d is a bulk acoustic wave (BAW) element that utilizes bulk waves in a thickness extensional vibration mode or a thickness shear vibration mode.

[0013] The plurality of series arm resonators 61a, 61b, 61c, 61d, and 61e are connected in series to a signal path between the input terminal 60A and the output terminal 60B. The plurality of parallel arm resonators 62a, 62b, 62c, and 62d are connected in parallel between the signal path between the input terminal 60A and the output terminal 60B and external terminals 63 and 64. The acoustic wave filter 51 according to the first embodiment is a so-called ladder filter.

[0014] One terminal of each of the series-connected series arm resonators 61a, 61b, 61c, 61d, and 61e is electrically connected to the input terminal 60A, and the other terminal is electrically connected to the output terminal 60B. One terminal of the parallel arm resonator 62a is electrically connected to a signal path connecting the series arm resonators 61a and 61b, and the other terminal is electrically connected to an external terminal 63. One terminal of the parallel arm resonator 62b is electrically connected to a signal path connecting the series arm resonators 61b and 61c, and the other terminal is electrically connected to the external terminal 63. One terminal of the parallel arm resonator 62c is electrically connected to a signal path connecting the series arm resonator 61c and 61d, and the other terminal is electrically connected to an external terminal 64. One terminal of the parallel arm resonator 62 d is electrically connected to the signal path connecting the series arm resonators 61 d and 61 e , and the other terminal is electrically connected to the external terminal 64 .

[0015] The configurations and numbers of the series arm resonators 61 a, 61 b, 61 c, 61 d, and 61 e and the parallel arm resonators 62 a, 62 b, 62 c, and 62 d in the acoustic wave filter 51 can be changed as needed depending on the desired filter characteristics. For example, the acoustic wave filter 51 may include at least one series arm resonator and at least one parallel arm resonator. The acoustic wave filter 51 may also include impedance elements such as inductors and capacitors.

[0016] 2 is a plan view showing an acoustic wave filter according to the first preferred embodiment. As shown in Fig. 2, an acoustic wave filter 51 includes a plurality of series arm resonators 61a, 61b, 61c, 61d, and 61e, a plurality of parallel arm resonators 62a, 62b, 62c, and 62d, and a plurality of terminals (an input terminal 60A, an output terminal 60B, and external terminals 63, 64, 65, 66, and 67) disposed on a support member 11. The connections of the series arm resonators 61a, 61b, 61c, 61d, and 61e, the parallel arm resonators 62a, 62b, 62c, and 62d, and the plurality of terminals are the same as those shown in Fig. 1, and therefore, repeated description will be omitted.

[0017] The input terminal 60A and the output terminal 60B are located at diagonally opposite corners of the support member 11. The external terminals 63, 64, 65, and 66 are located at the periphery of the support member 11. The external terminal 67 is located in a region overlapping with the elastic wave excitation portion 28 (see FIG. 5) of the series arm resonator 61c. The location of the external terminal 67 will be described later with reference to FIG. 5.

[0018] In the following description, when it is not necessary to distinguish between the multiple series arm resonators 61a, 61b, 61c, 61d, and 61e and the multiple parallel arm resonators 62a, 62b, 62c, and 62d, they will simply be referred to as elastic wave resonators 10.

[0019] Next, the detailed configuration of the elastic wave resonator 10 (e.g., the series arm resonator 61a) included in the elastic wave filter 51 will be described. Fig. 3 is a cross-sectional view showing the configuration of an elastic wave resonator included in the elastic wave filter according to the first preferred embodiment. Note that the configuration of the elastic wave resonator 10 shown in Fig. 3 is not limited to the series arm resonator 61a, and can also be applied to the configurations of other resonators included in the elastic wave filter 51.

[0020] 3, the acoustic wave resonator 10 includes a support member 11, a piezoelectric layer 20, a first electrode 21, a second electrode 22, an interconnection 23, a via 24, a surface electrode 25, a first acoustic reflector 31, and a second acoustic reflector 32. As shown in Fig. 3, the second acoustic reflector 32, the second electrode 22 and the interconnection 23b, the piezoelectric layer 20, the first electrode 21 and the interconnection 23a, the first acoustic reflector 31, and the surface electrode 25 are stacked on the support member 11 in this order.

[0021] In the following description, the thickness direction of the piezoelectric layer 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 layer 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 layer 20 (Z direction).

[0022] In addition, in the Z direction, the direction from the support member 11 toward the outermost surface electrode 25 may be referred to as "up" or "upper," and the direction from the surface electrode 25 toward the support member 11 may be referred to as "down" or "lower." However, the terms "up" and "down" are used simply for the purpose of defining the relative positional relationship of parts, and do not limit the spatial arrangement and position of the BAW resonator.

[0023] The support member 11 is provided opposite to the second main surface 20b of the piezoelectric layer 20. The support member 11 is a flat plate-shaped member made of silicon, quartz crystal, or the like.

[0024] The piezoelectric layer 20 is flat and has a first main surface 20a and a second main surface 20b opposite to the first main surface 20a. The piezoelectric layer 20 is a substrate made of a single crystal of lithium niobate or lithium tantalate. The piezoelectric layer 20 is not limited to these, and aluminum nitride, zinc oxide, lead zirconate titanate, etc. may also be used. The thickness of the piezoelectric layer 20 is not particularly limited, but is preferably 1 μm or less. The piezoelectric layer 20 may have a structure in which multiple piezoelectric films having different polarization directions are stacked.

[0025] The first electrode 21 is provided on the top (first main surface 20a) of the piezoelectric layer 20. The second electrode 22 is provided on the bottom (second main surface 20b) of the piezoelectric layer 20. The first electrode 21 and the second electrode 22 face each other in the Z direction, sandwiching the piezoelectric layer 20 therebetween. In other words, the piezoelectric layer 20 is disposed between the first electrode 21 and the second electrode 22 in the Z direction. This allows bulk waves to propagate between the first electrode 21 and the second electrode 22. In the following description, the region where the first electrode 21 and the second electrode 22 overlap in a planar view may be described as the elastic wave exciting portion 28 of the resonator.

[0026] 2, the portions corresponding to the elastic wave exciting portion 28 of each resonator are indicated by hatching. As shown in Fig. 2, the first electrode 21 and the second electrode 22 constituting the elastic wave exciting portion 28 are each rectangular. However, this is not limiting, and the first electrode 21 and the second electrode 22 may be other shapes such as circular or polygonal.

[0027] The first electrode 21 and the second electrode 22 are formed of a conductive material such as aluminum, platinum, gold, copper, molybdenum, tungsten, titanium, chromium, ruthenium, tantalum, or iridium, or an alloy containing at least one of these materials. The first electrode 21 and the second electrode 22 may also be a laminate film containing these materials.

[0028] The lead-out wiring 23a is provided on the first main surface 20a of the piezoelectric layer 20 in the same layer as the first electrode 21, and is connected to one side of the first electrode 21 in the X direction. The lead-out wiring 23b is provided on the second main surface 20b of the piezoelectric layer 20 in the same layer as the second electrode 22, and is connected to the other side of the second electrode 22 in the X direction. The lead-out wirings 23a and 23b are formed of the same material as the first electrode 21 and the second electrode 22, respectively. However, the lead-out wirings 23a and 23b may be made of a different material from the first electrode 21 and the second electrode 22.

[0029] The first acoustic reflector 31 is provided on the first main surface 20a side of the piezoelectric layer 20, covering the first electrode 21 and the lead-out wiring 23a. In other words, the first acoustic reflector 31 is provided between the piezoelectric layer 20 and the plurality of surface electrodes 25 in the Z direction.

[0030] The first acoustic reflecting portion 31 is made of a laminate of first low acoustic impedance layers 31 a, 31 c, and 31 e having a relatively low acoustic impedance, and first high acoustic impedance layers 31 b and 31 d having a higher acoustic impedance than the first low acoustic impedance layers 31 a, 31 c, and 31 e. The first low acoustic impedance layer 31 a, the first high acoustic impedance layer 31 b, the first low acoustic impedance layer 31 c, the first high acoustic impedance layer 31 d, and the first low acoustic impedance layer 31 e are laminated in this order on the first main surface 20 a of the piezoelectric layer 20.

[0031] The first low acoustic impedance layers 31a, 31c, and 31e are made of an insulating material. The first high acoustic impedance layers 31b and 31d are made of a conductive material. The first low acoustic impedance layers 31a, 31c, and 31e are, for example, silicon oxide layers. The first high acoustic impedance layers 31b and 31d are, for example, metal materials such as tungsten, molybdenum, ruthenium, and platinum. However, without being limited thereto, the first high acoustic impedance layers 31b and 31d may be alloys containing at least one of the above metal materials. Note that, here, the conductive material refers to a material having an electrical resistivity of 1.0×10 －６ An insulating material is a material with an electrical resistivity of less than 1.0 x 10 －６ This refers to materials with a resistance of Ω·m or more.

[0032] Note that there is no particular limitation on the number of stacked first low acoustic impedance layers 31a, 31c, 31e and first high acoustic impedance layers 31b, 31d in the first acoustic reflecting portion 31. The first acoustic reflecting portion 31 may have four or fewer layers, or six or more layers. It is sufficient that at least one of the first high acoustic impedance layers 31b, 31d is disposed farther from the piezoelectric layer 20 than the first low acoustic impedance layers 31a, 31c, 31e.

[0033] The second acoustic reflecting portion 32 is made of a laminate of second low acoustic impedance layers 32 a, 32 c having a relatively low acoustic impedance and second high acoustic impedance layers 32 b, 32 d having a higher acoustic impedance than the second low acoustic impedance layers 32 a, 32 c. The second low acoustic impedance layer 32 a, the second high acoustic impedance layer 32 b, the second low acoustic impedance layer 32 c, and the second high acoustic impedance layer 32 d are laminated in this order on the second main surface 20 b of the piezoelectric layer 20.

[0034] The second low acoustic impedance layers 32 a, 32 c and the second high acoustic impedance layers 32 b, 32 d are both made of insulating materials. The second low acoustic impedance layers 32 a, 32 c are, for example, silicon oxide layers, and the second high acoustic impedance layers 32 b, 32 d are, for example, dielectric layers made of silicon nitride, aluminum oxide, tantalum oxide, hafnium oxide, or the like.

[0035] Note that there is no particular limitation on the number of layers of the second low acoustic impedance layers 32a, 32c and the second high acoustic impedance layers 32b, 32d in the second acoustic reflecting portion 32. The second acoustic reflecting portion 32 may have three or fewer layers, or five or more layers. It is sufficient that at least one of the second high acoustic impedance layers 32b, 32d is disposed farther from the piezoelectric layer 20 than the second low acoustic impedance layers 32a, 32c.

[0036] The second acoustic reflector 32 is provided on the second main surface 20b side of the piezoelectric layer 20, covering the second electrode 22 and the lead-out wiring 23b. In other words, the second acoustic reflector 32 is located on the opposite side of the piezoelectric layer 20 from the plurality of surface electrodes 25 in the Z direction, and is provided between the piezoelectric layer 20 and the support member 11.

[0037] The plurality of surface electrodes 25 are provided on the first main surface 20a side of the piezoelectric layer 20. Specifically, the plurality of surface electrodes 25 are provided on the first low acoustic impedance layer 31e, which is the outermost layer of the first acoustic reflector 31. One surface electrode 25 is electrically connected to the lead-out wiring 23a through a via 24 that penetrates the first acoustic reflector 31 in the Z direction. The other surface electrode 25 is electrically connected to the lead-out wiring 23b through a via 24 that penetrates the first acoustic reflector 31 and the piezoelectric layer 20 in the Z direction.

[0038] Each of the surface electrodes 25 is provided with an external terminal 60 (e.g., an input terminal 60A, an output terminal 60B, etc.). The external terminals, such as the input terminal 60A and the output terminal 60B, are, for example, solder bumps or Au bumps. A protective layer 41 is provided to cover the surface electrodes 25 and the first acoustic reflector 31 and has openings in areas where the external terminals 60 are provided. The protective layer 41 is formed of an insulating resin material and is also called a solder resist. With this configuration, the surface electrodes 25 and the external terminals 60 electrically connect the first electrode 21 and the second electrode 22 constituting the acoustic wave excitation unit 28 to the module substrate 101 (see FIG. 13 ), which is an external substrate. Note that the acoustic wave resonator 10 does not necessarily have to include the protective layer 41. Furthermore, the acoustic wave resonator 10 does not necessarily have to include at least one of the surface electrodes 25. Note that the surface electrodes 25 may not be provided, and the external terminals 60 may be provided on the lead-out wiring 23.

[0039] With the above-described configuration, in the elastic wave resonator 10 of this embodiment, the first acoustic reflecting portion 31 and the second acoustic reflecting portion 32 are provided on both sides of the piezoelectric layer 20, so that bulk waves such as those in the thickness-extensional vibration mode or the thickness-shear vibration mode can be confined within the piezoelectric layer 20.

[0040] The first acoustic reflecting portion 31, which is provided on the same side as the plurality of surface electrodes 25 and the external terminal 60, contains both an insulating material and a conductive material, and therefore has better thermal conductivity than a first acoustic reflecting portion 31 made of only an insulating material. More specifically, in the elastic wave resonator 10, in addition to a heat transfer path from the elastic wave excitation portion 28 through the first electrode 21, the lead wiring 23 a, the via 24, and one of the surface electrodes 25, and a heat transfer path from the elastic wave excitation portion 28 through the second electrode 22, the lead wiring 23 b, the via 24, and the other surface electrode 25, a heat transfer path is formed from the elastic wave excitation portion 28 in the Z direction through a region of the first acoustic reflecting portion 31, which includes a conductive material, that overlaps with the first high acoustic impedance layers 31 b and 31 d. This improves the heat dissipation of heat generated in the elastic wave excitation portion 28 in the elastic wave resonator 10. Furthermore, the elastic wave resonator 10 has good heat dissipation properties, which improves power durability.

[0041] In the first acoustic reflecting portion 31, the first high acoustic impedance layers 31b and 31d made of a conductive material have a higher acoustic impedance than an insulating material. That is, the ratio of the acoustic impedance of the first low acoustic impedance layers 31a, 31c, and 31e to the acoustic impedance of the first high acoustic impedance layers 31b and 31d is large. This improves the acoustic wave confinement and reflection effects in the first acoustic reflecting portion 31. This allows the acoustic wave resonator 10 to achieve good resonator characteristics.

[0042] Furthermore, in the first acoustic reflecting section 31, the first high acoustic impedance layers 31b and 31d are provided in a region overlapping with the elastic wave excitation section 28, but are not provided in a region not overlapping with the elastic wave excitation section 28. In other words, in the region overlapping with the elastic wave excitation section 28, the first low acoustic impedance layer 31a, the first high acoustic impedance layer 31b, the first low acoustic impedance layer 31c, the first high acoustic impedance layer 31d, and the first low acoustic impedance layer 31e are stacked in this order. In the region not overlapping with the elastic wave excitation section 28, the first low acoustic impedance layers 31a, 31c, and 31e are stacked in this order. This ensures flexibility in the arrangement of the vias 24 and the surface electrodes 25 while enhancing the acoustic wave confinement and reflection effects in the region overlapping with the elastic wave excitation section 28. Note that it is sufficient that the first acoustic reflecting section 31 is provided at least in the region overlapping with the elastic wave excitation section 28. That is, the first low acoustic impedance layers 31a, 31c, 31e and the first high acoustic impedance layers 31b, 31d that constitute the first acoustic reflecting section 31 may be removed in the area that does not overlap with the elastic wave excitation section 28.

[0043] A first acoustic reflector 31 containing a conductive material is provided on the first main surface 20a side (i.e., the surface electrode 25 side) of the piezoelectric layer 20, and a second acoustic reflector 32 made of an insulating material is provided on the second main surface 20b side (i.e., the support member 11 side) of the piezoelectric layer 20, so that heat generated in the elastic wave excitation unit 28 is transmitted to the surface electrode 25 side through the first acoustic reflector 31 and is less likely to be transmitted to the support member 11 side. Therefore, even when silicon, a semiconductor material, is used for the support member 11, fluctuations in the electrical properties (e.g., conductivity) of silicon due to heat from the elastic wave excitation unit 28 can be suppressed.

[0044] Furthermore, because the second acoustic reflecting portion 32 is made of an insulating material, capacitive coupling and electromagnetic field coupling can be suppressed between the elastic wave exciting portion 28 and the support member 11, which face each other across the second acoustic reflecting portion 32, compared to a configuration in which the second acoustic reflecting portion 32 includes a conductive material. Therefore, in the first embodiment, because the second acoustic reflecting portion 32 is made of an insulating material, fluctuations in the characteristics of the support member 11 due to heat from the elastic wave exciting portion 28 are suppressed, and interference between the elastic wave exciting portion 28 and the support member 11 is suppressed, resulting in good resonator characteristics.

[0045] In the second acoustic reflecting section 32, the second high acoustic impedance layers 32b, 32d are provided over the entire surface, including both the region overlapping with the elastic wave excitation section 28 and the region not overlapping with the elastic wave excitation section 28. Therefore, the process of patterning the second high acoustic impedance layers 32b, 32d can be omitted when forming the second acoustic reflecting section 32. Furthermore, in the second acoustic reflecting section 32, the second low acoustic impedance layers 32a, 32c and the second high acoustic impedance layers 32b, 32d are formed flat without any steps, which can suppress the occurrence of cracks.

[0046] Furthermore, in the elastic wave resonator 10 of this embodiment, the first acoustic reflecting portion 31 and the second acoustic reflecting portion 32 are provided on either side of the piezoelectric layer 20, and therefore the strength of the piezoelectric layer 20 can be increased compared to a configuration in which a cavity portion 12 (see FIG. 11 ) is provided in the support member 11 instead of the first acoustic reflecting portion 31 and the second acoustic reflecting portion 32.

[0047] 4 is a cross-sectional view showing the configuration of an elastic wave resonator according to a first modification of the first embodiment. As shown in FIG. 4, an elastic wave resonator 10A according to the first modification of the first embodiment has a different configuration from the first embodiment described above in that it has a high-viscoelastic layer 42.

[0048] The first acoustic reflecting portion 31 includes a first high acoustic impedance layer 31f. The high-viscoelastic layer 42 is provided to cover the first high acoustic impedance layer 31f and the first low acoustic impedance layer 31e of the first acoustic reflecting portion 31. In other words, the high-viscoelastic layer 42 is provided on the side of the first acoustic reflecting portion 31 opposite the piezoelectric layer 20, between the first acoustic reflecting portion 31 and the plurality of surface electrodes 25. The high-viscoelastic layer 42 is formed of a material having higher viscoelasticity than the first low acoustic impedance layers 31a, 31c, and 31e and the first high acoustic impedance layers 31b, 31d, and 31f of the first acoustic reflecting portion 31. Furthermore, when the elastic wave resonator 10A is mounted on the module substrate 101 (see FIG. 6 ), a sealing resin 105 is provided to cover the elastic wave resonator 10A. The high-viscoelastic layer 42 is formed of a material having higher viscoelasticity than the sealing resin 105.

[0049] The highly viscoelastic layer 42 is made of a material having a relatively high viscoelasticity, such as a polyimide resin, polybenzoxazole, a urethane resin, a silicone resin, an acrylic resin, a cycloolefin resin, a maleimide resin, etc. The sealing resin 105 is made of a material having a relatively low viscoelasticity, such as an epoxy resin (containing a filler).

[0050] In the first modified example, the high-viscoelastic layer 42 is provided closer to the surface electrode 25 than the elastic wave excitation section 28 and the first acoustic reflection section 31, so that fluctuations in the resonator characteristics due to the influence of the module substrate 101 and the sealing resin 105 (see Figure 6) can be suppressed.

[0051] (Second Modification of First Embodiment) Fig. 5 is a cross-sectional view showing the configuration of an elastic wave resonator according to a second modification of the first embodiment. Fig. 6 is a cross-sectional view showing a portion of an electronic device including an elastic wave resonator according to the second modification of the first embodiment. An elastic wave resonator 10B shown in Figs. 5 and 6 corresponds to, for example, the series arm resonator 61c in Fig. 2.

[0052] As shown in FIG. 5 , the elastic wave resonator 10B according to the second variant of the first embodiment differs from the first embodiment and the first variant described above in that at least one of the multiple surface electrodes 25 and external terminals 60 is arranged in a region that overlaps with the elastic wave excitation section 28 in a planar view.

[0053] An external terminal 67 made of a conductive material is provided on the surface electrode 25 at a position overlapping the elastic wave excitation unit 28. Setting these at ground potential is preferable because it reduces variations in characteristics due to interference with the elastic wave excitation unit. As shown in FIG. 2 , the surface electrode 25 at the position overlapping the elastic wave excitation unit 28 is pulled out to a corner of the support member 11 through a connection wiring 26 and connected to an external terminal 66 that is also at ground potential. The external terminals 66, 67 are, for example, solder bumps.

[0054] 2 , the surface electrode 25 and the external terminal 60 at the position overlapping with the elastic wave excitation unit 28 may be connected in any manner. Alternatively, the surface electrode 25 at the position overlapping with the elastic wave excitation unit 28 may be provided with only an external terminal 67 connected to a ground potential from an external substrate, and may not be connected to other wiring or terminals such as the connection wiring 26.

[0055] 6 , the elastic wave resonator 10B is mounted on the module substrate 101 via the input terminal 60A, the output terminal 60B, and the external terminal 67. The sealing resin 105 is provided to cover the elastic wave resonator 10B. The sealing resin 105 is provided to fill the space between the module substrate 101 and the protective layer 41 of the elastic wave resonator 10B. The sealing resin 105 is also provided to cover the first acoustic reflector 31, the piezoelectric layer 20, the second acoustic reflector 32, the side surface of the support member 11, and the surface of the support member 11 opposite the module substrate 101.

[0056] In the electronic device 100 including the elastic wave resonator 10B of the second modification, the surface electrode 25 and the external terminal 67 are provided in a region overlapping with the elastic wave excitation unit 28, and the external terminal 67 is in contact with the module substrate 101. This forms a heat transfer path extending in the Z direction from the elastic wave excitation unit 28 through the region of the first acoustic reflecting unit 31 overlapping with the first high acoustic impedance layers 31b, 31d, and 31f made of a conductive material, the surface electrode 25, and the external terminal 67, and reaching the module substrate 101. This allows the elastic wave resonator 10B to improve the heat dissipation performance of heat generated in the elastic wave excitation unit 28. Furthermore, the elastic wave resonator 10B has good heat dissipation performance, which improves power durability.

[0057] (Method of Manufacturing Elastic Wave Resonator According to Second Modification) Fig. 7 is a diagram illustrating a method of manufacturing an elastic wave resonator according to a second modification of the first embodiment. Fig. 8 is a diagram illustrating a method of manufacturing an elastic wave resonator according to the second modification of the first embodiment.

[0058] In the manufacturing method of the elastic wave resonator 10B, FIG. 7 shows the process up to the step of forming the second acoustic reflecting portion 32 on the second main surface 20b of the piezoelectric layer 20, and FIG. 8 shows the process from the step of forming the first acoustic reflecting portion 31 on the first main surface 20a of the piezoelectric layer 20 onward.

[0059] As shown in FIG. 7 , the piezoelectric layer 20 is bonded to a transfer substrate 200 (step ST1). The piezoelectric layer 20 is a wafer cut from a single crystal ingot of lithium niobate formed by liquid phase epitaxy (LPE). The transfer substrate 200 is, for example, a silicon substrate. In step ST1, the piezoelectric layer 20 is thinned by processes such as grinding, lapping, and polishing. The piezoelectric layer 20 may also be formed using an ion slicing method.

[0060] The second electrode 22 and the lead wiring 23b are formed on the second main surface 20b of the piezoelectric layer 20 (step ST2).

[0061] Next, a second low acoustic impedance layer 32a constituting the second acoustic reflector 32 is formed on the second main surface 20b (the surface facing the support member 11) of the piezoelectric layer 20 (step ST3). The second low acoustic impedance layer 32a is, for example, a silicon oxide film. A material with low density and low hardness is preferred for the low acoustic impedance layer.

[0062] The surface of the second low acoustic impedance layer 32a is planarized (step ST4), thereby planarizing the convex portions of the second low acoustic impedance layer 32a formed in step ST3 in correspondence with the second electrode 22 and the lead wiring 23b.

[0063] Next, the second high acoustic impedance layer 32b that constitutes the second acoustic reflector 32 is formed (step ST5). For example, a hafnium oxide film is formed as the second high acoustic impedance layer 32b. A material with high density and Young's modulus is preferably used for the high acoustic impedance layer.

[0064] Next, the second low acoustic impedance layer 32c and the second high acoustic impedance layer 32d are formed in this order (step ST6). Specifically, a silicon oxide film is formed as the second low acoustic impedance layer 32c, and a hafnium oxide film is further formed thereon as the second high acoustic impedance layer 32d, thereby forming a laminate of the silicon oxide film and the hafnium oxide film.

[0065] In the process of forming the second acoustic reflecting portion 32 shown in steps ST3 to ST6, the film properties and thicknesses of the second low acoustic impedance layers 32a, 32c and the second high acoustic impedance layers 32b, 32d are optimized according to the desired resonance characteristics. Note that the second acoustic reflecting portion 32 tends to have higher performance as a reflector if the impedance ratio of the high acoustic impedance layer / low acoustic impedance layer is large.

[0066] Next, the second high acoustic impedance layer 32d, which is the outermost layer of the second acoustic reflector 32, is planarized and smoothed, and then directly bonded to the support member 11 (step ST7). Direct bonding may be achieved by hydrophilic bonding, surface activation bonding, atomic diffusion bonding, or the like. It is preferable to use, for example, a high-resistivity silicon substrate as the support member 11. A high-resistivity silicon substrate is preferable because it has high processability and thermal conductivity, which makes it easy to reduce loss during singulation and ensures power durability. Note that steps ST7 and beyond are illustrated upside down compared to the diagrams up to step ST6.

[0067] Next, as shown in FIG. 8, the transfer substrate 200 is removed (step ST8).

[0068] The first electrode 21 and the lead wiring 23a are formed on the first main surface 20a of the piezoelectric layer 20 (step ST9).

[0069] Next, a first low acoustic impedance layer 31a, a first high acoustic impedance layer 31b, a first low acoustic impedance layer 31c, a first high acoustic impedance layer 31d, a first low acoustic impedance layer 31e, and a first high acoustic impedance layer 31f, which constitute a first acoustic reflecting portion 31, are formed in this order on a first main surface 20a (the surface on which the surface electrode 25 is provided) of the piezoelectric layer 20 (step ST10). Silicon oxide films are formed as the first low acoustic impedance layers 31a, 31c, and 31e, and tungsten films are formed as the first high acoustic impedance layers 31b, 31d, and 31f.

[0070] A tungsten film is formed on each of the first high acoustic impedance layers 31b, 31d, and 31f in an area overlapping with the elastic wave excitation section 28, and the tungsten film is removed from an area not overlapping with the elastic wave excitation section 28. Furthermore, a silicon oxide film is formed on each of the first low acoustic impedance layers 31c and 31e formed overlapping with the first high acoustic impedance layers 31b and 31d, and then the layers are planarized.

[0071] In step ST10, by reducing the pattern variation of the first high acoustic impedance layers 31b, 31d, and 31f, variation in the resonator characteristics of the elastic wave resonator 10B can be suppressed. Therefore, it is preferable to pattern the first high acoustic impedance layers 31b, 31d, and 31f using processing techniques, materials, and equipment that are effective for achieving high precision. Furthermore, a material with high density and Young's modulus is preferable for the high acoustic impedance layers, and is not limited to tungsten. Molybdenum, ruthenium, platinum, etc. can also be used.

[0072] Next, a high-viscoelastic layer 42 having higher viscoelasticity than the material used for the first acoustic reflector 31 is formed (step ST11). The high-viscoelastic layer 42 is made of a material having higher viscoelasticity than the sealing resin 105 (see FIG. 6 ) that covers the acoustic wave resonator 10B. An example of the high-viscoelastic layer 42 is a polyimide film. Alternatively, the high-viscoelastic layer 42 may be made of an epoxy-based material other than polyimide, an olefin-based resin, benzocyclobutene, polybenzoxazole, silicone, or the like.

[0073] Next, the surface electrode 25, the connection wiring 26, and the via 24 are formed by lift-off (step ST12). In step ST12, first, through holes penetrating the high-viscoelastic layer 42 and the first acoustic reflector 31, and through holes penetrating the high-viscoelastic layer 42, the first acoustic reflector 31, and the piezoelectric layer 20 are formed by RIE (reactive ion etching) at positions overlapping with the lead-out wirings 23a and 23b. After forming a resist pattern, a Cu / Ti film is deposited, and the surface electrode 25, the connection wiring 26, and the via 24 are formed by lift-off. In step ST12, the surface electrode 25 is also provided in a region overlapping with the elastic wave excitation unit 28.

[0074] Next, a protective layer 41 is formed to cover the surface electrodes 25 and the connection wiring 26, and openings are formed in the protective layer 41 in areas where terminals such as the input terminal 60A, the output terminal 60B, and the external terminal 67 will be provided. Solder bumps are formed on the plurality of surface electrodes 25 as the input terminals 60A, the output terminals 60B, and the external terminals 67 (step ST13). At this time, the external terminals 67 are provided on the surface electrodes 25 in areas overlapping with the elastic wave excitation units 28.

[0075] Next, the piezoelectric layer 20 is singulated into individual pieces to manufacture the elastic wave resonators 10B. Through the above-described process, a first acoustic reflector 31 containing an insulating material and a metal material is formed on the surface electrode 25 side of the piezoelectric layer 20, and a second acoustic reflector 32 made of an insulating material is formed on the support member 11 side opposite the surface electrode 25.

[0076] 7 and 8, the method for manufacturing the elastic wave resonator 10B according to the second modified example has been described. However, by omitting step ST11 or by modifying a part of step ST12, the elastic wave resonators 10 and 10A according to the first embodiment and the first modified example can be manufactured.

[0077] 9 is a cross-sectional view showing the configuration of an elastic wave resonator according to a third modification of the first embodiment. As shown in FIG. 9, an elastic wave resonator 10C according to the third modification of the first embodiment differs from the second modification of the first embodiment in that the second acoustic reflecting portion 32A includes a conductive material.

[0078] A second low acoustic impedance layer 32Aa, a second high acoustic impedance layer 32Ab, a second low acoustic impedance layer 32Ac, a second high acoustic impedance layer 32Ad, a second low acoustic impedance layer 32Ae, a second high acoustic impedance layer 32Af, and a second low acoustic impedance layer 32Ag are stacked in this order on the second main surface 20b of the piezoelectric layer 20.

[0079] The second low acoustic impedance layers 32Aa, 32Ac, 32Ae, and 32Ag are made of an insulating material. The second high acoustic impedance layers 32Ab, 32Ad, and 32Af are made of a conductive material. The second low acoustic impedance layers 32Aa, 32Ac, 32Ae, and 32Ag are, for example, silicon oxide layers. The second high acoustic impedance layers 32Ab, 32Ad, and 32Af are, for example, metal materials such as tungsten, molybdenum, ruthenium, and platinum. However, without being limited thereto, the second high acoustic impedance layers 32Ab, 32Ad, and 32Af may be alloys containing at least one of the above metal materials.

[0080] The second low acoustic impedance layers 32Aa, 32Ac, 32Ae, and 32Ag are made of the same material as the first low acoustic impedance layers 31a, 31c, and 31e of the first acoustic reflecting portion 31. The second high acoustic impedance layers 32Ab, 32Ad, and 32Af are made of the same material as the first high acoustic impedance layers 31b, 31d, and 31f of the first acoustic reflecting portion 31. However, without being limited to this, the second acoustic reflecting portion 32A may be made of a different material from that of the first acoustic reflecting portion 31.

[0081] In the elastic wave resonator 10C of the third modified example, both the first acoustic reflecting portion 31 and the second acoustic reflecting portion 32A contain a conductive material, and an external terminal 67 is provided on the surface electrode 25 in a region overlapping with the elastic wave exciting portion 28. Therefore, the elastic wave resonator 10C of the third modified example can efficiently dissipate heat generated in the elastic wave exciting portion 28 to the outside.

[0082] 10 is an explanatory diagram for describing a method for manufacturing an elastic wave resonator according to a third modified example of the first embodiment. Note that, in FIG. 10 , details common to the method for manufacturing elastic wave resonator 10B according to the second modified example described above will be omitted.

[0083] 10 , a second low acoustic impedance layer 32Aa constituting a second acoustic reflector 32A is formed on the second main surface 20b of the piezoelectric layer 20 and then planarized (step ST21). A silicon oxide film is formed as the second low acoustic impedance layer 32Aa. Prior to step ST21, similar to steps ST1 to ST3 (see FIG. 7 ) described above, the piezoelectric layer 20 is bonded to the transfer substrate 200, and the second electrode 22 and the lead wiring 23b are formed on the second main surface 20b of the piezoelectric layer 20.

[0084] Next, the second high acoustic impedance layer 32Ab, the second low acoustic impedance layer 32Ac, the second high acoustic impedance layer 32Ad, the second low acoustic impedance layer 32Ae, the second high acoustic impedance layer 32Af, and the second low acoustic impedance layer 32Ag are formed (step ST22). Silicon oxide films are formed as the second low acoustic impedance layers 32Ac, 32Ae, and 32Ag. Tungsten films are formed as the second high acoustic impedance layers 32Ab, 32Ad, and 32Af. The tungsten films are formed in the regions of the second high acoustic impedance layers 32Ab, 32Ad, and 32Af that overlap with the acoustic wave excitation unit 28, and the tungsten films are removed from the regions that do not overlap with the acoustic wave excitation unit 28. This forms the second acoustic reflecting portion 32A, which includes an insulating material and a conductive material.

[0085] Next, similarly to steps ST7 and ST8 described above, the second acoustic reflecting portion 32A and the support member 11 are joined together, and then the transfer substrate 200 is removed (step ST23).

[0086] 8 are performed. That is, the first electrode 21, the lead wiring 23a, the first acoustic reflector 31, the highly viscoelastic layer 42, the surface electrode 25, the protective layer 41, and the respective terminals are formed on the first main surface 20a of the piezoelectric layer 20.

[0087] Next, the elastic wave resonator 10C is manufactured by singulating the piezoelectric layer 20. Through the above-described process, a first acoustic reflector 31 containing an insulating material and a conductive material is formed on the surface electrode 25 side of the piezoelectric layer 20, and a second acoustic reflector 32A containing an insulating material and a conductive material is formed on the support member 11 side of the piezoelectric layer 20 opposite the surface electrode 25.

[0088] 11 is a cross-sectional view showing the configuration of an elastic wave resonator according to a second embodiment. As shown in FIG. 11 , an elastic wave resonator 10D according to the second embodiment differs from the first embodiment in that, instead of the second acoustic reflecting portion 32, a cavity 12 that opens to the piezoelectric layer 20 side is provided in the support member 11.

[0089] The cavity 12 is provided in a region that overlaps with the elastic wave excitation portion 28 in a plan view. At least a portion of the second electrode 22 and the lead wiring 23b is disposed within the cavity 12. A portion of the support member 11 where the cavity 12 is not formed contacts the second main surface 20b of the piezoelectric layer 20. In the second embodiment, the cavity 12 is provided on the second main surface 20b of the piezoelectric layer 20. Therefore, compared to the first embodiment in which, for example, the second acoustic reflector 32 (see FIG. 3 ) made of only an insulating material is provided, the energy trapping effect of the elastic wave resonator 10D is enhanced and favorable resonator characteristics are obtained.

[0090] Furthermore, the elastic wave resonator 10D according to the second embodiment has a first acoustic reflector 31 containing a conductive material on the first main surface 20a side (i.e., the surface electrode 25 side) of the piezoelectric layer 20, and a cavity 12 on the second main surface 20b side (i.e., the support member 11 side) of the piezoelectric layer 20. Therefore, heat generated in the elastic wave excitation unit 28 is transferred to the surface electrode 25 side through the first acoustic reflector 31, and is less likely to be transferred to the support member 11 side in which the cavity 12 is provided. Therefore, even when silicon, a semiconductor material, is used for the support member 11, fluctuations in the electrical properties (e.g., conductivity) of silicon due to heat from the elastic wave excitation unit 28 can be suppressed.

[0091] The elastic wave resonator 10D according to the second preferred embodiment also includes a high-viscoelastic layer 42 and a high Young's modulus layer 44. The high-viscoelastic layer 42 is similar to that in the first modified example (see FIG. 4 ) described above, and therefore a repeated description will be omitted.

[0092] The high Young's modulus layer 44 is disposed on the side of the first acoustic reflector 31 opposite the piezoelectric layer 20, between the first acoustic reflector 31 and the plurality of surface electrodes 25, and is provided in a region overlapping at least the cavity 12 in a planar view. More specifically, the high Young's modulus layer 44 is disposed between the high viscoelastic layer 42 and the plurality of surface electrodes 25. The high Young's modulus layer 44 has a higher Young's modulus than at least the first low acoustic impedance layers 31a, 31c, and 31e and the first high acoustic impedance layers 31b, 31d, and 31f of the first acoustic reflector 31, among the layers arranged to overlap the cavity 12. More preferably, the high Young's modulus layer 44 has a higher Young's modulus than any of the materials of the layers arranged to overlap the elastic wave excitation unit 28 in a planar view (the first acoustic reflector 31, the high viscoelastic layer 42, the sealing resin 105, etc.).

[0093] The high Young's modulus layer 44 is formed, for example, from an insulating material or a semiconductive material. Examples of preferred materials for the high Young's modulus layer 44 include thinned high-resistivity silicon, quartz, aluminum oxide, and silicon oxide. For example, in the case of high-resistivity silicon, its thickness is preferably approximately 0.5 μm to 10 μm. With this thickness, even when high-resistivity silicon, a semiconductive material, is selected for the high Young's modulus layer 44, its conductivity and the effect on resonance characteristics due to the increase in conductivity caused by carriers generated when heat is applied are limited. Furthermore, the high Young's modulus layer 44 is preferably made of an inorganic material. This is because, while organic materials such as resins soften and their Young's modulus decreases with increasing temperature, inorganic materials do not soften as easily as organic materials.

[0094] In the second embodiment, by providing the high Young's modulus layer 44, even in a configuration having a cavity 12, it is possible to suppress deterioration of the resonance characteristics and prevent deformation of the cavity 12 due to external pressure and damage to the piezoelectric layer 20. Furthermore, in the second embodiment, it is possible to suppress fluctuations in the resonance frequency due to deformation of the piezoelectric layer 20.

[0095] The support member 11 may include a support substrate (e.g., a silicon substrate) and an intermediate layer (insulating layer). That is, the piezoelectric layer 20 is bonded to the support substrate directly or via the intermediate (insulating) layer. The cavity 12 may be formed in the intermediate layer. In this case, the support substrate (silicon substrate) and the intermediate layer may have a frame-like shape, thereby forming the cavity 12. Alternatively, the cavity 12 may be formed in the intermediate layer.

[0096] 12 is an explanatory diagram for describing a method for manufacturing an elastic wave resonator according to a second embodiment. Note that in FIG. 12, details common to the method for manufacturing elastic wave resonator 10B according to the second modified example described above are omitted.

[0097] As shown in FIG. 12, the piezoelectric layer 20 is bonded to the transfer substrate 200, and the second electrodes 22 and the lead wirings 23b are formed on the second main surface 20b of the piezoelectric layer 20 (step ST31).

[0098] Next, the cavity 12 is formed in the support member 11 by wet etching, and the second main surface 20b of the piezoelectric layer 20 is bonded to the support member 11 (step ST32). The bonding of the support member 11 can be performed by direct bonding such as hydrophilic bonding or surface activation bonding.

[0099] Next, the transfer substrate 200 is removed (step ST33). The transfer substrate 200 may be removed by wet etching, or may be separated at the bonding surface using a laser.

[0100] Next, similarly to steps ST10 and ST11 described above, the first acoustic reflecting portion 31 and the high-viscoelastic layer 42 are formed on the first main surface 20a of the piezoelectric layer 20 (step ST34). In step ST34, a high Young's modulus layer 44 is further formed. The high Young's modulus layer 44 has a higher Young's modulus than any of the materials of the layers arranged to overlap the elastic wave exciting portion 28 in plan view, such as the first acoustic reflecting portion 31 and the high-viscoelastic layer 42.

[0101] Next, similar to steps ST12 and ST13 described above, the surface electrodes 25, connection wiring 26, and vias 24 are formed, the protective layer 41 is patterned, and solder bumps such as the input terminals 60A, output terminals 60B, and external terminals 67 are formed (step ST35).

[0102] Next, the piezoelectric layer 20 is singulated into individual pieces to manufacture the elastic wave resonators 10D. Through the above-described process, a first acoustic reflector 31 containing an insulating material and a conductive material is formed on the surface electrode 25 side of the piezoelectric layer 20, and a cavity 12 is formed as a second acoustic reflector on the support member 11 side opposite the surface electrode 25.

[0103] 13 is a cross-sectional view showing an electronic device according to a third embodiment. An electronic device 100 according to a fourth embodiment is a communication module used in, for example, a mobile terminal such as a mobile phone, a smartphone, or a tablet terminal, or a personal computer with a communication function. Alternatively, the electronic device 100 may be used for backhaul communication between base stations and between a base station and a core network.

[0104] As shown in FIG. 13, the electronic device 100 includes a module substrate 101, acoustic wave filters 51 and 52, a power amplifier 102, a high-frequency switch 103, surface-mounted components 104 (such as inductors and coils), and a sealing resin 105.

[0105] The module substrate 101 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 101 may be a single-layer substrate or a multi-layer substrate in which multiple dielectric layers are stacked.

[0106] The acoustic wave filters 51 and 52 include at least one of the acoustic wave resonators 10, 10A-10D of the first and second embodiments described above. The acoustic wave filter 52 may have a configuration similar to or different from that of the acoustic wave filter 51. The acoustic wave filters 51 and 52 including the acoustic wave resonator 10 have a first acoustic reflecting portion 31 containing an insulating material and a conductive material on the surface electrode 25 side (module substrate 101 side). Therefore, heat generated in the acoustic wave excitation portion 28 is efficiently conducted to the module substrate 101 through the first acoustic reflecting portion 31. Therefore, the acoustic wave filters 51 and 52 can improve the heat dissipation performance of the heat generated in the acoustic wave excitation portion 28.

[0107] Furthermore, the acoustic wave filters 51 and 52 each having the acoustic wave resonator 10 are provided with the second acoustic reflector 32 made of an insulating material on the support member 11 side (the side opposite the module substrate 101), and the sealing resin 105 covers the support member 11. This means that heat generated in the acoustic wave excitation unit 28 is less likely to be transmitted to the support member 11 side. Therefore, even when the support member 11 is made of silicon, a semiconductor material, fluctuations in the electrical properties (e.g., conductivity) of the support member 11 due to the heat from the acoustic wave excitation unit 28 can be suppressed. Therefore, the acoustic wave filters 51 and 52 each having the acoustic wave resonator 10 have excellent filter characteristics.

[0108] The sealing resin 105 is formed by transfer molding to cover the acoustic wave filters 51 and 52, the power amplifier 102, the high-frequency switch 103, and the surface-mounted components 104. As described above, the sealing resin 105 covers the side surfaces of the support member 11, the first acoustic reflecting portion 31, and the second acoustic reflecting portion 32 of the acoustic wave resonator 10. In other words, no other package or connecting member is present between the acoustic wave resonator 10 and the module substrate 101 or the sealing resin 105. This allows the electronic device 100 to be miniaturized.

[0109] It should be noted that the electronic device 100 shown in FIG. 13 is merely a schematic illustration, and the types, number, arrangement, etc. of the components mounted on the electronic device 100 can be changed as appropriate.

[0110] 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.

[0111] The present disclosure may also have the following configurations.

[0112] (1) A piezoelectric layer having a first main surface and a second main surface opposite to the first main surface; a first electrode provided on the first main surface of the piezoelectric layer; a second electrode provided on the second main surface of the piezoelectric layer and facing the first electrode with the piezoelectric layer sandwiched therebetween; a support member provided opposite the second main surface of the piezoelectric layer; a first acoustic reflecting section provided on the first main surface side of the piezoelectric layer and consisting of a laminate of a first low acoustic impedance layer and a first high acoustic impedance layer having an acoustic impedance higher than that of the first low acoustic impedance layer; and a second acoustic reflecting section provided on the second main surface side of the piezoelectric layer, between the piezoelectric layer and the support member, and consisting of a laminate of a second low acoustic impedance layer and a second high acoustic impedance layer having an acoustic impedance higher than that of the second low acoustic impedance layer, wherein the first low acoustic impedance layer of the first acoustic reflecting section is made of an insulating material and the first high acoustic impedance layer is made of a conductive material, (2) An elastic wave resonator according to (1), further comprising a high-viscoelastic layer disposed on the opposite side of the first acoustic reflecting section from the piezoelectric layer, the high-viscoelastic layer having higher viscoelasticity than the first low acoustic impedance layer and the first high acoustic impedance layer of the first acoustic reflecting section and the second low acoustic impedance layer and the second high acoustic impedance layer of the second acoustic reflecting section. (3) An elastic wave resonator comprising: a piezoelectric layer having a first main surface and a second main surface opposite to the first main surface; a first electrode provided on the first main surface of the piezoelectric layer; a second electrode provided on the second main surface of the piezoelectric layer and facing the first electrode with the piezoelectric layer sandwiched therebetween; a support member provided opposite the second main surface of the piezoelectric layer; and a first acoustic reflecting portion provided on the first main surface side of the piezoelectric layer and consisting of a laminate of a first low acoustic impedance layer and a first high acoustic impedance layer having an acoustic impedance higher than that of the first low acoustic impedance layer, wherein the first low acoustic impedance layer of the first acoustic reflecting portion is made of an insulating material and the first high acoustic impedance layer is made of a conductive material, and the support member is provided with a cavity portion opening to the piezoelectric layer side.(4) The elastic wave resonator according to (3), comprising: a high viscoelastic layer disposed on the opposite side of the first acoustic reflecting section from the piezoelectric layer, the high viscoelasticity layer having higher viscoelasticity than the first low acoustic impedance layer and the first high acoustic impedance layer of the first acoustic reflecting section; and a high Young's modulus layer disposed on the opposite side of the first acoustic reflecting section from the piezoelectric layer, the high Young's modulus layer being higher than the first high acoustic impedance layer and the first low acoustic impedance layer of the first acoustic reflecting section, and being provided in a region overlapping with at least the cavity in a plan view. (5) The elastic wave resonator according to any one of (1) to (4), comprising: a plurality of external terminals provided on the first main surface side of the piezoelectric layer for electrically connecting the first electrode and the second electrode to an external substrate, wherein when a region where the first electrode and the second electrode overlap with each other across the piezoelectric layer is defined as an elastic wave exciting section, at least one external terminal of the plurality of external terminals is arranged in a region overlapping with the elastic wave exciting section in a plan view. (6) An electronic device comprising: an elastic wave resonator according to any one of (1) to (5); a module substrate on which the elastic wave resonator is mounted; and a sealing resin provided to cover the elastic wave resonator and in contact with at least each side surface of the piezoelectric layer and the first acoustic reflecting portion.

[0113] (7) A piezoelectric layer having a first main surface and a second main surface opposite to the first main surface, a first electrode provided on the first main surface of the piezoelectric layer, a second electrode provided on the second main surface of the piezoelectric layer and facing the first electrode with the piezoelectric layer sandwiched therebetween, a plurality of external terminals provided on the first main surface side of the piezoelectric layer for electrically connecting the first electrode and the second electrode to an external substrate, a support member provided opposite the second main surface of the piezoelectric layer, a first acoustic reflecting section provided between the piezoelectric layer and the plurality of external terminals on the first main surface side of the piezoelectric layer and consisting of a laminate of a first low acoustic impedance layer and a first high acoustic impedance layer having an acoustic impedance higher than that of the first low acoustic impedance layer, and a second acoustic reflecting section provided between the piezoelectric layer and the support member on the second main surface side of the piezoelectric layer and consisting of a laminate of a second low acoustic impedance layer and a second high acoustic impedance layer having an acoustic impedance higher than that of the second low acoustic impedance layer, an elastic wave resonator in which, when the first low acoustic impedance layer of the first acoustic reflecting portion is made of an insulating material and the first high acoustic impedance layer is made of a conductive material, the second low acoustic impedance layer of the second acoustic reflecting portion is made of an insulating material and the second high acoustic impedance layer is made of a conductive material, and when a region where the first electrode and the second electrode overlap with the piezoelectric layer sandwiched therebetween is defined as an elastic wave exciting portion, at least one external terminal of the plurality of external terminals is arranged in a region that overlaps with the elastic wave exciting portion in a planar view.

[0114] REFERENCE SIGNS LIST 10, 10A, 10B, 10C, 10D Acoustic wave resonator 11 Support member 12 Cavity 20 Piezoelectric layer 20a First main surface 20b Second main surface 21 First electrode 22 Second electrode 25 Surface electrode 28 Acoustic wave excitation section 31 First acoustic reflection section 31a, 31c First low acoustic impedance layer 31b, 31d First high acoustic impedance layer 32, 32A Second acoustic reflection section 32a, 32c, 32Aa, 32Ac, 32Ae, 32Ag Second low acoustic impedance layer 32b, 32d, 32Ab, 32Ad, 32Af Second high acoustic impedance layer 42 High viscoelastic layer 44 High Young's modulus layer 51, 52 Acoustic wave filter 61a, 61b, 61c, 61d, 61e Series arm resonator 62a, 62b, 62c, 62d parallel arm resonators 100 electronic device 101 module substrate 105 sealing resin

Claims

a piezoelectric layer having a first major surface and a second major surface opposite the first major surface; a first electrode provided on the first main surface of the piezoelectric layer; a second electrode provided on the second main surface of the piezoelectric layer and facing the first electrode across the piezoelectric layer; a support member provided opposite the second main surface of the piezoelectric layer; a first acoustic reflecting portion provided on the first principal surface side of the piezoelectric layer and including a laminate of a first low acoustic impedance layer and a first high acoustic impedance layer having an acoustic impedance higher than that of the first low acoustic impedance layer; a second acoustic reflecting portion provided between the piezoelectric layer and the support member on the second main surface side of the piezoelectric layer, the second acoustic reflecting portion being a laminate of a second low acoustic impedance layer and a second high acoustic impedance layer having an acoustic impedance higher than that of the second low acoustic impedance layer; the first low acoustic impedance layer of the first acoustic reflecting portion is made of an insulating material, and the first high acoustic impedance layer is made of a conductive material; The second low acoustic impedance layer and the second high acoustic impedance layer of the second acoustic reflecting portion are both made of an insulating material. Elastic wave resonator. 　 a high viscoelastic layer disposed on the opposite side of the piezoelectric layer of the first acoustic reflecting section, the high viscoelastic layer having higher viscoelasticity than the first low acoustic impedance layer and the first high acoustic impedance layer of the first acoustic reflecting section and the second low acoustic impedance layer and the second high acoustic impedance layer of the second acoustic reflecting section; The elastic wave resonator according to claim 1 . 　 a piezoelectric layer having a first major surface and a second major surface opposite the first major surface; a first electrode provided on the first main surface of the piezoelectric layer; a second electrode provided on the second main surface of the piezoelectric layer and facing the first electrode across the piezoelectric layer; a support member provided opposite the second main surface of the piezoelectric layer; a first acoustic reflecting portion provided on the first principal surface side of the piezoelectric layer and consisting of a laminate of a first low acoustic impedance layer and a first high acoustic impedance layer having an acoustic impedance higher than that of the first low acoustic impedance layer; the first low acoustic impedance layer of the first acoustic reflecting portion is made of an insulating material, and the first high acoustic impedance layer is made of a conductive material; The support member has a cavity that opens to the piezoelectric layer side. Elastic wave resonator. 　 a high viscoelastic layer disposed on the opposite side of the piezoelectric layer of the first acoustic reflecting unit and having higher viscoelasticity than the first low acoustic impedance layer and the first high acoustic impedance layer of the first acoustic reflecting unit; a high Young's modulus layer that is disposed on the opposite side of the piezoelectric layer of the first acoustic reflecting portion, is provided in a region that overlaps with at least the cavity portion in a plan view, and has a higher Young's modulus than the first high acoustic impedance layer and the first low acoustic impedance layer of the first acoustic reflecting portion. The elastic wave resonator according to claim 3 . 　 a plurality of external terminals provided on the first principal surface side of the piezoelectric layer for electrically connecting the first electrode and the second electrode to an external substrate; When a region where the first electrode and the second electrode overlap with the piezoelectric layer sandwiched therebetween is defined as an elastic wave exciting portion, At least one of the plurality of external terminals is disposed in a region overlapping with the elastic wave excitation unit in a plan view. The elastic wave resonator according to claim 1 . 　 an elastic wave resonator according to any one of claims 1 to 5; a module substrate on which the acoustic wave resonator is mounted; a sealing resin that covers the elastic wave resonator and is in contact with at least each side surface of the piezoelectric layer and the first acoustic reflecting portion. Electronic devices.

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