Acoustic wave device, splitter, and communication apparatus

Abstract

To realize an acoustic wave device of which a capacitance is large, and an impedance is small.SOLUTION: An acoustic wave device includes: a piezoelectric material; a first IDT electrode positioned to an upper direction of the piezoelectric material; and a multilayer film positioned to a lower direction of the piezoelectric material. The first IDT electrode includes a part that is opposite each other, includes a first inter-digital electrode and a second inter-digital electrode, constructed so as to be connected to a different potential. The first inter-digital electrode is constructed by a first bus bar and a plurality of first electrode fingers. The second inter-digital electrode is constructed by a second bus bar and a plurality of second electrode fingers. The multilayer film includes: a low acoustic impedance layer containing a part of which an acoustic impedance is lower as compared with a layer that is at least one layer and is contacted to an upper direction; and a high acoustic impedance layer containing a part of which the acoustic impedance is higher as compared with the layer that is at least one layer and is contacted to the upper direction. At least one of the low acoustic impedance layer and the high acoustic impedance layer contains a metal part, and an insulation body part.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Acoustic wave devices that utilize acoustic waves are known. Examples of the acoustic wave devices include a surface acoustic wave (SAW) device or a bulk acoustic wave (BAW) device. The acoustic wave device includes, for example, a substrate having piezoelectricity at least on its upper surface, and an excitation electrode that applies a voltage to the upper or lower surface of the substrate to excite an acoustic wave. In the acoustic wave device, a standing wave of an acoustic wave having a wavelength twice the pitch of the electrode fingers is formed, and the resonant frequency of the acoustic wave device is set by the pitch of the electrode fingers. Patent Document 1 discloses an acoustic wave element having a support substrate, a multilayer film, a piezoelectric layer, and an IDT electrode. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2023 / 033032 Summary of the Invention [Problem to be solved by the invention]

[0004] Depending on the design of the acoustic wave device, the acoustic wave device may have a low capacitance and a high impedance. [Means for solving the problem]

[0005] An elastic wave device according to one embodiment of the present disclosure comprises a piezoelectric body, a first IDT (Inter Digital Transducer) electrode located above the piezoelectric body, and a multilayer film located below the piezoelectric body, the first IDT electrode having portions facing each other and including a first comb tooth electrode and a second comb tooth electrode configured to be connected to different potentials, the first comb tooth electrode being configured by a first bus bar and a plurality of first electrode fingers, the second comb tooth electrode being configured by a second bus bar and a plurality of second electrode fingers, the multilayer film having at least one low acoustic impedance layer including a portion having a lower acoustic impedance than a layer in contact with it above, and at least one high acoustic impedance layer including a portion having a higher acoustic impedance than a layer in contact with it above, and at least one of the low acoustic impedance layer or the high acoustic impedance layer includes a first metal portion and an insulator portion. Effect of the Invention

[0006] According to one aspect of the present disclosure, an acoustic wave device having large capacitance and small impedance can be realized. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic cross-sectional view of an elastic wave device according to an embodiment of the present disclosure. [Diagram 2] FIG. 1 is a schematic plan view of an elastic wave device according to an embodiment of the present disclosure. [Diagram 3] FIG. 1 is a schematic plan view of an elastic wave device according to an embodiment of the present disclosure. [Figure 4] FIG. 1 is a schematic plan view of an elastic wave device according to an embodiment of the present disclosure. [Diagram 5] FIG. 1 is a schematic plan view of an elastic wave device according to an embodiment of the present disclosure. [Figure 6] FIG. 1 is a schematic plan view of an elastic wave device according to an embodiment of the present disclosure. [Figure 7] FIG. 1 is a schematic cross-sectional view of an elastic wave device according to an embodiment of the present disclosure. [Figure 8]FIG. 1 is a schematic cross-sectional view of an elastic wave device according to an embodiment of the present disclosure. [Figure 9] FIG. 1 is a schematic plan view of an elastic wave device according to an embodiment of the present disclosure. [Figure 10] FIG. 1 is a schematic plan view of an elastic wave device according to an embodiment of the present disclosure. [Figure 11A] FIG. 1 is a schematic plan view of an elastic wave device according to an embodiment of the present disclosure. [Figure 11B] FIG. 1 is a schematic plan view of an elastic wave device according to an embodiment of the present disclosure. [Figure 12] 2 is a schematic cross-sectional view of an elastic wave device according to a preferred embodiment of the present disclosure taken along line XX. FIG. [Figure 13] FIG. 1 is a schematic cross-sectional view of an elastic wave device according to an embodiment of the present disclosure. [Figure 14] FIG. 1 is a schematic plan view of an elastic wave device according to an embodiment of the present disclosure. [Figure 15] FIG. 1 is a schematic cross-sectional view of an elastic wave device according to an embodiment of the present disclosure. [Figure 16] FIG. 1 is a schematic cross-sectional view of an elastic wave device according to an embodiment of the present disclosure. [Figure 17] FIG. 2 is a schematic circuit diagram of a duplexer according to an embodiment of the present disclosure. [Figure 18] FIG. 2 is a schematic circuit diagram of a communication device according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the drawings used in the following description are schematic, and the dimensional ratios and the like in the drawings do not necessarily match those in reality. Furthermore, the dimensional ratios of the drawings do not necessarily match each other.

[0009] In the elastic wave device according to the present disclosure, either direction may be upward or downward. However, for convenience, in the following, an orthogonal coordinate system represented by the D1, D2, and D3 axes is attached to the drawings, and terms such as upper surface and lower surface may be used with the positive side of the D3 axis being upward. Furthermore, when referring to a plan view or a plan perspective view, it refers to a view in the D3 direction unless otherwise specified. The D1 axis is defined to be parallel to the arrangement direction of the electrode fingers, which will be described later. The D2 axis is defined to be parallel to the extension direction of the electrode fingers, which will be described later. The D3 axis is defined to be perpendicular to the upper surface of the piezoelectric body.

[0010] The following are embodiments of the present disclosure. The configurations described in the following embodiments may be freely combined with other embodiments.

[0011] [First embodiment] A first embodiment of an elastic wave device according to the present disclosure will be described. Fig. 1 is a schematic diagram showing a cross-sectional structure of a portion of an elastic wave device 1. The elastic wave device 1 has a support substrate 2, a multilayer film 3, a piezoelectric body 4, and an electrode layer 5, and is configured by stacking the support substrate 2, the multilayer film 3, the piezoelectric body 4, and the electrode layer 5 in this order from top to bottom.

[0012] (Support substrate) The support substrate 2 is a substrate that supports the multilayer film 3, the piezoelectric body 4, and the electrode layer 5. The material of the support substrate 2 is not particularly limited as long as it has a certain strength. For example, when the support substrate 2 is made of a material having a smaller linear expansion coefficient than the piezoelectric body 4, the deformation of the piezoelectric body 4 due to temperature change can be reduced, thereby reducing the change in electrical characteristics due to temperature change. The material of the support substrate 2 may be a material having a higher transverse wave sound velocity of the propagating elastic wave than the transverse wave sound velocity of the elastic wave propagating through the piezoelectric body 4. When a material having a higher transverse wave sound velocity of the propagating elastic wave than the transverse wave sound velocity of the elastic wave propagating through the piezoelectric body 4 is selected as the material of the support substrate 2, the leakage of the elastic wave to the support substrate 2 side can be reduced, and an elastic wave device 1 with excellent frequency characteristics can be provided. The support substrate 2 may be a material with high thermal conductivity. For example, when a material with a higher thermal conductivity than the piezoelectric body 4 or the multilayer film 3 is selected, an elastic wave device 1 with excellent heat dissipation can be provided.

[0013] Examples of materials for the support substrate 2 include single crystals of sapphire (Al2O3) and silicon (Si). In this embodiment, the support substrate 2 is made of Si. explain.

[0014] The thickness of the support substrate 2 is not particularly limited, but is, for example, thicker than the thickness of the piezoelectric body 4 .

[0015] (electrode layer) The electrode layer 5 has an IDT electrode 51, a wiring portion 52, and a reflector 53. The IDT electrode 51 is, for example, a first IDT electrode 51a. The acoustic wave device 1 has a plurality of IDT electrodes 51. The wiring portion 52 electrically connects the first IDT electrode 51a to the other IDT electrodes 51.

[0016] (IDT electrode) FIG. 2 shows the shape of the first IDT electrode 51a in a plan view. As shown in FIG. 2, the first IDT electrode 51a is composed of two opposing comb-tooth electrodes 511. The comb-tooth electrode 511 is, for example, a first comb-tooth electrode 511a. The comb-tooth electrode 511 is, for example, a second comb-tooth electrode 511b. The first comb-tooth electrode 511a and the second comb-tooth electrode 511b have portions that face each other. The first comb-tooth electrode 511a and the second comb-tooth electrode 511b are configured to be connected to different potentials. The comb-tooth electrode 511 has a bus bar 5111 and a plurality of electrode fingers 5112. The bus bar 5111 is, for example, a first bus bar 5111a. The bus bar 5111 is, for example, a second bus bar 5111b. The electrode fingers 5112 are, for example, first electrode fingers 5112a connected to the first bus bar 5111a. The electrode finger 5112 is, for example, a second electrode finger 5112b connected to a second bus bar 5111b.

[0017] 2, the repetition interval between each of the electrode fingers 5112 is called pitch p. By adjusting the pitch p, it is possible to control the wavelength of the acoustic wave excited by the electrode fingers 5112 and resonating with a signal.

[0018] The pitch p of the multiple electrode fingers 5112 is basically constant within the IDT electrode 51. Note that the IDT electrode 51 may have a portion where the pitch p is unique. Examples of the unique portion include a portion where the pitch p is narrower or wider than the majority (e.g., 80% or more), and a thinned-out portion where a small number of the electrode fingers 5112 are essentially thinned out.

[0019] In the following, unless otherwise specified, pitch p refers to the pitch of the portion excluding the above-mentioned unique portion (the majority of electrode fingers 5112). In addition, in the case where pitch p varies in most of electrode fingers 5112 excluding the unique portion, the average value of the pitches of most of electrode fingers 5112 may be used as the value of pitch p.

[0020] The lengths of the electrode fingers 5112 are, for example, equal to each other. The IDT electrode 51 may be apodized, in which the lengths of the electrode fingers 5112 vary depending on the position in the propagation direction. The thickness of the electrode fingers 5112 may be appropriately set depending on the required electrical characteristics, etc.

[0021] In acoustic wave device 1, the width of electrode fingers 5112 is represented by w. Duty d of IDT electrode 51 represents the ratio of the electrode fingers to pitch p. That is, duty d of IDT electrode 51 can be represented by w / p. When duty d is calculated, w and p are expressed in the same unit, for example, μm. Regarding electrode finger width w, if a unique portion exists, the portion excluding the unique portion (the majority of multiple electrode fingers 5112) may be used as electrode finger width w. Furthermore, if the electrode finger width w varies in most of electrode fingers 5112 excluding the unique portion, the average value of electrode finger widths w of most of multiple electrode fingers 5112 may be used as the value of electrode finger width w.

[0022] 3, the IDT electrode 51 may have dummy electrode fingers 513 protruding from a bus bar 5111. The IDT electrode 51 may have a variable width between the first comb-tooth electrode 511a and the second comb-tooth electrode 511b, or may be inclined with respect to the propagation direction of the acoustic wave.

[0023] The number of electrode fingers 5112 may be set as appropriate depending on the electrical characteristics required of the acoustic wave device 1. A small number of electrode fingers 5112 are shown as schematic diagrams in Fig. 2, Fig. 3, and the subsequent plan views. In reality, more electrode fingers 5112 than shown in the drawings may be arranged.

[0024] The IDT electrode 51 is made of a conductive material. The IDT electrode 51 may be made of various conductive materials such as Al (aluminum), Cu (copper), Pt (platinum), Mo (molybdenum), Au (gold) or alloys thereof, and may be made of a plurality of layers stacked together. Although not shown, when the IDT electrode 51 is made of a laminate of a plurality of layers, a base layer may be interposed at the interface between the layers. For example, the IDT electrode 51 may be made of Al, and the base layer may be made of Ti.

[0025] (Wiring section) The wiring portion 52 electrically connects the first IDT electrode 51a to the other IDT electrodes. The wiring portion 52 is, for example, a first wiring portion 52a connected to a first bus bar 5111a. The wiring portion 52 is, for example, a second wiring portion 52b connected to a second bus bar 5111b. The first bus bar 5111a is connected to the other IDT electrodes by the first wiring portion 52a, and the second bus bar 5111b is connected to the other IDT electrodes by the second wiring portion 52b.

[0026] The wiring section 52 is made of a material having electrical conductivity. For example, various conductive materials such as Al, Cu, Pt, Mo, Au, or alloys thereof can be used as the material of the wiring section 52, and the wiring section 52 may be made of a laminate of a plurality of layers. Although not shown, when the wiring section 52 is made of a laminate of a plurality of layers, a base layer may be interposed at the interface of the layers. For example, the wiring section 52 may be made of Al, and the base layer may be made of Ti.

[0027] (reflector) The electrode layer 5 has a reflector 53. The reflector 53 is, for example, a first reflector 53a. The reflector 53 is, for example, a second reflector 53b. The reflector 53 reduces leakage of the acoustic wave propagating in the D1 direction. The electrode layer 5 may not have the reflector 53 depending on the design. The first metal part 331a described later and the reflector 53 may not overlap in a planar view. Note that the first metal part 331a described later and the reflector 53 not overlapping may include the case where the reflector 53 is not included. When the reflector 53 is included, as shown in FIG. 4, the first reflector 53a and the second reflector 53b are arranged to face each other at positions sandwiching the IDT electrode 51 in a planar view. Reflector 53 has a pair of bus bars facing each other in the arrangement direction of electrode fingers 5112 (direction D1), and a plurality of strip electrodes extending between these bus bars in the extension direction of electrode fingers 5112 (direction D2).

[0028] The multiple strip electrodes of reflector 53 are arranged in direction D1 following the arrangement of the multiple electrode fingers 5112. The number and width of the strip electrodes may be set appropriately depending on the electrical characteristics required of acoustic wave device 1. The pitch of the multiple strip electrodes is, for example, equivalent to the pitch p of the multiple electrode fingers 5112. In addition, the distance between the strip electrode at the end of reflector 53 and the electrode finger 5112 at the end of IDT electrode 51 is, for example, equivalent to the pitch p of the multiple electrode fingers 5112.

[0029] (Piezoelectric material) The piezoelectric body 4 is formed to be relatively thin compared to a general surface acoustic wave device. The thickness of the piezoelectric body 4 may be appropriately set to be 2p or less compared with the pitch p of the IDT electrodes 51. This makes it possible to utilize elastic waves, such as bulk waves and plate waves, in the thickness direction excited in the piezoelectric body 4.

[0030] The material of the piezoelectric body 4 is a single crystal of lithium tantalate (LiTaO3, hereinafter sometimes abbreviated as "LT") or a single crystal of lithium niobate (LiNbO3, hereinafter sometimes abbreviated as "LN"). The piezoelectric body 4 is not limited to these, and various piezoelectric materials may be used.

[0031] (Multilayer film) As shown in Fig. 1, the multilayer film 3 is located between the support substrate 2 and the piezoelectric body 4. The multilayer film 3 is an acoustic reflection film formed by alternately stacking low acoustic impedance layers 31 including a portion having a lower acoustic impedance than the layer in contact with it above, and high acoustic impedance layers 32 including a portion having a higher acoustic impedance than the layer in contact with it above. The multilayer film 3 includes multiple low acoustic impedance layers 31 and multiple high acoustic impedance layers 32. The multilayer film 3 reflects waves propagating from above in the stacking direction at the interface between the low acoustic impedance layers 31 and the high acoustic impedance layers 32.

[0032] The number of layers in the multilayer film 3 may be set appropriately. For example, the total number of layers of the low acoustic impedance layers 31 and the high acoustic impedance layers 32 in the multilayer film 3 may be 4 or more and 12 or less. In this embodiment, the multilayer film 3 has at least two low acoustic impedance layers 31 and at least one high acoustic impedance layer 32. In other words, the multilayer film 3 is composed of a total of three or more layers. The total number of layers in the multilayer film 3 may be an even number or an odd number. The layer in contact with the piezoelectric body 4 and the support substrate 2 may be the low acoustic impedance layer 31 or the high acoustic impedance layer 32.

[0033] The material of the low acoustic impedance layer 31 is, for example, silicon dioxide (SiO2). The material of the high acoustic impedance layer 32 is, for example, any one of hafnium oxide (HfO2), tantalum oxide (Ta2O5), and zirconium oxide (ZrO2). The material of the multilayer film 3 is not limited to these, and various materials may be used as long as the material satisfies the magnitude relationship of acoustic impedance with the layer in contact above.

[0034] As shown in FIG. 1, any one layer of the high acoustic impedance layer 32 of the multilayer film 3 includes a first metal portion 331a and an insulator portion 332. The first metal portion 331a is made of a material having a higher acoustic impedance than the layer in contact therewith above. The material of the first metal portion 331a is, for example, W (tungsten). The first metal portion 331a may be made of another metal material having a relatively high acoustic impedance or an alloy thereof. The first metal portion 331a may be, for example, Ti (titanium). In particular, when the first metal portion 331a is made of a material having a high acoustic impedance such as W, the reflectivity of the wave propagating in the stacking direction of the multilayer film 3 is improved. In other words, the number of layers of the multilayer film 3 can be reduced, which contributes to the miniaturization of the acoustic wave device 1. The insulator portion 332 is, for example, hafnium oxide (HfO2). The insulator portion 332 may be made of another insulator material having a relatively high acoustic impedance. The insulator portion 332 may be, for example, tantalum oxide (Ta2O5) or zirconium oxide (ZrO2). The acoustic impedance of the insulator portion 332 may be higher, equal, or lower than that of the layer in contact therewith above. The insulator portion 332 may be, for example, silicon oxide (SiO2) having a relatively low acoustic impedance, or may be the same material as the low acoustic impedance layer 31.

[0035] 5, the first metal portion 331a may be configured to overlap the IDT electrode 51 in a plan view. The IDT electrode 51 and the first metal portion 331a form a capacitor, and This increases the capacitance of the acoustic wave device 1. In other words, the impedance of the acoustic wave device 1 decreases, and Δf, which is the difference between the resonant frequency and the anti-resonant frequency, decreases.

[0036] As shown in FIG. 6, the first metal portion 331a may overlap the first comb tooth electrode 511a and the second comb tooth electrode 511b in a plan view. When the first metal portion 331a overlaps the first comb tooth electrode 511a and the second comb tooth electrode 511b in a plan view, a capacitor is formed between the first metal portion 331a and the first comb tooth electrode 511a and between the first metal portion 331a and the second comb tooth electrode 511b. The capacitor formed between the first comb tooth electrode 511a and the first metal portion 331a and the capacitor formed between the second comb tooth electrode 511b and the first metal portion 331a are connected in series. That is, a capacitor connected in parallel is formed between the first comb tooth electrode 511a and the second comb tooth electrode 511b. The capacitance of the elastic wave device 1 increases and the impedance decreases, so that Δf, which is the difference between the resonant frequency and the anti-resonant frequency, can be reduced. The first metal portion 331a is formed by a process such as photolithography, for example. Another metal portion formed at the same time as the first metal portion 331a may be formed by photolithography so as to overlap another IDT electrode 51. The first metal portion 331a may be configured so as to overlap the first IDT electrode 51a in a plan view, but may not overlap the other IDT electrodes 51. The layer having the first metal portion 331a is configured so as to be separated and insulated from the first metal portion 331a and the other metal portions by filling the portion other than the first metal portion 331a with an insulator portion 332. In other words, as shown in FIG. 7, the second IDT electrode 51b is further included, and a second metal portion 331b overlapping the second IDT electrode 51b in a plan view is further included, and the first metal portion 331a and the second metal portion 331b are insulated by the insulator portion 332. By overlapping a single metal portion 331 and a single IDT electrode 51, a capacitor is formed which is connected in parallel from the nodes before and after the IDT electrode 51.

[0037] The thickness of each layer of the multilayer film 3 may be set appropriately, and may be uniform or may differ from one another.

[0038] (Bulk Wave) An acoustic wave device according to an embodiment of the present disclosure excites, for example, bulk waves. Since the bulk waves have a small propagating component in the D1 direction and a large propagating component in the D3 direction, the multilayer film 3 contributes to reducing leakage of the propagating acoustic waves.

[0039] Generally speaking, the bulk wave includes three types of waves: longitudinal waves, slow transverse waves, and fast transverse waves. The slow transverse waves and fast transverse waves are either SV (Shear vertical) waves or SH (Shear horizontal) waves, respectively. The bulk wave for which the acoustic impedance is calculated may be, for example, a bulk wave that propagates through the piezoelectric body 4 and corresponds to a component that is mainly included among the above three types of bulk waves. For example, when the elastic wave in the piezoelectric body 4 includes an SH wave, the acoustic impedance layer related to the SH wave of the piezoelectric body 4 and the acoustic impedance related to the SH wave of the low acoustic impedance layer 31 may be compared. Although the SH wave is taken as an example, the SV wave or longitudinal wave may also be compared by the above method. In addition, when it is intended to use an elastic wave in which a longitudinal wave and a transverse wave are combined, for example, the acoustic impedance of the transverse wave may be compared.

[0040] The conditions for comparison do not necessarily need to be as strict as those described above. From another perspective, when comparing acoustic impedances between layers, the acoustic impedances of both do not need to be strictly specified. For example, consider a comparison of acoustic impedances related to shear waves between two layers. When the difference between the acoustic impedances of fast and slow shear waves in each layer is relatively small, and the magnitude relationship of the acoustic impedances between the two layers is clear even if the fast and slow shear waves are not particularly distinguished, there is no need to distinguish between the fast and slow shear waves. From another perspective, the components mainly contained in the elastic waves of the piezoelectric body 4 intended for use do not need to be strictly specified.

[0041] Second Embodiment A second embodiment of an acoustic wave device according to the present disclosure will be described. The configurations of an acoustic wave device 1, a support substrate 2, a piezoelectric body 4, and an electrode layer 5 are the same as those of the first embodiment. A description of the common parts will be omitted. Only the differences will be described below.

[0042] 8, any one of the low acoustic impedance layers 31 of the multilayer film 3 includes a first metal portion 331a and an insulator portion 332. The first metal portion 331a is made of a material having a lower acoustic impedance than the layer in contact therewith above. The material of the first metal portion 331a is, for example, Al (aluminum). The first metal portion 331a may be made of another metal material having a relatively low acoustic impedance or an alloy thereof.

[0043] The insulator portion 332 is, for example, silicon oxide (SiO2). Other insulator materials having a relatively low acoustic impedance may be used for the insulator portion 332. The acoustic impedance of the insulator portion 332 may be higher, equal, or lower than that of the layer in contact therewith above. The insulator portion 332 may be, for example, tantalum oxide (Ta2O5) or zirconium oxide (ZrO2) having a relatively high acoustic impedance, or may be the same material as the high acoustic impedance layer 32.

[0044] Third embodiment An acoustic wave device according to a third embodiment of the present disclosure will be described. The configurations of an acoustic wave device 1, a support substrate 2, a multilayer film 3, and a piezoelectric body 4 are the same as those of the first embodiment. Only the differences will be described below.

[0045] (electrode layer) As shown in FIG. 9, the first comb-tooth electrode 511a may be connected to the first reflector 53a, and the second comb-tooth electrode 511b may be connected to the second reflector 53b. In this embodiment, the first metal portion 331a may overlap the first reflector 53a and the second reflector 53b in a plan view. In this embodiment, the first metal portion 331a forms a capacitor with the first reflector 53a and the second reflector 53b. The capacitor formed between the first metal portion 331a and the first reflector 53a and the capacitor formed between the first metal portion 331a and the second reflector 53b are connected in series. That is, a capacitor connected in parallel is formed between the first reflector 53a and the second reflector 53b. By increasing the capacitance of the elastic wave device 1 and decreasing the impedance, it is possible to reduce Δf, which is the difference between the resonant frequency and the anti-resonant frequency.

[0046] Alternatively, the first metal portion 331a may overlap the first reflector 53a and the second comb-tooth electrode 511b in a plan view. In this embodiment, the first metal portion 331a forms a capacitor with the first reflector 53a and the second comb-tooth electrode 511b. The capacitor formed between the first metal portion 331a and the first reflector 53a and the capacitor formed between the first metal portion 331a and the second comb-tooth electrode 511b are connected in series. In other words, a capacitor connected in parallel is formed between the first reflector 53a and the second comb-tooth electrode 511b. By increasing the capacitance of the elastic wave device 1 and decreasing the impedance, it is possible to reduce Δf, which is the difference between the resonant frequency and the anti-resonant frequency.

[0047] Alternatively, only the first comb-tooth electrode 511a and the first reflector 53a may be connected, and the second comb-tooth electrode 551b and the second reflector 53b may not be connected. In this embodiment, the first metal portion 331a forms a capacitor with the first reflector 53a and the second comb-tooth electrode 511b. The capacitor formed between the first metal portion 331a and the first reflector 53a and the capacitor formed between the first metal portion 331a and the second comb-tooth electrode 511b are connected in series. In other words, a capacitor connected in parallel is formed between the first reflector 53a and the second comb-tooth electrode 511b. As a result of the increase in capacitance and the decrease in impedance of elastic wave device 1, the difference Δf between the resonant frequency and the anti-resonant frequency can be reduced.

[0048] [Fourth embodiment] An acoustic wave device according to a fourth embodiment of the present disclosure will be described. The configurations of an acoustic wave device 1, a support substrate 2, a multilayer film 3, and a piezoelectric body 4 are the same as those of the first embodiment. Only the differences will be described below.

[0049] (electrode layer) 10, first bus bar 5111a and second bus bar 5111b may be thicker in plan view. Specifically, they may be thicker than the thickness of any one of multiple electrode fingers 5112. First bus bar 5111a may be thicker in plan view. In this embodiment, the overlapping area between IDT electrode 51 and first metal portion 331a can be increased in plan view, and thus the capacitance of elastic wave device 1 is large. The increase in capacitance and the decrease in impedance of elastic wave device 1 can reduce Δf, which is the difference between the resonant frequency and the antiresonant frequency. Furthermore, the increase in IDT electrode 51 improves the heat dissipation of elastic wave device 1.

[0050] Fifth embodiment An acoustic wave device according to a fifth embodiment of the present disclosure will be described. The configurations of an acoustic wave device 1, a support substrate 2, a multilayer film 3, and a piezoelectric body 4 are the same as those of the first embodiment. Only the differences will be described below.

[0051] (electrode layer) As shown in FIGS. 11A and 11B, the first bus bar 5111a and the second bus bar 5111b may have the first portion 5121 and the second portion 5122. Only the first bus bar 5111a may have the first portion 5121 and the second portion 5122. The first portion 5121 is connected to the first wiring portion 52a and the first electrode finger 5112a. The second portion 5122 is connected to the first portion 5121 and configured to overlap the first metal portion 331a in a plan view. At this time, the first metal portion 331a may be configured to overlap the second comb-tooth electrode 511b. The second portion 5122 may be rectangular as shown in FIG. 11A, circular as shown in FIG. 11B, or any other shape.

[0052] Adding second portion 5122 to first bus bar 5111a and second bus bar 5111b increases the area where first metal portion 331a and IDT electrode 51 overlap in a plan view. The capacitance of elastic wave device 1 increases and the impedance decreases, thereby reducing Δf, which is the difference between the resonant frequency and the anti-resonant frequency. Furthermore, increasing the size of IDT electrode 51 improves heat dissipation.

[0053] Sixth embodiment A sixth embodiment of an acoustic wave device according to the present disclosure will be described. The configurations of an acoustic wave device 1, a support substrate 2, a multilayer film 3, a piezoelectric body 4, and an electrode layer 5 are the same as those of the first embodiment. Only the differences will be described below.

[0054] FIG. 12 is a cross-sectional view of the elastic wave device 1 of FIG. 2 taken along line XX. For ease of explanation, FIG. 12 illustrates the height of first comb-tooth electrode 511a to be higher than the height of second comb-tooth electrode 511b, but in actual design, they may be higher, equal, or lower. As shown in FIG. 12, the elastic wave device 1 may have a through portion 8 connecting first comb-tooth electrode 511a and first metal portion 331a. Through portion 8 is made of a conductor. In this embodiment, first metal portion 331a and second comb-tooth electrode 511b may overlap in a plan view. In this embodiment, In this embodiment, a capacitor is formed between second comb-tooth electrode 511b and first metal portion 331a, and the capacitance of elastic wave device 1 is increased and the impedance is reduced, thereby making it possible to reduce Δf, which is the difference between the resonant frequency and the anti-resonant frequency. In addition, through portion 8 contributes to dissipating heat generated when elastic waves are excited.

[0055] Seventh embodiment A seventh embodiment of an acoustic wave device according to the present disclosure will be described. The configurations of an acoustic wave device 1, a support substrate 2, a multilayer film 3, a piezoelectric body 4, and an electrode layer 5 are the same as those of the first embodiment. Only the differences will be described below.

[0056] (Multilayer film) The larger the area of ​​the first metal portion 331a, the greater the contribution to heat dissipation. Specifically, the area of ​​the first metal portion 331a may be larger than or equal to the total area of ​​the first IDT electrode 51 on the piezoelectric body 4 as shown in FIG. 1. The total area is the area of ​​the region where the first comb-tooth electrode 511a and the second comb-tooth electrode 511b face each other. The total area also includes the region where the comb-tooth electrode 511 does not overlap the piezoelectric body 4 in a plan view.

[0057] Eighth embodiment An eighth embodiment of an acoustic wave device according to the present disclosure will be described. The acoustic wave device 1, the support substrate 2, the multilayer film 3, the piezoelectric body 4, and the electrode layer 5 have the same configurations as those of the first embodiment. Only the differences will be described below.

[0058] FIG. 13 is a cross-sectional view of the elastic wave device 1 cut in the D2 direction. As shown in FIG. 13, the first metal portion 331a may overlap the connection portion 9 that is located above the piezoelectric body and connects to the outside in a plan view. The connection portion 9 is, for example, a bump such as solder. The connection portion 9 includes a conductor and can dissipate heat from the elastic wave device 1 through the first metal portion 331a. That is, the heat dissipation performance of the elastic wave device 1 is improved. The first metal portion 331a may be continuously formed on a line segment between an arbitrary point directly below the IDT electrode 51 and an arbitrary point directly below the connection portion 9. According to the present embodiment, the first metal portion 331a serves as a linear heat dissipation path, and the heat dissipation performance of the elastic wave device 1 is improved. The metal portion directly below the connection portion 9 may be a metal portion different from the first metal portion 331a directly below the IDT electrode 51.

[0059] Ninth embodiment A ninth embodiment of an acoustic wave device according to the present disclosure will be described. The configurations of an acoustic wave device 1, a supporting substrate 2, a piezoelectric body 4, and an electrode layer 5 are the same as those of the first embodiment. Only the differences will be described below.

[0060] 14, in a plan view, the first metal portion 331a may overlap the first wiring portion 52a connected to the first bus bar 5111a and the second wiring portion 52b connected to the second bus bar 5111b. In this case, the first wiring portion 52a and the second wiring portion 52b are connected to different potentials, and the first metal portion 331a forms a capacitor with the first wiring portion 52a and the second wiring portion 52b. The capacitor formed between the first metal portion 331a and the first wiring portion 52a and the capacitor formed between the first metal portion 331a and the second wiring portion 52b are connected in series to form a capacitor. In other words, a capacitor connected in parallel is formed between the first wiring portion 52a and the second wiring portion 52b. The impedance of the elastic wave device 1 is reduced, and Δf, which is the difference between the resonant frequency and the anti-resonant frequency, can be reduced.

[0061] The first metal portion 331a may overlap the first wiring portion 52a and the second comb-tooth electrode 511b. In this case, the first wiring portion 52a and the second comb-tooth electrode 511b are connected to different potentials, and the first metal portion 331a is connected to the first wiring portion 52a and the second comb-tooth electrode 511b. A capacitor is formed. A capacitor formed between first metal portion 331a and first wiring portion 52a and a capacitor formed between first metal portion 331a and second comb-tooth electrode 511b are connected in series to form a capacitor. In other words, a capacitor connected in parallel is formed between first wiring portion 52a and second comb-tooth electrode 511b. The impedance of elastic wave device 1 is reduced, and Δf, which is the difference between the resonant frequency and the anti-resonant frequency, can be reduced.

[0062] Tenth embodiment A tenth embodiment of an elastic wave device according to the present disclosure will be described. The configurations of an elastic wave device 1, a supporting substrate 2, a piezoelectric body 4, and an electrode layer 5 are the same as those of the first embodiment. Only the differences will be described below.

[0063] The layer having first metal portion 331a forms a larger capacitor as it is closer to piezoelectric body 4. Specifically, in the cross-sectional view, it may be disposed above the center of multilayer film 3. In other words, as shown in FIG. 1, the number of layers of multilayer film 3 may be the first layer or the second layer when viewed from above.

[0064] Eleventh embodiment An eleventh embodiment of an acoustic wave device according to the present disclosure will be described. The configurations of an acoustic wave device 1, a supporting substrate 2, a piezoelectric body 4, and an electrode layer 5 are the same as those of the first embodiment. Only the differences will be described below.

[0065] 15, the high acoustic impedance layer 32 having the first metal portion 331a may be located below the center of the multilayer film 3. The material with high acoustic impedance is, for example, W. Above the center of the multilayer film 3, the material and thickness of the low acoustic impedance layer 31 and the high acoustic impedance layer 32 may be controlled to selectively enhance the reflection of an acoustic wave of a desired wavelength. According to the eleventh embodiment of the acoustic wave device 1 according to the present disclosure, the resonance of unwanted waves can be reduced. By increasing the distance from the IDT electrode 51, it is possible to adjust the electric flux in the D3 direction, which reduces the excitation of an acoustic wave, for example, a plate wave.

[0066] [Twelfth embodiment] An eleventh embodiment of an acoustic wave device according to the present disclosure will be described. The configurations of an acoustic wave device 1, a supporting substrate 2, a piezoelectric body 4, and an electrode layer 5 are the same as those of the first embodiment. Only the differences will be described below.

[0067] 16, the elastic wave device 1 may have a plurality of layers each having first metal portion 331a. That is, the elastic wave device 1 may have first metal portion 331a in, for example, two layers. Waves propagating in the stacking direction are more efficiently reflected by the plurality of first metal portions 331a. In addition, the heat dissipation properties are improved by first metal portion 331a.

[0068] Examples of applications of the elastic wave device according to the present disclosure will be described below. In the following examples of applications, the first to twelfth embodiments and combinations thereof may be used.

[0069] [First use example: splitter] 17 is a circuit diagram illustrating the configuration of a duplexer 101 as an example of the use of the acoustic wave device 1.

[0070] The splitter 101 has, for example, a transmit filter 105 that filters a transmit signal from a transmit terminal 103 and outputs the signal to an antenna terminal 102, and a receive filter 106 that filters a receive signal from the antenna terminal 102 and outputs the signal to a pair of receive terminals 104.

[0071] Transmit filter 105 is configured, for example, by a ladder filter including multiple elastic wave devices 1. That is, transmit filter 105 has multiple (or one) elastic wave devices 1 connected in series between transmit terminal 103 and antenna terminal 102, and multiple (or one) elastic wave devices 1 (parallel arms) connecting the series line (series arm) to a reference potential.

[0072] The receiving filter 106 includes, for example, an acoustic wave device 1 and a multimode filter (including a double-mode filter) 107. The multimode filter 107 has a plurality of IDT electrodes 51 (three in the illustrated example) arranged in the propagation direction of the acoustic waves and a pair of reflectors 53 arranged on both sides thereof.

[0073] Although the description has been given of a case in which splitter 101 includes transmit filter 105 and receive filter 106, the present invention is not limited to this. Splitter 101 may be, for example, a diplexer or a multiplexer including three or more filters.

[0074] Elastic wave devices 1 having first metal portion 331a may be used only in elastic wave devices 1 that generate a large amount of heat in duplexer 101. For example, by using elastic wave devices 1 having first metal portion 331a only in elastic wave devices 1 that are closer to antenna terminal 102, heat generation in duplexer 101 can be reduced.

[0075] Furthermore, a capacitive element does not need to be connected to acoustic wave device 1 included in branching filter 101. For example, a capacitor does not need to be connected in parallel to acoustic wave device 1.

[0076] [Second use example: communication device] 18 is a block diagram showing a main part of a communication device 111 as an example of using the duplexer 101. The communication device 111 performs wireless communication using radio waves, and includes the duplexer 101.

[0077] In the communication device 111, a transmission information signal TIS including information to be transmitted is modulated and frequency-raised (converted to a high-frequency signal of a carrier frequency) by an RF-IC (Radio Frequency Integrated Circuit) 113 to become a transmission signal TS. Unnecessary components outside the transmission passband are removed from the transmission signal TS by a bandpass filter 115a, amplified by an amplifier 114a, and input to a splitter 101 (transmission terminal 103). The splitter 101 (transmission filter 105) then removes unnecessary components outside the transmission passband from the input transmission signal TS, and outputs the transmission signal TS after removal to an antenna terminal 102 or an antenna 112. The antenna 112 converts the input electrical signal (transmission signal TS) into a wireless signal (radio wave) and transmits it.

[0078] In addition, in the communication device 111, a radio signal (radio wave) received by an antenna 112 is converted by the antenna 112 into an electric signal (received signal RS) and input to the duplexer 101 (antenna terminal 102). The duplexer 101 (receiving filter 106) removes unnecessary components outside the receiving passband from the inputted received signal RS, and the signal is amplified by the amplifier 114b from the receiving terminal 104, and the unnecessary components outside the receiving passband are removed by the bandpass filter 115b. The received signal RS is then frequency-downshifted and demodulated by the RF-IC 113 to become a received information signal RIS.

[0079] The transmission information signal TIS and the reception information signal RIS may be low-frequency signals (baseband signals) containing appropriate information, such as analog voice signals or digitized voice signals. The passband of radio signals (for example, 5 GHz or higher) may also be used. The modulation method may be phase modulation, amplitude modulation, frequency modulation, or a combination of any two or more of these. Although the direct conversion type is illustrated in Fig. 18, other suitable circuit types may be used, for example, a double superheterodyne type. Fig. 18 shows only the essential parts in a schematic manner, and a low-pass filter or an isolator may be added at an appropriate position, and the positions of the amplifiers and the like may be changed.

[0080] 〔summary〕 (1) An elastic wave device according to a first aspect of the present disclosure comprises a piezoelectric body, a first IDT electrode located above the piezoelectric body, and a multilayer film located below the piezoelectric body, the first IDT electrode having portions facing each other and including a first comb-tooth electrode and a second comb-tooth electrode configured to be connected to different potentials, the first comb-tooth electrode being formed by a first bus bar and a plurality of first electrode fingers, the second comb-tooth electrode being formed by a second bus bar and a plurality of second electrode fingers, the multilayer film having at least one low acoustic impedance layer including a portion having a lower acoustic impedance than a layer in contact with the upper side, and at least one high acoustic impedance layer including a portion having a higher acoustic impedance than a layer in contact with the upper side, and at least one of the low acoustic impedance layer or the high acoustic impedance layer includes a first metal portion and an insulator portion.

[0081] (2) An elastic wave device according to a second aspect of the present disclosure is the same as the first aspect, except that the first metal portion overlaps with the first IDT electrode in a plan view.

[0082] (3) An elastic wave device according to a third aspect of the present disclosure is the same as or similar to the first or second aspect, wherein the first metal portion overlaps both the first comb-tooth electrode and the second comb-tooth electrode in a planar view.

[0083] (4) In an elastic wave device according to a fourth aspect of the present disclosure, in the first to third aspects described above, the first metal portion does not overlap with any IDT electrodes other than the first IDT electrode in a plan view.

[0084] (5) An elastic wave device according to a fifth aspect of the present disclosure is, in the first to fourth aspects described above, further includes a second IDT electrode and a second metal portion overlapping the second IDT electrode in a planar view, and the first metal portion and the second metal portion are insulated from each other by the insulator portion.

[0085] (6) An elastic wave device according to a sixth aspect of the present disclosure is any one of the first to fifth aspects, wherein, in a planar view, the first metal portion overlaps the first bus bar, and, in a planar view, the thickness of the first bus bar is thicker than the thickness of any one of the first electrode fingers.

[0086] (7) A seventh aspect of the present disclosure provides an elastic wave device in any one of the first to sixth aspects, wherein the first busbar has a first wiring portion electrically connecting the first IDT electrode to another IDT electrode, a first portion connecting the first electrode fingers, and a second portion overlapping the first metal portion in a planar view.

[0087] (8) An elastic wave device according to an eighth aspect of the present disclosure is, in any one of the first to seventh aspects described above, a wiring portion that electrically connects the first IDT electrode to another IDT electrode, and in a planar view, the first metal portion overlaps the wiring portion.

[0088] (9) A ninth aspect of the present disclosure is an elastic wave device in any one of the first to eighth aspects, wherein the elastic wave device has a first wiring portion connected to the first bus bar and a second wiring portion connected to the second bus bar, and in a planar view, the first metal portion overlaps both the first wiring portion and the second wiring portion.

[0089] (10) An elastic wave device according to a tenth aspect of the present disclosure is any one of the first to ninth aspects, wherein the first metal portion and the reflector do not overlap in a plan view.

[0090] (11) An elastic wave device according to an eleventh aspect of the present disclosure is, in any one of the first to tenth aspects above, further comprising a first reflector on the piezoelectric body connected to the first comb electrode, and in a planar view, the first metal portion overlaps the first reflector.

[0091] (12) An elastic wave device according to a twelfth aspect of the present disclosure is any one of the first to eleventh aspects, in which the first metal portion and the insulating portion are located above a center of the multilayer film.

[0092] (13) An elastic wave device according to a thirteenth aspect of the present disclosure, in any one of the first to twelfth aspects above, has a through portion connecting the first comb tooth electrode and the first metal portion, the through portion having a conductor, and at least a portion of the first metal portion overlaps with the second comb tooth electrode in a planar view.

[0093] (14) An elastic wave device according to a fourteenth aspect of the present disclosure, in any one of the first to thirteenth aspects above, further has a connection portion located above the piezoelectric body and connected to the outside, and at least a portion of the first metal portion overlaps with the connection portion in a planar view.

[0094] (15) An elastic wave device according to a fifteenth aspect of the present disclosure is, in any one of the first to fourteenth aspects described above, such that, in a planar view, the total area of ​​the first metal portion is greater than or equal to the total area of ​​the first IDT electrode.

[0095] (16) According to a sixteenth aspect of the present disclosure, in the elastic wave device of any one of the first to fifteenth aspects, the thickness of the piezoelectric body is equal to or less than 2p, where p is the pitch of the first IDT electrode.

[0096] (17) An acoustic wave device according to a seventeenth aspect of the present disclosure is any one of the first to sixteenth aspects, wherein the first IDT electrode is configured to excite a bulk wave.

[0097] (18) An acoustic wave device according to an eighteenth aspect of the present disclosure is any one of the first to seventeenth aspects, wherein the first IDT electrode is configured to excite a plate wave.

[0098] (19) A duplexer according to a nineteenth aspect of the present disclosure has an antenna terminal, a transmit filter that filters a signal output to the antenna terminal, and a receive filter that filters a signal input from the antenna terminal, wherein either the transmit filter or the receive filter includes an elastic wave device described in any of the first to eighteenth aspects.

[0099] (20) The acoustic wave device according to a twentieth aspect of the present disclosure included in the duplexer according to the nineteenth aspect does not include a capacitive element.

[0100] (21) A communication device according to a twenty-first aspect of the present disclosure includes a duplexer as described in the nineteenth or twentieth aspect, in which the antenna terminal is connected to the antenna, and an IC connected to a terminal opposite the antenna terminal with respect to the signal path for the transmit filter and the receive filter.

[0101] 1: Elastic wave device 2: Support substrate 3:Multilayer film 31: Low acoustic impedance layer 32: High acoustic impedance layer 331: Metal part 331a: 1st metal part 331b:Second metal part 332: Insulation section 4: Piezoelectric 5: Electrode layer 51:IDT electrode 51a: 1st IDT electrode 51b: 2nd IDT electrode 511:Comb electrode 511a: 1st comb electrode 511b: Second comb electrode 5111: Busbar 5111a: First bus bar 5111b: 2nd bus bar 5112: Electrode finger 5112a: 1st electrode finger 5112b: 2nd electrode finger 5113: Dummy electrode 52: Wiring section 52a: 1st wiring section 52b: 2nd wiring section 53:Reflector 53a: First wiring section 53b: 2nd wiring section 8: Penetration 9: Connection 101: Duplexer 102: Antenna terminal 103: Transmission terminal 104: Receiving terminal 105: Transmission filter 106: Receive filter 107: Multimode filter 111: Communication equipment 112: Antenna 113: RF-IC 114: Amplifier 115: Bandpass filter

Claims

1. A piezoelectric body; a first IDT electrode located above the piezoelectric body; a multilayer film located below the piezoelectric body; having The first IDT electrode is a first comb-tooth electrode and a second comb-tooth electrode having portions facing each other and configured to be connected to different potentials; the first comb electrode is constituted by a first bus bar and a plurality of first electrode fingers, the second comb electrode is constituted by a second bus bar and a plurality of second electrode fingers, The multilayer film is at least one low acoustic impedance layer having a portion with a lower acoustic impedance than a layer adjacent thereto above; at least one high acoustic impedance layer having a portion with a higher acoustic impedance than a layer adjacent thereto above; having At least one of the low acoustic impedance layer and the high acoustic impedance layer includes a first metal portion and an insulator portion. Elastic wave device.

2. The first metal portion overlaps with the first IDT electrode in a plan view. The acoustic wave device according to claim 1 .

3. The first metal portion overlaps both the first comb-tooth electrode and the second comb-tooth electrode in a plan view. The acoustic wave device according to claim 2 .

4. The first metal portion does not overlap with any other IDT electrodes other than the first IDT electrode in a plan view. The acoustic wave device according to claim 2 .

5. Further comprising a second IDT electrode, a second metal portion overlapping the second IDT electrode in a plan view; The first metal portion and the second metal portion are insulated from each other by the insulator portion. The acoustic wave device according to claim 4 .

6. the first metal portion overlaps the first bus bar in a plan view, In a plan view, the thickness of the first bus bar is larger than the thickness of any one of the first electrode fingers. The acoustic wave device according to claim 1 .

7. The first bus bar is a first wiring portion electrically connecting the first IDT electrode to another IDT electrode, and a first portion connecting the first electrode finger to the first wiring portion; a second portion overlapping the first metal portion in a plan view; have The acoustic wave device according to claim 1 .

8. a wiring portion electrically connecting the first IDT electrode and another IDT electrode; The first metal portion overlaps with the wiring portion in a plan view. The acoustic wave device according to claim 1 .

9. The acoustic wave device includes: A first wiring portion connected to the first bus bar; a second wiring portion connected to the second bus bar, The first metal portion overlaps both the first wiring portion and the second wiring portion in a plan view. The acoustic wave device according to claim 7 .

10. The first metal portion and the reflector do not overlap in a plan view.

2. The acoustic wave device according to claim 1.

11. a first reflector connected to the first comb electrode on the piezoelectric body; In a plan view, the first metal portion overlaps with the first reflector. The acoustic wave device according to claim 1 .

12. The first metal portion and the insulator portion are located above the center of the multilayer film. The acoustic wave device according to claim 1 .

13. a through portion that connects the first comb-tooth electrode and the first metal portion; The through portion has a conductor, At least a portion of the first metal portion overlaps with the second comb-tooth electrode in a plan view. The acoustic wave device according to claim 1 .

14. A connection portion is located above the piezoelectric body and connected to an outside. At least a portion of the first metal portion, In plan view, it overlaps with the connection portion. The acoustic wave device according to claim 1 .

15. In a plan view, a total area of ​​the first metal portion is larger than or equal to a total area of ​​the first IDT electrode. The acoustic wave device according to claim 1 .

16. When the pitch of the first IDT electrode is p, the thickness of the piezoelectric body is 2p or less. The acoustic wave device according to claim 1 .

17. The first IDT electrode is configured to excite a bulk wave. The acoustic wave device according to claim 1 .

18. The first IDT electrode is configured to excite a plate wave. The acoustic wave device according to claim 1 .

19. An antenna terminal; a transmission filter that filters a signal output to the antenna terminal; a receiving filter that filters a signal input from the antenna terminal; having A duplexer, wherein either the transmission filter or the reception filter includes the acoustic wave device according to claim 1 .

20. The acoustic wave device does not include a capacitive element. The duplexer according to claim 19.

21. The antenna, The duplexer according to claim 19 or 20, wherein the antenna terminal is connected to the antenna; an IC connected to a terminal opposite to the antenna terminal with respect to a signal path with respect to the transmission filter and the reception filter; A communication device having the above configuration.

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