Acoustic wave device and multiplexer

Abstract

To provide an acoustic wave device having a piston mode IDT electrode in which the generation of unnecessary waves due to third harmonic excitation is suppressed.SOLUTION: A filter 10 includes an acoustic wave resonator having a piezoelectric substrate 50 and an IDT electrode 30. The piezoelectric substrate 50 includes a piezoelectric layer 51, a low acoustic velocity layer 52, and a high acoustic velocity layer 53. The crossing region of the IDT electrode 30 has a center region and an edge region. The IDT electrode 30 includes a mass addition film disposed in the edge region. A duty D of the IDT electrode 30 and a cut angle θ° of the piezoelectric layer 51 satisfy any of 0.513≤D≤0.568 and 2.5≤θ≤17.5, 0.538≤D≤0.568 and 17.5≤θ≤22.5, 0.538≤D≤0.588 and 42.5≤θ≤52.5, 0.538≤D≤0.613 and 52.5≤θ≤67.5, 0.513≤D≤0.638 and 67.5≤θ≤77.5, and 0.513≤D≤0.713 and 77.5≤θ≤92.5.SELECTED DRAWING: Figure 3A

Description

[Technical field]

[0001] The present invention relates to an acoustic wave device and a multiplexer. [Background technology]

[0002] Patent Documents 1 and 2 disclose an electrode structure and a laminated structure of a substrate of a surface acoustic wave resonator using a substrate including a piezoelectric layer, a low acoustic velocity layer, and a high acoustic velocity layer. Patent Document 1 discloses a piston mode structure in which the width of multiple electrode fingers constituting an IDT (InterDigital Transducer) electrode is partially widened, and Patent Document 2 discloses a piston mode structure in which a mass-adding film is disposed on the tips of multiple electrode fingers constituting an IDT electrode. It is said that the piston mode structures disclosed in Patent Documents 1 and 2 can suppress ripples in the transverse mode. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 060150 [Patent Document 2] JP 2019-092095 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the elastic wave resonators having piston-mode IDT electrodes disclosed in Patent Documents 1 and 2, the suppression of unnecessary waves (triple harmonic excitation) occurring at a frequency three times that of the fundamental wave is insufficient.

[0005] Therefore, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an acoustic wave device and a multiplexer having a piston mode IDT electrode in which the generation of unwanted waves of third harmonic excitation is suppressed. [Means for solving the problem]

[0006] In order to achieve the above object, an acoustic wave device according to one aspect of the present invention includes a first acoustic wave resonator having a substrate and an IDT electrode disposed on the substrate, the substrate including a piezoelectric layer having an IDT electrode formed thereon, the substrate including a piezoelectric layer made of lithium tantalate, a high acoustic velocity layer having a bulk wave acoustic velocity faster than an acoustic wave acoustic velocity in the piezoelectric layer, and a low acoustic velocity layer disposed between the piezoelectric layer and the high acoustic velocity layer and having a bulk wave acoustic velocity slower than a bulk wave acoustic velocity in the piezoelectric layer, the IDT electrode including a plurality of first electrode fingers and a plurality of second electrode fingers arranged in parallel to each other, a first bus bar electrode configured to connect one ends of the plurality of first electrode fingers together, and a low acoustic velocity layer configured to connect one ends of the plurality of second electrode fingers together, the IDT electrode including a plurality of first electrode fingers and a plurality of second electrode fingers arranged in parallel to each other, and a second bus bar electrode arranged to face the first bus bar electrode with the plurality of second electrode fingers interposed therebetween, wherein when a region where the plurality of first electrode fingers and the plurality of second electrode fingers overlap when viewed from a first direction parallel to the piezoelectric layer and perpendicular to the extension direction of the first electrode fingers and the second electrode fingers is defined as an intersection region, the intersection region has a central region located at the center in the extension direction and edge regions located on both outer sides of the central region in the extension direction and where the sound speed is slower than the sound speed in the central region, and the IDT electrode further has a mass addition film arranged in a second direction perpendicular to the main surface of the piezoelectric layer of at least one of the plurality of first electrode fingers and the plurality of second electrode fingers in the edge regions, and wherein a duty of the IDT electrode is D and a cut angle of the piezoelectric layer is θ°, (1) 0.513≦D≦0.568 and 2.5≦θ≦17.5, (2) 0.538≦D≦0.568 and 17.5≦θ≦22.5, (3) 0.538≦D≦0.588, and 42.5≦θ≦52.5, (4) 0.538≦D≦0.613, and 52.5≦θ≦67.5, (5) 0.513≦D≦0.638, and 67.5≦θ≦77.5, and (6) Either 0.513≦D≦0.713 or 77.5≦θ≦92.5 is satisfied. Effect of the Invention

[0007] According to the present invention, it is possible to provide an acoustic wave device and a multiplexer having a piston mode IDT electrode in which the generation of unwanted waves of third harmonic excitation is suppressed. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a circuit configuration diagram of a multiplexer according to an embodiment. [Figure 2A] 1 is a circuit configuration diagram of an elastic wave device according to an embodiment. [Figure 2B] 1 is a circuit configuration diagram of an elastic wave device in accordance with a first modified example of an embodiment. FIG. [Figure 3A] 1 is a plan view of a first acoustic wave resonator according to an embodiment. [Figure 3B] 1 is a first cross-sectional view of a first acoustic wave resonator in accordance with an embodiment. [Figure 3C] 4 is a second cross-sectional view of the first acoustic wave resonator in accordance with the embodiment. FIG. [Figure 4A] 11 is a plan view of a first acoustic wave resonator in accordance with a second modification of the embodiment. FIG. [Figure 4B] 11 is a cross-sectional view of a first acoustic wave resonator in accordance with a second modification of the embodiment. FIG. [Figure 5A] 13 is a graph showing the resonance characteristics of an elastic wave resonator when the duty of an IDT electrode is changed. [Figure 5B] 11 is a graph showing the phase of a third harmonic excitation signal of an acoustic wave resonator when the duty of an IDT electrode is changed. [Figure 5C] 11 is a graph showing the relationship between the duty of the IDT electrode and the phase of a third harmonic excitation signal. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, arrangements and connection forms of the components shown in the following embodiments are merely examples and are not intended to limit the present invention.

[0010] In addition, each figure is a schematic diagram in which emphasis, omission, or adjustment of the ratio is appropriately performed in order to illustrate the present invention, and is not necessarily a strict illustration, and may differ from the actual shape, positional relationship, and ratio. In each figure, the same reference numerals are given to substantially the same configurations, and duplicated explanations may be omitted or simplified.

[0011] In the circuit configuration of the present disclosure, “connected between A and B” or “connected between A and B” means connected to both A and B between A and B.

[0012] In addition, in the component arrangement of the present disclosure, “component A is arranged in series on path B” means that both the signal input terminal and the signal output terminal of component A are connected to the wiring, electrode, or terminal that constitutes path B.

[0013] In addition, terms indicating the relationship between elements, such as "parallel" and "perpendicular," terms indicating the shape of an element, such as "rectangle," and numerical ranges do not only indicate the strict meaning, but also include a substantially equivalent range, for example, an error of about a few percent.

[0014] Also, in this disclosure, a "terminal" means a point where a conductor within an element terminates, and is to be construed as any point on a conductor between elements or the entire conductor, not just a single point, if the impedance of the conductor between elements is sufficiently low.

[0015] In the following embodiments, the passband of an acoustic wave device or filter is defined as a frequency band between two frequencies that are 3 dB higher than the minimum value of insertion loss in the passband.

[0016] In addition, in the present disclosure, band A and band B refer to frequency bands defined in advance by standardization organizations (e.g., 3GPP (registered trademark), IEEE (Institute of Electrical and Electronics Engineers), etc.) for communication systems built using radio access technology (RAT). In this embodiment, the communication system may be, for example, a Long Term Evolution (LTE) system, a 5th Generation (5G)-New Radio (NR) system, and a Wireless Local Area Network (WLAN) system, but is not limited thereto.

[0017] Additionally, the uplink operating band of Band A refers to the frequency range of Band A designated for uplink use, and the downlink operating band of Band A refers to the frequency range of Band A designated for downlink use.

[0018] (Embodiment) [1. Circuit configuration of multiplexer] 1 is a circuit diagram of a multiplexer 1 according to an embodiment of the present invention. The multiplexer 1 includes filters 10 and 20, a common terminal 100, and input / output terminals 110 and 120.

[0019] The common terminal 100 is connected to, for example, an antenna 2 .

[0020] Filter 10 is an example of an acoustic wave device and includes a first acoustic wave resonator. Filter 10 is connected to common terminal 100 and has a pass band including, for example, an uplink operating band of band A. Filter 20 is connected to common terminal 100 and has a pass band including, for example, a downlink operating band of band A. Filters 10 and 20 form, for example, a duplexer for band A.

[0021] Note that filter 10 may have a passband including at least one of an uplink operating band and a downlink operating band of band A, and filter 20 may have a passband including at least one of an uplink operating band and a downlink operating band of band B different from band A. In this case, filters 10 and 20 form a diplexer.

[0022] In the present embodiment, the passband of filter 10 is located on the lower frequency side than the passband of filter 20. At least one of the multiple acoustic wave resonators constituting filter 10 can reduce unwanted waves of third harmonic excitation. Therefore, even if unwanted waves of third harmonic excitation generated by filter 10 are included in the vicinity of the passband of filter 20, degradation of the pass characteristics of filter 20 can be suppressed.

[0023] The passband of the filter 10 may be located on the higher frequency side than the passband of the filter 20 .

[0024] 2A is a circuit diagram of a filter 10 according to an embodiment. As shown in the figure, the filter 10 includes series arm resonators 11, 12, 13, and 14, parallel arm resonators 15, 16, 17, and 18, and terminals 111 and 112.

[0025] The terminal 111 is an example of a first input / output terminal, and is connected to the common terminal 100. The terminal 112 is an example of a second input / output terminal, and is connected to the input / output terminal 110.

[0026] Each of the series arm resonators 11 to 14 is an acoustic wave resonator, and is arranged in series on a path connecting the terminal 111 and the terminal 112. The series arm resonator 11 is an example of a first acoustic wave resonator, and is connected closest to the common terminal 100 among the series arm resonators 11 to 14 and the parallel arm resonators 15 to 18.

[0027] The parallel arm resonator 15 is an elastic wave resonator and is connected between the connection point of the series arm resonators 11 and 12 and ground. The parallel arm resonator 16 is an elastic wave resonator and is connected between the connection point of the series arm resonators 12 and 13 and ground. The parallel arm resonator 17 is an elastic wave resonator and is connected between the connection point of the series arm resonators 13 and 14 and ground. The parallel arm resonator 18 is an elastic wave resonator and is connected between the connection point of the series arm resonator 14 and the terminal 112 and ground.

[0028] With the above configuration, the filter 10 constitutes, for example, a ladder-type bandpass filter. Each of the series arm resonators 11 to 14 and the parallel arm resonators 15 to 18 has an IDT electrode disposed on a piezoelectric substrate.

[0029] 2A is just one example, and the numbers of series arm resonators and parallel arm resonators are not limited to four, but may each be equal to or greater than 1. In addition, an inductor may be connected between the parallel arm resonator and ground.

[0030] Furthermore, filter 10 is not limited to being a ladder-type bandpass filter, and may be, for example, a filter including a longitudinally coupled resonator in which a plurality of acoustic wave resonators are arranged in parallel in the acoustic wave propagation direction, as shown in FIG. 2B.

[0031] 2B is a circuit diagram of a filter 10A according to a first modification of the embodiment. Filter 10A is an example of an acoustic wave device and is connected to a common terminal 100. As shown in FIG. 2B, filter 10A is a filter circuit including a longitudinally coupled resonator 19 including seven acoustic wave resonators, and includes longitudinally coupled resonator 19, series arm resonators 11, 12, and 13, parallel arm resonators 15 and 16, and terminals 111 and 112. Terminal 111 is connected to common terminal 100, and terminal 112 is connected to input / output terminal 120.

[0032] The longitudinally coupled resonator 19 is composed of acoustic wave resonators 191 , 192 , 193 , 194 , 195 , 196 and 197 , and has one end connected to a terminal 111 via series arm resonators 11 and 12 , and the other end connected to a terminal 112 via a series arm resonator 13 .

[0033] Each of the acoustic wave resonators 191 to 197 has an IDT electrode disposed on a piezoelectric substrate. The IDT electrodes of the acoustic wave resonators 191 to 197 are composed of two comb electrodes facing each other. One comb electrode of each of the acoustic wave resonators 191, 193, 195, and 197 is connected to a terminal 111 via the series arm resonators 11 and 12, and the other comb electrode of each of the acoustic wave resonators 191, 193, 195, and 197 is connected to a ground. One comb electrode of each of the acoustic wave resonators 192, 194, and 196 is connected to a terminal 112 via the series arm resonator 13, and the other comb electrode of each of the acoustic wave resonators 192, 194, and 196 is connected to a ground. The acoustic wave resonators 191 to 197 are arranged in the order of 191, 192, 193, 194, 195, 196, and 197 along the acoustic wave propagation direction.

[0034] The series arm resonators 11, 12, and 13 are arranged in series on a path connecting terminals 111 and 112. The parallel arm resonators 15 and 16 are each connected between the above path and ground. The series arm resonator 11 is an example of a first acoustic wave resonator, and is connected closest to the common terminal 100 among the series arm resonators 11 to 13, the longitudinally coupled resonator 19, and the parallel arm resonators 15 and 16.

[0035] The filter 20 may be any one of a band-pass filter, a notch filter, a low-pass filter, and a high-pass filter, and includes at least one of an acoustic wave resonator, an inductor, and a capacitor.

[0036] When filter 20 includes an acoustic wave resonator, filters 10 and 20 may be formed on the same piezoelectric substrate. This allows multiplexer 1 to be miniaturized and the manufacturing process to be simplified. Furthermore, when filter 20 includes an acoustic wave resonator, the film thickness of the IDT electrode of the acoustic wave resonator may be the same as the film thickness of the IDT electrode of the acoustic wave resonator constituting filter 10. This allows the manufacturing process of multiplexer 1 to be simplified.

[0037] [2. Structure of the first acoustic wave resonator] Next, the structure of a first acoustic wave resonator constituting the filter 10 will be described. Fig. 3A is a plan view of the series arm resonator 11 according to an embodiment. Fig. 3B is a first cross-sectional view of the series arm resonator 11 according to the embodiment. Fig. 3C is a second cross-sectional view of the series arm resonator 11 according to the embodiment. The series arm resonator 11 shown in Figs. 3A to 3C is an example of a first acoustic wave resonator. Fig. 3B shows a cross-sectional view taken along line IIIB-IIIB in Fig. 3A, and Fig. 3C shows a cross-sectional view taken along line IIIC-IIIC in Fig. 3A.

[0038] 3A to 3C, the series arm resonator 11 includes a piezoelectric substrate 50, an IDT electrode 30, and a reflective electrode 40. Note that the series arm resonator 11 shown in Fig. 3A to 3C is intended to illustrate a typical structure of a first acoustic wave resonator constituting the filter 10, and the number and length of electrode fingers constituting the IDT electrode 30 are not limited thereto. The IDT electrode 30 and the reflective electrode 40 are disposed on the piezoelectric substrate 50 (in the positive direction of the z-axis).

[0039] As shown in FIGS. 3B and 3C, the piezoelectric substrate 50 has piezoelectric properties and includes a piezoelectric layer 51, a low acoustic velocity layer 52, a high acoustic velocity layer 53, and a support substrate .

[0040] The IDT electrode 30 and the reflective electrode 40 are disposed on one surface of the piezoelectric layer 51. For example, lithium tantalate (LiTaO3) or a material containing lithium tantalate as a main component can be used for the piezoelectric layer 51. The thickness of the piezoelectric layer 51 is, for example, 900 nm.

[0041] The high acoustic velocity layer 53 is disposed on the other side of the piezoelectric layer 51, and the acoustic velocity of the bulk wave propagating through the high acoustic velocity layer 53 is faster than the acoustic velocity of the elastic wave propagating through the piezoelectric layer 51. For example, the high acoustic velocity layer 53 can be made of a piezoelectric material such as silicon nitride, aluminum nitride, lithium tantalate, lithium niobate, or quartz, a ceramic material such as alumina, sapphire, magnesia, silicon carbide, zirconia, cordierite, mullite, steatite, or forsterite, a dielectric material such as diamond or glass, a semiconductor material such as silicon or gallium nitride, or a resin, or a material containing the above materials as a main component. The thickness of the high acoustic velocity layer 53 is, for example, 300 nm.

[0042] The low acoustic velocity layer 52 is disposed between the other main surface of the piezoelectric layer 51 and one main surface of the high acoustic velocity layer 53, and the acoustic velocity of the bulk wave propagating through the low acoustic velocity layer 52 is lower than that of the bulk wave propagating through the piezoelectric layer 51. This structure and the property of the elastic wave concentrating energy in a medium with an essentially low acoustic velocity suppress leakage of the surface acoustic wave energy out of the piezoelectric layer 51. The low acoustic velocity layer 52 can be made of, for example, a dielectric material such as silicon oxide, glass, silicon oxynitride, lithium oxide, tantalum oxide, or a compound in which fluorine, carbon, or boron is added to silicon oxide, or a material mainly composed of the above materials. The film thickness of the low acoustic velocity layer 52 is, for example, 300 nm.

[0043] The support substrate 54 is disposed on the other main surface of the high acoustic velocity layer 53, and is a substrate that supports the IDT electrode 30, the piezoelectric layer 51, the low acoustic velocity layer 52, and the high acoustic velocity layer 53. For example, the support substrate 54 can be made of a piezoelectric material such as silicon, aluminum nitride, lithium tantalate, lithium niobate, or quartz, a ceramic material such as alumina, sapphire, magnesia, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, or forsterite, a dielectric material such as diamond or glass, a semiconductor material such as gallium nitride, or a resin, or a material mainly composed of the above materials. The thickness of the support substrate 54 is, for example, 125 μm.

[0044] The above-described laminated structure of piezoelectric substrate 50 makes it possible to significantly increase the Q value at the resonant frequency and the anti-resonant frequency, compared to a conventional structure using a single-layer piezoelectric substrate. In other words, an elastic wave resonator with a high Q value can be configured, and therefore, using this elastic wave resonator, it is possible to configure a high-frequency filter with low insertion loss.

[0045] It is also possible that the low acoustic velocity layer 52 is not provided, and the piezoelectric layer 51 is provided directly on the high acoustic velocity layer 53 .

[0046] The high acoustic velocity layer 53 and the support substrate 54 may be combined to form one high acoustic velocity support substrate. The high acoustic velocity support substrate is a substrate that supports the IDT electrode 30, the piezoelectric layer 51, and the low acoustic velocity layer 52. The high acoustic velocity support substrate is a substrate in which the acoustic velocity of the bulk waves in the high acoustic velocity support substrate is faster than that of the surface waves and boundary waves propagating through the piezoelectric layer 51, and functions to confine the surface acoustic waves in the portion where the piezoelectric layer 51 and the low acoustic velocity layer 52 are laminated, and to prevent the surface acoustic waves from leaking below the high acoustic velocity support substrate. Examples of materials that can be used for the high acoustic velocity support substrate include piezoelectric materials such as aluminum nitride, lithium tantalate, lithium niobate, and quartz, ceramics such as alumina, sapphire, magnesia, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, forsterite, spinel, and sialon, dielectric materials such as aluminum oxide, silicon oxynitride, DLC (diamond-like carbon), and diamond, semiconductors such as silicon, and materials mainly composed of the above materials. The spinel includes an aluminum compound containing oxygen and one or more elements selected from Mg, Fe, Zn, Mn, etc. Examples of the spinel include MgAl2O4, FeAl2O4, ZnAl2O4, and MnAl2O4.

[0047] In this specification, the term "major component of a material" refers to a component that accounts for more than 50% by weight of the material. The major component may be in any of the following states: single crystal, polycrystalline, or amorphous, or a mixture of these.

[0048] Also, instead of the piezoelectric substrate 50, a support substrate, an energy trapping layer, and a piezoelectric layer may be laminated in this order. The IDT electrode 30 and the reflective electrode 40 are formed on the piezoelectric layer. For example, LiTaO3 piezoelectric single crystal or piezoelectric ceramics is used for the piezoelectric layer. The support substrate is a substrate that supports the piezoelectric layer, the energy trapping layer, and the IDT electrode 30.

[0049] The energy trapping layer is composed of one or more layers, and the speed of the bulk acoustic wave propagating through at least one of the layers is greater than the speed of the acoustic wave propagating near the piezoelectric layer. For example, the energy trapping layer may have a laminated structure of a low acoustic velocity layer and a high acoustic velocity layer. The low acoustic velocity layer is a film in which the acoustic velocity of the bulk wave in the low acoustic velocity layer is slower than the acoustic velocity of the acoustic wave propagating through the piezoelectric layer. The high acoustic velocity layer is a film in which the acoustic velocity of the bulk wave in the high acoustic velocity layer is faster than the acoustic velocity of the acoustic wave propagating through the piezoelectric layer. The support substrate may be the high acoustic velocity layer.

[0050] The energy trapping layer may be an acoustic impedance layer having a configuration in which low acoustic impedance layers having a relatively low acoustic impedance and high acoustic impedance layers having a relatively high acoustic impedance are alternately laminated.

[0051] As shown in FIG. 3A, the IDT electrode 30 has a plurality of electrode fingers 31a and a plurality of electrode fingers 31b, bus bar electrodes 32a and 32b, and mass addition films 35a and 35b.

[0052] Each of the electrode fingers 31a and the electrode fingers 31b extends in a direction perpendicular to the acoustic wave propagation direction (x-axis direction: first direction), and the electrode fingers 31a and the electrode fingers 31b are arranged parallel to each other. The electrode fingers 31a are an example of first electrode fingers, and the electrode fingers 31b are an example of second electrode fingers.

[0053] The busbar electrode 32a is an example of a first busbar electrode and is configured to connect one ends of the electrode fingers 31a to each other. The busbar electrode 32a extends in a direction (x-axis direction) intersecting with the extension direction (y-axis direction) of the electrode fingers 31a. The busbar electrode 32b is an example of a second busbar electrode and is configured to connect one ends of the electrode fingers 31b to each other. The busbar electrode 32b extends in a direction (x-axis direction: first direction) intersecting with the extension direction (y-axis direction) of the electrode fingers 31b. The busbar electrodes 32a and 32b are arranged opposite each other with the electrode fingers 31a and the electrode fingers 31b interposed therebetween. The other ends of the electrode fingers 31a face the busbar electrode 32b, and the other ends of the electrode fingers 31b face the busbar electrode 32a. The busbar electrodes 32a and 32b may extend in a direction intersecting the extension direction (y-axis direction) but not perpendicular to the extension direction (y-axis direction).

[0054] The reflective electrodes 40 are arranged on both sides of the IDT electrode 30 so as to be adjacent to the IDT electrode 30 in a direction (x-axis direction) perpendicular to the extending direction of the electrode fingers 31a and the electrode fingers 31b. The reflective electrodes 40 are configured to confine within the IDT electrode 30 a predetermined high-frequency signal that resonates in the IDT electrode 30. The reflective electrode 40 has a plurality of electrode fingers and a pair of busbar electrodes. The electrode fingers of the reflective electrode 40 are arranged parallel to the electrode fingers 31a and 31b. One of the busbar electrodes of the reflective electrode 40 is configured to connect one ends of the electrode fingers of the reflective electrode 40 to each other, and the other of the busbar electrodes of the reflective electrode 40 is configured to connect the other ends of the electrode fingers of the reflective electrode 40 to each other. Note that the series arm resonator 11 according to this embodiment does not necessarily require the reflective electrode 40.

[0055] The electrode fingers 31a and 31b, the bus bar electrodes 32a and 32b, and the reflective electrode 40 have a laminated structure of, for example, an adhesive layer 311 and a main electrode layer 310, as shown in FIGS. 3B and 3C.

[0056] The main electrode layer 310 is mainly composed of aluminum (Al), and has a thickness of, for example, 320 nm. The adhesion layer 311 is disposed between the main electrode layer 310 and the piezoelectric layer 51, and is configured to improve adhesion of the main electrode layer 310 to the piezoelectric layer 51. The adhesion layer 311 is made of titanium (Ti), and has a thickness of, for example, 30 nm. Note that the electrode fingers 31a and 31b, the busbar electrodes 32a and 32b, and the reflective electrode 40 are not limited to the above-mentioned laminated structure, and may be made of, for example, a metal or alloy such as Ti, Al, Cu, Pt, Au, Ag, or Pd, or may be made of a laminate of multiple layers made of the above-mentioned metals or alloys.

[0057] 3B and 3C, a protective layer 34 is disposed so as to cover the electrode fingers 31a and 31b and the bus bar electrodes 32a and 32b. The protective layer 34 is a layer intended to protect the main electrode layer 310 from the external environment, adjust the frequency-temperature characteristics, and increase the moisture resistance, and is, for example, a dielectric film containing silicon oxide as a main component. The protective layer 34 does not necessarily have to be disposed.

[0058] 3A, the main surface of the piezoelectric substrate 50 is divided into a plurality of regions. A region where the plurality of electrode fingers 31a and the plurality of electrode fingers 31b overlap when viewed from a first direction (x-axis direction) that is parallel to the main surface of the piezoelectric layer 51 and perpendicular to the extension direction of the electrode fingers 31a and 31b is defined as an intersection region W. The intersection region W has a central region C and an edge region E. The central region C is located at the center in the extension direction (y-axis direction). The edge regions E are located on both outer sides of the central region C in the extension direction (y-axis direction), and are regions where the sound speed is slower than that in the central region C.

[0059] The mass adding films 35a and 35b are arranged along the x-axis direction and in a second direction (z-axis direction) perpendicular to the main surface of the piezoelectric layer 51 in the region between the electrode fingers 31a and 31b and the multiple electrode fingers 31a and 31b in the edge region E. By arranging the mass adding films 35a and 35b, the edge region E has a lower sound speed than the central region C.

[0060] From the above, the central region C is defined as the region sandwiched between the mass adding films 35a and 35b of the IDT electrode 30, where the mass adding films 35a and 35b are not arranged, and the length of the central region C in the extension direction (y-axis direction) is arbitrary. Also, the edge regions E are defined as the regions located on both outer sides of the central region C in the extension direction (y-axis direction), where the mass adding films 35a or 35b are arranged.

[0061] In order to make the sound velocity in the edge region E lower than that in the central region C, the edge region E is provided with a mass-adding film 35a or 35b in addition to the structure in the central region C.

[0062] Mass-adding films 35a and 35b for making the edge region E a region with a slower sound velocity than that in the central region C include, for example, a dielectric film whose main component is any of tantalum oxide (Ta2O5), titanium oxide (TiO2), hafnium oxide (HfO2), niobium oxide (Nb2O5), tungsten oxide (WO3), cerium oxide (CeO2), and silicon oxide (SiO2), or a metal film.

[0063] The mass-adding films 35a and 35b do not have to be disposed in the region between the electrode fingers 31a and 31b in the edge region E. Furthermore, the mass-adding film 35a may be disposed only on the electrode fingers 31b in the edge region E, and the mass-adding film 35b may be disposed only on the electrode fingers 31a in the edge region E.

[0064] Here, the electrode parameters of the IDT electrodes that constitute the acoustic wave resonator will be described.

[0065] The wavelength of the acoustic wave resonator is defined as the wavelength λ, which is the repetition period of the electrode fingers 31a or 31b shown in FIG. 3A and FIG. 3B. In other words, the wavelength λ is twice the electrode finger pitch, which is the distance between the center of the electrode finger 31a and the center of the electrode finger 31b adjacent to each other. The electrode finger pitch is defined as (L+S), where L is the line width of the electrode fingers 31a and 31b, and S is the space width between the electrode fingers 31a and 31b adjacent to each other. The duty D of the IDT electrode 30 is the line width occupancy rate of the electrode fingers 31a and 31b, which is the ratio of the line width to the sum of the line width and the space width of the electrode fingers 31a and 31b, and is defined as L / (L+S). In FIG. 3B, the height of the electrode fingers 31a and 31b is h.

[0066] In the IDT electrode 30, when the interval between adjacent electrode fingers is not constant, the electrode finger pitch of the IDT electrode 30 is defined as the average electrode finger pitch of the IDT electrode 30. The average electrode finger pitch of the IDT electrode 30 is defined as Di / (Ni-1), where the total number of electrode fingers 31a and 31b included in the IDT electrode 30 is Ni, and Di is the center-to-center distance between the electrode finger located at one end and the electrode finger located at the other end of the IDT electrode 30 in the acoustic wave propagation direction (x-axis direction).

[0067] Furthermore, when the duties of electrode fingers 31a and 31b are not uniform, duty D of IDT electrode 30 is defined as the average of the duties of multiple electrode fingers 31a and multiple electrode fingers 31b.

[0068] The IDT electrode 30 of the series arm resonator 11 according to this embodiment has a so-called 3D piston mode structure in which a mass-adding film is arranged in the second direction of the electrode fingers, and is capable of suppressing ripples in the transverse mode.

[0069] Moreover, the IDT electrode 30 of the series arm resonator 11 according to this embodiment is suitable for increasing the duty of the IDT electrode 30 with high precision, as compared with an IDT electrode having a so-called 2D piston structure in which the width of a portion of the electrode fingers is widened in the first direction.

[0070] [3. Structure of First Acoustic Wave Resonator According to Modification Example 2] Next, a structure of a first acoustic wave resonator constituting the filter 10 according to Modification 2 will be described. Fig. 4A is a plan view of a series arm resonator 11A according to Modification 2 of the embodiment. Fig. 4B is a cross-sectional view of the series arm resonator 11A according to Modification 2 of the embodiment. Fig. 4B shows a cross-sectional view taken along line IVB-IVB in Fig. 4A.

[0071] A filter 10 according to the second modification has a circuit configuration in which the series arm resonator 11 in the circuit shown in Fig. 2A is replaced with a series arm resonator 11A. The series arm resonator 11A shown in Fig. 4A and Fig. 4B is an example of a first acoustic wave resonator.

[0072] 4A and 4B, the series arm resonator 11A includes a piezoelectric substrate 50, an IDT electrode 30A, and a reflective electrode 40A. Note that the series arm resonator 11A shown in Fig. 4A and 4B is intended to illustrate a typical structure of a first acoustic wave resonator constituting the filter 10 according to Modification 2, and the number and length of electrode fingers constituting the IDT electrode 30A are not limited thereto. The IDT electrode 30A and the reflective electrode 40A are disposed on the piezoelectric substrate 50 (in the positive direction of the z-axis).

[0073] The series arm resonator 11A according to this modification differs from the series arm resonator 11 according to the embodiment only in the configurations of the mass addition films 36a and 36b. In the following, the series arm resonator 11A according to this modification will be described focusing on the different configurations and omitting the description of the same configurations as those of the series arm resonator 11 according to the embodiment.

[0074] As shown in FIG. 4A, the IDT electrode 30A has a plurality of electrode fingers 31a and a plurality of electrode fingers 31b, bus bar electrodes 32a and 32b, and mass addition films 36a and 36b.

[0075] The mass adding films 36a and 36b are each disposed in a second direction (z-axis direction) perpendicular to the main surface of the piezoelectric layer 51 at the tip portions of the multiple electrode fingers 31a and 31b in the edge region E. The mass adding films 36a and 36b are not disposed in the region between the electrode fingers 31a and 31b in the edge region E.

[0076] The mass-adding films 36a and 36b are disposed so that the sound velocity in the edge region E is lower than that in the central region C.

[0077] The mass-adding films 36a and 36b are made of, for example, the same conductive material as the plurality of electrode fingers 31a and the plurality of electrode fingers 31b.

[0078] The mass-adding film 36a may be further disposed on the electrode fingers 31a in the edge region E, and the mass-adding film 36b may be further disposed on the electrode fingers 31b in the edge region E.

[0079] The IDT electrode 30A of the series arm resonator 11A according to this modification has a so-called 3D piston mode structure in which a mass-adding film is arranged in the second direction of the electrode fingers, and is capable of suppressing ripples in the transverse mode.

[0080] Furthermore, the IDT electrode 30A of the series arm resonator 11A according to this modified example is suitable for increasing the duty of the IDT electrode 30A with high precision, compared to an IDT electrode having a so-called 2D piston structure in which the width of a portion of the electrode fingers is widened in the first direction.

[0081] [4. Relationship between the cut angle of the piezoelectric layer and the duty of the IDT electrode] Next, the cut angle θ of the piezoelectric layer and the duty D of the IDT electrode for suppressing the third harmonic excitation response of the first acoustic wave resonator having a 3D piston mode structure will be described. The piezoelectric layer 51 (LiTaO3) is a θ°Y-cut X-propagation LiTaO3 piezoelectric single crystal or piezoelectric ceramic (a lithium tantalate single crystal or ceramic cut on a plane having an axis rotated θ° from the Y-axis as the central axis, and in which surface acoustic waves propagate in the X-axis direction). The cut angle θ shown below is the θ of the above θ°Y-cut X-propagation LiTaO3.

[0082] Table 1 shows an example of parameters of an elastic wave resonator having a 3D piston mode structure.

[0083] [Table 1]

[0084] Fig. 5A is a graph showing the resonance characteristics of an elastic wave resonator when the duty of an IDT electrode is changed, Fig. 5B is a graph showing the phase of a third harmonic excitation signal of the elastic wave resonator when the duty of the IDT electrode is changed, and Fig. 5C is a graph showing the relationship between the duty of the IDT electrode and the phase of the third harmonic excitation signal.

[0085] The elastic wave resonator from which the characteristics of FIGS. 5A to 5C are obtained has the parameters shown in Table 1, and has the 3D piston mode structure shown in FIGS. 3A to 3C.

[0086] As shown in Figures 5A and 5B, when the duty D is changed to 0.525, 0.6, and 0.65 at the commonly used cut angle θ of the piezoelectric layer of 30°, the resonance characteristics of the fundamental wave hardly change, but the strength (impedance difference between the resonant frequency and the anti-resonant frequency) and phase of the third harmonic excitation increase as the duty increases. Note that the larger the phase of the third harmonic excitation signal (closer to +90°), the higher the strength of the third harmonic excitation signal, and the smaller the phase of the third harmonic excitation signal (closer to -90°), the lower the strength of the third harmonic excitation signal.

[0087] 5C, when the cut angle θ of the piezoelectric layer is 30°, the phase of the third harmonic excitation signal exceeds −45° when the duty D is 0.5 or more. In other words, when the cut angle θ is 30°, the unwanted wave of the third harmonic excitation becomes larger as the duty D increases.

[0088] However, increasing the duty D of the IDT electrode is an effective method for increasing the capacitance of the acoustic wave resonator without increasing the size of the IDT electrode. In addition, by increasing the duty D, the line width of the electrode fingers can be made large, thereby suppressing manufacturing variations in the IDT electrode.

[0089] From the above viewpoint, the inventors have found a combination of the duty D and the cut angle θ that can suppress the spurious waves of the third harmonic excitation in a region where the duty D of the IDT electrode is greater than 0.5.

[0090] Tables 2, 3, and 4 show the phases of the third harmonic excitation signal when the duty D and the cut angle θ are changed. Specifically, Table 2 shows the phases of the third harmonic excitation when the duty D is 0.5 or more and the cut angle θ is 0° to 32.5°, Table 3 shows the phases of the third harmonic excitation when the duty D is 0.5 or more and the cut angle θ is 32.5° to 67.5°, and Table 4 shows the phases of the third harmonic excitation when the duty D is 0.5 or more and the cut angle θ is 67.5° to 92.5°.

[0091] The numerical value α of the cut angle shown in Tables 2 to 4 means that it has a range of α±2.5°, and the numerical value β of the duty D means that it has a range of β-0.012 to β+0.013.

[0092] [Table 2]

[0093] [Table 3]

[0094] [Table 4]

[0095] In Tables 2 to 4, in the region where the duty D is greater than 0.5, the range in which the phase of the third harmonic excitation becomes smaller than that of the conventionally used (D, θ)=(0.5, 30) is as follows: (1) 0.513≦D≦0.568 and 2.5≦θ≦17.5, (2) 0.538≦D≦0.568 and 17.5≦θ≦22.5, (3) 0.538≦D≦0.588, and 42.5≦θ≦52.5, (4) 0.538≦D≦0.613, and 52.5≦θ≦67.5, (5) 0.513≦D≦0.638, and 67.5≦θ≦77.5, and (6) 0.513≦D≦0.713 and 77.5≦θ≦92.5 (within the thick, double, and triple line frames in Tables 2 to 4).

[0096] That is, the series arm resonator 11 (first acoustic wave resonator) included in the filter 10 according to the present preferred embodiment satisfies any one of the above conditions (1) to (6).

[0097] This makes it possible to provide a filter 10 having a piston mode IDT electrode in which the generation of unwanted waves due to third harmonic excitation is suppressed in a region where the duty D is large, which is advantageous for miniaturization and suppression of manufacturing variations.

[0098] Furthermore, by applying the first acoustic wave resonator satisfying any one of the above (1) to (6) to the series arm resonator 11 connected closest to the common terminal 100 in the filter 10, it is possible to effectively reduce the reflection loss at the frequency of the third harmonic excitation when the filter 10 is viewed from the common terminal 100. As a result, it is possible to suppress deterioration of the pass characteristic at the above frequency of the third harmonic excitation of the filter 20 connected to the common terminal 100.

[0099] The first acoustic wave resonator satisfying any one of the above conditions (1) to (6) does not have to be applied to the series arm resonator 11, and may be applied to at least one of the series arm resonators 12 to 14 and the parallel arm resonators 15 to 18 of the filter 10. Even in this case, it is possible to provide the filter 10 having a piston mode IDT electrode in which the generation of unwanted waves due to third harmonic excitation is suppressed in a region where the duty D is large, which is advantageous for miniaturization and suppression of manufacturing variations.

[0100] Moreover, the series arm resonator 11 (first acoustic wave resonator) of the filter 10 according to the present embodiment has (7) 0.538≦D≦0.588, and 42.5≦θ≦52.5, and (8) It is desirable to satisfy either 0.538≦D≦0.613 and 52.5≦θ≦57.5 (within the double-lined and triple-lined frames in Table 3).

[0101] In a region where the cut angle θ is 30° or less, the crystallinity of the IDT electrode 30 and the reflective electrode 40 formed on the piezoelectric layer 51 decreases, and the power durability decreases. Also, in a region where the cut angle θ is 60° or more, the Rayleigh wave response generated in a frequency region approximately 0.75 times that of the fundamental wave increases. In response to this, by satisfying either (7) or (8) above, it is possible to provide a filter 10 having a piston mode IDT electrode in which the generation of third harmonic excitation and unwanted Rayleigh waves is suppressed while ensuring power durability in a region where the duty D is large, which is advantageous for miniaturization and suppression of manufacturing variations.

[0102] Moreover, the series arm resonator 11 (first acoustic wave resonator) of the filter 10 according to the present embodiment has (7) It is desirable to satisfy 0.538≦D≦0.588 and 42.5≦θ≦52.5 (within the triple-lined frame in Table 3).

[0103] In the region where the cut angle θ is 30° or less, the crystallinity of the IDT electrode 30 and the reflective electrode 40 formed on the piezoelectric layer 51 decreases, and the power durability decreases. In addition, as the cut angle θ becomes larger than 55°, the Rayleigh wave response increases. In contrast, by satisfying the above condition (7), it is possible to provide a filter 10 having a piston mode IDT electrode in which the generation of third harmonic excitation and unwanted Rayleigh waves is further suppressed while ensuring power durability in a region where the duty D is large, which is advantageous for miniaturization and suppression of manufacturing variations.

[0104] [5. Effects, etc.] As described above, the filter 10 according to the present embodiment and the second modification includes a first acoustic wave resonator having the piezoelectric substrate 50 and the IDT electrode 30 arranged on the piezoelectric substrate 50. The piezoelectric substrate 50 includes a piezoelectric layer 51 having the IDT electrode 30 formed thereon and made of lithium tantalate, a high acoustic velocity layer 53 having a bulk wave acoustic velocity faster than an acoustic wave acoustic velocity propagating through the piezoelectric layer 51, and a low acoustic velocity layer 52 arranged between the piezoelectric layer 51 and the high acoustic velocity layer 53 and having a bulk wave acoustic velocity slower than that of the bulk wave propagating through the piezoelectric layer 51. The IDT electrode 30 includes a plurality of electrode fingers 31 a and a plurality of electrode fingers 31 b arranged in parallel to each other, a bus bar electrode 32 a configured to connect one ends of the plurality of electrode fingers 31 a to each other, and a bus bar electrode 32 a configured to connect one ends of the plurality of electrode fingers 31 b to each other, and includes a plurality of electrode fingers 31 a and a bus bar electrode 32 b configured to connect one ends of the plurality of electrode fingers 31 b to each other. and bus bar electrode 32b arranged to face bus bar electrode 32a with multiple electrode fingers 31b therebetween. If an overlapping region W of multiple electrode fingers 31a and multiple electrode fingers 31b is defined as a first direction that is parallel to piezoelectric layer 51 and perpendicular to the extension direction of electrode fingers 31a and 31b, intersection region W has central region C located at the center of the extension direction and edge regions E located on both sides of central region C in the extension direction and having a slower sound speed than that in central region C. IDT electrode 30 further has mass addition films 35a and 35b (36a and 36b) arranged in a second direction perpendicular to the main surface of piezoelectric layer 51 of at least one of multiple electrode fingers 31a and multiple electrode fingers 31b in edge region E. If a duty of IDT electrode 30 is D and a cut angle of piezoelectric layer 51 is θ°, (1) 0.513≦D≦0.568 and 2.5≦θ≦17.5, (2) 0.538≦D≦0.568 and 17.5≦θ≦22.5, (3) 0.538≦D≦0.588, and 42.5≦θ≦52.5, (4) 0.538≦D≦0.613, and 52.5≦θ≦67.5, (5) 0.513≦D≦0.638, and 67.5≦θ≦77.5, and (6) Either 0.513≦D≦0.713 or 77.5≦θ≦92.5 is satisfied.

[0105] This makes it possible to provide a filter 10 having a piston mode IDT electrode 30 in which the generation of unwanted waves due to third harmonic excitation is suppressed in a region where the duty D is large, which is advantageous for miniaturization and suppression of manufacturing variations.

[0106] Also, for example, the filter 10 satisfies either (1) 0.538≦D≦0.588 and 42.5≦θ≦52.5, or (2) 0.538≦D≦0.613 and 52.5≦θ≦57.5.

[0107] This makes it possible to provide a filter 10 having a piston mode IDT electrode in which the generation of unnecessary waves such as third harmonic excitation and Rayleigh waves is suppressed while ensuring power resistance in a region where the duty D is large, which is advantageous for miniaturization and suppression of manufacturing variations.

[0108] Further, for example, the filter 10 satisfies 0.538≦D≦0.588 and 42.5≦θ≦52.5.

[0109] This makes it possible to provide filter 10 having piston mode IDT electrodes in which the generation of unwanted waves such as third harmonic excitation and Rayleigh waves is further suppressed while ensuring power resistance in a region where duty D is large, which is advantageous for miniaturization and suppression of manufacturing variations.

[0110] Also, for example, in the filter 10, the mass adding films 35a and 35b are arranged in the second direction in the edge region E, the plurality of electrode fingers 31a, the plurality of electrode fingers 31b, and the region between the plurality of electrode fingers 31a and the plurality of electrode fingers 31b.

[0111] According to this, each of the mass-adding films 35a and 35b can be formed continuously over a plurality of electrode fingers in the edge region E, so that the accuracy of forming the mass-adding films 35a and 35b can be improved.

[0112] Also for example, in filter 10, mass-adding films 35a and 35b include tantalum oxide.

[0113] With this, even if mass-adding films 35a and 35b are formed in the region between electrode fingers 31a and 31b, ripples in the transverse mode can be suppressed without deteriorating the resonance characteristics of the first acoustic wave resonator.

[0114] Also, for example, in the filter 10, the mass-adding films 36a and 36b are arranged in a second direction of only one of the multiple electrode fingers 31a and the multiple electrode fingers 31b in the edge region E, and the mass-adding films 36a and 36b are made of the same conductive material as the multiple electrode fingers 31a and the multiple electrode fingers 31b.

[0115] According to this, the mass adding films 36a and 36b can be formed in the same process as the electrode fingers 31a and 31b, respectively, and therefore, the manufacturing process can be simplified and ripples in the transverse mode can be suppressed.

[0116] Also, for example, in the filter 10, the duty D of the IDT electrode 30 is the average of the duties of the plurality of electrode fingers 31a and the plurality of electrode fingers 31b.

[0117] According to this, even if the duties of the plurality of electrode fingers 31a and the plurality of electrode fingers 31b are not uniform, the duty D of the IDT electrode 30 can be defined.

[0118] For example, filter 10 includes terminals 111 and 112 and a plurality of elastic wave resonators including a first elastic wave resonator, and the plurality of elastic wave resonators include series arm resonators 11 to 14 arranged in series on a path connecting terminals 111 and 112, and parallel arm resonators 15 to 18 connected between the path and ground.

[0119] This makes it possible to suppress unwanted waves of third harmonic excitation in the ladder-type filter 10.

[0120] For example, the filter 10A in accordance with the first modification includes a plurality of acoustic wave resonators including a first acoustic wave resonator, and the plurality of acoustic wave resonators include a longitudinally coupled resonator.

[0121] This makes it possible to suppress unwanted waves of third harmonic excitation in the filter 10A including the longitudinally coupled resonators.

[0122] For example, the multiplexer 1 according to the present embodiment includes a common terminal 100, a filter 10 or 10A connected to the common terminal 100, and a filter 20 connected to the common terminal 100.

[0123] This makes it possible to provide a multiplexer 1 in which unwanted waves of third harmonic excitation generated in the filter 10 are suppressed.

[0124] Also, for example, in the multiplexer 1, the filter 10 or 10A includes a plurality of acoustic wave resonators including a first acoustic wave resonator, and the first acoustic wave resonator is connected closest to the common terminal 100 among the plurality of acoustic wave resonators.

[0125] This effectively reduces the reflection loss at the frequency of the third harmonic excitation when the filter 10 or 10A is viewed from the common terminal 100. This makes it possible to suppress deterioration of the pass characteristic at the frequency of the third harmonic excitation of the filter 20 connected to the common terminal 100.

[0126] Also, for example, in the multiplexer 1, the passband of the filter 20 is located on the higher frequency side than the passband of the filter 10.

[0127] According to this, even if an unwanted wave of third harmonic excitation generated by the filter 10 is included in the vicinity of the passband of the filter 20, deterioration of the passband characteristic of the filter 20 can be suppressed.

[0128] (Other embodiments) Although the elastic wave device and multiplexer according to the present invention have been described above with reference to the embodiments and modifications, the present invention is not limited to the above-described embodiments and modifications. The present invention also includes modifications that can be made by those skilled in the art without departing from the spirit of the present invention, and various devices incorporating the elastic wave device and multiplexer according to the present invention.

[0129] Furthermore, for example, in the acoustic wave devices and multiplexers according to the above-described embodiments and modifications, matching elements such as inductors and capacitors, and switch circuits may be connected between the respective components.

[0130] The resonant frequency and anti-resonant frequency shown in the above embodiment and modified examples are derived, for example, by contacting an RF probe with two input / output electrodes of an acoustic wave resonator and measuring the reflection characteristics.

[0131] Features of the acoustic wave device and the multiplexer described based on the above embodiment and modifications will be described below.

[0132] <1> a first acoustic wave resonator including a substrate and an IDT electrode disposed on the substrate; The substrate is a piezoelectric layer formed with the IDT electrodes and made of lithium tantalate; a high acoustic velocity layer in which a bulk wave acoustic velocity is faster than an elastic wave acoustic velocity in the piezoelectric layer; a low acoustic velocity layer disposed between the piezoelectric layer and the high acoustic velocity layer, the low acoustic velocity layer having a bulk wave with a sound velocity slower than that of a bulk wave propagating through the piezoelectric layer; The IDT electrode is a plurality of first electrode fingers and a plurality of second electrode fingers arranged parallel to each other; a first bus bar electrode configured to connect one ends of the first electrode fingers to each other; a second bus bar electrode configured to connect one ends of the second electrode fingers to each other and disposed opposite the first bus bar electrode with the first electrode fingers and the second electrode fingers interposed therebetween, When a region where the plurality of first electrode fingers and the plurality of second electrode fingers overlap when viewed from a first direction that is parallel to the piezoelectric layer and perpendicular to an extension direction of the first electrode fingers and the second electrode fingers is defined as an intersection region, the intersection region has a central region that is located at the center of the extension direction, and edge regions that are located on both outer sides of the central region in the extension direction and have a slower sound speed than that in the central region, The IDT electrode further comprises: a mass-adding film disposed in a second direction perpendicular to a principal surface of the piezoelectric layer of at least one of the first electrode fingers and the second electrode fingers in the edge region; When the duty of the IDT electrode is D and the cut angle of the piezoelectric layer is θ°, (1) 0.513≦D≦0.568 and 2.5≦θ≦17.5, (2) 0.538≦D≦0.568 and 17.5≦θ≦22.5, (3) 0.538≦D≦0.588, and 42.5≦θ≦52.5, (4) 0.538≦D≦0.613, and 52.5≦θ≦67.5, (5) 0.513≦D≦0.638, and 67.5≦θ≦77.5, and (6) An elastic wave device that satisfies either 0.513≦D≦0.713 and 77.5≦θ≦92.5.

[0133] <2> (1) 0.538≦D≦0.588, and 42.5≦θ≦52.5, and (2) Either 0.538≦D≦0.613 and 52.5≦θ≦57.5 is satisfied; <1> The acoustic wave device according to claim 1 .

[0134] <3> 0.538≦D≦0.588 and 42.5≦θ≦52.5 are satisfied. <2> The acoustic wave device according to claim 1 .

[0135] <4> the mass-adding film is disposed in the second direction of the plurality of first electrode fingers, the plurality of second electrode fingers, and a region between the plurality of first electrode fingers and the plurality of second electrode fingers in the edge region; <1> ~ <3> 2. The acoustic wave device according to claim 1 ,

[0136] <5> The mass-adding film includes tantalum oxide. <4> The acoustic wave device according to claim 1 .

[0137] <6> the mass-adding film is disposed in the second direction of only at least one of the first electrode fingers and the second electrode fingers in the edge region, the mass-addition film is made of the same conductive material as the first electrode fingers and the second electrode fingers; <1> ~ <3> 2. The acoustic wave device according to claim 1 ,

[0138] <7> a duty D of the IDT electrode is an average of the duties of the first electrode fingers and the second electrode fingers. <1> ~ <6> 2. The acoustic wave device according to claim 1 ,

[0139] <8> The acoustic wave device includes: a first input / output terminal and a second input / output terminal; a plurality of acoustic wave resonators including the first acoustic wave resonator, The plurality of elastic wave resonators include a series arm resonator arranged in series on a path connecting the first input / output terminal and the second input / output terminal; a parallel arm resonator connected between the path and a ground. <1> ~ <7> 2. The acoustic wave device according to claim 1 ,

[0140] <9> The acoustic wave device includes: a plurality of acoustic wave resonators including the first acoustic wave resonator, the plurality of elastic wave resonators include longitudinally coupled resonators, <1> ~ <7> 2. The acoustic wave device according to claim 1 ,

[0141] <10> A common terminal; connected to the common terminal <1> ~ <9> and an elastic wave device according to any one of the preceding claims. a filter connected to the common terminal.

[0142] <11> the acoustic wave device includes a plurality of acoustic wave resonators including the first acoustic wave resonator, the first acoustic wave resonator is connected closest to the common terminal among the plurality of acoustic wave resonators; <10> 2. A multiplexer according to claim 1 .

[0143] <12> The filter has a pass band located on the higher frequency side than the acoustic wave device. <10> or <11> 2. A multiplexer according to claim 1 . [Industrial Applicability]

[0144] The present invention can be widely used as a transmit / receive filter and a multiplexer for use in the front end of a wireless communication terminal where low loss within the passband and high attenuation outside the passband are required. [Explanation of symbols]

[0145] 1 Multiplexer 2 Antennas 10, 10A, 20 Filter 11, 11A, 12, 13, 14 Series arm resonators 15, 16, 17, 18 Parallel arm resonators 19 Vertically coupled resonator 30, 30A IDT electrode 31a, 31b electrode fingers 32a, 32b Busbar electrodes 34 Protective layer 35a, 35b, 36a, 36b mass addition membrane 40, 40A reflective electrode 50 Piezoelectric Substrate 51 Piezoelectric layer 52 Low sound speed layer 53 High-sonic layer 54 Support substrate 100 Common terminal 110, 120 input / output terminals Terminals 111 and 112 191, 192, 193, 194, 195, 196, 197 Elastic wave resonators 310 Main electrode layer 311 Adhesion layer

Claims

1. a first acoustic wave resonator including a substrate and an IDT (InterDigital Transducer) electrode disposed on the substrate; The substrate is a piezoelectric layer formed with the IDT electrodes and made of lithium tantalate; a high acoustic velocity layer in which a bulk wave acoustic velocity is faster than an elastic wave acoustic velocity in the piezoelectric layer; a low acoustic velocity layer disposed between the piezoelectric layer and the high acoustic velocity layer, the low acoustic velocity layer having a bulk wave with a sound velocity slower than that of a bulk wave propagating through the piezoelectric layer; The IDT electrode is a plurality of first electrode fingers and a plurality of second electrode fingers arranged parallel to each other; a first bus bar electrode configured to connect one ends of the first electrode fingers to each other; a second bus bar electrode configured to connect one ends of the second electrode fingers to each other and disposed opposite the first bus bar electrode with the first electrode fingers and the second electrode fingers interposed therebetween, When a region where the plurality of first electrode fingers and the plurality of second electrode fingers overlap each other as viewed from a first direction that is parallel to the piezoelectric layer and perpendicular to an extension direction of the first electrode fingers and the second electrode fingers is defined as an intersection region, the intersection region has a central region that is located at the center of the extension direction, and edge regions that are located on both outer sides of the central region in the extension direction and have a slower sound speed than that in the central region, The IDT electrode further comprises: a mass-adding film disposed in a second direction perpendicular to a main surface of the piezoelectric layer of at least one of the first electrode fingers and the second electrode fingers in the edge region; When the duty of the IDT electrode is D and the cut angle of the piezoelectric layer is θ°, (1) 0.513≦D≦0.568, and 2.5≦θ≦17.5, (2) 0.538≦D≦0.568, and 17.5≦θ≦22.5, (3) 0.538≦D≦0.588, and 42.5≦θ≦52.5, (4) 0.538≦D≦0.613, and 52.5≦θ≦67.5, (5) 0.513≦D≦0.638, and 67.5≦θ≦77.5, and (6) Any one of 0.513≦D≦0.713 and 77.5≦θ≦92.5 is satisfied; Elastic wave device.

2. (1) 0.538≦D≦0.588, and 42.5≦θ≦52.5, and (2) Either of 0.538≦D≦0.613 and 52.5≦θ≦57.5 is satisfied; The acoustic wave device according to claim 1 .

3. 0.538≦D≦0.588 and 42.5≦θ≦52.5 are satisfied. The acoustic wave device according to claim 2 .

4. the mass-adding film is disposed in the second direction of the plurality of first electrode fingers, the plurality of second electrode fingers in the edge region, and a region between the plurality of first electrode fingers and the plurality of second electrode fingers; The elastic wave device according to any one of claims 1 to 3.

5. The mass-adding film includes tantalum oxide. The acoustic wave device according to claim 4 .

6. the mass-adding film is disposed in the second direction of only at least one of the first electrode fingers and the second electrode fingers in the edge region, the mass-addition film is made of the same conductive material as the first electrode fingers and the second electrode fingers; The elastic wave device according to any one of claims 1 to 3.

7. a duty D of the IDT electrode is an average of the duties of the first electrode fingers and the second electrode fingers. The elastic wave device according to any one of claims 1 to 3.

8. The acoustic wave device includes: a first input / output terminal and a second input / output terminal; a plurality of acoustic wave resonators including the first acoustic wave resonator, The plurality of elastic wave resonators include a series arm resonator arranged in series on a path connecting the first input / output terminal and the second input / output terminal; a parallel arm resonator connected between the path and a ground. The elastic wave device according to any one of claims 1 to 3.

9. The acoustic wave device includes: a plurality of acoustic wave resonators including the first acoustic wave resonator, the plurality of elastic wave resonators include longitudinally coupled resonators, The elastic wave device according to any one of claims 1 to 3.

10. A common terminal; The elastic wave device according to any one of claims 1 to 3, which is connected to the common terminal; a filter connected to the common terminal. Multiplexer.

11. the acoustic wave device includes a plurality of acoustic wave resonators including the first acoustic wave resonator, the first acoustic wave resonator is connected closest to the common terminal among the plurality of acoustic wave resonators; 11. The multiplexer of claim 10.

12. The filter has a pass band located on the higher frequency side than the acoustic wave device.

11. The multiplexer of claim 10.

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