Elastic wave device and multiplexer

Abstract

The invention provides an elastic wave device and a multiplexer. A filter is provided with an elastic wave resonator having a piezoelectric substrate and IDT electrodes, the piezoelectric substrate having a piezoelectric layer, a low-acoustic-velocity layer, and a high-acoustic-velocity layer, the intersection region of the IDT electrodes having a central region and an edge region, and the IDT electrodes having a mass-added film disposed in the edge region. The duty ratio D of the IDT electrode and the cutting angle [theta] degree of the piezoelectric layer satisfy any one of 0.513 < = D < = 0.568 and 2.5 < = [theta] < = 17.5, 0.538 < = D < = 0.568 and 17.5 < = [theta] < = 22.5, 0.538 < = D < = 0.588 and 42.5 < = [theta] < = 52.5, 0.538 < = D < = 0.613 and 52.5 < = [theta] < = 67.5, 0.513 < = D < = 0.638 and 67.5 < = [theta] < = 77.5, and 0.513 < = D < = 0.713 and 77.5 < = [theta] < = 92.5.

Description

Technical Field

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

[0002] Patent documents 1 and 2 disclose an electrode structure of a surface acoustic wave resonator using a substrate including a piezoelectric layer, a low acoustic velocity layer, and a high acoustic velocity layer, and a laminated structure of the substrate. Patent document 1 discloses a piston mode structure in which the width of a plurality of electrode fingers constituting an IDT (InterDigital Transducer) electrode is locally widened, and Patent document 2 discloses a piston mode structure in which a mass-added film is arranged at the front end of a plurality of electrode fingers constituting an IDT electrode. According to the piston mode structure disclosed in Patent documents 1 and 2, ripples in the transverse mode can be suppressed.

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2021 / 060150

[0006] Patent Document 2: Japanese Patent Application Publication No. 2019-092095

[0007] However, in the elastic wave resonator having the piston mode IDT electrode disclosed in Patent Documents 1 and 2, it is not possible to sufficiently suppress the unnecessary wave (third harmonic excitation) generated at a frequency three times that of the fundamental wave. Summary of the invention

[0008] Problem that the invention aims to solve

[0009] Therefore, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an elastic wave device and a multiplexer having a piston-mode IDT electrode that suppresses generation of unnecessary waves caused by third-order harmonic excitation.

[0010] Technical solutions to solve problems

[0011] To achieve the above object, an elastic wave device according to one embodiment of the present invention comprises a first elastic wave resonator having a substrate and an IDT electrode arranged on the substrate, the substrate having a piezoelectric layer including lithium tantalate on which the IDT electrode is formed, a high acoustic velocity layer in which a bulk wave propagates at a higher acoustic velocity than an elastic wave propagating in the piezoelectric layer, and a low acoustic velocity layer arranged between the piezoelectric layer and the high acoustic velocity layer and in which a bulk wave propagates at a lower acoustic velocity than the bulk wave propagating in the piezoelectric layer, the IDT electrode having a plurality of first electrode fingers and a plurality of second electrode fingers arranged in parallel with each other, a first bus bar electrode configured to connect one ends of the plurality of first electrode fingers to each other, and a plurality of first electrode fingers and a plurality of second electrode fingers sandwiched therebetween. The second bus bar electrode arranged opposite to the first bus bar electrode, when the area where the plurality of first electrode fingers and the plurality of second electrode fingers overlap each other when viewed from a first direction parallel to the piezoelectric layer and orthogonal to the extension direction of the first electrode finger and the second electrode finger is set as an intersection area, the intersection area has a central area located in the center of the extension direction, and edge areas located on both outer sides of the extension direction relative to the central area and having a lower sound velocity than the sound velocity in the central area, the IDT electrode also has a mass addition film in a second direction perpendicular to the main surface of the piezoelectric layer for at least one of the plurality of first electrode fingers and the plurality of second electrode fingers arranged in the edge area, and when the duty ratio of the IDT electrode is set to D and the cutting angle of the piezoelectric layer is set to θ°, it is satisfied

[0012] (1) 0.513≤D≤0.568 and 2.5≤θ≤17.5,

[0013] (2) 0.538≤D≤0.568 and 17.5≤θ≤22.5,

[0014] (3) 0.538≤D≤0.588 and 42.5≤θ≤52.5,

[0015] (4) 0.538≤D≤0.613 and 52.5≤θ≤67.5,

[0016] (5) 0.513 ≤ D ≤ 0.638 and 67.5 ≤ θ ≤ 77.5, and

[0017] (6) Any one of 0.513≤D≤0.713 and 77.5≤θ≤92.5.

[0018] Effects of the Invention

[0019] According to the present invention, it is possible to provide an elastic wave device and a multiplexer having a piston-mode IDT electrode that suppresses generation of unnecessary waves caused by third-order harmonic excitation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1It is a circuit structure diagram of a multiplexer involved in an embodiment.

[0021] Figure 2A It is a circuit configuration diagram of an elastic wave device according to an embodiment.

[0022] Figure 2B It is a circuit configuration diagram of an elastic wave device according to Modification 1 of the embodiment.

[0023] Figure 3A It is a top view of a first elastic wave resonator according to the embodiment.

[0024] Figure 3B It is a first cross-sectional view of a first elastic wave resonator according to the embodiment.

[0025] Figure 3C It is a second cross-sectional view of the first elastic wave resonator according to the embodiment.

[0026] Figure 4A It is a plan view of a first elastic wave resonator according to Modification 2 of the embodiment.

[0027] Figure 4B It is a cross-sectional view of a first elastic wave resonator according to Modification 2 of the embodiment.

[0028] Figure 5A This is a graph showing the resonance characteristics of the elastic wave resonator when the duty ratio of the IDT electrode is changed.

[0029] Figure 5B : is a graph showing the phase of the third harmonic excitation signal of the elastic wave resonator when the duty ratio of the IDT electrode is changed.

[0030] Figure 5C : is a graph showing the relationship between the duty ratio of the IDT electrode and the phase of the third harmonic excitation signal.

[0031] Description of Reference Numerals

[0032] 1 Multiplexer;

[0033] 2 Antennas;

[0034] 10, 10A, 20 filter;

[0035] 11, 11A, 12, 13, 14 series arm resonator;

[0036] 15, 16, 17, 18 Parallel arm resonator;

[0037] 19 Longitudinal coupling resonator;

[0038] 30, 30A IDT electrode;

[0039] 31a, 31b electrode fingers;

[0040] 32a, 32b bus bar electrodes;

[0041] 34 protective layer;

[0042] 35a, 35b, 36a, 36b quality additional membrane;

[0043] 40, 40A reflective electrode;

[0044] 50 piezoelectric substrate;

[0045] 51 piezoelectric layer;

[0046] 52 Low sound velocity layer;

[0047] 53 high sound velocity layer;

[0048] 54 support base plate;

[0049] 100 common terminals;

[0050] 110, 120 input and output terminals;

[0051] 111, 112 terminals;

[0052] 191, 192, 193, 194, 195, 196, 197 elastic wave resonator;

[0053] 310 main electrode layer;

[0054] 311 close contact layer. DETAILED DESCRIPTION

[0055] The embodiments of the present invention are described in detail below using the accompanying drawings. In addition, the embodiments described below are all general or specific examples. The numerical values, shapes, materials, components, configurations of components, and connection methods shown in the following embodiments are examples, and the main purpose is not to limit the present invention.

[0056] In addition, each figure is a schematic diagram that is appropriately emphasized, omitted, or adjusted in proportion to illustrate the present invention, and is not necessarily strictly illustrated, and sometimes differs from the actual shape, positional relationship, and proportion. In each figure, the same reference numerals are marked for substantially the same structure, and repeated descriptions are sometimes omitted or simplified.

[0057] In the circuit configuration of the present disclosure, “connected between A and B” or “connected between A and B” means connected between A and B or connected to both A and B.

[0058] 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 constituting path B.

[0059] In addition, terms such as “parallel” and “perpendicular” indicating the relationship between elements, terms such as “rectangular” indicating the shape of an element, and numerical ranges do not have strict meanings but mean substantially equivalent ranges and include, for example, errors of several %.

[0060] In addition, in the present disclosure, the so-called "terminal" means a point where a conductor in an element ends. In addition, when the impedance of the conductor between elements is sufficiently low, the terminal is interpreted not only as a single point but also as an arbitrary point on the conductor between elements or the conductor as a whole.

[0061] In the following embodiments, the passband of an elastic wave device or a filter is defined as a frequency band between two frequencies that is 3 dB greater than the minimum value of insertion loss in the passband.

[0062] In addition, in the present disclosure, frequency band A and frequency band B mean frequency bands predefined by standardization organizations (e.g., 3GPP (registered trademark), IEEE (Institute of Electrical and Electronics Engineers), etc.) for communication systems constructed using radio access technology (RAT: Radio Access Technology). In the present embodiment, as a communication system, for example, an LTE (Long Term Evolution) system, a 5G (5th Generation)-NR (New Radio) system, and a WLAN (Wireless Local Area Network) system can be used, but are not limited to these.

[0063] Furthermore, the uplink operating frequency band of frequency band A means a frequency range designated for uplink in frequency band A. Furthermore, the downlink operating frequency band of frequency band A means a frequency range designated for downlink in frequency band A.

[0064] (Implementation Method)

[0065] [1. Circuit structure of multiplexer]

[0066] Figure 1 1 is a circuit diagram of a multiplexer 1 according to the embodiment. The multiplexer 1 includes filters 10 and 20 , a common terminal 100 , and input / output terminals 110 and 120 .

[0067] The common terminal 100 is connected to, for example, the antenna 2 .

[0068] The filter 10 is an example of an elastic wave device, and has a first elastic wave resonator. The filter 10 is connected to the common terminal 100, and has a passband including, for example, an uplink operating frequency band of the frequency band A. The filter 20 is connected to the common terminal 100, and has, for example, a passband including, for example, a downlink operating frequency band of the frequency band A. The filters 10 and 20 constitute, for example, a duplexer for the frequency band A.

[0069] Alternatively, the filter 10 may have a passband including at least one of an uplink operating frequency band and a downlink operating frequency band of frequency band A, and the filter 20 may have a passband including at least one of an uplink operating frequency band and a downlink operating frequency band of frequency band B different from frequency band A. In this case, the filters 10 and 20 constitute a diplexer.

[0070] In the present embodiment, the passband of the filter 10 is located on the lower frequency side than the passband of the filter 20. At least one of the plurality of elastic wave resonators constituting the filter 10 can reduce the unnecessary waves of the third harmonic excitation. Therefore, even if the unnecessary waves of the third harmonic excitation generated by the filter 10 are included in the vicinity of the passband of the filter 20, the deterioration of the pass characteristic of the filter 20 can be suppressed.

[0071] In addition, the passband of the filter 10 may be located on the high-frequency side relative to the passband of the filter 20 .

[0072] Figure 2A 1 is a circuit diagram of a filter 10 according to the 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 .

[0073] 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 .

[0074] Series arm resonators 11 to 14 are elastic wave resonators, respectively, and are arranged in series on a path connecting terminal 111 and terminal 112. Series arm resonator 11 is an example of a first elastic wave resonator, and is connected closest to common terminal 100 among series arm resonators 11 to 14 and parallel arm resonators 15 to 18.

[0075] The parallel arm resonator 15 is an elastic wave resonator connected between the connection point of the series arm resonators 11 and 12 and the ground. The parallel arm resonator 16 is an elastic wave resonator connected between the connection point of the series arm resonators 12 and 13 and the ground. The parallel arm resonator 17 is an elastic wave resonator connected between the connection point of the series arm resonators 13 and 14 and the ground. The parallel arm resonator 18 is an elastic wave resonator connected between the connection point of the series arm resonator 14 and the terminal 112 and the ground.

[0076] With the above configuration, the filter 10 constitutes, for example, a ladder-type bandpass filter. The series arm resonators 11 to 14 and the parallel arm resonators 15 to 18 each have an IDT electrode disposed on a substrate having piezoelectricity.

[0077] in addition, Figure 2A The circuit configuration of the filter 10 shown is an example, and the number of series arm resonators and the number of parallel arm resonators are not limited to 4, respectively, and may be 1 or more. In addition, an inductor may be connected between the parallel arm resonator and the ground.

[0078] In addition, the filter 10 is not limited to a ladder-type bandpass filter. Figure 2B As shown, a filter including a longitudinally coupled resonator in which a plurality of elastic wave resonators are arranged in parallel in the direction of propagation of the elastic wave may be used.

[0079] Figure 2B FIG. 1 is a circuit diagram of a filter 10A according to a first modification of the embodiment. The filter 10A is an example of an elastic wave device and is connected to a common terminal 100. Figure 2B As shown, the filter 10A is a filter circuit including a longitudinally coupled resonator 19 composed of seven elastic wave resonators, and includes the longitudinally coupled resonator 19, series arm resonators 11, 12, and 13, parallel arm resonators 15 and 16, and terminals 111 and 112. The terminal 111 is connected to the common terminal 100, and the terminal 112 is connected to the input / output terminal 110.

[0080] Longitudinally coupled resonator 19 includes elastic wave resonators 191 , 192 , 193 , 194 , 195 , 196 , and 197 , one end of which is connected to terminal 111 via series arm resonators 11 and 12 , and the other end of which is connected to terminal 112 via series arm resonator 13 .

[0081] Each of the elastic wave resonators 191 to 197 has an IDT electrode disposed on a substrate having piezoelectricity. The IDT electrodes of the elastic wave resonators 191 to 197 are composed of two comb-shaped electrodes facing each other. One comb-shaped electrode of each of the elastic wave resonators 191, 193, 195, and 197 is connected to the terminal 111 via the series arm resonators 11 and 12, and the other comb-shaped electrode of each of the elastic wave resonators 191, 193, 195, and 197 is connected to the ground. One comb-shaped electrode of each of the elastic wave resonators 192, 194, and 196 is connected to the terminal 112 via the series arm resonator 13, and the other comb-shaped electrode of each of the elastic wave resonators 192, 194, and 196 is connected to the ground. The elastic wave resonators 191 to 197 are disposed in the order of the elastic wave resonators 191, 192, 193, 194, 195, 196, and 197 along the propagation direction of the elastic wave.

[0082] The series arm resonators 11, 12, and 13 are arranged in series on a path connecting the terminals 111 and 112. The parallel arm resonators 15 and 16 are connected between the above path and the ground, respectively. The series arm resonator 11 is an example of a first elastic 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.

[0083] The filter 20 may be any of a bandpass filter, a notch filter, a lowpass filter, and a highpass filter, and includes at least one of an elastic wave resonator, an inductor, and a capacitor.

[0084] When the filter 20 includes an elastic wave resonator, the filters 10 and 20 may be formed on the same piezoelectric substrate. Thus, the multiplexer 1 can be miniaturized and the manufacturing process can be simplified. In addition, when the filter 20 includes an elastic wave resonator, the film thickness of the IDT electrode of the elastic wave resonator may be the same as the film thickness of the IDT electrode of the elastic wave resonator constituting the filter 10. Thus, the manufacturing process of the multiplexer 1 can be simplified.

[0085] [2. Structure of the first elastic wave resonator]

[0086] Next, the structure of the first elastic wave resonator constituting the filter 10 will be described. Figure 3A It is a top view of the series arm resonator 11 according to the embodiment. Figure 3B It is a first cross-sectional view of the series arm resonator 11 according to the embodiment. Figure 3C It is a second cross-sectional view of the series arm resonator 11 according to the embodiment. Figure 3A to Figure 3C The series arm resonator 11 shown is an example of a first elastic wave resonator. Figure 3B It is shown in Figure 3A The cross-sectional view at line IIIB-IIIB is shown in Figure 3C It is shown in Figure 3A Cross-sectional view at line IIIC-IIIC.

[0087] like Figure 3A to Figure 3C As shown in FIG. 1 , the series arm resonator 11 includes a piezoelectric substrate 50 , an IDT electrode 30 , and a reflective electrode 40 . Figure 3A to Figure 3C The series arm resonator 11 is shown to illustrate a typical structure of the first elastic wave resonator constituting the filter 10, and the number and length of the electrode fingers constituting the IDT electrode 30 are not limited thereto. The IDT electrode 30 and the reflective electrode 40 are arranged on the piezoelectric substrate 50 (in the positive z-axis direction).

[0088] like Figure 3B as well as Figure 3C As shown, the piezoelectric substrate 50 has piezoelectricity and includes a piezoelectric layer 51 , a low acoustic velocity layer 52 , a high acoustic velocity layer 53 , and a support substrate 54 .

[0089] The piezoelectric layer 51 has the IDT electrode 30 and the reflective electrode 40 arranged on one surface thereof. For example, lithium tantalate (LiTaO 3 ) or a material containing lithium tantalate as a main component can be used for the piezoelectric layer 51 . The film thickness of the piezoelectric layer 51 is, for example, 900 nm.

[0090] The high acoustic velocity layer 53 is arranged on the other side of the piezoelectric layer 51, and the body wave propagating in the high acoustic velocity layer 53 is faster than the elastic wave propagating in the piezoelectric layer 51. The high acoustic velocity layer 53 can be made of, for example, piezoelectric materials such as silicon nitride, aluminum nitride, lithium tantalate, lithium niobate, quartz, alumina, sapphire, magnesium oxide, silicon carbide, zirconium oxide, cordierite, mullite, steatite, forsterite, dielectric materials such as diamond and glass, semiconductors such as silicon and gallium nitride, or resins, or materials mainly composed of the above materials. The film thickness of the high acoustic velocity layer 53 is, for example, 300 nm.

[0091] 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. The acoustic velocity of the body wave propagating in the low acoustic velocity layer 52 is lower than that of the body wave propagating in the piezoelectric layer 51. According to this structure and the property that the energy of the elastic wave is essentially concentrated in the medium of low acoustic velocity, the leakage of the surface acoustic wave energy to the outside of the piezoelectric layer 51 can be suppressed. For example, the low acoustic velocity layer 52 can use dielectrics such as silicon oxide, glass, silicon oxynitride, lithium oxide, tantalum oxide, or compounds in which fluorine, carbon, and boron are added to silicon oxide, or materials with the above materials as main components. The film thickness of the low acoustic velocity layer 52 is, for example, 300 nm.

[0092] The support substrate 54 is arranged 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. The support substrate 54 can be made of, for example, silicon, aluminum nitride, lithium tantalate, lithium niobate, piezoelectrics such as quartz, alumina, sapphire, magnesium oxide, silicon nitride, silicon carbide, zirconium oxide, cordierite, mullite, steatite, ceramics such as forsterite, dielectrics such as diamond and glass, semiconductors such as gallium nitride, or resins, or materials with the above materials as main components. The thickness of the support substrate 54 is, for example, 125 μm.

[0093] According to the stacked structure of the piezoelectric substrate 50, the Q value at the resonant frequency and the anti-resonant frequency can be greatly improved compared with the conventional structure using a single-layer piezoelectric substrate. That is, an elastic wave resonator with a high Q value can be formed, and thus a high-frequency filter with a small insertion loss can be formed using the elastic wave resonator.

[0094] Alternatively, the piezoelectric layer 51 may be directly disposed on the high acoustic velocity layer 53 without disposing the low acoustic velocity layer 52 .

[0095] In addition, the high acoustic velocity layer 53 and the supporting substrate 54 may be combined to form a high acoustic velocity supporting substrate. The high acoustic velocity supporting 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 supporting substrate is a substrate in which the acoustic velocity of the body wave in the high acoustic velocity supporting substrate becomes higher than the elastic waves such as the surface wave and the boundary wave propagating in the piezoelectric layer 51, and functions to confine the surface acoustic wave in the portion where the piezoelectric layer 51 and the low acoustic velocity layer 52 are stacked, and does not leak to the lower part of the high acoustic velocity supporting substrate. As the material of the high acoustic velocity support substrate, for example, piezoelectrics such as aluminum nitride, lithium tantalate, lithium niobate, and quartz, alumina, sapphire, magnesium oxide, silicon nitride, silicon carbide, zirconium oxide, cordierite, mullite, steatite, forsterite, spinel, ceramics such as sialon, dielectrics such as aluminum oxide, silicon oxynitride, DLC (diamond-like carbon), and diamond, or semiconductors such as silicon, or materials with the above materials as the main component can be used. In addition, the above spinel contains aluminum compounds containing one or more elements selected from Mg, Fe, Zn, Mn, etc. and oxygen. As examples of the above spinel, MgAl2O4, FeAl2O4, ZnAl2O4, and MnAl2O4 can be listed.

[0096] In this specification, the term "main component of a material" refers to a component that accounts for more than 50% by weight of the material. The main component may be present in any state of single crystal, polycrystalline, or amorphous, or in a mixed state thereof.

[0097] In addition, the piezoelectric substrate 50 may be replaced with a structure in which a support substrate, an energy confinement layer, and a piezoelectric layer are stacked in sequence. An IDT electrode 30 and a reflective electrode 40 are formed on the piezoelectric layer. For example, a LiTaO3 piezoelectric single crystal or a piezoelectric ceramic may be used for the piezoelectric layer. The support substrate is a substrate that supports the piezoelectric layer, the energy confinement layer, and the IDT electrode 30.

[0098] The energy confinement layer includes one or more layers, and the speed of the body acoustic wave propagating in at least one of the layers is greater than the speed of the elastic wave propagating near the piezoelectric layer. For example, the energy confinement layer can also be a stacked structure of a low-acoustic-velocity layer and a high-acoustic-velocity layer. The low-acoustic-velocity layer is a film in which the sound speed of the body wave in the low-acoustic-velocity layer becomes low compared to the sound speed of the elastic wave propagating in the piezoelectric layer. The high-acoustic-velocity layer is a film in which the sound speed of the body wave in the high-acoustic-velocity layer becomes high compared to the sound speed of the elastic wave propagating in the piezoelectric layer. In addition, the supporting substrate can also be used as the high-acoustic-velocity layer.

[0099] Alternatively, the energy confinement layer may be an acoustic impedance layer having a structure in which low acoustic impedance layers having relatively low acoustic impedance and high acoustic impedance layers having relatively high acoustic impedance are alternately stacked.

[0100] like Figure 3A As shown, the IDT electrode 30 includes a plurality of electrode fingers 31 a and a plurality of electrode fingers 31 b , bus bar electrodes 32 a and 32 b , and mass addition films 35 a and 35 b .

[0101] The plurality of electrode fingers 31a and the plurality of electrode fingers 31b extend in a direction perpendicular to the elastic wave propagation direction (x-axis direction: first direction), and the plurality of electrode fingers 31a and the plurality of electrode fingers 31b are arranged parallel to each other. The electrode finger 31a is an example of a first electrode finger, and the electrode finger 31b is an example of a second electrode finger.

[0102] The bus bar electrode 32a is an example of the first bus bar electrode, and is configured to connect one ends of the plurality of electrode fingers 31a to each other. The bus bar electrode 32a extends in a direction (x-axis direction) intersecting the extension direction (y-axis direction) of the plurality of electrode fingers 31a. The bus bar electrode 32b is an example of the second bus bar electrode, and is configured to connect one ends of the plurality of electrode fingers 31b to each other. The bus bar electrode 32b extends in a direction (x-axis direction: first direction) intersecting the extension direction (y-axis direction) of the plurality of electrode fingers 31b. The bus bar electrodes 32a and 32b are arranged opposite to each other with the plurality of electrode fingers 31a and the plurality of electrode fingers 31b sandwiched therebetween. The other ends of the plurality of electrode fingers 31a are opposite to the bus bar electrode 32b, and the other ends of the plurality of electrode fingers 31b are opposite to the bus bar electrode 32a. In addition, the bus bar electrodes 32 a and 32 b may extend in a direction intersecting the extending direction (y-axis direction) and in a direction not orthogonal to the extending direction (y-axis direction).

[0103] The reflective electrode 40 is arranged on both sides of the IDT electrode 30 in a direction (x-axis direction) perpendicular to the extending direction of the plurality of electrode fingers 31a and the plurality of electrode fingers 31b so as to be adjacent to the IDT electrode 30. The reflective electrode 40 is configured to confine a given high-frequency signal resonating in the IDT electrode 30 within the IDT electrode 30. The reflective electrode 40 has a plurality of electrode fingers and a pair of bus bar electrodes. The plurality of electrode fingers of the reflective electrode 40 are arranged in parallel with the plurality of electrode fingers 31a and 31b. One of the bus bar electrodes of the reflective electrode 40 is configured to connect one ends of the plurality of electrode fingers of the reflective electrode 40 to each other, and the other of the bus bar electrodes of the reflective electrode 40 is configured to connect the other ends of the plurality of electrode fingers of the reflective electrode 40 to each other. In addition, in the series arm resonator 11 involved in this embodiment, the reflective electrode 40 may not be present.

[0104] like Figure 3B as well as Figure 3C As shown, the plurality of electrode fingers 31 a and 31 b , the bus bar electrodes 32 a and 32 b , and the reflective electrode 40 form a stacked structure of, for example, an adhesion layer 311 and a main electrode layer 310 .

[0105] The main electrode layer 310, for example, has aluminum (Al) as a main component, 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 the adhesion of the main electrode layer 310 to the piezoelectric layer 51. The adhesion layer 311, for example, contains titanium (Ti), and has a thickness of, for example, 30 nm. In addition, the plurality of electrode fingers 31a and 31b, the busbar electrodes 32a and 32b, and the reflective electrode 40 are not limited to the above-mentioned stacked structure, and may be composed of metals or alloys such as Ti, Al, Cu, Pt, Au, Ag, and Pd, and may also be composed of a plurality of stacked bodies composed of the above-mentioned metals or alloys.

[0106] In addition, if Figure 3B as well as Figure 3C As shown, a protective layer 34 is arranged to cover the plurality of electrode fingers 31a and 31b and the busbar electrodes 32a and 32b. The protective layer 34 is a layer for the purpose of protecting the main electrode layer 310 from the external environment, adjusting the frequency-temperature characteristics, and improving moisture resistance, and is, for example, a dielectric film with silicon oxide as the main component. In addition, the protective layer 34 may not be arranged.

[0107] Here, if Figure 3AAs shown in FIG. 1 , the main surface of the piezoelectric substrate 50 is divided into a plurality of regions. When viewed from a first direction (x-axis direction) parallel to the main surface of the piezoelectric layer 51 and orthogonal to the extension direction of the electrode fingers 31a and 31b, the region where the plurality of electrode fingers 31a and the plurality of electrode fingers 31b overlap each other is defined as an intersection region W. The intersection region W includes a central region C and an edge region E. The central region C is located at the center of the extension direction (y-axis direction). The edge region E is located on both sides of the central region C closer to the extension direction (y-axis direction), and is a region where the sound velocity is lower than the sound velocity in the central region C.

[0108] The mass addition films 35a and 35b are respectively arranged along the x-axis direction in the second direction (z-axis direction) perpendicular to the main surface of the piezoelectric layer 51 in the plurality of electrode fingers 31a and 31b in the edge region E and in the region between the electrode fingers 31a and 31b. By arranging the mass addition films 35a and 35b, the edge region E has a lower acoustic velocity than the central region C.

[0109] As described above, the central region C is defined as a region sandwiched by the mass adding films 35a and 35b of the IDT electrode 30 and not provided with the mass adding films 35a and 35b, and the length of the central region C in the extension direction (y-axis direction) is arbitrary. In addition, the edge region E is defined as a region located on both sides of the central region C in the extension direction (y-axis direction) and provided with the mass adding film 35a or 35b.

[0110] Furthermore, as a structure for making 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 addition film 35 a or 35 b in addition to the structure in the central region C.

[0111] As mass addition films 35a and 35b for setting the edge region E as a region where the sound velocity is lower than the sound velocity in the central region C, for example, a dielectric film or a metal film having any one of tantalum oxide (Ta2O5), titanium oxide (TiO2), hafnium oxide (HfO2), niobium oxide (Nb2O5), tungsten oxide (WO3), cerium oxide (CeO2), and silicon oxide (SiO2) as a main component can be listed.

[0112] The mass addition films 35a and 35b may not be arranged in the region between the electrode fingers 31a and 31b in the edge region E. Furthermore, the mass addition film 35a may be arranged only on the electrode fingers 31b in the edge region E, and the mass addition film 35b may be arranged only on the electrode fingers 31a in the edge region E.

[0113] Here, electrode parameters of the IDT electrode constituting the elastic wave resonator are described.

[0114] The wavelength of the so-called elastic wave resonator is given by Figure 3A as well as Figure 3B The repetition period of the multiple electrode fingers 31a or 31b shown is specified by the wavelength λ. In other words, the wavelength λ is twice the distance between the center of the adjacent electrode finger 31a and the center of the electrode finger 31b, that is, the electrode finger pitch. In addition, when the line width of the electrode fingers 31a and 31b is set to L and the gap width between the adjacent electrode fingers 31a and electrode fingers 31b is set to S, the electrode finger pitch is defined by (L+S). In addition, the duty cycle D of the IDT electrode 30 is the line width occupancy rate of the multiple electrode fingers 31a and 31b, which is the ratio of the line width of the multiple electrode fingers 31a and 31b to the sum of the line width and the gap width, and is defined by L / (L+S). In addition, Figure 3B In FIG. 5 , the height of the electrode fingers 31 a and 31 b is denoted as h.

[0115] In the IDT electrode 30, when the intervals between adjacent electrode fingers are not constant, the electrode finger pitch of the IDT electrode 30 is defined by the average electrode finger pitch of the IDT electrode 30. If the total number of electrode fingers 31a and 31b included in the IDT electrode 30 is Ni, and the center-to-center distance between the electrode fingers at one end of the IDT electrode 30 in the elastic wave propagation direction (x-axis direction) and the electrode fingers at the other end is Di, the average electrode finger pitch of the IDT electrode 30 is defined as Di / (Ni-1).

[0116] When the duty ratios of the electrode fingers 31 a and 31 b are different, the duty ratio D of the IDT electrode 30 is defined as a value obtained by averaging the duty ratios of the plurality of electrode fingers 31 a and the plurality of electrode fingers 31 b .

[0117] The IDT electrode 30 of the series arm resonator 11 according to the present embodiment has a so-called 3D piston mode structure in which a mass added film is arranged in the second direction of the electrode fingers, and can suppress ripples in the transverse mode.

[0118] Furthermore, the IDT electrode 30 of the series arm resonator 11 according to the present embodiment is suitable for increasing the duty ratio of the IDT electrode 30 with high precision, compared with an IDT electrode having a so-called 2D piston structure in which the width of a part of electrode fingers is widened in the first direction.

[0119] [3. Structure of the first elastic wave resonator according to modification 2]

[0120] Next, the structure of the first elastic wave resonator constituting the filter 10 according to the second modification will be described. Figure 4A 1 is a plan view of a series arm resonator 11A according to Modification 2 of the embodiment. Figure 4BFIG. 1 is a cross-sectional view of a series arm resonator 11A according to a second modification of the embodiment. Figure 4B It is shown in Figure 4A Cross-sectional view at line IVB-IVB.

[0121] The filter 10 according to the second modification has Figure 2A In the circuit shown, the series arm resonator 11 is replaced with a series arm resonator 11A. Figure 4A as well as Figure 4B The series arm resonator 11A shown is an example of a first elastic wave resonator.

[0122] like Figure 4A as well as Figure 4B As shown in FIG. 1 , the series arm resonator 11A includes a piezoelectric substrate 50 , an IDT electrode 30A, and a reflective electrode 40A. Figure 4A as well as Figure 4B The series arm resonator 11A shown is used to illustrate a typical structure of the first elastic wave resonator constituting the filter 10 according to Modification 2, and the number and length of the electrode fingers constituting the IDT electrode 30A are not limited thereto. The IDT electrode 30A and the reflective electrode 40A are arranged on the piezoelectric substrate 50 (in the positive z-axis direction).

[0123] The series arm resonator 11A involved in this modification is different from the series arm resonator 11 involved in the embodiment only in the structure of the mass added films 36a and 36b. Hereinafter, regarding the series arm resonator 11A involved in this modification, the description of the same structure as the series arm resonator 11 involved in the embodiment is omitted, and the description is centered on the different structures.

[0124] like Figure 4A As shown, the IDT electrode 30A includes a plurality of electrode fingers 31 a and a plurality of electrode fingers 31 b , bus bar electrodes 32 a and 32 b , and mass addition films 36 a and 36 b .

[0125] The mass addition films 36a and 36b are respectively arranged in the second direction (z-axis direction) perpendicular to the main surface of the piezoelectric layer 51 at the front ends of the plurality of electrode fingers 31a and 31b in the edge region E. The mass addition films 36a and 36b are not arranged in the region between the electrode fingers 31a and 31b in the edge region E.

[0126] The edge region E has a lower acoustic velocity than the central region C by arranging the mass adding films 36 a and 36 b .

[0127] The mass additional films 36 a and 36 b include, for example, the same conductive material as that of the plurality of electrode fingers 31 a and the plurality of electrode fingers 31 b .

[0128] Furthermore, the mass additional film 36 a may be disposed on the electrode fingers 31 a in the peripheral region E, and the mass additional film 36 b may be disposed on the electrode fingers 31 b in the peripheral region E.

[0129] The IDT electrode 30A of the series arm resonator 11A according to the present modification has a so-called 3D piston mode structure in which a mass added film is arranged in the second direction of the electrode fingers, and can suppress ripples in the transverse mode.

[0130] Furthermore, the IDT electrode 30A of the series arm resonator 11A according to the present modification is suitable for increasing the duty ratio of the IDT electrode 30A with high accuracy, compared with an IDT electrode having a so-called 2D piston structure in which the width of a part of the electrode fingers is widened in the first direction.

[0131] [4. Relationship between the cutting angle of the piezoelectric layer and the duty ratio of the IDT electrode]

[0132] Next, the cutting angle θ of the piezoelectric layer and the duty ratio D of the IDT electrode for suppressing the third harmonic excitation response of the first elastic wave resonator having a structure with a 3D piston mode are described. In addition, 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 by a plane whose normal line is an axis rotated θ° from the Y axis with the X axis as the center axis, and a single crystal or ceramic in which a surface acoustic wave propagates in the X-axis direction). The cutting angle θ shown below is θ of the above-mentioned θ°Y-cut X-propagation LiTaO3.

[0133] Table 1 shows an example of parameters of an elastic wave resonator having a 3D piston mode structure.

[0134] [Table 1]

[0135]

[0136] Figure 5A This is a graph showing the resonance characteristics of the elastic wave resonator when the duty ratio of the IDT electrode is changed. Figure 5B : is a graph showing the phase of the third harmonic excitation signal of the elastic wave resonator when the duty ratio of the IDT electrode is changed. Figure 5C : is a graph showing the relationship between the duty ratio of the IDT electrode and the phase of the third harmonic excitation signal.

[0137] Got it Figure 5A to Figure 5C The elastic wave resonator has the parameters shown in Table 1. Figure 3A to Figure 3C The construction of the 3D piston model is shown.

[0138] like Figure 5A as well as Figure 5BAs shown in the figure, when the cutting angle θ of the piezoelectric layer is generally used and is 30°, the resonance characteristics of the fundamental wave hardly change when the duty ratio D is changed to 0.525, 0.6, and 0.65, but the intensity (the impedance difference between the resonant frequency and the anti-resonant frequency) and phase of the third harmonic excitation increase as the duty ratio increases. In addition, the larger the phase of the third harmonic excitation signal (the closer to +90°), the higher the intensity of the third harmonic excitation signal, and the smaller the phase of the third harmonic excitation signal (the closer to -90°), the lower the intensity of the third harmonic excitation signal.

[0139] In addition, if Figure 5C As shown in FIG. 1 , when the cutting angle θ of the piezoelectric layer is 30°, the duty ratio D is greater than 0.5, and the phase of the third harmonic excitation signal exceeds -45°. In other words, when the cutting angle θ is 30°, the unnecessary wave of the third harmonic excitation increases as the duty ratio D increases.

[0140] However, increasing the duty ratio D of the IDT electrode is effective as a method of increasing the capacitance of the elastic wave resonator without increasing the size of the IDT electrode. In addition, by increasing the duty ratio D, the line width of the electrode finger can be ensured to be large, thereby suppressing the manufacturing variation of the IDT electrode.

[0141] From the above viewpoints, the inventors have found a combination of the duty ratio D and the cut angle θ that can suppress unnecessary waves caused by third-order harmonic excitation in a region where the duty ratio D of the IDT electrode becomes larger than 0.5.

[0142] Tables 2, 3, and 4 show the phases of the third harmonic excitation signal when the duty cycle D and the cutting angle θ are changed. Specifically, Table 2 shows the phases of the third harmonic excitation when the duty cycle D is greater than 0.5 and the cutting angle θ is 0° to 32.5°, Table 3 shows the phases of the third harmonic excitation when the duty cycle D is greater than 0.5 and the cutting angle θ is 32.5° to 67.5°, and Table 4 shows the phases of the third harmonic excitation when the duty cycle D is greater than 0.5 and the cutting angle θ is 67.5° to 92.5°.

[0143] The numerical values ​​α of the cut angles described in Tables 2 to 4 mean a range of α±2.5°. The numerical value β of the duty ratio D means a range of β-0.012 to β+0.013.

[0144] [Table 2]

[0145]

[0146] [Table 3]

[0147]

[0148] [Table 4]

[0149]

[0150] In Tables 2 to 4, in the region where the duty ratio D is greater than 0.5, the range in which the phase of the third harmonic excitation becomes smaller compared to the conventionally used (D, θ) = (0.5, 30) is

[0151] (1) 0.513≤D≤0.568 and 2.5≤θ≤17.5,

[0152] (2) 0.538≤D≤0.568 and 17.5≤θ≤22.5,

[0153] (3) 0.538≤D≤0.588 and 42.5≤θ≤52.5,

[0154] (4) 0.538≤D≤0.613 and 52.5≤θ≤67.5,

[0155] (5) 0.513 ≤ D ≤ 0.638 and 67.5 ≤ θ ≤ 77.5, and

[0156] (6) 0.513≤D≤0.713 and 77.5≤θ≤92.5 (in the bold, double, and triple lines of Tables 2 to 4).

[0157] That is, the series arm resonator 11 (first elastic wave resonator) included in the filter 10 according to the present embodiment satisfies any one of the above (1) to (6).

[0158] Thus, it is possible to provide the filter 10 having the IDT electrode of the piston mode in which the generation of the unnecessary wave of the third harmonic excitation is suppressed in the region where the duty ratio D is large, which is advantageous for miniaturization and suppression of manufacturing variation.

[0159] Furthermore, by applying the first elastic 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. Therefore, it is possible to suppress the deterioration of the pass characteristic at the above frequency of the third harmonic excitation of the filter 20 connected to the common terminal 100.

[0160] In addition, the first elastic wave resonator satisfying any one of the above (1) to (6) 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 instead of the series arm resonator 11. In this case, it is also possible to provide a filter 10 having an IDT electrode of a piston mode that suppresses the generation of unnecessary waves caused by third harmonic excitation in a region where the duty ratio D is large and is advantageous for miniaturization and suppression of manufacturing variations.

[0161] Furthermore, the series arm resonator 11 (first elastic wave resonator) included in the filter 10 according to the present embodiment preferably satisfies

[0162] (7) 0.538≤D≤0.588 and 42.5≤θ≤52.5, and

[0163] (8) Any of 0.538≤D≤0.613 and 52.5≤θ≤57.5 (in the double-line frame and triple-line frame in Table 3).

[0164] In the region where the cut angle θ is less than 30°, the crystallinity of the IDT electrode 30 and the reflective electrode 40 formed on the piezoelectric layer 51 decreases, and the power resistance decreases. In addition, in the region where the cut angle θ is greater than 60°, the Rayleigh wave response generated in the frequency region of approximately 0.75 times the fundamental wave increases. In contrast, by satisfying either of the above (7) and (8), it is possible to provide a filter 10 having an IDT electrode of a piston mode that suppresses the generation of third harmonic excitation and unnecessary Rayleigh waves while ensuring power resistance in a region where the duty ratio D is large and is advantageous for miniaturization and suppression of manufacturing variations.

[0165] Furthermore, the series arm resonator 11 (first elastic wave resonator) included in the filter 10 according to the present embodiment preferably satisfies

[0166] (7) 0.538≤D≤0.588 and 42.5≤θ≤52.5 (within the three-line box in Table 3).

[0167] In the region where the cut angle θ is less than 30°, the crystallinity of the IDT electrode 30 and the reflective electrode 40 formed on the piezoelectric layer 51 decreases, and the power resistance decreases. In addition, as the cut angle θ becomes larger than 55°, the Rayleigh wave response increases. In contrast, by satisfying the above (7), it is possible to provide a filter 10 having an IDT electrode of a piston mode that further suppresses the generation of third harmonic excitation and unnecessary Rayleigh waves while ensuring power resistance in a region where the duty ratio D is large, which is advantageous for miniaturization and suppression of manufacturing variations.

[0168] [5. Effects, etc.]

[0169] As described above, the filter 10 according to the present embodiment and the second modification example includes a first elastic wave resonator including a piezoelectric substrate 50 and an IDT electrode 30 arranged on the piezoelectric substrate 50, the piezoelectric substrate 50 including a piezoelectric layer 51 including lithium tantalate and having an IDT electrode 30 formed thereon, a high acoustic velocity layer 53 in which a body wave propagates at a higher acoustic velocity than an elastic wave propagating in 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 in which a body wave propagates at a lower acoustic velocity than a body wave propagating in the piezoelectric layer 51, the IDT electrode 30 including a plurality of electrode fingers 31a and a plurality of electrode fingers 31b arranged in parallel with each other, a bus bar electrode 32a configured to connect one ends of the plurality of electrode fingers 31a to each other, and a bus bar electrode 32a configured to connect one ends of the plurality of electrode fingers 31b to each other and to sandwich the plurality of electrode fingers 31a and the plurality of electrode fingers 31b. The bus bar electrode 32b is arranged opposite to the bus bar electrode 32a. When the area where the plurality of electrode fingers 31a and the plurality of electrode fingers 31b overlap each other when viewed from a first direction parallel to the piezoelectric layer 51 and perpendicular to the extending direction of the electrode fingers 31a and 31b is set as an intersection area W, the intersection area W has a central area C located in the center of the above-mentioned extending direction, and edge areas E located on both outer sides of the central area C in the above-mentioned extending direction and having a sound velocity lower than the sound velocity in the central area C. The IDT electrode 30 further has mass addition films 35a and 35b (36a and 36b) in a second direction perpendicular to the main surface of the piezoelectric layer 51 of at least one of the plurality of electrode fingers 31a and the plurality of electrode fingers 31b arranged in the edge area E. When the duty ratio of the IDT electrode 30 is set to D and the cutting angle of the piezoelectric layer 51 is set to θ°, it satisfies

[0170] (1) 0.513≤D≤0.568 and 2.5≤θ≤17.5,

[0171] (2) 0.538≤D≤0.568 and 17.5≤θ≤22.5,

[0172] (3) 0.538≤D≤0.588 and 42.5≤θ≤52.5,

[0173] (4) 0.538≤D≤0.613 and 52.5≤θ≤67.5,

[0174] (5) 0.513 ≤ D ≤ 0.638 and 67.5 ≤ θ ≤ 77.5, and

[0175] (6) Any one of 0.513≤D≤0.713 and 77.5≤θ≤92.5.

[0176] Thus, it is possible to provide the filter 10 having the IDT electrode 30 of the piston mode in which the generation of unnecessary waves due to third-order harmonic excitation is suppressed in a region where the duty ratio D is large, which is advantageous for miniaturization and suppression of manufacturing variations.

[0177] For another example, in the filter 10 , either (1) 0.538≤D≤0.588 and 42.5≤θ≤52.5 and (2) 0.538≤D≤0.613 and 52.5≤θ≤57.5 are satisfied.

[0178] Thus, the filter 10 having the IDT electrode of the piston mode which suppresses the generation of the third harmonic excitation and the unnecessary wave of the Rayleigh wave while ensuring the power handling performance in the large duty ratio D region which is advantageous for miniaturization and suppression of manufacturing variation can be provided.

[0179] For another example, in the filter 10, 0.538≤D≤0.588 and 42.5≤θ≤52.5 are satisfied.

[0180] Thus, in the filter 10 , it is possible to provide a filter 10 having a piston mode IDT electrode that further suppresses the generation of third harmonic excitation and unnecessary Rayleigh waves while ensuring power handling performance in a large duty ratio D region that is advantageous for miniaturization and suppression of manufacturing variations.

[0181] For another example, in the filter 10 , the mass addition films 35 a and 35 b are arranged in the edge region E in the second direction on the electrode fingers 31 a , the electrode fingers 31 b , and the region between the electrode fingers 31 a and the electrode fingers 31 b .

[0182] Thus, the mass adding films 35 a and 35 b can be continuously formed in the edge region E over the plurality of electrode fingers, respectively, and thus the formation accuracy of the mass adding films 35 a and 35 b can be improved.

[0183] As another example, in the filter 10 , the mass added films 35 a and 35 b include tantalum oxide.

[0184] Thus, even if the mass addition films 35 a and 35 b are formed in the region between the electrode fingers 31 a and 31 b , it is possible to suppress the ripples in the transverse mode without deteriorating the resonance characteristics of the first elastic wave resonator.

[0185] For another example, in the filter 10, the mass addition films 36a and 36b are arranged in the second direction of only at least one of the multiple electrode fingers 31a and the multiple electrode fingers 31b in the edge area E, and the mass addition films 36a and 36b include the same conductive material as the multiple electrode fingers 31a and the multiple electrode fingers 31b.

[0186] Thus, the mass addition films 36 a and 36 b can be formed by the same process as that of the electrode fingers 31 a and 31 b , respectively, so that the ripples in the transverse mode can be suppressed while simplifying the manufacturing process.

[0187] For another example, in the filter 10 , the duty ratio D of the IDT electrode 30 is a value obtained by averaging the duty ratios of the plurality of electrode fingers 31 a and the plurality of electrode fingers 31 b .

[0188] Thus, even when the duty ratios of the plurality of electrode fingers 31 a and the plurality of electrode fingers 31 b are different, the duty ratio D of the IDT electrode 30 can be specified.

[0189] For another example, the filter 10 includes terminals 111 and 112, and a plurality of elastic wave resonators including a first elastic wave resonator, the plurality of elastic wave resonators including series arm resonators 11 to 14 arranged in series in a path connecting the terminals 111 and 112, and parallel arm resonators 15 to 18 connected between the path and ground.

[0190] Thus, in the ladder-type filter 10 , it is possible to suppress unnecessary waves caused by third-order harmonic excitation.

[0191] For another example, a filter 10A according to Modification 1 includes a plurality of elastic wave resonators including a first elastic wave resonator, and the plurality of elastic wave resonators include a longitudinally coupled resonator.

[0192] Thus, in the filter 10A including the longitudinally coupled resonator, it is possible to suppress unnecessary waves caused by third-order harmonic excitation.

[0193] As another example, the multiplexer 1 according to the present embodiment includes the common terminal 100 , the filter 10 or 10A connected to the common terminal 100 , and the filter 20 connected to the common terminal 100 .

[0194] Thus, it is possible to provide the multiplexer 1 in which the unnecessary waves caused by the third harmonic excitation generated in the filter 10 are suppressed.

[0195] For another example, in the multiplexer 1 , the filter 10 or 10A includes a plurality of elastic wave resonators including a first elastic wave resonator, and the first elastic wave resonator is connected closest to the common terminal 100 among the plurality of elastic wave resonators.

[0196] This can effectively reduce the reflection loss at the frequency of the third harmonic excitation when the filter 10 or 10A is viewed from the common terminal 100. Therefore, it is possible to suppress the deterioration of the transmission characteristic of the filter 20 connected to the common terminal 100 at the frequency of the third harmonic excitation.

[0197] For another example, in the multiplexer 1 , the passband of the filter 20 is located on the high frequency side compared to the passband of the filter 10 .

[0198] Thus, even if the unnecessary waves of the third harmonic excitation generated by the filter 10 are included in the vicinity of the passband of the filter 20 , it is possible to suppress the deterioration of the passband characteristics of the filter 20 .

[0199] (Other Embodiments)

[0200] The elastic wave device and multiplexer according to the present invention are described above by listing the embodiments and variations, but the present invention is not limited to the above embodiments and variations. Variations obtained by implementing various modifications that a person skilled in the art can think of to the above embodiments and variations without departing from the main purpose of the present invention, and various devices incorporating the elastic wave device and multiplexer according to the present invention are also included in the present invention.

[0201] For another example, in the elastic 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 components.

[0202] The resonant frequency and antiresonant frequency described in the above-described embodiment and modified examples are derived by, for example, bringing an RF probe into contact with two input and output electrodes of an elastic wave resonator and measuring reflection characteristics.

[0203] Features of the elastic wave device and the multiplexer described based on the above-mentioned embodiment and modified examples are described below.

[0204] <1>

[0205] An elastic wave device comprises: a first elastic wave resonator having a substrate and an IDT electrode arranged on the substrate,

[0206] The substrate has:

[0207] A piezoelectric layer, formed with the IDT electrode, comprising lithium tantalate;

[0208] a high sound velocity layer in which a body wave propagates at a higher sound velocity than an elastic wave propagating in the piezoelectric layer; and

[0209] The low acoustic velocity layer is disposed between the piezoelectric layer and the high acoustic velocity layer, and the acoustic velocity of the body wave is lower than that of the body wave propagating in the piezoelectric layer.

[0210] The IDT electrode has:

[0211] a plurality of first electrode fingers and a plurality of second electrode fingers arranged in parallel with each other;

[0212] a first bus bar electrode configured to connect one ends of the plurality of first electrode fingers to each other; and

[0213] a second bus bar electrode configured to connect one ends of the plurality of second electrode fingers to each other and arranged to face the first bus bar electrode with the plurality of first electrode fingers and the plurality of second electrode fingers interposed therebetween;

[0214] When a region where the plurality of first electrode fingers and the plurality of second electrode fingers overlap each other when viewed from a first direction parallel to the piezoelectric layer and orthogonal to the extending direction of the first electrode finger and the second electrode finger is set as an intersection region, the intersection region includes a central region located in the center of the extending direction, and edge regions located on both outer sides of the central region in the extending direction and having a sound velocity lower than that in the central region.

[0215] The IDT electrode also has:

[0216] a mass addition film arranged in the edge region in a second direction perpendicular to the main surface of the piezoelectric layer on at least one of the plurality of first electrode fingers and the plurality of second electrode fingers;

[0217] When the duty ratio of the IDT electrode is set to D and the cutting angle of the piezoelectric layer is set to θ°,

[0218] (1) 0.513≤D≤0.568 and 2.5≤θ≤17.5,

[0219] (2) 0.538≤D≤0.568 and 17.5≤θ≤22.5,

[0220] (3) 0.538≤D≤0.588 and 42.5≤θ≤52.5,

[0221] (4) 0.538≤D≤0.613 and 52.5≤θ≤67.5,

[0222] (5) 0.513 ≤ D ≤ 0.638 and 67.5 ≤ θ ≤ 77.5, and

[0223] (6) Any one of 0.513≤D≤0.713 and 77.5≤θ≤92.5.

[0224] <2>

[0225] The elastic wave device according to <1>, wherein

[0226] (1) 0.538≤D≤0.588 and 42.5≤θ≤52.5, and

[0227] (2) Any one of 0.538≤D≤0.613 and 52.5≤θ≤57.5.

[0228] <3>

[0229] The elastic wave device according to <2>, wherein:

[0230] 0.538≤D≤0.588 and 42.5≤θ≤52.5 are satisfied.

[0231] <4>

[0232] The elastic wave device according to any one of <1> to <3>,

[0233] The mass additional film is arranged in the second direction on 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.

[0234] <5>

[0235] The elastic wave device according to <4>, wherein:

[0236] The mass-adding film includes tantalum oxide.

[0237] <6>

[0238] The elastic wave device according to any one of <1> to <3>,

[0239] The mass additional film is arranged in the second direction of only at least one of the plurality of first electrode fingers and the plurality of second electrode fingers in the edge region.

[0240] The mass additional film includes the same conductive material as that of the plurality of first electrode fingers and the plurality of second electrode fingers.

[0241] <7>

[0242] The elastic wave device according to any one of <1> to <6>, wherein

[0243] The duty ratio D of the IDT electrode is a value obtained by averaging the duty ratios of the plurality of first electrode fingers and the plurality of second electrode fingers.

[0244] <8>

[0245] The elastic wave device according to any one of <1> to <7>,

[0246] The elastic wave device comprises:

[0247] a first input / output terminal and a second input / output terminal; and

[0248] a plurality of elastic wave resonators, including the first elastic wave resonator,

[0249] The plurality of elastic wave resonators include:

[0250] a series arm resonator arranged in series on a path connecting the first input / output terminal and the second input / output terminal; and

[0251] The parallel arm resonator is connected between the path and the ground.

[0252] <9>

[0253] The elastic wave device according to any one of <1> to <7>,

[0254] The elastic wave device includes a plurality of elastic wave resonators including the first elastic wave resonator.

[0255] The plurality of elastic wave resonators include longitudinally coupled resonators.

[0256] <10>

[0257] A multiplexer having:

[0258] Common terminal;

[0259] The elastic wave device according to any one of <1> to <9>, connected to the common terminal; and

[0260] A filter is connected to the common terminal.

[0261] <11>

[0262] The multiplexer according to <10>, wherein:

[0263] The elastic wave device includes a plurality of elastic wave resonators including the first elastic wave resonator.

[0264] The first elastic wave resonator is connected closest to the common terminal among the plurality of elastic wave resonators.

[0265] <12>

[0266] The multiplexer according to <10> or <11>, wherein:

[0267] The passband of the filter is located on the high-frequency side relative to the elastic wave device.

[0268] Industrial Applicability

[0269] The present invention can be widely used as a transceiver filter and a multiplexer used in the front end of a wireless communication terminal that is required to have low loss within a passband and high attenuation outside the passband.

Claims

1. An elastic wave device comprising: a first elastic wave resonator having a substrate and an interdigital transducer (IDT) electrode arranged on the substrate; The substrate has: A piezoelectric layer, formed with the IDT electrode, comprising lithium tantalate; a high sound velocity layer in which a body wave propagates at a higher sound velocity than an elastic wave propagating in the piezoelectric layer; and The low acoustic velocity layer is disposed between the piezoelectric layer and the high acoustic velocity layer, and the acoustic velocity of the body wave is lower than that of the body wave propagating in the piezoelectric layer. The IDT electrode has: a plurality of first electrode fingers and a plurality of second electrode fingers arranged in parallel with each other; a first bus bar electrode configured to connect one ends of the plurality of first electrode fingers to each other; and a second bus bar electrode configured to connect one ends of the plurality of second electrode fingers to each other and arranged to face the first bus bar electrode with the plurality of first electrode fingers and the plurality of 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 when viewed from a first direction parallel to the piezoelectric layer and orthogonal to the extension direction of the first electrode finger and the second electrode finger is set as an intersection region, the intersection region includes a central region located in the center of the extension direction, and edge regions located on both outer sides of the central region in the extension direction and having a sound velocity lower than that in the central region. The IDT electrode also has: a mass addition film arranged in the edge region in a second direction perpendicular to the main surface of the piezoelectric layer on at least one of the plurality of first electrode fingers and the plurality of second electrode fingers; When the duty ratio of the IDT electrode is set to D and the cutting angle of the piezoelectric layer is set to 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.

2. The elastic wave device according to claim 1, wherein: satisfy (1) 0.538≤D≤0.588 and 42.5≤θ≤52.5, and (2) Any one of 0.538≤D≤0.613 and 52.5≤θ≤57.

5.

3. The elastic wave device according to claim 2, wherein: 0.538≤D≤0.588 and 42.5≤θ≤52.5 are satisfied.

4. The elastic wave device according to any one of claims 1 to 3, wherein: The mass additional film is arranged in the second direction on 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.

5. The elastic wave device according to claim 4, wherein: The mass-adding film includes tantalum oxide.

6. The elastic wave device according to any one of claims 1 to 3, wherein: The mass additional film is arranged in the second direction of only at least one of the plurality of first electrode fingers and the plurality of second electrode fingers in the edge region. The mass additional film includes the same conductive material as that of the plurality of first electrode fingers and the plurality of second electrode fingers.

7. The elastic wave device according to any one of claims 1 to 6, wherein: The duty ratio D of the IDT electrode is a value obtained by averaging the duty ratios of the plurality of first electrode fingers and the plurality of second electrode fingers.

8. The elastic wave device according to any one of claims 1 to 7, wherein: The elastic wave device comprises: a first input / output terminal and a second input / output terminal; and a plurality of elastic wave resonators, including the first elastic 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; and The parallel arm resonator is connected between the path and the ground.

9. The elastic wave device according to any one of claims 1 to 7, wherein: The elastic wave device includes a plurality of elastic wave resonators including the first elastic wave resonator. The plurality of elastic wave resonators include longitudinally coupled resonators.

10. A multiplexer comprising: Common terminal; The elastic wave device according to any one of claims 1 to 9, connected to the common terminal; and A filter is connected to the common terminal.

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

12. The multiplexer according to claim 10 or 11, wherein: The passband of the filter is located on the high-frequency side relative to the elastic wave device.

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