Elastic wave device

Abstract

An elastic wave filter (1) has a parallel arm resonator (22) connected between a series arm path connecting input and output terminals (110 and 120) and a ground, a parallel arm resonator (25) connected between the series arm path and the ground, a series arm resonator (12) arranged in series in the series arm path, a capacitor (32) connected in parallel with the parallel arm resonator (22), and a capacitor (35) connected in parallel with the parallel arm resonator (25), the parallel arm resonators (22 and 25) and the series arm resonator (12) each include an IDT electrode formed in a substrate having piezoelectricity, the capacitors (32 and 35) each include a pair of comb electrodes formed in a substrate having piezoelectricity, the extending direction of the electrode fingers of the IDT electrode intersects the extending direction of the electrode fingers of the pair of comb electrodes, and the anti-resonance frequency (fa32) of the capacitor (32) is different from the anti-resonance frequency (fa35) of the capacitor (35).

Description

Technical Field

[0001] This invention relates to elastic wave devices. Background Technology

[0002] Patent Document 1 discloses an elastic wave device comprising a series arm resonator disposed in a series arm path connecting two signal terminals, a parallel arm resonator connected between the series arm path and a first reference electrode, and a capacitor element connected between the series arm path and a second reference electrode. According to the above structure, an elastic wave device with low insertion loss and high attenuation in the high-frequency region can be provided.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-243570 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, in the elastic wave device described in Patent Document 1, depending on the structure of the piezoelectric substrate or the elastic wave mode used, sometimes higher-order modes caused by the aforementioned capacitor element are generated in the frequency band that is higher than the passband, which deteriorates the attenuation characteristics.

[0008] Therefore, the present invention was made to solve the above-mentioned problems, and its object is to provide an elastic wave device with improved attenuation characteristics.

[0009] Methods for solving problems

[0010] To achieve the above objectives, one aspect of the elastic wave device according to the present invention includes: a first elastic wave resonator connected between a series arm path connecting a first input / output terminal and a second input / output terminal and ground; a second elastic wave resonator connected between the series arm path and ground; a third elastic wave resonator connected in series in the series arm path; a first capacitor element connected in parallel with the first elastic wave resonator; and a second capacitor element connected in parallel with the second elastic wave resonator. The first, second, and third elastic wave resonators are respectively included in an IDT (Inter-Digital Transmission Device) formed on a piezoelectric substrate. The interdigitated transducer (IDT) electrode, the first capacitor element, and the second capacitor element each include a pair of comb-shaped electrodes formed on a substrate. The IDT electrode has: a plurality of first electrode fingers arranged in parallel with each other; and a set of first busbar electrodes arranged opposite each other sandwiching the plurality of first electrode fingers. The pair of comb-shaped electrodes has: a plurality of second electrode fingers arranged in parallel with each other; and a set of second busbar electrodes arranged opposite each other sandwiching the plurality of second electrode fingers. The extension directions of the plurality of first electrode fingers intersect the extension directions of the plurality of second electrode fingers. The anti-resonant frequency of the first capacitor element is different from the anti-resonant frequency of the second capacitor element.

[0011] Furthermore, one aspect of the elastic wave device according to the present invention includes: a first elastic wave resonator, which is connected in series in a series arm path connecting a first input / output terminal and a second input / output terminal; a second elastic wave resonator, which is connected in series in the series arm path; a third elastic wave resonator, which is connected between the series arm path and ground; a first capacitor element, which is connected in parallel with the first elastic wave resonator; and a second capacitor element, which is connected in parallel with the second elastic wave resonator. The first elastic wave resonator, the second elastic wave resonator, and the third elastic wave resonator are respectively included in a piezoelectric... The IDT electrode formed on the substrate includes a pair of comb-shaped electrodes formed on the substrate. The IDT electrode has a plurality of first electrode fingers arranged in parallel with each other and a set of first busbar electrodes arranged opposite each other, sandwiching the plurality of first electrode fingers. The pair of comb-shaped electrodes has a plurality of second electrode fingers arranged in parallel with each other and a set of second busbar electrodes arranged opposite each other, sandwiching the plurality of second electrode fingers. The extension directions of the plurality of first electrode fingers intersect the extension directions of the plurality of second electrode fingers. The resonant frequency of the first capacitor element is different from the resonant frequency of the second capacitor element.

[0012] Furthermore, one aspect of the elastic wave device according to the present invention includes: a first elastic wave resonator, which is connected in series in a series arm path connecting a first input / output terminal and a second input / output terminal; a second elastic wave resonator, which is connected between the series arm path and ground; a third elastic wave resonator, which is connected in series in the series arm path or connected between the series arm path and ground; a first capacitor element, which is connected in parallel with the first elastic wave resonator; and a second capacitor element, which is connected in parallel with the second elastic wave resonator. The first elastic wave resonator, the second elastic wave resonator, and the third elastic wave resonator are respectively included in an ID formed on a piezoelectric substrate. The IDT electrode, the first capacitor element, and the second capacitor element each include a pair of comb-shaped electrodes formed on the substrate. The IDT electrode has: a plurality of first electrode fingers arranged in parallel with each other; and a set of first busbar electrodes arranged opposite each other sandwiching the plurality of first electrode fingers. The pair of comb-shaped electrodes has: a plurality of second electrode fingers arranged in parallel with each other; and a set of second busbar electrodes arranged opposite each other sandwiching the plurality of second electrode fingers. The extension directions of the plurality of first electrode fingers intersect the extension directions of the plurality of second electrode fingers. The anti-resonant frequency of the second capacitor element is smaller than the resonant frequency of the first capacitor element, or the anti-resonant frequency of the second capacitor element is larger than the anti-resonant frequency of the first capacitor element.

[0013] Additionally, one aspect of the present invention relates to an elastic wave device comprising: a first elastic wave resonator, a second elastic wave resonator, and a third elastic wave resonator; a first capacitor element connected in parallel with the first elastic wave resonator; and a second capacitor element connected in parallel with the second elastic wave resonator. The first and second elastic wave resonators are connected in series in a series arm path connecting the first and second input / output terminals, and the third elastic wave resonator is connected between the series arm path and ground. Alternatively, the first and second elastic wave resonators are connected between the series arm path and ground, and the third elastic wave resonator is connected in series in the series arm path. The first elastic wave resonator, the second elastic wave resonator, and the third elastic wave resonator each include an IDT electrode formed on a piezoelectric substrate. The first capacitor element and the second capacitor element each include a pair of comb-shaped electrodes formed on the substrate. The IDT electrode has: a plurality of first electrode fingers arranged in parallel with each other; and a set of first busbar electrodes arranged opposite each other sandwiching the plurality of first electrode fingers. The pair of comb-shaped electrodes has: a plurality of second electrode fingers arranged in parallel with each other; and a set of second busbar electrodes arranged opposite each other sandwiching the plurality of second electrode fingers. The extension directions of the plurality of first electrode fingers intersect the extension directions of the plurality of second electrode fingers. The electrode finger spacing of the first capacitor element is different from the electrode finger spacing of the second capacitor element.

[0014] Additionally, one embodiment of the present invention relates to an elastic wave device comprising: a first elastic wave resonator, a second elastic wave resonator, and a third elastic wave resonator; a first capacitor element connected in parallel with the first elastic wave resonator; and a second capacitor element connected in parallel with the second elastic wave resonator. The first and second elastic wave resonators are connected in series in a series arm path connecting the first and second input / output terminals, and the third elastic wave resonator is connected between the series arm path and ground. Alternatively, the first and second elastic wave resonators are connected in series between the series arm path and ground, and the third elastic wave resonator is connected in series in the series arm path. The first elastic wave resonator, the second elastic wave resonator, and the third elastic wave resonator each include an IDT electrode formed on a piezoelectric substrate. The first capacitor element and the second capacitor element each include a pair of comb-shaped electrodes formed on the substrate. The IDT electrode has: a plurality of first electrode fingers arranged in parallel with each other; and a set of first busbar electrodes arranged opposite each other sandwiching the plurality of first electrode fingers. The pair of comb-shaped electrodes has: a plurality of second electrode fingers arranged in parallel with each other; and a set of second busbar electrodes arranged opposite each other sandwiching the plurality of second electrode fingers. The extension directions of the plurality of first electrode fingers intersect the extension directions of the plurality of second electrode fingers. The duty cycle of the electrode fingers of the first capacitor element is different from the duty cycle of the electrode fingers of the second capacitor element.

[0015] Invention Effects

[0016] According to the present invention, it is possible to provide an elastic wave device with improved attenuation characteristics. Attached Figure Description

[0017] Figure 1 This is a circuit diagram of the elastic wave filter involved in the implementation method.

[0018] Figure 2A These are schematic top and cross-sectional views illustrating a first example of an elastic wave resonator constituting an elastic wave filter according to an embodiment.

[0019] Figure 2B This is a cross-sectional view schematically illustrating a second example of an elastic wave resonator constituting the elastic wave filter according to the embodiment.

[0020] Figure 3 This is a top view showing the electrode configuration of the elastic wave resonator and capacitor element involved in the embodiment.

[0021] Figure 4A This is a graph showing the impedance characteristics of the capacitive elements of the elastic wave filter involved in the embodiment.

[0022] Figure 4B This is a diagram showing the relationship between the resonant characteristics of the two capacitive elements in the elastic wave filter involved in the embodiment.

[0023] Figure 4C This is a graph showing the transmission characteristics of the elastic wave filters involved in the embodiments and comparative examples.

[0024] Figure 5A This is a circuit diagram of the elastic wave filter involved in the modified example 1 of the implementation method.

[0025] Figure 5B This is a diagram showing the relationship between the resonant characteristics of the two capacitive elements of the elastic wave filter according to the modified example 1 of the embodiment.

[0026] Figure 6A This is a circuit diagram of the elastic wave filter involved in variation 2 of the implementation method.

[0027] Figure 6B This is a diagram showing the relationship between the resonant characteristics of the two capacitive elements in the elastic wave filter according to the modified example 2 of the embodiment. Detailed Implementation

[0028] Hereinafter, embodiments of the present disclosure will be described in detail with the aid of accompanying drawings. Furthermore, the embodiments described below are either general or specific examples. The numerical values, shapes, materials, constituent elements, arrangements of constituent elements, and connection methods shown in the following embodiments are examples and are not intended to limit the present invention.

[0029] Furthermore, the figures are schematic diagrams that have been appropriately emphasized, omitted, or scaled for the purpose of illustrating the invention, and are not necessarily strictly illustrative. Sometimes they differ from the actual shapes, positional relationships, and proportions. In the figures, substantially identical structures are labeled with the same reference numerals, and sometimes repeated descriptions are omitted or simplified.

[0030] In the circuit structure disclosed herein, "connected between A and B" means connected to both A and B. It also includes cases where there is an indirect connection with A and B.

[0031] In addition, in the component configuration disclosed herein, "component A is configured in series in path B" means that both the signal input terminal and the signal output terminal of component A are connected to the wiring, electrodes or terminals constituting path B.

[0032] In addition, terms such as "parallel" and "perpendicular" indicate the relationship between elements, terms such as "rectangle" indicate the shape of elements, and numerical ranges not only have a strict meaning, but also include substantially equivalent ranges, such as a few percent of error.

[0033] Furthermore, in this disclosure, "terminal" refers to the point where a conductor within an element terminates. Additionally, when the impedance of the conductors between elements is sufficiently low, a terminal is not merely a single point, but can be interpreted as any point on the conductors between elements or the entire conductor.

[0034] In addition, in the disclosure, "input / output terminal" is a terminal that has the function of at least one of an input terminal and an output terminal.

[0035] Furthermore, in this disclosure, the passband of the elastic wave device or filter is defined as the frequency band between two frequencies that are 3 dB greater than the minimum insertion loss within that passband.

[0036] Furthermore, the resonant frequency and anti-resonant frequency shown in the above embodiments and variations are derived, for example, by contacting the two input and output electrodes of the elastic wave resonator or capacitor element with the RF probe when the elastic wave resonator or capacitor element is not connected to other circuit elements, and then measuring the reflection characteristics (impedance characteristics) using a network analyzer or the like.

[0037] Furthermore, "two different resonant frequencies" and "two different anti-resonant frequencies" are defined as a difference of 0.1% or more between the two measured resonant frequencies (or two anti-resonant frequencies). This difference includes the error of the measuring device. Additionally, "one resonant frequency is larger than one anti-resonant frequency" and "one resonant frequency is smaller than one anti-resonant frequency" are defined as a difference of 0.1% or more between a measured resonant frequency and a measured anti-resonant frequency. This difference includes the error of the measuring device.

[0038] Furthermore, in this disclosure, "frequency band" refers to at least one of the uplink and downlink operating frequency bands of a frequency band predefined by standardization organizations such as 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 can be, for example, an LTE (Long Term Evolution) system, a 5G (5th Generation)-NR (New Radio) system, and a WLAN (Wireless Local Area Network) system, but is not limited to these. Furthermore, the uplink operating frequency band of a frequency band refers to the frequency range designated for uplink use within that frequency band. Similarly, the downlink operating frequency band of a frequency band refers to the frequency range designated for downlink use within that frequency band.

[0039] (Implementation Method)

[0040] [1 Circuit structure of elastic wave filter 1]

[0041] Figure 1 This is a circuit diagram of the elastic wave filter 1 according to the embodiment. As shown in the figure, the elastic wave filter 1 is an example of an elastic wave device, which includes series arm resonators 11, 12, 13, 14 and 15, parallel arm resonators 21, 22, 23, 24, 25 and 26, capacitors 32 and 35, and input and output terminals 110 and 120.

[0042] The series arm resonators 11-15 each include an elastic wave resonator, arranged in series in the series arm path that connects the input / output terminal 110 (first input / output terminal) and the input / output terminal 120 (second input / output terminal). The series arm resonators 11-15 are examples of a third elastic wave resonator, connected sequentially from the input / output terminal 110 in the order of series arm resonators 11, 12, 13, 14, and 15. Furthermore, at least one of the series arm resonators 11-15 may not be included in the elastic wave filter 1.

[0043] Parallel arm resonators 21-26 each include an elastic wave resonator, connected between the aforementioned series arm path and ground. Parallel arm resonator 21 is connected between the connection point of input / output terminal 110 and series arm resonator 11 and ground. Parallel arm resonator 22 is an example of a first elastic wave resonator, connected between the connection point of series arm resonators 11 and 12 and ground. Parallel arm resonator 23 is connected between the connection point of series arm resonators 12 and 13 and ground. Parallel arm resonator 24 is connected between the connection point of series arm resonators 13 and 14 and ground. Parallel arm resonator 25 is an example of a second elastic wave resonator, connected between the connection point of series arm resonators 14 and 15 and ground. Parallel arm resonator 26 is connected between the connection point of series arm resonator 15 and input / output terminal 120 and ground. Furthermore, at least one of parallel arm resonators 21, 23, 24, and 26 may not be included in the elastic wave filter 1.

[0044] The series arm resonators 11-15 and the parallel arm resonators 21-26 each include an IDT electrode formed on a piezoelectric substrate.

[0045] Capacitor 32 is an example of a first capacitive element, connected in parallel with the parallel arm resonator 22. Specifically, one end of capacitor 32 is connected to the connection node n1 of the series arm resonators 11, 12, and 22, and the other end of capacitor 32 is connected to the connection node n2 between the parallel arm resonator 22 and ground. Capacitor 32 is a so-called bridging capacitor connected in parallel with the parallel arm resonator 22.

[0046] Capacitor 35 is an example of a second capacitive element, connected in parallel with the parallel arm resonator 25. Specifically, one end of capacitor 35 is connected to the connection node n3 of the series arm resonators 14, 15, and 25, and the other end of capacitor 35 is connected to the connection node n4 between the parallel arm resonator 25 and ground. Capacitor 35 is a so-called bridging capacitor connected in parallel with the parallel arm resonator 25.

[0047] Capacitors 32 and 35 each include a pair of comb-shaped electrodes formed on a piezoelectric substrate, and resonate with the substrate. Thus, capacitors 32 and 35 respectively have a resonant frequency with extremely low impedance and an anti-resonant frequency with extremely high impedance.

[0048] Here, the anti-resonance frequency fa32 of capacitor 32 is different from the anti-resonance frequency fa35 of capacitor 35.

[0049] Therefore, in the attenuation band of the elastic wave filter 1 at a higher frequency than the passband, the spurious higher-order modes caused by capacitors 32 and 35 can be suppressed. Thus, the elastic wave filter 1 with improved attenuation characteristics at a higher frequency than the passband can be provided.

[0050] Furthermore, in this embodiment, "the anti-resonance frequency of the first capacitor element is different from the anti-resonance frequency of the second capacitor element" means that the first-order anti-resonance frequency of the first capacitor element is different from the aforementioned first-order anti-resonance frequency of the second capacitor element. That is, the order of the anti-resonance frequency of the first capacitor element being compared is the same as the order of the anti-resonance frequency of the second capacitor element.

[0051] Furthermore, by measuring the material, film thickness, and dimensions of the elastic wave harmonic oscillator and performing analytical analysis using the finite element method, it is possible to determine whether the anti-resonance frequency is a higher-order mode and its order.

[0052] Furthermore, capacitor 32 may not be connected in parallel with parallel arm resonator 22, or it may be connected in parallel with any one of parallel arm resonators 21, 23, 24, and 26. Similarly, capacitor 35 may not be connected in parallel with parallel arm resonator 25, or it may be connected in parallel with any one of parallel arm resonators 21, 23, 24, and 26.

[0053] Furthermore, in this embodiment, no capacitors are connected in parallel to the series arm resonators 11 to 15.

[0054] In addition, the number of series arm resonators in the elastic wave filter 1 can be 6 or more, and the number of parallel arm resonators can be 7 or more.

[0055] Alternatively, longitudinally coupled resonators, inductors, capacitors, and switches can be connected between the series arm resonators 11-15, the parallel arm resonators 21-26, the ground, and the input / output terminals 110 and 120. Furthermore, the inductor may also include a wiring inductor formed by wiring connecting the various components, wiring within the package, and vias.

[0056] The following section provides a detailed explanation of the construction and resonant characteristics of the elastic wave filter 1.

[0057] [2 Construction of elastic wave resonator and capacitor element]

[0058] Next, the construction of the elastic wave resonator (series arm resonator and parallel arm resonator) and capacitor element constituting the elastic wave filter 1 will be illustrated.

[0059] Figure 2A These are schematic top and cross-sectional views illustrating a first example of the elastic wave resonator constituting the elastic wave filter 1 according to the embodiment. The basic structure of the elastic wave resonator constituting the elastic wave filter 1 is illustrated in these figures. Furthermore, Figure 2AThe elastic wave resonator 60 shown is used to illustrate the typical structure of the surface acoustic wave (SAW) resonator constituting the elastic wave filter 1. The number and length of the electrode fingers constituting the electrodes are not limited thereto.

[0060] The elastic wave resonator 60 is composed of a piezoelectric substrate 50 and comb-shaped electrodes 60a and 60b.

[0061] like Figure 2A As shown in (a), a pair of opposing comb-shaped electrodes 60a and 60b are formed on the piezoelectric substrate 50. The comb-shaped electrode 60a is composed of multiple parallel electrode fingers 61a (first electrode fingers) and a busbar electrode 62a (first busbar electrode) connecting the multiple electrode fingers 61a. Similarly, the comb-shaped electrode 60b is composed of multiple parallel electrode fingers 61b (first electrode fingers) and a busbar electrode 62b (first busbar electrode) connecting the multiple electrode fingers 61b. When the elastic wave resonator 60 is a series-arm resonator 11-15 or a parallel-arm resonator 21-26, the multiple electrode fingers 61a and 61b are formed along a direction orthogonal to the elastic wave propagation direction (X-axis direction).

[0062] like Figure 2A As shown in (c), the elastic wave resonator in this example has an IDT electrode 54, a protective layer 55, and a piezoelectric substrate 50.

[0063] The IDT electrode 54, consisting of multiple electrode fingers 61a and 61b and bus bar electrodes 62a and 62b, is as follows: Figure 2A As shown in (b), it forms a stacked structure of close-fitting layer 540 and main electrode layer 542.

[0064] The bonding layer 540 is used to improve the adhesion between the piezoelectric substrate 50 and the main electrode layer 542, and is made of materials such as Ti. The main electrode layer 542 is made of Al containing 1% Cu, for example.

[0065] The protective layer 55 is formed to cover the IDT electrode 54. The protective layer 55 is a layer for the purpose of protecting the main electrode layer 542 from damage by the external environment, improving frequency temperature characteristics, and improving moisture resistance, and is, for example, a dielectric film with silicon dioxide as the main component.

[0066] Furthermore, the materials constituting the bonding layer 540, the main electrode layer 542, and the protective layer 55 are not limited to the materials described above. Also, the IDT electrode 54 may not be of the aforementioned multilayer structure. For example, the IDT electrode 54 may be made of metals or alloys such as Ti, Al, Cu, Pt, Au, Ag, and Pd. Alternatively, it may be composed of multiple laminates made of the aforementioned metals or alloys. Furthermore, the protective layer 55 may not be formed.

[0067] Next, the stacked structure of the piezoelectric substrate 50 will be described.

[0068] like Figure 2A As shown in (c), the piezoelectric substrate 50 includes a high-velocity support substrate 51, a low-velocity layer 52, and a piezoelectric layer 53, and has a structure in which the high-velocity support substrate 51, the low-velocity layer 52, and the piezoelectric layer 53 are stacked sequentially.

[0069] The piezoelectric layer 53 may include, for example, an θ° Y-cut LiTaO3 piezoelectric single crystal or piezoelectric ceramic (a lithium tantalate single crystal or ceramic obtained by cutting a plane with the X-axis rotated θ° from the Y-axis as the normal, and which is a single crystal or ceramic in which surface acoustic waves propagate along the X-axis). Furthermore, the material of the piezoelectric single crystal used as the piezoelectric layer 53 and the cutting angle θ are appropriately selected according to the requirements of each filter.

[0070] The high-velocity acoustic wave support substrate 51 is a substrate that supports the low-velocity acoustic wave layer 52, the piezoelectric layer 53, and the IDT electrode 54. The high-velocity acoustic wave support substrate 51 is also a substrate where the velocity of the bulk waves propagating in the high-velocity acoustic wave support substrate 51 is higher than that of elastic waves such as surface waves and boundary waves propagating in the piezoelectric layer 53, and functions as follows: it seals the surface acoustic waves into the portion where the piezoelectric layer 53 and the low-velocity acoustic wave layer 52 are stacked, preventing leakage to a position lower than the high-velocity acoustic wave support substrate 51. Materials used for the high-velocity acoustic wave support substrate 51 include, for example, piezoelectric materials such as aluminum nitride, lithium tantalate, lithium niobate, and quartz; dielectric materials such as bauxite, sapphire, magnesium oxide, silicon nitride, silicon carbide, zirconium oxide, cordierite, mullite, block talc, forsterite, spinel, and silane; dielectric materials such as alumina, silicon oxynitride, DLC (diamond-like carbon), and diamond; or semiconductor materials such as silicon; or materials with the above materials as the main component. Furthermore, the aforementioned spinels include aluminum compounds containing one or more elements selected from Mg, Fe, Zn, Mn, etc., and oxygen. Examples of the aforementioned spinels include MgAl2O4, FeAl2O4, ZnAl2O4, and MnAl2O4.

[0071] The low-velocity layer 52 is a film in which the velocity of the bulk waves propagating in the piezoelectric layer 53 is lower than that of the bulk waves propagating in the piezoelectric layer 53, and it is disposed between the piezoelectric layer 53 and the high-velocity support substrate 51. Based on this structure and the property that the energy of elastic waves is essentially concentrated in a low-velocity medium, leakage of surface acoustic wave energy to the outside of the piezoelectric layer 53 is suppressed. For example, materials such as glass, silicon oxide, silicon oxynitride, lithium oxide, tantalum oxide, or compounds obtained by adding fluorine, carbon, or boron to silicon oxide, or materials mainly composed of the aforementioned materials, can be used as the material for the low-velocity layer 52.

[0072] Furthermore, based on the above-described laminated structure of the piezoelectric substrate 50, compared to the existing structure using a single layer of piezoelectric substrate, the Q value at the resonant frequency and anti-resonant frequency can be significantly improved. That is, a high-Q elastic wave resonator can be constructed, and therefore, using this elastic wave resonator, a filter with low insertion loss can be constructed.

[0073] Furthermore, the hypersonic support substrate 51 may also have a structure in which a support substrate and a hypersonic film are stacked, and the sound speed of the bulk wave propagating in this hypersonic film is higher than that of elastic waves such as surface waves and boundary waves propagating in the piezoelectric layer 53. In this case, the same material as the hypersonic support substrate 51 can be used as the material of the hypersonic film. In addition, as the material of the support substrate, for example, ceramics such as aluminum nitride, lithium tantalate, lithium niobate, and quartz, piezoelectric materials, bauxite, sapphire, magnesium oxide, silicon nitride, silicon carbide, zirconium oxide, cordierite, mullite, block talc, and forsterite, ceramics, diamond, glass, and other dielectrics, silicon, gallium nitride, and other semiconductors, or resins, or materials mainly composed of the above materials can be used.

[0074] Furthermore, in this specification, "main component of the material" refers to the component that occupies more than 50% by weight in the material. The aforementioned main component may also exist in any of the following states: single crystal, polycrystalline, and amorphous, or a mixture thereof.

[0075] Figure 2B This is a cross-sectional view schematically illustrating a second example of the elastic wave resonator constituting the elastic wave filter 1 according to the embodiment. Figure 2A The elastic wave resonator 60 shown illustrates an example where the IDT electrode 54 is formed on a piezoelectric substrate 50 having a piezoelectric layer 53, but the substrate on which the IDT electrode 54 is formed can also be as shown. Figure 2B The image shows a single-layer piezoelectric single-crystal substrate 57 including a piezoelectric layer.

[0076] The elastic wave resonator constituting the elastic wave filter 1 includes an IDT electrode 54, a protective layer 55, and a piezoelectric substrate 50.

[0077] like Figure 2B As shown, the elastic wave resonator in this example includes an IDT electrode 54, a dielectric layer 58, an adjustment film 59, and a piezoelectric single crystal substrate 57.

[0078] The piezoelectric single crystal substrate 57 is an example of a substrate with piezoelectric properties, for example, it is made of a piezoelectric single crystal of lithium niobate or lithium tantalate.

[0079] A dielectric layer 58 is formed to cover the surface of the IDT electrode 54 and the piezoelectric single crystal substrate 57. The thickness of the dielectric layer 58 is greater than the height (film thickness) of the IDT electrode 54. The dielectric layer 58 is a layer for purposes such as protecting the main electrode layer 542 from damage by the external environment, adjusting frequency and temperature characteristics, and improving moisture resistance, and is, for example, a dielectric film with silicon dioxide as the main component.

[0080] An adjustment film 59 is formed on the surface of the dielectric layer 58. The adjustment film 59 is a layer intended to adjust the frequency of the passband, etc., of the elastic wave filter 1, and is, for example, a film mainly composed of silicon nitride. Alternatively, the adjustment film 59 may not be present.

[0081] In addition, the piezoelectric layer 53 and the piezoelectric single crystal substrate 57 can also be appropriately modified in terms of their stacking structure, materials, cutting angles and thicknesses according to the requirements of the elastic wave filter 1.

[0082] In addition, the substrate on which the IDT electrode 54 is formed, besides Figure 2A The piezoelectric substrate 50 shown and Figure 2B In addition to the piezoelectric single-crystal substrate 57 shown, it may also have a structure in which a support substrate, an energy sealing layer, and a piezoelectric film are sequentially stacked. In this case, an IDT electrode 54 is formed on the piezoelectric film. The piezoelectric film may be, for example, a LiTaO3 piezoelectric single crystal or a piezoelectric ceramic. The support substrate is a substrate that supports the piezoelectric film, the energy sealing layer, and the IDT electrode 54.

[0083] The energy sealing layer comprises one or more layers, wherein the velocity of the bulk elastic wave propagating in at least one layer is greater than the velocity of the elastic wave propagating near the piezoelectric film. For example, the energy sealing layer can also be a stacked structure of a low-velocity layer and a high-velocity layer. The low-velocity layer is a film in which the velocity of the bulk wave is low compared to the velocity of the elastic wave propagating in the piezoelectric film. The high-velocity layer is a film in which the velocity of the bulk wave is high compared to the velocity of the elastic wave propagating in the piezoelectric film. Alternatively, the support substrate can be configured as a high-velocity layer.

[0084] Alternatively, the energy encapsulation layer can also be an acoustic impedance layer with an alternating structure of low acoustic impedance layers with relatively low acoustic impedance and high acoustic impedance layers with relatively high acoustic impedance.

[0085] Furthermore, the elastic wave device 1 according to this embodiment is not limited to a structure having a SAW resonator, and can also be applied to a structure having a laterally excited bulk acoustic resonator (XBAR). An XBAR has a thin-film structure in which an IDT electrode is formed on a first main surface of a piezoelectric layer, and a cavity is formed on a second main surface of the piezoelectric layer opposite to the first main surface. That is, in the elastic wave device 1 according to this embodiment, the series arm resonators 11-15 and the parallel arm resonators 21-26 can also each have an XBAR structure.

[0086] Next, the construction of the capacitor elements (capacitors 32 and 35) constituting the elastic wave filter 1 will be described.

[0087] Figure 3 This is a top view showing the electrode arrangement of the elastic wave resonator and capacitor element according to the embodiment. The figure illustrates the arrangement of the IDT electrodes of the parallel arm resonator 22 constituting the elastic wave filter 1 according to the embodiment and a pair of comb electrodes of the capacitor 32. Figure 3 As shown, on the main surface of the piezoelectric substrate 50, the IDT electrode (and reflector of the parallel arm resonator 22) and the comb electrode of the capacitor 32 are formed.

[0088] Capacitor 32 comprises a piezoelectric substrate 50 and a pair of comb-shaped electrodes. The pair of comb-shaped electrodes of capacitor 32 are each composed of a plurality of parallel second electrode fingers (electrode fingers 71a and 71b) and a second busbar electrode (72a and 72b) connecting the plurality of second electrode fingers. Capacitor 35 also has the same electrode structure as capacitor 32. The plurality of second electrode fingers constituting capacitors 32 and 35 are formed along a direction intersecting the direction of elastic wave propagation (X-axis direction).

[0089] like Figure 3As shown, one busbar electrode 62a of the IDT electrode of the parallel arm resonator 22 is connected to one busbar electrode 72a of the pair of comb electrodes of the capacitor 32 via connection node n1. Furthermore, the other busbar electrode 62b of the IDT electrode of the parallel arm resonator 22 is connected to the other busbar electrode 72b of the pair of comb electrodes of the capacitor 32 via connection node n2. The first extension direction of the electrode fingers 61a and 61b of the IDT electrode of the parallel arm resonator 22 intersects the second extension direction of the electrode fingers 71a and 71b of the pair of comb electrodes of the capacitor 32. This suppresses interference between the elastic wave propagating in the parallel arm resonator 22 and the high-frequency signal propagating in the capacitor 32. Additionally, the first extension direction of the electrode fingers of the IDT electrode of the parallel arm resonator 25 intersects the second extension direction of the electrode fingers of the pair of comb electrodes of the capacitor 35. This also suppresses interference between the elastic wave propagating in the parallel arm resonator 25 and the high-frequency signal propagating in the capacitor 35.

[0090] Furthermore, the extension direction of the electrode fingers of the IDT electrodes of each of the series arm resonators 11-15 and the parallel arm resonators 21-26 is consistent with the first extension direction.

[0091] In addition, the series arm resonators 11-15 and the parallel arm resonators 21-26 are formed in Figure 2B In the case of the piezoelectric single crystal substrate 57 shown, capacitors 32 and 35 are formed on the piezoelectric single crystal substrate 57.

[0092] Alternatively, the piezoelectric substrate 50 may include a first piezoelectric layer and a second piezoelectric layer, with the IDT electrode of the parallel arm resonator 22 and a pair of comb electrodes of the capacitor 32 formed on the first piezoelectric layer, and the IDT electrode of the parallel arm resonator 25 and a pair of comb electrodes of the capacitor 35 formed on the second piezoelectric layer.

[0093] Here, the electrode parameters of the IDT electrode 54 constituting the elastic wave resonator 60 and the electrode parameters of the comb-shaped electrodes constituting the capacitor elements (capacitors 32 and 35) are explained.

[0094] The wavelength λ of the elastic wave resonator 60 and the capacitor element is determined by... Figure 2AThe repeating period of the plurality of electrode fingers 61a or 61b constituting the IDT electrode 54 is specified as shown in (b). Furthermore, the electrode finger spacing P is half the wavelength λ, defined by (L+S) when the linewidth of the electrode fingers 61a and 61b constituting the comb electrodes 60a and 60b is set to L, and the spacing width between adjacent electrode fingers 61a and 61b is set to S. Additionally, the electrode finger duty cycle D of the IDT electrode 54 of the elastic wave resonator 60 and the comb electrode of the capacitor element is the linewidth occupancy rate of the electrode fingers 61a and 61b, defined by L / (L+S) as the ratio of the linewidth L of each electrode finger 61a and 61b to the sum of the linewidth L and the spacing width S. Furthermore, the cross width V of the IDT electrode 54 is the length of the overlapping electrode fingers when viewed from a direction perpendicular to the electrode fingers 61a and 61b and parallel to the main surface of the piezoelectric substrate 50. In addition, the height (film thickness) of the comb electrodes 60a and 60b (IDT electrode 54) is set to h.

[0095] Furthermore, in the IDT electrode 54, when the spacing between adjacent electrode fingers is not fixed, the electrode finger spacing P of the IDT electrode 54 is determined by the average electrode finger spacing P of the IDT electrode 54. AVE Definition. When the total number of electrode fingers 61a and 61b included in the IDT electrode 54 is set to Ni, and the center-to-center distance between the electrode fingers at one end of the IDT electrode 54 located in the elastic wave propagation direction and the electrode fingers at the other end is set to Di, the average electrode finger spacing P of the IDT electrode 54 is defined. AVE It is defined as Di / (Ni-1).

[0096] Furthermore, in the comb-shaped electrodes of the capacitor element, when the spacing between adjacent electrode fingers is not fixed, it also relates to the average electrode finger spacing P of the IDT electrode 54. AVE Similarly, when the total number of second electrode fingers included in the comb electrode of the capacitor element is set to Ni, and the distance between the centers of the second electrode fingers at one end and the second electrode fingers at the other end of the comb electrode of the capacitor element is set to Di, the average electrode finger spacing P of the comb electrode of the capacitor element is defined as follows: AVE It is defined as Di / (Ni-1).

[0097] Furthermore, in the IDT electrode 54, when the electrode finger duty cycle D is not fixed, the electrode finger duty cycle D of the IDT electrode 54 is determined by the average electrode finger duty cycle D of the IDT electrode 54. AVE Definition. Let the total number of electrode fingers 61a and 61b included in the IDT electrode 54 be Ni, and the total linewidth L obtained by adding the linewidths L of (Ni-1) electrode fingers be L. ALLThe total spacing width obtained by adding up the (Ni-1) spacing widths S contained in the IDT electrode 54 is set as S. ALL In this case, the average electrode index duty cycle D of IDT electrode 54 AVE By L ALL / (L) ALL +S ALL )definition.

[0098] Furthermore, in the comb-shaped electrodes of the capacitor element, when the duty cycle D of the electrode fingers is not fixed, it is also related to the average duty cycle D of the electrode fingers of the IDT electrode 54. AVE Similarly, let the total number of second electrode fingers contained in the comb-shaped electrode be Ni, and let the total linewidth L obtained by adding the linewidths L of (Ni-1) electrode fingers be L. ALL The total spacing width S is obtained by adding up the (Ni-1) spacing widths S contained in the comb electrode. ALL In this case, the average electrode index D of the comb-shaped electrodes of the capacitor element is... AVE By L ALL / (L) ALL +S ALL )definition.

[0099] Furthermore, the electrode finger spacing P and electrode finger duty cycle D of the comb electrodes of the IDT electrode 54 and the capacitor element can be measured by observing the main surface of the substrate on which the comb electrodes of the IDT electrode 54 and the capacitor element are formed from top view using a scanning electron microscope (SEM), a scanning transmission electron microscope (STEM), or a transmission electron microscope (TEM), and / or by observing the cross-section perpendicular to the extension direction of the electrode fingers, thereby measuring the line width L and the spacing width S.

[0100] [3. Resonance characteristics and transmission characteristics of the elastic wave filter 1 involved in the embodiment]

[0101] First, the basic operating principle of a trapezoidal bandpass filter consisting of a series arm resonator and a parallel arm resonator will be explained.

[0102] A parallel-arm resonator has a resonant frequency *frp* and an anti-resonant frequency *fap* (> *frp*), while a series-arm resonator has a resonant frequency *frs* and an anti-resonant frequency *fas* (> *frs*> *frp*). In both series-arm and parallel-arm resonators with these resonant characteristics, the anti-resonant frequency *fap* of the parallel-arm resonator is typically made close to the resonant frequency *frs* of the series-arm resonator. Therefore, the area near the resonant frequency *frp*, where the impedance of the parallel-arm resonator approaches zero, becomes a low-frequency stopband. Furthermore, if the frequency increases from this point, the impedance of the parallel-arm resonator increases near the anti-resonant frequency *fap*, and the impedance of the series-arm resonator approaches zero near the resonant frequency *frs*. Therefore, a signal passband is formed in the signal path that serves as the series arm path, in the area between the anti-resonant frequency *fap* and the resonant frequency *frs*. This allows for the formation of a passband that reflects the electrode parameters and electromechanical coupling coefficient of the elastic wave resonator. Moreover, when the frequency increases and approaches the anti-resonant frequency *fas*, the impedance of the series-arm resonator increases, becoming a high-frequency stopband.

[0103] Next, the resonant characteristics and throughput characteristics of the elastic wave filter 1 involved in the embodiment will be explained. The elastic wave filter 1 involved in the embodiment, compared with the elastic wave filter 1 involved in the implementation, specifies the specific values ​​of the wavelength λ (electrode finger spacing × 2) and electrode finger duty cycle D of each elastic wave resonator (series arm resonator, parallel arm resonator) and capacitor element.

[0104] Table 1 shows data for the elastic wave resonator and capacitor elements constituting the elastic wave filter 1 according to the embodiment. Furthermore, the data for the elastic wave filter 1 shown in Table 1 are illustrative and can be appropriately modified according to the required passband of the elastic wave filter 1.

[0105] [Table 1]

[0106]

[0107] In the elastic wave filter 1 described in the embodiment, capacitor elements (capacitors 32 and 35) are connected in parallel with parallel arm resonators 22 and 25 among the series arm resonators 11-15 and the parallel arm resonators 21-26. This reduces the fractional bandwidth of the parallel arm resonator formed by parallel arm resonator 22 and capacitor 32, and the parallel arm resonator formed by parallel arm resonator 25 and capacitor 35 (the value obtained by dividing the frequency difference between the anti-resonant frequency and the resonant frequency by the center frequency of the anti-resonant frequency and the resonant frequency). This improves the abruptness at the passband end of the elastic wave filter 1.

[0108] However, when a piezoelectric substrate 50 with a multilayer substrate structure having a high-velocity layer and a low-velocity layer is used for the elastic wave filter, or when a piezoelectric single crystal substrate 57 including lithium niobate or lithium tantalate is used and Rayleigh wave, Raf wave, leak wave or Lamb wave is utilized, sometimes higher-order mode spurious emissions are generated in the frequency band higher than the passband due to the capacitor element connected in parallel with the elastic wave resonator, and the attenuation characteristics deteriorate.

[0109] In contrast, in the elastic wave filter 1 involved in this embodiment, the wavelength λ32 (electrode finger spacing P32×2) of capacitor 32 is different from the wavelength λ35 (electrode finger spacing P35×2) of capacitor 35.

[0110] Furthermore, the wavelength λ32 (electrode finger spacing P32×2) of capacitor 32 is smaller than any of the wavelengths λ of series arm resonators 11-15 and parallel arm resonators 21-26, and the wavelength λ35 (electrode finger spacing P35×2) of capacitor 35 is smaller than any of the wavelengths λ of series arm resonators 11-15 and parallel arm resonators 21-26.

[0111] As a result, spurious higher-order modes caused by capacitors 32 and 35 are generated on the higher-frequency side of the passband of elastic wave filter 1.

[0112] Figure 4A This is a graph showing the impedance characteristics of the capacitive elements included in the elastic wave filter 1 according to the embodiment. The graph illustrates the impedance characteristics of the capacitive elements included in the elastic wave filters according to the embodiment and the comparative example. Furthermore, the elastic wave filter according to the comparative example has the same circuit structure as the elastic wave filter 1 according to the embodiment. That is, the elastic wave filter according to the comparative example includes series arm resonators 11, 12, 13, 14 and 15, and parallel arm resonators 21, 22, 23, 24, 25 and 26, capacitors 32 and 35, and input / output terminals 110 and 120. However, in the elastic wave filter according to the comparative example, the wavelength λ32 (electrode finger spacing P32×2) of capacitor 32 is equal to the wavelength λ35 (electrode finger spacing P35×2) of capacitor 35.

[0113] like Figure 4A As shown, in the elastic wave filter involved in the comparative example, since the wavelength λ32 of capacitor 32 is equal to the wavelength λ35 of capacitor 35, the anti-resonance frequency fa320 of capacitor 32 is the same as the anti-resonance frequency fa350 of capacitor 35, and the maximum impedance at the anti-resonance frequencies fa320 and fa350 becomes larger.

[0114] In contrast, in the elastic wave filter 1 of the embodiment, the anti-resonant frequency fa32 of capacitor 32 is different from the anti-resonant frequency fa35 of capacitor 35. Specifically, the wavelength λ32 (=1.200μm) of capacitor 32 is smaller than the wavelength λ35 (=1.250μm) of capacitor 35. Therefore, the anti-resonant frequency fa32 is located at a higher frequency than the anti-resonant frequency fa35. Consequently, the maximum impedance at each of the anti-resonant frequencies fa32 and fa35 is smaller than the maximum impedance at the anti-resonant frequencies fa320 and fa350 of the elastic wave filter of the comparative example.

[0115] Figure 4B This is a diagram illustrating the relationship between the resonant characteristics of capacitors 32 and 35 in the elastic wave filter 1 according to the embodiment. As shown in the diagram, by making the anti-resonant frequency fa32 of capacitor 32 different from the anti-resonant frequency fa35 of capacitor 35, the maximum impedance of the capacitors arranged in the parallel arm path of elastic wave filter 1 is reduced. Therefore, the attenuation (insertion loss) of the anti-resonant frequencies fa32 and fa35 in the pass-through characteristics from input / output terminal 110 to input / output terminal 120 can be ensured to a greater extent.

[0116] Figure 4C This is a graph showing the pass-through characteristics of the elastic wave filters according to the embodiments and comparative examples. As shown in the graph, compared with the elastic wave filter according to the comparative example, the elastic wave filter 1 according to the embodiments does not deteriorate the insertion loss in the passband and improves the attenuation characteristics in the frequency band (3GHz-4GHz) higher than the passband. This is because the anti-resonant frequency fa32 of capacitor 32 is different from the anti-resonant frequency fa35 of capacitor 35.

[0117] Furthermore, in the elastic wave filter 1 according to the embodiment, instead of making the wavelength λ32 (electrode finger spacing P32×2) of capacitor 32 different from the wavelength λ35 (electrode finger spacing P35×2) of capacitor 35, the duty cycle D32 of the electrode fingers of capacitor 32 can be made different from the duty cycle D35 of the electrode fingers of capacitor 35. Specifically, for example, by making the duty cycle D32 of the electrode fingers of capacitor 32 smaller than the duty cycle D35 of the electrode fingers of capacitor 35, the anti-resonant frequency fa32 can be located at a higher frequency side than the anti-resonant frequency fa35. As a result, since the anti-resonant frequency fa32 of capacitor 32 is different from the anti-resonant frequency fa35 of capacitor 35, the maximum impedance of the capacitors arranged in the parallel arm path of elastic wave filter 1 is reduced, and the attenuation (insertion loss) of the anti-resonant frequencies fa32 and fa35 in the transmission characteristics from input / output terminal 110 to input / output terminal 120 can be ensured to a greater extent.

[0118] Alternatively, the wavelength λ32 (electrode finger spacing P32×2) of capacitor 32 can be different from that of capacitor 35 (electrode finger spacing P35×2), and the duty cycle D32 of the electrode fingers of capacitor 32 can be different from that of capacitor 35. This allows the anti-resonant frequency fa32 of capacitor 32 to be precisely different from that of capacitor 35, thus enabling precise suppression of the attenuation (insertion loss) of the anti-resonant frequencies fa32 and fa35 in the transmission characteristics from input / output terminal 110 to input / output terminal 120.

[0119] Furthermore, in the elastic wave filter 1 according to the embodiment, the electrode film thickness of capacitor 32 can be different from that of capacitor 35. Specifically, for example, by making the electrode film thickness of capacitor 32 smaller than that of capacitor 35, the anti-resonant frequency fa32 can be located at a higher frequency side than the anti-resonant frequency fa35. As a result, the anti-resonant frequency fa32 of capacitor 32 is different from that of capacitor 35, thus reducing the maximum impedance of the capacitors arranged in the parallel arm path of elastic wave filter 1, and ensuring a greater attenuation (insertion loss) of the anti-resonant frequencies fa32 and fa35 in the transmission characteristics from input / output terminal 110 to input / output terminal 120.

[0120] The resonant frequency and anti-resonant frequency are approximately inversely proportional to the product of the electrode finger spacing and the electrode finger duty cycle (where the electrode finger duty cycle is ≤ approximately 0.65). Based on this viewpoint, in the elastic wave filter 1 according to the embodiment, instead of making the anti-resonant frequency fa32 of capacitor 32 different from the anti-resonant frequency fa35 of capacitor 35, the product of the electrode finger duty cycle D32 and wavelength λ32 (electrode finger spacing P32×2) of capacitor 32 can be made different from the product of the electrode finger duty cycle D35 and wavelength λ35 (electrode finger spacing P35×2) of capacitor 35.

[0121] [4. Resonance and transmission characteristics of the elastic wave filter 1A involved in Modification Example 1]

[0122] Next, the circuit structure and resonant characteristics of the elastic wave filter 1A according to the modified example 1 of the embodiment will be described.

[0123] Figure 5AThis is a circuit diagram of the elastic wave filter 1A according to Embodiment Modification 1. As shown in the figure, the elastic wave filter 1A is an example of an elastic wave device, including series arm resonators 11, 12, 13, 14 and 15, parallel arm resonators 21, 22, 23, 24, 25 and 26, capacitors 42 and 44, and input / output terminals 110 and 120. The connection structure of the capacitor elements (capacitors 42 and 44) ​​in the elastic wave filter 1A according to this modification differs from that in the elastic wave filter 1 according to Embodiment 1. Therefore, in the following description of the elastic wave filter 1A according to this modification, the same structures as those in the elastic wave filter 1 according to Embodiment 1 will be omitted, and the description will focus on the different structures.

[0124] The series arm resonators 11 to 15 each include an elastic wave resonator, which are arranged in series in the series arm path that connects the input / output terminal 110 (first input / output terminal) and the input / output terminal 120 (second input / output terminal). The series arm resonator 12 is an example of a first elastic wave resonator, and the series arm resonator 14 is an example of a second elastic wave resonator.

[0125] Parallel arm resonators 21 to 26 are examples of the third elastic wave resonator, connected between the aforementioned series arm path and ground.

[0126] Capacitor 42 is an example of a first capacitive element, connected in parallel with the series arm resonator 12. Specifically, one end of capacitor 42 is connected to the connection node of the series arm resonators 11, 12, and 22, and the other end of capacitor 42 is connected to the connection node of the series arm resonators 12, 13, and 23. Capacitor 42 is a so-called bridging capacitor connected in parallel with the series arm resonator 12.

[0127] Capacitor 44 is an example of a second capacitive element, connected in parallel with the series arm resonator 14. Specifically, one end of capacitor 44 is connected to the connection node of the series arm resonators 13, 14, and 24, and the other end of capacitor 44 is connected to the connection node of the series arm resonators 14, 15, and 25. Capacitor 44 is a so-called bridging capacitor connected in parallel with the series arm resonator 14.

[0128] Capacitors 42 and 44 each include comb-shaped electrodes formed on a piezoelectric substrate, and resonate with the substrate. Thus, capacitors 42 and 44 respectively have a resonant frequency with extremely low impedance and an anti-resonant frequency with extremely high impedance.

[0129] Furthermore, although not shown in the figure, the extension direction of the electrode fingers of the IDT electrodes of each of the series arm resonators 11-15 and the parallel arm resonators 21-26 is consistent with the first extension direction. The first extension direction intersects with the second extension direction of the electrode fingers of the IDT electrodes of the capacitor 42, and the first extension direction intersects with the extension direction of the electrode fingers of the IDT electrodes of the capacitor 44.

[0130] Here, the resonant frequency fr42 of capacitor 42 is different from the resonant frequency fr44 of capacitor 44.

[0131] Therefore, in the attenuation band of the elastic wave filter 1A at a higher frequency than the passband, spurious high-order modes can be suppressed, thus providing an elastic wave filter 1A with improved attenuation characteristics at a higher frequency than the passband.

[0132] Furthermore, in this modified example, "the resonant frequency of the first capacitor element is different from the resonant frequency of the second capacitor element" means that the first-order resonant frequency of the first capacitor element is different from the aforementioned first-order resonant frequency of the second capacitor element. That is, the resonant frequencies of the first capacitor element and the second capacitor element, which are being compared, have the same order.

[0133] Furthermore, the wavelength λ42 (electrode finger spacing P42×2) of capacitor 42 is smaller than any of the wavelengths λ of series arm resonators 11-15 and parallel arm resonators 21-26, and the wavelength λ44 (electrode finger spacing P44×2) of capacitor 44 is smaller than any of the wavelengths λ of series arm resonators 11-15 and parallel arm resonators 21-26.

[0134] As a result, spurious higher-order modes caused by capacitors 42 and 44 are generated on the higher-frequency side of the passband of elastic wave filter 1A.

[0135] Furthermore, at least one of the series arm resonators 11, 13 and 15 may not be included in the elastic wave filter 1A, and at least one of the parallel arm resonators 21 to 26 may not be included in the elastic wave filter 1A.

[0136] Furthermore, capacitor 42 may not be connected in parallel with series arm resonator 12, or it may be connected in parallel with any one of series arm resonators 11, 13, and 15. Similarly, capacitor 44 may not be connected in parallel with series arm resonator 14, or it may be connected in parallel with any one of series arm resonators 11, 13, and 15.

[0137] Furthermore, in this modified example, no capacitors are connected in parallel to the parallel arm resonators 21 to 26.

[0138] Alternatively, the piezoelectric substrate 50 may include a first piezoelectric layer and a second piezoelectric layer, with the IDT electrode of the series arm resonator 12 and a pair of comb electrodes of the capacitor 42 formed on the first piezoelectric layer, and the IDT electrode of the series arm resonator 14 and a pair of comb electrodes of the capacitor 44 formed on the second piezoelectric layer.

[0139] In addition, the elastic wave filter 1A can have 6 or more series arm resonators and 7 or more parallel arm resonators.

[0140] Alternatively, longitudinally coupled resonators, inductors, capacitors, and switches can be connected between the series arm resonators 11-15, the parallel arm resonators 21-26, the ground, and the input / output terminals 110 and 120. Furthermore, the inductor may also include a wiring inductor formed by wiring connecting the various components, wiring within the package, and vias.

[0141] Figure 5B This is a diagram showing the relationship between the resonant characteristics of capacitors 42 and 44 in the elastic wave filter 1A according to Modification 1 of the embodiment. As shown in the diagram, by making the resonant frequency fr42 of capacitor 42 different from the resonant frequency fr44 of capacitor 44, the minimum value of the impedance of the capacitors arranged in the series arm path of the elastic wave filter 1A is increased. Therefore, the attenuation (insertion loss) of the resonant frequencies fr42 and fr44 in the transmission characteristics from the input / output terminal 110 to the input / output terminal 120 can be ensured to a greater extent.

[0142] Therefore, compared to conventional elastic wave filters where the resonant frequencies fr42 and fr44 of capacitor 42 and 44 are equal, the elastic wave filter 1A involved in Modification Example 1 does not worsen the insertion loss in the passband and improves the attenuation characteristics in the frequency band higher than the passband. This is because the resonant frequencies fr42 and fr44 of capacitor 42 are different.

[0143] Furthermore, in the elastic wave filter 1A according to this modified example, as a structure to make the resonant frequency fr42 of capacitor 42 different from the resonant frequency fr44 of capacitor 44, the wavelength λ44 (electrode finger spacing P44×2) of capacitor 42 can also be different from the wavelength λ44 (electrode finger spacing P44×2) of capacitor 44. Specifically, by making the wavelength λ42 of capacitor 42 larger than the wavelength λ44 of capacitor 44, the resonant frequency fr42 is located on the lower frequency side than the resonant frequency fr44.

[0144] Alternatively, instead of making the wavelength λ42 (electrode finger spacing P42×2) of capacitor 42 different from the wavelength λ44 (electrode finger spacing P44×2) of capacitor 44, the duty cycle D42 of capacitor 42 can be made different from the duty cycle D44 of capacitor 44. Specifically, for example, by making the duty cycle D42 of capacitor 42 larger than the duty cycle D44 of capacitor 44, the resonant frequency fr42 can be located at a lower frequency than the resonant frequency fr44. As a result, the resonant frequency fr42 of capacitor 42 is different from the resonant frequency fr44 of capacitor 44. Therefore, the minimum impedance of the capacitors arranged in the series arm path of elastic wave filter 1A is increased, which can greatly ensure the attenuation (insertion loss) of the resonant frequencies fr42 and fr44 in the transmission characteristics from input / output terminal 110 to input / output terminal 120.

[0145] Alternatively, the wavelength λ42 (electrode finger spacing P42×2) of capacitor 42 can be made different from the wavelength λ44 (electrode finger spacing P44×2) of capacitor 44, and the duty cycle D42 of the electrode fingers of capacitor 42 can be made different from the duty cycle D44 of the electrode fingers of capacitor 44. This allows the resonant frequency fr42 of capacitor 42 to be precisely different from the resonant frequency fr44 of capacitor 44, thus enabling precise suppression of the attenuation (insertion loss) of the resonant frequencies fr42 and fr44 in the transmission characteristics from input / output terminal 110 to input / output terminal 120.

[0146] Furthermore, in the elastic wave filter 1A according to this modification, the electrode film thickness of capacitor 42 can be different from that of capacitor 44. Specifically, for example, by making the electrode film thickness of capacitor 42 greater than that of capacitor 44, the resonant frequency fr42 can be located at a lower frequency than the resonant frequency fr44. As a result, the resonant frequency fr42 of capacitor 42 is different from the resonant frequency fr44 of capacitor 44. Therefore, the minimum impedance of the capacitors arranged in the series arm path of the elastic wave filter 1A is increased, which can greatly ensure the attenuation (insertion loss) of the resonant frequencies fr42 and fr44 in the transmission characteristics from input / output terminal 110 to input / output terminal 120.

[0147] Furthermore, in the elastic wave filter 1A involved in this modified example, instead of making the resonant frequency fr42 of capacitor 42 different from the resonant frequency fr44 of capacitor 44, the product of the duty cycle D42 of the electrode fingers of capacitor 42 and the wavelength λ42 (electrode finger spacing P42×2) is different from the product of the duty cycle D44 of the electrode fingers of capacitor 44 and the wavelength λ44 (electrode finger spacing P44×2).

[0148] [5. Resonance and transmission characteristics of the elastic wave filter 1B involved in Modification Example 2]

[0149] Next, the circuit structure and resonance characteristics of the elastic wave filter 1B according to the modified example 2 of the embodiment will be described.

[0150] Figure 6A This is a circuit diagram of the elastic wave filter 1B according to Embodiment Modification 2. As shown in the figure, the elastic wave filter 1B is an example of an elastic wave device, including series arm resonators 11, 12, 13, 14 and 15, parallel arm resonators 21, 22, 23, 24, 25 and 26, capacitors 32 and 44, and input / output terminals 110 and 120. The connection structure of the capacitor element (capacitor 44) in the elastic wave filter 1B according to this modification differs from that in the elastic wave filter 1 according to Embodiment 2. Therefore, the following description of the elastic wave filter 1B according to this modification will omit descriptions of structures identical to those in the elastic wave filter 1 according to Embodiment 2, and will focus on the different structures.

[0151] The series arm resonators 11-15 each include an elastic wave resonator, which are arranged in series in the series arm path connecting the input / output terminal 110 (first input / output terminal) and the input / output terminal 120 (second input / output terminal). The series arm resonator 14 is an example of the first elastic wave resonator.

[0152] Parallel arm resonators 21-26 each include an elastic wave resonator, connected between the aforementioned series arm path and ground. Parallel arm resonator 22 is an example of a second elastic wave resonator.

[0153] The series arm resonators 11-13 and 15 and the parallel arm resonators 21 and 23-26 are examples of the third elastic wave resonator.

[0154] Capacitor 44 is an example of a first capacitive element, connected in parallel with series arm resonator 14. Specifically, one end of capacitor 44 is connected to the connection node of series arm resonators 13, 14, and 24, and the other end of capacitor 44 is connected to the connection node of series arm resonators 14, 15, and 25. Capacitor 44 is a so-called bridging capacitor connected in parallel with series arm resonator 14.

[0155] Capacitor 32 is an example of a second capacitive element, connected in parallel with the parallel arm resonator 22. Specifically, one end of capacitor 32 is connected to the connection node of the series arm resonators 11, 12, and 22, and the other end is connected to the connection node between the parallel arm resonator 22 and ground. Capacitor 32 is a so-called bridging capacitor connected in parallel with the parallel arm resonator 22.

[0156] Capacitors 32 and 44 each include comb-shaped electrodes formed on a piezoelectric substrate, and resonate with the substrate. Thus, capacitors 32 and 44 respectively have a resonant frequency with minimal impedance and an anti-resonant frequency with extremely large impedance.

[0157] Furthermore, although not illustrated, the extension direction of the electrode fingers of the IDT electrodes of each of the series arm resonators 11-15 and the parallel arm resonators 21-26 is consistent with the first extension direction. The first extension direction intersects with the second extension direction of the electrode fingers of the IDT electrodes of the capacitor 32, and the first extension direction intersects with the extension direction of the electrode fingers of the IDT electrodes of the capacitor 44.

[0158] Here, the anti-resonance frequency fa32 of capacitor 32 is smaller than the resonance frequency fr44 of capacitor 44, or the anti-resonance frequency fa32 of capacitor 32 is larger than the anti-resonance frequency fa44 of capacitor 44.

[0159] Therefore, in the attenuation band of the elastic wave filter 1B at a higher frequency than the passband, spurious high-order modes can be suppressed, thus providing an elastic wave filter 1B with improved attenuation characteristics at a higher frequency than the passband.

[0160] Furthermore, in this modified example, "the anti-resonant frequency of the second capacitor element is smaller than the resonant frequency of the first capacitor element" means that the first-order anti-resonant frequency of the second capacitor element is smaller than the aforementioned first-order resonant frequency of the first capacitor element. That is, the order of the anti-resonant frequency of the second capacitor element being compared is equal to the order of the resonant frequency of the first capacitor element. Conversely, "the anti-resonant frequency of the second capacitor element is larger than the anti-resonant frequency of the first capacitor element" means that the first-order anti-resonant frequency of the second capacitor element is larger than the aforementioned first-order anti-resonant frequency of the first capacitor element. That is, the order of the anti-resonant frequency of the second capacitor element being compared is equal to the order of the anti-resonant frequency of the first capacitor element.

[0161] Furthermore, the wavelength λ32 (electrode finger spacing P32×2) of capacitor 32 is smaller than any of the wavelengths λ of series arm resonators 11-15 and parallel arm resonators 21-26, and the wavelength λ44 (electrode finger spacing P44×2) of capacitor 44 is smaller than any of the wavelengths λ of series arm resonators 11-15 and parallel arm resonators 21-26.

[0162] As a result, spurious higher-order modes caused by capacitors 32 and 44 are generated on the higher-frequency side of the passband of elastic wave filter 1B.

[0163] Furthermore, at least one of the series arm resonators 11, 12, 13 and 15 may not be included in the elastic wave filter 1B, and at least one of the parallel arm resonators 21, 23, 24, 25 and 26 may not be included in the elastic wave filter 1B.

[0164] Furthermore, capacitor 44 may not be connected in parallel with series arm resonator 14, or it may be connected in parallel with any one of series arm resonators 11, 12, 13, and 15. Similarly, capacitor 32 may not be connected in parallel with parallel arm resonator 22, or it may be connected in parallel with any one of parallel arm resonators 21, 23, 24, 25, and 26.

[0165] Furthermore, in this modified example, no capacitors are connected in parallel to the series arm resonators 11-13, 15 and the parallel arm resonators 21, 23-26.

[0166] Alternatively, the piezoelectric substrate 50 may include a first piezoelectric layer and a second piezoelectric layer, with the IDT electrode of the series arm resonator 14 and a pair of comb electrodes of the capacitor 44 formed on the first piezoelectric layer, and the IDT electrode of the parallel arm resonator 22 and a pair of comb electrodes of the capacitor 32 formed on the second piezoelectric layer.

[0167] Furthermore, when the series arm resonators 11-15 and the parallel arm resonators 21-26 each have an XBAR structure, the thickness of the first piezoelectric layer can be different from the thickness of the second piezoelectric layer. This allows for high-precision adjustment of the Q value and fractional bandwidth of each resonator.

[0168] In addition, the number of series arm resonators in the elastic wave filter 1B can be 6 or more, and the number of parallel arm resonators can be 7 or more.

[0169] Alternatively, longitudinally coupled resonators, inductors, capacitors, and switches can be connected between the series arm resonators 11-15, the parallel arm resonators 21-26, the ground, and the input / output terminals 110 and 120. Furthermore, the inductor may also include a wiring inductor formed by wiring connecting the various components, wiring within the package, and vias.

[0170] Figure 6BThis is a diagram showing the relationship between the resonant characteristics of capacitors 32 and 44 in the elastic wave filter 1B according to Modification 2 of the embodiment. As shown in Figure (b), by making the anti-resonant frequency fa32 of capacitor 32 lower than the resonant frequency fr44 of capacitor 44, compared to an elastic wave filter where the anti-resonant frequency fa32 and the resonant frequency fr44 are equal, the attenuation (insertion loss) of the bandwidth from anti-resonant frequency fa32 to resonant frequency fr44 in the transmission characteristics of elastic wave filter 1B from input / output terminal 110 to input / output terminal 120 can be greatly ensured. Furthermore, as shown in Figure (c), by making the anti-resonant frequency fa32 of capacitor 32 higher than the anti-resonant frequency fa44 of capacitor 44, compared to an elastic wave filter where the anti-resonant frequency fa32 and the resonant frequency fr44 are equal, the attenuation (insertion loss) of the bandwidth from anti-resonant frequency fa44 to anti-resonant frequency fa32 in the transmission characteristics of elastic wave filter 1B from input / output terminal 110 to input / output terminal 120 can be greatly ensured.

[0171] [6. Effects, etc.]

[0172] As described above, the elastic wave filter 1 according to the embodiment (and example) includes a parallel arm resonator 22 connected between the series arm path connecting the input and output terminals 110 and 120 and ground, a parallel arm resonator 25 connected between the series arm path and ground, a series arm resonator 12 arranged in series in the series arm path, a capacitor 32 connected in parallel with the parallel arm resonator 22, and a capacitor 35 connected in parallel with the parallel arm resonator 25. The parallel arm resonators 22, 25 and the series arm resonator 12 are respectively included in an IDT formed on a piezoelectric substrate. Electrodes, capacitors 32 and 35 each include a pair of comb-shaped electrodes formed on a piezoelectric substrate. The IDT electrodes have a plurality of first electrode fingers arranged in parallel with each other and a set of first busbar electrodes arranged opposite each other sandwiching the plurality of first electrode fingers. The pair of comb-shaped electrodes have a plurality of second electrode fingers arranged in parallel with each other and a set of second busbar electrodes arranged opposite each other sandwiching the plurality of second electrode fingers. The extension directions of the plurality of first electrode fingers intersect the extension directions of the plurality of second electrode fingers. The anti-resonance frequency fa32 of capacitor 32 is different from the anti-resonance frequency fa35 of capacitor 35.

[0173] Therefore, the maximum impedance values ​​at the anti-resonant frequencies fa32 and fa35 are smaller than the maximum impedance values ​​when the anti-resonant frequencies fa32 and fa35 are the same. Thus, in the attenuation band of the elastic wave filter 1 at higher frequencies than the passband, spurious higher-order modes can be suppressed, thereby providing an elastic wave filter 1 with improved attenuation characteristics at higher frequencies than the passband. Furthermore, the first extension direction of the first electrode finger of the IDT electrode of the parallel arm resonator 22 intersects the second extension direction of the second electrode finger of the pair of comb electrodes of the capacitor 32. This suppresses interference between the elastic wave propagating in the parallel arm resonator 22 and the high-frequency signal propagating in the capacitor 32. Similarly, the first extension direction of the first electrode finger of the IDT electrode of the parallel arm resonator 25 intersects the second extension direction of the second electrode finger of the IDT electrode of the capacitor 35. This also suppresses interference between the elastic wave propagating in the parallel arm resonator 25 and the high-frequency signal propagating in the capacitor 35.

[0174] Furthermore, the elastic wave filter 1A according to the modified embodiment 1 includes a series arm resonator 12 arranged in series in the series arm path connecting the input and output terminals 110 and 120, a series arm resonator 14 arranged in series in the series arm path, a parallel arm resonator 23 connected between the series arm path and ground, a capacitor 44 connected in parallel with the series arm resonator 12, and a capacitor 44 connected in parallel with the series arm resonator 14. The series arm resonators 12, 14 and the parallel arm resonator 23 each include an IDT electrode formed on a piezoelectric substrate. Capacitors 42 and 44 each include a pair of comb-shaped electrodes formed on a piezoelectric substrate. Each IDT electrode has a plurality of first electrode fingers arranged parallel to each other and a set of first busbar electrodes arranged opposite each other, sandwiching the plurality of first electrode fingers. The pair of comb-shaped electrodes also have a plurality of second electrode fingers arranged parallel to each other and a set of second busbar electrodes arranged opposite each other, sandwiching the plurality of second electrode fingers. The extension directions of the plurality of first electrode fingers intersect the extension directions of the plurality of second electrode fingers. The resonant frequency fr42 of capacitor 42 is different from the resonant frequency fr44 of capacitor 44. Furthermore, the first extension direction of the first electrode fingers of the IDT electrode of the series arm resonator 12 intersects the second extension direction of the second electrode fingers of the pair of comb-shaped electrodes of capacitor 42. This suppresses interference between the elastic wave propagating in the series arm resonator 12 and the high-frequency signal propagating in capacitor 42. Additionally, the first extension direction of the first electrode fingers of the IDT electrode of the series arm resonator 14 intersects the second extension direction of the second electrode fingers of the pair of comb-shaped electrodes of capacitor 44. Therefore, it is possible to suppress the interference between the elastic wave propagating in the series arm resonator 14 and the high-frequency signal propagating in the capacitor 44.

[0175] Therefore, the minimum impedance at each of the resonant frequencies fr42 and fr44 is greater than the minimum impedance when the resonant frequencies fr42 and fr44 are the same. Thus, in the attenuation band of the elastic wave filter 1A at higher frequencies than the passband, spurious higher-order modes can be suppressed, thereby providing an elastic wave filter 1A with improved attenuation characteristics at higher frequencies than the passband.

[0176] Furthermore, the elastic wave filter 1B according to the modified embodiment 2 includes a series arm resonator 14 disposed in a series arm path connecting the input and output terminals 110 and 120, a parallel arm resonator 22 connected between the series arm path and ground, a series arm resonator 12 disposed in series in the series arm path or a parallel arm resonator 23 connected between the series arm path and ground, a capacitor 44 connected in parallel with the series arm resonator 14, and a capacitor 32 connected in parallel with the parallel arm resonator 22. The series arm resonator 14, the parallel arm resonator 22, and the series arm resonator 12 or the parallel arm resonator 23 are respectively included in an ID formed on a piezoelectric substrate. The IDT electrode, capacitors 44 and 32 respectively include a pair of comb-shaped electrodes formed on a piezoelectric substrate. The IDT electrode has a plurality of first electrode fingers arranged in parallel with each other and a set of first busbar electrodes arranged opposite each other sandwiching the plurality of first electrode fingers. The pair of comb-shaped electrodes has a plurality of second electrode fingers arranged in parallel with each other and a set of second busbar electrodes arranged opposite each other sandwiching the plurality of second electrode fingers. The extension directions of the plurality of first electrode fingers intersect the extension directions of the plurality of second electrode fingers. The anti-resonance frequency fa32 of capacitor 32 is smaller than the resonance frequency fr44 of capacitor 44, or the anti-resonance frequency fa32 of capacitor 32 is larger than the anti-resonance frequency fa44 of capacitor 44.

[0177] Therefore, by making the anti-resonant frequency fa32 of capacitor 32 lower than the resonant frequency fr44 of capacitor 44, compared to an elastic wave filter where the anti-resonant frequency fa32 and the resonant frequency fr44 are equal, the attenuation (insertion loss) of the bandwidth from anti-resonant frequency fa32 to resonant frequency fr44 in the transmission characteristics of elastic wave filter 1B from input / output terminal 110 to input / output terminal 120 can be significantly ensured. Furthermore, by making the anti-resonant frequency fa32 of capacitor 32 higher than the anti-resonant frequency fa44 of capacitor 44, compared to an elastic wave filter where the anti-resonant frequency fa32 and the resonant frequency fr44 are equal, the attenuation (insertion loss) of the bandwidth from anti-resonant frequency fa44 to anti-resonant frequency fa32 in the transmission characteristics of elastic wave filter 1B from input / output terminal 110 to input / output terminal 120 can be significantly ensured. Therefore, in the attenuation band of the elastic wave filter 1B at higher frequencies than the passband, spurious signals of higher-order modes can be suppressed, thus providing an elastic wave filter 1B with improved attenuation characteristics at higher frequencies than the passband. Furthermore, the first extension direction of the first electrode finger of the IDT electrode of the series arm resonator 14 intersects the second extension direction of the second electrode finger of the pair of comb electrodes of the capacitor 44. This suppresses interference between the elastic wave propagating in the series arm resonator 14 and the high-frequency signal propagating in the capacitor 44. Similarly, the first extension direction of the first electrode finger of the IDT electrode of the parallel arm resonator 22 intersects the second extension direction of the second electrode finger of the pair of comb electrodes of the capacitor 32. This also suppresses interference between the elastic wave propagating in the parallel arm resonator 22 and the high-frequency signal propagating in the capacitor 32.

[0178] Furthermore, in the elastic wave filter 1 involved in the implementation method (and embodiment), the IDT electrode has a plurality of first electrode fingers arranged in parallel with each other, and a set of first bus bar electrodes arranged opposite each other sandwiching the plurality of first electrode fingers. A pair of comb electrodes has a plurality of second electrode fingers arranged in parallel with each other, and a set of second bus bar electrodes arranged opposite each other sandwiching the plurality of second electrode fingers. The extension direction of the plurality of first electrode fingers intersects the extension direction of the plurality of second electrode fingers. The electrode finger spacing P32 of capacitor 32 is different from the electrode finger spacing P35 of capacitor 35.

[0179] Therefore, the maximum impedance at each of the anti-resonant frequencies fa32 and fa35 is smaller than the maximum impedance when the anti-resonant frequencies fa32 and fa35 are the same. Thus, an elastic wave filter 1 with improved attenuation characteristics at higher frequencies than the passband can be provided. Furthermore, the first extension direction of the first electrode finger of the IDT electrode of the parallel arm resonator 22 intersects the second extension direction of the second electrode finger of the pair of comb electrodes of the capacitor 32. This suppresses interference between the elastic wave propagating in the parallel arm resonator 22 and the high-frequency signal propagating in the capacitor 32. Additionally, the first extension direction of the first electrode finger of the IDT electrode of the parallel arm resonator 25 intersects the second extension direction of the second electrode finger of the IDT electrode of the capacitor 35. This also suppresses interference between the elastic wave propagating in the parallel arm resonator 25 and the high-frequency signal propagating in the capacitor 35.

[0180] Furthermore, in the elastic wave filter 1A involved in Modification Example 1, the IDT electrode has a plurality of first electrode fingers arranged in parallel with each other, and a set of first busbar electrodes arranged opposite each other sandwiching the plurality of first electrode fingers. A pair of comb electrodes has a plurality of second electrode fingers arranged in parallel with each other, and a set of second busbar electrodes arranged opposite each other sandwiching the plurality of second electrode fingers. The extension directions of the plurality of first electrode fingers intersect with the extension directions of the plurality of second electrode fingers. The electrode finger spacing P42 of capacitor 42 is different from the electrode finger spacing P44 of capacitor 44.

[0181] Therefore, the minimum impedance at each of the resonant frequencies fr42 and fr44 is greater than the minimum impedance when the resonant frequencies fr42 and fr44 are the same. Thus, an elastic wave filter 1A with improved attenuation characteristics at higher frequencies than the passband can be provided. Furthermore, the first extension direction of the first electrode finger of the IDT electrode of the series arm resonator 12 intersects the second extension direction of the second electrode finger of the pair of comb electrodes of the capacitor 42. This suppresses interference between the elastic wave propagating in the series arm resonator 12 and the high-frequency signal propagating in the capacitor 42. Similarly, the first extension direction of the first electrode finger of the IDT electrode of the series arm resonator 14 intersects the second extension direction of the second electrode finger of the pair of comb electrodes of the capacitor 44. This also suppresses interference between the elastic wave propagating in the series arm resonator 14 and the high-frequency signal propagating in the capacitor 44.

[0182] Furthermore, in the elastic wave filter 1 involved in the implementation method (and embodiment), the IDT electrode has a plurality of first electrode fingers arranged in parallel with each other, and a set of first bus bar electrodes arranged opposite each other sandwiching the plurality of first electrode fingers. A pair of comb electrodes has a plurality of second electrode fingers arranged in parallel with each other, and a set of second bus bar electrodes arranged opposite each other sandwiching the plurality of second electrode fingers. The extension direction of the plurality of first electrode fingers intersects with the extension direction of the plurality of second electrode fingers. The duty cycle D32 of the electrode fingers of capacitor 32 is different from the duty cycle D35 of the electrode fingers of capacitor 35.

[0183] Therefore, the maximum impedance at each of the anti-resonant frequencies fa32 and fa35 is smaller than the maximum impedance when the anti-resonant frequencies fa32 and fa35 are the same. Thus, an elastic wave filter 1 with improved attenuation characteristics at higher frequencies than the passband can be provided. Furthermore, the first extension direction of the first electrode finger of the IDT electrode of the parallel arm resonator 22 intersects the second extension direction of the second electrode finger of the pair of comb electrodes of the capacitor 32. This suppresses interference between the elastic wave propagating in the parallel arm resonator 22 and the high-frequency signal propagating in the capacitor 32. Additionally, the first extension direction of the first electrode finger of the IDT electrode of the parallel arm resonator 25 intersects the second extension direction of the second electrode finger of the IDT electrode of the capacitor 35. This also suppresses interference between the elastic wave propagating in the parallel arm resonator 25 and the high-frequency signal propagating in the capacitor 35.

[0184] Furthermore, in the elastic wave filter 1A involved in Modification Example 1, the IDT electrode has a plurality of first electrode fingers arranged in parallel with each other, and a set of first busbar electrodes arranged opposite each other sandwiching the plurality of first electrode fingers. A pair of comb electrodes has a plurality of second electrode fingers arranged in parallel with each other, and a set of second busbar electrodes arranged opposite each other sandwiching the plurality of second electrode fingers. The extension directions of the plurality of first electrode fingers intersect with the extension directions of the plurality of second electrode fingers. The duty cycle D42 of the electrode fingers of capacitor 42 is different from the duty cycle D44 of the electrode fingers of capacitor 44.

[0185] Therefore, the minimum impedance at each of the resonant frequencies fr42 and fr44 is greater than the minimum impedance when the resonant frequencies fr42 and fr44 are the same. Thus, an elastic wave filter 1A with improved attenuation characteristics at higher frequencies than the passband can be provided. Furthermore, the first extension direction of the first electrode finger of the IDT electrode of the series arm resonator 12 intersects the second extension direction of the second electrode finger of the pair of comb electrodes of the capacitor 42. This suppresses interference between the elastic wave propagating in the series arm resonator 12 and the high-frequency signal propagating in the capacitor 42. Similarly, the first extension direction of the first electrode finger of the IDT electrode of the series arm resonator 14 intersects the second extension direction of the second electrode finger of the pair of comb electrodes of the capacitor 44. This also suppresses interference between the elastic wave propagating in the series arm resonator 14 and the high-frequency signal propagating in the capacitor 44.

[0186] Furthermore, in the elastic wave filter 1 involved in the implementation (and embodiment), the duty cycle D32 of the electrode fingers of capacitor 32 is different from the duty cycle D35 of the electrode fingers of capacitor 35, and the electrode finger spacing P32 of capacitor 32 is different from the electrode finger spacing P35 of capacitor 35.

[0187] Therefore, the anti-resonance frequency fa32 of capacitor 32 can be made to be different from the anti-resonance frequency fa35 of capacitor 35 with high precision. Thus, the degradation of the attenuation (insertion loss) of the anti-resonance frequencies fa32 and fa35 in the transmission characteristics from input / output terminal 110 to input / output terminal 120 can be suppressed with high precision.

[0188] Furthermore, in the elastic wave filter 1A involved in Modification Example 1, the electrode finger spacing P42 of capacitor 42 is different from the electrode finger spacing P44 of capacitor 44, and the electrode finger duty cycle D42 of capacitor 42 is different from the electrode finger duty cycle D44 of capacitor 44.

[0189] Therefore, the resonant frequency fr42 of capacitor 42 can be made to be different from the resonant frequency fr44 of capacitor 44 with high precision. Thus, the degradation of the attenuation (insertion loss) of the resonant frequencies fr42 and fr44 in the transmission characteristics from input / output terminal 110 to input / output terminal 120 can be suppressed with high precision.

[0190] Additionally, for example, in the elastic wave filter 1, the wavelength λ32 of capacitor 32 is smaller than either the wavelength λ22 of parallel arm resonator 22 or the wavelength λ25 of parallel arm resonator 25, and the wavelength λ35 of capacitor 35 is smaller than either the wavelength λ22 of parallel arm resonator 22 or the wavelength λ25 of parallel arm resonator 25.

[0191] As a result, spurious higher-order modes caused by capacitors 32 and 35 are generated on the higher-frequency side of the passband of elastic wave filter 1.

[0192] Additionally, for example, in the elastic wave filter 1A, the wavelength λ42 of capacitor 42 is smaller than either the wavelength λ12 of series arm resonator 12 or the wavelength λ14 of series arm resonator 14, and the wavelength λ44 of capacitor 44 is smaller than either the wavelength λ12 of series arm resonator 12 or the wavelength λ14 of series arm resonator 14.

[0193] As a result, spurious higher-order modes caused by capacitors 42 and 44 are generated on the higher-frequency side of the passband of elastic wave filter 1A.

[0194] Additionally, for example, in the elastic wave filter 1B, the wavelength λ32 of capacitor 32 is smaller than either the wavelength λ22 of parallel arm resonator 22 or the wavelength λ14 of series arm resonator 14, and the wavelength λ44 of capacitor 44 is smaller than either the wavelength λ22 of parallel arm resonator 22 or the wavelength λ14 of series arm resonator 14.

[0195] As a result, spurious higher-order modes caused by capacitors 32 and 44 are generated on the higher-frequency side of the passband of elastic wave filter 1B.

[0196] In addition, for example, in the elastic wave filter 1, no capacitor element is connected in parallel to the series arm resonators 11 to 15.

[0197] Additionally, for example, in the elastic wave filter 1A, no capacitor element is connected in parallel to the parallel arm resonators 21 to 26.

[0198] Additionally, for example, in the elastic wave filter 1B, no capacitor element is connected in parallel to the series arm resonators 11-13 and 15 or the parallel arm resonators 21 and 23-26.

[0199] Additionally, for example, in elastic wave filters 1, 1A, and 1B, the substrate includes: a piezoelectric layer 53 with IDT electrodes disposed thereon; a support substrate; a low-velocity layer 52 disposed between the piezoelectric layer 53 and the support substrate, wherein the velocity of the bulk wave is lower than that of the bulk wave propagating in the piezoelectric layer 53; and a high-velocity layer disposed between the low-velocity layer 52 and the support substrate, wherein the velocity of the propagating bulk wave is higher than that of the elastic wave propagating in the piezoelectric layer 53.

[0200] Therefore, a high-Q elastic wave resonator can be constructed. Thus, using this elastic wave resonator, elastic wave filters 1, 1A, and 1B with low insertion loss can be constructed.

[0201] Additionally, for example, in elastic wave filters 1, 1A, and 1B, the substrate includes lithium niobate or lithium tantalate, and an IDT electrode is disposed on the first main surface of the substrate. The elastic wave filters 1, 1A, and 1B also include a dielectric layer 58 disposed on the first main surface to cover the IDT electrode.

[0202] Therefore, it is possible to provide broadband elastic wave filters 1, 1A and 1B that utilize Rayleigh waves, Rough waves, leaky waves or Lamb waves.

[0203] Additionally, for example, in elastic wave filters 1, 1A, and 1B, the substrate includes a first piezoelectric layer and a second piezoelectric layer, with the IDT electrode of the first elastic wave resonator and a pair of comb electrodes of the first capacitor element formed on the first piezoelectric layer, and the IDT electrode of the second elastic wave resonator and a pair of comb electrodes of the second capacitor element formed on the second piezoelectric layer.

[0204] Furthermore, for example, in elastic wave filters 1, 1A, and 1B, the substrate includes a first piezoelectric layer and a second piezoelectric layer. The IDT electrode of the first elastic wave resonator and a pair of comb-shaped electrodes of the first capacitor element are formed in the first piezoelectric layer, and the IDT electrode of the second elastic wave resonator and a pair of comb-shaped electrodes of the second capacitor element are formed in the second piezoelectric layer. The thickness of the first piezoelectric layer is different from the thickness of the second piezoelectric layer. (Other variations, etc.)

[0205] The elastic wave device has been described above with examples of embodiments, examples, and modifications, but the elastic wave device of the present invention is not limited to the above-described embodiments, examples, and modifications. Other embodiments implemented by combining any of the constituent elements in the above-described embodiments, examples, and modifications, modifications obtained by implementing various modifications of the above-described embodiments, examples, and modifications as conceived by those skilled in the art without departing from the spirit of the present invention, and various devices incorporating the elastic wave device involved in the above-described embodiments, examples, and modifications are also included in the present invention.

[0206] The following describes the features of the elastic wave device based on the above-described embodiments, examples, and variations.

[0207] <1>

[0208] An elastic wave device, comprising:

[0209] A first elastic wave resonator is connected between the series arm path that connects the first input / output terminal and the second input / output terminal and ground;

[0210] The second elastic wave resonator is connected between the series arm path and the ground;

[0211] The third elastic wave resonator is arranged in series in the path of the series arm;

[0212] A first capacitor element, which is connected in parallel with the first elastic wave resonator; and

[0213] The second capacitor element is connected in parallel with the second elastic wave resonator.

[0214] The first elastic wave resonator, the second elastic wave resonator, and the third elastic wave resonator each include an IDT electrode formed on a piezoelectric substrate.

[0215] The first capacitor element and the second capacitor element each include a pair of comb-shaped electrodes formed on the substrate.

[0216] The IDT electrode has:

[0217] Multiple first electrode fingers arranged in parallel with each other; and

[0218] The plurality of first electrodes are sandwiched between a group of first busbar electrodes arranged in an opposing configuration.

[0219] The pair of comb-shaped electrodes have:

[0220] Multiple second electrode fingers arranged in parallel with each other; and

[0221] The plurality of second electrodes are sandwiched between a group of second busbar electrodes arranged in an opposing configuration.

[0222] The extension directions of the plurality of first electrode fingers intersect the extension directions of the plurality of second electrode fingers.

[0223] The anti-resonance frequency of the first capacitor element is different from that of the second capacitor element.

[0224] <2>

[0225] An elastic wave device, comprising:

[0226] A first elastic wave resonator is configured in series in the series arm path that connects the first input / output terminal and the second input / output terminal;

[0227] The second elastic wave resonator is arranged in series in the path of the series arm;

[0228] The third elastic wave resonator is connected between the series arm path and the ground;

[0229] A first capacitor element, which is connected in parallel with the first elastic wave resonator; and

[0230] The second capacitor element is connected in parallel with the second elastic wave resonator.

[0231] The first elastic wave resonator, the second elastic wave resonator, and the third elastic wave resonator each include an IDT electrode formed on a piezoelectric substrate.

[0232] The first capacitor element and the second capacitor element each include a pair of comb-shaped electrodes formed on the substrate.

[0233] The IDT electrode has:

[0234] Multiple first electrode fingers arranged in parallel with each other; and

[0235] The plurality of first electrodes are sandwiched between a group of first busbar electrodes arranged in an opposing configuration.

[0236] The pair of comb-shaped electrodes have:

[0237] Multiple second electrode fingers arranged in parallel with each other; and

[0238] The plurality of second electrodes are sandwiched between a group of second busbar electrodes arranged in an opposing configuration.

[0239] The extension directions of the plurality of first electrode fingers intersect the extension directions of the plurality of second electrode fingers.

[0240] The resonant frequency of the first capacitor element is different from that of the second capacitor element.

[0241] <3>

[0242] An elastic wave device, comprising:

[0243] A first elastic wave resonator is configured in series in the series arm path that connects the first input / output terminal and the second input / output terminal;

[0244] The second elastic wave resonator is connected between the series arm path and the ground;

[0245] The third elastic wave resonator is configured in series in the series arm path, or connected between the series arm path and ground;

[0246] A first capacitor element, which is connected in parallel with the first elastic wave resonator; and

[0247] The second capacitor element is connected in parallel with the second elastic wave resonator.

[0248] The first elastic wave resonator, the second elastic wave resonator, and the third elastic wave resonator each include an IDT electrode formed on a piezoelectric substrate.

[0249] The first capacitor element and the second capacitor element each include a pair of comb-shaped electrodes formed on the substrate.

[0250] The IDT electrode has:

[0251] Multiple first electrode fingers arranged in parallel with each other; and

[0252] The plurality of first electrodes are sandwiched between a group of first busbar electrodes arranged in an opposing configuration.

[0253] The pair of comb-shaped electrodes have:

[0254] Multiple second electrode fingers arranged in parallel with each other; and

[0255] The plurality of second electrodes are sandwiched between a group of second busbar electrodes arranged in an opposing configuration.

[0256] The extension directions of the plurality of first electrode fingers intersect the extension directions of the plurality of second electrode fingers.

[0257] The anti-resonant frequency of the second capacitor element is smaller than the resonant frequency of the first capacitor element, or the anti-resonant frequency of the second capacitor element is larger than the anti-resonant frequency of the first capacitor element.

[0258] <4>

[0259] An elastic wave device, comprising:

[0260] The first elastic wave harmonic oscillator, the second elastic wave harmonic oscillator, and the third elastic wave harmonic oscillator;

[0261] The first capacitor element connected in parallel with the first elastic wave resonator; and

[0262] The second capacitor element is connected in parallel with the second elastic wave resonator.

[0263] The first and second elastic wave resonators are connected in series in a series arm path that connects the first and second input / output terminals, and the third elastic wave resonator is connected between the series arm path and ground. Alternatively, the first and second elastic wave resonators are connected between the series arm path and ground, and the third elastic wave resonator is connected in series in the series arm path.

[0264] The first elastic wave resonator, the second elastic wave resonator, and the third elastic wave resonator each include an IDT electrode formed on a piezoelectric substrate.

[0265] The first capacitor element and the second capacitor element each include a pair of comb-shaped electrodes formed on the substrate.

[0266] The IDT electrode has:

[0267] Multiple first electrode fingers arranged in parallel with each other; and

[0268] The plurality of first electrodes are sandwiched between a group of first busbar electrodes arranged in an opposing configuration.

[0269] The pair of comb-shaped electrodes have:

[0270] Multiple second electrode fingers arranged in parallel with each other; and

[0271] The plurality of second electrodes are sandwiched between a group of second busbar electrodes arranged in an opposing configuration.

[0272] The extension directions of the plurality of first electrode fingers intersect the extension directions of the plurality of second electrode fingers.

[0273] The electrode finger spacing of the first capacitor element is different from that of the second capacitor element.

[0274] <5>

[0275] An elastic wave device, comprising:

[0276] The first elastic wave harmonic oscillator, the second elastic wave harmonic oscillator, and the third elastic wave harmonic oscillator;

[0277] The first capacitor element connected in parallel with the first elastic wave resonator; and

[0278] The second capacitor element is connected in parallel with the second elastic wave resonator.

[0279] The first and second elastic wave resonators are connected in series in a series arm path that connects the first and second input / output terminals, and the third elastic wave resonator is connected between the series arm path and ground. Alternatively, the first and second elastic wave resonators are connected between the series arm path and ground, and the third elastic wave resonator is connected in series in the series arm path.

[0280] The first elastic wave resonator, the second elastic wave resonator, and the third elastic wave resonator each include an IDT electrode formed on a piezoelectric substrate.

[0281] The first capacitor element and the second capacitor element each include a pair of comb-shaped electrodes formed on the substrate.

[0282] The IDT electrode has:

[0283] Multiple first electrode fingers arranged in parallel with each other; and

[0284] The plurality of first electrodes are sandwiched between a group of first busbar electrodes arranged in an opposing configuration.

[0285] The pair of comb-shaped electrodes have:

[0286] Multiple second electrode fingers arranged in parallel with each other; and

[0287] The plurality of second electrodes are sandwiched between a group of second busbar electrodes arranged in an opposing configuration.

[0288] The extension directions of the plurality of first electrode fingers intersect the extension directions of the plurality of second electrode fingers.

[0289] The duty cycle of the electrode fingers of the first capacitor element is different from that of the electrode fingers of the second capacitor element.

[0290] <6>

[0291] According to the elastic wave device described in <5>, in which,

[0292] The electrode finger spacing of the first capacitor element is different from that of the second capacitor element.

[0293] <7>

[0294] According to any one of <1> to <6>, the elastic wave device described therein,

[0295] The electrode finger spacing of the first capacitor element is smaller than either the electrode finger spacing of the first elastic wave resonator or the electrode finger spacing of the second elastic wave resonator, and...

[0296] The distance between the electrodes of the second capacitor element is smaller than either the distance between the electrodes of the first elastic wave resonator or the distance between the electrodes of the second elastic wave resonator.

[0297] <8>

[0298] According to any one of <1> to <7>, the elastic wave device described therein,

[0299] The third elastic wave resonator does not have a capacitor element connected in parallel.

[0300] <9>

[0301] According to any one of <1> to <8>, the elastic wave device described therein,

[0302] The substrate includes:

[0303] A piezoelectric layer having the IDT electrodes disposed thereon;

[0304] support base plate;

[0305] A low-velocity sound layer, disposed between the piezoelectric layer and the supporting substrate, wherein the sound velocity of bulk waves is lower than that of bulk waves propagating in the piezoelectric layer; and

[0306] A high-velocity sound layer, disposed between the low-velocity sound layer and the support substrate, wherein the propagating volume wave sound velocity is higher than the elastic wave sound velocity propagating in the piezoelectric layer.

[0307] <10>

[0308] According to any one of <1> to <8>, the elastic wave device described therein,

[0309] The substrate includes lithium niobate or lithium tantalate.

[0310] The IDT electrode is disposed on the first main surface of the substrate.

[0311] The elastic wave device further includes a dielectric layer disposed on the first main surface to cover the IDT electrode.

[0312] <11>

[0313] According to any one of <1> to <10>, the elastic wave device described therein,

[0314] The substrate includes a first piezoelectric layer and a second piezoelectric layer.

[0315] The IDT electrode of the first elastic wave resonator and the pair of comb electrodes of the first capacitor element are formed on the first piezoelectric layer.

[0316] The IDT electrode of the second elastic wave resonator and the pair of comb electrodes of the second capacitor element are formed on the second piezoelectric layer.

[0317] <12>

[0318] According to the elastic wave device described in <3>, in which,

[0319] The substrate includes a first piezoelectric layer and a second piezoelectric layer.

[0320] The IDT electrode of the first elastic wave resonator and the pair of comb electrodes of the first capacitor element are formed on the first piezoelectric layer.

[0321] The IDT electrode of the second elastic wave resonator and the pair of comb electrodes of the second capacitor element are formed on the second piezoelectric layer.

[0322] The thickness of the first piezoelectric layer is different from the thickness of the second piezoelectric layer.

[0323] Industrial utilization

[0324] This invention, as a low-loss and high-attenuation elastic wave filter applicable to multi-band frequency standards, can be widely used in communication devices such as portable telephones.

[0325] Explanation of reference numerals in the attached figures

[0326] 1. 1A, 1B Elastic Wave Filters;

[0327] Series arm harmonic oscillators 11, 12, 13, 14, and 15;

[0328] Parallel arm harmonic oscillators: 21, 22, 23, 24, 25, 26;

[0329] 32, 35, 42, 44 capacitors;

[0330] 50 Piezoelectric substrate;

[0331] 51 High-speed acoustic support substrate;

[0332] 52 Low-sound-velocity layer;

[0333] 53. Piezoelectric layer;

[0334] 54 IDT electrodes;

[0335] 55. Protective layer;

[0336] 57. Piezoelectric single-crystal substrate;

[0337] 58. Dielectric layer;

[0338] 59. Adjustment membrane;

[0339] 60a and 60b comb-shaped electrodes;

[0340] Electrode fingers 61a, 61b, 71a, and 71b;

[0341] Busbar electrodes 62a, 62b, 72a, and 72b;

[0342] 110 and 120 input / output terminals;

[0343] 540 tightly sealed layer;

[0344] 542 Main electrode layer;

[0345] Anti-resonant frequencies of fa32, fa35, fa44, fa320, and fa350;

[0346] The resonant frequencies of fr42 and fr44;

[0347] n1, n2, n3, n4 are connection nodes;

[0348] Wavelengths of λ32, λ35, λ42, and λ44.

Claims

1. An elastic wave device, comprising: A first elastic wave resonator is connected between the series arm path that connects the first input / output terminal and the second input / output terminal and ground; The second elastic wave resonator is connected between the series arm path and the ground; The third elastic wave resonator is arranged in series in the path of the series arm; A first capacitor element, which is connected in parallel with the first elastic wave resonator; and The second capacitor element is connected in parallel with the second elastic wave resonator. The first elastic wave resonator, the second elastic wave resonator, and the third elastic wave resonator each include an IDT electrode, i.e., an interdigital transducer electrode, formed on a piezoelectric substrate. The first capacitor element and the second capacitor element each include a pair of comb-shaped electrodes formed on the substrate. The IDT electrode has: Multiple first electrode fingers arranged in parallel with each other; and The plurality of first electrodes are sandwiched between a group of first busbar electrodes arranged in an opposing configuration. The pair of comb-shaped electrodes have: Multiple second electrode fingers arranged in parallel with each other; and The plurality of second electrodes are sandwiched between a group of second busbar electrodes arranged in an opposing configuration. The extension directions of the plurality of first electrode fingers intersect the extension directions of the plurality of second electrode fingers. The anti-resonance frequency of the first capacitor element is different from that of the second capacitor element.

2. An elastic wave device, comprising: A first elastic wave resonator is configured in series in the series arm path that connects the first input / output terminal and the second input / output terminal; The second elastic wave resonator is arranged in series in the path of the series arm; The third elastic wave resonator is connected between the series arm path and the ground; A first capacitor element, which is connected in parallel with the first elastic wave resonator; and The second capacitor element is connected in parallel with the second elastic wave resonator. The first elastic wave resonator, the second elastic wave resonator, and the third elastic wave resonator each include an IDT electrode formed on a piezoelectric substrate. The first capacitor element and the second capacitor element each include a pair of comb-shaped electrodes formed on the substrate. The IDT electrode has: Multiple first electrode fingers arranged in parallel with each other; and The plurality of first electrodes are sandwiched between a group of first busbar electrodes arranged in an opposing configuration. The pair of comb-shaped electrodes have: Multiple second electrode fingers arranged in parallel with each other; as well as The plurality of second electrodes are sandwiched between a group of second busbar electrodes arranged in an opposing configuration. The extension directions of the plurality of first electrode fingers intersect the extension directions of the plurality of second electrode fingers. The resonant frequency of the first capacitor element is different from that of the second capacitor element.

3. An elastic wave device, comprising: A first elastic wave resonator is configured in series in the series arm path that connects the first input / output terminal and the second input / output terminal; The second elastic wave resonator is connected between the series arm path and the ground; The third elastic wave resonator is configured in series in the series arm path, or connected between the series arm path and ground; A first capacitor element, which is connected in parallel with the first elastic wave resonator; and The second capacitor element is connected in parallel with the second elastic wave resonator. The first elastic wave resonator, the second elastic wave resonator, and the third elastic wave resonator each include an IDT electrode formed on a piezoelectric substrate. The first capacitor element and the second capacitor element each include a pair of comb-shaped electrodes formed on the substrate. The IDT electrode has: Multiple first electrode fingers arranged in parallel with each other; and The plurality of first electrodes are sandwiched between a group of first busbar electrodes arranged in an opposing configuration. The pair of comb-shaped electrodes have: Multiple second electrode fingers arranged in parallel with each other; and The plurality of second electrodes are sandwiched between a group of second busbar electrodes arranged in an opposing configuration. The extension directions of the plurality of first electrode fingers intersect the extension directions of the plurality of second electrode fingers. The anti-resonant frequency of the second capacitor element is smaller than the resonant frequency of the first capacitor element, or the anti-resonant frequency of the second capacitor element is larger than the anti-resonant frequency of the first capacitor element.

4. An elastic wave device, comprising: The first elastic wave harmonic oscillator, the second elastic wave harmonic oscillator, and the third elastic wave harmonic oscillator; The first capacitor element connected in parallel with the first elastic wave resonator; and The second capacitor element is connected in parallel with the second elastic wave resonator. The first and second elastic wave resonators are connected in series in a series arm path that connects the first and second input / output terminals, and the third elastic wave resonator is connected between the series arm path and ground. Alternatively, the first and second elastic wave resonators are connected between the series arm path and ground, and the third elastic wave resonator is connected in series in the series arm path. The first elastic wave resonator, the second elastic wave resonator, and the third elastic wave resonator each include an IDT electrode formed on a piezoelectric substrate. The first capacitor element and the second capacitor element each include a pair of comb-shaped electrodes formed on the substrate. The IDT electrode has: Multiple first electrode fingers arranged in parallel with each other; and The plurality of first electrodes are sandwiched between a group of first busbar electrodes arranged in an opposing configuration. The pair of comb-shaped electrodes have: Multiple second electrode fingers arranged in parallel with each other; and The plurality of second electrodes are sandwiched between a group of second busbar electrodes arranged in an opposing configuration. The extension directions of the plurality of first electrode fingers intersect the extension directions of the plurality of second electrode fingers. The electrode finger spacing of the first capacitor element is different from that of the second capacitor element.

5. An elastic wave device, comprising: The first elastic wave harmonic oscillator, the second elastic wave harmonic oscillator, and the third elastic wave harmonic oscillator; The first capacitor element connected in parallel with the first elastic wave resonator; and The second capacitor element is connected in parallel with the second elastic wave resonator. The first and second elastic wave resonators are connected in series in a series arm path that connects the first and second input / output terminals, and the third elastic wave resonator is connected between the series arm path and ground. Alternatively, the first and second elastic wave resonators are connected between the series arm path and ground, and the third elastic wave resonator is connected in series in the series arm path. The first elastic wave resonator, the second elastic wave resonator, and the third elastic wave resonator each include an IDT electrode formed on a piezoelectric substrate. The first capacitor element and the second capacitor element each include a pair of comb-shaped electrodes formed on the substrate. The IDT electrode has: Multiple first electrode fingers arranged in parallel with each other; and The plurality of first electrodes are sandwiched between a group of first busbar electrodes arranged in an opposing configuration. The pair of comb-shaped electrodes have: Multiple second electrode fingers arranged in parallel with each other; and The plurality of second electrodes are sandwiched between a group of second busbar electrodes arranged in an opposing configuration. The extension directions of the plurality of first electrode fingers intersect the extension directions of the plurality of second electrode fingers. The duty cycle of the electrode fingers of the first capacitor element is different from that of the electrode fingers of the second capacitor element.

6. The elastic wave device according to claim 5, wherein, The electrode finger spacing of the first capacitor element is different from that of the second capacitor element.

7. The elastic wave device according to any one of claims 1 to 6, wherein, The electrode finger spacing of the first capacitor element is smaller than either the electrode finger spacing of the first elastic wave resonator or the electrode finger spacing of the second elastic wave resonator, and... The distance between the electrodes of the second capacitor element is smaller than either the distance between the electrodes of the first elastic wave resonator or the distance between the electrodes of the second elastic wave resonator.

8. The elastic wave device according to any one of claims 1 to 7, wherein, The third elastic wave resonator does not have a capacitor element connected in parallel.

9. The elastic wave device according to any one of claims 1 to 8, wherein, The substrate includes: A piezoelectric layer having the IDT electrodes disposed thereon; support base plate; A low-velocity sound layer, disposed between the piezoelectric layer and the supporting substrate, wherein the sound velocity of bulk waves is lower than that of bulk waves propagating in the piezoelectric layer; and A high-velocity sound layer, disposed between the low-velocity sound layer and the support substrate, wherein the propagating volume wave sound velocity is higher than the elastic wave sound velocity propagating in the piezoelectric layer.

10. The elastic wave device according to any one of claims 1 to 8, wherein, The substrate includes lithium niobate or lithium tantalate. The IDT electrode is disposed on the first main surface of the substrate. The elastic wave device further includes a dielectric layer disposed on the first main surface to cover the IDT electrode.

11. The elastic wave device according to any one of claims 1 to 10, wherein, The substrate includes a first piezoelectric layer and a second piezoelectric layer. The IDT electrode of the first elastic wave resonator and the pair of comb electrodes of the first capacitor element are formed on the first piezoelectric layer. The IDT electrode of the second elastic wave resonator and the pair of comb electrodes of the second capacitor element are formed on the second piezoelectric layer.

12. The elastic wave device according to claim 3, wherein, The substrate includes a first piezoelectric layer and a second piezoelectric layer. The IDT electrode of the first elastic wave resonator and the pair of comb electrodes of the first capacitor element are formed on the first piezoelectric layer. The IDT electrode of the second elastic wave resonator and the pair of comb electrodes of the second capacitor element are formed on the second piezoelectric layer. The thickness of the first piezoelectric layer is different from the thickness of the second piezoelectric layer.

Images