Elastic wave apparatus, elastic wave filter, and multiplexer

Abstract

The present invention provides an elastic wave filter 1 with improved attenuation characteristics. [Solution] The elastic wave filter 1 comprises a mounting substrate 80 having a main surface 80a, a piezoelectric substrate 70 having a main surface 70b facing the main surface 80a across an air gap, a series arm resonator S1 including an IDT electrode 31 and disposed on the piezoelectric substrate 70, a capacitor 11 disposed on the main surface 70b and connected in parallel to the series arm resonator S1, and a floating planar electrode 41 disposed on the main surface 80a, and when the main surface 80a and the main surface 70b are viewed from above, a region A is enclosed by the IDT electrode 31, the capacitor 11 and the wirings W1 and W2. R This overlaps with at least a portion of the floating planar electrode 41.

Description

[Technical Field]

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

[0002] Patent Document 1 discloses an elastic wave apparatus comprising a series arm resonator arranged 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 capacitive element connected between the series arm path and a second reference electrode. According to the document, this configuration can provide an elastic wave apparatus with low insertion loss and high attenuation in the high-frequency range. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2013-243570 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, in the elastic wave apparatus described in Patent Document 1, the attenuation characteristics of the elastic wave apparatus may deteriorate due to the current loop formed by the parallel arm resonator, the first reference electrode, the second reference electrode, and the capacitive element.

[0005] Therefore, the present invention has been made to solve the above problems, and aims to provide an elastic wave device, an elastic wave filter, and a multiplexer with improved attenuation characteristics. [Means for solving the problem]

[0006] To achieve the above objective, an elastic wave apparatus according to one aspect of the present invention comprises a first substrate having a first main surface, a second substrate having a second main surface facing the first main surface across an air gap, an elastic wave resonator including a functional electrode and disposed on the second substrate, a bridging capacitance element disposed on the second main surface and connected in parallel to the elastic wave resonator, and a floating electrode disposed on the first main surface, wherein when the first and second main surfaces are viewed from above, the region enclosed by the functional electrode, the bridging capacitance element, and the wiring connecting the functional electrode and the bridging capacitance element overlaps with at least a portion of the floating electrode.

[0007] Furthermore, an elastic wave filter according to one aspect of the present invention comprises a first substrate having a first main surface, a second substrate having a second main surface facing the first main surface across an air gap, a series arm resonator arranged in a series arm path connecting the first input / output terminal and the second input / output terminal, a parallel arm resonator connected between the series arm path and ground, a bridging capacitance element arranged on the second main surface and connected in parallel to one of the series arm resonator and the parallel arm resonator, and a floating electrode arranged on the first main surface, wherein one of the series arm resonator and the parallel arm resonator is an elastic wave resonator including a functional electrode, and when the first and second main surfaces are viewed in plan, the region enclosed by the functional electrode, the bridging capacitance element, and the wiring connecting the functional electrode and the bridging capacitance element overlaps with at least a part of the floating electrode.

[0008] Furthermore, a multiplexer according to one aspect of the present invention comprises a common terminal, the above-described elastic wave filter connected to the common terminal, and a first filter connected to the common terminal. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an elastic wave device, an elastic wave filter, and a multiplexer with improved attenuation characteristics. [Brief explanation of the drawing]

[0010] [Figure 1] This is a circuit diagram of an elastic wave filter according to an embodiment. [Figure 2A]It is a plan view and a cross-sectional view schematically showing a first example of an elastic wave resonator constituting an elastic wave filter according to an embodiment. [Figure 2B] It is a cross-sectional view schematically showing a second example of an elastic wave resonator constituting an elastic wave filter according to an embodiment. [Figure 2C] It is a cross-sectional view schematically showing a third example of an elastic wave resonator constituting an elastic wave filter according to an embodiment. [Figure 2D] It is a cross-sectional view schematically showing a fourth example of an elastic wave resonator constituting an elastic wave filter according to an embodiment. [Figure 3A] It is a cross-sectional view of an elastic wave filter according to an embodiment. [Figure 3B] It is a cross-sectional view of an elastic wave filter according to a comparative example. [Figure 4] It is a diagram showing an electrode layout of a series arm resonator and a bridging capacitor element of an elastic wave filter according to an embodiment. [Figure 5] It is a circuit configuration diagram of a multiplexer according to an embodiment. [Figure 6] It is a cross-sectional view of a multiplexer according to an embodiment. [Figure 7A] It is a first plan view showing an electrode layout of a multiplexer according to an embodiment. [Figure 7B] It is a second plan view showing an electrode layout of a multiplexer according to an embodiment. [Figure 7C] It is a third plan view showing an electrode layout of a multiplexer according to an embodiment. [Figure 8A] It is a graph showing the passing characteristics of an elastic wave filter included in a multiplexer according to an embodiment, Comparative Example 1, and Comparative Example 2. [Figure 8B] It is a graph showing the voltage standing wave ratio of an elastic wave filter included in a multiplexer according to an embodiment, Comparative Example 1, and Comparative Example 2. [Figure 8C] It is a graph showing the isolation characteristics of a multiplexer according to an embodiment, Comparative Example 1, and Comparative Example 2.

Embodiments for Carrying Out the Invention

[0011] The embodiments of this disclosure will be described in detail below with reference to the drawings. The embodiments described below are all general or specific examples. The numerical values, shapes, materials, components, arrangement of components, and connection configurations shown in the following embodiments are examples only and are not intended to limit the present invention.

[0012] The figures are schematic diagrams that have been appropriately emphasized, omitted, or had their proportions adjusted to illustrate the present invention, and are not necessarily strictly accurate representations. Actual shapes, positional relationships, and proportions may differ. In each figure, substantially identical components are denoted by the same reference numerals, and redundant explanations may be omitted or simplified.

[0013] In the circuit configuration of this disclosure, "connected between A and B" means connected to both A and B, including cases where it is indirectly connected to both A and B.

[0014] Furthermore, in the component arrangement of this disclosure, "component A is arranged in series with path B" means that both the signal input terminal and the signal output terminal of component A are connected between path B. Path B consists of wiring, electrodes, or terminals.

[0015] Furthermore, terms indicating relationships between elements, such as "parallel" and "perpendicular," terms indicating the shape of elements, such as "rectangle," and numerical ranges do not represent only strict meanings, but also include substantially equivalent ranges, such as errors of a few percent.

[0016] Furthermore, in this disclosure, “terminal” means the point where a conductor within an element terminates. However, if the impedance of the conductors between elements is sufficiently low, a terminal is interpreted not only as a single point, but as any point on the conductor between elements or the entire conductor.

[0017] Furthermore, in this disclosure, the passband of the filter is defined as the portion of the frequency spectrum transmitted by the filter, and is the frequency band between two frequencies that are 3 dB greater than the minimum power insertion loss.

[0018] Furthermore, the resonant frequency and anti-resonant frequency shown in the above embodiments and modifications can be derived, for example, by contacting the two input and output electrodes of the elastic wave resonator or capacitive element with an RF probe and measuring the reflection characteristics (impedance characteristics) with a network analyzer or the like, while the elastic wave resonator or capacitive element is not connected to any other circuit elements.

[0019] Furthermore, "two resonant frequencies are different" and "two anti-resonant frequencies are different" are defined as the difference between two measured resonant frequencies (or two anti-resonant frequencies) being 0.1% or more. This difference includes the error of the measuring device. Also, "one resonant frequency is greater than one anti-resonant frequency" and "one resonant frequency is smaller than one anti-resonant frequency" are defined as the measured resonant frequency being 0.1% or more greater (or less) than the measured anti-resonant frequency. The difference between the measured resonant frequency and the measured anti-resonant frequency includes the error of the measuring device.

[0020] Furthermore, in this disclosure, "band" means at least one of the uplink operating band and the downlink operating band of a frequency band predefined by a standardization body (e.g., 3GPP®, IEEE (Institute of Electrical and Electronics Engineers), etc.) for a communication system built using Radio Access Technology (RAT). In this embodiment, the communication system can be, but is not limited to, an LTE (Long Term Evolution) system, a 5G (5th Generation)-NR (New Radio) system, and a WLAN (Wireless Local Area Network) system. The uplink operating band of a frequency band means the frequency range designated for uplink use within that frequency band. The downlink operating band of a frequency band means the frequency range designated for downlink use within that frequency band.

[0021] (Embodiment) [1. Circuit configuration of an elastic wave filter] Figure 1 is a circuit diagram of an elastic wave filter 1 according to an embodiment. As shown in the figure, the elastic wave filter 1 is an example of an elastic wave device and comprises series arm resonators S1 and S2, parallel arm resonators P1 and P2, capacitors 11 and 21, and input / output terminals 101 and 102.

[0022] Each of the series arm resonators S1 and S2 includes an elastic wave resonator and is arranged in series in the series arm path connecting the input / output terminal 101 (first input / output terminal) and the input / output terminal 102 (second input / output terminal).

[0023] Each of the parallel arm resonators P1 and P2 includes an elastic wave resonator and is connected between the series arm path and ground. The parallel arm resonator P1 is connected between the connection point of the input / output terminal 101 and the series arm resonator S1 and ground. The parallel arm resonator P2 is connected between the connection point of the series arm resonators S1 and S2 and ground.

[0024] Capacitor 11 is an example of a bridging capacitance element and is connected in parallel to the series arm resonator S1. Capacitor 21 is an example of a bridging capacitance element and is connected in parallel to the parallel arm resonator P1.

[0025] The series arm resonators S1 and S2, and the parallel arm resonators P1 and P2, each have a resonant frequency at which their impedance is minimum and an anti-resonant frequency at which their impedance is maximum. By adjusting the relative heights of the resonant and anti-resonant frequencies of each resonator, it is possible to achieve the transmission characteristics required for the elastic wave filter 1.

[0026] By connecting capacitor 11 in parallel to the series arm resonator S1, the interval between the resonant frequency and the anti-resonant frequency of the series arm resonator S1 (hereinafter referred to as the resonant bandwidth) can be reduced, and the resonant Q value of the resonant circuit in which the series arm resonator S1 and capacitor 11 are connected in parallel can be increased. Furthermore, by connecting capacitor 21 in parallel to the parallel arm resonator P1, the resonant bandwidth of the parallel arm resonator P1 can be reduced, and the resonant Q value of the resonant circuit in which the parallel arm resonator P1 and capacitor 21 are connected in parallel can be increased. This makes it possible to realize an elastic wave filter 1 with improved low loss within the passband and improved steepness between the passband and the attenuation band.

[0027] The elastic wave filter 1 according to this embodiment includes at least one series arm resonator and at least one parallel arm resonator, and a bridging capacitance element is connected to at least one of the series arm resonator and the parallel arm resonator.

[0028] Furthermore, the elastic wave device according to the present invention does not have to be an elastic wave filter comprising at least one series arm resonator and at least one parallel arm resonator, but may be an elastic wave resonator comprising at least one set of elastic wave resonators and bridging capacitance elements connected in parallel with each other.

[0029] [2 Structure of elastic wave resonators and bridging capacitance elements] Next, we will illustrate the structure of the elastic wave resonators (series arm resonators and parallel arm resonators) and capacitive elements that constitute the elastic wave filter 1.

[0030] Figure 2A is a schematic plan view and cross-sectional view of a first example of an elastic wave resonator constituting the elastic wave filter 1 according to the embodiment. The figure illustrates the structure of a series arm resonator S1 among the elastic wave resonators constituting the elastic wave filter 1. Note that the series arm resonator S1 shown in Figure 2A is for illustrating a typical structure of a surface acoustic wave (SAW) resonator constituting the elastic wave filter 1, and the number and length of electrode fingers constituting the electrode are not limited thereto. Furthermore, elastic wave resonators other than the series arm resonator S1 constituting the elastic wave filter 1 have the structure of a SAW resonator shown in Figure 2A.

[0031] As shown in Figure 2A(c), the series arm resonator S1 comprises a piezoelectric substrate 70, an IDT (InterDigital Transducer) electrode 31, and a protective layer 55.

[0032] As shown in Figure 2A(a), an IDT electrode 31 is formed on the piezoelectric substrate 70. The IDT electrode 31 is an example of a functional electrode and includes a pair of comb-shaped electrodes 60a and 60b facing each other. The comb-shaped electrode 60a is composed of a plurality of electrode fingers 61a that are parallel to each other and a busbar electrode 62a that connects the plurality of electrode fingers 61a. The comb-shaped electrode 60b is composed of a plurality of electrode fingers 61b that are parallel to each other and a busbar electrode 62b that connects the plurality of electrode fingers 61b. The plurality of electrode fingers 61a and 61b are formed along a direction perpendicular to the elastic wave propagation direction (X-axis direction). The series arm resonator S1 may have reflectors at both ends of the IDT electrode 31 in the elastic wave propagation direction (X-axis direction).

[0033] As shown in Figure 2A(b), the IDT electrode 31 has a laminated structure consisting of an adhesion layer 540 and a main electrode layer 542.

[0034] The adhesion layer 540 is a layer for improving the adhesion between the piezoelectric substrate 70 and the main electrode layer 542, and is made of, for example, Ti. The main electrode layer 542 is made of, for example, Al containing 1% Cu.

[0035] The protective layer 55 is formed to cover the IDT electrode 31. The protective layer 55 is a layer intended to protect the main electrode layer 542 from the external environment, adjust the frequency-temperature characteristics, and improve moisture resistance, and is, for example, a dielectric film mainly composed of silicon dioxide.

[0036] The materials constituting the adhesion layer 540, the main electrode layer 542, and the protective layer 55 are not limited to those described above. Furthermore, the IDT electrode 31 does not have to be in the laminated structure described above. The IDT electrode 31 may be composed of a metal or alloy such as Ti, Al, Cu, Pt, Au, Ag, or Pd, or it may be composed of multiple laminates made of the above metals or alloys. Also, the protective layer 55 may not be formed.

[0037] Next, the laminated structure of the piezoelectric substrate 70 will be described.

[0038] The piezoelectric substrate 70 is an example of a second substrate, and as shown in Figure 2A(c), it comprises a support substrate 71, a low-sonic layer 72, and a piezoelectric layer 73, and has a structure in which the support substrate 71, the low-sonic layer 72, and the piezoelectric layer 73 are stacked in this order.

[0039] The piezoelectric layer 73 is made of, for example, a θ° Y-cut X-propagating LiTaO3 piezoelectric single crystal or piezoelectric ceramic (a lithium tantalate single crystal or ceramic cut by a plane whose normal axis is the axis rotated θ° from the Y axis with the X axis as the central axis, and in which surface acoustic waves propagate in the X-axis direction). The material of the piezoelectric single crystal used as the piezoelectric layer 73 and the cut angle θ are appropriately selected according to the requirements of each filter.

[0040] The support substrate 71 is a substrate that supports the low-sound-velocity layer 72, the piezoelectric layer 73, and the IDT electrode 31. Furthermore, the support substrate 71 is a substrate in which the sound velocity of bulk waves within the support substrate 71 is faster than that of elastic waves such as surface waves and boundary waves propagating through the piezoelectric layer 73, and functions to confine the acoustic surface waves in the portion where the piezoelectric layer 73 and the low-sound-velocity layer 72 are stacked, preventing them from leaking below the support substrate 71. As the material for the support substrate 71, for example, piezoelectric materials such as aluminum nitride, lithium tantalate, lithium niobate, and quartz; ceramics such as alumina, sapphire, magnesia, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, forsterite, spinel, and sialon; dielectrics such as aluminum oxide, silicon oxynitride, DLC (diamond-like carbon), and diamond; or semiconductors such as silicon; or materials mainly composed of the above materials can be used. The spinel mentioned above includes aluminum compounds containing one or more elements selected from Mg, Fe, Zn, Mn, etc., and oxygen. Examples of spinel include MgAl2O4, FeAl2O4, ZnAl2O4, and MnAl2O4.

[0041] The low-sound-velocity layer 72 is a film in which the sound velocity of bulk waves propagating through the piezoelectric layer 73 is lower than that of bulk waves propagating through the piezoelectric layer 73, and is positioned between the piezoelectric layer 73 and the support substrate 71. Due to this structure and the property that elastic waves concentrate energy in a medium with an inherently low sound velocity, leakage of surface acoustic wave energy to the piezoelectric layer 73 is suppressed. As the material for the low-sound-velocity layer 72, for example, dielectric materials such as glass, silicon oxide, silicon oxynitride, lithium oxide, tantalum oxide, or compounds of silicon oxide to which fluorine, carbon, or boron have been added, or materials mainly composed of the above materials can be used.

[0042] Furthermore, the above-described laminated structure of the piezoelectric substrate 70 makes it possible to significantly increase the Q factor at the resonant and anti-resonant frequencies compared to conventional structures using a single layer of piezoelectric substrate. In other words, it is possible to construct an elastic wave resonator with a high Q factor, and using this elastic wave resonator, it becomes possible to construct an elastic wave filter with low insertion loss.

[0043] The support substrate 71 may have a structure in which a first support substrate and a high-speed film are laminated together, the high-speed film having a sound velocity of bulk waves propagating faster than the elastic waves such as surface waves and boundary waves propagating through the piezoelectric layer 73. In this case, the same material as the support substrate 71 can be used as the material for the high-speed film. As for the material of the first support substrate, for example, piezoelectric materials such as aluminum nitride, lithium tantalate, lithium niobate, and quartz; ceramics such as alumina, sapphire, magnesia, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, and forsterite; dielectrics such as diamond and glass; semiconductors such as silicon and gallium nitride; or resins; or materials mainly composed of the above materials can be used.

[0044] In this specification, "main component of the material" refers to a component that accounts for more than 50% by weight of the material. The main component may exist in one of the following states: single crystal, polycrystalline, or amorphous, or in a mixture thereof.

[0045] In the series arm resonator S1 shown in Figure 2A(c), the piezoelectric substrate 70 may be a piezoelectric single crystal substrate, for example, a piezoelectric single crystal of lithium niobate or lithium tantalate.

[0046] Figure 2B is a schematic cross-sectional view showing a second example of an elastic wave resonator constituting the elastic wave filter 1 according to the embodiment. The figure illustrates the structure of a series arm resonator S1A, which is a modified version of the series arm resonator S1 constituting the elastic wave filter 1. Note that elastic wave resonators other than the series arm resonator S1 constituting the elastic wave filter 1 may have the structure of a laterally excited film bulk acoustic resonator (XBAR) as shown in Figure 2B.

[0047] As shown in Figure 2B, the series arm resonator S1A comprises a piezoelectric substrate 70A and an IDT electrode 31. The series arm resonator S1A in this example has a different configuration of the piezoelectric substrate 70A compared to the series arm resonator S1 in the first example. Therefore, the following description will focus on the configuration of the piezoelectric substrate 70A of the series arm resonator S1A in this example, which differs from that of the series arm resonator S1 in the first example.

[0048] The piezoelectric substrate 70A is an example of a second substrate and consists of a support substrate 71, a low-sonic layer 72, a piezoelectric layer 73, and an IDT electrode 31. The IDT electrode 31 is placed on the piezoelectric layer 73. The support substrate 71, the low-sonic layer 72, and the piezoelectric layer 73 are stacked in this order. When the piezoelectric layer 73 is viewed from above, a gap 150 is provided between the piezoelectric layer 73 and the support substrate 71 in the region that overlaps with the IDT electrode 31. The series arm resonator S1A constitutes an XBAR.

[0049] The piezoelectric layer 73 consists of, for example, a θ° Y-cut X-propagating LiTaO3 piezoelectric single crystal or piezoelectric ceramic, or a θ° Y-cut X-propagating LiNbO3 piezoelectric single crystal or piezoelectric ceramic. The material of the piezoelectric single crystal used as the piezoelectric layer 73 and the cut angle θ are appropriately selected according to the requirements of each filter.

[0050] The support substrate 71 is a substrate that supports the low-sonic layer 72, the piezoelectric layer 73, and the IDT electrode 31.

[0051] The laminated structure of the piezoelectric substrate 70A described above makes it possible to significantly increase the Q factor at the resonant and anti-resonant frequencies compared to conventional structures using a single layer of piezoelectric substrate. In other words, it is possible to construct an elastic wave resonator with a high Q factor, and using this elastic wave resonator, it becomes possible to construct an elastic wave filter with low insertion loss.

[0052] Figure 2C is a schematic cross-sectional view showing a third example of an elastic wave resonator constituting the elastic wave filter 1 according to the embodiment. The figure illustrates the structure of a series arm resonator S1B, which is a modified version of the series arm resonator S1 constituting the elastic wave filter 1. Note that the series arm resonator S1B shown in Figure 2C is intended to illustrate a typical structure of a bulk elastic wave (BAW) resonator constituting the elastic wave filter 1, and the shape and thickness of the planar electrode 66, piezoelectric layer 67, planar electrode 68, and support substrate 65 are not limited thereto. Furthermore, elastic wave resonators other than the series arm resonator S1 constituting the elastic wave filter 1 may have the structure of the BAW resonator shown in Figure 2C.

[0053] As shown in Figure 2C, the series-arm resonator S1B includes planar electrodes 66 and 68 and a piezoelectric layer 67. Planar electrode 66 is an example of a first planar electrode, and planar electrode 68 is an example of a second planar electrode. Planar electrode 66, piezoelectric layer 67, and planar electrode 68 are examples of functional electrodes and are arranged in this order from the support substrate 65 to form a laminate. The support substrate 65 is an example of a second substrate and is configured to be non-contact with the central region of the planar electrode 66. In Figure 2C, a gap 150 is formed in the support substrate 65 to achieve a non-contact configuration between the support substrate 65 and the central region of the planar electrode 66. Alternatively, to achieve a non-contact configuration between the support substrate 65 and the central region of the planar electrode 66, no gap may be formed in the support substrate 65, and a gap may be formed at the interface between the support substrate 65 and the laminate.

[0054] The piezoelectric layer 67 is composed of, for example, a piezoelectric single crystal of lithium niobate or lithium tantalate. Alternatively, the piezoelectric layer 67 may be composed of, for example, AlN (aluminum nitride) or ScAlN. The piezoelectric layer 67 may have its laminated structure, material, cut angle, and thickness changed as appropriate depending on the required transmission characteristics of the elastic wave filter 1.

[0055] In the above configuration, when a high-frequency signal is applied between the planar electrode 66 and the planar electrode 68, a potential difference is generated between the two electrodes, causing the piezoelectric layer 67 to distort and generating bulk elastic waves in the stacking direction. By setting the thickness of the piezoelectric layer 67 to correspond to the passband of the elastic wave filter 1, an elastic wave filter 1 with desired transmission characteristics can be realized.

[0056] Figure 2D is a schematic cross-sectional view showing a fourth example of an elastic wave resonator constituting the elastic wave filter 1 according to the embodiment. The figure illustrates the structure of a series arm resonator S1C, which is a modified version of the series arm resonator S1 constituting the elastic wave filter 1. Note that the series arm resonator S1C shown in Figure 2D is intended to illustrate a typical structure of an SMR (Solidly Mounted Resonator) type BAW resonator constituting the elastic wave filter 1, and the shape and thickness of the planar electrode 66, piezoelectric layer 67, planar electrode 68, support substrate 65, and acoustic multilayer film are not limited thereto. Furthermore, elastic wave resonators other than the series arm resonator S1 constituting the elastic wave filter 1 may have the structure of an SMR type BAW resonator shown in Figure 2D.

[0057] As shown in Figure 2D, the series arm resonator S1C includes planar electrodes 66 and 68, a piezoelectric layer 67, a low acoustic impedance layer 161, a high acoustic impedance layer 162, and a support substrate 65. Planar electrode 66 is an example of a first planar electrode, and planar electrode 68 is an example of a second planar electrode. Planar electrode 66, piezoelectric layer 67, and planar electrode 68 are examples of functional electrodes and are arranged in this order from the support substrate 65 to form a laminate. The support substrate 65 is an example of a second substrate and supports the laminate. Between the laminate and the support substrate 65, an acoustic multilayer film is arranged having a structure in which the low acoustic impedance layer 161 and the high acoustic impedance layer 162 are alternately laminated. With this structure, the series arm resonator S1C constitutes an SMR-type BAW resonator and confines bulk elastic waves above the acoustic multilayer film by utilizing Bragg reflection by the acoustic multilayer film.

[0058] In the above configuration, when a high-frequency signal is applied between the planar electrode 66 and the planar electrode 68, a potential difference is generated between the two electrodes, causing the piezoelectric layer 67 to distort and generating bulk elastic waves in the stacking direction. By setting the thickness of the piezoelectric layer 67 to correspond to the passband of the elastic wave filter 1, an elastic wave filter 1 with desired transmission characteristics can be realized.

[0059] In addition, in the series arm resonator S1A shown in Figure 2B, instead of the air gap 150, an acoustic multilayer film having a structure in which low acoustic impedance layers 161 and high acoustic impedance layers 162 are alternately stacked may be arranged. With this arrangement, an energy confinement layer is provided between the piezoelectric layer 73 and the support substrate 71, so that the series arm resonator S1A functions as an XBAR.

[0060] [3 Structure of an elastic wave filter] Next, the structure of the elastic wave filter according to this embodiment will be described in comparison with the structure of the elastic wave filter 500 according to the comparative example.

[0061] Figure 3A is a cross-sectional view of an elastic wave filter 1 according to an embodiment. As shown in the figure, the elastic wave filter 1 comprises a mounting substrate 80, a piezoelectric substrate 70, a series arm resonator S1, a capacitor 11, a floating planar electrode 41, via conductors 91 and 92, and external connection electrodes 93 and 94.

[0062] The mounting substrate 80 is an example of a first substrate and has two main surfaces 80a (first main surface) and 80b facing away from each other. Examples of mounting substrates 80 include substrates made of low-temperature co-fired ceramics (LTCC) formed by low-temperature co-firing of a laminate of multiple dielectric layers, substrates made of high-temperature co-fired ceramics (HTCC) formed by high-temperature co-firing, component-embedded substrates, substrates having a redistribution layer (RDL), or printed circuit boards.

[0063] The piezoelectric substrate 70 is an example of a second substrate and has two main surfaces 70a and 70b (second main surface) facing away from each other. The piezoelectric substrate 70 is arranged such that the main surface 70b faces the main surface 80a of the mounting substrate 80 with an air gap in between.

[0064] The series-arm resonator S1 consists of a piezoelectric substrate 70 and an IDT electrode 31 arranged on the main surface 70b. The IDT electrode 31 is an example of a functional electrode.

[0065] Capacitor 11 is an example of a bridging capacitance element and is arranged on the main surface 70b. Capacitor 11 has a pair of comb-shaped electrodes formed on the main surface 70b so as to be interlocked with each other.

[0066] The series arm resonator S1 and the capacitor 11 are connected in parallel on the main surface 70b.

[0067] The floating planar electrode 41 is an example of a floating electrode and is positioned on the main surface 80a. The floating planar electrode 41 may also be a floating electrode having a terminal shape or a bump shape. A floating electrode is an electrode that is not set to ground potential or a fixed potential; specifically, it is an electrode that is not connected to an electrode or terminal set to ground potential or a fixed potential when a high-frequency signal passes through the elastic wave filter 1. The fixed potential includes the signal potential of the high-frequency signal transmitted through the elastic wave filter 1.

[0068] The via conductor 91 is a conductor formed between the main surface 70b and the main surface 80b, and consists of a columnar conductor positioned between the main surface 70b and the main surface 80a, and a through conductor penetrating between the main surface 80a and the main surface 80b. The via conductor 91 is an electrode set to ground potential.

[0069] The via conductor 92 is a conductor formed between the main surface 70b and the main surface 80b, and consists of a columnar conductor positioned between the main surface 70b and the main surface 80a, and a through conductor penetrating between the main surface 80a and the main surface 80b. The via conductor 92 is an electrode set to the signal potential of a high-frequency signal.

[0070] The external connection electrode 93 is positioned on the main surface 80b, connected to the via conductor 91, and also connected to the motherboard on which the elastic wave filter 1 is mounted. The external connection electrode 93 is set to ground potential.

[0071] The external connection electrode 94 is positioned on the main surface 80b, connected to the via conductor 92, and also connected to the motherboard on which the elastic wave filter 1 is mounted. The external connection electrode 94 is an electrode set to the signal potential of a high-frequency signal.

[0072] Furthermore, a frame may be positioned between the main surface 70b and the main surface 80a so as to surround the elastic wave resonator, capacitor 11, and floating planar electrode 41 when the main surfaces 70b and 80a are viewed from above. The frame separates the space in which the elastic wave resonator, capacitor 11, and floating planar electrode 41 are located from the external space. The frame may also be positioned to cover the columnar conductors that constitute the via conductors 91 and 92.

[0073] Figure 4 shows the electrode layout of the series arm resonator S1 and capacitor 11 of the elastic wave filter 1 according to the embodiment. The figure shows the electrode layout as viewed from the mounting substrate 80 side of the main surface 70b. The IDT electrode 31 and a pair of comb-tooth electrodes that constitute the capacitor 11 are arranged on the main surface 70b. One comb-tooth electrode that constitutes the IDT electrode 31 and one comb-tooth electrode that constitutes the capacitor 11 are connected by wiring W1, and the other comb-tooth electrode that constitutes the IDT electrode 31 and the other comb-tooth electrode that constitutes the capacitor 11 are connected by wiring W2.

[0074] Here, when the main surfaces 80a and 70b are viewed from above, region A is enclosed by the IDT electrode 31, the capacitor 11, and the wirings W1 and W2 connecting the IDT electrode 31 and the capacitor 11. R This overlaps with at least a portion of the floating planar electrode 41.

[0075] Furthermore, region A is enclosed by the IDT electrode 31, capacitor 11, and wirings W1 and W2. R This includes the IDT electrode 31, the capacitor 11, and the wirings W1 and W2.

[0076] Figure 3B is a cross-sectional view of the elastic wave filter 500 according to the comparative example. As shown in the figure, the elastic wave filter 500 comprises a mounting substrate 80, a piezoelectric substrate 70, a series arm resonator S1, a capacitor 11, a ground plane electrode 541, via conductors 91 and 92, and external connection electrodes 93 and 94. The elastic wave filter 500 according to the comparative example differs from the elastic wave filter 1 according to the embodiment only in that the ground plane electrode 541 is placed in place of the floating plane electrode 41. Therefore, the following description will focus on the configuration of the ground plane electrode 541 in the elastic wave filter 500 according to the comparative example.

[0077] The ground plane electrode 541 is an example of a ground electrode, and is placed on the main surface 80a and connected to the via conductor 91 which is set to ground potential. A ground electrode is an electrode set to ground potential, and specifically, it is an electrode or electrode connected to a terminal which is set to ground potential.

[0078] The IDT electrode 31 and the capacitor 11 are arranged on the main surface 70b, similar to the elastic wave filter 1 according to the embodiment. Here, when the main surface 80a and the main surface 70b are viewed from above, the region A is enclosed by the IDT electrode 31, the capacitor 11, and the wirings W1 and W2 connecting the IDT electrode 31 and the capacitor 11. R This overlaps, at least partially, with the ground plane electrode 541.

[0079] The elastic wave resonators (series arm resonators S1 and S2, parallel arm resonators P1 and P2) that constitute the elastic wave filter 1 exhibit inductive impedance in the frequency domain between the resonant frequency and the anti-resonant frequency. On the other hand, the capacitor 11 exhibits capacitive impedance. As a result, the series arm resonators S1 and capacitor 11, which are connected in parallel to each other, are in approximately opposite phase in the above frequency domain, and this phase difference causes current to flow between the series arm resonators S1 and capacitor 11. In other words, as shown in Figure 4, the series arm resonators S1, capacitor 11, and wirings W1 and W2 form a current loop. This current loop generates a magnetic field (magnetic flux) in the z-axis direction.

[0080] Here, in a plan view of the main surface 80a, region A R If a planar electrode is not positioned on the main surface 80a that overlaps with the current loop, the magnetic field (magnetic flux) generated due to the current loop will leak into the mounting substrate 80 and couple with the planar conductors and via conductors formed on the mounting substrate 80. As a result, the circuit constants of the elastic wave filter will deviate from the design values, degrading the transmission characteristics and attenuation characteristics.

[0081] Furthermore, in the comparative example elastic wave filter 500, in a plan view of the main surface 80a, in order to shield the magnetic field generated due to the current loop, region A R A ground plane electrode 541 is positioned on the main surface 80a where it overlaps with the magnetic field. However, when the magnetic field couples with the ground plane electrode 541, the impedance of the series arm resonator S1 and the capacitor 11 changes significantly. As a result, the circuit constants of the elastic wave filter 500 deviate from their design values, degrading the transmission and attenuation characteristics.

[0082] In particular, when the elastic wave filter 500 is miniaturized and made lower in height, the distance between the main surface 70b and the main surface 80a decreases, which strengthens the coupling between the magnetic field generated by the current loop and the planar conductor and via conductor formed on the mounting substrate 80, further degrading the transmission and attenuation characteristics of the elastic wave filter 500.

[0083] In contrast, in the elastic wave filter 1 according to the embodiment, region A R A floating planar electrode 41 is positioned on the main surface 80a that overlaps with the current loop. This prevents the magnetic field (magnetic flux) generated by the current loop from leaking to the mounting substrate 80. Furthermore, the floating planar electrode 41 is not set to a fixed potential, including ground potential, and no clear potential difference is generated between it and the current loop, so coupling between the magnetic field and the floating planar electrode 41 is suppressed. Therefore, the circuit constants of the elastic wave filter 1 do not deviate from the design values, and deterioration of the transmission characteristics and attenuation characteristics can be suppressed.

[0084] In addition, in the elastic wave filter 1 according to this embodiment, when the main surfaces 70b and 80a are viewed from above, it is desirable that the capacitor 11 overlaps with at least a portion of the floating planar electrode 41.

[0085] According to this, the magnetic field generated due to the current loop can be suppressed from coupling with the electrodes of the mounting substrate 80, thereby further improving the attenuation characteristics of the elastic wave filter 1.

[0086] Furthermore, in the elastic wave filter 1 according to this embodiment, in the plan view, region A R It is desirable that the floating planar electrode 41 be included.

[0087] According to this, the magnetic field generated due to the current loop can be shielded with high efficiency by the floating planar electrode 41, thereby further improving the attenuation characteristics of the elastic wave filter 1.

[0088] In this embodiment, the elastic wave filter 1 is formed by the series arm resonator S1 and the capacitor 11, and region A R The above diagram shows a configuration in which the floating planar electrode 41 and the region formed by the parallel arm resonator P1 and the capacitor 21 overlap in the above planar view. The elastic wave filter according to the present invention may have a configuration in which the region formed by the parallel arm resonator P1 and the capacitor 21 and the floating electrode overlap in the above planar view, instead of (or in addition to) the above configuration. This makes it possible to suppress deterioration of the transmission characteristics and attenuation characteristics of the elastic wave filter.

[0089] Furthermore, the present invention also includes elastic wave devices (elastic wave resonators) having either a series arm resonator S1 and a capacitor 11, or a parallel arm resonator P1 and a capacitor 21, in the elastic wave filter 1. This makes it possible to suppress the deterioration of the transmission characteristics and damping characteristics of the elastic wave resonator.

[0090] [4. Multiplexer Circuit Configuration] Next, the circuit configuration of a multiplexer 100 equipped with an elastic wave filter having the characteristics of the elastic wave filter 1 according to the embodiment will be described.

[0091] Figure 5 is a circuit diagram of a multiplexer 100 according to an embodiment. As shown in the figure, the multiplexer 100 includes a common terminal 103, an elastic wave filter 110, and filters 120, 130, and 140.

[0092] The elastic wave filter 110 comprises series arm resonators S10, S20, S30, S40, and S50, parallel arm resonators P10, P20, P30, and P40, a capacitor 13, an inductor 15, and input / output terminals 101 and 102. The elastic wave filter 110 is, for example, a bandpass filter having a passband that includes the transmission bandwidth of band A.

[0093] The input / output terminal 101 is connected to the common terminal 103.

[0094] Each of the series arm resonators S10 to S50 includes an elastic wave resonator and is arranged in series in the series arm path connecting the input / output terminal 101 (first input / output terminal) and the input / output terminal 102 (second input / output terminal). The series arm resonator S10 is composed of divided resonators S11 and S12 connected in series with each other. The series arm resonator S30 is composed of divided resonators S31 and S32 connected in series with each other. The series arm resonator S40 is composed of divided resonators S41 and S42 connected in series with each other. Each of the parallel arm resonators P10 to P40 includes an elastic wave resonator and is connected between the series arm path and ground.

[0095] Each of the series arm resonators S10 to S50 and the parallel arm resonators P10 to P40 may consist of a single elastic wave resonator, or it may consist of a split resonator.

[0096] Capacitor 13 is an example of a bridging capacitance element and is connected in parallel to the series arm resonator S30.

[0097] By connecting capacitor 13 in parallel to the series arm resonator S30, the resonant bandwidth of the series arm resonator S30 can be reduced, and the resonant Q value of the resonant circuit in which the series arm resonator S30 and capacitor 13 are connected in parallel can be increased. This makes it possible to realize an elastic wave filter 110 with improved low loss within the passband and a steeper gap between the passband and the attenuation band.

[0098] Inductor 15 is connected between the parallel arm resonators P30 and P40 and ground. By adjusting the inductance value of inductor 15, it is possible to form an attenuation pole in a predetermined frequency range or enhance the attenuation in the pass characteristics of the elastic wave filter 110.

[0099] The elastic wave filter 110 includes at least one series arm resonator and at least one parallel arm resonator, and a bridging capacitance element is connected to at least one of the series arm resonator and the parallel arm resonator.

[0100] Filter 120 is an example of a first filter, for example, a bandpass filter having a passband that includes the receiving band of band A, and is connected between the common terminal 103 and the signal output terminal 105. Filter 130 is, for example, a bandpass filter having a passband that includes the transmitting band of band B, and is connected to the common terminal 103. Filter 140 is, for example, a bandpass filter having a passband that includes the receiving band of band B, and is connected to the common terminal 103.

[0101] Band A is, for example, Band B3 for 4G-LTE or Band n3 for 5G-NR. Band B is, for example, Band B1 for 4G-LTE or Band n1 for 5G-NR. A multiplexer 100 to which the above band combinations are applied constitutes a quadplexer.

[0102] Each elastic wave resonator (series arm resonators S10 to S50 and parallel arm resonators P10 to P40) constituting the elastic wave filter 110 may have any of the following structures: the SAW resonator shown in Figure 2A, the XBAR shown in Figure 2B, the BAW resonator shown in Figure 2C, or the SMR-type BAW resonator shown in Figure 2D.

[0103] [5 Structure of a Multiplexer] Next, the structure of the multiplexer 100 according to this embodiment will be described.

[0104] Figure 6 is a cross-sectional view of the multiplexer 100 according to the embodiment. Figure 7A is a first plan view showing the electrode layout of the multiplexer 100 according to the embodiment. Figure 7B is a second plan view showing the electrode layout of the multiplexer 100 according to the embodiment. Figure 7C is a third plan view showing the electrode layout of the multiplexer 100 according to the embodiment. Figure 7A shows the electrode layout on the main surface 70b of the piezoelectric substrate 70 (first plan view), Figure 7B shows the electrode layout on the L1 layer (main surface 80a) of the mounting substrate 80 (second plan view), and Figure 7C shows the electrode layout on the L3 layer of the mounting substrate 80 (third plan view). Figure 6 is also a view of the cross-sectional view along the line VI-VI in Figures 7A, 7B, and 7C, seen from the positive y-axis side. Note that the electrode layouts on the L2 and L4 layers of the mounting substrate 80 are not shown.

[0105] As shown in Figures 6 to 7C, the multiplexer 100 comprises a mounting substrate 80, a piezoelectric substrate 70, an elastic wave filter 110, filters 120 to 140, a floating planar electrode 41, via conductors 91 and 92, and external connection electrodes 93 and 94.

[0106] The mounting substrate 80 is an example of a first substrate and, as shown in Figure 6, has two main surfaces 80a (first main surface) and 80b facing away from each other. On the mounting substrate 80, L1, L2, L3, and L4 layers, on which planar conductors are formed, are arranged from the main surface 80a toward the main surface 80b. The L1 layer includes the main surface 80a, and the L4 layer includes the main surface 80b. Examples of mounting substrates 80 include LTCC substrates, HTCC substrates, component-embedded substrates, substrates with RDLs, or printed circuit boards.

[0107] The piezoelectric substrate 70 is an example of a second substrate and, as shown in Figure 6, has two main surfaces 70a and 70b (second main surface) facing away from each other. The piezoelectric substrate 70 is positioned such that the main surface 70b faces the main surface 80a of the mounting substrate 80 with an air gap in between.

[0108] The elastic wave filter 110 comprises series arm resonators S10 to S50, parallel arm resonators P10 to P40, a capacitor 13, an inductor 15, and input / output terminals 101 and 102.

[0109] As shown in Figure 7A, the series arm resonators S10 to S50 and the parallel arm resonators P10 to P40 (and their IDT electrodes) are formed on the main surface 70b. The electrodes of the filters 120 to 140 are also formed on the main surface 70b. In addition, bump electrodes for joining the piezoelectric substrate 70 and the mounting substrate 80 are arranged on the main surface 70b.

[0110] The series-arm resonator S30 is composed of a piezoelectric substrate 70 and an IDT electrode 32 arranged on the main surface 70b. The IDT electrode 32 is an example of a functional electrode.

[0111] Capacitor 13 is an example of a bridging capacitance element and is arranged on the main surface 70b. Capacitor 13 has a pair of comb-shaped electrodes formed on the main surface 70b so as to be interlocked with each other.

[0112] The series arm resonator S30 and the capacitor 13 are connected in parallel on the main surface 70b.

[0113] The floating planar electrode 41 is an example of a floating electrode and is disposed on the main surface 80a as shown in FIG. 7B. Note that the floating planar electrode 41 may be a floating electrode having a terminal shape or a bump shape.

[0114] As shown in FIG. 7C, the inductor 15 is composed of a coil conductor formed in the L3 layer of the mounting substrate 80.

[0115] The via conductor 91 is a conductor formed between the main surface 80a and the main surface 80b and is an electrode set to a ground potential. The via conductor 92 is a conductor formed between the main surface 80a and the main surface 80b and is an electrode set to a signal potential of a high-frequency signal.

[0116] The external connection electrode 93 is disposed on the main surface 80b, connected to the via conductor 91, and also connected to a mother board on which the multiplexer 100 is mounted. The external connection electrode 93 is an electrode set to a ground potential. The external connection electrode 94 is disposed on the main surface 80b, connected to the via conductor 92, and also connected to a mother board on which the multiplexer 100 is mounted. The external connection electrode 94 is an electrode set to a signal potential of a high-frequency signal.

[0117] The mounting substrate 80 and the piezoelectric substrate 70 are joined via a plurality of bump electrodes including bump electrodes 151, 152, and 153, and a gap is secured between the main surface 80a and the main surface 70b.

[0118] Note that a frame body may be disposed between the main surface 70b and the main surface 80a so as to surround the surface acoustic wave resonator, the capacitor 13, and the floating planar electrode 41. The frame body separates the space in which the surface acoustic wave resonator, the capacitor 13, and the floating planar electrode 41 are disposed from the external space.

[0119] Here, when the main surface 80a and the main surface 70b are viewed in plan view, a region A R is overlapped with at least a part of the floating planar electrode 41.

[0120] Furthermore, region A is enclosed by the IDT electrode 32, the capacitor 13, and the wiring connecting the IDT electrode 32 and the capacitor 13. R This includes the IDT electrode 32, the capacitor 13, and the above-mentioned wiring.

[0121] [6. High-Frequency Transmission Characteristics of Multiplexers] Figure 8A is a graph showing the transmission characteristics of the elastic wave filter 110 provided in the multiplexer according to the embodiment, comparative example 1, and comparative example 2. Figure 8B is a graph showing the voltage standing wave ratio of the elastic wave filter 110 provided in the multiplexer according to the embodiment, comparative example 1, and comparative example 2. Figure 8C is a graph showing the isolation characteristics of the multiplexer according to the embodiment, comparative example 1, and comparative example 2.

[0122] The multiplexer according to Comparative Example 1 differs from the multiplexer 100 according to the embodiment only in that a floating planar electrode 41 is not arranged on the main surface 80a. The multiplexer according to Comparative Example 2 differs from the multiplexer 100 according to the embodiment only in that a ground planar electrode is arranged on the main surface 80a instead of the floating planar electrode 41.

[0123] The elastic wave resonators (series arm resonators S10-S50, parallel arm resonators P10-P40) constituting the elastic wave filter 110 exhibit inductive impedance in the frequency domain between the resonant frequency and the anti-resonant frequency. On the other hand, the capacitor 13 exhibits capacitive impedance. As a result, the series arm resonator S30 and the capacitor 13, which are connected in parallel to each other, are in approximately opposite phase in the above frequency domain, and this phase difference causes current to flow between the series arm resonator S30 and the capacitor 13. A current loop is formed between the series arm resonator S30, the capacitor 13, and the wiring connecting the series arm resonator S30 and the capacitor 13. This current loop generates a magnetic field (magnetic flux) in the z-axis direction.

[0124] In the multiplexer according to Comparative Example 1, in a plan view of the main surface 80a, region A R Since no planar electrodes are positioned on the main surface 80a that overlaps with the main surface 80a, the magnetic field (magnetic flux) generated by the current loop formed by the IDT electrode 32, capacitor 13, and the above wiring leaks into the mounting substrate 80, and for example, this magnetic field couples with the magnetic field of the inductor 15 formed in the L3 layer. As a result, the attenuation near the high frequency of the passband is reduced, as shown in Figure 8A (within the black dashed circle in Figure 8A). Furthermore, due to the reduction in the attenuation of the elastic wave filter 110, the isolation between the elastic wave filter 110 and the filter 120 deteriorates, as shown in Figure 8C (within the black dashed circle in Figure 8C).

[0125] Furthermore, in the multiplexer according to Comparative Example 2, in a plan view of the main surface 80a, in order to shield the magnetic field (magnetic flux) generated due to the current loop, region A R A ground plane electrode is positioned on the main surface 80a, which overlaps with the magnetic field. As a result, the magnetic field couples with the ground plane electrode, causing a significant change in the impedance of the series arm resonator S30 and the capacitor 13. This worsens the voltage standing wave ratio within the passband of the elastic wave filter 110 at the signal input terminal 104, as shown in Figure 8B. Furthermore, due to the change in impedance, the attenuation near high frequencies in the passband is reduced, as shown in Figure 8A. Additionally, due to the reduction in the attenuation of the elastic wave filter 110, the isolation between the elastic wave filter 110 and the filter 120 deteriorates, as shown in Figure 8C.

[0126] In contrast, in the multiplexer 100 according to the embodiment, region A RA floating planar electrode 41 is positioned on the main surface 80a that overlaps with the current loop. This suppresses leakage of the magnetic field (magnetic flux) generated by the current loop to the mounting substrate 80. Furthermore, since the floating planar electrode 41 is not set to a fixed potential, including ground potential, and no clear potential difference is generated between it and the current loop, coupling between the magnetic field and the floating planar electrode 41 is suppressed. Therefore, the circuit constants of the elastic wave filter 110 and the multiplexer 100 do not deviate from the design values. As a result, as shown in Figure 8A, a large amount of attenuation near the high frequency of the passband of the elastic wave filter 110 can be secured (within the black dashed circle in Figure 8A). Also, as shown in Figure 8B, the voltage standing wave ratio within the passband of the elastic wave filter 110 is not worsened. In addition, as shown in Figure 8C, the isolation between the elastic wave filter 110 and the filter 120 can be improved (within the black dashed circle in Figure 8C).

[0127] In addition, in the multiplexer 100 according to this embodiment, when the main surfaces 70b and 80a are viewed from above, it is desirable that the capacitor 13 overlaps with at least a portion of the floating planar electrode 41.

[0128] According to this, the magnetic field generated due to the current loop and the electric field generated due to the capacitor 13 can be prevented from coupling with the electrodes of the mounting substrate 80, thereby further improving the attenuation characteristics of the elastic wave filter 1 and the isolation characteristics of the multiplexer 100.

[0129] Furthermore, in the multiplexer 100 according to this embodiment, in the above plan view, region A R It is desirable that the floating planar electrode 41 be included.

[0130] According to this, the magnetic field generated due to the current loop can be shielded with high efficiency by the floating planar electrode 41, thereby further improving the attenuation characteristics of the elastic wave filter 1 and the isolation characteristics of the multiplexer 100.

[0131] [7 Effects, etc.] As described above, the elastic wave apparatus according to the embodiment comprises a first substrate having a first main surface, a second substrate having a second main surface facing the first main surface across an air gap, an elastic wave resonator including a functional electrode and disposed on the second substrate, a bridging capacitance element disposed on the second main surface and connected in parallel to the elastic wave resonator, and a floating electrode disposed on the first main surface. When the first and second main surfaces are viewed from above, the region enclosed by the functional electrode, the bridging capacitance element, and the wiring connecting the functional electrode and the bridging capacitance element overlaps with at least a part of the floating electrode.

[0132] According to this, leakage of the magnetic field generated by the current loop formed by the functional electrode and bridging capacitance element to the first substrate can be suppressed. Furthermore, since the floating electrode is not set to a fixed potential such as ground potential, and no clear potential difference is generated between it and the current loop, coupling between the magnetic field and the floating electrode is suppressed. Therefore, the circuit constants of the elastic wave device do not deviate from the design values, and deterioration of the attenuation characteristics can be suppressed.

[0133] Furthermore, for example, in the elastic wave apparatus according to the embodiment, in the plan view described above, the bridging capacitance element overlaps with at least a portion of the floating electrode.

[0134] According to this, the coupling between the magnetic field generated by the current loop and the electric field generated by the bridging capacitance element with the electrodes of the first substrate can be suppressed, thereby further improving the attenuation characteristics of the elastic wave apparatus.

[0135] Furthermore, for example, in the elastic wave apparatus according to the embodiment, the region in the plan view includes the floating electrode.

[0136] According to this, the magnetic field generated due to the current loop can be shielded with high efficiency by the floating electrode, thereby further improving the attenuation characteristics of the elastic wave device.

[0137] Furthermore, for example, in the elastic wave apparatus according to the embodiment, the bridging capacitance element includes a pair of comb-tooth electrodes.

[0138] According to this, the bridging capacitance element can be miniaturized, thus reducing the area of ​​the second main surface.

[0139] Furthermore, for example, the elastic wave filter 1 according to the embodiment comprises a mounting substrate 80 having a main surface 80a, a piezoelectric substrate 70 having a main surface 70b facing the main surface 80a across an air gap, a series arm resonator S1 including a functional electrode and disposed on the piezoelectric substrate 70, a capacitor 11 disposed on the main surface 70b and connected in parallel to the series arm resonator S1, and a floating planar electrode 41 disposed on the main surface 80a, wherein the piezoelectric substrate 70 includes a piezoelectric layer 73 disposed on the main surface 70b side, the functional electrode includes an IDT electrode 31 disposed on the piezoelectric layer 73, and when the main surface 80a and the main surface 70b are viewed in plan view, a region A is enclosed by the IDT electrode 31, the capacitor 11, and the wirings W1 and W2. R It overlaps with the floating planar electrode 41, at least in part.

[0140] According to this, leakage of the magnetic field generated by the current loop formed by the IDT electrode 31 and the capacitor 11 to the mounting substrate 80 can be suppressed. Furthermore, since the floating planar electrode 41 is not set to a fixed potential such as ground potential, and no clear potential difference is generated between it and the current loop, coupling between the magnetic field and the floating planar electrode 41 is suppressed. Therefore, the circuit constants of the elastic wave filter 1 do not deviate from the design values, and deterioration of the attenuation characteristics can be suppressed.

[0141] For example, in the elastic wave apparatus according to the embodiment, the functional electrodes include planar electrodes 66 and 68 arranged so as to sandwich the piezoelectric layer 67, and the planar electrode 66, piezoelectric layer 67, and planar electrode 68 are arranged on the second main surface in this order from the second main surface toward the first main surface.

[0142] According to this, when the elastic wave resonator is a BAW resonator, leakage of the magnetic field generated by the current loop formed by the functional electrode and bridging capacitance element to the first substrate can be suppressed. Furthermore, since the floating electrode is not set to a fixed potential such as ground potential, and no clear potential difference is generated between it and the current loop, coupling between the magnetic field and the floating electrode is suppressed. Therefore, the circuit constants of the elastic wave device do not deviate from the design values, and deterioration of the damping characteristics can be suppressed.

[0143] Furthermore, the elastic wave filter 110 according to the embodiment comprises a mounting substrate 80 having a main surface 80a, a piezoelectric substrate 70 having a main surface 70b facing the main surface 80a across an air gap, series arm resonators S10 to S50 arranged in a series arm path connecting input / output terminals 101 and 102, parallel arm resonators P10 to P40 connected between the series arm path and ground, a capacitor 13 arranged on the main surface 70b and connected in parallel to the series arm resonator S30, and a floating planar electrode 41 arranged on the main surface 80a, wherein the series arm resonator S30 is an elastic wave resonator including an IDT electrode 32, and when the main surface 80a and the main surface 70b are viewed in plan view, region A is enclosed by the IDT electrode 32, the capacitor 13, and the wiring connecting the IDT electrode 32 and the capacitor 13. R This overlaps with at least a portion of the floating planar electrode 41.

[0144] According to this, leakage of the magnetic field generated by the current loop formed by the IDT electrode 32 and the capacitor 13 to the mounting substrate 80 can be suppressed. Furthermore, since the floating planar electrode 41 is not set to a fixed potential such as ground potential, and no clear potential difference is generated between it and the current loop, coupling between the magnetic field and the floating planar electrode 41 is suppressed. Therefore, the circuit constants of the elastic wave filter 110 do not deviate from the design values, and deterioration of the attenuation characteristics can be suppressed.

[0145] For example, the elastic wave filter 110 further includes an inductor 15 connected between the parallel arm resonator P30 and ground, the mounting substrate 80 is made of an insulating material, and the inductor 15 is composed of a coil conductor formed on the above material.

[0146] According to this, the arrangement of the floating planar electrode 41 can suppress the coupling of the magnetic field generated due to the current loop with the inductor 15 formed on the mounting substrate 80. Therefore, the deterioration of the attenuation characteristics of the elastic wave filter 110 can be suppressed.

[0147] Furthermore, the multiplexer 100 according to this embodiment includes a common terminal 103, an elastic wave filter 110 connected to the common terminal 103, and a filter 120 connected to the common terminal 103.

[0148] According to this, leakage of the magnetic field generated due to the current loop to the mounting substrate 80 can be suppressed. Also, since no clear potential difference is generated between the floating planar electrode 41 and the current loop, coupling between the magnetic field and the floating planar electrode 41 is suppressed. Therefore, the circuit constants of the elastic wave filter 110 and the multiplexer 100 do not deviate from the design values. Thus, the attenuation characteristics of the elastic wave filter 110 and the isolation characteristics of the multiplexer 100 can be improved. (Other variations, etc.) Although embodiments of the elastic wave apparatus, elastic wave filter, and multiplexer have been described above, the elastic wave apparatus, elastic wave filter, and multiplexer of the present invention are not limited to the above embodiments. Other embodiments realized by combining any of the components in the above embodiments, modified versions obtained by applying various modifications to the above embodiments that a person skilled in the art can conceive of without departing from the spirit of the present invention, and various devices incorporating the elastic wave apparatus, elastic wave filter, and multiplexer according to the above embodiments are also included in the present invention. [Industrial applicability]

[0149] The present invention can be widely used in communication devices such as mobile phones as a low-loss and high-attenuation elastic wave filter and multiplexer applicable to multiband frequency standards. [Explanation of symbols]

[0150] 1,110,500 Elastic wave filter 11, 13, 21 Capacitors 15 Inductors 31, 32 IDT electrode 41 Floating Planar Electrode 55 Protective layer 60a, 60b comb electrode 61a, 61b electrode fingers 62a, 62b busbar electrodes 65, 71 Support substrate 66, 68 Planar electrode 67, 73 Piezoelectric layer 70, 70A Piezoelectric Substrate 70a, 70b, 80a, 80b main surface 72 Low sound speed layer 80 Mounted circuit boards 91, 92 via conductors 93, 94 External connection electrodes 100 Multiplexer 101, 102 input / output terminals 103 Common terminal 104 Signal Input Terminals 105 Signal output terminal 120, 130, 140 filters 150 void 151, 152, 153 Bump electrodes 161 Low acoustic impedance layer 162 High Acoustic Impedance Layer 540 Close contact layer 541 Ground Planar Electrode 542 Main electrode layer A R region P1, P2, P10, P20, P30, P40 parallel arm resonators S1, S1A, S1B, S1C, S2, S10, S20, S30, S40, S50 series arm resonators S11, S12, S31, S32, S41, S42 split resonator W1, W2 wiring

Claims

1. A first substrate having a first main surface, A second substrate having a second main surface that faces the first main surface across a gap, A resonator comprising a functional electrode and disposed on the second substrate, A bridging capacitance element is arranged on the second main surface and connected in parallel to the elastic wave resonator, The device comprises a floating electrode disposed on the first main surface, When the first main surface and the second main surface are viewed from above, the region enclosed by the functional electrode, the bridging capacitance element, and the wiring connecting the functional electrode and the bridging capacitance element overlaps with at least a portion of the floating electrode. Elastic wave device.

2. In the aforementioned plan view, the bridging capacitance element overlaps with at least a portion of the floating electrode. The elastic wave apparatus according to claim 1.

3. In the aforementioned plan view, the region includes the floating electrode. The elastic wave apparatus according to claim 1.

4. The bridging capacitance element includes a pair of comb-tooth electrodes, The elastic wave apparatus according to any one of claims 1 to 3.

5. The second substrate includes a piezoelectric layer disposed on the second main surface side, The functional electrode includes an IDT (InterDigital Transducer) electrode disposed in the piezoelectric layer. The elastic wave apparatus according to any one of claims 1 to 4.

6. The functional electrode includes a first planar electrode and a second planar electrode arranged so as to sandwich a piezoelectric layer. The first planar electrode, the piezoelectric layer, and the second planar electrode are arranged on the second main surface in this order, oriented from the second main surface towards the first main surface. The elastic wave apparatus according to any one of claims 1 to 4.

7. A first substrate having a first main surface, A second substrate having a second main surface that faces the first main surface across a gap, A series arm resonator is arranged in a series arm path connecting the first input / output terminal and the second input / output terminal, A parallel arm resonator connected between the series arm path and ground, A bridging capacitance element is arranged on the second main surface and connected in parallel to one of the series arm resonators and the parallel arm resonators, The device comprises a floating electrode disposed on the first main surface, One of the series-arm resonator and the parallel-arm resonator is an elastic wave resonator including a functional electrode. When the first main surface and the second main surface are viewed from above, the region enclosed by the functional electrode, the bridging capacitance element, and the wiring connecting the functional electrode and the bridging capacitance element overlaps with at least a portion of the floating electrode. Elastic wave filter.

8. Furthermore, it includes an inductor connected between the parallel arm resonator and ground, The first substrate is made of an insulating material, The inductor is composed of a coil conductor formed in the base body. The elastic wave filter according to claim 7.

9. Common terminal and A seismic wave filter according to claim 7 or 8 connected to the common terminal, The system comprises a first filter connected to the common terminal, Multiplexer.

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