Acoustic wave device and multiplexer

Abstract

To provide an acoustic wave device suppressed in deterioration of pass characteristics.SOLUTION: A filter 20 includes a series arm resonator s21, parallel arm resonators p21-p24, a laminated substrate 40 having main surfaces 40a and 40b, a piezoelectric substrate 50, and a bump electrode 70 (121) disposed on a main surface 50a. The parallel arm resonator p21 includes an IDT electrode disposed on the main surface 50a. The bump electrode 70 (121) is connected to the IDT electrode. The laminated substrate 40 includes a flat electrode 410 disposed on the main surface 40a and joined to the bump electrode 70 (121), a flat electrode 440 disposed on the main surface 40b and connected to the ground, and a plurality of via conductors 81 connecting the flat electrode 410 and the flat electrode 440. In a plan view of the main surface 40a, the bump electrode 70 (121) is located between a via conductor 81a and a via conductor 81b connected to the flat electrode 410. In the parallel arm resonators p21-p24, the parallel arm resonator p21 has the highest resonance frequency.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Patent Document 1 discloses a branching device (elastic wave device) including multiple surface acoustic wave filters formed on a piezoelectric substrate and a mounting substrate having multiple dielectric layers. A small-sized acoustic wave device can be realized by face-down bonding of bump electrodes arranged on the piezoelectric substrate to land electrodes arranged on the mounting substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2015 / 016203 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the acoustic wave device described in Patent Document 1 has a problem in that the transmission characteristics of the acoustic wave device are degraded due to misalignment between the bump electrodes and the land electrodes during face-down bonding.

[0005] Therefore, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an acoustic wave device and a multiplexer in which degradation of the pass characteristics is suppressed. [Means for solving the problem]

[0006] In order to achieve the above object, an elastic wave device according to one aspect of the present invention includes a first series arm resonator arranged in a series arm path connecting a first input / output terminal and a second input / output terminal, a plurality of parallel arm resonators connected between the series arm path and a ground, a first substrate having first and second main surfaces opposing each other and including a plurality of dielectric layers, a second substrate having a third main surface arranged opposite to the first main surface, and a first bump electrode arranged on the third main surface, wherein the first series arm resonator includes a first functional electrode arranged on the third main surface, and a first parallel arm resonator of the plurality of parallel arm resonators includes a second functional electrode arranged on the third main surface. the first substrate includes a first planar electrode, the first bump electrode being connected to the second functional electrode, the first substrate has a first planar electrode arranged on a first dielectric layer of the plurality of dielectric layers and joined to the first bump electrode, a second planar electrode arranged on a second dielectric layer of the plurality of dielectric layers closer to the second principal surface than the first dielectric layer and connected to ground, and a plurality of via conductors connecting the first planar electrode and the second planar electrode, wherein when the first principal surface is viewed in a plane, the first bump electrode is located between two of the plurality of via conductors connected to the first planar electrode, and the first parallel arm resonator has the highest resonant frequency among the plurality of parallel arm resonators.

[0007] An elastic wave device according to one aspect of the present invention includes a first series arm resonator arranged in a series arm path connecting a first input / output terminal and a second input / output terminal, a plurality of parallel arm resonators connected between the series arm path and a ground, a first substrate having first and second main surfaces opposing each other and having a plurality of dielectric layers, a second substrate having a third main surface arranged opposite to the first main surface, and a first bump electrode arranged on the third main surface, wherein the first series arm resonator includes a first functional electrode arranged on the third main surface, and a first parallel arm resonator of the plurality of parallel arm resonators includes a second functional electrode arranged on the third main surface, and the first bump electrode is connected to the second functional electrode. the first substrate has a first planar electrode arranged on a first dielectric layer of the plurality of dielectric layers and joined to a first bump electrode, a second planar electrode arranged on a second dielectric layer of the plurality of dielectric layers closer to the second principal surface than the first dielectric layer and connected to ground, and a plurality of via conductors connecting the first planar electrode and the second planar electrode, wherein when the first principal surface is viewed in a plan view, the first bump electrode is located between two of the plurality of via conductors connected to the first planar electrode, each of the first functional electrode and the second functional electrode is an IDT electrode, and the first parallel arm resonator has the smallest electrode finger pitch of the IDT electrodes among the plurality of parallel arm resonators. Effect of the Invention

[0008] According to the present invention, it is possible to provide an acoustic wave device and a multiplexer in which degradation of the transmission characteristics is suppressed. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a circuit configuration diagram of a multiplexer according to an embodiment. [Diagram 2] 1 is a cross-sectional view of a multiplexer according to an embodiment. [Diagram 3] FIG. 2 is a plan view of a filter chip according to an embodiment. [Figure 4A] 1A and 1B are a plan view and a cross-sectional view illustrating a first example of an acoustic wave resonator that constitutes a multiplexer according to an embodiment of the present invention. [Figure 4B]10 is a cross-sectional view illustrating a schematic diagram of a second example of an acoustic wave resonator that constitutes a multiplexer according to an embodiment. FIG. [Figure 4C] FIG. 11 is a cross-sectional view illustrating a schematic diagram of a third example of an acoustic wave resonator that constitutes a multiplexer according to an embodiment. [Diagram 5] 2A to 2C are plan views of layers of a laminated substrate constituting a multiplexer according to an embodiment of the present invention. [Figure 6] 5A to 5C are plan views of layers of a laminated substrate constituting a multiplexer according to a comparative example. [Figure 7A] 2 is an enlarged plan view of a first layer of the multilayer substrate in the embodiment. FIG. [Figure 7B] FIG. 4 is an enlarged plan view of a first layer of a multilayer substrate according to a comparative example. [Figure 8A] 4 is a graph showing isolation characteristics of a multiplexer according to an embodiment. [Figure 8B] 11 is a graph showing isolation characteristics of a multiplexer according to a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, arrangements and connection forms of the components shown in the following embodiments are merely examples and are not intended to limit the present invention.

[0011] In addition, each figure is a schematic diagram in which emphasis, omission, or adjustment of the ratio is appropriately performed in order to illustrate the present invention, and is not necessarily a strict illustration, and may differ from the actual shape, positional relationship, and ratio. In each figure, the same reference numerals are given to substantially the same configurations, and duplicated explanations may be omitted or simplified.

[0012] In the circuit configuration of the present disclosure, “connected between A and B” and “connected between A and B” mean connected to both A and B between A and B.

[0013] In addition, in the component arrangement of the present disclosure, “component A is arranged in series on path B” means that both the signal input terminal and the signal output terminal of component A are connected to the wiring, electrode, or terminal that constitutes path B.

[0014] In addition, terms indicating the relationship between elements, such as "parallel" and "perpendicular," terms indicating the shape of an element, such as "rectangle," and numerical ranges do not only indicate the strict meaning, but also include a substantially equivalent range, for example, an error of about a few percent.

[0015] In the component layout of this disclosure, "planar view of the principal surface" means that an object is viewed by orthogonal projection onto the principal surface from the z-axis side. "A is located between B and C" means that at least one of multiple line segments connecting an arbitrary point in B and an arbitrary point in C passes through A.

[0016] In the following embodiments, the passband of an acoustic wave device or filter is defined as a frequency band between two frequencies that are 3 dB higher than the minimum value of insertion loss in the passband.

[0017] In addition, in the present disclosure, band A refers to a frequency band defined in advance by a standardization organization (e.g., 3GPP (registered trademark), IEEE (Institute of Electrical and Electronics Engineers), etc.) for a communication system built using a radio access technology (RAT). In this embodiment, the communication system may be, for example, a Long Term Evolution (LTE) system, a 5th Generation (5G)-New Radio (NR) system, and a Wireless Local Area Network (WLAN) system, but is not limited thereto.

[0018] Additionally, the uplink operating band of Band A refers to the frequency range of Band A designated for uplink use, and the downlink operating band of Band A refers to the frequency range of Band A designated for downlink use.

[0019] (Embodiment) [1. Circuit configuration of multiplexer] 1 is a circuit diagram of a multiplexer 1 according to an embodiment of the present invention. The multiplexer 1 includes filters 10 and 20 and a common terminal 100.

[0020] Filter 10 is connected to common terminal 100 and has a passband that includes an uplink operating band, e.g., band A. Filter 20 is an example of an acoustic wave device, and is connected to common terminal 100 and has a passband that includes a downlink operating band, e.g., band A. In this embodiment, the passband of filter 10 is located at a lower frequency than the passband of filter 20.

[0021] Note that band A is, for example, band B3 for LTE or band n3 for 5G-NR. The passband of filter 10 includes the uplink operating band (1710-1785 MHz) of band B3 or band n3, and the passband of filter 20 includes the downlink operating band (1805-1880 MHz) of band B3 or band n3.

[0022] As shown in FIG. 1, the filter 10 includes series arm resonators s11, s12, s13, and s14, parallel arm resonators p11, p12, p13, and p14, and inductors 31 and 32.

[0023] Each of the series arm resonators s11 to s14 is an elastic wave resonator and is disposed in a series arm path connecting the input terminal 110 and the output terminal 101. The parallel arm resonator p11 is an elastic wave resonator and is connected between the connection point of the series arm resonators s11 and s12 and the terminal 111. The parallel arm resonator p12 is an elastic wave resonator and is connected between the connection point of the series arm resonators s12 and s13 and the terminal 112. The parallel arm resonator p13 is an elastic wave resonator and is connected between the connection point of the series arm resonators s13 and s14 and the terminal 112. The parallel arm resonator p14 is an elastic wave resonator and is connected between the connection point of the series arm resonator s14 and the input terminal 110 and the terminal 113. The terminal 111 is connected to the ground without an inductor. The terminal 112 is connected to the ground via the inductor 31. The terminal 113 is connected to the ground via the inductor 32.

[0024] With the above configuration, filter 10 constitutes a ladder-type bandpass filter.

[0025] Each of the series arm resonators s13 and s14 is composed of three split resonators connected in series, but may be composed of a single resonator. Each of the series arm resonators s11, s12 and the parallel arm resonators p11 to p14 is composed of two split resonators connected in series, but may be composed of a single resonator.

[0026] The filter 20 is an example of an acoustic wave device, and includes series arm resonators s21, s22, s23, and s24, parallel arm resonators p21, p22, p23, and p24, and an inductor 33.

[0027] Each of the series arm resonators s21 to s24 is a surface acoustic wave resonator or a bulk acoustic wave resonator, and is arranged in a series arm path connecting the input terminal 102 (first input / output terminal) and the output terminal 120 (second input / output terminal). The series arm resonators s21 and s22 are each an example of a first series arm resonator.

[0028] The parallel arm resonator p21 is an example of a first parallel arm resonator and is connected between the connection point of the series arm resonators s21 and s22 and the terminal 121. The parallel arm resonator p22 is an example of a second parallel arm resonator and is connected between the connection point of the series arm resonators s22 and s23 and the terminal 121. The parallel arm resonator p23 is an example of a third parallel arm resonator and is connected between the connection point of the series arm resonators s23 and s24 and the terminal 122. The parallel arm resonator p24 is an example of a third parallel arm resonator and is connected between the connection point of the series arm resonator s24 and the output terminal 120 and the terminal 122. Each of the parallel arm resonators p21 to p24 is a surface acoustic wave resonator or a bulk acoustic wave resonator. The terminal 121 is connected to the ground without an inductor. The terminal 122 is connected to the ground via an inductor 33.

[0029] With the above configuration, the filter 20 constitutes a ladder-type bandpass filter.

[0030] Although the series arm resonator s21 is composed of three split resonators connected in series, it may be composed of one resonator. Furthermore, each of the series arm resonators s22 to s24 and the parallel arm resonators p21 to p24 is composed of one resonator, but may be composed of two or more split resonators.

[0031] Table 1 shows the resonant frequency, anti-resonant frequency, and capacitance of filter 20.

[0032] [Table 1]

[0033] [2. Basic structure of a multiplexer] Fig. 2 is a cross-sectional view of the multiplexer 1 according to the embodiment, and Fig. 3 is a plan view of the filter chip 2 according to the embodiment, and Fig. 2 is a cross-sectional view of the multiplexer 1 taken along line II-II in Fig. 3.

[0034] As shown in Fig. 2, the multiplexer 1 includes a filter chip 2 and a laminated substrate 40. As shown in Fig. 3, the filter chip 2 includes a piezoelectric substrate 50, IDT (Inter Digital Transducer) electrodes 54 (shown in Fig. 3 as s11 to s14, p11 to p14, s21 to s24, and p21 to p24), a common terminal 100, an input terminal 110, an output terminal 120, terminals 111, 112, 113, 121, and 122, and a bump electrode 70. Each of the common terminal 100, the input terminal 110, the output terminal 120, and the terminals 111, 112, 113, 121, and 122 is a planar electrode formed on a main surface 50a (third main surface) of the piezoelectric substrate 50.

[0035] Although not shown in FIG. 3, common terminal 100, input terminal 110, output terminal 120, terminals 111, 112, 113, 121 and 122 are disposed on the positive z-axis side of bump electrode 70.

[0036] In addition, in Figures 3, 5, 6, 7A and 7B, the bump electrode 70 joined to the common terminal 100 is referred to as bump electrode 70(100), the bump electrode 70 joined to the input terminal 110 is referred to as bump electrode 70(110), the bump electrode 70 joined to the output terminal 120 is referred to as bump electrode 70(120), and the bump electrodes 70 joined to the terminals 111, 112, 113, 121 and 122, respectively, are referred to as bump electrodes 70(111), 70(112), 70(113), 70(121) and 70(122).

[0037] In Figure 3, the IDT electrodes and planar electrodes that constitute filter 10 are arranged above filter chip 2 (on the positive y-axis side), and the IDT electrodes and planar electrodes that constitute filter 20 are arranged below filter chip 2 (on the negative y-axis side).

[0038] 2 and 3 show an example in which each series arm resonator and each parallel arm resonator is a surface acoustic wave resonator, but each series arm resonator and each parallel arm resonator may be a bulk acoustic wave resonator. Detailed structures of the surface acoustic wave resonator and the bulk acoustic wave resonator will be described with reference to FIGS. 4A to 4C.

[0039] The piezoelectric substrate 50 is an example of a second substrate, and has principal surfaces 50a (third principal surface) and 50b facing each other, and has piezoelectric properties. An example of the structure of the piezoelectric substrate 50 will be described with reference to FIGS. 4A to 4C.

[0040] The laminated substrate 40 is an example of a first substrate, and has opposing main surfaces 40a and 40b, and a plurality of dielectric layers L1, L2, and L3, as shown in Fig. 2. The laminated substrate 40 is disposed so that the main surface 40a faces the main surface 50a. As the laminated substrate 40, for example, a low temperature co-fired ceramics (LTCC) substrate having a laminated structure of a plurality of dielectric layers L1 to L3, a high temperature co-fired ceramics (HTCC) substrate, a component-embedded substrate, a substrate having a redistribution layer (RDL), a printed circuit board, or the like is used.

[0041] The laminated substrate 40 has, from the main surface 40a to the main surface 40b, an electrode layer L41 which is the surface of the dielectric layer L1 facing in the positive direction of the z axis, an electrode layer L42 which is the surface of the dielectric layer L2 facing in the positive direction of the z axis, an electrode layer L43 which is the surface of the dielectric layer L3 facing in the positive direction of the z axis, and an electrode layer L44 which is the surface of the dielectric layer L3 facing in the negative direction of the z axis, and a conductor pattern consisting of a planar electrode is formed on each electrode layer.

[0042] [3. Basic structures of series arm resonators and parallel arm resonators] Next, a basic structure of each series arm resonator and each parallel arm resonator constituting the multiplexer 1 will be described. Fig. 4A is a plan view and a cross-sectional view that typically show a first example of an elastic wave resonator constituting the multiplexer 1 according to an embodiment. This figure illustrates the basic structure of an elastic wave resonator constituting the multiplexer 1. Note that an elastic wave resonator 60 shown in Fig. 4A is intended to illustrate a typical structure of an elastic wave resonator constituting the multiplexer 1, and the number and length of electrode fingers constituting the electrodes are not limited thereto.

[0043] The acoustic wave resonator 60 is composed of a piezoelectric substrate 50 and comb electrodes 60a and 60b. As shown in FIG. 4A(a), a pair of comb electrodes 60a and 60b facing each other is formed on the piezoelectric substrate 50. The comb electrode 60a is composed of a plurality of electrode fingers 61a parallel to each other and a bus bar electrode 62a connecting one ends of the plurality of electrode fingers 61a. The comb electrode 60b is composed of a plurality of electrode fingers 61b parallel to each other and a bus bar electrode 62b connecting one ends of the plurality of electrode fingers 61b. The plurality of electrode fingers 61a and 61b are formed along a direction perpendicular to the acoustic wave propagation direction (X-axis direction). The bus bar electrode 62a and the bus bar electrode 62b are arranged facing each other with the electrode fingers 61a and 61b interposed therebetween. The comb electrodes 60a and 60b form an IDT electrode 54.

[0044] When filter 20 according to the present embodiment performs electromechanical conversion using surface acoustic waves, IDT electrode 54 is a functional electrode. Acoustic wave resonator 60 may have reflectors on both ends of IDT electrode 54 in the acoustic wave propagation direction (X-axis direction).

[0045] As shown in FIG. 4B, the IDT electrode 54 has a laminated structure of an adhesive layer 540 and a main electrode layer 542, for example.

[0046] The adhesion layer 540 is a layer for improving adhesion between the piezoelectric substrate 50 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. The protective layer 55 is formed so as to cover the comb-shaped electrodes 60a and 60b. 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 increase moisture resistance, and is, for example, a dielectric film whose main component is silicon dioxide.

[0047] The materials constituting the adhesion layer 540, the main electrode layer 542, and the protective layer 55 are not limited to the above-mentioned materials. Furthermore, the IDT electrode 54 does not have to have the above-mentioned laminated structure. The IDT electrode 54 may be made of a metal or alloy such as Ti, Al, Cu, Pt, Au, Ag, or Pd, or may be made of a laminate of multiple layers made of the above-mentioned metals or alloys. Furthermore, the protective layer 55 does not have to be formed.

[0048] Next, the layered structure of the piezoelectric substrate 50 will be described.

[0049] As shown in (c) of Figure 4A, the piezoelectric substrate 50 includes a high acoustic speed support substrate 51, a low acoustic speed film 52, and a piezoelectric film 53, and has a structure in which the high acoustic speed support substrate 51, the low acoustic speed film 52, and the piezoelectric film 53 are laminated in this order.

[0050] The piezoelectric film 53 is made of, for example, θ°Y-cut X-propagation LiTaO3 piezoelectric single crystal or piezoelectric ceramics (lithium tantalate single crystal or ceramics cut on a plane whose normal is an axis rotated θ° from the Y axis around the X axis, and whose surface acoustic wave propagates in the X axis direction). Note that the material and cut angle θ of the piezoelectric single crystal used as the piezoelectric film 53 are appropriately selected depending on the required specifications of each filter.

[0051] The high acoustic velocity support substrate 51 is a substrate that supports the low acoustic velocity film 52, the piezoelectric film 53, and the IDT electrode 54. The high acoustic velocity support substrate 51 is a substrate in which the acoustic velocity of the bulk waves in the high acoustic velocity support substrate 51 is faster than that of the surface waves and boundary waves propagating through the piezoelectric film 53, and functions to confine the surface acoustic waves to the portion where the piezoelectric film 53 and the low acoustic velocity film 52 are laminated, and to prevent the surface acoustic waves from leaking below the high acoustic velocity support substrate 51. Examples of materials that can be used for the high acoustic velocity support substrate 51 include piezoelectric materials such as aluminum nitride, lithium tantalate, lithium niobate, and quartz, ceramics such as alumina, sapphire, magnesia, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, forsterite, spinel, and sialon, dielectric materials such as aluminum oxide, silicon oxynitride, DLC (diamond-like carbon), and diamond, semiconductors such as silicon, and materials mainly composed of the above materials. The spinel includes an aluminum compound containing oxygen and one or more elements selected from Mg, Fe, Zn, Mn, etc. Examples of the spinel include MgAl2O4, FeAl2O4, ZnAl2O4, and MnAl2O4.

[0052] The low acoustic velocity film 52 is a film in which the acoustic velocity of the bulk waves in the low acoustic velocity film 52 is slower than that of the bulk waves propagating through the piezoelectric film 53, and is disposed between the piezoelectric film 53 and the high acoustic velocity support substrate 51. This structure and the property of the acoustic wave concentrating energy in a medium with an essentially low acoustic velocity suppress leakage of surface acoustic wave energy to the outside of the IDT electrode 54. The low acoustic velocity film 52 can be made of a dielectric material such as glass, silicon oxide, silicon oxynitride, lithium oxide, tantalum oxide, or a compound in which fluorine, carbon, or boron is added to silicon oxide, or a material containing the above-mentioned material as a main component.

[0053] The laminated structure of piezoelectric substrate 50 makes it possible to significantly increase the Q value at the resonant frequency and the anti-resonant frequency, compared to a conventional structure using a single-layer piezoelectric substrate. In other words, an elastic wave resonator with a high Q value can be configured, and therefore a filter with low insertion loss can be configured using the elastic wave resonator.

[0054] The high acoustic velocity support substrate 51 may have a structure in which a support substrate and a high acoustic velocity film in which the acoustic velocity of the propagating bulk wave is faster than that of the elastic wave such as the surface wave and boundary wave propagating through the piezoelectric film 53 are laminated. In this case, the material of the high acoustic velocity film can be the same as the material of the high acoustic velocity support substrate 51. The material of the support substrate can be, for example, a piezoelectric material such as aluminum nitride, lithium tantalate, lithium niobate, or quartz; a ceramic material such as alumina, sapphire, magnesia, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, or forsterite; a dielectric material such as diamond or glass; a semiconductor material such as silicon or gallium nitride; or a resin; or a material mainly composed of the above-mentioned material.

[0055] In this specification, the term "major component of a material" refers to a component that accounts for more than 50% by weight of the material. The major component may be in any of the following states: single crystal, polycrystalline, or amorphous, or a mixture of these.

[0056] Fig. 4B is a cross-sectional view that illustrates a second example of an acoustic wave resonator that constitutes the multiplexer 1 according to the embodiment. In the acoustic wave resonator 60 illustrated in Fig. 4A, the IDT electrode 54 is formed on the piezoelectric substrate 50 having the piezoelectric film 53. However, the substrate on which the IDT electrode 54 is formed may be a piezoelectric single crystal substrate 57 that is made of a single layer of a piezoelectric material, as illustrated in Fig. 4B.

[0057] The piezoelectric single crystal substrate 57 is made of, for example, a piezoelectric single crystal of LiNbO3. The elastic wave resonator according to this example is made of the piezoelectric single crystal substrate 57 made of LiNbO3, an IDT electrode 54, and a protective layer 58 formed on the piezoelectric single crystal substrate 57 and the IDT electrode 54.

[0058] The laminated structure, material, cut angle, and thickness of the piezoelectric film 53 and the piezoelectric single crystal substrate 57 may be changed as appropriate depending on the required pass characteristics of the multiplexer 1. Even an elastic wave resonator using a LiTaO3 piezoelectric substrate having a cut angle other than the above-mentioned cut angle can achieve the same effect as the elastic wave resonator 60 using the piezoelectric film 53.

[0059] The piezoelectric substrate on which the IDT electrode 54 is formed may have a structure in which a support substrate, an energy trapping layer, and a piezoelectric film are laminated in this order. The IDT electrode 54 is formed on the piezoelectric film. For example, a LiTaO3 piezoelectric single crystal or a piezoelectric ceramic is used for the piezoelectric film. The support substrate is a substrate that supports the piezoelectric film, the energy trapping layer, and the IDT electrode 54.

[0060] The energy trapping layer is composed of one or more layers, and the speed of the bulk acoustic wave propagating through at least one of the layers is greater than the speed of the acoustic wave propagating near the piezoelectric film. For example, the energy trapping layer may have a laminated structure of a low acoustic velocity layer and a high acoustic velocity layer. The low acoustic velocity layer is a film in which the acoustic velocity of the bulk wave in the low acoustic velocity layer is slower than the acoustic velocity of the acoustic wave propagating through the piezoelectric film. The high acoustic velocity layer is a film in which the acoustic velocity of the bulk wave in the high acoustic velocity layer is faster than the acoustic velocity of the acoustic wave propagating through the piezoelectric film. The support substrate may be the high acoustic velocity layer.

[0061] The energy trapping layer may be an acoustic impedance layer having a configuration in which low acoustic impedance layers having a relatively low acoustic impedance and high acoustic impedance layers having a relatively high acoustic impedance are alternately laminated.

[0062] Here, electrode parameters of the IDT electrodes constituting the acoustic wave resonator 60 will be described.

[0063] The wavelength of the acoustic wave resonator is defined as wavelength λ, which is the repetition period of multiple electrode fingers 61a or 61b constituting IDT electrode 54 shown in Fig. 4A(b). The electrode finger pitch is 1 / 2 of wavelength λ, and is defined as (W+S), where W is the line width of electrode fingers 61a and 61b constituting comb-shaped electrodes 60a and 60b, respectively, and S is the space width between adjacent electrode fingers 61a and 61b.

[0064] In the case where the interval between adjacent electrode fingers in IDT electrode 54 is not constant, the electrode finger pitch of IDT electrode 54 is defined as the average electrode finger pitch of IDT electrode 54. The average electrode finger pitch of IDT electrode 54 is defined as Di / (Ni-1), where the total number of electrode fingers 61a, 61b included in IDT electrode 54 is Ni, and the center-to-center distance between the electrode finger located at one end and the electrode finger located at the other end of IDT electrode 54 in the acoustic wave propagation direction is Di.

[0065] 4C is a cross-sectional view that typically illustrates a third example of an acoustic wave resonator that constitutes the multiplexer 1 according to the embodiment. In FIG. 4C, a bulk acoustic wave resonator is illustrated as the acoustic wave resonator of the multiplexer 1. As illustrated in the figure, the bulk acoustic wave resonator includes, for example, a support substrate 65, a lower electrode 66, a piezoelectric layer 67, and an upper electrode 68, and is configured such that the support substrate 65, the lower electrode 66, the piezoelectric layer 67, and the upper electrode 68 are laminated in this order.

[0066] The support substrate 65 is a substrate for supporting the lower electrode 66, the piezoelectric layer 67, and the upper electrode 68, and is, for example, a silicon substrate. The support substrate 65 has a cavity in an area in contact with the lower electrode 66. This allows the piezoelectric layer 67 to vibrate freely.

[0067] The lower electrode 66 is an example of a third planar electrode, and is formed on one surface of the support substrate 65. The upper electrode 68 is an example of a fourth planar electrode, and is formed on one surface of the support substrate 65. The lower electrode 66 and the upper electrode 68 are made of a material, for example, Al containing 1% Cu.

[0068] The piezoelectric layer 67 is an example of a piezoelectric thin film, and is formed between the lower electrode 66 and the upper electrode 68. The piezoelectric layer 67 is mainly composed of at least one of ZnO (zinc oxide), AlN (aluminum nitride), PZT (lead zirconate titanate), KN (potassium niobate), LN (lithium niobate), LT (lithium tantalate), quartz crystal, and LiBO (lithium borate).

[0069] A bulk acoustic wave resonator having the above-described laminated structure generates resonance by inducing bulk acoustic waves in the piezoelectric layer 67 by applying electrical energy between the lower electrode 66 and the upper electrode 68. The bulk acoustic waves generated by this bulk acoustic wave resonator propagate between the lower electrode 66 and the upper electrode 68 in a direction perpendicular to the film surface of the piezoelectric layer 67. In other words, the bulk acoustic wave resonator is a resonator that utilizes bulk acoustic waves.

[0070] Here, when the filter 20 according to the present embodiment performs electromechanical transduction using bulk acoustic waves, the lower electrode 66, the piezoelectric layer 67, and the upper electrode 68 are functional electrodes. Also, the support substrate 65 may be a first substrate instead of the piezoelectric substrate 50.

[0071] [4. Bonding structure between filter chip and laminated substrate] Next, the joining structure between the filter chip 2 and the laminated substrate 40 will be described with reference to FIG. 3 and FIGS. 5 to 7B.

[0072] 3, in the filter chip 2, the parallel arm resonator p21 (first parallel arm resonator) has a part of the piezoelectric substrate 50 and an IDT electrode 54p. The IDT electrode 54p is an example of a second functional electrode and is one of the IDT electrodes 54. Moreover, the series arm resonator s21 (first series arm resonator) has another part of the piezoelectric substrate 50 and an IDT electrode 54s. The IDT electrode 54s is an example of a first functional electrode and is one of the IDT electrodes 54.

[0073] 1 are planar electrodes on the main surface 50a, the same as the common terminal 100. A bump electrode 70 is bonded to each of the common terminal 100, the input terminal 110, the output terminal 120, and the terminals 111, 112, 113, 121, and 122. As shown in FIG. 3, the bump electrode 70 (121) is an example of a first bump electrode, and is connected to the IDT electrode 54p.

[0074] Fig. 5 is a plan view of each layer of the laminated substrate 40 constituting the multiplexer 1 according to the embodiment. As shown in Fig. 5, the laminated substrate 40 has planar electrodes 410, 420, 430, 440, 441, 442, 443, and 444, and a plurality of via conductors 81. The circles (○) shown in (a) to (c) of Fig. 5 represent the via conductors 81 that penetrate from the surface on the principal surface 40a side to the surface on the principal surface 40b side of any of the dielectric layers L1 to L3.

[0075] 5(a) shows an electrode layout of the electrode layer L41 formed on the surface of the dielectric layer L1 on the principal surface 40a side. A bump electrode 70 provided on the filter chip 2 is joined to a planar electrode of the electrode layer L41. A planar electrode 410 formed on the electrode layer L41 is an example of a first planar electrode, and is joined to the bump electrodes 70(121) and 70(111). The planar electrode 410 to which the bump 70(121) is connected is connected to a planar electrode 420 of the electrode layer L42 below the electrode layer L41 by a plurality of via conductors 81.

[0076] 5(b) shows an electrode layout of the electrode layer L42 formed on the principal surface 40a side of the dielectric layer L2. The planar electrode 420 is connected by a plurality of via conductors 81 to a planar electrode 430 of the electrode layer L43 below the electrode layer L42.

[0077] 5(c) shows an electrode layout of the electrode layer L43 formed on the principal surface 40a side of the dielectric layer L3. The planar electrode 430 is connected by a plurality of via conductors 81 to a planar electrode 440 of the electrode layer L44 below the electrode layer L43.

[0078] FIG. 5(d) shows the electrode layout of the electrode layer L44 formed on the surface of the dielectric layer L3 on the principal surface 40b side. The planar electrode 440 formed on the electrode layer L44 is an example of a second planar electrode, and is connected to the planar electrode 430 formed on the electrode layer L43 through a plurality of via conductors 81, and is connected to the ground. The planar electrode 441 formed on the electrode layer L44 is connected to the bump electrode 70 (100) of the electrode layer L41 through the electrode layers L42 and L43. The planar electrode 442 formed on the electrode layer L44 is connected to the bump electrode 70 (110) of the electrode layer L41 through the electrode layers L42 and L43. The planar electrode 443 formed on the electrode layer L44 is connected to the bump electrode 70 (120) of the electrode layer L41 through the electrode layers L42 and L43. Furthermore, the planar electrode 444 formed on the electrode layer L44 is connected to the bump electrode 70 (122) of the electrode layer L41 via the electrode layers L42 and L43. The planar electrodes 440, 441, 442, 443 and 444 formed on the electrode layer L44 are external connection terminals for connecting the multiplexer 1 to an external substrate disposed opposite the main surface 40b.

[0079] The number of via conductors 81 connecting the planar electrode 410 and the planar electrode 420 is the largest among the number of via conductors 81 connecting one planar electrode of the electrode layer L41 and one planar electrode of the electrode layer L42. This makes it possible to reduce the inductor component between the planar electrode 410 and the planar electrode 420.

[0080] In addition, the number of via conductors 81 connecting the planar electrode 420 and the planar electrode 430 is the largest among the number of via conductors 81 connecting one planar electrode of the electrode layer L42 and one planar electrode of the electrode layer L43. This makes it possible to reduce the inductor component between the planar electrode 420 and the planar electrode 430.

[0081] In addition, the number of via conductors 81 connecting the planar electrode 430 and the planar electrode 440 is the largest among the number of via conductors 81 connecting one planar electrode of the electrode layer L43 and one planar electrode of the electrode layer L44. This makes it possible to reduce the inductor component between the planar electrode 430 and the planar electrode 440.

[0082] These make it possible to reduce the inductor component from the planar electrode 440, which is the external connection terminal, to the bump 70 (121), and as a result, the steepness of the filter characteristics can be improved.

[0083] In addition, the planar electrode 410 joined to the bump electrode 70 (121) does not have to be arranged on the electrode layer L41, which is the outermost layer of the laminated substrate 40, but may be arranged on a first dielectric layer among the multiple dielectric layers L1-L3 on which the planar electrode is formed, and the planar electrode 440 does not have to be arranged on the electrode layer L44, which is the outermost layer of the laminated substrate 40, but may be arranged on a second dielectric layer closer to the main surface 40b than the first dielectric layer among the multiple dielectric layers L1-L3 on which the planar electrode is formed.

[0084] 6 is a plan view of each layer of the laminated substrate 40 constituting the multiplexer according to the comparative example. The multiplexer according to the comparative example differs from the multiplexer 1 according to the embodiment only in that the planar electrode 410 of the electrode layer L41 is replaced with a planar electrode 510.

[0085] 6(a) shows the electrode layout of the electrode layer L41. The bump electrodes 70 provided on the filter chip 2 are joined to the planar electrodes of the electrode layer L41. The planar electrodes 510 formed on the electrode layer L41 are joined to the bump electrodes 70 (121) and 70 (111). The electrode layouts in FIGS. 6(b) to 6(d) are the same as the electrode layouts in FIGS. 5(b) to 5(d), respectively.

[0086] Fig. 7A is an enlarged plan view of an electrode layer L41 of a laminated substrate 40 according to an embodiment. Fig. 7B is an enlarged plan view of an electrode layer L41 of a laminated substrate according to a comparative example. Fig. 7A is an enlarged plan view of an area VIIA in Fig. 5(a), and Fig. 7B is an enlarged plan view of an area VIIB in Fig. 6(a).

[0087] Here, as shown in FIG. 7A, in the filter 20 according to the present embodiment, when the main surface 40a is viewed in plan, the bump electrode 70 (121) is located between two via conductors 81a and 81b among the multiple via conductors 81 connected to the planar electrode 410. The bump electrode 70 (121) is connected between the parallel arm resonator p21 of the filter 20 and the ground. As shown in Table 1, the parallel arm resonator p21 has the highest resonance frequency among the multiple parallel arm resonators constituting the filter 20. The multiple parallel arm resonators constituting the filter 20 are parallel arm resonators that contribute to forming the pass band of the filter 20, and are specifically defined as parallel arm resonators whose anti-resonance frequencies are located within the pass band of the filter 20.

[0088] Furthermore, the parallel arm resonator p21 has the highest resonant frequency among the multiple parallel arm resonators that constitute the filter 20; in other words, the parallel arm resonator p21 has the smallest electrode finger pitch of the IDT electrodes among the multiple parallel arm resonators that constitute the filter 20.

[0089] In a ladder-type elastic wave filter, when a parasitic inductance occurs in a path connecting a parallel arm resonator and a ground, the resonant frequency of the parallel arm resonator fluctuates. If the capacitance of the parallel arm resonator is Cp and the parasitic inductance is Lp, the resonant frequency of the parallel arm resonator (=1 / 2π√(LpCp)) fluctuates toward the lower frequency side as the parasitic inductance Lp increases, and the interval between the resonant frequency and the antiresonant frequency increases. This makes the attenuation slope on the lower frequency side of the pass band gentler, and the attenuation in the vicinity of the lower frequency side of the pass band deteriorates. In particular, the parallel arm resonator having the highest resonant frequency among the multiple parallel arm resonators constituting the elastic wave filter determines the attenuation and steepness in the vicinity of the lower frequency side of the pass band. Therefore, when the resonant frequency of the parallel arm resonator having the highest resonant frequency fluctuates toward the lower frequency side, the attenuation characteristics in the vicinity of the lower frequency side of the pass band of the elastic wave filter deteriorate significantly. In the multiplexer 1 and the filter 20 according to the present embodiment, no intentional inductor is connected between the parallel arm resonator p21, which has the highest resonant frequency among the multiple parallel arm resonators, and ground. The intentional inductor includes a chip-shaped inductor and an inductor made of a conductor coil formed on an electrode layer constituting a laminated substrate.

[0090] 7B, in the multiplexer according to the comparative example, when the main surface 40a is viewed in plan, the bump electrode 70 (121) is not located between two of the via conductors 81 among the multiple via conductors 81 connected to the planar electrode 510. Therefore, when the joining position of the bump electrode 70 (121) is shifted, the distance between the bump electrode 70 (121) and the via conductor 81 closest to it varies, and therefore the parasitic inductance generated between the bump electrode 70 (121) and the ground-connected planar electrode 440 of the electrode layer L44 varies significantly.

[0091] In contrast, in the case of the multiplexer 1 according to the embodiment, as shown in Fig. 7A, the bump electrode 70 (121) is located between two of the via conductors 81, 81a and 81b. Therefore, even if the joining position of the bump electrode 70 (121) fluctuates, if the distance between the bump electrode 70 (121) and the via conductor 81a increases, the distance between the bump electrode 70 (121) and the via conductor 81b decreases. This suppresses the fluctuation of the parasitic inductance defined by the parallel connection of the parasitic inductance occurring in the path connecting the bump electrode 70 (121) and the via conductor 81a and the parasitic inductance occurring in the path connecting the bump electrode 70 (121) and the via conductor 81b.

[0092] Fig. 8A is a graph showing the isolation characteristics of the multiplexer 1 according to the embodiment. Fig. 8B is a graph showing the isolation characteristics of a multiplexer according to a comparative example. The multiplexer according to the comparative example differs from the multiplexer 1 according to the embodiment only in that the planar electrode 410 of the filter 20 is replaced with a planar electrode 510.

[0093] Two types of waveform data (solid line and dashed line) are shown in each of Figures 8A and 8B. In both Figures 8A and 8B, the solid line waveform data is data obtained when the position of the bump electrode 70 (121) is shifted by +30 μm in the positive direction of the y axis with respect to the dashed line waveform data.

[0094] In multiplexer 1 according to this embodiment, the isolation of the passband of filter 10 is 58.5 dB when there is no misalignment (dashed line data in FIG. 8A) and 58.0 dB when there is a misalignment (solid line data in FIG. 8A), a degradation of 0.5 dB.

[0095] On the other hand, in the multiplexer according to the comparative example, the isolation of the passband of the filter 10 is 58.4 dB when there is no misalignment (dashed line data in FIG. 8B) and is 54.1 dB when there is a misalignment (solid line data in FIG. 8B), a degradation of 4.3 dB.

[0096] As described above, the multiplexer 1 according to the embodiment can improve isolation on the high frequency side of the passband of the filter 10, because even if there is a misalignment of the bump electrodes for connecting the parallel arm resonator having the highest resonant frequency to ground when the filter chip 2 is face-down bonded to the laminated substrate 40, the variation in parasitic inductance between the parallel arm resonator and ground is suppressed. In other words, the filter 20 according to the embodiment can improve the attenuation characteristics near the low frequency side of the passband of the filter 20, compared to the filter according to the comparative example. Therefore, it is possible to provide the filter 20 and the multiplexer 1 in which deterioration of the passband characteristics is suppressed.

[0097] 1, in the filter 20 according to this embodiment, the parallel arm resonator p21 is connected to a path connecting the input terminal 102 and the series arm resonator s22 and to a terminal 121, and the parallel arm resonator p22 is connected to a path connecting the output terminal 120 and the series arm resonator s22 and to a terminal 121. In other words, the parallel arm resonators p21 and p22 are connected to ground via a common bump electrode 70 (121) as shown in FIG.

[0098] The larger the capacitance Cp is, the more likely the resonant frequency (=1 / 2π√(LpCp)) of the parallel arm resonator is to fluctuate even with a slight variation in the parasitic inductance Lp. For this reason, reducing the capacitance Cp is effective for suppressing the variation in the resonant frequency. However, in order to achieve a reduction in the size of the filter chip, it is necessary to reduce the number of bump electrodes 70 connected to the ground, and it becomes necessary to connect multiple parallel arm resonators to a common bump electrode 70. As a result, in the multiplexer according to the conventional (comparative) example, the combined capacitance Cp of the parallel arm resonators p21 and p22 connected to one bump electrode 70 becomes large, and even a slight variation in the parasitic inductance Lp causes a large variation in the resonant frequency, which causes a problem that it is not possible to simultaneously reduce the size of the filter chip and suppress the characteristic variation.

[0099] In contrast, according to the multiplexer 1 and filter 20 of the present embodiment, even if the combined capacitance Cp of the parallel arm resonators p21 and p22 connected to one bump electrode 70 (121) becomes large, the variation in the parasitic inductance Lp due to the misalignment of the bump electrode 70 (121) can be suppressed, and therefore the variation in the attenuation characteristics on the lower frequency side than the pass band of the filter 20 defined by the parallel arm resonator p21 having the highest resonant frequency among the multiple parallel arm resonators can be suppressed. Therefore, it is possible to provide a compact filter 20 and multiplexer 1 in which degradation of the pass characteristics is suppressed.

[0100] Furthermore, in the multiplexer 1 according to the present embodiment, as shown in FIG. 7A, when the main surface 40a is viewed in a plane, the bump electrode 70 (121) is located between two via conductors 81a and 81b out of the multiple via conductors 81 connected to the planar electrode 410, and is also located between two via conductors 81c and 81d that are located on a virtual straight line that intersects with the virtual line segment connecting the two via conductors 81a and 81b.

[0101] This makes it possible to suppress fluctuations in parasitic inductance not only when the joining position of the bump electrode 70 (121) is shifted in a direction along the imaginary line connecting the via conductors 81a and 81b in a planar view of the main surface 40a, but also when it is shifted in a direction along the imaginary line connecting the via conductors 81c and 81d.

[0102] As shown in FIG. 3, eight bump electrodes 70 are arranged on the main surface 50a in the multiplexer 1 according to the present embodiment. Of the eight bump electrodes 70, the bump electrode 70 (113) (second bump electrode) and the bump electrode 70 (120) (third bump electrode) are arranged at both ends of the outer edge of the piezoelectric substrate 50 in a plan view of the main surface 50a. In contrast, the bump electrode 70 (121) is located between the bump electrode 70 (113) and the bump electrode 70 (120) in a plan view of the main surface 50a. In other words, the bump electrode 70 (121) is arranged in an area excluding the corners of the piezoelectric substrate 50. The bump electrodes arranged at the corners of the piezoelectric substrate 50 are far from the center of the piezoelectric substrate 50, so that the positional fluctuation distance of the bump electrodes increases with respect to the positional fluctuation in the rotational direction of the piezoelectric substrate 50, and the fluctuation of the parasitic inductance increases. Therefore, by arranging the bump electrode 70 (121) connected to the parallel arm resonator p21 having the highest resonant frequency among the multiple parallel arm resonators in a region excluding the corner portions of the piezoelectric substrate 50, i.e., in a region close to the center of the piezoelectric substrate 50, it is possible to effectively suppress characteristic variations due to misalignment in not only the x-axis and y-axis directions but also the rotational direction.

[0103] Furthermore, in the filter 20 according to this preferred embodiment, as shown in Table 1, the parallel arm resonator p21 has the smallest capacitance among the multiple parallel arm resonators.

[0104] Among the multiple parallel arm resonators, the parallel arm resonator p21, which has the highest resonant frequency, has the highest impedance on the low frequency side of the passband. Since the higher the impedance of a parallel arm resonator, the more the insertion loss in the passband can be reduced, by minimizing the capacitance of the parallel arm resonator p21, the impedance can be increased and the insertion loss in the passband can be improved.

[0105] The capacitance of a surface acoustic wave resonator is proportional to (number of pairs × cross width) of the IDT electrodes. Therefore, a method for identifying a parallel arm resonator with the smallest capacitance among multiple parallel arm resonators may be to compare the size of (number of pairs × cross width) of the IDT electrodes.

[0106] In the filter 20 according to this embodiment, the parallel arm resonator p23 includes a piezoelectric substrate 50, an IDT electrode (third functional electrode: illustrated as p23 in FIG. 3) disposed on the principal surface 50a, and a bump electrode 70 (122) (fourth bump electrode) connected to the IDT electrode. As shown in FIG. 5, the laminated substrate 40 includes a planar electrode 411 (fifth planar electrode) disposed on the electrode layer L41 and joined to the bump electrode 70 (122), a planar electrode 444 (sixth planar electrode) disposed on the electrode layer L44 and connected to ground, and an inductor 33 (disposed on the electrode layer L42) connected between the planar electrode 411 and the planar electrode 444.

[0107] The parallel arm resonator p23 is separated from the parallel arm resonator p21 having the highest resonant frequency by a ground in the multiplexer 1, and is connected to the ground via a bump electrode 70 (122) different from the bump electrode 70 (121) and an inductor 33. By connecting the inductor 33 to the parallel arm resonator p23, the interval between the resonant frequency and anti-resonant frequency of the parallel arm resonator p23 is widened, and the attenuation pole due to the resonant frequency of the parallel arm resonator p23 can be positioned on the low-frequency side within the pass band of the filter 10. Therefore, it is possible to provide a filter 20 having improved attenuation characteristics over a wide band on the low-frequency side of the pass band of the filter 20.

[0108] Furthermore, since the parallel arm resonator p24 is connected to the bump electrode 70 (122) together with the parallel arm resonator p23, the combined capacitance of the parallel arm resonators p23 and p24 increases, and the inductance value required to obtain a predetermined resonance frequency can be reduced. This allows the line width of the inductor 33 formed in the laminated substrate 40 to be increased, thereby suppressing variations in the inductance value of the inductor 33. As a result, it is possible to provide a compact filter 20 with improved attenuation characteristics and a compact multiplexer 1 with improved isolation characteristics.

[0109] [5. Effects, etc.] As described above, the filter 20 according to the present embodiment includes the series arm resonator s21 arranged in the series arm path connecting the input terminal 102 and the output terminal 120, the plurality of parallel arm resonators p21 to p24 connected between the series arm path and ground, the laminated substrate 40 having mutually opposing principal surfaces 40a and 40b and having a plurality of dielectric layers, the piezoelectric substrate 50 having the principal surface 50a arranged opposite to the principal surface 40a, and the bump electrode 70 (121) arranged on the principal surface 50a, in which the series arm resonator s21 includes a first functional electrode arranged on the principal surface 50a, and the parallel arm resonator p21 of the plurality of parallel arm resonators p21 to p24 includes a second functional electrode arranged on the principal surface 50a. The electrode 70 (121) is connected to the second functional electrode, and the laminated substrate 40 has a planar electrode 410 arranged on a first dielectric layer of the multiple dielectric layers and joined to the bump electrode 70 (121), a planar electrode 440 arranged on a second dielectric layer of the multiple dielectric layers closer to the main surface 40b than the first dielectric layer and connected to ground, and a plurality of via conductors 81 connecting the planar electrode 410 and the planar electrode 440, where, when the main surface 40a is viewed in plan, the bump electrode 70 (121) is located between two via conductors 81a and 81b of the multiple via conductors 81 connected to the planar electrode 410, and the parallel arm resonator p21 has the highest resonance frequency among the multiple parallel arm resonators p21 to p24.

[0110] According to this, even if there is a displacement in the bonding position of the bump electrode 70 (121) for connecting the parallel arm resonator p21 having the highest resonant frequency to ground when the filter chip 2 is bonded face-down to the laminated substrate 40, the variation in parasitic inductance occurring between the parallel arm resonator p21 and ground is suppressed. This improves the attenuation characteristics on the lower frequency side of the pass band of the filter 20, and improves the isolation characteristics on the higher frequency side of the pass band of the filter 10 in the multiplexer 1. It is therefore possible to provide a filter 20 and a multiplexer 1 in which deterioration of the pass characteristics is suppressed.

[0111] Also, for example, in the filter 20, the second substrate is the piezoelectric substrate 50, and each of the first functional electrode and the second functional electrode is an IDT electrode.

[0112] This makes it possible to suppress deterioration of the pass characteristic of the filter 20 that performs electromechanical conversion using surface acoustic waves.

[0113] For example, in the filter 20, each of the first functional electrode and the second functional electrode includes a lower electrode 66, a piezoelectric layer 67, and an upper electrode 68 in this order from the principal surface 40a.

[0114] This makes it possible to suppress deterioration of the pass characteristic of the filter 20 that performs electromechanical conversion using bulk acoustic waves.

[0115] The filter 20 according to the present embodiment includes a series arm resonator s21 arranged in a series arm path connecting the input terminal 102 and the output terminal 120, a plurality of parallel arm resonators p21 to p24 connected between the series arm path and ground, a laminated substrate 40 having mutually opposing principal surfaces 40a and 40b and having a plurality of dielectric layers, a piezoelectric substrate 50 having a principal surface 50a arranged opposite to the principal surface 40a, and a bump electrode 70 (121) arranged on the principal surface 50a, in which the series arm resonator s21 includes a first functional electrode arranged on the principal surface 50a, and the parallel arm resonator p21 of the plurality of parallel arm resonators p21 to p24 includes a second functional electrode arranged on the principal surface 50a, and the bump electrode 70 (121) is connected to the second functional electrode. The laminated substrate 40 has a planar electrode 410 arranged on a first dielectric layer of the plurality of dielectric layers and joined to a bump electrode 70 (121), a planar electrode 440 arranged on a second dielectric layer of the plurality of dielectric layers closer to the main surface 40b than the first dielectric layer and connected to ground, and a plurality of via conductors 81 connecting the planar electrode 410 and the planar electrode 440, where when the main surface 40a is viewed in plan, the bump electrode 70 (121) is located between two via conductors 81a and 81b of the plurality of via conductors 81 connected to the planar electrode 410, each of the first functional electrode and the second functional electrode is an IDT electrode, and the parallel arm resonator p21 has the smallest electrode finger pitch of the IDT electrodes among the plurality of parallel arm resonators p21 to p24.

[0116] According to this, even if there is a displacement in the bonding position of the bump electrode 70 (121) for connecting the parallel arm resonator p21 having the highest resonant frequency to ground when the filter chip 2 is bonded face-down to the laminated substrate 40, the variation in parasitic inductance occurring between the parallel arm resonator p21 and ground is suppressed. This improves the attenuation characteristics on the lower frequency side of the pass band of the filter 20, and improves the isolation characteristics on the higher frequency side of the pass band of the filter 10 in the multiplexer 1. It is therefore possible to provide a filter 20 and a multiplexer 1 in which deterioration of the pass characteristics is suppressed.

[0117] For example, the filter 20 includes parallel arm resonators p21 and p22, the parallel arm resonator p21 is connected to a path connecting the input terminal 102 and the series arm resonator s22 and to the bump electrode 70 (121), and the parallel arm resonator p22 is connected to a path connecting the output terminal 120 and the series arm resonator s22 and to the bump electrode 70 (121).

[0118] This makes it possible to suppress fluctuations in the parasitic inductance Lp due to misalignment of the bump electrode 70 (121) even if the combined capacitance Cp of the parallel arm resonators p21 and p22 connected to one bump electrode 70 (121) increases. This makes it possible to suppress fluctuations in the attenuation characteristics on the lower frequency side than the passband of the filter 20 defined by the parallel arm resonator p21, which has the highest resonant frequency among the multiple parallel arm resonators. This makes it possible to provide a compact filter 20 in which degradation of the passband characteristics is suppressed.

[0119] Also, for example, in the filter 20, the planar electrode 410 is disposed on the main surface 40a.

[0120] Also, for example, in the filter 20, the planar electrode 440 is disposed on the main surface 40b.

[0121] Also, for example, in the filter 20, the planar electrode 440 is an external connection terminal.

[0122] Also, for example, in the filter 20, when the main surface 40a is viewed in a plane, the bump electrode 70 (121) is located between two via conductors 81a and 81b of the multiple via conductors 81 connected to the planar electrode 410, and is also located between two via conductors 81c and 81d that are located on a virtual straight line that intersects with the virtual line segment connecting the two via conductors 81a and 81b.

[0123] This makes it possible to suppress fluctuations in parasitic inductance not only when the joining position of the bump electrode 70 (121) is shifted in a direction along the imaginary line connecting the via conductors 81a and 81b in a planar view of the main surface 40a, but also when it is shifted in a direction along the imaginary line connecting the via conductors 81c and 81d.

[0124] Also, for example, in the filter 20, a plurality of bump electrodes 70 including a bump electrode 70 (121) are arranged on the main surface 40a, and among the plurality of bump electrodes 70, the bump electrodes 70 (113) and 70 (120) are arranged at both ends of the outer edge of the piezoelectric substrate 50 when viewed in a plan view of the main surface 40a, and the bump electrode 70 (121) is located between the bump electrodes 70 (113) and 70 (120) when viewed in a plan view of the main surface 40a.

[0125] According to this, the bump electrode 70 (121) connected to the parallel arm resonator p21 having the highest resonant frequency among the multiple parallel arm resonators p21 to p24 is disposed in an area excluding the corner portions of the piezoelectric substrate 50, i.e., in an area close to the center of the piezoelectric substrate 50. This makes it possible to effectively suppress characteristic variations due to misalignment of the bump electrode 70 (121) in the x-axis and y-axis directions as well as misalignment of the bump electrode 70 (121) in the rotational direction.

[0126] Also, for example, in the filter 20, the parallel arm resonator p21 has the smallest capacitance among the multiple parallel arm resonators p21 to p24.

[0127] Among the multiple parallel arm resonators p21 to p24, the parallel arm resonator p21, which has the highest resonant frequency, has the lowest impedance on the low frequency side of the passband. In a parallel arm resonator, the higher the impedance, the more the insertion loss in the passband can be reduced. Accordingly, by making the capacitance of the parallel arm resonator p21 the smallest, the impedance can be increased, and the insertion loss in the passband of the filter 20 can be improved.

[0128] In addition, for example, in the filter 20, the parallel arm resonator p23 has a piezoelectric substrate 50, an IDT electrode arranged on the principal surface 50a, and a bump electrode 70 (122) arranged on the principal surface 50a and connected to the IDT electrode, and the laminated substrate 40 further has a planar electrode 411 arranged on the dielectric layer closest to the principal surface 40a among the multiple dielectric layers and joined to the bump electrode 70 (122), a planar electrode 444 arranged on the dielectric layer closest to the principal surface 40b among the multiple dielectric layers and connected to ground, and an inductor 33 connected between the planar electrode 411 and the planar electrode 444.

[0129] According to this, by connecting the inductor 33 to the parallel arm resonator p23, the interval between the resonant frequency and anti-resonant frequency of the parallel arm resonator p23 is widened, and the attenuation pole due to the resonant frequency of the parallel arm resonator p23 can be positioned on the low-frequency side within the pass band of the filter 10. Therefore, the attenuation characteristics can be improved over a wide band on the low-frequency side of the pass band of the filter 20.

[0130] Moreover, the multiplexer 1 according to this embodiment includes a common terminal 100, the above-described filter 20 having an input terminal 102 connected to the common terminal 100, and a filter 10 connected to the common terminal 100 and having a passband located on the lower frequency side than the filter 20.

[0131] This makes it possible to provide a multiplexer 1 in which degradation of the isolation characteristics on the high frequency side of the pass band of the filter 10 is suppressed.

[0132] (Other embodiments) Although the elastic wave device and multiplexer according to the present invention have been described above with reference to the embodiments, the present invention is not limited to the above-described embodiments. The present invention also includes modifications that can be made by those skilled in the art without departing from the spirit of the present invention, and various devices incorporating the elastic wave device and multiplexer according to the present invention.

[0133] Furthermore, for example, in the acoustic wave devices and multiplexers according to the above-described embodiments, matching elements such as inductors and capacitors, and switch circuits may be connected between the respective components.

[0134] The resonant frequency and anti-resonant frequency shown in the above-described embodiments are derived, for example, by contacting an RF probe with two input and output electrodes of an acoustic wave resonator and measuring the reflection characteristics.

[0135] Features of the acoustic wave device and the multiplexer described based on the above embodiment and modifications will be described below.

[0136] <1> a first series arm resonator disposed in a series arm path connecting the first input / output terminal and the second input / output terminal; a plurality of parallel arm resonators connected between the series arm path and a ground; A first substrate having a first main surface and a second main surface opposed to each other and having a plurality of dielectric layers; a second substrate having a third main surface disposed opposite the first main surface; a first bump electrode disposed on the third main surface; The first series arm resonator includes: a first functional electrode disposed on the third major surface; A first parallel arm resonator of the plurality of parallel arm resonators includes: a second functional electrode disposed on the third major surface; the first bump electrode is connected to the second functional electrode; The first substrate is a first planar electrode disposed on a first dielectric layer of the plurality of dielectric layers and joined to the first bump electrode; a second planar electrode disposed on a second dielectric layer of the plurality of dielectric layers closer to the second principal surface than the first dielectric layer, and connected to ground; a plurality of via conductors connecting the first planar electrode and the second planar electrode; When the first main surface is viewed in plan, the first bump electrode is located between two of the plurality of via conductors connected to the first planar electrode, The first parallel arm resonator has the highest resonant frequency among the multiple parallel arm resonators.

[0137] <2> the second substrate has piezoelectric properties; Each of the first functional electrode and the second functional electrode is an IDT electrode. <1> The acoustic wave device according to claim 1 .

[0138] <3> each of the first functional electrode and the second functional electrode includes, in order from the third principal surface, a third planar electrode, a piezoelectric thin film, and a fourth planar electrode; <1> The acoustic wave device according to claim 1 .

[0139] <4> a first series arm resonator disposed in a series arm path connecting the first input / output terminal and the second input / output terminal; a plurality of parallel arm resonators connected between the series arm path and a ground; A first substrate having a first main surface and a second main surface opposed to each other and having a plurality of dielectric layers; a second substrate having a third main surface disposed opposite the first main surface; a first bump electrode disposed on the third main surface; The first series arm resonator includes: a first functional electrode disposed on the third major surface; A first parallel arm resonator of the plurality of parallel arm resonators includes: a second functional electrode disposed on the third major surface; the first bump electrode is connected to the second functional electrode; The first substrate is a first planar electrode disposed on a first dielectric layer of the plurality of dielectric layers and joined to the first bump electrode; a second planar electrode disposed on a second dielectric layer of the plurality of dielectric layers closer to the second principal surface than the first dielectric layer, and connected to ground; a plurality of via conductors connecting the first planar electrode and the second planar electrode; When the first main surface is viewed in plan, the first bump electrode is located between two of the plurality of via conductors connected to the first planar electrode, each of the first functional electrode and the second functional electrode is an IDT electrode; The first parallel arm resonator is an acoustic wave device in which the electrode finger pitch of the IDT electrode is the smallest among the multiple parallel arm resonators.

[0140] <5> the plurality of parallel arm resonators include the first parallel arm resonator and a second parallel arm resonator, the first parallel arm resonator is connected to a path connecting the first input / output terminal and the first series arm resonator and to the first bump electrode; the second parallel arm resonator is connected to a path connecting the second input / output terminal and the first series arm resonator and to the first bump electrode. <1> ~ <4> 2. The acoustic wave device according to claim 1 ,

[0141] <6> the first planar electrode is disposed on the first major surface; <1> ~ <5> 2. The acoustic wave device according to claim 1 ,

[0142] <7> the second planar electrode is disposed on the second major surface; <1> ~ <6> 2. The acoustic wave device according to claim 1 ,

[0143] <8> The second planar electrode is an external connection terminal. <7> The acoustic wave device according to claim 1 .

[0144] <9> When the first main surface is viewed in a plan view, the first bump electrode is located between two of the plurality of via conductors connected to the first planar electrode, and is located between two via conductors located on a virtual line intersecting a virtual line segment connecting the two via conductors. <1> ~ <8> 2. The acoustic wave device according to claim 1 ,

[0145] <10> a plurality of bump electrodes including the first bump electrode are disposed on the third main surface; a second bump electrode and a third bump electrode among the plurality of bump electrodes are disposed at both end portions of an outer side of the second substrate in a plan view of the third main surface, the first bump electrode is located between the second bump electrode and the third bump electrode in a plan view of the third main surface; <1> ~ <9> 2. The acoustic wave device according to claim 1 ,

[0146] <11> the first parallel arm resonator has the smallest capacitance among the plurality of parallel arm resonators; <1> ~ <10> 2. The acoustic wave device according to claim 1 ,

[0147] <12> the plurality of parallel arm resonators include the first parallel arm resonator and a third parallel arm resonator, The third parallel arm resonator is The second substrate; a third functional electrode disposed on the third principal surface; a fourth bump electrode disposed on the third main surface and connected to the third functional electrode; The first substrate further comprises: a fifth planar electrode disposed on a dielectric layer among the plurality of dielectric layers closest to the first principal surface side and joined to the fourth bump electrode; a sixth planar electrode that is disposed on the dielectric layer among the plurality of dielectric layers closest to the second principal surface and is connected to ground; an inductor connected between the fifth planar electrode and the sixth planar electrode. <1> ~ <11> 2. The acoustic wave device according to claim 1 ,

[0148] <13> A common terminal; The first input / output terminal is connected to the common terminal. <1> ~ <12> and an elastic wave device according to any one of the preceding claims. a filter connected to the common terminal and having a passband located at a lower frequency than the acoustic wave device. [Industrial Applicability]

[0149] INDUSTRIAL APPLICABILITY The present invention can be widely used in communication devices such as mobile phones as an elastic wave device or multiplexer with low loss and high attenuation that can be applied to multi-band frequency standards. [Explanation of symbols]

[0150] 1 Multiplexer 2 Filter Tips 10, 20 Filter 31, 32, 33 Inductors 40 Multilayer Board 40a, 40b, 50a, 50b main surface 50 Piezoelectric Substrate 51 High-sonic support substrate 52 Low sound velocity membrane 53 Piezoelectric Film 54, 54p, 54s IDT electrode 55, 58 protective layer 57 Piezoelectric single crystal substrate 60 Elastic Wave Resonator 60a, 60b comb-shaped electrode 61a, 61b electrode fingers 62a, 62b Busbar electrodes 65 Support substrate 66 Lower electrode 67 Piezoelectric layer 68 Upper electrode 70, 70(100), 70(110), 70(111), 70(112), 70(113), 70(120), 70(121), 70(122) Bump electrode 81, 81a, 81b, 81c, 81d Via conductor 100 Common terminal 101, 120 Output terminals 102, 110 Input terminals 111, 112, 113, 121, 122 terminals 410, 411, 420, 430, 440, 441, 442, 443, 444, 510 Planar electrode 540 Adhesion layer 542 Main electrode layer L1, L2, L3 dielectric layers L41, L42, L43, L44 electrode layer p11, p12, p13, p14, p21, p22, p23, p24 Parallel arm resonators s11, s12, s13, s14, s21, s22, s23, s24 Series arm resonators

Claims

1. a first series arm resonator disposed in a series arm path connecting the first input / output terminal and the second input / output terminal; a plurality of parallel arm resonators connected between the series arm path and a ground; A first substrate having a first main surface and a second main surface opposed to each other and having a plurality of dielectric layers; a second substrate having a third main surface disposed opposite the first main surface; a first bump electrode disposed on the third main surface; The first series arm resonator includes: a first functional electrode disposed on the third major surface; A first parallel arm resonator of the plurality of parallel arm resonators includes: a second functional electrode disposed on the third major surface; the first bump electrode is connected to the second functional electrode; The first substrate is a first planar electrode disposed on a first dielectric layer of the plurality of dielectric layers and joined to the first bump electrode; a second planar electrode disposed on a second dielectric layer of the plurality of dielectric layers closer to the second principal surface than the first dielectric layer, the second planar electrode being connected to ground; a plurality of via conductors connecting the first planar electrode and the second planar electrode; When the first main surface is viewed in a plan view, the first bump electrode is located between two of the plurality of via conductors connected to the first planar electrode, the first parallel arm resonator has the highest resonant frequency among the plurality of parallel arm resonators; Elastic wave device.

2. the second substrate has piezoelectric properties; each of the first functional electrode and the second functional electrode is an IDT electrode; The acoustic wave device according to claim 1 .

3. each of the first functional electrode and the second functional electrode includes, in order from the third principal surface, a third planar electrode, a piezoelectric thin film, and a fourth planar electrode; The acoustic wave device according to claim 1 .

4. a first series arm resonator disposed in a series arm path connecting the first input / output terminal and the second input / output terminal; a plurality of parallel arm resonators connected between the series arm path and a ground; A first substrate having a first main surface and a second main surface opposed to each other and having a plurality of dielectric layers; a second substrate having a third main surface disposed opposite the first main surface; a first bump electrode disposed on the third main surface; The first series arm resonator is a first functional electrode disposed on the third major surface; A first parallel arm resonator of the plurality of parallel arm resonators includes: a second functional electrode disposed on the third major surface; the first bump electrode is connected to the second functional electrode; The first substrate is a first planar electrode disposed on a first dielectric layer of the plurality of dielectric layers and joined to the first bump electrode; a second planar electrode disposed on a second dielectric layer of the plurality of dielectric layers closer to the second principal surface than the first dielectric layer, the second planar electrode being connected to ground; a plurality of via conductors connecting the first planar electrode and the second planar electrode; When the first main surface is viewed in a plan view, the first bump electrode is located between two of the plurality of via conductors connected to the first planar electrode, each of the first functional electrode and the second functional electrode is an IDT electrode; the first parallel arm resonator has an IDT electrode with a smallest electrode finger pitch among the plurality of parallel arm resonators; Elastic wave device.

5. the plurality of parallel arm resonators include the first parallel arm resonator and a second parallel arm resonator, the first parallel arm resonator is connected to a path connecting the first input / output terminal and the first series arm resonator and to the first bump electrode; the second parallel arm resonator is connected to a path connecting the second input / output terminal and the first series arm resonator and to the first bump electrode. The elastic wave device according to any one of claims 1 to 4.

6. the first planar electrode is disposed on the first major surface; The elastic wave device according to any one of claims 1 to 4.

7. the second planar electrode is disposed on the second major surface; The elastic wave device according to any one of claims 1 to 4.

8. The second planar electrode is an external connection terminal. The acoustic wave device according to claim 7 .

9. When the first main surface is viewed in a plan view, the first bump electrode is located between two of the plurality of via conductors connected to the first planar electrode, and is located between two via conductors located on a virtual line intersecting a virtual line segment connecting the two via conductors. The elastic wave device according to any one of claims 1 to 4.

10. a plurality of bump electrodes including the first bump electrode are disposed on the third main surface; a second bump electrode and a third bump electrode among the plurality of bump electrodes are disposed at both end portions of an outer side of the second substrate in a plan view of the third main surface, the first bump electrode is located between the second bump electrode and the third bump electrode in a plan view of the third main surface; The elastic wave device according to any one of claims 1 to 4.

11. the first parallel arm resonator has the smallest capacitance among the plurality of parallel arm resonators; The elastic wave device according to any one of claims 1 to 4.

12. the plurality of parallel arm resonators include the first parallel arm resonator and a third parallel arm resonator, The third parallel arm resonator is The second substrate; a third functional electrode disposed on the third principal surface; a fourth bump electrode disposed on the third main surface and connected to the third functional electrode; The first substrate further comprises: a fifth planar electrode disposed on a dielectric layer among the plurality of dielectric layers closest to the first main surface side and joined to the fourth bump electrode; a sixth planar electrode that is disposed on the dielectric layer closest to the second principal surface among the plurality of dielectric layers and is connected to ground; an inductor connected between the fifth planar electrode and the sixth planar electrode. The elastic wave device according to any one of claims 1 to 4.

13. A common terminal; the first input / output terminal is connected to the common terminal; and a filter connected to the common terminal and having a passband located at a lower frequency side than the elastic wave device. Multiplexer.

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