WO2024080205A1 - Dispositif de filtre - Google Patents

Dispositif de filtre Download PDF

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Publication number
WO2024080205A1
WO2024080205A1 PCT/JP2023/036224 JP2023036224W WO2024080205A1 WO 2024080205 A1 WO2024080205 A1 WO 2024080205A1 JP 2023036224 W JP2023036224 W JP 2023036224W WO 2024080205 A1 WO2024080205 A1 WO 2024080205A1
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WIPO (PCT)
Prior art keywords
acoustic wave
piezoelectric substrate
piezoelectric
resonator
filter device
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PCT/JP2023/036224
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English (en)
Japanese (ja)
Inventor
直 山崎
泰伸 林
康政 谷口
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株式会社村田製作所
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Publication of WO2024080205A1 publication Critical patent/WO2024080205A1/fr

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/25—Constructional features of resonators using surface acoustic waves
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/64—Filters using surface acoustic waves

Definitions

  • the present invention relates to a filter device having an elastic wave resonator.
  • Patent Document 1 discloses an example of an acoustic wave device as a filter device.
  • This acoustic wave device is a duplexer.
  • two piezoelectric substrates are provided on a support substrate. Both of the two piezoelectric substrates are lithium tantalate substrates.
  • the two piezoelectric substrates have different cut angles. This causes the electromechanical coupling coefficients of the two piezoelectric substrates to differ from each other.
  • the parallel arm resonator of the transmit filter and the series arm resonator of the receive filter are configured on the piezoelectric substrate with the smaller electromechanical coupling coefficient.
  • a stack structure may be adopted.
  • a set of laminated substrates are stacked.
  • a filter is formed in each of the laminated substrates.
  • a filter device having a stack structure includes a set of acoustic wave devices. Even if the acoustic wave device described in Patent Document 1 is adopted as one of the acoustic wave devices in such a filter device, there is a risk that it may not be possible to achieve both sufficient steepness in the filter characteristics and sufficient power resistance.
  • the object of the present invention is to provide a filter device with a stack structure that can suppress deterioration in the steepness of the filter characteristics and can increase power durability.
  • a first piezoelectric substrate has a first main surface and a second main surface opposed to each other, at least one first elastic wave resonator which includes an IDT electrode provided on the first main surface of the first piezoelectric substrate and is a series arm resonator or a parallel arm resonator, a support provided on the first main surface of the first piezoelectric substrate and arranged to surround the first elastic wave resonator, a second piezoelectric substrate provided on the support and having a third main surface located on the first piezoelectric substrate side and a fourth main surface facing the third main surface, and at least one second elastic wave resonator which includes an IDT electrode provided on the third main surface of the second piezoelectric substrate and is a series arm resonator
  • the first piezoelectric substrate has a first support substrate and a first piezoelectric layer laminated with the first support substrate, and the first The main surface includes the main surface of the first piezoelectric layer, the second piezoelectric layer
  • a first piezoelectric substrate has a first main surface and a second main surface opposed to each other, at least one first elastic wave resonator including an IDT electrode provided on the first main surface of the first piezoelectric substrate and being a series arm resonator or a parallel arm resonator, a support provided on the first main surface of the first piezoelectric substrate and arranged to surround the first elastic wave resonator, a second piezoelectric substrate provided on the support and having a third main surface located on the first piezoelectric substrate side and a fourth main surface facing the third main surface, and at least one second elastic wave resonator including an IDT electrode provided on the third main surface of the second piezoelectric substrate, at least one of which is a parallel arm resonator, the first piezoelectric substrate having a first support substrate and a first piezoelectric layer laminated with the first support substrate,
  • the main surface of the piezoelectric resonator includes the main surface of the
  • the present invention provides a filter device with a stack structure that can suppress deterioration in steepness of the filter characteristics and improve power durability.
  • FIG. 1 is a circuit diagram of a filter device according to a first embodiment of the present invention.
  • FIG. 2 is a schematic front cross-sectional view of the filter device according to the first embodiment of the present invention.
  • FIG. 3 is a schematic perspective plan view showing an electrode configuration on a first main surface of a first piezoelectric substrate in the first embodiment of the present invention.
  • FIG. 4 is a schematic plan view showing an electrode configuration on a third main surface of a second piezoelectric substrate in the first embodiment of the present invention.
  • FIG. 5 is a schematic perspective plan view showing an electrode configuration on a fourth main surface of a second piezoelectric substrate in the first embodiment of the present invention.
  • FIG. 6 is a schematic cross-sectional view showing a portion taken along line II-II in FIG. FIG.
  • FIG. 7 is a graph showing the relationship between the thickness of the lithium tantalate layer and the band width ratio.
  • FIG. 8 is a diagram showing the relationship between the cut angle of the lithium tantalate layer and the band width ratio.
  • FIG. 9 is a schematic perspective plan view illustrating an electrode configuration of a first acoustic wave resonator according to a first preferred embodiment of the present invention.
  • FIG. 10 is a schematic cross-sectional view showing a portion of a filter device according to a modified example of the first embodiment of the present invention, which corresponds to the cross-section shown in FIG.
  • FIG. 11 is a schematic front cross-sectional view of a filter device according to a third embodiment of the present invention.
  • FIG. 12 is a schematic front cross-sectional view of a filter device according to a fourth embodiment of the present invention.
  • FIG. 13 is a schematic front cross-sectional view of a filter device according to a fifth embodiment of the present invention.
  • FIG. 14 is a schematic diagram of impedance frequency characteristics of a first elastic wave resonator and a second elastic wave resonator according to the fifth embodiment of the present invention.
  • FIG. 15 is a schematic diagram of the attenuation frequency characteristics of the filter device according to the fifth embodiment of the present invention.
  • FIG. 16 is a schematic diagram illustrating impedance frequency characteristics of a first elastic wave resonator and a second elastic wave resonator according to the sixth embodiment of the present invention.
  • FIG. 17 is a schematic diagram of the attenuation frequency characteristics of the filter device according to the sixth embodiment of the present invention.
  • FIG. 18 is a schematic front cross-sectional view of a filter device according to a seventh embodiment of the present invention.
  • FIG. 19 is a schematic front cross-sectional view of a filter device according to a ninth embodiment of the present invention.
  • FIG. 20 is a diagram showing the relationship between the standard value of the thickness of the intermediate layer and the band width ratio.
  • FIG. 21 is a diagram showing the relationship between the thickness of the piezoelectric layer and the thickness of the intermediate layer and the phase of the harmonics.
  • FIG. 22 is a schematic front cross-sectional view of a filter device according to a tenth embodiment of the present invention.
  • FIG. 23 is a schematic front sectional view for explaining the effect of the tenth embodiment of the present invention.
  • FIG. 24 is a schematic front cross-sectional view of a filter device according to an eleventh embodiment of the present invention.
  • FIG. 25 is a schematic front sectional view for explaining the effect of the eleventh embodiment of the present invention.
  • FIG. 26 is a schematic front cross-sectional view of a filter device according to a twelfth embodiment of the present invention.
  • FIG. 27 is a diagram showing the relationship between ⁇ in the Euler angles ( ⁇ , ⁇ , ⁇ ) of the support substrate and the phases of the Rayleigh wave and the harmonic waves.
  • FIG. 28 is a diagram showing a case where the phase is ⁇ 60° or less in the relationship shown in FIG. FIG.
  • FIG. 29 is a schematic cross-sectional front view of a filter device according to a fourteenth embodiment of the present invention.
  • FIG. 30 is a diagram showing the relationship between the thickness of the IDT electrode and TCFa.
  • FIG. 31 is a diagram showing the relationship between the thickness of the IDT electrode and TCFr.
  • FIG. 32 is a schematic cross-sectional front view of a filter device according to a fifteenth embodiment of the present invention.
  • FIG. 33 is a schematic perspective plan view showing an arrangement of acoustic wave resonators on a first main surface of a first piezoelectric substrate in a sixteenth embodiment of the present invention.
  • FIG. 30 is a diagram showing the relationship between the thickness of the IDT electrode and TCFa.
  • FIG. 31 is a diagram showing the relationship between the thickness of the IDT electrode and TCFr.
  • FIG. 32 is a schematic cross-sectional front view of a filter device according to a fifteenth embodiment of the present invention.
  • FIG. 33 is a
  • FIG. 34 is a schematic plan view showing an arrangement of acoustic wave resonators on a third main surface of a second piezoelectric substrate in a sixteenth embodiment of the present invention.
  • FIG. 35 is a schematic front cross-sectional view of a filter device according to a seventeenth embodiment of the present invention.
  • FIG. 36 is a diagram showing the relationship between the thickness of the dielectric film and the band width ratio.
  • FIG. 37 is a schematic cross-sectional front view of a filter device according to an eighteenth embodiment of the present invention.
  • FIG. 1 is a circuit diagram of a filter device according to a first embodiment of the present invention.
  • the filter device 10 of this embodiment is a transmit filter.
  • the pass band of the filter device 10 is 1850 MHz to 1915 MHz, which is the transmit band of Band 25.
  • the pass band of the filter device 10 is not limited to the above.
  • the filter device 10 is not limited to a transmit filter.
  • the filter device 10 may be, for example, a receive filter. In this embodiment, the filter device 10 is only one filter.
  • the filter device according to the present invention may be a duplexer or a multiplexer having three or more filters.
  • the filter device 10 is a ladder-type filter. Therefore, the filter device 10 has at least one series arm resonator and at least one parallel arm resonator. In this embodiment, both the series arm resonator and the parallel arm resonator are surface acoustic wave resonators. The specific configuration of the filter device 10 will be described below.
  • FIG. 2 is a schematic front cross-sectional view of a filter device according to a first embodiment of the present invention.
  • each resonator is shown as a rectangle with two diagonal lines added.
  • the portion shown in FIG. 2 is shown diagrammatically as having a bump, which will be described later. The same applies to other schematic cross-sectional views.
  • the filter device 10 has a first piezoelectric substrate 2A, a second piezoelectric substrate 2B, and a support 8A.
  • the support 8A is provided between the first piezoelectric substrate 2A and the second piezoelectric substrate 2B.
  • the support 8A has a frame-like shape.
  • a space is defined by the first piezoelectric substrate 2A, the second piezoelectric substrate 2B, and the support 8A.
  • the first piezoelectric substrate 2A and the second piezoelectric substrate 2B face each other across the space and the support 8A.
  • the first piezoelectric substrate 2A is a laminated substrate including a first piezoelectric layer 5A.
  • the first piezoelectric substrate 2A has a first main surface 2a and a second main surface 2b.
  • the first main surface 2a and the second main surface 2b face each other.
  • the main surface of the first piezoelectric layer 5A is the first main surface 2a.
  • the second piezoelectric substrate 2B is a laminated substrate including a second piezoelectric layer 5B.
  • the second piezoelectric substrate 2B has a third main surface 2c and a fourth main surface 2d.
  • the third main surface 2c and the fourth main surface 2d face each other.
  • the main surface of the second piezoelectric layer 5B is the third main surface 2c.
  • rotated Y-cut lithium niobate is used as the material for the first piezoelectric layer 5A and the second piezoelectric layer 5B.
  • the material for the first piezoelectric layer 5A and the second piezoelectric layer 5B is not limited to the above, and for example, lithium tantalate can also be used.
  • the first piezoelectric substrate 2A and the second piezoelectric substrate 2B have different electromechanical coupling coefficients Ksaw. Specifically, the electromechanical coupling coefficient Ksaw of the second piezoelectric substrate 2B is smaller than the electromechanical coupling coefficient Ksaw of the first piezoelectric substrate 2A.
  • the electromechanical coupling coefficient Ksaw of the piezoelectric substrate can be adjusted, for example, by the thickness and cut angle of the piezoelectric layer. In this embodiment, the thickness of the first piezoelectric layer 5A is 400 nm, and the cut angle of the first piezoelectric layer 5A is 35°Y. The thickness of the second piezoelectric layer 5B is 600 nm, and the cut angle of the second piezoelectric layer 5B is 55°Y.
  • a first elastic wave resonator 13A is configured on the first piezoelectric substrate 2A.
  • a second elastic wave resonator 13B is configured on the second piezoelectric substrate 2B.
  • the first elastic wave resonator 13A and the second elastic wave resonator 13B are each a series arm resonator or a parallel arm resonator.
  • the electromechanical coupling coefficient Ksaw of the first piezoelectric substrate 2A is the electromechanical coupling coefficient Ksaw associated with the main mode used by the first elastic wave resonator 13A.
  • the electromechanical coupling coefficient Ksaw of the second piezoelectric substrate 2B is the electromechanical coupling coefficient Ksaw associated with the main mode used by the second elastic wave resonator 13B.
  • each piezoelectric substrate is shown in Figures 3 and 4. Note that in Figures 3 and 4, the first elastic wave resonator 13A and the second elastic wave resonator 13B are indicated by the symbols of the series arm resonators or parallel arm resonators shown in Figure 1.
  • FIG. 3 is a schematic perspective plan view showing the electrode configuration on the first main surface of the first piezoelectric substrate in the first embodiment.
  • FIG. 4 is a schematic plan view showing the electrode configuration on the third main surface of the second piezoelectric substrate in the first embodiment.
  • FIG. 5 is a schematic perspective plan view showing the electrode configuration on the fourth main surface of the second piezoelectric substrate in the first embodiment.
  • Arrow A in FIGS. 3 and 4 typically shows the path from the input end side to the output end side in the filter device 10. Note that FIG. 2 above is a schematic cross-sectional view taken along line I-I in FIG. 3.
  • a plurality of first acoustic wave resonators are configured on the first main surface 2a of the first piezoelectric substrate 2A.
  • a plurality of functional electrodes are provided on the first main surface 2a of the first piezoelectric substrate 2A.
  • Each of the first acoustic wave resonators includes a functional electrode.
  • each functional electrode is an IDT electrode.
  • a plurality of wirings and the support 8A are provided on the first main surface 2a.
  • the upper two-dot chain line in FIG. 3 indicates the boundary between the support 8A and the wiring.
  • the first acoustic wave resonators are electrically connected to each other by the wiring.
  • the support 8A is provided so as to surround the multiple first acoustic wave resonators. More specifically, the support 8A surrounds the multiple functional electrodes provided on the first main surface 2a. As described above, in this embodiment, the support 8A has a frame-like shape. Note that multiple columnar supports may be provided on the first main surface 2a so as to surround the multiple first acoustic wave resonators.
  • the second piezoelectric substrate 2B shown in FIG. 4 is provided on the support 8A.
  • a plurality of second elastic wave resonators are configured on the second piezoelectric substrate 2B.
  • a plurality of IDT electrodes are provided as a plurality of functional electrodes on the third main surface 2c of the second piezoelectric substrate 2B.
  • Each second elastic wave resonator includes an IDT electrode.
  • a plurality of wirings are provided on the third main surface 2c. The second elastic wave resonators are electrically connected to each other by the wirings.
  • a plurality of first elastic wave resonators 13A and a plurality of second elastic wave resonators 13B are positioned within a space surrounded by the first piezoelectric substrate 2A, the second piezoelectric substrate 2B, and the support 8A.
  • the filter device 10 has a stack structure.
  • the plurality of second elastic wave resonators 13B are all series arm resonators.
  • the plurality of second elastic wave resonators 13B include at least one of a series arm resonator and a parallel arm resonator.
  • the filter device 10 has at least one pillar member 8B. Specifically, in this embodiment, the filter device 10 has multiple pillar members 8B.
  • the first piezoelectric substrate 2A and the second piezoelectric substrate 2B are supported by the support 8A as well as the pillar member 8B.
  • the support 8A and the pillar member 8B are a laminate of multiple metal layers.
  • the support 8A and the pillar member 8B are electrically connected to the first elastic wave resonator 13A or the second elastic wave resonator 13B via each wiring.
  • the first elastic wave resonator 13A and the second elastic wave resonator 13B in the filter device 10 are electrically connected by a portion of the multiple pillar members 8B out of all the pillar members 8B.
  • FIG. 6 is a schematic cross-sectional view showing a portion along line II-II in FIG. 3.
  • the filter device 10 has a plurality of external connection terminals 11. A portion of the external connection terminals 11 penetrates the second piezoelectric substrate 2B. Each external connection terminal 11 is connected to the support 8A or the pillar member 8B. Furthermore, a bump 9 is bonded to each external connection terminal 11 as a conductive bonding member. Note that, for example, a conductive adhesive may be used as the conductive bonding member.
  • the filter device 10 is bonded to a mounting board or the like by the plurality of bumps 9.
  • Each of the first elastic wave resonators 13A and each of the second elastic wave resonators 13B are electrically connected to the outside via the external connection terminals 11 and the bumps 9.
  • this embodiment is characterized by the following configuration: 1) The electromechanical coupling coefficient Ksaw of the second piezoelectric substrate 2B is smaller than the electromechanical coupling coefficient Ksaw of the first piezoelectric substrate 2A. 2)
  • the second acoustic wave resonators 13B include a series arm resonator having the lowest anti-resonance frequency among all the series arm resonators configured in the first piezoelectric substrate 2A and the second piezoelectric substrate 2B. This makes it possible to suppress deterioration of the steepness of the filter characteristics and to improve power durability. In this specification, high steepness means that the amount of change in frequency is small for a certain amount of change in attenuation near the end of the pass band. The above effects will be described in detail below.
  • the resonant frequencies of the series arm resonators that form the pass band are located within the pass band.
  • the anti-resonant frequencies of the series arm resonators are located higher than the pass band.
  • the lower the anti-resonant frequency of a series arm resonator the closer the anti-resonant frequency is to the pass band of the ladder-type filter. Therefore, the series arm resonator with the lowest anti-resonant frequency among the series arm resonators of the ladder-type filter has a particularly large effect on the steepness near the high-frequency end of the pass band. Therefore, if the anti-resonant frequency of the series arm resonator changes significantly, there is a risk that the steepness will deteriorate.
  • an elastic wave resonator such as a series arm resonator
  • heat is generated when an elastic wave is excited. Therefore, when the filter device is used, the temperature of each elastic wave resonator changes.
  • the series arm resonator with the lowest anti-resonance frequency is particularly prone to heat generation. This is because the anti-resonance frequency of the series arm resonator is the closest to the pass band among the anti-resonance frequencies of the series arm resonators of the ladder filter. If the temperature of the elastic wave resonator changes significantly, the anti-resonance frequency also changes significantly. Therefore, there is a risk that the steepness near the high-frequency end of the pass band of the ladder filter will deteriorate further. Furthermore, the IDT electrode of the series arm resonator will become hot, and the IDT electrode may be damaged.
  • the series arm resonator with the lowest anti-resonance frequency among the series arm resonators of the filter device 10 is the second acoustic wave resonator 13B configured on the second piezoelectric substrate 2B.
  • the electromechanical coupling coefficient Ksaw of the second piezoelectric substrate 2B is smaller than the electromechanical coupling coefficient Ksaw of the first piezoelectric substrate 2A.
  • the smaller the electromechanical coupling coefficient Ksaw the smaller the thermal resistance. Therefore, it is possible to improve the heat dissipation in the part of the filter device 10 where the series arm resonator with the lowest anti-resonance frequency is configured. This makes it possible to suppress deterioration of steepness near the high-frequency end of the passband. In addition, it is possible to suppress damage to the IDT electrode of the series arm resonator. In this way, it is possible to improve the power resistance.
  • the black arrow B in FIG. 6 indicates the path along which heat from the second acoustic wave resonator 13B moves to the outside.
  • the white arrow C in FIG. 6 indicates the path along which heat from the first acoustic wave resonator 13A moves to the outside.
  • the thermal resistance in the path indicated by the arrow B is smaller than the thermal resistance in the path indicated by the arrow C. This allows heat to be efficiently moved from the second acoustic wave resonator 13B to the outside. This makes it possible to suppress deterioration in the steepness of the filter characteristics and to improve power resistance.
  • the external connection terminal 11 is provided on the second piezoelectric substrate 2B. This allows heat to be transferred from the second acoustic wave resonator 13B to the outside more efficiently.
  • the external connection terminal 11 does not have to be provided on the second piezoelectric substrate 2B.
  • the external connection terminal 11 may be provided on the first piezoelectric substrate 2A.
  • the electromechanical coupling coefficient Ksaw of the piezoelectric substrate can be adjusted by the thickness and cut angle of the piezoelectric layer. This is shown by an example in which the piezoelectric layer is a lithium tantalate layer.
  • the electromechanical coupling coefficient Ksaw of the elastic wave resonator correlates with the relative bandwidth of the elastic wave resonator. Specifically, the larger the value of the relative bandwidth, the larger the electromechanical coupling coefficient Ksaw. Therefore, by showing an example of adjusting the relative bandwidth, it is shown that the electromechanical coupling coefficient Ksaw can be adjusted.
  • the relative bandwidth referred to here is expressed as (
  • Figure 7 shows the relationship between the thickness of the lithium tantalate layer and the band width ratio.
  • Figure 8 shows the relationship between the cut angle of the lithium tantalate layer and the band width ratio.
  • the thicker the lithium tantalate layer the smaller the band width.
  • the relationship between the thickness of the lithium tantalate layer and the band width is expressed by a linear function. Specifically, the slope of the change in the band width with respect to the change in the thickness of the lithium tantalate layer is -0.002%/nm.
  • the band width when the cut angle of the lithium tantalate layer is changed, the band width also changes. As described above, the band width can be adjusted by adjusting the thickness or cut angle of the piezoelectric layer. There is a correlation between the band width and the electromechanical coupling coefficient Ksaw. Therefore, the electromechanical coupling coefficient Ksaw can be adjusted by adjusting the thickness or cut angle of the piezoelectric layer.
  • the filter device 10 has a first signal terminal 12A and a second signal terminal 12B.
  • the first signal terminal 12A corresponds to the input terminal
  • the second signal terminal 12B corresponds to the output terminal.
  • the multiple series arm resonators of the filter device 10 are specifically series arm resonator S1, series arm resonator S2, series arm resonator S3, series arm resonator S4, series arm resonator S5, series arm resonator S6, and series arm resonator S7.
  • the series arm resonator S1, series arm resonator S2, series arm resonator S3, series arm resonator S4, series arm resonator S5, series arm resonator S6, and series arm resonator S7 are connected in series with each other in this order.
  • the parallel arm resonators of the filter device 10 are specifically parallel arm resonators P1, P2, P3, P4, P5, and P6.
  • the parallel arm resonator P1 is connected between the connection point between the series arm resonators S1 and S2 and ground potential.
  • the parallel arm resonator P2 is connected between the connection point between the series arm resonators S2 and S3 and ground potential.
  • the parallel arm resonator P3 is connected between the connection point between the series arm resonators S3 and S4 and ground potential.
  • the parallel arm resonator P4 is connected between the connection point between the series arm resonators S4 and S5 and ground potential.
  • the parallel arm resonator P5 is connected between the connection point between the series arm resonators S5 and S6 and ground potential.
  • the parallel arm resonator P6 is connected between the connection point between the series arm resonators S6 and S7 and ground potential.
  • the series arm resonator S2, the series arm resonator S7 and all the parallel arm resonators are the first elastic wave resonators 13A.
  • the series arm resonator S1, the series arm resonator S3, the series arm resonator S4, the series arm resonator S5 and the series arm resonator S6 are the second elastic wave resonators 13B.
  • Any of the series arm resonators shown in FIG. 4 is the series arm resonator with the lowest anti-resonance frequency in the filter device 10.
  • FIG. 9 shows a specific configuration of the first elastic wave resonator 13A and the second elastic wave resonator 13B.
  • FIG. 9 is a schematic perspective plan view showing the electrode configuration of the first elastic wave resonator in the first embodiment.
  • wiring connected to the first elastic wave resonator 13A and the like are omitted.
  • the first acoustic wave resonator 13A has an IDT electrode 15 and a pair of reflectors 14A and 14B.
  • the IDT electrode 15 and the reflectors 14A and 14B are provided on the first main surface 2a of the first piezoelectric substrate 2A.
  • the IDT electrode 15 has a pair of bus bars and a plurality of electrode fingers.
  • the pair of bus bars is specifically a first bus bar 16 and a second bus bar 17.
  • the first bus bar 16 and the second bus bar 17 face each other.
  • the plurality of electrode fingers is specifically a plurality of first electrode fingers 18 and a plurality of second electrode fingers 19.
  • One end of each of the plurality of first electrode fingers 18 is connected to the first bus bar 16.
  • One end of each of the plurality of second electrode fingers 19 is connected to the second bus bar 17.
  • the plurality of first electrode fingers 18 and the plurality of second electrode fingers 19 are interdigitated with each other.
  • the first electrode fingers 18 and the second electrode fingers 19 are connected to different potentials.
  • An acoustic wave is excited by applying an AC voltage to the IDT electrode 15.
  • the first electrode finger 18 and the second electrode finger 19 may be simply referred to as electrode fingers.
  • the direction in which the multiple electrode fingers of the IDT electrode 15 extend is the electrode finger extension direction.
  • the reflectors 14A and 14B face each other in a direction perpendicular to the electrode finger extension direction, sandwiching the IDT electrode 15 therebetween. In this embodiment, the direction perpendicular to the electrode finger extension direction is parallel to the elastic wave propagation direction.
  • the IDT electrode 15, the reflectors 14A, and the reflectors 14B may be made of a single-layer metal film or may be made of a laminated metal film.
  • each of the other first acoustic wave resonators 13A and each of the second acoustic wave resonators 13B shown in FIG. 2 and the like also have an IDT electrode and a pair of reflectors.
  • each of the first acoustic wave resonators 13A and each of the second acoustic wave resonators 13B are surface acoustic wave resonators.
  • Each external connection terminal 11 has at least one through electrode 7 and an electrode pad 6. Specifically, in this embodiment, a plurality of through electrodes 7 are provided so as to penetrate the second piezoelectric substrate 2B. A plurality of electrode pads 6 are provided on the fourth main surface 2d of the second piezoelectric substrate 2B. One end of each through electrode 7 is connected to the electrode pad 6. In this way, each external connection terminal 11 is formed. The other end of each through electrode 7 is connected to the support 8A or the pillar member 8B, etc.
  • the multiple external connection terminals 11 include an external connection terminal 11 that is connected to a signal potential, and an external connection terminal 11 that is connected to a ground potential.
  • the support 8A is connected to the through electrode 7 of the external connection terminal 11 that is connected to the ground potential.
  • Each of the parallel arm resonators of the multiple first elastic wave resonators 13A and the multiple second elastic wave resonators 13B is electrically connected to the support 8A via wiring. Thus, each parallel arm resonator is connected to the ground potential via the wiring, the support 8A, the external connection terminal 11, and the bump 9.
  • a wiring or a pillar member 8B is connected to the through electrode 7 of the external connection terminal 11, which is connected to the signal potential.
  • the elastic wave resonator closest to the first signal terminal 12A is the series arm resonator S1.
  • the series arm resonator S1 is configured on the second piezoelectric substrate 2B.
  • the series arm resonator S1 is connected to a wiring provided on the third main surface 2c of the second piezoelectric substrate 2B.
  • the through electrode 7 of the external connection terminal 11 on the input end side of the filter device 10 is connected to the wiring.
  • the elastic wave resonator closest to the second signal terminal 12B is the series arm resonator S7.
  • the series arm resonator S7 is configured on the first piezoelectric substrate 2A.
  • the series arm resonator S7 is connected to a wiring provided on the first main surface 2a of the first piezoelectric substrate 2A.
  • a pillar member 8B is connected to the wiring.
  • the through electrode 7 of the external connection terminal 11 on the output end side of the filter device 10 is connected to the pillar member 8B.
  • the support 8A may be connected to a signal potential or to a ground potential.
  • the pillar member 8B may be connected to a signal potential or to a ground potential.
  • each pillar member 8B is electrically connected to either the first elastic wave resonator 13A or the second elastic wave resonator 13B.
  • the multiple pillar members 8B may include a pillar member 8B that is not electrically connected to any of the elastic wave resonators.
  • the multiple external connection terminals 11 include an external connection terminal 11 that is connected to a signal potential and an external connection terminal 11 that is connected to a ground potential. However, the multiple external connection terminals 11 may also include an external connection terminal 11 that is not connected to either the signal potential or the ground potential.
  • One of the multiple metal layers of the support 8A is provided integrally with the wiring provided on the first piezoelectric substrate 2A.
  • the other metal layer of the support 8A is provided integrally with the wiring provided on the second piezoelectric substrate 2B.
  • the same is true for the pillar member 8B.
  • the metal layers of the support 8A and the pillar member 8B may be provided separately from the wiring and connected to the wiring.
  • one external connection terminal 11 has multiple through electrodes 7. This allows heat to be transferred more efficiently from the second piezoelectric substrate 2B side to the outside. This allows the temperature change of each second acoustic wave resonator 13B to be further reduced. In other words, it is possible to further reduce the temperature change of the series arm resonator having the lowest anti-resonance frequency among the series arm resonators of the filter device 10. Therefore, it is possible to further suppress deterioration of the steepness of the filter characteristics and further improve the power resistance.
  • the external connection terminal 11 does not necessarily have to have multiple through electrodes 7.
  • a dielectric film 28 is provided on the fourth main surface 2d of the second piezoelectric substrate 2B.
  • the dielectric film 28 covers a part of each electrode pad 6.
  • the bump 9 is bonded to the part of each electrode pad 6 that is not covered by the dielectric film 28.
  • the provision of the dielectric film 28 makes the second piezoelectric substrate 2B less likely to be damaged.
  • the dielectric film 28 is not provided on the second main surface 2b of the first piezoelectric substrate 2A.
  • the dielectric film 28 may also be provided on the second main surface 2b of the first piezoelectric substrate 2A.
  • the dielectric film 28 is a silicon oxide film. Note that the material of the dielectric film 28 is not limited to the above. The dielectric film 28 does not necessarily have to be provided.
  • the first piezoelectric substrate 2A is a laminated substrate. Specifically, the first piezoelectric substrate 2A has a first support substrate 3A, a first intermediate layer 4A, and a first piezoelectric layer 5A. The first intermediate layer 4A is provided on the first support substrate 3A. The first piezoelectric layer 5A is provided on the first intermediate layer 4A.
  • the first principal surface 2a of the first piezoelectric substrate 2A is the principal surface of the first piezoelectric substrate 2A that is located closest to the second piezoelectric substrate 2B.
  • the principal surface of the first piezoelectric layer 5A is the first principal surface 2a.
  • the first principal surface 2a may include at least the principal surface of the first piezoelectric layer 5A.
  • the first principal surface 2a may include the principal surface of the first piezoelectric layer 5A, as well as the principal surface of the first intermediate layer 4A or the principal surface of the first support substrate 3A.
  • the second principal surface 2b of the first piezoelectric substrate 2A faces the first principal surface 2a and is the principal surface located on the outermost side of the first piezoelectric substrate 2A. Therefore, in this embodiment, the second principal surface 2b is the principal surface of the first support substrate 3A that is located on the outermost side of the first piezoelectric substrate 2A.
  • the second piezoelectric substrate 2B is a laminate substrate of a second support substrate 3B, a second intermediate layer 4B, and a second piezoelectric layer 5B.
  • the third main surface 2c of the second piezoelectric substrate 2B is the main surface of the second piezoelectric substrate 2B that is located closest to the first piezoelectric substrate 2A.
  • the main surface of the second piezoelectric layer 5B is the third main surface 2c. It is sufficient that the third main surface 2c includes at least the main surface of the second piezoelectric layer 5B.
  • the third main surface 2c may include the main surface of the second piezoelectric layer 5B, as well as the main surface of the second intermediate layer 4B or the main surface of the second support substrate 3B.
  • the fourth principal surface 2d of the second piezoelectric substrate 2B faces the third principal surface 2c and is the outermost principal surface of the second piezoelectric substrate 2B. Therefore, in this embodiment, the fourth principal surface 2d is the outermost principal surface of the second piezoelectric substrate 2B of the second support substrate 3B.
  • the first intermediate layer 4A and the second intermediate layer 4B are low acoustic speed films.
  • a low acoustic speed film is a film with a relatively low acoustic speed. More specifically, the acoustic speed of the bulk wave propagating through the low acoustic speed film is lower than the acoustic speed of the bulk wave propagating through the piezoelectric layer. That is, the acoustic speed of the bulk wave propagating through the first intermediate layer 4A is lower than the acoustic speed of the bulk wave propagating through the first piezoelectric layer 5A. The acoustic speed of the bulk wave propagating through the second intermediate layer 4B is lower than the acoustic speed of the bulk wave propagating through the second piezoelectric layer 5B.
  • the first intermediate layer 4A and the second intermediate layer 4B are made of silicon oxide.
  • the materials of the first intermediate layer 4A and the second intermediate layer 4B as the low acoustic velocity film are not limited to the above, and for example, dielectrics such as glass, silicon oxide, silicon oxynitride, lithium oxide, tantalum oxide, or compounds of silicon oxide with fluorine, carbon, or boron added, or materials containing the above materials as the main components can be used.
  • the main component refers to a component that accounts for more than 50 wt%.
  • the above main component material may be in any of the following states: single crystal, polycrystalline, or amorphous, or a mixture of these.
  • the electromechanical coupling coefficient Ksaw of the first piezoelectric substrate 2A and the second piezoelectric substrate 2B may be adjusted by adjusting the thicknesses of the first intermediate layer 4A and the second intermediate layer 4B, etc.
  • the first support substrate 3A and the second support substrate 3B are high acoustic velocity material layers.
  • the high acoustic velocity material layer is a layer with a relatively high acoustic velocity.
  • the acoustic velocity of the bulk waves propagating through the high acoustic velocity material layer is higher than the acoustic velocity of the elastic waves propagating through the piezoelectric layer.
  • the acoustic velocity of the bulk waves propagating through the first support substrate 3A is higher than the acoustic velocity of the elastic waves propagating through the first piezoelectric layer 5A.
  • the acoustic velocity of the bulk waves propagating through the second support substrate 3B is higher than the acoustic velocity of the elastic waves propagating through the second piezoelectric layer 5B.
  • the first support substrate 3A and the second support substrate 3B are high sound velocity material layers made of silicon, which is a high sound velocity material.
  • the high sound velocity material is not limited to the above, and may be, for example, aluminum nitride, lithium tantalate, lithium niobate, piezoelectric material such as quartz, ceramic such as alumina, sapphire, magnesia, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, forsterite, spinel, sialon, dielectric material such as aluminum oxide, silicon oxynitride, DLC (diamond-like carbon), diamond, semiconductor such as silicon, or material mainly composed of the above material.
  • the spinel includes an aluminum compound containing one or more elements selected from Mg, Fe, Zn, Mn, etc. and oxygen.
  • Examples of the spinel include MgAl 2 O 4 , FeAl 2 O 4 , ZnAl 2 O 4 , and MnAl 2 O 4 .
  • first piezoelectric substrate 2A In the first piezoelectric substrate 2A, a first support substrate 3A as a high acoustic velocity material layer, a first intermediate layer 4A as a low acoustic velocity film, and a first piezoelectric layer 5A are laminated in this order. This allows the energy of the acoustic waves of each first acoustic wave resonator 13A to be effectively confined to the first piezoelectric layer 5A side.
  • the second piezoelectric substrate 2B also has a similar laminated structure. This allows the energy of the acoustic waves of each second acoustic wave resonator 13B to be effectively confined to the second piezoelectric layer 5B side.
  • the laminated structure of the first piezoelectric substrate is not limited to the above.
  • the first intermediate layer may be a laminate of a plurality of dielectric layers. More specifically, for example, the first intermediate layer may be a laminate of a first low acoustic velocity film and a first high acoustic velocity film as a high acoustic velocity material layer.
  • the first piezoelectric substrate may be a laminated substrate of a first support substrate, a first high acoustic velocity film, a first low acoustic velocity film, and a first piezoelectric layer.
  • the first intermediate layer may be a first high acoustic velocity film.
  • the first piezoelectric substrate may be a laminated substrate of a first support substrate, a first high acoustic velocity film, and a first piezoelectric layer.
  • the first intermediate layer may not be provided.
  • the first piezoelectric substrate may be a laminated substrate of a first support substrate and a first piezoelectric layer as a high acoustic velocity material layer. In these cases, the energy of the elastic waves of each first elastic wave resonator can be effectively trapped on the first piezoelectric layer side.
  • the second piezoelectric substrate may be a laminate substrate of a second support substrate, a second low acoustic velocity film, a second high acoustic velocity film, and a second piezoelectric layer.
  • the second piezoelectric substrate may be a laminate substrate of a second support substrate, a second high acoustic velocity film, and a second piezoelectric layer, or a laminate substrate of a second support substrate and a second piezoelectric layer as a high acoustic velocity material layer.
  • the first piezoelectric substrate has a first high acoustic velocity film
  • the energy of the acoustic waves of each first acoustic wave resonator can be effectively trapped on the first piezoelectric layer side.
  • the second piezoelectric substrate has a first high acoustic velocity film
  • the first support substrate and the second support substrate can be made of, 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; dielectric materials such as diamond and glass; semiconductors such as silicon and gallium nitride; or resins, or materials mainly composed of the above materials.
  • 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
  • dielectric materials such as diamond and glass
  • semiconductors such as silicon and gallium nitride
  • resins or materials mainly composed
  • the first piezoelectric substrate 2A may have a first support substrate 3A and a first piezoelectric layer 5A.
  • the first support substrate 3A and the first piezoelectric layer 5A may be directly laminated, or may be indirectly laminated via a first intermediate layer 4A.
  • the second piezoelectric substrate 2B may have a second support substrate 3B and a second piezoelectric layer 5B.
  • the second support substrate 3B and the second piezoelectric layer 5B may be directly laminated, or may be indirectly laminated via a second intermediate layer 4B.
  • each of the first acoustic wave resonators 13A and each of the second acoustic wave resonators 13B shown in FIG. 2 and the like is a surface acoustic wave resonator.
  • the resonant frequency and anti-resonant frequency of the surface acoustic wave resonators can be compared using the electrode finger pitch and duty ratio of the IDT electrodes.
  • the electrode finger pitch is the center-to-center distance in the acoustic wave propagation direction between adjacent electrode fingers connected to different potentials.
  • the resonant frequency of the surface acoustic wave resonator having a larger reciprocal of the product of the electrode finger pitch and the duty ratio is higher than the resonant frequency of the other surface acoustic wave resonator.
  • the anti-resonant frequency of the surface acoustic wave resonator having a larger reciprocal of the product of the electrode finger pitch and the duty ratio is higher than the anti-resonant frequency of the other surface acoustic wave resonator.
  • the resonant frequency of the surface acoustic wave resonator having a larger inverse of the product of the electrode finger pitch, duty ratio, and electrode finger thickness is higher than the resonant frequency of the other surface acoustic wave resonator.
  • the anti-resonant frequency of the surface acoustic wave resonator having a larger inverse of the product of the electrode finger pitch, duty ratio, and electrode finger thickness is higher than the anti-resonant frequency of the other surface acoustic wave resonator.
  • the inverse of the product of the electrode finger pitch of the IDT electrode and the duty ratio in any one of the second acoustic wave resonators 13B is the smallest.
  • the inverse of the product of the electrode finger pitch of the IDT electrode, the duty ratio, and the electrode finger thickness in any one of the second acoustic wave resonators 13B is the smallest among all the series arm resonators in the filter device 10. This makes it possible to more reliably make the anti-resonance frequency of the series arm resonator that is the second acoustic wave resonator 13B the lowest among all the series arm resonators in the filter device 10.
  • a protective film may be provided on the first main surface 2a of the first piezoelectric substrate 2A so as to cover the IDT electrodes of the first acoustic wave resonators 13A. This makes it difficult for the first acoustic wave resonators 13A to be damaged.
  • a protective film may be provided on the third main surface 2c of the second piezoelectric substrate 2B so as to cover the IDT electrodes of the second acoustic wave resonators 13B. This makes it difficult for the second acoustic wave resonators 13B to be damaged.
  • An appropriate dielectric may be used for the protective film. Note that in configurations other than the first embodiment of the present invention, a configuration in which a protective film is provided on the first main surface 2a or the third main surface 2c so as to cover the functional electrodes may also be adopted.
  • the resonant frequency of the surface acoustic wave resonator having a larger inverse number of the product of the electrode finger pitch, duty ratio, and electrode finger thickness will be higher than the resonant frequency of the other surface acoustic wave resonator.
  • the anti-resonant frequency of the surface acoustic wave resonator having a larger inverse number of the product of the electrode finger pitch, duty ratio, and electrode finger thickness will be higher than the anti-resonant frequency of the other surface acoustic wave resonator.
  • the second piezoelectric substrate 2B has a side surface 2e.
  • the side surface 2e is connected to the third principal surface 2c and the fourth principal surface 2d.
  • the side surface 2e is made up of the side surfaces of each layer.
  • a part of the external connection terminal 11 may be provided on this side surface 2e.
  • the external connection terminal 11 is not limited to a configuration having a through electrode 7 and an electrode pad 6.
  • the external connection terminal 21 has an external electrode 25 and an electrode pad 6.
  • the external electrode 25 is continuously provided on the third main surface 2c, the side surface 2e, and the fourth main surface 2d of the second piezoelectric substrate 2B.
  • the external electrode 25 electrically connects the support 8A and the electrode pad 6.
  • the external electrode 25 and the electrode pad 6 are provided as a single unit.
  • the external electrode 25 and the electrode pad 6 may be provided separately and connected to each other.
  • deterioration of the steepness of the filter characteristics can be suppressed and power resistance can be improved.
  • both the external connection terminal 21 including the external electrode 25 and the external connection terminal 11 including the through electrode 7 shown in FIG. 6 may be provided.
  • the multiple second acoustic wave resonators 13B include a series arm resonator with the lowest anti-resonance frequency among all the series arm resonators configured on the first piezoelectric substrate 2A and the second piezoelectric substrate 2B.
  • the configuration of the filter device according to the present invention is not limited to this.
  • the second embodiment according to the present invention will be described with reference to FIG. 6, which was used to explain the configuration of the first embodiment.
  • the filter device of the second embodiment has the same first piezoelectric substrate 2A, second piezoelectric substrate 2B, support 8A, pillar member 8B, and external connection terminal 11 as in the first embodiment.
  • the circuit configuration in the filter device of the second embodiment is the same as the circuit configuration in the first embodiment.
  • the second embodiment differs from the first embodiment in that the multiple second acoustic wave resonators 13B include a parallel arm resonator with the highest resonant frequency among all the parallel arm resonators configured in the first piezoelectric substrate 2A and the second piezoelectric substrate 2B.
  • the anti-resonance frequency of the parallel arm resonators constituting the pass band is located within the pass band.
  • the resonant frequency of the parallel arm resonator is located on the lower side of the pass band. The higher the resonant frequency of the parallel arm resonator, the closer the resonant frequency is to the pass band of the ladder-type filter. Therefore, the parallel arm resonator with the highest resonant frequency among the parallel arm resonators of the ladder-type filter has a particularly large effect on the steepness near the lower end of the pass band. Therefore, if the resonant frequency of the parallel arm resonator changes significantly, the steepness may deteriorate.
  • the parallel arm resonator with the highest resonant frequency is particularly prone to heat generation among the parallel arm resonators of the ladder filter. This is because the resonant frequency of this parallel arm resonator is the closest to the passband among the parallel arm resonators of the ladder filter. When the temperature of the elastic wave resonator changes significantly, the resonant frequency also changes significantly. This may cause further deterioration in the steepness near the low-frequency end of the passband of the ladder filter. Furthermore, the IDT electrode of this parallel arm resonator may become too hot, which may cause the IDT electrode to be damaged.
  • the parallel arm resonator with the highest resonant frequency among the parallel arm resonators of the filter device is the second acoustic wave resonator 13B configured on the second piezoelectric substrate 2B.
  • the electromechanical coupling coefficient Ksaw of the second piezoelectric substrate 2B is smaller than the electromechanical coupling coefficient Ksaw of the first piezoelectric substrate 2A. Therefore, the thermal resistance of the second piezoelectric substrate 2B is smaller than the thermal resistance of the first piezoelectric substrate 2A. This makes it possible to improve the heat dissipation in the portion of the filter device of the second embodiment where the parallel arm resonator with the highest resonant frequency is configured. This makes it possible to suppress deterioration of steepness near the end on the low-frequency side of the passband. In addition, it is possible to suppress damage to the IDT electrode of the parallel arm resonator. In this way, it is possible to improve the power resistance.
  • the inverse of the product of the electrode finger pitch of the IDT electrode and the duty ratio of any one of the second elastic wave resonators 13B is the largest.
  • the inverse of the product of the electrode finger pitch of the IDT electrode, the duty ratio, and the electrode finger thickness of any one of the second elastic wave resonators 13B is the largest among all the parallel arm resonators in the filter device. This makes it possible to more reliably make the resonant frequency of the parallel arm resonator that is the second elastic wave resonator 13B the highest among all the parallel arm resonators in the filter device.
  • At least one second elastic wave resonator configured on the second piezoelectric substrate may include at least one of a series arm resonator having the lowest anti-resonance frequency in the filter device and a parallel arm resonator having the highest resonant frequency in the filter device.
  • the multiple second elastic wave resonators include both a series arm resonator having the lowest anti-resonant frequency in the filter device and a parallel arm resonator having the highest resonant frequency in the filter device. This can effectively improve the power durability.
  • the filter device is a single filter as in the first and second embodiments, deterioration of steepness near the ends on the high and low sides of the pass band can be suppressed.
  • the filter device may include multiple filters.
  • deterioration of steepness can be suppressed in the filter including the series arm resonator having the lowest resonant frequency in the filter device and the filter including the parallel arm resonator having the highest resonant frequency in the filter device.
  • the filter device is a ladder-type filter, but is not limited to this.
  • the filter device may have, for example, a vertically coupled resonator type elastic wave filter, a series arm resonator, and a parallel arm resonator.
  • the series arm resonator and the parallel arm resonator may be connected to the vertically coupled resonator type elastic wave filter.
  • the filter device may have a vertically coupled resonator type elastic wave filter and a ladder-type circuit unit.
  • the ladder-type circuit unit includes at least one series arm resonator and at least one parallel arm resonator.
  • the ladder-type circuit unit may be connected to the vertically coupled resonator type elastic wave filter.
  • the at least one second elastic wave resonator may include at least one of a series arm resonator having the lowest anti-resonance frequency in the filter device and a parallel arm resonator having the highest resonant frequency in the filter device.
  • the filter device is a single filter.
  • the filter device according to the present invention may include multiple filters.
  • An example in which the filter device is a duplexer is shown in the third and fourth embodiments.
  • FIG. 11 is a schematic cross-sectional front view of a filter device according to a third embodiment.
  • the filter device 30 has a first piezoelectric substrate 2A, a second piezoelectric substrate 2B, a support 8A, a pillar member 8B, and an external connection terminal 11, similar to those of the first embodiment.
  • the filter device 30 differs from the first embodiment in that it is a duplexer.
  • the filter device 30 has a first filter 31A and a second filter 31B.
  • the first filter 31A is a transmission filter.
  • the second filter 31B is a reception filter.
  • the pass band of the first filter 31A is 1850 MHz to 1915 MHz, which is the transmission band of Band 25.
  • the pass band of the second filter 31B is 1930 MHz to 1995 MHz, which is the reception band of Band 25.
  • the pass bands of the first filter 31A and the second filter 31B are not limited to the above.
  • both the first filter 31A and the second filter 31B may be transmit filters or receive filters.
  • the first filter 31A and the second filter 31B are each a ladder type filter. Therefore, the first filter 31A and the second filter 31B each have at least one series arm resonator and at least one parallel arm resonator. As shown in FIG. 11, in this embodiment, the first filter 31A and the second filter 31B each have both the first elastic wave resonator 13A and the second elastic wave resonator 13B.
  • the electromechanical coupling coefficient Ksaw of the second piezoelectric substrate 2B is smaller than the electromechanical coupling coefficient Ksaw of the first piezoelectric substrate 2A. Therefore, the thermal resistance of the second piezoelectric substrate 2B is smaller than the thermal resistance of the first piezoelectric substrate 2A.
  • the second elastic wave resonators 13B configured on the second piezoelectric substrate 2B include the series arm resonator with the lowest anti-resonance frequency among all the series arm resonators configured on the first piezoelectric substrate 2A and the second piezoelectric substrate 2B. In this embodiment, the series arm resonator with the lowest anti-resonance frequency is included in the second filter 31B.
  • the filter device 30 has the above configuration, so that the temperature change of the series arm resonator in the second filter 31B can be reduced. Therefore, the frequency fluctuation of the series arm resonator can be reduced. Therefore, the deterioration of steepness can be suppressed near the end of the high-frequency side of the pass band of the second filter 31B in the filter device 30. In addition, the power resistance of the second filter 31B can be improved.
  • the multiple second acoustic wave resonators 13B configured on the second piezoelectric substrate 2B may include a parallel arm resonator having the highest resonant frequency among all the parallel arm resonators configured on the first piezoelectric substrate 2A and the second piezoelectric substrate 2B.
  • the parallel arm resonator may be included in the second filter 31B. In this case, deterioration of steepness near the low-frequency end of the pass band of the second filter 31B can be suppressed. In addition, the power durability of the second filter 31B can be improved.
  • the first filter 31A may have a series arm resonator with the lowest anti-resonance frequency in the filter device 30, and the series arm resonator may be the second elastic wave resonator 13B.
  • the first filter 31A may have a parallel arm resonator with the highest resonant frequency in the filter device 30, and the parallel arm resonator may be the second elastic wave resonator 13B. In these cases, it is possible to suppress deterioration of the steepness in the pass band of the first filter 31A in the filter device 30, and to improve the power durability.
  • FIG. 12 is a schematic cross-sectional front view of a filter device according to a fourth embodiment.
  • the filter device 40 of this embodiment has a first piezoelectric substrate 2A, a second piezoelectric substrate 2B, a support 8A, a pillar member 8B, and an external connection terminal 11, similar to those of the third embodiment.
  • the first filter 41A and the second filter 41B are ladder-type filters, similar to those of the third embodiment.
  • the first filter 41A includes only the first elastic wave resonator 13A of the first elastic wave resonator 13A and the second elastic wave resonator 13B. Therefore, all the series arm resonators and all the parallel arm resonators of the first filter 41A are the first elastic wave resonators 13A configured on the first piezoelectric substrate 2A.
  • the second filter 41B includes only the second elastic wave resonator 13B of the first elastic wave resonator 13A and the second elastic wave resonator 13B. Therefore, all the series arm resonators and all the parallel arm resonators of the second filter 41B are the second elastic wave resonators 13B configured on the second piezoelectric substrate 2B.
  • the multiple second acoustic wave resonators 13B configured on the second piezoelectric substrate 2B include the series arm resonator with the lowest anti-resonance frequency among all the series arm resonators configured on the first piezoelectric substrate 2A and the second piezoelectric substrate 2B.
  • the series arm resonator with the lowest anti-resonance frequency is included in the second filter 41B. This makes it possible to suppress deterioration of the steepness of the second filter 41B in the filter device 40 near the high-frequency end of the pass band. In addition, the power resistance of the second filter 41B can be improved.
  • the multiple second acoustic wave resonators 13B configured on the second piezoelectric substrate 2B may include a parallel arm resonator having the highest resonant frequency among all the parallel arm resonators configured on the first piezoelectric substrate 2A and the second piezoelectric substrate 2B.
  • deterioration of the steepness near the end on the low-frequency side of the pass band of the second filter 41B can be suppressed.
  • the power durability of the second filter 41B can be improved.
  • FIG. 13 is a schematic cross-sectional front view of a filter device according to the fifth embodiment.
  • This embodiment differs from the first embodiment in that the thickness of the second piezoelectric layer 55B is greater than the thickness of the first piezoelectric layer 55A. It also differs from the first embodiment in that rotated Y-cut lithium tantalate is used as the material for the first piezoelectric layer 55A and the second piezoelectric layer 55B. However, lithium niobate may also be used as the material for the first piezoelectric layer 55A and the second piezoelectric layer 55B. This embodiment also differs from the first embodiment in that all the second acoustic wave resonators 13B are series arm resonators. Other than the above, the filter device 50 of this embodiment has the same configuration as the filter device 10 of the first embodiment.
  • the electromechanical coupling coefficient Ksaw of the second piezoelectric substrate 52B is smaller than the electromechanical coupling coefficient Ksaw of the first piezoelectric substrate 52A. Therefore, the thermal resistance of the second piezoelectric substrate 52B is smaller than the thermal resistance of the first piezoelectric substrate 52A.
  • the second acoustic wave resonators 13B configured in the second piezoelectric substrate 52B include the series arm resonator with the lowest anti-resonance frequency among all the series arm resonators configured in the first piezoelectric substrate 52A and the second piezoelectric substrate 52B. This makes it possible to suppress deterioration of the steepness of the filter characteristics and to improve power durability, similar to the first embodiment.
  • the thickness of the second piezoelectric layer 55B is greater than the thickness of the first piezoelectric layer 55A. This effectively prevents deterioration of the steepness of the filter characteristics. The details of this are described below.
  • the thicker the piezoelectric layer, such as the lithium tantalate layer the smaller the value of the relative bandwidth.
  • the second piezoelectric layer 55B in the second piezoelectric substrate 52B is thick. Therefore, the value of the relative bandwidth of the second acoustic wave resonator 13B formed in the second piezoelectric substrate 52B is small.
  • the electromechanical coupling coefficient Ksaw of the piezoelectric substrate correlates with the relative bandwidth. Specifically, the smaller the value of the relative bandwidth, the smaller the electromechanical coupling coefficient Ksaw. Therefore, in this embodiment, the electromechanical coupling coefficient Ksaw of the second piezoelectric substrate 52B can be effectively reduced.
  • FIG. 14 is a schematic diagram of the impedance frequency characteristics of a first elastic wave resonator and a second elastic wave resonator in the fifth embodiment.
  • FIG. 15 is a schematic diagram of the attenuation frequency characteristics of a filter device in the fifth embodiment.
  • the band ratio value of the second elastic wave resonator 13B which is a series arm resonator, is small. This makes it possible to increase the steepness near the high-frequency end of the passband in the filter device 50, as shown in FIG. 15.
  • the thermal resistance of the second piezoelectric substrate 52B is small. Therefore, it is possible to increase the steepness and improve the power resistance.
  • the external connection terminal 11 is provided on the second piezoelectric substrate 52B. This allows heat to be transferred from the second acoustic wave resonator 13B to the outside more efficiently. This effectively increases the power resistance.
  • the filter device 50 of this embodiment is a ladder-type filter including all of the first elastic wave resonators 13A and all of the second elastic wave resonators 13B. All of the second elastic wave resonators 13B are series arm resonators. Note that it is sufficient that at least one ladder-type filter is configured in the filter device 50.
  • the filter device 50 may have multiple ladder-type filters, such as the third embodiment shown in FIG. 11.
  • At least one ladder-type filter may include at least one first acoustic wave resonator 13A and at least one second acoustic wave resonator 13B.
  • At least one second acoustic wave resonator 13B of the ladder-type filter may include a series arm resonator having the lowest anti-resonance frequency among all the series arm resonators configured on the first piezoelectric substrate 52A and the second piezoelectric substrate 52B.
  • the filter device of the sixth embodiment has a first piezoelectric substrate 52A, a second piezoelectric substrate 52B, a support 8A, a pillar member 8B, and an external connection terminal 11 similar to those of the fifth embodiment.
  • the circuit configuration of the filter device of the sixth embodiment is similar to that of the fifth and first embodiments.
  • the sixth embodiment differs from the fifth embodiment in that the multiple second acoustic wave resonators 13B are all parallel arm resonators.
  • the thickness of the second piezoelectric layer 55B in the second piezoelectric substrate 52B is greater than the thickness of the first piezoelectric layer 55A in the first piezoelectric substrate 52A. Therefore, the value of the fractional bandwidth of the second acoustic wave resonator 13B formed in the second piezoelectric substrate 52B is small. This makes it possible to effectively reduce the electromechanical coupling coefficient Ksaw of the second piezoelectric substrate 52B.
  • the filter device of the sixth embodiment the heat dissipation can be improved in the portion in which the parallel arm resonator with the highest resonant frequency is configured. This effectively prevents deterioration of steepness near the low-frequency end of the passband. In addition, damage to the IDT electrode of the parallel arm resonator can be prevented. In this way, the power resistance can be improved.
  • FIG. 16 is a schematic diagram of the impedance frequency characteristics of a first elastic wave resonator and a second elastic wave resonator in the sixth embodiment.
  • FIG. 17 is a schematic diagram of the attenuation frequency characteristics of a filter device in the sixth embodiment.
  • the band ratio value of the second elastic wave resonator 13B which is a parallel arm resonator, is small. This makes it possible to increase the steepness near the lower end of the passband in the filter device, as shown in FIG. 17.
  • the thermal resistance of the second piezoelectric substrate 52B is small. Therefore, it is possible to increase the steepness and the power resistance.
  • the external connection terminal 11 is provided on the second piezoelectric substrate 52B. This allows heat to be transferred from the second acoustic wave resonator 13B to the outside more efficiently. This effectively increases the power resistance.
  • the filter device of the sixth embodiment is a ladder-type filter including all the first elastic wave resonators 13A and all the second elastic wave resonators 13B. All the second elastic wave resonators 13B are parallel arm resonators. As described above, even in a configuration in which the second piezoelectric layer 55B is thicker than the first piezoelectric layer 55A, for example, at least one ladder-type filter may be configured. At least one ladder-type filter may include at least one first elastic wave resonator 13A and at least one second elastic wave resonator 13B.
  • At least one second elastic wave resonator 13B of the ladder-type filter may include a parallel arm resonator having the highest resonant frequency among all the parallel arm resonators configured on the first piezoelectric substrate 52A and the second piezoelectric substrate 52B.
  • FIG. 18 is a schematic cross-sectional front view of a filter device according to the seventh embodiment.
  • both the first piezoelectric layer 55A and the second piezoelectric layer 55B are rotated Y-cut LiTaO3 layers.
  • This embodiment differs from the fifth embodiment in that the cut angle of the first piezoelectric layer 55A is different from the cut angle of the second piezoelectric layer 55B.
  • the filter device of this embodiment has the same configuration as the filter device 50 of the fifth embodiment.
  • the cut angle of the first piezoelectric layer and the cut angle of the second piezoelectric layer being different means that the difference between these cut angles is 0.5° or more.
  • the cut angle of the first piezoelectric layer 55A is 55°Y.
  • the cut angle of the second piezoelectric layer 55B is 35°Y. Note that the cut angles of the first piezoelectric layer 55A and the second piezoelectric layer 55B are not limited to the above.
  • the cut angle of a piezoelectric layer such as a lithium tantalate layer changes
  • the value of the relative bandwidth also changes.
  • the cut angle of the first piezoelectric layer 55A and the cut angle of the second piezoelectric layer 55B are different from each other. Therefore, the value of the relative bandwidth of the first elastic wave resonator 13A and the value of the relative bandwidth of the second elastic wave resonator 13B are different from each other.
  • the cut angle of the first piezoelectric layer 55A and the cut angle of the second piezoelectric layer 55B are different from each other so that the value of the fractional bandwidth of the second elastic wave resonator 13B is smaller than the value of the fractional bandwidth of the first elastic wave resonator 13A.
  • the multiple second elastic wave resonators 13B include a series arm resonator having the lowest anti-resonance frequency among all the series arm resonators configured on the first piezoelectric substrate 52A and the second piezoelectric substrate 52B. In this case, as in the fifth embodiment, it is possible to increase the steepness near the high-frequency end of the pass band in the filter device.
  • the second acoustic wave resonators 13B may include a parallel arm resonator having the highest resonant frequency among all the parallel arm resonators configured on the first piezoelectric substrate 52A and the second piezoelectric substrate 52B. In this case, as in the sixth embodiment, it is possible to increase the steepness near the low-frequency end of the passband in the filter device.
  • the configuration of the eighth embodiment will be described below.
  • the configuration of the eighth embodiment is similar to that of the fifth embodiment, except for the material of the piezoelectric layer. Therefore, the drawings and symbols used in the description of the fifth embodiment will be used in the description of the eighth embodiment.
  • the eighth embodiment shown with reference to FIG. 13 differs from the fifth embodiment in that the material used for the first piezoelectric layer 55A is different from the material used for the second piezoelectric layer 55B.
  • the filter device of the eighth embodiment has the same configuration as the filter device 50 of the fifth embodiment.
  • the first piezoelectric layer 55A and the second piezoelectric layer 55B may be made of, for example, lithium tantalate, lithium niobate, zinc oxide, aluminum nitride, or scandium aluminum nitride.
  • the band ratios of the first elastic wave resonator 13A and the second elastic wave resonator 13B can be suitably adjusted. This makes it possible to increase the steepness near the high-frequency end of the passband in the filter device.
  • the plurality of second acoustic wave resonators 13B may include a parallel arm resonator having the highest resonant frequency among all the parallel arm resonators configured on the first piezoelectric substrate 52A and the second piezoelectric substrate 52B.
  • This configuration is a modified example of the eighth embodiment. In this modified example, as in the sixth embodiment, it is possible to increase the steepness near the low-frequency end of the passband in the filter device.
  • FIG. 19 is a schematic front cross-sectional view of a filter device according to the ninth embodiment.
  • This embodiment differs from the fifth embodiment in that the thickness of the first intermediate layer 54A and the thickness of the second intermediate layer 54B are different from each other.
  • the filter device of this embodiment has a similar configuration to the filter device 50 of the fifth embodiment. Note that in this embodiment, like the fifth embodiment, silicon oxide is used as the material for the first intermediate layer 54A and the second intermediate layer 54B. However, the materials for the first intermediate layer 54A and the second intermediate layer 54B are not limited to the above.
  • the thickness of the first intermediate layer and the thickness of the second intermediate layer are different from each other means that the difference between these thicknesses is 5% or more for both the thickness of the first intermediate layer and the thickness of the second intermediate layer.
  • the thickness of the first intermediate layer 54A is 300 nm.
  • the thickness of the second intermediate layer 54B is 600 nm.
  • the thicknesses of the first intermediate layer 54A and the second intermediate layer 54B are not limited to the above.
  • Figure 20 shows the relationship between the standard value of the thickness of the intermediate layer and the relative bandwidth.
  • the second intermediate layer 54B is thicker than the first intermediate layer 54A. This makes it possible to more reliably make the band ratio of the second elastic wave resonator 13B smaller than the band ratio of the first elastic wave resonator 13A.
  • the second elastic wave resonators 13B include a series arm resonator having the lowest anti-resonance frequency among all the series arm resonators configured on the first piezoelectric substrate and the second piezoelectric substrate. This makes it possible to increase the steepness near the high-frequency end of the passband in the filter device, as in the fifth embodiment.
  • the plurality of second acoustic wave resonators 13B may include a parallel arm resonator having the highest resonant frequency among all the parallel arm resonators configured on the first piezoelectric substrate and the second piezoelectric substrate.
  • This configuration is a modified example of the ninth embodiment. In this modified example, as in the sixth embodiment, it is possible to increase the steepness near the low-frequency end of the passband in the filter device.
  • the thickness of the first intermediate layer 54A or the second intermediate layer 54B is preferably 350 nm or more and 500 nm or less, and more preferably 400 nm or more and 450 nm or less. This makes it possible to suppress harmonics as unwanted waves. Note that these harmonics are harmonics that occur at approximately 1.5 times the main mode. Details of this effect are given below.
  • FIG. 21 shows the relationship between the thickness of the piezoelectric layer and the thickness of the intermediate layer and the phase of the harmonics. Note that in FIG. 21, the thickness of the piezoelectric layer is shown as a standard value.
  • the phase of the harmonics is suppressed to less than 0° regardless of the thickness of the piezoelectric layer.
  • the thickness of the intermediate layer is 400 nm or more and 450 nm or less, the phase of the harmonics is suppressed even further.
  • the material of the first intermediate layer 54A and the material of the second intermediate layer 54B may be different from each other. In this case, it is possible to adjust the type of harmonics that are likely to be generated. Therefore, it is possible to adjust the frequency of the main mode of each elastic wave resonator as well as the frequency at which harmonics are generated. Therefore, when the filter device is a multiplexer, it is possible to adjust the frequency at which harmonics are generated so that it is not located within the passband of any of the bandpass filters. In addition, as in this embodiment, it is possible to increase the steepness near the lower end of the passband of the bandpass filter.
  • the configuration in which the material of the first intermediate layer 54A and the material of the second intermediate layer 54B are different from each other can be adopted in the ninth embodiment and configurations of the present invention other than the ninth embodiment.
  • the thickness of the first intermediate layer 54A and the thickness of the second intermediate layer 54B may be the same.
  • the multiple second acoustic wave resonators 13B may include a parallel arm resonator having the highest resonant frequency among all the parallel arm resonators configured on the first piezoelectric substrate and the second piezoelectric substrate.
  • FIG. 22 is a schematic cross-sectional front view of a filter device according to the tenth embodiment.
  • This embodiment differs from the fifth embodiment in that the thickness of the first support substrate 53A and the thickness of the second support substrate 53B are different from each other. Specifically, the thickness of the second support substrate 53B is thicker than the thickness of the first support substrate 53A.
  • the filter device of this embodiment has the same configuration as the filter device 50 of the fifth embodiment.
  • the thickness of the first support substrate and the thickness of the second support substrate are different from each other means that the difference between these thicknesses is 50 nm or more.
  • FIG. 24 is a schematic cross-sectional front view of a filter device according to an eleventh embodiment.
  • This embodiment differs from the fifth embodiment in that the thickness of the first support substrate 53A is greater than the thickness of the second support substrate 53B.
  • the filter device of this embodiment has the same configuration as the filter device 50 of the fifth embodiment.
  • first support substrate 53A when a stack including a first piezoelectric substrate and a second piezoelectric substrate is mounted on a mounting substrate, cracks are unlikely to occur in the first support substrate 53A.
  • first support substrate 53A when mounting the stack on a mounting substrate 61, the first support substrate 53A is attracted by an adsorption collet 100 and the stack is transported. The stack is then mounted on the mounting substrate 61. During mounting, a particularly large impact is applied to the first support substrate 53A. In contrast, in this embodiment, the first support substrate 53A is thick, and therefore the first support substrate 53A is unlikely to break. This can increase the reliability of the filter device.
  • the multiple second acoustic wave resonators 13B may include a parallel arm resonator having the highest resonant frequency among all the parallel arm resonators configured on the first piezoelectric substrate and the second piezoelectric substrate.
  • FIG. 26 is a schematic cross-sectional front view of a filter device according to the twelfth embodiment.
  • This embodiment differs from the fifth embodiment in that the Euler angles ( ⁇ , ⁇ , ⁇ ) of the crystal orientations of the first support substrate 53A and the second support substrate 53B are different from each other.
  • the filter device of this embodiment has a similar configuration to the filter device 50 of the fifth embodiment.
  • silicon is used as the material of the first support substrate 53A and the second support substrate 53B.
  • the material of the first support substrate 53A and the second support substrate 53B is not limited to the above.
  • Figure 27 shows the relationship between ⁇ in the Euler angles ( ⁇ , ⁇ , ⁇ ) of the support substrate and the phase of the Rayleigh wave and harmonics.
  • Figure 28 shows the case where the phase is -60° or less in the relationship shown in Figure 27.
  • ⁇ is shown as a standard value. Note that harmonics that occur at frequencies higher than 2.2 times the main mode will be referred to as higher-order harmonics below. In Figures 27 and 28, higher-order harmonics will simply be referred to as higher-order.
  • phase of the harmonics occurring at frequencies around 2.2 times the frequency at which the main mode occurs is particularly dependent on ⁇ in the Euler angles ( ⁇ , ⁇ , ⁇ ) of the support substrate.
  • the phases of the harmonics occurring at frequencies around 1.5 times the frequency of the main mode, higher harmonics, and Rayleigh waves also depend on ⁇ in the Euler angles ( ⁇ , ⁇ , ⁇ ) of the support substrate.
  • the multiple second acoustic wave resonators 13B may include a parallel arm resonator having the highest resonant frequency among all the parallel arm resonators configured on the first piezoelectric substrate and the second piezoelectric substrate.
  • the configuration of the thirteenth embodiment will be described below.
  • the configuration of the thirteenth embodiment is similar to that of the fifth embodiment, except for the material of the support substrate. Therefore, the drawings and symbols used in the description of the fifth embodiment will be used in the description of the thirteenth embodiment.
  • the thirteenth embodiment differs from the fifth embodiment in that the material used for the first support substrate 3A is different from the material used for the second support substrate 3B.
  • the filter device of the thirteenth embodiment has the same configuration as the filter device 50 of the fifth embodiment.
  • the temperature coefficient of frequency (TCF) can be adjusted in each of the first support substrate 3A and the second support substrate 3B. This allows adjustment of the TCF of the first elastic wave resonator 13A configured in the first piezoelectric substrate 52A, and the TCF of the second elastic wave resonator 13B configured in the second piezoelectric substrate 52B.
  • the frequency temperature coefficient at the resonant frequency is designated as TCFr.
  • the frequency temperature coefficient at the anti-resonant frequency is designated as TCFa.
  • the TCFr or TCFa can be brought close to 0 ppm/°C. This can provide effects such as increasing the steepness of the filter device and suppressing the deterioration of the voltage standing wave ratio (VSWR).
  • VSWR voltage standing wave ratio
  • the heat dissipation properties of the material used for the second support substrate 3B are preferably higher than those of the material used for the first support substrate 3A. This allows the heat generated in the series arm resonator with the lowest anti-resonance frequency among all the series arm resonators configured in the first piezoelectric substrate 52A and the second piezoelectric substrate 52B to be transferred to the outside more efficiently. This makes it possible to further suppress the deterioration of the steepness on the high-frequency side of the passband in the filter device, and to further increase the power resistance.
  • the material for the second support substrate 3B may be, for example, a material for adjusting TCFr or TCFa, a material that can suppress harmonics, or a material with high heat dissipation properties.
  • the material for the first support substrate 3A may be, for example, a material for adjusting TCFr or TCFa, or a material that can suppress harmonics.
  • the multiple second acoustic wave resonators 13B may include a parallel arm resonator having the highest resonant frequency among all the parallel arm resonators configured on the first piezoelectric substrate 52A and the second piezoelectric substrate 52B.
  • FIG. 29 is a schematic cross-sectional front view of a filter device according to the fourteenth embodiment.
  • This embodiment differs from the fifth embodiment in that the thickness of the IDT electrode 65A of the first elastic wave resonator 13A is different from the thickness of the IDT electrode 65B of the second elastic wave resonator 13B. Specifically, the thickness of the IDT electrode 65B of the second elastic wave resonator 13B is thinner than the thickness of the IDT electrode 65A of the first elastic wave resonator 13A.
  • the filter device of this embodiment has a similar configuration to the filter device 50 of the fifth embodiment.
  • Al is used as the material for the IDT electrodes 65A and 65B.
  • the material for the IDT electrodes 65A and 65B is not limited to the above.
  • the wavelength defined by the electrode finger pitch of the IDT electrodes is ⁇ .
  • the thickness of the IDT electrode 65A of the first acoustic wave resonator 13A is 0.1 ⁇ .
  • the thickness of the IDT electrode 65B of the second acoustic wave resonator 13B is 0.05 ⁇ .
  • the wavelength ⁇ that is the reference for the thicknesses of the IDT electrodes 65A and 65B is the shortest wavelength ⁇ among the wavelengths ⁇ of all the IDT electrodes 65A and all the IDT electrodes 65B.
  • the thicknesses of the IDT electrodes 65A and 65B are not limited to the above.
  • the steepness of the filter characteristics is less likely to deteriorate even when the temperature rises. Details of this effect are provided below.
  • Figure 30 shows the relationship between the thickness of the IDT electrode and TCFa. Note that in Figure 30, the thickness of the IDT electrode is shown as a standard value. Figure 30 shows an example in which Al is used as the material for the IDT electrode.
  • the thicker the IDT electrode the larger the TCFa in the negative direction.
  • all the second elastic wave resonators 13B are series arm resonators.
  • the thickness of the IDT electrode 65B is thin in the second elastic wave resonators 13B. Therefore, in the second elastic wave resonators 13B, which are series arm resonators, the TCFa can be brought close to 0 ppm/°C. As a result, even when the temperature of the second elastic wave resonator 13B increases, the anti-resonance frequency of the second elastic wave resonator 13B is less likely to change. As a result, the steepness of the high-frequency side of the pass band in the filter device is less likely to deteriorate.
  • Figure 31 shows the relationship between the thickness of the IDT electrode and TCFr. Note that in Figure 31, the thickness of the IDT electrode is shown as a standard value. Figure 31 shows an example in which Al is used as the material for the IDT electrode.
  • the multiple first elastic wave resonators 13A include parallel arm resonators.
  • the IDT electrodes 65A are thick. Therefore, in the first elastic wave resonators 13A, which are parallel arm resonators, the TCFr can be brought closer to 0 ppm/°C. As a result, even if the temperature of the first elastic wave resonators 13A increases, the resonant frequency of the first elastic wave resonators 13A, which are parallel arm resonators, is less likely to change. As a result, the steepness of the low-frequency side of the passband in the filter device is less likely to deteriorate.
  • the multiple second acoustic wave resonators 13B may include a parallel arm resonator having the highest resonant frequency among all the parallel arm resonators configured on the first piezoelectric substrate and the second piezoelectric substrate.
  • This configuration is a modified example of the fourteenth embodiment.
  • it is preferable that the thickness of the IDT electrode 65B of the second acoustic wave resonator 13B is greater than the thickness of the IDT electrode 65A of the first acoustic wave resonator 13A. This makes it difficult for the steepness of the low-frequency side of the pass band in the filter device to deteriorate.
  • the thickness of the IDT electrode 65A of the first elastic wave resonator 13A and the IDT electrode 65B of the second elastic wave resonator 13B is 0.03 ⁇ or more and 0.3 ⁇ or less.
  • the thickness of the IDT electrode 65A and the IDT electrode 65B is 0.03 ⁇ or more, the insertion loss of the filter device is unlikely to increase.
  • the thickness of the IDT electrode 65A and the IDT electrode 65B is 0.3 ⁇ or less, deterioration of power resistance can be suppressed.
  • FIG. 32 is a schematic cross-sectional front view of a filter device according to the fifteenth embodiment.
  • This embodiment differs from the fifth embodiment in that the material used for the IDT electrode 65A of the first acoustic wave resonator 13A is different from the material used for the IDT electrode 65B of the second acoustic wave resonator 13B.
  • the filter device of the fifteenth embodiment has the same configuration as the filter device 50 of the fifth embodiment.
  • all the second elastic wave resonators 13B are series arm resonators.
  • the multiple first elastic wave resonators 13A include parallel arm resonators.
  • the electrical resistance of the material used for the IDT electrode 65A of the first elastic wave resonator 13A is higher than the electrical resistance of the material used for the IDT electrode 65B of the second elastic wave resonator 13B. Even if the electrical resistance of the parallel arm resonators is high, degradation of the filter characteristics of the filter device is unlikely to occur.
  • the power resistance of the first elastic wave resonator 13A which is a parallel arm resonator, can be increased.
  • the strength of the material used for the IDT electrode 65A of the first acoustic wave resonator 13A is greater than the strength of the material used for the IDT electrode 65B of the second acoustic wave resonator 13B. This can increase the power resistance of the first acoustic wave resonator 13A, which is a parallel arm resonator.
  • the plurality of second elastic wave resonators 13B may include a parallel arm resonator having the highest resonant frequency among all the parallel arm resonators configured on the first piezoelectric substrate and the second piezoelectric substrate.
  • This configuration is a modified example of the fifteenth embodiment. In this modified example, it is preferable that the electrical resistance of the material used for the IDT electrode 65B of the second elastic wave resonator 13B is higher than the electrical resistance of the material used for the IDT electrode 65A of the first elastic wave resonator 13A.
  • the strength of the material used for the IDT electrode 65B of the second elastic wave resonator 13B is higher than the strength of the material used for the IDT electrode 65A of the first elastic wave resonator 13A. This can increase the power resistance of the second elastic wave resonator 13B, which is a parallel arm resonator.
  • the IDT electrode 65A of the first elastic wave resonator 13A and the IDT electrode 65B of the second elastic wave resonator 13B may be made of, for example, Al, Cu, Pt, Ti, Mo, W, Ru, Au, Ag, or an alloy containing the above metals as a main component.
  • FIG. 33 is a schematic perspective plan view showing the arrangement of elastic wave resonators on a first main surface of a first piezoelectric substrate in the sixteenth embodiment.
  • FIG. 34 is a schematic plan view showing the arrangement of elastic wave resonators on a third main surface of a second piezoelectric substrate in the sixteenth embodiment. Note that the double-headed arrow F in FIGS. 33 and 34 indicates the direction of elastic wave propagation. Wiring, supports, pillar members, etc. are omitted in FIGS. 33 and 34.
  • the circular portions in FIGS. 33 and 34 diagrammatically show electrode pads.
  • the filter device of this embodiment has the same configuration as the filter device 50 of the fifth embodiment.
  • the Euler angles ( ⁇ , ⁇ , ⁇ ) of the first piezoelectric layer 55A and the second piezoelectric layer 55B are the same.
  • the relationship between the elastic wave propagation direction and the Euler angles ( ⁇ , ⁇ , ⁇ ) of the piezoelectric layer is different between the first elastic wave resonator 13A and the second elastic wave resonator 13B.
  • all the second elastic wave resonators 13B are series arm resonators. Therefore, by reducing the value of the band ratio of the second elastic wave resonator 13B, it is possible to increase the steepness near the high-frequency end of the passband of the filter device.
  • the multiple second acoustic wave resonators 13B may include a parallel arm resonator having the highest resonant frequency among all the parallel arm resonators configured on the first piezoelectric substrate 52A and the second piezoelectric substrate 52B.
  • This configuration is a modified example of the sixteenth embodiment. In this modified example, by reducing the value of the band ratio of the second acoustic wave resonator 13B, which is a parallel arm resonator, it is possible to increase the steepness near the low-frequency end of the passband of the filter device.
  • FIG. 35 is a schematic cross-sectional front view of a filter device according to the seventeenth embodiment.
  • This embodiment differs from the fifth embodiment in that a first dielectric film 66A is provided as a protective film on the first piezoelectric layer 55A so as to cover the multiple IDT electrodes 65A.
  • This embodiment also differs from the fifth embodiment in that a second dielectric film 66B is provided as a protective film on the second piezoelectric layer 55B so as to cover the multiple IDT electrodes 65B.
  • the filter device of this embodiment has the same configuration as the filter device 50 of the fifth embodiment.
  • the thickness of the second piezoelectric layer 55B in the second piezoelectric substrate 52B is greater than the thickness of the first piezoelectric layer 55A in the first piezoelectric substrate 52A. This makes it possible to more reliably make the electromechanical coupling coefficient Ksaw of the second piezoelectric substrate 52B smaller than the electromechanical coupling coefficient Ksaw of the first piezoelectric substrate 52A.
  • the second acoustic wave resonators 13B include a series arm resonator having the lowest anti-resonance frequency among all the series arm resonators configured in the first piezoelectric substrate 52A and the second piezoelectric substrate 52B. This makes it possible to suppress deterioration of the steepness near the high-frequency end of the filter device and to improve power durability.
  • the multiple IDT electrodes 65A are covered with a first dielectric film 66A.
  • the multiple IDT electrodes 65B are covered with a second dielectric film 66B. This protects each IDT electrode, making them less likely to be damaged.
  • the thickness of the first dielectric film 66A and the thickness of the second dielectric film 66B are different from each other. Specifically, the thickness of the first dielectric film 66A is thicker than the thickness of the second dielectric film 66B. More specifically, the thickness of the first dielectric film 66A is 0.025 ⁇ . The thickness of the second dielectric film 66B is 0.015 ⁇ .
  • the thickness of the first dielectric film 66A is the distance from the surface of the first dielectric film 66A that is in contact with the IDT electrode 65A to the surface of the first dielectric film 66A.
  • the thickness of the second dielectric film 66B is the distance from the surface of the second dielectric film 66B that is in contact with the IDT electrode 65B to the surface of the second dielectric film 66B.
  • the wavelength ⁇ that is the basis for the thicknesses of the first dielectric film 66A and the second dielectric film 66B is the shortest wavelength ⁇ among the wavelengths ⁇ of all the IDT electrodes 65A and all the IDT electrodes 65B.
  • the thicknesses of the first dielectric film 66A and the second dielectric film 66B are not limited to the above.
  • the thickness of one dielectric film is different from the thickness of the other dielectric film means that the difference between the two thicknesses is ⁇ 5% or less.
  • the difference between the two thicknesses being ⁇ 5% or less specifically means that the absolute value of the difference between the thickness of one dielectric film and the thickness of the other dielectric film is 5% or less for both of the thicknesses of the dielectric films.
  • Silicon oxide is used as the material for the first dielectric film 66A and the second dielectric film 66B.
  • the material for the first dielectric film 66A and the second dielectric film 66B is not limited to the above, and for example, dielectrics such as glass, silicon oxide, silicon oxynitride, lithium oxide, tantalum oxide, or compounds in which fluorine, carbon, or boron is added to silicon oxide, or materials containing the above materials as the main components can also be used.
  • the steepness of the passband of the filter device can be increased. This is described in detail below.
  • the first dielectric film 66A and the second dielectric film 66B may be collectively referred to simply as the dielectric film. However, it should be noted that the dielectric film referred to here is different from the dielectric film 28 provided on the fourth main surface 2d of the second piezoelectric substrate 52B.
  • Figure 36 shows the relationship between the thickness of the dielectric film and the relative bandwidth.
  • the thickness of the dielectric film is shown as a standard value.
  • the thicker the dielectric film the smaller the value of the bandwidth ratio.
  • the multiple first elastic wave resonators 13A include parallel arm resonators.
  • the first dielectric film 66A has a large thickness. Therefore, the bandwidth ratio can be reduced in the first elastic wave resonator 13A, which is a parallel arm resonator. This can increase the steepness near the low-frequency end of the passband of the filter device.
  • the thickness of the second dielectric film 66B may be thicker than the thickness of the first dielectric film 66A.
  • This configuration is a first modified example of the seventeenth embodiment.
  • all the second acoustic wave resonators 13B are series arm resonators. Therefore, the value of the band ratio can be reduced in the second acoustic wave resonators 13B that are series arm resonators. This can increase the steepness near the high-frequency end of the passband of the filter device.
  • the multiple second acoustic wave resonators 13B may include a parallel arm resonator having the highest resonant frequency among all the parallel arm resonators configured on the first piezoelectric substrate 52A and the second piezoelectric substrate 52B.
  • the thickness of the second dielectric film 66B may be greater than the thickness of the first dielectric film 66A.
  • This configuration is a second modified example of the seventeenth embodiment. In this modified example, the steepness can be increased near the low-frequency end of the passband of the filter device by reducing the value of the band ratio of the second acoustic wave resonator 13B, which is a parallel arm resonator.
  • FIG. 37 is a schematic cross-sectional front view of a filter device according to the 18th embodiment.
  • This embodiment differs from the 17th embodiment in that the first dielectric film 66A and the second dielectric film 66B have the same thickness. This embodiment also differs from the 17th embodiment in that the material used for the first dielectric film 66A and the material used for the second dielectric film 66B are different from each other. Other than the above, the filter device of this embodiment has the same configuration as the filter device of the 17th embodiment.
  • the thickness of the second piezoelectric layer 55B in the second piezoelectric substrate 52B is greater than the thickness of the first piezoelectric layer 55A in the first piezoelectric substrate 52A. This makes it possible to suppress deterioration of the steepness near the end of the high-frequency side of the filter device, and to increase the power resistance.
  • the material used for the first dielectric film 66A and the material used for the second dielectric film 66B can adjust, for example, the band ratio of the first elastic wave resonator 13A and the second elastic wave resonator 13B. This can increase the steepness of the passband of the filter device, as in the seventeenth embodiment.
  • the configuration of the 18th embodiment can also be adopted in configurations of the present invention other than the 18th embodiment.
  • the thickness of the first dielectric film 66A and the thickness of the second dielectric film 66B may be different from each other.
  • the multiple second acoustic wave resonators 13B may include a parallel arm resonator having the highest resonant frequency among all the parallel arm resonators configured on the first piezoelectric substrate 52A and the second piezoelectric substrate 52B.
  • a piezoelectric element comprising: a first piezoelectric substrate having a first main surface and a second main surface opposed to each other; at least one first elastic wave resonator which includes an IDT electrode provided on the first main surface of the first piezoelectric substrate and is a series arm resonator or a parallel arm resonator; a support provided on the first main surface of the first piezoelectric substrate and arranged to surround the first elastic wave resonator; a second piezoelectric substrate provided on the support and having a third main surface located on the first piezoelectric substrate side and a fourth main surface facing the third main surface; and at least one second elastic wave resonator which includes an IDT electrode provided on the third main surface of the second piezoelectric substrate and is a series arm resonator, wherein the first piezoelectric substrate has a first support substrate and a first piezoelectric layer laminated with the first support substrate, and the first main surface is a main surface of the first piezoelectric layer.
  • the second piezoelectric substrate has a second support substrate and a second piezoelectric layer laminated with the second support substrate, the third main surface includes the main surface of the second piezoelectric layer, the IDT electrode of the at least one first acoustic wave resonator and the IDT electrode of the at least one second acoustic wave resonator have a plurality of first electrode fingers and a plurality of second electrode fingers that are connected to different potentials and are interdigitated with each other, a space is formed surrounded by the first piezoelectric substrate, the second piezoelectric substrate, and the support, the electromechanical coupling coefficient Ksaw of the second piezoelectric substrate is smaller than the electromechanical coupling coefficient Ksaw of the first piezoelectric substrate, and the at least one second acoustic wave resonator includes a series arm resonator with the lowest anti-resonance frequency among all series arm resonators formed in the first piezoelectric substrate and the second piezoelectric substrate.
  • a piezoelectric element comprising: a first piezoelectric substrate having a first main surface and a second main surface opposed to each other; at least one first elastic wave resonator which includes an IDT electrode provided on the first main surface of the first piezoelectric substrate and is a series arm resonator or a parallel arm resonator; a support provided on the first main surface of the first piezoelectric substrate and arranged to surround the first elastic wave resonator; a second piezoelectric substrate provided on the support and having a third main surface located on the first piezoelectric substrate side and a fourth main surface facing the third main surface; and at least one second elastic wave resonator which includes an IDT electrode provided on the third main surface of the second piezoelectric substrate and is a parallel arm resonator, wherein the first piezoelectric substrate has a first support substrate and a first piezoelectric layer laminated with the first support substrate, and the first main surface is a main surface of the first piezoelectric layer.
  • the second piezoelectric substrate has a second support substrate and a second piezoelectric layer laminated with the second support substrate, the third main surface includes the main surface of the second piezoelectric layer, the IDT electrode of the at least one first acoustic wave resonator and the IDT electrode of the at least one second acoustic wave resonator have a plurality of first electrode fingers and a plurality of second electrode fingers that are connected to different potentials and are interdigitated with each other, a space is formed surrounded by the first piezoelectric substrate, the second piezoelectric substrate, and the support, the electromechanical coupling coefficient Ksaw of the second piezoelectric substrate is smaller than the electromechanical coupling coefficient Ksaw of the first piezoelectric substrate, and the at least one second acoustic wave resonator includes a parallel arm resonator having the highest resonant frequency among all parallel arm resonators formed in the first piezoelectric substrate and the second piezoelectric substrate.
  • a filter device comprising a first filter and a second filter, the first filter including some of the at least one first elastic wave resonator and the at least one second elastic wave resonator, and the second filter including the remaining of the at least one first elastic wave resonator and the at least one second elastic wave resonator, as described in ⁇ 1> or ⁇ 2>.
  • the filter device comprising a plurality of the first elastic wave resonators and a plurality of the second elastic wave resonators, the first filter including only the first elastic wave resonators among the plurality of first elastic wave resonators and the plurality of second elastic wave resonators, and the second filter including only the second elastic wave resonators among the plurality of first elastic wave resonators and the plurality of second elastic wave resonators.
  • the filter device comprising a plurality of the first elastic wave resonators and a plurality of the second elastic wave resonators, wherein the first filter and the second filter each include the first elastic wave resonator and the second elastic wave resonator.
  • the filter device according to ⁇ 1> or ⁇ 2>, which is a single filter including all of the first acoustic wave resonators and all of the second acoustic wave resonators.
  • ⁇ 7> A filter device according to any one of ⁇ 1> to ⁇ 6>, in which the external connection terminal includes a through electrode penetrating the second piezoelectric substrate, and an electrode pad provided on the fourth main surface of the second piezoelectric substrate and connected to the through electrode.
  • the filter device comprising a plurality of the second acoustic wave resonators, the external connection terminals including a through electrode penetrating the second piezoelectric substrate and an electrode pad provided on the fourth main surface of the second piezoelectric substrate and connected to the through electrode, the thickness of the second piezoelectric layer is greater than the thickness of the first piezoelectric layer, at least one ladder type filter including at least one of the first acoustic wave resonators and at least one of the second acoustic wave resonators is configured, a plurality of the second acoustic wave resonators among all the second acoustic wave resonators are included in at least one of the ladder type filters, and all of the second acoustic wave resonators included in the ladder type filter are series arm resonators of the ladder type filter.
  • the filter device comprising a plurality of the second acoustic wave resonators, the external connection terminals including a through electrode penetrating the second piezoelectric substrate and an electrode pad provided on the fourth main surface of the second piezoelectric substrate and connected to the through electrode, the thickness of the second piezoelectric layer is greater than the thickness of the first piezoelectric layer, at least one ladder type filter including at least one of the first acoustic wave resonators and at least one of the second acoustic wave resonators is configured, a plurality of the second acoustic wave resonators among all the second acoustic wave resonators are included in at least one of the ladder type filters, and all of the second acoustic wave resonators included in the ladder type filter are parallel arm resonators of the ladder type filter.
  • a filter device according to any one of ⁇ 8> to ⁇ 10>, in which the cut angle of the first piezoelectric layer and the cut angle of the second piezoelectric layer are different from each other.
  • ⁇ 12> A filter device according to any one of ⁇ 8> to ⁇ 11>, in which the material used for the first piezoelectric layer is different from the material used for the second piezoelectric layer.
  • the filter device according to any one of ⁇ 8> to ⁇ 12>, wherein the first piezoelectric substrate includes a first intermediate layer provided between the first support substrate and the first piezoelectric layer, the second piezoelectric substrate includes a second intermediate layer provided between the second support substrate and the second piezoelectric layer, and the thickness of the first intermediate layer and the thickness of the second intermediate layer are different from each other.
  • ⁇ 14> A filter device according to any one of ⁇ 8> to ⁇ 13>, in which the thickness of the first support substrate and the thickness of the second support substrate are different from each other.
  • a filter device according to any one of ⁇ 8> to ⁇ 14>, in which the material used for the first support substrate is different from the material used for the second support substrate.
  • ⁇ 16> The filter device according to any one of ⁇ 8> to ⁇ 15>, in which, in a plan view, the direction in which the first electrode fingers and the second electrode fingers of the IDT electrode of the first acoustic wave resonator extend intersects with the direction in which the first electrode fingers and the second electrode fingers of the IDT electrode of the second acoustic wave resonator extend.
  • the filter device according to any one of ⁇ 8> to ⁇ 16>, further comprising a first dielectric film provided on the first piezoelectric layer so as to cover the IDT electrode of the first elastic wave resonator, and a second dielectric film provided on the second piezoelectric layer so as to cover the IDT electrode of the second elastic wave resonator, and the thickness of the first dielectric film and the thickness of the second dielectric film are different from each other.
  • ⁇ 18> The filter device according to any one of ⁇ 8> to ⁇ 17>, further comprising a first dielectric film provided on the first piezoelectric layer so as to cover the IDT electrode of the first elastic wave resonator, and a second dielectric film provided on the second piezoelectric layer so as to cover the IDT electrode of the second elastic wave resonator, and the material used for the first dielectric film is different from the material used for the second dielectric film.
  • a filter device according to any one of ⁇ 8> to ⁇ 18>, in which the thickness of the IDT electrode of the first elastic wave resonator and the thickness of the IDT electrode of the second elastic wave resonator are different from each other.
  • a filter device according to any one of ⁇ 8> to ⁇ 19>, in which the material used for the IDT electrode of the first elastic wave resonator is different from the material used for the IDT electrode of the second elastic wave resonator.
  • Reference Signs List 2A, 2B ...first and second piezoelectric substrates 2a to 2d...first to fourth main surfaces 2e...side surfaces 3A, 3B...first and second support substrates 4A, 4B...first and second intermediate layers 5A, 5B...first and second piezoelectric layers 6...electrode pads 7...through electrodes 8A...support bodies 8B...column members 9...bumps 10...filter device 11...external connection terminals 12A, 12B...first and second signal terminals 13A, 13B...first and second elastic wave resonators 14A, 14B...reflector 15...IDT electrodes 16, 17...first and second bus bars 18, 19...first and second electrode fingers 21...External connection terminal 25...External electrode 28...Dielectric film 30...Filter device 31A, 31B...First and second filters 40...Filter device 41A, 41B...First and second filters 50...Filter device 52A, 52B...First and second piezoelectric substrates 53A, 53B...First and second support substrates

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)

Abstract

Selon la présente invention, un dispositif de filtre 10 comprend : un premier substrat piézoélectrique 2A ayant une première surface principale 2a et une deuxième surface principale 2b opposées l'une à l'autre ; au moins un premier résonateur à ondes acoustiques 13A qui comprend une électrode IDT disposée sur la première surface principale 2a du premier substrat piézoélectrique 2A, le premier résonateur à ondes acoustiques 13A étant un résonateur à bras en série ou un résonateur à bras en parallèle ; un corps de support 8A qui est disposé sur la première surface principale 2a du premier substrat piézoélectrique 2A et est disposé de façon à entourer le premier résonateur à ondes acoustiques 13A ; un deuxième substrat piézoélectrique 2B qui est disposé sur le corps de support 8A et comprend une troisième surface principale 2c positionnée sur le côté du premier substrat piézoélectrique 2A et une quatrième surface principale 2d opposée à la troisième surface principale 2c ; et au moins un deuxième résonateur à ondes acoustiques 13B qui comprend une électrode IDT disposée sur la troisième surface principale 2c du deuxième substrat piézoélectrique 2B, le deuxième résonateur à ondes acoustiques 13B ayant au moins un résonateur à bras en série. Le coefficient Ksaw de couplage électromécanique du deuxième substrat piézoélectrique (2B) est inférieur au coefficient Ksaw de couplage électromécanique du premier substrat piézoélectrique 2A. Le ou les deuxièmes résonateurs à ondes acoustiques 13B comprennent un résonateur à bras en série qui a la fréquence anti-résonance la plus basse parmi tous les résonateurs à bras en série configurés sur le premier substrat piézoélectrique 2A et le deuxième substrat piézoélectrique 2B.
PCT/JP2023/036224 2022-10-11 2023-10-04 Dispositif de filtre WO2024080205A1 (fr)

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JP2022163325 2022-10-11
JP2022-163325 2022-10-11

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WO2024080205A1 true WO2024080205A1 (fr) 2024-04-18

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004173236A (ja) * 2002-11-08 2004-06-17 Murata Mfg Co Ltd 分波器および通信装置
JP2017204743A (ja) * 2016-05-11 2017-11-16 太陽誘電株式会社 フィルタおよびマルチプレクサ

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004173236A (ja) * 2002-11-08 2004-06-17 Murata Mfg Co Ltd 分波器および通信装置
JP2017204743A (ja) * 2016-05-11 2017-11-16 太陽誘電株式会社 フィルタおよびマルチプレクサ

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