JP2010263296A - Elastic boundary wave device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a spurious signal resulting from a higher mode in an elastic boundary wave device with a filter unit. <P>SOLUTION: The elastic boundary wave device 1 includes an elastic boundary wave filter unit 10, and an elastic wave resonator 20. The elastic boundary wave filter unit 10 has an input terminal 11 and output terminals 12a, 12b. The elastic wave resonator 20 is connected to the elastic boundary wave filter unit 10. A frequency of response in the higher mode of an elastic boundary wave generated in the elastic wave resonator 20, and a frequency in the higher mode of the elastic boundary wave generated in the elastic boundary wave filter unit 10 are made equal. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a boundary acoustic wave device, and more particularly, to a boundary acoustic wave device including a longitudinally coupled resonator type boundary acoustic wave filter unit and a boundary acoustic wave resonator connected to the filter unit.

  In recent years, an elastic wave device such as a band rejection filter has been widely used in communication terminals capable of transmitting and receiving a plurality of types of bands. As the acoustic wave device, in addition to the most widely used surface acoustic wave device, a boundary acoustic wave device disclosed in, for example, the following Patent Document 1 is known. Since the boundary acoustic wave device can be downsized as compared with the surface acoustic wave device, it has attracted much attention.

  The boundary acoustic wave device includes a piezoelectric substrate, a first dielectric layer formed on the piezoelectric substrate, a second dielectric layer formed on the first dielectric layer, and a piezoelectric substrate. And an IDT electrode formed at a boundary between the first dielectric layer and the first dielectric layer. The second dielectric layer is a dielectric layer having a higher speed of sound than the first dielectric layer. Typically, the first dielectric layer is formed from silicon oxide and the second dielectric layer is formed from silicon nitride.

WO98 / 52279

  As described above, the boundary acoustic wave device can be downsized as compared with the surface acoustic wave device. However, in the boundary acoustic wave device having a filter function, higher-order modes of the boundary acoustic waves generated in the IDT electrodes constituting the filter unit are confined in the first dielectric layer, which causes spurious. There was a problem.

  The present invention has been made in view of such a point, and an object thereof is to suppress spurious due to a higher-order mode in a boundary acoustic wave device having a filter section.

  The boundary acoustic wave device according to the present invention includes a boundary acoustic wave filter unit and a boundary acoustic wave resonator. The boundary acoustic wave filter unit has an input terminal and an output terminal. The boundary acoustic wave resonator is connected to the boundary acoustic wave filter unit. In the boundary acoustic wave device according to the present invention, the frequency of the higher-order mode response of the boundary acoustic wave generated in the boundary acoustic wave resonator and the response of the higher-order mode of the boundary acoustic wave generated in the boundary acoustic wave filter unit. The frequency is made equal.

  In a specific aspect of the boundary acoustic wave device according to the present invention, the boundary acoustic wave resonator is connected between the input terminal or the output terminal and the boundary acoustic wave filter unit.

  In another specific aspect of the boundary acoustic wave device according to the present invention, the boundary acoustic wave resonator is connected between the input terminal and the boundary acoustic wave filter unit.

  In another specific aspect of the boundary acoustic wave device according to the present invention, the boundary acoustic wave filter unit is a longitudinally coupled resonator type boundary acoustic wave filter unit.

  In still another specific aspect of the boundary acoustic wave device according to the present invention, the frequency of the response of the main mode of the boundary acoustic wave generated in the boundary acoustic wave resonator and the main boundary acoustic wave generated in the boundary acoustic wave filter unit. The frequency of the mode response is different from each other. According to this structure, it can suppress that a filter characteristic deteriorates by the main mode of the boundary acoustic wave which generate | occur | produces in a boundary acoustic wave resonator. Specifically, it is possible to suppress the occurrence of spurious due to the main mode of the boundary acoustic wave generated in the boundary acoustic wave resonator.

  In still another specific aspect of the boundary acoustic wave device according to the present invention, each of the boundary acoustic wave filter unit and the boundary acoustic wave resonator includes a piezoelectric substrate and a first dielectric formed on the piezoelectric substrate. A body layer, a second dielectric layer formed on the first dielectric layer and having a higher sound velocity than the first dielectric layer, and a boundary between the piezoelectric substrate and the first dielectric layer. And the frequency of the main mode response of the boundary acoustic wave generated in the boundary acoustic wave resonator, and the frequency of the response of the main mode of the boundary acoustic wave generated in the boundary acoustic wave filter unit. Are different from each other in at least one of the wavelength of the IDT electrode, the duty of the IDT electrode, and the thickness of the first dielectric layer between the boundary acoustic wave resonator and the boundary acoustic wave filter unit. ing.

  In another specific aspect of the boundary acoustic wave device according to the present invention, the first dielectric layer is made of silicon oxide, and the second dielectric layer is made of silicon nitride.

  In the present invention, the frequency of the higher-order mode response of the boundary acoustic wave generated in the boundary acoustic wave resonator is made equal to the frequency of the higher-order mode response of the boundary acoustic wave generated in the boundary acoustic wave filter unit. Therefore, the spurious attributed to the higher order mode of the boundary acoustic wave generated in the boundary acoustic wave filter unit can be suppressed by the higher order mode of the boundary acoustic wave generated in the boundary acoustic wave resonator.

1 is a schematic diagram of a boundary acoustic wave device. It is the schematic sectional drawing which expanded the part in which the IDT electrode of the boundary acoustic wave apparatus is formed. As a comparative example, the frequency of the higher-order mode response of the boundary acoustic wave generated in the boundary acoustic wave resonator is not equal to the frequency of the higher-order mode response of the boundary acoustic wave generated in the boundary acoustic wave filter section. It is a graph showing the transmission characteristic of a boundary acoustic wave apparatus. It is a graph showing the impedance characteristic of the elastic boundary wave resonator in a comparative example. It is the graph which written together the impedance characteristic of the boundary acoustic wave resonator in a comparative example, and the insertion loss of the boundary acoustic wave apparatus. It is a graph showing the phase characteristic of the elastic boundary wave resonator in a comparative example. It is the graph which wrote together the phase characteristic of the boundary acoustic wave resonator in a comparative example, and the insertion loss of the boundary acoustic wave apparatus. It is the graph which described together the insertion loss of 2500 MHz vicinity of the boundary acoustic wave apparatus in an Example, and the insertion loss of 2500 MHz vicinity of the boundary acoustic wave apparatus in a comparative example. It is the graph which described together the insertion loss and impedance characteristic of 2500 MHz vicinity of the boundary acoustic wave apparatus in an Example, and the insertion loss and impedance characteristic of 2500 MHz vicinity of the boundary acoustic wave apparatus in a comparative example. It is the graph which wrote together the insertion loss and phase characteristic of 2500 MHz vicinity of the boundary acoustic wave apparatus in an Example, and the insertion loss and phase characteristic of 2500 MHz vicinity of the boundary acoustic wave apparatus in a comparative example. It is a schematic diagram of a boundary acoustic wave device according to a modification.

  Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

  FIG. 1 is a schematic diagram of a boundary acoustic wave device according to this embodiment. FIG. 2 is a schematic cross-sectional view in which a portion where the IDT electrode of the boundary acoustic wave device according to the present embodiment is formed is enlarged. In FIG. 1, for convenience of drawing, the number of electrode fingers and the like in the IDT electrode and the reflector are drawn less than the actual number.

  The boundary acoustic wave device 1 of the present embodiment is a boundary acoustic wave device using an SH type boundary acoustic wave. As shown in FIG. 1, the boundary acoustic wave device 1 of this embodiment includes a longitudinally coupled resonator type boundary acoustic wave filter unit 10. The longitudinally coupled resonator type boundary acoustic wave filter unit 10 includes a balanced-unbalanced conversion function including an input terminal (balanced signal terminal) 11 and first and second output terminals (balanced signal terminals) 12a and 12b. This is a balanced type longitudinally coupled resonator type boundary acoustic wave filter unit.

  The longitudinally coupled resonator type boundary acoustic wave filter unit 10 is a so-called 3IDT type longitudinally coupled resonator type acoustic wave filter unit. The longitudinally coupled resonator type boundary acoustic wave filter unit 10 includes first to third IDT electrodes 13 to 15 and first to third IDT electrodes 13 to 15 arranged along the boundary acoustic wave propagation direction. First and second grating reflectors 16 and 17 are provided on both sides of the provided region in the boundary acoustic wave propagation direction. One end side of the second IDT electrode 14 located at the center of the first to third IDT electrodes 13 to 15 is connected to the input terminal 11. On the other hand, the other end side of the second IDT electrode 14 is connected to the ground electrode. One end side of each of the first and third IDT electrodes 13 and 15 located on both sides of the second IDT electrode 14 in the boundary acoustic wave propagation direction is connected to a ground electrode. The other end side of the first IDT electrode 13 is connected to the first output terminal 12a. On the other hand, the other end side of the third IDT electrode 15 is connected to the second output terminal 12b.

  A boundary acoustic wave resonator 20 is connected between the longitudinally coupled resonator type boundary acoustic wave filter unit 10 and the input terminal 11. That is, the longitudinally coupled resonator type boundary acoustic wave filter unit 10 and the boundary acoustic wave resonator 20 are connected in series.

  The boundary acoustic wave resonator 20 includes an IDT electrode 21 and first and second grating reflectors 22 and 23 arranged on both sides of the IDT electrode 21 in the boundary acoustic wave propagation direction. One side of the IDT electrode 21 is connected to the input terminal 11. The other side of the IDT electrode 21 is connected to one side of the second IDT electrode 14 of the longitudinally coupled resonator-type boundary acoustic wave filter unit 10.

Next, the film configuration of the longitudinally coupled resonator type boundary acoustic wave filter unit 10 and the boundary acoustic wave resonator 20 will be described in detail with reference to FIG. Each of the longitudinally coupled resonator type boundary acoustic wave filter unit 10 and the boundary acoustic wave resonator 20 includes a piezoelectric substrate 30. In the present embodiment, the piezoelectric substrate 30 is formed of a 27.5 ° YX LiNbO ₃ substrate. However, the piezoelectric substrate 30 is not limited to this, and can be formed of an appropriate piezoelectric material such as LiNbO ₃ , LiTaO ₃ , or quartz.

  A first dielectric layer 31 is formed on the piezoelectric substrate 30. A second dielectric layer 32 is formed on the first dielectric layer 31. In the present embodiment, the first dielectric layer 31 is made of silicon oxide, and the second dielectric layer 32 is made of silicon nitride. However, the forming material of the first and second dielectric layers 31 and 32 is not particularly limited as long as the sound speed of the second dielectric layer 32 is higher than the sound speed of the first dielectric layer 31. , And can be appropriately selected within the range where the above conditions are satisfied.

In the present embodiment, a base layer 33 made of, for example, Ta ₂ O ₅ is formed at the boundary between the piezoelectric substrate 30 and the first dielectric layer 31. The IDT electrodes 13 to 15 and 21 and the grating reflectors 16, 17, 22, and 23 are formed on the base layer 33. However, in the present invention, the underlayer is not an essential configuration. An IDT electrode or a reflector may be formed at the boundary between the piezoelectric substrate and the first dielectric layer without providing the base layer. 2 and the following description, the IDT electrodes 13 to 15 and 21 are collectively referred to as an IDT electrode 40 for convenience of description.

  The IDT electrode 40 can be formed of an appropriate conductive material such as a metal such as Al, Ag, Au, Pt, Cu, and Ti, or an alloy containing these metals as a main component such as AlCu. The IDT electrode 40 may be constituted by a single conductive layer or a laminate of a plurality of conductive layers. Further, the IDT electrode 40 may be provided with an adhesion layer for improving adhesion with the base layer 33 and the first dielectric layer 31. Specifically, in this embodiment, the IDT electrode 40 includes a Ti layer 41, a Pt layer (first main electrode layer) 42, a Ti layer 43, and an AlCu layer (first conductive layer) on the base layer 33. ) 44, Ti layer 45, Pt layer (second main electrode layer) 46, Ti layer 47, AlCu layer (second conductive layer) 48, and Ti layer 49 were formed in this order from the piezoelectric substrate 30 side. It is comprised by the laminated body.

  In the present embodiment, the frequency of the higher order mode response of the boundary acoustic wave generated in the boundary acoustic wave resonator 20 and the higher order mode response of the boundary acoustic wave generated in the longitudinally coupled resonator type boundary acoustic wave filter unit 10 are described. The frequency of is equal. Specifically, in the present embodiment, the anti-resonance frequency of the higher order mode of the boundary acoustic wave generated in the boundary acoustic wave resonator 20 and the boundary acoustic wave generated in the longitudinally coupled resonator type boundary acoustic wave filter unit 10 are shown. The frequency of the higher-order mode response is made equal. Therefore, spurious due to the higher order mode of the boundary acoustic wave generated in the longitudinally coupled resonator type boundary acoustic wave filter unit 10 is suppressed by the higher order mode of the boundary acoustic wave generated in the boundary acoustic wave resonator 20. Can do.

  In this specification, “the frequency of the response of the higher order mode of the boundary acoustic wave generated in the boundary acoustic wave filter unit” is formed by the higher order mode of the boundary acoustic wave generated in the boundary acoustic wave filter unit. The frequency band of the pass band or stop band.

  The higher-order mode includes not only the secondary mode but also the third and higher modes. That is, “the frequency of the higher-order mode response of the boundary acoustic wave generated in the boundary acoustic wave resonator is equal to the frequency of the higher-order mode response of the boundary acoustic wave generated in the boundary acoustic wave filter unit” The frequency of any one of the second and higher order modes of the boundary acoustic wave generated in the boundary acoustic wave resonator and any one of the second and higher order modes of the boundary acoustic wave generated in the boundary acoustic wave filter unit This means that the passband or stopband frequency band formed by the response is equal.

  For example, the passband or stopband formed by the frequency of the response of the third order mode of the boundary acoustic wave generated in the boundary acoustic wave resonator and the response of the second order mode of the boundary acoustic wave generated in the boundary acoustic wave filter unit. The frequency band may be equal. However, since the response becomes smaller as the mode becomes higher, the frequency of the response of the secondary mode of the boundary acoustic wave generated in the boundary acoustic wave resonator and the secondary mode of the boundary acoustic wave generated in the boundary acoustic wave filter unit. The frequency band of the pass band or stop band formed by the response is preferably made equal. By doing so, higher-order mode spurious can be suppressed more effectively.

  The frequency of the response of the higher order mode of the boundary acoustic wave generated in the boundary acoustic wave resonator is the case where the boundary acoustic wave resonator is connected in series with the boundary acoustic wave filter unit as in this embodiment. This is the antiresonance frequency of the higher order mode of the boundary acoustic wave generated in the boundary acoustic wave resonator. When the boundary acoustic wave resonator is connected between the connection point between the input terminal or the output terminal and the boundary acoustic wave filter unit and the ground potential, the boundary acoustic wave generated in the boundary acoustic wave resonator is The resonance frequency of the higher order mode.

  Hereinafter, this effect will be described in more detail based on specific examples.

  FIG. 3 shows that the frequency of the high-order mode response of the boundary acoustic wave generated in the boundary acoustic wave resonator is not equal to the frequency of the high-order mode response of the boundary acoustic wave generated in the boundary acoustic wave filter unit. It is a graph showing the transmission characteristic of the boundary acoustic wave apparatus as a comparative example. FIG. 4 is a graph showing the impedance characteristics of the boundary acoustic wave resonator in the comparative example, and FIG. 5 shows both the impedance characteristics of the boundary acoustic wave resonator in the comparative example and the insertion loss of the boundary acoustic wave device. It is a graph. FIG. 6 is a graph showing the phase characteristics of the boundary acoustic wave resonator in the comparative example. FIG. 7 is a graph showing both the phase characteristics of the boundary acoustic wave resonator and the insertion loss of the boundary acoustic wave device in the comparative example.

  In the example shown in FIG. 3, spurious due to the higher order mode of the boundary acoustic wave generated in the boundary acoustic wave filter unit is generated in the vicinity of 2500 MHz. The insertion loss of the spurious portion is about 17 dB. From the graph shown in FIG. 5, it can be seen that the higher order mode of the boundary acoustic wave resonator appears in the vicinity of 2600 MHz, which is different from the spurious frequency of 2500 MHz. Therefore, in the comparative example, the frequency of the response of the higher order mode of the boundary acoustic wave generated in the boundary acoustic wave resonator and the frequency of the response of the higher order mode of the boundary acoustic wave generated in the boundary acoustic wave filter unit are It can be seen that are not equal.

  On the other hand, in this embodiment, as shown in FIGS. 9 and 10, the frequency of the higher-order mode response of the boundary acoustic wave generated in the boundary acoustic wave resonator 20 and the longitudinally coupled resonator type boundary acoustic wave filter are used. The frequency of the high-order mode response of the boundary acoustic wave generated in the section 10 is made equal. Specifically, in the present embodiment, the anti-resonance frequency of the higher order mode of the boundary acoustic wave generated in the boundary acoustic wave resonator 20 and the boundary acoustic wave generated in the longitudinally coupled resonator type boundary acoustic wave filter unit 10 are shown. The frequency of the high-order mode response, that is, the frequency band of the pass band is made equal. For this reason, as shown in FIGS. 8 to 10, the boundary acoustic wave thin film generated in the longitudinally coupled resonator type boundary acoustic wave filter unit 10 by the higher order mode of the boundary acoustic wave generated in the boundary acoustic wave resonator 20. The spurious attributed to the higher order mode can be suppressed. Specifically, in this embodiment and the comparative example, spurious is suppressed by about 5 dB.

  Based on the above results, the frequency of the higher-order mode response of the boundary acoustic wave generated in the boundary acoustic wave resonator is equal to the frequency of the higher-order mode response of the boundary acoustic wave generated in the boundary acoustic wave filter section. Thus, it is understood that the spurious attributed to the higher order mode of the boundary acoustic wave generated in the boundary acoustic wave filter unit can be suppressed by the higher order mode of the boundary acoustic wave generated in the boundary acoustic wave resonator.

  In this embodiment, the frequency of the main mode response of the boundary acoustic wave generated in the boundary acoustic wave resonator 20 and the response of the main mode of the boundary acoustic wave generated in the longitudinally coupled resonator type boundary acoustic wave filter unit 10 are described. It is preferable that the frequency is different from each other. By doing in this way, it can suppress that a filter characteristic deteriorates by the main mode of the boundary acoustic wave which generate | occur | produces in the boundary acoustic wave resonator 20. FIG. Generation of spurious due to the main mode of the boundary acoustic wave generated in the boundary acoustic wave resonator 20 can be suppressed.

  In the present specification, the “frequency of the main mode response of the boundary acoustic wave filter unit” refers to the frequency band of the pass band or stop band formed by the main mode of the boundary acoustic wave generated in the boundary acoustic wave filter unit. I mean.

  The “frequency of the main mode response of the boundary acoustic wave generated in the boundary acoustic wave resonator” means that the boundary acoustic wave resonator is connected in series with the boundary acoustic wave filter unit as in this embodiment. In this case, the antiresonance frequency of the main mode of the boundary acoustic wave generated in the boundary acoustic wave resonator is obtained. When the boundary acoustic wave resonator is connected between the connection point between the input terminal or the output terminal and the boundary acoustic wave filter unit and the ground potential, the boundary acoustic wave generated in the boundary acoustic wave resonator is The resonance frequency of the higher order mode.

  In the boundary acoustic wave resonator 20 and the longitudinally coupled resonator type boundary acoustic wave filter unit 10, the method of making the frequency of the higher-order mode response mutually the same and making the frequency of the main mode response different from each other is as follows. There is no particular limitation. As a method of making the response frequency of the main mode different from each other, for example, one of the wavelength (λ) of the IDT electrode, the duty, and the thickness of the first dielectric layer 31 is longitudinally coupled to the boundary acoustic wave resonator 20. A method of differentiating the resonator type boundary acoustic wave filter unit 10 may be mentioned.

  The design parameters in the above examples and comparative examples are as follows.

Example:
Piezoelectric substrate 30: 27.5 ° YX LiNbO ₃ substrate IDT electrode 40: Ti layer 41 (10 nm), Pt layer 42 (23 nm), Ti layer 43 (10 nm), AlCu layer 44 (175 nm), Ti layer 45 ( 10 nm), Pt layer 46 (23 nm), Ti layer 47 (10 nm), AlCu layer 48 (100 nm), Ti layer 49 (10 nm)
First dielectric layer 31: silicon oxide layer having a thickness of 550 nm Second dielectric layer 32: silicon nitride layer having a thickness of 2000 nm

Longitudinal coupled resonator type boundary acoustic wave filter 10:
Propagation direction: ψ = 0 degree Cross width: 27λ
Duty: 0.50
Logarithm of reflector 16: 14.5 pair Wavelength of reflector 16: 1.918 μm
Logarithm of IDT13: 19.0 pair Wavelength of IDT13: 1.897 μm (however, eight adjacent to IDT14 have a wavelength of 1.815 μm)
Logarithm of IDT14: 19.0 pair Wavelength of IDT14: 1.879 μm (however, 7 adjacent to IDTs 13 and 15 have a wavelength of 1.791 μm)
Logarithm of IDT15: 19.0 pairs Wavelength of IDT15: 1.879 μm (However, eight adjacent to IDT14 have a wavelength of 1.815 μm)
Logarithm of reflector 17: 14.5 pair Wavelength of reflector 17: 1.918 μm

Boundary acoustic wave resonator 21:
Propagation direction: ψ = 0 degrees Cross width: 30λ
Duty: 0.50
Logarithm of reflectors 22 and 23: 25 pairs Wavelength of reflectors 22 and 23: 1.900 μm
Logarithm of IDT21: 60.0 pair Wavelength of IDT21: 1.900 μm

Comparative example:
Piezoelectric substrate: 27.5 ° YX LiNbO ₃ substrate IDT electrode 40: Ti layer 41 (10 nm), Pt layer 42 (23 nm), Ti layer 43 (10 nm), AlCu layer 44 (175 nm), Ti layer 45 (10 nm) ), Pt layer 46 (23 nm), Ti layer 47 (10 nm), AlCu layer 48 (100 nm), Ti layer 49 (10 nm)
First dielectric layer: silicon oxide layer having a thickness of 550 nm Second dielectric layer: silicon nitride layer having a thickness of 2000 nm

Longitudinal coupled resonator type boundary acoustic wave filter 10:
Propagation direction: ψ = 0 degree Cross width: 27λ
Duty: 0.50
Logarithm of reflector 16: 14.5 pair Wavelength of reflector 16: 1.918 μm
Logarithm of IDT13: 19.0 pair Wavelength of IDT13: 1.897 μm (however, eight adjacent to IDT14 have a wavelength of 1.815 μm)
Logarithm of IDT14: 19.0 pair Wavelength of IDT14: 1.879 μm (however, 7 adjacent to IDTs 13 and 15 have a wavelength of 1.791 μm)
Logarithm of IDT15: 19.0 pairs Wavelength of IDT15: 1.879 μm (However, eight adjacent to IDT14 have a wavelength of 1.815 μm)
Logarithm of reflector 17: 14.5 pair Wavelength of reflector 17: 1.918 μm

Boundary acoustic wave resonator 21:
Propagation direction: ψ = 0 degrees Cross width: 30λ
Duty: 0.50
Logarithm of reflectors 16 and 17: 25 pairs Wavelength of reflectors 16 and 17: 1.842 μm
Logarithm of IDT21: 60.0 pair Wavelength of IDT21: 1.842 μm

  Hereinafter, modifications of the embodiment will be described. However, in the following description of the modified examples, members having substantially the same functions as those of the above-described embodiment are referred to by common reference numerals, and description thereof is omitted.

(Modification)
In the above-described embodiment, the example in which the boundary acoustic wave resonator is connected between the input terminal and the boundary acoustic wave filter unit has been described. However, the present invention is not limited to this configuration. For example, as shown in FIG. 11, boundary acoustic wave resonators 20a and 20b may be provided between the longitudinally coupled resonator type boundary acoustic wave filter unit 10 and the output terminals 12a and 12b.

  In the above embodiment, the boundary acoustic wave resonator is connected in series to the boundary acoustic wave filter unit. However, the boundary acoustic wave resonator includes an input terminal or an output terminal and a boundary acoustic wave. You may connect between the connection point between filter parts, and ground potential. In this case, the higher-order mode resonance frequency of the boundary acoustic wave generated in the boundary acoustic wave resonators 20a and 20b and the higher-order mode frequency of the boundary acoustic wave generated in the longitudinally coupled resonator type boundary acoustic wave filter unit 10 are used. And are made equal.

  In the above embodiment, an example in which a so-called 3IDT type longitudinally coupled resonator type acoustic wave filter unit is provided as the boundary acoustic wave filter unit has been described. However, in the present invention, the boundary acoustic wave filter unit is not limited to the 3IDT type longitudinally coupled resonator type acoustic wave filter unit. The boundary acoustic wave filter unit may be, for example, a 5IDT type or 7IDT type longitudinally coupled resonator type elastic wave filter unit.

  The boundary acoustic wave filter unit may be a filter unit other than a longitudinally coupled resonator type boundary acoustic wave filter unit such as a ladder type filter unit using boundary acoustic waves.

DESCRIPTION OF SYMBOLS 1 ... Elastic boundary wave apparatus 10 ... Longitudinal coupling resonator type | mold boundary acoustic wave filter part 11 ... Input terminal 12a ... 1st output terminal 12b ... 2nd output terminal 13 ... 1st IDT electrode 14 ... 2nd IDT electrode DESCRIPTION OF SYMBOLS 15 ... 3rd IDT electrode 16 ... 1st grating reflector 17 ... 2nd grating reflector 20, 20a, 20b ... Elastic boundary wave resonator 21 ... IDT electrode 22 ... 1st grating reflector 23 ... 2nd Grating reflector 30 ... piezoelectric substrate 31 ... first dielectric layer 32 ... second dielectric layer 33 ... underlying layer 40 ... IDT electrodes 41, 43, 45, 47, 49 ... Ti layer 42 ... Pt layer 44 ... AlCu layer 46 ... Pt layer 48 ... AlCu layer

Claims (7)

A boundary acoustic wave filter unit having an input terminal and an output terminal;
A boundary acoustic wave resonator connected to the boundary acoustic wave filter unit;
A boundary acoustic wave device in which the frequency of the higher order mode response of the boundary acoustic wave generated in the boundary acoustic wave resonator is equal to the frequency of the higher order mode response of the boundary acoustic wave generated in the boundary acoustic wave filter unit. .   The boundary acoustic wave device according to claim 1, wherein the boundary acoustic wave resonator is connected between the input terminal or the output terminal and the boundary acoustic wave filter unit.   The boundary acoustic wave device according to claim 1, wherein the boundary acoustic wave resonator is connected between the input terminal and the boundary acoustic wave filter unit.   The boundary acoustic wave device according to any one of claims 1 to 3, wherein the boundary acoustic wave filter unit is a longitudinally coupled resonator type boundary acoustic wave filter unit.   The frequency of the main mode response of the boundary acoustic wave generated in the boundary acoustic wave resonator is different from the frequency of the main mode response of the boundary acoustic wave generated in the boundary acoustic wave filter unit. 5. The boundary acoustic wave device according to claim 4. Each of the boundary acoustic wave filter unit and the boundary acoustic wave resonator includes a piezoelectric substrate, a first dielectric layer formed on the piezoelectric substrate, and a first dielectric layer. A second dielectric layer formed at a higher speed of sound than the first dielectric layer, and an IDT electrode formed at a boundary between the piezoelectric substrate and the first dielectric layer. ,
The elastic mode is such that the frequency of the response of the main mode of the boundary acoustic wave generated in the boundary acoustic wave resonator is different from the frequency of the response of the main mode of the boundary acoustic wave generated in the boundary acoustic wave filter unit. The at least one of the wavelength of the IDT electrode, the duty of the IDT electrode, and the thickness of the first dielectric layer is different between the boundary wave resonator and the boundary acoustic wave filter unit. 5. The boundary acoustic wave device according to 5.   The boundary acoustic wave device according to claim 6, wherein the first dielectric layer is made of silicon oxide, and the second dielectric layer is made of silicon nitride.

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