Elastic wave device
By using a dielectric film containing Li and Ta in the elastic wave device, and setting a dielectric film with different piezoelectric properties and polarization directions, the problem of large-scale elastic wave resonator is solved, and the fractional bandwidth is precisely adjusted and the electrostatic capacitance is maintained.
Patent Information
- Application Number
- CN202380089402.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-12-27
- Filing Date
- 2023-12-15
- Publication Date
- 2025-07-25
AI Technical Summary
Adjustment of electromechanical coupling coefficients of existing elastic wave resonators leads to a larger filter, making it difficult to adjust fractional bandwidth without increasing size.
A dielectric film structure including Li and Ta is adopted, and a first and second dielectric film with different piezoelectric properties, polarization directions and crystal structures are provided on a piezoelectric substrate, which are used in the first and second elastic wave resonators respectively, and the fractional bandwidth is adjusted by adjusting the thickness of the dielectric film.
It is realized that the fractional bandwidth of each elastic wave resonator is accurately adjusted without increasing the device size, so as to keep the electrostatic capacitance basically unchanged.
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Figure CN120380697A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to an elastic wave device having a plurality of elastic wave resonators. Background Art
[0002] Conventionally, elastic wave devices having a plurality of elastic wave resonators have been widely used as filters for portable telephones and the like. In Patent Document 1 described below, an example of an elastic wave device as an elastic wave resonator is disclosed. In this elastic wave device, a dielectric is provided on a piezoelectric substrate. Comb-shaped electrodes are provided on the dielectric. By changing the film thickness of the dielectric, the electromechanical coupling coefficient in the elastic wave device changes. Further, Patent Document 1 shows an example of a filter having the above-described elastic wave device.
[0003] Prior Art Documents
[0004] Patent Documents
[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2008-067289 Summary of the Invention
[0006] Problems to be Solved by the Invention
[0007] By adjusting the electromechanical coupling coefficient in the elastic wave resonator, the fractional bandwidth of the elastic wave resonator can be adjusted. Further, in Patent Document 1, as examples of the dielectric provided between the piezoelectric substrate and the comb-shaped electrodes, a silicon oxide film and an aluminum oxide film are cited. However, the dielectric constants of the silicon oxide film and the aluminum oxide film are relatively small. Therefore, in the elastic wave device of Patent Document 1, when a desired capacitance is to be obtained, the elastic wave device needs to be made large. Thus, as a whole filter, it also tends to be large-sized.
[0008] An object of the present invention is to provide an elastic wave device capable of easily adjusting the fractional bandwidth in each elastic wave resonator without causing large-sizing.
[0009] Means for Solving the Problems
[0010] The elastic wave device according to the present invention includes: a piezoelectric substrate including a piezoelectric layer having a first main surface and a second main surface facing each other; a first IDT electrode and a second IDT electrode directly or indirectly provided on the first main surface of the piezoelectric layer; and a first dielectric film and a second dielectric film provided on at least one of the first main surface and the second main surface of the piezoelectric layer. A first elastic wave resonator is formed by a portion of the piezoelectric substrate where the first IDT electrode is provided, the first IDT electrode, and the first dielectric film, and a second elastic wave resonator is formed by a portion of the piezoelectric substrate where the second IDT electrode is provided, the second IDT electrode, and the second dielectric film. The first dielectric film and the second dielectric film each have one of a structure containing Li and Ta and a structure containing Li and Nb, and at least any one of piezoelectricity, polarization direction, and crystal structure is different between the first dielectric film and the second dielectric film.
[0011] Advantages of the Invention
[0012] According to the elastic wave device of the present invention, it is possible to easily adjust the fractional bandwidth in each elastic wave resonator without causing an increase in size. Description of the Drawings
[0013] Figure 1 is a circuit diagram of the elastic wave device according to the first embodiment of the present invention.
[0014] Figure 2 is a schematic front cross-sectional view showing a part of each of the first elastic wave resonator and the second elastic wave resonator in the first embodiment of the present invention.
[0015] Figure 3 is a schematic front cross-sectional view showing a part of the elastic wave resonator of the reference example.
[0016] Figure 4 is a graph showing the relationship between the thickness of the first dielectric film of the first elastic wave resonator and the thickness of the second dielectric film of the second elastic wave resonator and the fractional bandwidth in the first embodiment of the present invention, and the fractional bandwidth of the elastic wave resonator of the reference example.
[0017] Figure 5 is a graph showing the relationship between the thickness of the first dielectric film of the first elastic wave resonator and the thickness of the second dielectric film of the second elastic wave resonator and the electrostatic capacitance in the first embodiment of the present invention, and the electrostatic capacitance of the elastic wave resonator of the reference example.
[0018] Figure 6 is a schematic top view of the first elastic wave resonator in the first embodiment of the present invention.
[0019] Figure 7 is a schematic front cross-sectional view showing a part of each of the first elastic wave resonator and the second elastic wave resonator in the second embodiment of the present invention.
[0020] Figure 8 (a) of is a schematic front cross-sectional view of the first elastic wave resonator in the third embodiment of the present invention, Figure 8 and (b) of is a schematic front cross-sectional view of the second elastic wave resonator in the third embodiment of the present invention.
[0021] Figure 9 (a) of is a schematic front cross-sectional view of the first elastic wave resonator in the fourth embodiment of the present invention, Figure 9 and (b) of is a schematic front cross-sectional view of the second elastic wave resonator in the fourth embodiment of the present invention.
[0022] Figure 10 (a) of is a schematic front cross-sectional view of the first elastic wave resonator in the fifth embodiment of the present invention, Figure 10 and (b) of is a schematic front cross-sectional view of the second elastic wave resonator in the fifth embodiment of the present invention.
[0023] Figure 11 is a schematic diagram of an elastic wave device according to the sixth embodiment of the present invention. Detailed Embodiments
[0024] Hereinafter, specific embodiments of the present invention will be described with reference to the drawings, whereby the present invention will be made clear.
[0025] In addition, it should be noted in advance that each embodiment described in this specification is illustrative, and partial replacement or combination of structures can be made between different embodiments.
[0026] Figure 1 is a circuit diagram of an elastic wave device according to the first embodiment of the present invention.
[0027] The elastic wave device 10 of the present embodiment is a ladder filter. The elastic wave device 10 has a first signal terminal 13A and a second signal terminal 13B, a plurality of inductors, and a plurality of series arm resonators and a plurality of parallel arm resonators. In the present embodiment, the plurality of series arm resonators and the plurality of parallel arm resonators are all elastic wave resonators. Specifically, the elastic wave device 10 is a bandpass filter of Band41. More specifically, the elastic wave device 10 is a transmit filter, and the passband of the elastic wave device 10 is 2496 MHz to 2690 MHz.
[0028] However, the passband of the elastic wave device 10 is not limited to the above. Furthermore, the elastic wave device according to the present invention is not limited to a transmission filter, and may also be a reception filter. The elastic wave device according to the present invention is not limited to being a single filter, and may also be a multiplexer having a plurality of filters. The elastic wave device according to the present invention only needs to have a plurality of elastic wave resonators. The elastic wave device 10 of the present embodiment has a first elastic wave resonator and a second elastic wave resonator. Hereinafter, the specific structures of the first elastic wave resonator and the second elastic wave resonator will be shown.
[0029] Figure 2 FIG. 4 is a schematic front cross-sectional view showing a part of each of the first elastic wave resonator and the second elastic wave resonator in the first embodiment. In addition, in Figure 2 FIG. 5, the first elastic wave resonator 1A and the second elastic wave resonator 1B are schematically arranged, but the arrangement of the first elastic wave resonator 1A and the second elastic wave resonator 1B is not particularly limited.
[0030] The first elastic wave resonator 1A and the second elastic wave resonator 1B share the piezoelectric substrate 2. Moreover, the first elastic wave resonator 1A has a first IDT electrode 8A. The second elastic wave resonator 1B has a second IDT electrode 8B. The first IDT electrode 8A and the second IDT electrode 8B are provided on the piezoelectric substrate 2. By applying an alternating voltage to the first IDT electrode 8A, elastic waves are excited. The same applies to the second IDT electrode 8B.
[0031] In addition, the first IDT electrode 8A and the second IDT electrode 8B each have a plurality of electrode fingers. In Figure 2 FIG. 6, the vicinity of a pair of electrode fingers in the first IDT electrode 8A and the vicinity of a pair of electrode fingers in the second IDT electrode 8B are shown.
[0032] The first IDT electrode 8A includes a laminated metal film. Specifically, the layer structure of the first IDT electrode 8A is a structure in which a Ti layer, an Al layer, and a Ti layer are laminated in this order from the piezoelectric substrate 2 side. The second IDT electrode 8B also includes the same laminated metal film as the first IDT electrode 8A. However, the materials of the first IDT electrode 8A and the second IDT electrode 8B are not limited to the above. Alternatively, the first IDT electrode 8A and the second IDT electrode 8B may also include a single-layer metal film.
[0033] The piezoelectric substrate 2 is a laminated substrate including a piezoelectric layer 6. That is, the piezoelectric substrate 2 is a substrate having piezoelectricity. In the present embodiment, the piezoelectric layer 6 is a piezoelectric single crystal layer containing LiNbO3. The crystal structure of the piezoelectric layer 6 is of the LiNbO3 type. However, the piezoelectric layer 6 may also be, for example, a piezoelectric single crystal layer containing LiTaO3. The piezoelectric layer 6 preferably has a structure containing Li and Nb, or a structure containing Li and Ta.
[0034] Furthermore, the piezoelectric substrate 2 has a support substrate 3, a high acoustic velocity film 4 as a high acoustic velocity material layer, and a low acoustic velocity film 5. The support substrate 3, the high acoustic velocity film 4, the low acoustic velocity film 5, and the piezoelectric layer 6 are laminated in this order. The high acoustic velocity material layer is a layer with a relatively high acoustic velocity. Specifically, the acoustic velocity of the bulk wave propagating in the high acoustic velocity material layer is higher than the acoustic velocity of the elastic wave propagating in the piezoelectric layer 6. On the other hand, the low acoustic velocity film 5 is a film with a relatively low acoustic velocity. Specifically, the acoustic velocity of the bulk wave propagating in the low acoustic velocity film 5 is lower than the acoustic velocity of the bulk wave propagating in the piezoelectric layer 6.
[0035] In the present embodiment, silicon is used as the material of the support substrate 3. Silicon nitride is used as the material of the high acoustic velocity film 4. Silicon oxide is used as the material of the low acoustic velocity film 5. In addition, the materials of the support substrate 3, the high acoustic velocity film 4, and the low acoustic velocity film 5 are not limited to the above. Alternatively, the piezoelectric substrate 2 may also be a substrate including only the piezoelectric layer 6.
[0036] The piezoelectric layer 6 has a first main surface 6a and a second main surface 6b. The first main surface 6a and the second main surface 6b face each other. The second main surface 6b of the first main surface 6a and the second main surface 6b is located on the side of the support substrate 3. A first dielectric film 7A is provided on the first main surface 6a. The first IDT electrode 8A is provided on the first dielectric film 7A. Therefore, the first IDT electrode 8A is indirectly provided on the first main surface 6a with the first dielectric film 7A interposed therebetween. The first elastic wave resonator 1A is composed of the portion of the piezoelectric substrate 2 where the first IDT electrode 8A is provided, the first IDT electrode 8A, and the first dielectric film 7A.
[0037] In addition, a second dielectric film 7B is provided on the first main surface 6a of the piezoelectric layer 6. In addition, in the first main surface 6a, the position of the portion where the second dielectric film 7B is provided and the position of the portion where the first dielectric film 7A is provided are different from each other. The second IDT electrode 8B is provided on the second dielectric film 7B. Therefore, the second IDT electrode 8B is indirectly provided on the first main surface 6a with the second dielectric film 7B interposed therebetween. The second elastic wave resonator 1B is composed of the portion of the piezoelectric substrate 2 where the second IDT electrode 8B is provided, the second IDT electrode 8B, and the second dielectric film 7B.
[0038] In the present embodiment, when x is set to an arbitrary positive number, the first dielectric film 7A is a LiNbO x film. When y is set to an arbitrary positive number, the second dielectric film 7B is a LiNbO y film. That is, the first dielectric film 7A and the second dielectric film 7B are oxide films containing Li and Nb.
[0039] The physical properties of the first dielectric film 7A and the second dielectric film 7B are shown in Table 1. In addition, although the second dielectric film 7B is not a single crystal film, in Table 1, the values equivalent to those of a single crystal are shown for Young's modulus, Poisson's ratio, and density.
[0040] [Table 1]
[0041]
[0042] As shown in Table 1, the piezoelectric properties are different between the first dielectric film 7A and the second dielectric film 7B. Specifically, in the present embodiment, the first dielectric film 7A does not have piezoelectric properties, and the second dielectric film 7B has piezoelectric properties. However, even when the first dielectric film 7A has piezoelectric properties, the piezoelectric properties can be different between the first dielectric film 7A and the second dielectric film 7B. Alternatively, the polarization directions can be different between the first dielectric film 7A and the second dielectric film 7B. In addition, the structure is not limited to one in which the polarization directions are different between the entire first dielectric film 7A and the second dielectric film 7B. Specifically, the first dielectric film 7A and the second dielectric film 7B may also include portions with different polarization directions. In the present embodiment, the crystal structures are also different between the first dielectric film 7A and the second dielectric film 7B. More specifically, the phrase "the crystal structures are different" means, for example, a case where one is a single crystal and the other is a polycrystal, or the atoms contained are different, etc.
[0043] In addition, the materials of the first dielectric film 7A and the second dielectric film 7B are not limited to the above. For example, the first dielectric film 7A may also be a LiTaO x film. The second dielectric film 7B may also be a LiTaO y film. In addition, x and y are arbitrary positive numbers. Furthermore, the first dielectric film 7A and the second dielectric film 7B are not limited to oxides. Alternatively, for example, the first dielectric film 7A may have a structure containing Li and Ta, and the second dielectric film 7B may have a structure containing Li and Nb. It may also be that the first dielectric film 7A has a structure containing Li and Nb, and the second dielectric film 7B has a structure containing Li and Ta.
[0044] By adjusting the thickness of the first dielectric film 7A, the fractional bandwidth of the first surface acoustic wave resonator 1A can be adjusted. Similarly, by adjusting the thickness of the second dielectric film 7B, the fractional bandwidth of the second surface acoustic wave resonator 1B can be adjusted. In addition, when the resonance frequency is set to fr and the anti-resonance frequency is set to fa, the fractional bandwidth is represented by (|fr - fa| / fr) × 100 [%]. In the surface acoustic wave device 10, the thicknesses of the first dielectric film 7A and the second dielectric film 7B are different from each other. However, the thicknesses of the first dielectric film 7A and the second dielectric film 7B may also be the same.
[0045] The present embodiment is characterized by having the following structures 1) and 2). 1) Each of the first dielectric film 7A and the second dielectric film 7B has one of a structure containing Li and Ta and a structure containing Li and Nb. 2) In the first dielectric film 7A and the second dielectric film 7B, at least any one of piezoelectricity, polarization direction, and crystal structure is different from each other. Thus, it is possible to easily adjust the fractional bandwidth in each surface acoustic wave resonator of the surface acoustic wave device 10 without causing the surface acoustic wave device 10 to be enlarged. The details of this effect will be described below.
[0046] A plurality of first surface acoustic wave resonators 1A with different thicknesses of the first dielectric film 7A were prepared. Similarly, a plurality of second surface acoustic wave resonators 1B with different thicknesses of the second dielectric film 7B were prepared. Furthermore, a Figure 3 surface acoustic wave resonator 101 of the reference example shown was prepared. The surface acoustic wave resonator 101 of the reference example is different from the first surface acoustic wave resonator 1A and the second surface acoustic wave resonator 1B in that it does not have the first dielectric film 7A and the second dielectric film 7B. In addition, a plurality of surface acoustic wave resonators of the reference example with the same design parameters were prepared. The design parameters of the prepared first surface acoustic wave resonator 1A are as follows. Here, the wavelength defined by the electrode finger pitch of the IDT electrode is set to λ. The electrode finger pitch is the center-to-center distance between adjacent electrode fingers connected to different potentials. Specifically, when the electrode finger pitch is set to p, the wavelength λ is λ = 2p.
[0047] Support substrate 3: Material... Si
[0048] High acoustic velocity film 4: Material... SiN, Thickness... 0.9 μm
[0049] Low acoustic velocity film 5: Material... SiO2, Thickness... 1 μm
[0050] Piezoelectric layer 6: Material... LiNbO3, Thickness... 1 μm
[0051] First dielectric film 7A: Material... LiNbO x 、Thickness... 90 nm, 130 nm or 240 nm
[0052] First IDT electrode 8A: Layer structure... from the piezoelectric layer 6 side, Ti layer / Al layer / Ti layer, thickness... 4 nm / 400 nm / 30 nm from the piezoelectric layer 6 side, duty ratio... 0.5
[0053] Wavelength λ: 4 μm
[0054] The design parameters of the prepared second surface acoustic wave resonator 1B are the same as those of the first surface acoustic wave resonator 1A except for the following points. In addition, the design parameters of the second IDT electrode 8B are the same as those of the first IDT electrode 8A.
[0055] Second dielectric film 7B: Material... LiNbO y and thickness... 100 nm, 160 nm or 290 nm
[0056] The design parameters of the prepared surface acoustic wave resonator 101 of the reference example are the same as those of the first surface acoustic wave resonator 1A except for the point of not having the first dielectric film 7A. In addition, the design parameters of the IDT electrode of the surface acoustic wave resonator 101 are the same as those of the first IDT electrode 8A.
[0057] By Figure 4 and Figure 5 show the fractional bandwidth and electrostatic capacitance of each prepared surface acoustic wave resonator. In addition, in Figure 5 the electrostatic capacitance is shown as the electrostatic capacitance of the portion where each pair of electrode fingers in the IDT electrode is located.
[0058] Figure 4 is a graph showing the relationship between the thickness of the first dielectric film of the first surface acoustic wave resonator in the first embodiment, the thickness of the second dielectric film of the second surface acoustic wave resonator, and the fractional bandwidth, and the fractional bandwidth of the surface acoustic wave resonator of the reference example. Figure 5 is a graph showing the relationship between the thickness of the first dielectric film of the first surface acoustic wave resonator in the first embodiment, the thickness of the second dielectric film of the second surface acoustic wave resonator, and the electrostatic capacitance, and the electrostatic capacitance of the surface acoustic wave resonator of the reference example. Figure 4 and Figure 5 the horizontal axis in is the thickness of the first dielectric film 7A in the case of the first surface acoustic wave resonator 1A, and the thickness of the second dielectric film 7B in the case of the second surface acoustic wave resonator 1B.
[0059] As Figure 4As shown, the thicker the thickness of the first dielectric film 7A, the smaller the fractional bandwidth value in the first elastic wave resonator 1A. Similarly, the thicker the thickness of the second dielectric film 7B, the smaller the fractional bandwidth value in the second elastic wave resonator 1B. In addition, in the elastic wave resonator 101 of the reference example, the thickness of the dielectric film is equivalent to 0. Therefore, the fractional bandwidth values in the first elastic wave resonator 1A and the second elastic wave resonator 1B are smaller than the fractional bandwidth value in the elastic wave resonator 101 of the reference example.
[0060] In addition, the change trend of the fractional bandwidth in the first elastic wave resonator 1A with respect to the change in the thickness of the first dielectric film 7A and the change trend of the fractional bandwidth in the second elastic wave resonator 1B with respect to the change in the thickness of the second dielectric film 7B are different from each other. Thus, in each elastic wave resonator of the elastic wave device 10, not only can the fractional bandwidth be adjusted by adjusting the thickness of the dielectric film, but also the fractional bandwidth can be adjusted by selecting whether to use the first dielectric film 7A or the second dielectric film 7B in each elastic wave resonator. Therefore, in the elastic wave device 10, the fractional bandwidth can be easily adjusted for each elastic wave resonator.
[0061] For example, when the first dielectric film 7A is selected such that the change slope of the fractional bandwidth with respect to the thickness of the first dielectric film 7A becomes smaller near the desired fractional bandwidth in the first elastic wave resonator 1A, the fractional bandwidth of the first elastic wave resonator 1A can be adjusted with high precision. Moreover, when the second dielectric film 7B is selected such that the change slope of the fractional bandwidth with respect to the thickness of the second dielectric film 7B becomes smaller near the desired fractional bandwidth in the second elastic wave resonator 1B, the fractional bandwidth of the second elastic wave resonator 1B can be adjusted with high precision. In this way, the fractional bandwidth in each elastic wave resonator of the elastic wave device 10 can be easily adjusted with high precision.
[0062] On the other hand, as Figure 5 shown, it can be seen that even if the thickness of the first dielectric film 7A is changed, there is almost no change in the electrostatic capacitance of the first elastic wave resonator 1A. Similarly, it can be seen that even if the thickness of the second dielectric film 7B is changed, there is almost no change in the electrostatic capacitance of the second elastic wave resonator 1B. Furthermore, the electrostatic capacitances of the first elastic wave resonator 1A and the second elastic wave resonator 1B are the same as the electrostatic capacitance in the elastic wave resonator 101 of the reference example. That is, in the present embodiment, as Figure 2 shown, even if the first dielectric film 7A and the second dielectric film 7B are provided on the piezoelectric layer 6, the electrostatic capacitance hardly becomes smaller.
[0063] For example, in the case where a dielectric film contains silicon oxide, aluminum oxide, etc. as in the past, the dielectric constant of the dielectric film is small. Therefore, the electrostatic capacitance of the laminate of the piezoelectric layer and the dielectric film becomes small. Thus, in the structure in which the dielectric film is provided, in order to obtain a desired electrostatic capacitance, it is necessary to increase the area of the laminate of the piezoelectric layer and the dielectric film.
[0064] In contrast, in the present embodiment, even when the first dielectric film 7A and the second dielectric film 7B are provided on the piezoelectric layer 6, the electrostatic capacitances of the first SAW resonator 1A and the second SAW resonator 1B hardly decrease. The same applies when adjusting the thicknesses of the first dielectric film 7A and the second dielectric film 7B. Therefore, it is possible to easily adjust the fractional bandwidths of the first SAW resonator 1A and the second SAW resonator 1B of the SAW device 10 without causing the SAW device 10 to become large.
[0065] Hereinafter, the structure of the present embodiment will be described in more detail.
[0066] Figure 6 is a schematic plan view of the first SAW resonator in the first embodiment. In Figure 6 the wirings connected to the first SAW resonator 1A are omitted.
[0067] The first IDT electrode 8A has a first bus bar 16A, a second bus bar 17A, and the plurality of electrode fingers. The first bus bar 16A and the second bus bar 17A face each other. Specifically, the plurality of electrode fingers are a plurality of first electrode fingers 18A and a plurality of second electrode fingers 19A. One ends of the plurality of first electrode fingers 18A are respectively connected to the first bus bar 16A. One ends of the plurality of second electrode fingers 19A are respectively connected to the second bus bar 17A. The plurality of first electrode fingers 18A and the plurality of second electrode fingers 19A are interlaced with each other. The first electrode fingers 18A and the second electrode fingers 19A are connected to different potentials. In the present embodiment, when the direction in which the plurality of first electrode fingers 18A and the plurality of second electrode fingers 19A extend is defined as the electrode finger extending direction, the electrode finger extending direction is orthogonal to the surface acoustic wave propagation direction.
[0068] The first SAW resonator 1A has a pair of reflectors 9A and 9B. The reflectors 9A and 9B are provided on the first main surface 6a of the piezoelectric layer 6. More specifically, in the present embodiment, each reflector is indirectly provided on the first main surface 6a with the first dielectric film 7A interposed therebetween. The reflectors 9A and 9B face each other with the first IDT electrode 8A interposed therebetween in the surface acoustic wave propagation direction. The first SAW resonator 1A is a surface acoustic wave resonator.
[0069] Similarly, Figure 2The second elastic wave resonator 1B shown is also a surface acoustic wave resonator. The second IDT electrode 8B has a pair of bus bars, a plurality of first electrode fingers 18B, and a plurality of second electrode fingers 19B. The second elastic wave resonator 1B has a pair of reflectors. In addition, the elastic wave resonators other than the first elastic wave resonator 1A and the second elastic wave resonator 1B in the elastic wave device 10 also have IDT electrodes and a pair of bus bars in the same manner.
[0070] Each electrode finger of the first IDT electrode 8A and the second IDT electrode 8B has two surfaces and side surfaces that face each other in the thickness direction. The side surfaces are connected to the two surfaces. In the present embodiment, the side surfaces of each electrode finger extend obliquely with respect to the normal direction of the first main surface 6a of the piezoelectric layer 6. However, the side surfaces of each electrode finger may also extend parallel to the normal direction of the first main surface 6a.
[0071] Hereinafter, the circuit structure in the present embodiment will be described. As Figure 1 shown, the plurality of series arm resonators of the elastic wave device 10 are a series arm resonator S1, a series arm resonator S2, a series arm resonator S3, a series arm resonator S4, and a series arm resonator S5. Between the first signal terminal 13A and the second signal terminal 13B, the series arm resonator S1, the series arm resonator S2, the series arm resonator S3, the series arm resonator S4, and the series arm resonator S5 are connected in series with each other in sequence.
[0072] In the present embodiment, the second signal terminal 13B is an antenna terminal. The antenna terminal is connected to an antenna. However, the second signal terminal 13B may not be an antenna terminal.
[0073] The plurality of shunt arm resonators of the elastic wave device 10 are a shunt arm resonator P1, a shunt arm resonator P2, a shunt arm resonator P3, and a shunt arm resonator P4. The shunt arm resonator P1 is connected between the connection point between the series arm resonator S1 and the series arm resonator S2 and the ground potential. The shunt arm resonator P2 is connected between the connection point between the series arm resonator S2 and the series arm resonator S3 and the ground potential. The shunt arm resonator P3 is connected between the connection point between the series arm resonator S3 and the series arm resonator S4 and the ground potential. The shunt arm resonator P4 is connected between the connection point between the series arm resonator S4 and the series arm resonator S5 and the ground potential.
[0074] The plurality of inductors of the elastic wave device 10 are an inductor L1, an inductor L2, an inductor L3, and an inductor L4. The inductor L1 is connected between the first signal terminal 13A and the series arm resonator S1. The inductor L2 is connected between the series arm resonator S5 and the second signal terminal 13B. The inductor L3 is connected between the shunt arm resonator P2 and the ground potential. The inductor L4 is connected between the shunt arm resonator P4 and the ground potential.
[0075] In addition, the circuit structure of the elastic wave device 10 is not limited to the above. The elastic wave device 10 may not necessarily have a plurality of inductors. In the case where the elastic wave device according to the present invention is a ladder filter, the elastic wave device only needs to have at least one series arm resonator and at least one parallel arm resonator.
[0076] In the present embodiment, the first elastic wave resonator 1A is a parallel arm resonator P1. The second elastic wave resonator 1B is a parallel arm resonator P2. However, the arrangement of the first elastic wave resonator 1A and the second elastic wave resonator 1B is not limited to the above. The first elastic wave resonator 1A and the second elastic wave resonator 1B only need to be any elastic wave resonators in the elastic wave device 10.
[0077] The elastic wave device 10 has one first elastic wave resonator 1A and one second elastic wave resonator 1B. In addition, the elastic wave device 10 may also have a plurality of first elastic wave resonators 1A. Similarly, the elastic wave device 10 may also have a plurality of second elastic wave resonators 1B.
[0078] As described above, the passband of the elastic wave device 10 is 2496 MHz to 2690 MHz. In this way, the elastic wave device 10 is a wideband filter. Furthermore, the low-frequency side of the passband of the elastic wave device is close to the WiFi band. In such a case, it is preferable that the steepness is high on the low-frequency side of the passband. In the present specification, a high steepness means that near the frequency at the end of the passband, the change amount of the frequency is small with respect to the change amount of a certain fixed attenuation amount. Regarding the steepness on the low-frequency side of the passband, the influence of the fractional bandwidth of the parallel arm resonator is large. Specifically, by reducing the value of the fractional bandwidth of the parallel arm resonator, the steepness on the low-frequency side of the passband can be improved.
[0079] In such a case, as in the present embodiment, it is preferable that the first elastic wave resonator 1A and the second elastic wave resonator 1B are parallel arm resonators. Thereby, it is possible to easily reduce the values of the fractional bandwidths of the first elastic wave resonator 1A and the second elastic wave resonator 1B, that is, the parallel arm resonators. Therefore, the steepness on the low-frequency side of the passband can be easily improved. More preferably, one of the first elastic wave resonator 1A and the second elastic wave resonator 1B is the parallel arm resonator having the highest resonance frequency among the plurality of parallel arm resonators of the elastic wave device 10. Thereby, the steepness on the low-frequency side of the passband can be easily and effectively improved. Thereby, in the elastic wave device 10, it is possible to more reliably prevent signals such as the WiFi band outside the passband from passing through.
[0080] In addition, in the present embodiment, among the plurality of elastic wave resonators of the elastic wave device 10, the first dielectric film 7A or the second dielectric film 7B is used in the elastic wave resonator having a reduced fractional bandwidth value. That is, the elastic wave device 10 includes a first elastic wave resonator 1A, a second elastic wave resonator 1B, and elastic wave resonators other than the first elastic wave resonator 1A and the second elastic wave resonator 1B. For example, the elastic wave device 10 may also include the elastic wave resonator 101 of the reference example. The elastic wave device 10 includes the first elastic wave resonator 1A and the second elastic wave resonator 1B having a small fractional bandwidth value, and a plurality of elastic wave resonators having a large fractional bandwidth value. Thereby, it is possible to achieve both an expanded passband and improved steepness.
[0081] In addition, for example, when both the first dielectric film 7A and the second dielectric film 7B are lithium niobate films, and when the crystal structures of both dielectric films are different from each other, both dielectric films may be any of the following examples. That is, both dielectric films may be, for example, any of ilmenite-type lithium niobate, LiNb3O8, Li3NbO4, or LiNbO2.
[0082] When the first dielectric film 7A and the second dielectric film 7B each have a crystal structure with Euler angles (φ, θ, ψ), and when the polarization directions of both dielectric films are different from each other, for example, it is sufficient that θ in the Euler angles of both dielectric films is different.
[0083] In addition, in each of the first dielectric film 7A and the second dielectric film 7B, the structure may not necessarily be uniform. For example, the first dielectric film 7A or the second dielectric film 7B may be a film in which the crystal structure, physical property value, or polarization direction varies in the thickness direction. When one of the first dielectric film 7A and the second dielectric film 7B has the above-described non-uniform structure and the other has a uniform structure, at least any one of piezoelectricity, polarization direction, and crystal structure is different between the first dielectric film 7A and the second dielectric film 7B. Or, for example, when both dielectric films have a non-uniform structure, and when the crystal structure included in one dielectric film is not included in the other dielectric film, the crystal structures are different between the first dielectric film 7A and the second dielectric film 7B.
[0084] Preferably, at least one of the first dielectric film 7A and the second dielectric film 7B has a structure containing Li and Nb, and the piezoelectric layer 6 has a structure containing Li and Nb. When the first dielectric film 7A has a structure containing Li and Nb and the first dielectric film 7A is formed by film formation on the piezoelectric layer 6, the crystallinity of the first dielectric film 7A can be easily improved. The same applies when the second dielectric film 7B has a structure containing Li and Nb.
[0085] Alternatively, preferably, at least one of the first dielectric film 7A and the second dielectric film 7B has a structure containing Li and Ta, and the piezoelectric layer 6 has a structure containing Li and Ta. In this case, the crystallinity of the dielectric film containing Li and Ta among the first dielectric film 7A and the second dielectric film 7B can also be easily improved.
[0086] In addition, when the first dielectric film 7A has a structure containing Li and Ta, for example, when x is set to any positive number, it may be LiTaO x . When the second dielectric film 7B has a structure containing Li and Ta, for example, when y is set to any positive number, it may be LiTaO y . However, as described above, the first dielectric film 7A and the second dielectric film 7B are not limited to oxide films.
[0087] The thickness of the first dielectric film 7A and the thickness of the second dielectric film 7B are preferably different from each other as in the present embodiment. In this case, the fractional bandwidth can be more reliably adjusted to a desired value in the first elastic wave resonator 1A and the second elastic wave resonator 1B, respectively.
[0088] In Figure 2 In the piezoelectric substrate 2 of the present embodiment shown, a high acoustic velocity film 4, a low acoustic velocity film 5, and a piezoelectric layer 6 are laminated in this order. Thereby, the energy of the elastic wave can be effectively confined to the piezoelectric layer 6 side. In addition, in the above, as an example of the materials of the high acoustic velocity film 4 and the low acoustic velocity film 5, silicon nitride and silicon oxide are shown, but other materials can also be used for the high acoustic velocity film 4 and the low acoustic velocity film 5. Examples of these materials are shown below. Examples of the material of the support substrate 3 are also shown together.
[0089] As the material of the low acoustic velocity film 5, for example, dielectrics such as glass, silicon oxide, silicon oxynitride, lithium oxide, tantalum oxide, or a compound in which fluorine, carbon, or boron is added to silicon oxide, or a material mainly composed of the above materials can be used. In addition, in the present specification, the so-called main component means a component whose proportion exceeds 50 wt%. The material of the above main component may exist in any one of single crystal, polycrystal, and amorphous states, or in a state in which they are mixed.
[0090] As the material of the high acoustic velocity material layer, i.e., the high acoustic velocity film 4, for example, piezoelectric bodies such as aluminum nitride, lithium tantalate, lithium niobate, and quartz, ceramics such as alumina, sapphire, magnesia, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, forsterite, spinel, and sialon, dielectrics such as alumina, silicon oxynitride, DLC (diamond-like carbon), and diamond, semiconductors such as silicon, or materials mainly composed of the above materials can also be used. In addition, in the above spinel, an aluminum compound containing one or more elements selected from Mg, Fe, Zn, Mn, etc. and oxygen is included. As examples of the above spinel, MgAl2O4, FeAl2O4, ZnAl2O4, and MnAl2O4 can be cited.
[0091] As the material of the support substrate 3, for example, piezoelectric bodies such as aluminum nitride, lithium tantalate, lithium niobate, and quartz, ceramics such as alumina, sapphire, magnesia, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, forsterite, spinel, and sialon, dielectrics such as alumina, silicon oxynitride, DLC (diamond-like carbon), and diamond, semiconductors such as silicon, or materials mainly composed of the above materials can also be used. In addition, in the above spinel, an aluminum compound containing one or more elements selected from Mg, Fe, Zn, Mn, etc. and oxygen is included. As examples of the above spinel, MgAl2O4, FeAl2O4, ZnAl2O4, and MnAl2O4 can be cited.
[0092] In addition, the laminated structure of the piezoelectric substrate is not limited to the above. For example, the piezoelectric substrate may also be a laminated substrate of a support substrate, a high acoustic velocity film as the high acoustic velocity material layer, and a piezoelectric layer. Or, the high acoustic velocity material layer may also be a high acoustic velocity support substrate. In this case, the piezoelectric substrate may also be a laminated substrate of a high acoustic velocity support substrate, a low acoustic velocity film, and a piezoelectric layer, or may also be a laminated substrate of a high acoustic velocity support substrate and a piezoelectric layer. Even in these cases, the energy of the elastic wave can be effectively confined to the piezoelectric layer side.
[0093] Figure 7 It is a schematic front cross-sectional view showing a part of each of the first elastic wave resonator and the second elastic wave resonator in the second embodiment.
[0094] This embodiment is different from the first embodiment in the positions of the first dielectric film 7A and the second dielectric film 7B. Except for the above points, the elastic wave device of this embodiment has the same structure as the elastic wave device 10 of the first embodiment.
[0095] The first dielectric film 7A is provided on the second major surface 6b of the piezoelectric layer 6. The first IDT electrode 8A is directly provided on the first major surface 6a of the piezoelectric layer 6. The first IDT electrode 8A and the first dielectric film 7A are opposed to each other with the piezoelectric layer 6 therebetween.
[0096] Similarly, the second dielectric film 7B is provided on the second major surface 6b of the piezoelectric layer 6. The second IDT electrode 8B is directly provided on the first major surface 6a of the piezoelectric layer 6. The second IDT electrode 8B and the second dielectric film 7B are opposed to each other with the piezoelectric layer 6 therebetween.
[0097] As in the present embodiment, it is preferable that both the first dielectric film 7A and the second dielectric film 7B are provided on the second major surface 6b of the piezoelectric layer 6, and both the first IDT electrode 8A and the second IDT electrode 8B are directly provided on the first major surface 6a of the piezoelectric layer 6. In this case, the crystallinity of the first IDT electrode 8A and the second IDT electrode 8B can be made consistent. Therefore, the difference in the withstand voltage of the first surface acoustic wave resonator 21A and the second surface acoustic wave resonator 21B can be reduced.
[0098] As Figure 7 shown, the thicknesses of the first dielectric film 7A and the second dielectric film 7B are different from each other. On the other hand, the thickness of the portion where the first dielectric film 7A and the low sound velocity film 25 are laminated is the same as the thickness of the portion where the second dielectric film 7B and the low sound velocity film 25 are laminated. This is because the thicknesses of the portions of the low sound velocity film 25 laminated with the first dielectric film 7A and the second dielectric film 7B are made different from each other so that the thicknesses of both portions become the same.
[0099] Since the thicknesses of the above-mentioned both portions are the same, the productivity of the surface acoustic wave device can be improved. More specifically, when manufacturing a surface acoustic wave device, for example, after forming a plurality of IDT electrodes and the like on a laminated wafer, singulation is performed. Thereby, a plurality of surface acoustic wave devices are obtained. By singulating the laminated wafer, a plurality of piezoelectric substrates are obtained. Moreover, when the thicknesses of both are the same, it is easy to fix the thickness of the laminated wafer. Therefore, it is easy to form the laminated wafer, and the productivity of the surface acoustic wave device can be improved.
[0100] In the present embodiment, as in the first embodiment, the first dielectric film 7A and the second dielectric film 7B each have one of a structure containing Li and Ta and a structure containing Li and Nb. Moreover, in the first dielectric film 7A and the second dielectric film 7B, at least any one of piezoelectricity, polarization direction, and crystal structure is different from each other. Thereby, it is possible to easily adjust the fractional bandwidth in each surface acoustic wave resonator of the surface acoustic wave device without causing the surface acoustic wave device to be enlarged.
[0101] Further, for example, it may also be the following structure, that is, between the first dielectric film 7A and the second dielectric film 7B, the piezoelectricity, polarization direction, and crystal structure are the same, but the thicknesses are different. In this case, it is also possible to easily adjust the fractional bandwidth in each elastic wave resonator of the elastic wave device without causing the enlargement of the elastic wave device. However, as in the first embodiment and the second embodiment, it is preferable that at least any one of the piezoelectricity, polarization direction, and crystal structure is different between the first dielectric film 7A and the second dielectric film 7B. Thereby, it is possible to more easily adjust the fractional bandwidth in each elastic wave resonator.
[0102] Figure 8 FIG. (a) is a schematic front cross-sectional view of the first elastic wave resonator in the third embodiment. Figure 8 FIG. (b) is a schematic front cross-sectional view of the second elastic wave resonator in the third embodiment.
[0103] As Figure 8 shown in FIG. (a), the difference between this embodiment and the first embodiment is that the first dielectric film 7A is provided on both the first main surface 6a and the second main surface 6b of the piezoelectric layer 6. As Figure 8 shown in FIG. (b), the difference between this embodiment and the first embodiment is also that the second dielectric film 7B is provided on both the first main surface 6a and the second main surface 6b of the piezoelectric layer 6. Except for the above points, the elastic wave device of this embodiment has the same structure as the elastic wave device 10 of the first embodiment.
[0104] The elastic wave device of this embodiment also has the structures of the above 1) and 2) in the same manner as the elastic wave device 10 of the first embodiment. That is, in the elastic wave device of this embodiment, the first dielectric film 7A and the second dielectric film 7B each have one of the structures including Li and Ta and the structure including Li and Nb. Moreover, at least any one of the piezoelectricity, polarization direction, and crystal structure is different between the first dielectric film 7A and the second dielectric film 7B. Thereby, it is possible to easily adjust the fractional bandwidth in each elastic wave resonator of the elastic wave device without causing the enlargement of the elastic wave device.
[0105] As in the first embodiment to the third embodiment, in the present invention, the first dielectric film 7A and the second dielectric film 7B only need to be provided on at least one of the first main surface 6a and the second main surface 6b of the piezoelectric layer 6.
[0106] Figure 9 FIG. (a) is a schematic front cross-sectional view of the first elastic wave resonator in the fourth embodiment. Figure 9 FIG. (b) is a schematic front cross-sectional view of the second elastic wave resonator in the fourth embodiment.
[0107] As shown in Figure 9 (a) thereof and Figure 9 (b) thereof, the present embodiment is different from the first embodiment in the arrangement of the first dielectric film 7A and the second dielectric film 7B on the first main surface 6a of the piezoelectric layer 6. The present embodiment is also different from the first embodiment in the shapes of the plurality of first electrode fingers 48A and the plurality of second electrode fingers 49A of the first IDT electrode 38A, and the shapes of the plurality of first electrode fingers 48B and the plurality of second electrode fingers 49B of the second IDT electrode 38B. Except for the above points, the surface acoustic wave device of the present embodiment has the same structure as the surface acoustic wave device 10 of the first embodiment.
[0108] As shown in Figure 9 (a) thereof, the side surfaces of the respective electrode fingers of the first IDT electrode 38A extend parallel to the normal direction of the first main surface 6a of the piezoelectric layer 6. Similarly, as shown in Figure 9 (b) thereof, the side surfaces of the respective electrode fingers of the second IDT electrode 38B extend parallel to the normal direction of the first main surface 6a of the piezoelectric layer 6.
[0109] As shown in Figure 9 (a) thereof, the edge portion of the first dielectric film 7A in the surface acoustic wave propagation direction and the edge portion of the first IDT electrode 38A in the surface acoustic wave propagation direction overlap in a plan view. More specifically, the edge portion of the first dielectric film 7A in the surface acoustic wave propagation direction and the edge portion of the outermost electrode finger of the first IDT electrode 38A in the surface acoustic wave propagation direction overlap in a plan view. In addition, in this specification, the plan view means observing the surface acoustic wave device from the upper direction in a schematic cross-sectional view such as Figure 9 (a) thereof. For example, in Figure 9 (a) thereof, the side of the first IDT electrode 38A among the piezoelectric layer 6 side and the first IDT electrode 38A side is the upper side.
[0110] As shown in Figure 9 (b) thereof, the edge portion of the second dielectric film 7B in the surface acoustic wave propagation direction and the edge portion of the second IDT electrode 38B in the surface acoustic wave propagation direction overlap in a plan view. More specifically, the edge portion of the second dielectric film 7B in the surface acoustic wave propagation direction and the edge portion of the outermost electrode finger of the second IDT electrode 38B in the surface acoustic wave propagation direction overlap in a plan view.
[0111] The surface acoustic wave device of the present embodiment also has the structures of the above 1) and 2) in the same manner as the surface acoustic wave device 10 of the first embodiment. Thus, it is possible to easily adjust the fractional bandwidth in each surface acoustic wave resonator of the surface acoustic wave device without causing the surface acoustic wave device to be enlarged.
[0112] Figure 10Fig. (a) is a schematic front sectional view of the first elastic wave resonator in the fifth embodiment. Figure 10 Fig. (b) is a schematic front sectional view of the second elastic wave resonator in the fifth embodiment.
[0113] As Figure 10 shown in Fig. (a) and Figure 10 Fig. (b), the difference between this embodiment and the fourth embodiment is that the first elastic wave resonator and the second elastic wave resonator each have a separate piezoelectric substrate 2. In addition, the piezoelectric layer 6 in the first elastic wave resonator has a side surface 6c. The side surface 6c is connected to the first main surface 6a and the second main surface 6b. Similarly, the piezoelectric layer 6 in the second elastic wave resonator also has a side surface 6c. Except for the above points, the elastic wave device of this embodiment has the same structure as the elastic wave device of the fourth embodiment.
[0114] As Figure 10 shown in Fig. (a), the edge portion of the first dielectric film 7A in the elastic wave propagation direction, the edge portion of the first IDT electrode 38A in the elastic wave propagation direction, and the edge portion of the piezoelectric layer 6 in the elastic wave propagation direction overlap in plan view. More specifically, the edge portion of the first dielectric film 7A in the elastic wave propagation direction, the edge portion of the outermost electrode finger of the first IDT electrode 38A in the elastic wave propagation direction, and the side surface 6c of the piezoelectric layer 6 overlap in plan view.
[0115] As Figure 10 shown in Fig. (b), the edge portion of the second dielectric film 7B in the elastic wave propagation direction, the edge portion of the second IDT electrode 38B in the elastic wave propagation direction, and the edge portion of the piezoelectric layer 6 in the elastic wave propagation direction overlap in plan view. More specifically, the edge portion of the second dielectric film 7B in the elastic wave propagation direction, the edge portion of the outermost electrode finger of the second IDT electrode 38B in the elastic wave propagation direction, and the side surface 6c of the piezoelectric layer 6 overlap in plan view.
[0116] The elastic wave device of this embodiment also has the structures of the above 1) and 2) in the same manner as the elastic wave device of the fourth embodiment. Thus, it is possible to easily adjust the fractional bandwidth in each elastic wave resonator of the elastic wave device without causing the elastic wave device to become large.
[0117] In the first to fifth embodiments, an example in which the elastic wave device is a single filter is shown. However, the elastic wave device according to the present invention may also be a multiplexer including a plurality of filters. The first elastic wave resonator and the second elastic wave resonator may also be included in different filters. This example is shown in the sixth embodiment.
[0118] Figure 11It is a schematic diagram of the elastic wave device according to the sixth embodiment.
[0119] The elastic wave device 50 is a multiplexer. The elastic wave device 50 has a common connection terminal 52, a first filter 50A, a second filter 50B, a third filter 50C, and a plurality of other filters. The first filter 50A, the second filter 50B, the third filter 50C, and the plurality of other filters are commonly connected to the common connection terminal 52. In the present embodiment, the common connection terminal 52 is an antenna terminal. However, the common connection terminal 52 may not be an antenna terminal.
[0120] The first filter 50A, the second filter 50B, and the third filter 50C each have a plurality of elastic wave resonators. The first filter 50A, the second filter 50B, and the third filter 50C each have mutually different passbands. In addition, the elastic wave device 50 as a multiplexer only needs to have two or more filters. The circuit structure in each filter of the elastic wave device 50 is not particularly limited.
[0121] The first filter 50A includes a plurality of first elastic wave resonators in the present invention. In addition, the first filter 50A only needs to have at least one first elastic wave resonator. On the other hand, the second filter 50B includes a plurality of second elastic wave resonators in the present invention. In addition, the second filter 50B only needs to have at least one second elastic wave resonator.
[0122] In this embodiment, as in the first embodiment, the first dielectric film and the second dielectric film each have one of a structure containing Li and Ta and a structure containing Li and Nb. Moreover, in the first dielectric film and the second dielectric film, at least any one of piezoelectricity, polarization direction, and crystal structure is different from each other. Thus, it is possible to easily adjust the fractional bandwidth in each elastic wave resonator of the elastic wave device 50 without causing the enlargement of the elastic wave device 50.
[0123] In the elastic wave device 50, the width of the passband of the first filter 50A and the width of the passband of the second filter 50B are different from each other. Moreover, in the present embodiment, it is possible to appropriately select the first dielectric film used for the first elastic wave resonator in the first filter 50A and the second dielectric film used for the second elastic wave resonator in the second filter 50B. Therefore, in the first filter 50A and the second filter 50B, it is possible to easily adjust to the desired width of the passband.
[0124] Preferably, the thickness of the first dielectric film in the first surface acoustic wave resonator included in the first filter 50A and the thickness of the second dielectric film in the second surface acoustic wave resonator included in the second filter 50B are different from each other. In this case, the fractional bandwidth can be more reliably adjusted to a desired value in the first surface acoustic wave resonator and the second surface acoustic wave resonator, respectively. Therefore, the width of the desired passband can be more reliably and easily adjusted in the first filter 50A and the second filter 50B.
[0125] Hereinafter, examples of the embodiments of the surface acoustic wave device according to the present invention will be summarized.
[0126] <1>A surface acoustic wave device includes: a piezoelectric substrate including a piezoelectric layer having a first main surface and a second main surface facing each other; a first IDT electrode and a second IDT electrode directly or indirectly provided on the first main surface of the piezoelectric layer; and a first dielectric film and a second dielectric film provided on at least one of the first main surface and the second main surface of the piezoelectric layer. A first surface acoustic wave resonator is formed by a portion of the piezoelectric substrate where the first IDT electrode is provided, the first IDT electrode, and the first dielectric film, and a second surface acoustic wave resonator is formed by a portion of the piezoelectric substrate where the second IDT electrode is provided, the second IDT electrode, and the second dielectric film. The first dielectric film and the second dielectric film each have a structure including Li and Ta or a structure including Li and Nb, and at least any one of piezoelectricity, polarization direction, and crystal structure is different between the first dielectric film and the second dielectric film.
[0127] <2>The surface acoustic wave device according to <1>, wherein
[0128] when x is set to any positive number, the first dielectric film is a LiTaO x film or a LiNbO x film.
[0129] <3>The surface acoustic wave device according to <1> or <2>, wherein
[0130] when y is set to any positive number, the second dielectric film is a LiTaO y film or a LiNbO y film.
[0131] <4>The surface acoustic wave device according to <1>, wherein
[0132] at least one of the first dielectric film and the second dielectric film is a structure including Li and Nb, and the piezoelectric layer is a structure including Li and Nb.
[0133] <5>The elastic wave device according to <1>, wherein,
[0134] At least one of the first dielectric film and the second dielectric film has a structure containing Li and Ta, and the piezoelectric layer has a structure containing Li and Ta.
[0135] <6>The elastic wave device according to any one of <1> to <5>, wherein,
[0136] The first dielectric film is provided on the first main surface of the piezoelectric layer, and the first IDT electrode is indirectly provided on the first main surface with the first dielectric film interposed therebetween.
[0137] <7>The elastic wave device according to <6>, wherein,
[0138] The second dielectric film is provided on the first main surface of the piezoelectric layer, and the second IDT electrode is indirectly provided on the first main surface with the second dielectric film interposed therebetween.
[0139] <8>The elastic wave device according to any one of <1> to <5>, wherein,
[0140] The first dielectric film is provided on the second main surface of the piezoelectric layer, and the first IDT electrode and the first dielectric film are opposed to each other with the piezoelectric layer interposed therebetween.
[0141] <9>The elastic wave device according to <8>, wherein,
[0142] The second dielectric film is provided on the second main surface of the piezoelectric layer, and the second IDT electrode and the second dielectric film are opposed to each other with the piezoelectric layer interposed therebetween.
[0143] <10>The elastic wave device according to <8> or <9>, wherein,
[0144] The piezoelectric substrate includes a support substrate, and the first dielectric film is provided between the support substrate and the piezoelectric layer.
[0145] <11>The elastic wave device according to any one of <1> to <10>, wherein,
[0146] The thicknesses of the first dielectric film and the second dielectric film are different from each other.
[0147] <12>The elastic wave device according to any one of <1> to <11>, wherein,
[0148] The elastic wave device is a filter including a plurality of elastic wave resonators, and the plurality of elastic wave resonators include the first elastic wave resonator and the second elastic wave resonator.
[0149] <13>According to the elastic wave device described in any one of <1> to <11>, wherein,
[0150] The elastic wave device is a multiplexer including a plurality of filters, and the first elastic wave resonator and the second elastic wave resonator are included in different ones of the filters.
[0151] Description of Reference Numerals
[0152] 1A, 1B: First elastic wave resonator, second elastic wave resonator;
[0153] 2: Piezoelectric substrate;
[0154] 3: Support substrate;
[0155] 4: High acoustic velocity film;
[0156] 5: Low acoustic velocity film;
[0157] 6: Piezoelectric layer;
[0158] 6a, 6b: First main surface, second main surface;
[0159] 6c: Side surface;
[0160] 7A, 7B: First dielectric film, second dielectric film;
[0161] 8A, 8B: First IDT electrode, second IDT electrode;
[0162] 9A, 9B: Reflector;
[0163] 10: Elastic wave device;
[0164] 13A, 13B: First signal terminal, second signal terminal;
[0165] 16A, 17A: First bus bar, second bus bar;
[0166] 18A, 18B: First electrode finger;
[0167] 19A, 19B: Second electrode finger;
[0168] 21A, 21B: First elastic wave resonator, second elastic wave resonator;
[0169] 25: Low acoustic velocity film;
[0170] 38A, 38B: First IDT electrode, second IDT electrode;
[0171] 48A, 48B: First electrode fingers;
[0172] 49A, 49B: Second electrode fingers;
[0173] 50: Surface acoustic wave device;
[0174] 50A to 50C: First filter to third filter;
[0175] 52: Common connection terminal;
[0176] 101: Surface acoustic wave resonator;
[0177] L1 to L4: Inductors;
[0178] P1 to P4: Shunt arm resonators;
[0179] S1 to S5: Series arm resonators.
Claims
1. An elastic wave device comprising: A piezoelectric substrate including a piezoelectric layer having a first main surface and a second main surface facing each other; A first IDT electrode and a second IDT electrode are directly or indirectly provided on the first main surface of the piezoelectric layer; and A first dielectric film and a second dielectric film are provided on at least one of the first main surface and the second main surface of the piezoelectric layer. A first elastic wave resonator is formed by a portion of the piezoelectric substrate where the first IDT electrode is provided, the first IDT electrode, and the first dielectric film. A second elastic wave resonator is formed by the portion of the piezoelectric substrate where the second IDT electrode is provided, the second IDT electrode, and the second dielectric film. The first dielectric film and the second dielectric film each have a structure including Li and Ta and a structure including Li and Nb. The first dielectric film and the second dielectric film are different from each other in at least any one of piezoelectricity, polarization direction, and crystal structure.
2. The elastic wave device according to claim 1, wherein: When x is set to any positive number, the first dielectric film is LiTaO x film or LiNbO x film.
3. The elastic wave device according to claim 1 or 2, wherein: When y is set to any positive number, the second dielectric film is LiTaO y film or LiNbO y film.
4. The elastic wave device according to claim 1, wherein: At least one of the first dielectric film and the second dielectric film has a structure including Li and Nb, and the piezoelectric layer has a structure including Li and Nb.
5. The elastic wave device according to claim 1, wherein: At least one of the first dielectric film and the second dielectric film has a structure including Li and Ta, and the piezoelectric layer has a structure including Li and Ta.
6. The elastic wave device according to any one of claims 1 to 5, wherein: The first dielectric film is provided on the first main surface of the piezoelectric layer, and the first IDT electrode is indirectly provided on the first main surface via the first dielectric film.
7. The elastic wave device according to claim 6, wherein: The second dielectric film is provided on the first main surface of the piezoelectric layer, and the second IDT electrode is indirectly provided on the first main surface via the second dielectric film.
8. The elastic wave device according to any one of claims 1 to 5, wherein: The first dielectric film is provided on the second main surface of the piezoelectric layer, and the first IDT electrode and the first dielectric film are opposed to each other with the piezoelectric layer interposed therebetween.
9. The elastic wave device according to claim 8, wherein: The second dielectric film is provided on the second main surface of the piezoelectric layer, and the second IDT electrode and the second dielectric film are opposed to each other with the piezoelectric layer interposed therebetween.
10. The elastic wave device according to claim 8 or 9, wherein: The piezoelectric substrate includes a supporting substrate. The first dielectric film is provided between the support substrate and the piezoelectric layer.
11. The elastic wave device according to any one of claims 1 to 10, wherein: The first dielectric film and the second dielectric film have different thicknesses from each other.
12. The elastic wave device according to any one of claims 1 to 11, wherein, the elastic wave device is a filter including a plurality of elastic wave resonators, the plurality of elastic wave resonators include the first elastic wave resonator and the second elastic wave resonator.
13. The elastic wave device according to any one of claims 1 to 11, wherein, the elastic wave device is a multiplexer including a plurality of filters, the first elastic wave resonator and the second elastic wave resonator are included in different ones of the filters.
Citation Information
Patent Citations
Surface acoustic wave device and filter
JP2008067289A