Elastic wave device, filter, and multiplexer

Abstract

The invention relates to the technical field of elastic waves, and discloses an elastic wave device, a filter and a multiplexer. The elastic wave device comprises a supporting substrate, a low-sound-velocity layer, a piezoelectric layer and an interdigital transducer, the low-sound-velocity layer is arranged on the supporting substrate, the piezoelectric layer is arranged on the low-sound-velocity layer, the interdigital transducer is arranged on the piezoelectric layer, and the interdigital transducer comprises a temperature coefficient adjusting layer and a mass compensation layer which are sequentially stacked on the piezoelectric layer. According to the elastic wave device, the mass proportion of the temperature coefficient adjusting layer is optimally designed to be within a specific range value, so that the TCF difference value of the resonant frequency and the anti-resonant frequency can be kept at a relatively small level, and the influence of environment temperature change on the elastic wave device is reduced; and the stable performance of a filter and a multiplexer based on the elastic wave device is further maintained.

Description

Technical Field

[0001] This invention relates to the field of elastic wave technology, and more particularly to an elastic wave device, filter, and multiplexer. Background Art

[0002] Elastic wave devices are devices that utilize the propagation properties of sound waves or elastic waves in specific materials to achieve signal processing functions. They are widely used in radio frequency communication systems such as filters, resonators, and multiplexers. With the rapid development of wireless communication technology, the performance requirements for elastic wave devices are becoming increasingly stringent, especially in terms of frequency selectivity, insertion loss, and temperature stability.

[0003] However, existing elastic wave devices still face some key challenges in practical applications, among which the temperature coefficient of frequency (TCF) is one of the most significant challenges in research and application. TCF describes the characteristic of the resonant frequency of an elastic wave device as a function of temperature; the smaller the TCF value, the lower the device's sensitivity to temperature changes. In practical use, due to changes in ambient temperature, elastic wave devices may exhibit frequency drift, which affects the selectivity and insertion loss of filters, ultimately leading to a degraded performance of the communication system.

[0004] Currently, commercially available TF-SAW resonators suffer from problems such as different directions of forward and reverse resonant frequencies and a difference greater than 20ppm / ℃. The resulting increase in VSWR in filters is particularly noticeable. To fundamentally solve this problem, it is necessary to develop TF-SAW resonator designs that minimize the TCF of the resonator while minimizing the TCF difference between the forward and reverse resonant frequencies, i.e., minimizing ΔTCF. Summary of the Invention

[0005] Based on the above problems, the purpose of this invention is to provide an elastic wave device, filter and multiplexer to adjust the frequency temperature coefficient and keep the TCF difference between the positive and negative resonant frequencies within a relatively small range.

[0006] To achieve the above objectives, in a first aspect, the present invention adopts the following technical solution:

[0007] An elastic wave device includes a support substrate, a low-velocity sound layer, a piezoelectric layer, and an interdigital transducer, wherein:

[0008] A low-velocity layer is disposed on the support substrate;

[0009] The piezoelectric layer is placed on the low-velocity layer, and the thickness of the piezoelectric layer is less than λ, where λ is the wavelength of the elastic wave.

[0010] An interdigital transducer is disposed on a piezoelectric layer. The interdigital transducer includes a temperature coefficient adjustment layer and a mass compensation layer stacked sequentially on the piezoelectric layer. The electrode thickness of the temperature coefficient adjustment layer is set to h1, the electrode density of the temperature coefficient adjustment layer is set to ρ1, the electrode thickness of the mass compensation layer is set to h2, and the electrode density of the mass compensation layer is set to ρ2, satisfying 112 / 574≤h1ρ1 / (h1ρ1+h2ρ2)≤64 / 109, and ρ1>3ρ2.

[0011] As an optional solution, the interdigital transducer includes a first electrode finger, a second electrode finger, a first bus bar, and a second bus bar. A plurality of first electrode fingers and second electrode fingers are arranged alternately and parallel to each other in the direction of elastic wave propagation of the interdigital transducer. The first bus bar and the second bus bar are distributed on both sides of the first electrode finger and the second electrode finger. The first end of each first electrode finger is connected to the first bus bar, the first end of each second electrode finger is disconnected from the first bus bar, the second end of each second electrode finger is connected to the second bus bar, and the second end of each first electrode finger is disconnected from the second bus bar. The spacing between two adjacent first bus bars and the spacing between two adjacent second bus bars are both λ.

[0012] As an alternative, a reflector is also provided on the piezoelectric layer and on both sides of the interdigital transducer along the elastic wave propagation direction. The reflector includes a third electrode finger and a third bus bar. Several third electrode fingers are arranged in parallel at intervals along the elastic wave propagation direction of the interdigital transducer. Two third bus bars are distributed at both ends of the third electrode fingers, and the end of each third electrode finger is connected to the corresponding third bus bar.

[0013] As an alternative, the piezoelectric layer is made of lithium tantalate with an Euler angle of (0°, Φ, 0°) and 100°≤Φ≤150°; or, the piezoelectric layer is made of lithium niobate with an Euler angle of (0°, Ω, 0°) and 90°≤Ω≤160°.

[0014] As an alternative, the support substrate includes a high-velocity substrate disposed below the low-velocity layer, with the high-velocity substrate directly abutting the low-velocity layer; or, a trapping material layer is disposed between the high-velocity substrate and the low-velocity layer.

[0015] As an alternative, the material used to trap the material layer includes at least one of amorphous silicon, polycrystalline silicon, amorphous germanium, and polycrystalline germanium.

[0016] As an alternative, the material of the low-velocity layer includes silicon dioxide, silicon oxynitride, tantalum oxide, or at least one of a compound in which fluorine, carbon, or boron has been added to silicon dioxide.

[0017] As an alternative, the temperature coefficient regulating layer is made of at least one of copper, platinum, and tungsten; the mass compensation layer is made of aluminum.

[0018] Secondly, the present invention adopts the following technical solution:

[0019] A filter includes a series arm resonator and a parallel arm resonator, wherein the series arm resonator and / or the parallel arm resonator includes the elastic wave device described above.

[0020] Thirdly, the present invention adopts the following technical solution:

[0021] A multiplexer comprising the aforementioned filter.

[0022] The beneficial effects of this invention are:

[0023] This elastic wave device optimizes the design of the temperature coefficient adjustment layer mass ratio within a specific range, so that the TCF difference between the resonant frequency and the anti-resonant frequency can be kept at a relatively small level. This reduces the impact of ambient temperature changes on the elastic wave device, thereby maintaining the stable performance of filters and multiplexers based on the elastic wave device. Attached Figure Description

[0024] Figure 1 This is a top view of the elastic wave device provided in Embodiment 1 of the present invention;

[0025] Figure 2 This is a structural cross-sectional view of the elastic wave device provided in Embodiment 1 of the present invention;

[0026] Figure 3 This is a schematic diagram showing the variation of the TCFr and TCFa of the elastic wave device provided in Embodiment 1 of the present invention with the mass ratio of the temperature coefficient adjustment layer;

[0027] Figure 4 This is a structural cross-sectional view of the elastic wave device provided in Embodiment 2 of the present invention;

[0028] Figure 5 This is a schematic diagram showing the variation of the TCFr and TCFa of the elastic wave device provided in Embodiment 2 of the present invention with the mass ratio of the temperature coefficient adjustment layer.

[0029] In the attached image:

[0030] 100. Support base plate;

[0031] 110. High-speed acoustic substrate; 120. Trapping material layer;

[0032] 200, Low-sound-velocity layer;

[0033] 300, piezoelectric layer;

[0034] 400. Interdigitated transducer; 401. First electrode finger; 402. Second electrode finger; 403. First busbar; 404. Second busbar;

[0035] 410. Temperature coefficient adjustment layer; 420. Mass compensation layer;

[0036] 500, Reflector; 501, Third Electrode Finger; 502, Third Busbar. Detailed Implementation

[0037] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0038] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0039] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0040] In the description of this embodiment, terms such as "upper," "lower," "left," and "right" are based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of description and simplification of operation, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0041] Furthermore, the terms "first" and "second" are merely used to distinguish between different terms in description and do not have any special meaning.

[0042] Before proceeding, let's first explain and introduce the relevant technologies of elastic wave devices.

[0043] In recent years, elastic wave devices based on piezoelectric substrates have gained widespread attention due to their high Q-factor (quality factor), large electromechanical coupling coefficient, and good heat dissipation, and have been applied in many fields such as radar, communication, and navigation. Elastic wave devices based on piezoelectric substrates consist of a conductive material thin film pattern formed on a piezoelectric substrate. The piezoelectric substrate is a bulk or multilayer substrate made of piezoelectric material, primarily lithium niobate, lithium tantalate, gallium nitride, aluminum nitride, or zinc oxide. The conductive material thin film pattern includes an interdigital transducer (IDT) and a reflector. The interdigital transducer includes multiple first electrode fingers and multiple second electrode fingers interleaved. The distance λ between adjacent first or second electrode fingers is usually referred to as the "wavelength" of the IDT, and the overlapping distance AP between the first and second electrode fingers is usually referred to as the "aperture" of the IDT.

[0044] Because piezoelectric layers are cut to align with the crystal axes of the front and back sides of the piezoelectric layer, different tangential options are available. In the industry, Euler angles are used to define these tangential angles. For example, the Euler angles of a piezoelectric layer cut at 15°Y are (0°, 105°, 0°), the Euler angles of a piezoelectric layer cut at Z are (0°, 0°, 0°), the Euler angles of a piezoelectric layer cut at 128°Y are (0°, 38°, 0°), and the Euler angles of a piezoelectric layer cut at 32°Y and 45°X are (0°, 122°, 45°).

[0045] In addition, the temperature coefficient of frequency (TCF) refers to the characteristic parameter of an elastic wave device that varies with temperature, and it is defined as follows:

[0046] TCF = (1 / f)*(Δf / ΔT);

[0047] Where f is the center frequency of the elastic wave device at the reference temperature, Δf is the frequency offset caused by the temperature change ΔT, and ΔT is the difference between the operating temperature and the reference temperature.

[0048] ΔTCF is defined as the difference (absolute value) between the TCF of the resonant frequency and the anti-resonant frequency, i.e.

[0049] ΔTCF=|TCFr-TCFa|;

[0050] Where TCFr is the TCF at the resonant frequency and TCFa is the TCF at the anti-resonant frequency.

[0051] Example 1:

[0052] Please see Figure 1 and Figure 2 As shown, this embodiment provides an elastic wave device, including a support substrate 100, a low-velocity sound layer 200, a piezoelectric layer 300, and an interdigital transducer 400, wherein:

[0053] A low-velocity layer 200 is disposed on the support substrate 100;

[0054] The piezoelectric layer 300 is disposed on the low sound velocity layer 200, and the thickness of the piezoelectric layer 300 is less than λ, where λ is the wavelength of the elastic wave.

[0055] An interdigital transducer 400 is disposed on a piezoelectric layer 300. The interdigital transducer 400 includes a temperature coefficient adjustment layer 410 and a mass compensation layer 420 stacked sequentially on the piezoelectric layer 300. The electrode thickness of the temperature coefficient adjustment layer 410 is set to h1, and the electrode density of the temperature coefficient adjustment layer 410 is set to ρ1. The electrode thickness of the mass compensation layer 420 is set to h2, and the electrode density of the mass compensation layer 420 is set to ρ2, satisfying 112 / 574≤h1ρ1 / (h1ρ1+h2ρ2)≤64 / 109, and ρ1>3ρ2.

[0056] In this embodiment, the support substrate 100 includes a high-velocity substrate 110 disposed below the low-velocity layer 200. The high-velocity substrate 110 is directly attached to the low-velocity layer 200 to support the piezoelectric layer 300. The high-velocity substrate 110, the low-velocity layer 200, and the piezoelectric layer 300 constitute a multilayer piezoelectric substrate, as detailed below. Figure 2 .

[0057] Specifically, the interdigital transducer 400 includes a first electrode finger 401, a second electrode finger 402, a first bus bar 403, and a second bus bar 404. A plurality of first electrode fingers 401 and second electrode fingers 402 are arranged alternately and parallel to each other in the direction of elastic wave propagation of the interdigital transducer 400. The first bus bar 403 and the second bus bar 404 are distributed on both sides of the first electrode fingers 401 and the second electrode fingers 402. The first end of each first electrode finger 401 is connected to the first bus bar 403, the first end of each second electrode finger 402 is disconnected from the first bus bar 403, the second end of each second electrode finger 402 is connected to the second bus bar 404, and the second end of each first electrode finger 401 is disconnected from the second bus bar 404. The spacing between two adjacent first bus bars 403 and the spacing between two adjacent second bus bars 404 are both λ.

[0058] definition Figure 1 The direction parallel to the x-axis in the coordinate system is the arrangement direction of the first electrode finger 401 and the second electrode finger 402, which is also the direction of elastic wave propagation; the direction parallel to the y-axis in the coordinate system is defined as the length extension direction of the first electrode finger 401 and the second electrode finger 402.

[0059] Furthermore, reflectors 500 are also disposed on the piezoelectric layer 300 and on both sides of the interdigital transducer 400 along the elastic wave propagation direction. The interdigital transducer 400 and the reflectors 500 form a conductive material thin film pattern. The reflector 500 includes a third electrode finger 501 and a third bus bar 502. A plurality of third electrode fingers 501 are arranged parallel to each other at intervals in the elastic wave propagation direction of the interdigital transducer 400. Two third bus bars 502 are distributed at both ends of the third electrode fingers 501, and the end of each third electrode finger 501 is connected to the corresponding third bus bar 502.

[0060] Optionally, the piezoelectric layer 300 is made of lithium tantalate with an Euler angle of (0°, Φ, 0°) and 100°≤Φ≤150°; the temperature coefficient adjustment layer 410 is made of one or more materials with relatively high density, such as copper, platinum, or tungsten; the mass compensation layer 420 is made of aluminum; and the low-velocity layer 200 is made of one or more materials, such as silicon dioxide, glass, silicon oxynitride, tantalum oxide, or a compound with fluorine, carbon, or boron added to silicon dioxide as the main component.

[0061] This embodiment uses the following parameters as examples: the temperature coefficient adjustment layer 410 is a copper electrode; the mass compensation layer 420 is an aluminum electrode; the high-velocity substrate 110 is silicon; the low-velocity layer 200 is silicon dioxide with a thickness of 500 nm; the piezoelectric layer 300 is lithium tantalate cut at 42°Y with Euler angles of (0°, 132°, 0°) and a thickness of 600 nm; and the wavelength λ of the elastic wave is 2 μm.

[0062] Figure 3 A schematic diagram is shown illustrating the variation of TCFr and TCFa of the elastic wave device provided in this embodiment with the mass ratio of the temperature coefficient adjustment layer 410. The mass ratio of the temperature coefficient adjustment layer 410 is defined as the proportion of the mass of the temperature coefficient adjustment layer 410 to the total mass of the electrode, i.e., h1ρ1 / (h1ρ1+h2ρ2). As can be seen from the curve, at the resonant frequency of the elastic wave device, both TCFa and TCFr gradually increase with the increase of the mass ratio of the temperature coefficient adjustment layer 410; while when 112 / 574≤h1ρ1 / (h1ρ1+h2ρ2)≤64 / 109, ΔTCF remains at a relatively small level, indicating better performance.

[0063] Therefore, by optimizing the design of the temperature coefficient adjustment layer 410 to maintain its mass ratio within a specific range, the TCF difference between the resonant frequency and the anti-resonant frequency can be kept at a relatively small level, thereby reducing the impact of ambient temperature changes on the elastic wave device.

[0064] Example 2:

[0065] Based on Embodiment 1, this embodiment provides an elastic wave device, including a support substrate 100, a low-velocity sound layer 200, a piezoelectric layer 300, and an interdigital transducer 400, wherein:

[0066] A low-velocity layer 200 is disposed on the support substrate 100;

[0067] The piezoelectric layer 300 is disposed on the low sound velocity layer 200, and the thickness of the piezoelectric layer 300 is less than λ, where λ is the wavelength of the elastic wave.

[0068] An interdigital transducer 400 is disposed on a piezoelectric layer 300. The interdigital transducer 400 includes a temperature coefficient adjustment layer 410 and a mass compensation layer 420 stacked sequentially on the piezoelectric layer 300. The electrode thickness of the temperature coefficient adjustment layer 410 is set to h1, and the electrode density of the temperature coefficient adjustment layer 410 is set to ρ1. The electrode thickness of the mass compensation layer 420 is set to h2, and the electrode density of the mass compensation layer 420 is set to ρ2, satisfying 112 / 574≤h1ρ1 / (h1ρ1+h2ρ2)≤64 / 109, and ρ1>3ρ2.

[0069] The difference is that the support substrate 100 in this embodiment includes a high-velocity substrate 110 disposed below the low-velocity layer 200. A trapping material layer 120 is disposed between the high-velocity substrate 110 and the low-velocity layer 200. The high-velocity substrate 110, the trapping material layer 120, and the low-velocity layer 200 are stacked sequentially to support the piezoelectric layer 300. The high-velocity substrate 110, the trapping material layer 120, the low-velocity layer 200, and the piezoelectric layer 300 constitute a multilayer piezoelectric substrate, as detailed in [link to documentation]. Figure 4 .

[0070] Optionally, the piezoelectric layer 300 is made of lithium niobate with an Euler angle of (0°, Ω, 0°) and 90°≤Ω≤160°; the temperature coefficient adjustment layer 410 is one or more of copper, platinum, tungsten, etc., which have relatively high density; the mass compensation layer 420 is made of aluminum; the low-velocity layer 200 is one or more of silicon dioxide, glass, silicon oxynitride, tantalum oxide, or a compound with fluorine, carbon, or boron added to silicon dioxide as the main component; and the trapping material layer 120 is formed of one or more of amorphous silicon, polycrystalline silicon, amorphous germanium, polycrystalline germanium.

[0071] This embodiment uses the following parameters as examples: the temperature coefficient adjustment layer 410 is a platinum electrode; the mass compensation layer 420 is an aluminum electrode; the high-velocity substrate 110 is silicon; the trapping material layer 120 is polycrystalline silicon with a thickness of 1 μm; the low-velocity layer 200 is silicon dioxide with a thickness of 300 nm; the piezoelectric layer 300 is lithium niobate cut at 32°Y with Euler angles of (0°, 122°, 0°) and a thickness of 300 nm; and the wavelength λ of the elastic wave is 2 μm.

[0072] Figure 5A schematic diagram is shown illustrating the variation of TCFr and TCFa of the elastic wave device provided in this embodiment with the mass ratio of the temperature coefficient adjustment layer 410. The mass ratio of the temperature coefficient adjustment layer 410 is defined as the proportion of the mass of the temperature coefficient adjustment layer 410 to the total mass of the electrode, i.e., h1ρ1 / (h1ρ1+h2ρ2). As can be seen from the curve, at the resonant frequency of the elastic wave device, both TCFa and TCFr gradually increase with the increase of the mass ratio of the temperature coefficient adjustment layer 410; while when 112 / 574≤h1ρ1 / (h1ρ1+h2ρ2)≤64 / 109, ΔTCF remains at a relatively small level, indicating better performance.

[0073] Example 3:

[0074] Based on Embodiment 1 and Embodiment 2, this embodiment provides a filter including a series arm resonator and a parallel arm resonator, at least one of the series arm resonator and the parallel arm resonator including the above-mentioned elastic wave device, thereby ensuring the stable performance of the filter.

[0075] Example 4:

[0076] Based on Embodiment 3, this embodiment provides a multiplexer, including an antenna terminal connected to an antenna and multiple filter devices connected to the antenna terminal, wherein at least one filter device includes the aforementioned filter, thereby ensuring the stable performance of the multiplexer.

[0077] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. An elastic wave device, characterized in that, It includes a support substrate (100), a low-velocity layer (200), a piezoelectric layer (300), and an interdigital transducer (400), wherein: The low-velocity layer (200) is disposed on the support substrate (100); The piezoelectric layer (300) is disposed on the low-velocity layer (200), and the thickness of the piezoelectric layer (300) is less than λ, where λ is the wavelength of the elastic wave; The interdigital transducer (400) is disposed on the piezoelectric layer (300). The interdigital transducer (400) includes a temperature coefficient adjustment layer (410) and a mass compensation layer (420) stacked sequentially on the piezoelectric layer (300). The electrode thickness of the temperature coefficient adjustment layer (410) is set to h1, the electrode density of the temperature coefficient adjustment layer (410) is ρ1, the electrode thickness of the mass compensation layer (420) is h2, and the electrode density of the mass compensation layer (420) is ρ2, satisfying 112 / 574≤h1ρ1 / (h1ρ1+h2ρ2)≤64 / 109, and ρ1>3ρ2.

2. The elastic wave device according to claim 1, characterized in that, The interdigital transducer (400) includes a first electrode finger (401), a second electrode finger (402), a first busbar (403), and a second busbar (404). A plurality of the first electrode fingers (401) and the second electrode fingers (402) are arranged alternately and parallel to each other in the elastic wave propagation direction of the interdigital transducer (400). The first busbar (403) and the second busbar (404) are distributed on both sides of the first electrode finger (401) and the second electrode finger (402). The first end of each of the first electrode fingers (401) is connected to the first bus bar (403), the first end of each of the second electrode fingers (402) is disconnected from the first bus bar (403), the second end of each of the second electrode fingers (402) is connected to the second bus bar (404), the second end of each of the first electrode fingers (401) is disconnected from the second bus bar (404), and the spacing between two adjacent first bus bars (403) and the spacing between two adjacent second bus bars (404) are both λ.

3. The elastic wave device according to claim 1, characterized in that, A reflector (500) is also provided on the piezoelectric layer (300) and on both sides of the interdigital transducer (400) along the elastic wave propagation direction. The reflector (500) includes a third electrode finger (501) and a third bus bar (502). A plurality of the third electrode fingers (501) are arranged in parallel at intervals along the elastic wave propagation direction of the interdigital transducer (400). Two third bus bars (502) are distributed at both ends of the third electrode fingers (501), and the end of each third electrode finger (501) is connected to the corresponding third bus bar (502).

4. The elastic wave device according to claim 1, characterized in that, The piezoelectric layer (300) is made of lithium tantalate with an Euler angle of (0°, Φ, 0°) and 100°≤Φ≤150°; or the piezoelectric layer (300) is made of lithium niobate with an Euler angle of (0°, Ω, 0°) and 90°≤Ω≤160°.

5. The elastic wave device according to claim 1, characterized in that, The support substrate (100) includes a high-velocity substrate (110) disposed below the low-velocity layer (200), the high-velocity substrate (110) being directly attached to the low-velocity layer (200); or, a trapping material layer (120) is disposed between the high-velocity substrate (110) and the low-velocity layer (200).

6. The elastic wave device according to claim 5, characterized in that, The material of the trapping material layer (120) includes at least one of amorphous silicon, polycrystalline silicon, amorphous germanium, and polycrystalline germanium.

7. The elastic wave device according to claim 1, characterized in that, The material of the low-velocity layer (200) includes at least one of silicon dioxide, silicon oxynitride, tantalum oxide, or a compound in which fluorine, carbon, or boron has been added to silicon dioxide.

8. The elastic wave device according to claim 1, characterized in that, The temperature coefficient adjustment layer (410) is made of at least one of copper, platinum, and tungsten; the mass compensation layer (420) is made of aluminum.

9. A filter, characterized in that, It includes a series arm resonator and a parallel arm resonator, wherein the series arm resonator and / or the parallel arm resonator includes the elastic wave device according to any one of claims 1-8.

10. A multiplexer, characterized in that, Includes the filter as described in claim 9.

Images