Elastic wave device, ladder filter, wave divider, and communication device

Abstract

An elastic wave element with excellent electrical characteristics is achieved. The elastic wave resonator comprises: a piezoelectric substrate including a piezoelectric element and an IDT electrode, a support substrate, and a first intermediate layer. In the first intermediate layer, the atomic ratio of metal elements is greater than that of metal elements in the piezoelectric element, and the atomic ratio of oxygen is less than that of oxygen in the piezoelectric element. The thickness of the piezoelectric element is less than 5 times the maximum spacing of the electrode fingers of the IDT electrode.

Description

Technical Field

[0001] This disclosure relates to elastic wave elements, etc. Background Technology

[0002] Previously, elastic wave elements with electrodes disposed on a substrate formed by bonding a support substrate and a piezoelectric substrate were known. Such elastic wave elements were used, for example, as bandpass filters in communication devices. In Patent Document 1, elastic wave elements using lithium niobate or lithium tantalate as piezoelectric substrates and silicon, quartz, ceramic, etc. as support substrates were known.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Publication No. 2006-319679 Summary of the Invention

[0006] One aspect of the elastic wave element disclosed herein includes: a piezoelectric substrate comprising a piezoelectric body and an IDT electrode having a plurality of electrode fingers arranged at predetermined intervals on the piezoelectric body; a support substrate located on the opposite side of the IDT electrode relative to the piezoelectric substrate; and a first intermediate layer located between the piezoelectric substrate and the support substrate; wherein the first intermediate layer comprises elements identical to those of the piezoelectric body, the atomic ratio of metal elements being greater than that of metal elements in the piezoelectric body, and the atomic ratio of oxygen being less than that of oxygen in the piezoelectric body; and the thickness of the piezoelectric body being less than 5 times the maximum of the predetermined intervals. Attached Figure Description

[0007] Figure 1 This is a schematic top view of an elastic wave resonator according to Embodiment 1 of this disclosure.

[0008] Figure 2 This is a schematic cross-sectional view of the aforementioned elastic wave resonator, along... Figure 1 A cross-sectional view along line AA in the diagram.

[0009] Figure 3 This is a TEM image representing an example of the aforementioned elastic wave resonator.

[0010] Figure 4 This is a diagram illustrating the effect of the aforementioned elastic wave resonator.

[0011] Figure 5 This is a graph showing the relationship between the thickness of the piezoelectric element of the aforementioned elastic wave resonator and the generation of stray particles in the stopband when the aforementioned elastic wave resonator is used as a filter.

[0012] Figure 6 This is a graph showing the relationship between the thickness of the piezoelectric material and the maximum phase of the elastic wave resonator.

[0013] Figure 7 This is a graph showing the relationship between the intensity of the surface treatment and the thickness of the first intermediate layer in an elastic wave resonator manufactured under specified conditions.

[0014] Figure 8 This is a schematic diagram illustrating a communication device according to one embodiment of the present disclosure.

[0015] Figure 9 This is a circuit diagram illustrating one embodiment of the divider of this disclosure. Detailed Implementation

[0016] Embodiments of the present invention will now be described with reference to the accompanying drawings. Furthermore, the drawings used in the following description are schematic diagrams and do not strictly represent the dimensional proportions of the components in the drawings.

[0017] <Structure of a Resonator>

[0018] The elastic wave filter of this embodiment includes at least one elastic wave resonator. For example, the elastic wave filter can be configured as a trapezoidal filter by connecting multiple elastic wave resonators in a trapezoidal shape. The elastic wave filter of this embodiment may also include multiple elastic wave resonators arranged side by side in a direction orthogonal to the propagation direction of the elastic wave in each elastic wave resonator.

[0019] The following is for reference Figure 1 as well as Figure 2 The elastic wave resonator 4 of this embodiment will be described in more detail. Figure 1 This is a schematic top view of the elastic wave resonator 4 in this embodiment. Figure 2 This is a schematic cross-sectional view of the elastic wave resonator 4, along... Figure 1 A cross-sectional view along line AA. Additionally, in this specification, the propagation direction TD of the elastic wave in the elastic wave resonator 4 is defined as including... Figure 1 In the top view of the elastic wave resonator 4, it is positioned vertically towards the plane of the paper, including... Figure 2 In the cross-sectional view of the elastic wave resonator 4, it is positioned in the left-right direction facing the plane of the paper. Furthermore, in this specification, including... Figure 2 In the cross-sectional view of the elastic wave resonator 4, for the sake of simplicity, only the components in the cross-section are shown, and the components further inside the cross-section are omitted. Furthermore, the elastic wave resonator is an example of an elastic wave element.

[0020] like Figure 1 as well as Figure 2As shown, the elastic wave resonator 4 of this embodiment includes a piezoelectric substrate 5. The piezoelectric substrate 5 includes a piezoelectric body 6 and an IDT electrode 8 on the piezoelectric body 6. Additionally, this specification includes... Figure 2 In the cross-sectional view of the elastic wave resonator 4, the IDT electrode 8 is shown facing upward relative to the piezoelectric body 6 toward the paper.

[0021] The piezoelectric element 6 is made of a piezoelectric material, such as a single crystal of lithium tantalate or lithium niobate. The piezoelectric element 6 contains metallic and oxygen elements.

[0022] In the elastic wave resonator 4, an elastic wave propagating in the piezoelectric body 6 along the propagation direction TD is excited by applying a voltage to the conductive layer including the IDT electrode 8 (described later). In this embodiment, as... Figure 2 As shown, the piezoelectric element 6 can have a constant thickness. However, in this specification, "constant thickness" does not necessarily mean a strictly constant thickness, but rather allows for some variation within a range that does not significantly affect the characteristics of the elastic wave propagating in the piezoelectric element 6. To reduce electrical signal loss and characteristic changes due to temperature variations, the thickness of the piezoelectric element 6 is preferably relatively thin. In this embodiment, the thickness of the piezoelectric element 6 is configured to be less than 5 times the maximum spacing among the spacings of the electrode fingers 14 of the IDT electrode 8 (described later). Furthermore, the thickness of the piezoelectric element 6 is less than 2.5 times the wavelength of the elastic wave excited by the elastic wave resonator 4.

[0023] The IDT electrode 8 includes a pair of comb-tooth electrodes 10. Additionally, in this specification, [the following is mentioned:] including... Figure 1 In the top view of the elastic wave resonator 4, a comb electrode 10 is shaded to improve visibility. The comb electrode 10 includes, for example, a busbar 12; a plurality of electrode fingers 14 extending from the busbar 12 to each other; and a plurality of dummy electrodes 16 located between the electrode fingers 14 and protruding from the busbar 12. In a pair of comb electrodes 10, the electrode fingers 14 are configured to mesh with each other.

[0024] Busbar 12 has a substantially constant width and is formed approximately along the propagation direction TD. Furthermore, a pair of busbars 12 are positioned opposite each other in a direction substantially orthogonal to the propagation direction TD. Additionally, the width of the busbar 12 can be varied, or it can be formed at an angle relative to the propagation direction TD, without significantly affecting the elastic wave propagating in the piezoelectric material 6.

[0025] Each electrode finger 14 is formed into an elongated shape approximately along the width direction of the busbar 12. In each comb electrode 10, multiple electrode fingers 14 are arranged along the propagation direction TD. Furthermore, electrode fingers 14 extending from one busbar 12 and electrode fingers 14 extending from another busbar 12 are alternately arranged in the propagation direction TD.

[0026] The number of electrodes 14 is not limited to Figure 1 The number of roots shown can be appropriately designed according to the required characteristics of the elastic wave resonator 4. Furthermore, as... Figure 1 As shown, the length of each electrode finger 14 can be approximately constant, or it can vary in length depending on its position in the propagation direction TD, implemented as a so-called apodization. Additionally, a portion of the electrode fingers 14 within a portion of the IDT electrode 8 can also be "divided". In other words, the IDT electrode 8 can include a region in which no portion of the electrode fingers 14 is formed.

[0027] Each dummy electrode 16 protrudes approximately along the width direction of the busbar 12. Furthermore, the distal ends of a dummy electrode 16 protruding from one busbar 12 and an electrode finger 14 extending from another busbar 12 are positioned opposite each other with a gap in a direction orthogonal to the propagation direction TD. Alternatively, the elastic wave resonator 4 may not include the dummy electrodes 16.

[0028] The elastic wave resonator 4 also includes a pair of reflectors 18, which are located at opposite ends of the propagation direction TD on the piezoelectric element 6, relative to the electrode fingers 14. Each reflector 18 includes a plurality of strip electrodes 22 extending from a pair of opposing busbars 20. The reflectors 18 can be electrically suspended, or they can be given a reference potential. Furthermore, the IDT electrodes 8 and reflectors 18 can be in the same layer or contained within a conductive layer. The IDT electrodes 8 and reflectors 18 are formed of a metallic material, such as an alloy primarily composed of Al.

[0029] like Figure 2 As shown, the elastic wave resonator 4 also includes a support substrate 26, which supports the piezoelectric substrate 5 while located on the opposite side of the IDT electrode 8. In this embodiment, the support substrate 26 has a sufficiently small influence on the characteristics of the elastic wave propagating in the piezoelectric body 6. Therefore, the material and size of the support substrate 26 can be appropriately designed. For example, the support substrate 26 may include an insulating material and may include resin or ceramic (e.g., sapphire). Furthermore, the support substrate 26 may also be made of Si. The thickness of the support substrate 26 may, for example, be thicker than the thickness of the piezoelectric body 6. To further reduce the influence of temperature changes on the elastic wave characteristics, the support substrate 26 may be formed of a material with a lower coefficient of linear expansion than that of the piezoelectric body 6.

[0030] like Figure 2As shown, the elastic wave resonator 4 has a first intermediate layer 30 and a second intermediate layer 32 between the piezoelectric substrate 5 and the support substrate 26. More specifically, the elastic wave resonator 4 is constructed by stacking the piezoelectric substrate 5, the first intermediate layer 30, the second intermediate layer 32, and the support substrate 26 in the thickness direction of the elastic wave resonator 4.

[0031] As described below, the first intermediate layer 30 is derived from an activated layer produced during the bonding of the piezoelectric substrate 5 and the support substrate 26 by performing an activation treatment to activate the surface of the piezoelectric element 6 of the piezoelectric substrate 5. Therefore, the constituent elements of the first intermediate layer 30 are the same as or substantially the same as those of the piezoelectric element 6. "The constituent elements of the first intermediate layer 30 are substantially the same as those of the piezoelectric element 6" means that the first intermediate layer 30 contains a small amount of elements other than those of the piezoelectric element 6 as impurities. In the first intermediate layer 30, the atomic ratio of metal elements is greater than that of metal elements in the piezoelectric element 6, and the atomic ratio of oxygen is less than that of oxygen in the piezoelectric element. Consequently, the resistivity of the first intermediate layer 30 is lower than that of the piezoelectric element 6. For example, when the piezoelectric element 6 is composed of lithium tantalate, the atomic ratio of tantalum in the first intermediate layer 30 is greater than that of tantalum in the piezoelectric element 6, and the atomic ratio of oxygen in the first intermediate layer 30 is less than that of oxygen in the piezoelectric element 6, resulting in a lower resistivity for the first intermediate layer 30 than that of the piezoelectric element 6.

[0032] The second intermediate layer 32 is an activated layer generated during the bonding of the piezoelectric substrate 5 and the support substrate 26 by performing an activation treatment to activate the surface of the support substrate 26. Therefore, the constituent elements of the second intermediate layer 32 are the same as or substantially the same as those of the support substrate 26. "The constituent elements of the second intermediate layer 32 are substantially the same as those of the support substrate 26" means that the second intermediate layer 32 contains a small amount of elements other than those of the support substrate 26 as impurities. The thickness of the second intermediate layer 32 is greater than the thickness of the first intermediate layer 30. This improves the bonding strength between the piezoelectric element 6 and the support substrate 26.

[0033] The activation process for forming the first intermediate layer 30 and the second intermediate layer 32 can use conventional room temperature bonding apparatus (e.g., plasma processing apparatus) for bonding wafers. The first intermediate layer 30 and the second intermediate layer 32 become amorphous layers activated by the room temperature bonding apparatus.

[0034] Figure 3 This is a TEM image showing an example of the bonding surface of the piezoelectric element 6 and the support substrate 26 in an elastic wave resonator 4 manufactured by surface treating the piezoelectric element 6 and the support substrate 26 and bonding the piezoelectric element 6 and the support substrate 26.

[0035] exist Figure 3In the example shown, a first intermediate layer 30 with a thickness of approximately 1.2 nm and a second intermediate layer 32 with a thickness of approximately 3.0 nm are formed between the piezoelectric element 6 and the supporting substrate 26. Figure 3 EDS analysis of the elastic wave resonator 4 shown shows that the piezoelectric element 6 and the first intermediate layer 30 have the same constituent elements. Furthermore, in the EDS measurement of the piezoelectric element 6, the atomic ratio of oxygen is 72.78% and the atomic ratio of tantalum is 23.98%; in contrast, in the EDS measurement of the first intermediate layer, the atomic ratio of oxygen is 47.44% and the atomic ratio of tantalum is 26.76%. From these results, it can be concluded that the first intermediate layer 30 is a low-resistivity layer with a lower resistivity than the piezoelectric element 6.

[0036] Here, in the elastic wave resonator, to reduce signal strength loss and improve the low-temperature characteristics of the elastic wave resonator, it is desirable to reduce the thickness of the piezoelectric element. The inventors have discovered that when the thickness of the piezoelectric element is reduced, the resonant characteristics of the elastic wave resonator are affected by the interface state between the piezoelectric element and the supporting substrate. Furthermore, the inventors have discovered that by controlling the interface state between the piezoelectric element and the supporting substrate, the influence of the interface state on the resonant characteristics of the elastic wave resonator can be reduced, thereby improving the electrical characteristics of filters using elastic wave resonators.

[0037] Specifically, in the elastic wave resonator 4 of this embodiment, when the thickness of the piezoelectric body 6 is less than 5 times the maximum spacing among the electrode fingers 14, the aforementioned first intermediate layer 30 is formed between the piezoelectric body 6 and the support substrate 26. The inventors have discovered that, with this structure, when the stopband of the parallel resonator of the elastic wave resonator 4 of this embodiment is located within the passband of the filter, the possibility of spurious emissions in the stopband can be reduced.

[0038] Figure 4 This is a diagram illustrating the effect of the elastic wave resonator 4. Figure 4 It is a graph simulating the characteristics of a filter assuming that there are layers with resistivity of 2.5 Ωcm, 0.14 Ωcm and 0.007 Ωcm and thickness of 2 nm between the piezoelectric body 6 and the support substrate 26. Figure 4 The horizontal axis of each graph shows frequency, and the vertical axis represents group delay. Additionally, for easy reference, the data for resistivity of 0.14 Ωcm is also shown in the graphs for resistivity of 2.5 Ωcm and 0.007 Ωcm.

[0039] like Figure 4As shown, when the resistivity is 2.5 Ωcm, which is close to the value of piezoelectric material 6, more fluctuations occur compared to the case where the resistivity is 0.14 Ωcm. Furthermore, even when there is a layer with a resistivity close to 0.007 Ωcm between piezoelectric material 6 and support substrate 26, more fluctuations occur compared to the case where there is a layer with a resistivity of 0.14 Ωcm.

[0040] Conversely, by having a layer with a resistivity of 0.14 Ωcm that is lower than that of the piezoelectric material 6 between the piezoelectric material 6 and the support substrate 26, the generation of fluctuations can be reduced. In other words, by forming a layer with a resistance lower than that of the piezoelectric material 6 and higher than that of a metal between the piezoelectric material 6 and the support substrate 26, the generation of fluctuations in the elastic wave resonator 4 can be reduced.

[0041] Figure 5 This is a graph showing the relationship between the thickness of the piezoelectric element 6 of the elastic wave resonator 4 and the generation of spurious signals in the stopband when the elastic wave resonator 4 is used as a filter. Figure 5 The figures shown in the middle and upper parts depict the case where the thickness of the piezoelectric element 6 is 4.64 times the maximum spacing of the electrode fingers 14. Figure 5 The figures shown in the middle and lower sections depict the case where the thickness of the piezoelectric element 6 is 5.28 times the maximum spacing of the electrode fingers 14. Furthermore, Figure 5 In the graphs shown, the horizontal axis represents frequency, and the vertical axis represents impedance on the left and phase on the right. Furthermore, in... Figure 5 The diagram also illustrates data assuming that there are layers with resistivity of 2.5 Ωcm, 0.14 Ωcm, and 0.007 Ωcm and thickness of 2 nm between the piezoelectric body 6 and the support substrate 26.

[0042] like Figure 5 As shown, it can be seen that when the thickness of the piezoelectric body 6 is 4.64 times the maximum spacing of the electrode fingers 14, and when there is a layer with a resistivity of 0.14 Ωcm between the piezoelectric body 6 and the support substrate 26 (which has a lower resistance than the piezoelectric body 6), the possibility of stray particles being generated in the stopband is reduced. On the other hand, it can be seen that when the thickness of the piezoelectric body 6 is 4.64 times the maximum spacing of the electrode fingers 14, and when there is a layer with a resistivity of 2.5 Ωcm or 0.007 Ωcm between the piezoelectric body 6 and the support substrate 26, stray particles are generated in the stopband. Furthermore, it can be seen that when the thickness of the piezoelectric body 6 is 5.28 times the maximum spacing of the electrode fingers 14, stray particles are generated in the stopband in all figures.

[0043] The resistivity of the first intermediate layer 30 of the elastic wave resonator 4 in this embodiment is around 0.14 Ωcm. In other words, the layer with a resistivity of 0.14 Ωcm located between the piezoelectric body 6 and the support substrate 26 corresponds to the first intermediate layer 30 of this embodiment. Therefore, by having the first intermediate layer 30 between the piezoelectric body 6 and the support substrate 26, the characteristics of exciting elastic waves in the piezoelectric body 6 are improved.

[0044] Figure 6 This is a graph showing the relationship between the thickness of the piezoelectric element 6 and the maximum phase of the elastic wave resonator. (See figure.) Figure 6 As shown, the thickness of the piezoelectric material 6 is equal to the wavelength of the elastic wave excited in the piezoelectric substrate 5. Figure 6 When the wavelength of the elastic wave excited by the piezoelectric substrate 5 is less than 0.8 times (in other words, less than 1.6 times the maximum spacing of the electrode fingers 14), the characteristics of the elastic wave resonator deteriorate. Conversely, by making the thickness of the piezoelectric body 6 0.8 times longer than the wavelength of the elastic wave excited by the piezoelectric substrate 5 (in other words, more than 1.6 times the maximum spacing of the electrode fingers 14), the filtering characteristics of the elastic wave resonator can be improved.

[0045] Figure 7 This is a graph showing the relationship between the intensity of the surface treatment used to form the first intermediate layer and the thickness of the first intermediate layer in an elastic wave resonator manufactured under specified conditions. Figure 7 In the figure, the curves, marked with the same symbols, represent data under the same conditions of irradiation with an ion beam, except for the intensity of the ion beam.

[0046] like Figure 7 As shown, the thickness of the first intermediate layer increases with the increase of ion beam intensity. Furthermore, the characteristics of each fabricated elastic wave resonator were investigated, and the results showed that the device characteristics were good when the thickness of the first intermediate layer was 1.5–1.9 nm (i.e., 1.5 nm or more but less than 1.9 nm). On the other hand, the filtering characteristics fluctuated when the thickness of the first intermediate layer was less than 1.5 nm, and also fluctuated when the thickness of the first intermediate layer was greater than 1.9 nm, resulting in poor device characteristics.

[0047] <Overview of Communication Devices and Demultiplexer Structure>

[0048] Figure 8 This is a block diagram showing the main parts of a communication device 40 according to an embodiment of the present disclosure. The communication device 40 uses radio waves for wireless communication. The demultiplexer 42 has the function of demultiplexing a signal at a transmission frequency and a signal at a reception frequency in the communication device 40.

[0049] In communication device 40, the transmit information signal TIS, which includes the information to be transmitted, is modulated and frequency-boosted (converted into a high-frequency signal with a carrier frequency) by RF-IC 44, thus becoming the transmit signal TS. The transmit signal TS passes through bandpass filter 46 to remove unnecessary components outside the transmit passband, and is amplified by amplifier 48 before being input to demultiplexer 42. Demultiplexer 42 removes unnecessary components outside the transmit passband from the input transmit signal TS and outputs it to antenna 50. Antenna 50 converts the input electrical signal (transmit signal TS) into a wireless signal and transmits it.

[0050] In the communication device 40, the wireless signal received through the antenna 50 is converted into an electrical signal (received signal RS) and input to the demultiplexer 42. The demultiplexer 42 removes unnecessary components outside the passband from the input received signal RS and outputs it to the amplifier 52. The output received signal RS is amplified by the amplifier 52 and then passes through the bandpass filter 54 to remove unnecessary components outside the passband. Then, the received signal RS is converted into a received information signal RIS by the RF-IC 44 for frequency reduction and demodulation.

[0051] The Transmit Information Signal (TIS) and Receive Information Signal (RIS) can be low-frequency signals (baseband signals) containing appropriate information, such as analog or digitized audio signals. The wireless signal passband can conform to various standards such as the Universal Mobile Telecommunications System (UMTS). Modulation methods can be phase modulation, amplitude modulation, frequency modulation, or any combination of two or more of these.

[0052] Figure 9 This is a circuit diagram illustrating the structure of a demultiplexer 42 according to one embodiment of the present disclosure. The demultiplexer 42 is... Figure 8 The demultiplexer 42 used in the communication device 40.

[0053] like Figure 9As shown, the transmit filter 56 includes series resonators S1 to S3 and parallel resonators P1 to P3. The demultiplexer 42 mainly consists of an antenna terminal 58, a transmit terminal 60, a receive terminal 62, a transmit filter 56 disposed between the antenna terminal 58 and the transmit terminal 60, and a receive filter 64 disposed between the antenna terminal 58 and the receive terminal 62. The transmit signal TS from the amplifier 48 is input to the transmit terminal 60. The transmit signal TS input to the transmit terminal 60 is filtered in the transmit filter 56 to remove unnecessary components outside the passband used for transmission (in other words, filtering), and then output to the antenna terminal 58. In addition, the receive signal RS is input from the antenna 50 to the antenna terminal 58. The receive filter 64 removes unnecessary components outside the passband used for reception (in other words, filtering), and then output to the receive terminal 62.

[0054] The transmitting filter 56 is, for example, a trapezoidal elastic wave filter. Specifically, the transmitting filter 56 has: three series resonators S1, S2, and S3 connected in series between its input and output sides; and three parallel resonators P1, P2, and P3 disposed between the series arm and the reference potential section G; the series arm is wiring for connecting the series resonators to each other. That is, the transmitting filter 56 is a trapezoidal filter with a three-stage structure. However, in the transmitting filter 56, the number of stages of the trapezoidal filter is arbitrary.

[0055] An inductor L is provided between the parallel resonators P1 to P3 and the reference potential section G. By setting the inductance of the inductor L to a specified value, attenuation poles are formed outside the passband of the transmitted signal, thereby increasing attenuation outside the frequency band. The multiple series resonators S1 to S3 and the multiple parallel resonators P1 to P3 are each composed of elastic wave resonators.

[0056] The receiving filter 64 includes, for example, a multi-mode elastic wave filter 66 and an auxiliary resonator 68 connected in series with its input side. In this embodiment, multi-mode includes dual-mode. The multi-mode elastic wave filter 66 has a balanced-to-unbalanced conversion function, and the receiving filter 64 is connected to the two receiving terminals 62 that output a balanced signal. The receiving filter 64 is not limited to being composed of a multi-mode elastic wave filter 66; it can be composed of a trapezoidal filter, or it can be a filter without a balanced-to-unbalanced conversion function.

[0057] An impedance matching circuit, consisting of an inductor or the like, can be inserted between the connection point between the transmitting filter 56, the receiving filter 64, and the antenna terminal 58 and the ground potential section G.

[0058] The elastic wave filters in the above embodiments are, for example, made of... Figure 8The elastic wave element is constructed from a ladder-shaped filter circuit of at least one of the transmitting filter 56 or the receiving filter 64 in the shown splitter 42. When either the transmitting filter 56 or the receiving filter 64 is an elastic wave filter according to the above embodiment, all or at least a portion of the elastic wave resonators included in the filter are the aforementioned elastic wave resonators 4. In the elastic wave filters of each of the above embodiments, the stopband of at least one parallel resonator is located within the passband of the ladder-shaped filter.

[0059] By employing a demultiplexer 42 equipped with such a transmit filter 56 or receive filter 64, the filter characteristics of the communication device 40 can be improved.

[0060] This disclosure is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims; embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included within the technical scope of this disclosure.

[0061] Explanation of reference numerals in the attached figures

[0062] 4. Elastic wave resonator (elastic wave element)

[0063] 5. Piezoelectric substrate

[0064] 6. Piezoelectric elements

[0065] 8 IDT electrodes

[0066] 14 Electrode fingers

[0067] 26 Supporting substrate

[0068] 30 First intermediate layer 32 Second intermediate layer 40 Communication device 42 Demultiplexer 44 RF-IC

[0069] 50 antennas

[0070] 56 Transmit filter 58 Antenna terminal 64 Receive filter.

Claims

1. Elastic wave element, possessing: A piezoelectric substrate includes a piezoelectric body and an IDT electrode, wherein the IDT electrode has a plurality of electrode fingers arranged on the piezoelectric body at a predetermined interval; A support substrate is located on the opposite side of the IDT electrode relative to the piezoelectric substrate; and, The first intermediate layer is located between the piezoelectric substrate and the supporting substrate; In the first intermediate layer: The constituent elements are the same as those of the piezoelectric material. The atomic ratio of the metal elements is greater than that of the metal elements in the piezoelectric body, and the atomic ratio of oxygen is less than that of oxygen in the piezoelectric body. The thickness of the piezoelectric element is less than 5 times the maximum spacing among the specified spacings; Between the first intermediate layer and the support substrate, there is a second intermediate layer formed of the same constituent elements as the support substrate; The thickness of the second intermediate layer is greater than the thickness of the first intermediate layer.

2. The elastic wave element according to claim 1, wherein the thickness of the piezoelectric element is longer than 1.6 times the length of the specified spacing.

3. The elastic wave element according to claim 1 or 2, wherein the thickness of the first intermediate layer is 1.5~1.9 nm.

4. A trapezoidal filter comprising at least one elastic wave element according to any one of claims 1 to 3; The stopband of at least one parallel resonator is located within the passband of the trapezoidal filter.

5. Demultiplexer, featuring: Antenna terminals; a transmit filter to filter a transmit signal and output to the antenna terminal; and, A receiving filter is used to filter the received signal from the antenna terminal. At least one of the transmitting filter and the receiving filter includes: the trapezoidal filter according to claim 4.

6. A communication device, having: antenna; According to claim 5, the antenna terminal is connected to the antenna; and, The IC is connected to the transmitting filter and the receiving filter.

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