Acoustic wave device and module using the same

Abstract

To provide an acoustic wave device having good temperature characteristics and further suppressed spurious emissions, and a method for manufacturing the same.SOLUTION: An acoustic wave device includes a support substrate, a medium layer formed on the support substrate, a silicon nitride layer formed on the medium layer, a piezoelectric substrate formed on the silicon nitride layer, and a resonator including an interdigital transducer (IDT) electrode formed on the piezoelectric substrate, and the medium layer has a first acoustic impedance region in a stripe shape having a longitudinal direction and a lateral direction, and a second acoustic impedance region having an acoustic impedance different from that of the first acoustic impedance region in a stripe shape having a longitudinal direction and a lateral direction and arranged alternately with the first acoustic impedance region, and a total thickness of the silicon nitride layer and the piezoelectric substrate is 1.0 λ or less, where λ is the wavelength of an acoustic wave determined by the electrode pitch of the IDT electrode.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to an acoustic wave device and a module using the acoustic wave device, and more particularly to a surface acoustic wave device using SH waves, such as a filter, a duplexer, or a multiplexer. [Background technology]

[0002] 2. Description of the Related Art In high-frequency communication systems for mobile communication terminals, such as smartphones, high-frequency filters and the like are used to remove unnecessary signals outside the frequency band used for communication.

[0003] Acoustic wave devices having a surface acoustic wave (SAW) element, etc., are used in high frequency filters, etc. The SAW element is an element in which an IDT (Interdigital Transducer) having a pair of comb-shaped electrodes is formed on a piezoelectric substrate.

[0004] For example, a surface acoustic wave device is manufactured as follows. First, a multilayer film substrate is created by bonding a piezoelectric substrate that propagates acoustic waves to a support substrate that has a smaller thermal expansion coefficient than the piezoelectric substrate. Next, a large number of IDT electrodes are formed on the multilayer film substrate using photolithography technology, and the substrate is then cut to a specified size by dicing to form a surface acoustic wave device. In this manufacturing method, by using a multilayer film substrate, changes in size of the piezoelectric substrate when the temperature changes are suppressed by the support substrate, and the frequency characteristics of the acoustic wave device are stabilized.

[0005] For example, Patent Document 1 and other documents disclose that in order to improve the temperature characteristics of an acoustic wave device, a support substrate such as a sapphire substrate that has a high Young's modulus and a small linear expansion coefficient is bonded to a piezoelectric substrate to suppress expansion and contraction due to temperature changes. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2009-278610 A Summary of the Invention [Problem to be solved by the invention]

[0007] As disclosed in Patent Document 1, in order to improve the temperature characteristics of an acoustic wave device, it is known to bond a support substrate such as a sapphire substrate, which has a high Young's modulus and a small linear expansion coefficient, to a piezoelectric substrate to suppress expansion and contraction due to temperature changes. However, resonators using such a support substrate have spurious emissions, especially on the high frequency side, and have poor filter characteristics.

[0008] The present disclosure has been made to solve the above-mentioned problems. An object of the present disclosure is to provide an acoustic wave device having good temperature characteristics and further suppressing spurious emissions, and a module using the acoustic wave device. [Means for solving the problem]

[0009] The acoustic wave device according to the present disclosure comprises: A support substrate; a medium layer formed on the support substrate; a silicon nitride layer formed on the medium layer; a piezoelectric substrate formed on the silicon nitride layer; a resonator including an IDT electrode formed on the piezoelectric substrate; Equipped with The medium layer is A first acoustic impedance region having a stripe shape with a longitudinal direction and a lateral direction; a second acoustic impedance region having an acoustic impedance different from that of the first acoustic impedance region, the second acoustic impedance region being striped and having a longitudinal direction and a transverse direction and arranged alternately with the first acoustic impedance region; The total thickness of the silicon nitride layer and the piezoelectric substrate was set to 1.0λ or less, where λ is the wavelength of an elastic wave determined by the electrode pitch of the IDT electrodes.

[0010] According to one embodiment of the present disclosure, the total thickness of the medium layer, the silicon nitride layer and the piezoelectric substrate is 1.0λ or less, where λ is the wavelength of an elastic wave determined by the electrode pitch of the IDT electrodes.

[0011] In one aspect of the present disclosure, the silicon nitride layer has a thickness greater than a thickness of the piezoelectric substrate.

[0012] In one embodiment of the present disclosure, the total thickness of the silicon nitride layer and the piezoelectric substrate is 0.7λ or less, where λ is the wavelength of an elastic wave determined by the electrode pitch of the IDT electrodes.

[0013] It is an aspect of the present disclosure to further include a semiconductor layer between the silicon nitride layer and the piezoelectric substrate.

[0014] In one embodiment of the present disclosure, the longitudinal direction of the first acoustic impedance region and the second acoustic impedance region is arranged in the same direction as the longitudinal direction of electrode fingers of the IDT electrode.

[0015] According to one aspect of the present disclosure, the first acoustic impedance region and the second acoustic impedance region are arranged at a pitch different from an electrode pitch of the IDT electrode.

[0016] In one embodiment of the present disclosure, the thickness of the piezoelectric substrate is 0.1λ or more and 0.3λ or less, where λ is the wavelength of an elastic wave determined by the electrode pitch of the IDT electrodes.

[0017] In one embodiment of the present disclosure, the thickness of the medium layer is 0.1λ or more and 0.5λ or less, where λ is the wavelength of an acoustic wave determined by the electrode pitch of the IDT electrodes.

[0018] In one aspect of the present invention, the first acoustic impedance region is made of silicon dioxide.

[0019] In one aspect of the present invention, the second acoustic impedance region is made of alumina, aluminum nitride, silicon nitride, silicon oxynitride, silicon or silicon carbide.

[0020] In one aspect of the present invention, the supporting substrate is made of sapphire, silicon, alumina, spinel, quartz crystal or glass.

[0021] A module including the acoustic wave device is one aspect of the present invention. Effect of the Invention

[0022] According to the present disclosure, it is possible to provide an acoustic wave device having good temperature characteristics and further suppressed spurious emissions, and a method for manufacturing the same. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a cross-sectional view of an acoustic wave device 1 according to a first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing the device chip 5 of the acoustic wave device 1 according to the first embodiment. [Diagram 3] FIG. 3 is a top view of the functional element 50 of the acoustic wave device 1 according to the first embodiment. [Figure 4] FIG. 4 is a diagram illustrating the resonance characteristics of the resonator of the acoustic wave device 1 according to the first embodiment. [Diagram 5] FIG. 5 is a diagram illustrating the resonance characteristics of the acoustic wave device 1 according to the first embodiment and the resonator of a comparative example. [Figure 6] FIG. 6 is a cross-sectional view showing a configuration in which five second acoustic impedance regions 12B are arranged within the range of eight electrode fingers 51b. [Figure 7] FIG. 7 is a top view of the functional element 50 of the acoustic wave device 1 according to the second embodiment. [Figure 8] FIG. 8 is a diagram illustrating a method for manufacturing the acoustic wave device 1. As shown in FIG. [Figure 9]FIG. 9 is a vertical cross-sectional view of a module to which the acoustic wave device 1 according to the first or second embodiment is applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The embodiments will be described with reference to the accompanying drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals. Duplicate descriptions of the parts will be appropriately simplified or omitted.

[0025] Embodiment 1 FIG. 1 is a cross-sectional view of an acoustic wave device 1 according to a first embodiment.

[0026] As shown in FIG. 1, the acoustic wave device 1 includes a wiring substrate 3, an external connection terminal 31, a device chip 5, electrode pads 9, bumps 15, and a sealing portion 17.

[0027] For example, the wiring board 3 is a multi-layer board made of resin, or a low temperature co-fired ceramics (LTCC) multi-layer board made of a plurality of dielectric layers.

[0028] A plurality of external connection terminals 31 are formed on the lower surface of the wiring board 3 .

[0029] A plurality of electrode pads 9 are formed on the main surface of the wiring board 3. For example, the electrode pads 9 are made of copper or an alloy containing copper. For example, the thickness of the electrode pads 9 is 10 μm to 20 μm.

[0030] The bumps 15 are formed on the upper surface of each of the electrode pads 9. For example, the bumps 15 are gold bumps. For example, the height of the bumps 15 is 10 μm to 50 μm.

[0031] A gap 16 is formed between the wiring board 3 and the device chip 5 .

[0032] The device chip 5 is mounted on the wiring board 3 by flip-chip bonding via the bumps 15. The device chip 5 is electrically connected to the plurality of electrode pads 9 via the plurality of bumps 15.

[0033] The device chip 5 is a substrate on which the acoustic wave elements 50 are formed. For example, on the main surface of the device chip 5, a transmission filter and a reception filter including a plurality of acoustic wave elements 50, which are mainly resonators, are formed.

[0034] The transmit filter is formed so as to pass electrical signals in a desired frequency band, and is, for example, a ladder-type filter made up of a plurality of series resonators and a plurality of parallel resonators.

[0035] The receive filter is configured to pass electrical signals in a desired frequency band, and is, for example, a ladder filter.

[0036] The sealing portion 17 is formed so as to cover the device chip 5. For example, the sealing portion 17 is made of an insulating material such as a synthetic resin. For example, the sealing portion 17 is made of a metal.

[0037] When the sealing portion 17 is made of a synthetic resin, the synthetic resin is an epoxy resin, a polyimide, etc. Preferably, the sealing portion 17 is made of an epoxy resin and is formed of the epoxy resin using a low temperature curing process.

[0038] FIG. 2 is a cross-sectional view showing the device chip 5 of the acoustic wave device 1 according to the first embodiment.

[0039] 2, the device chip 5 includes a silicon nitride layer 10, a piezoelectric substrate 11, a medium layer 12, and a support substrate 13. On the piezoelectric substrate 11, an acoustic wave element 50 is formed.

[0040] The thickness of the silicon nitride layer 10 can be, for example, 0.1λ to 0.6λ, where λ is the wavelength of the acoustic wave determined by the electrode pitch of the IDT electrodes.

[0041] The piezoelectric substrate 11 is, for example, a substrate made of a piezoelectric single crystal such as lithium tantalate, lithium niobate, or quartz crystal. In another example, the piezoelectric substrate 11 is a substrate made of a piezoelectric ceramic.

[0042] The thickness of the piezoelectric substrate 11 can be set to, for example, 0.1λ to 0.9λ, where λ is the wavelength of an elastic wave determined by the electrode pitch of the IDT electrodes.

[0043] A semiconductor layer may be provided between the silicon nitride layer 10 and the piezoelectric substrate 11. The semiconductor layer may be made of, for example, silicon. By using silicon having a thickness of, for example, 5 nm to 20 nm for bonding the silicon nitride layer 10 and the piezoelectric substrate 11, bonding can be achieved without increasing unnecessary spurious signals.

[0044] The medium layer 12 includes a first acoustic impedance region 12A and a second acoustic impedance region 12B. The first acoustic impedance region 12A is made of, for example, silicon nitride, silicon oxynitride, silicon, alumina, silicon dioxide, or silicon carbide. The second acoustic impedance region 12B is made of, for example, alumina, aluminum nitride, silicon nitride, silicon oxynitride, silicon, or silicon carbide, and is made of a material different from that used in the first acoustic impedance region 12A.

[0045] The thickness of medium layer 12 can be, for example, 0.05λ to 0.45λ, where λ is the wavelength of the elastic wave determined by the electrode pitch of the IDT electrodes. The total thickness of silicon nitride layer 10, piezoelectric substrate 11, and medium layer 12 can be, for example, 1.0λ or less, where λ is the wavelength of the elastic wave determined by the electrode pitch of the IDT electrodes.

[0046] 2, the first acoustic impedance region 12A and the second acoustic impedance region 12B are arranged in three periods with respect to the four electrode fingers 51b on the piezoelectric substrate 11. In other words, three second acoustic impedance regions 12B are arranged within the range of the four electrode fingers 51b. In further other words, the first acoustic impedance region 12A and the second acoustic impedance region 12B are arranged at a pitch different from the pitch of the electrode fingers 51b. The first acoustic impedance region 12A and the second acoustic impedance region 12B are arranged alternately with the same thickness.

[0047] The support substrate 13 can be formed of, for example, sapphire, silicon, alumina, spinel, silicon nitride, aluminum nitride, silicon carbide, silicon oxynitride, diamond, quartz, glass, etc. The support substrate 13 should have a small thermal expansion coefficient and a high Young's modulus. This is because the temperature characteristics of the acoustic wave device 1 are improved. A sapphire substrate, which is a typical substrate that satisfies these conditions, is hard and chemically stable, so that surface processing to have an uneven or jagged shape is difficult, resulting in a decrease in yield. Therefore, it is desirable for the support substrate 13 to have a flat, plate-like rectangular parallelepiped shape.

[0048] The thickness of the support substrate 13 can be, for example, from 50 μm to 200 μm.

[0049] Next, an example of an acoustic wave element 50 formed on a piezoelectric substrate 11 will be described with reference to Fig. 3. Fig. 3 is a top view of the functional element 50 of the acoustic wave device 1 according to the first embodiment.

[0050] 3 is a perspective view of piezoelectric substrate 11 for convenience of explanation, and although not shown, an acoustic wave element 50 including an IDT (Interdigital Transducer) electrode 51 and a pair of reflectors 52 is formed on the main surface of piezoelectric substrate 11 (see FIG. 2). IDT electrode 51 and a pair of reflectors 52 are provided so as to excite acoustic waves (mainly SH waves).

[0051] For example, the IDT electrode 51 and the pair of reflectors 52 are formed of an alloy of aluminum and copper, or an appropriate metal such as aluminum, molybdenum, iridium, tungsten, cobalt, nickel, ruthenium, chromium, strontium, titanium, palladium, or silver, or an alloy thereof.

[0052] For example, the IDT electrode 51 and the pair of reflectors 52 are formed of a laminated metal film in which a plurality of metal layers are laminated. For example, the thickness of the IDT electrode 51 and the pair of reflectors 52 is 150 nm to 450 nm.

[0053] The IDT electrode 51 includes a pair of comb-shaped electrodes 51a that face each other. The comb-shaped electrodes 51a include a plurality of electrode fingers 51b and a bus bar 51c.

[0054] The electrode fingers 51b are arranged with their longitudinal directions aligned. The bus bar 51c connects the electrode fingers 51b together.

[0055] One of the pair of reflectors 52 is adjacent to one side of the IDT electrode 51. The other of the pair of reflectors 52 is adjacent to the other side of the IDT electrode 51.

[0056] A medium layer 12 is formed between a piezoelectric substrate 11 and a support substrate 13 (not shown in FIG. 3). As shown in FIG. 3, first acoustic impedance region 12A and second acoustic impedance region 12B each form a stripe-shaped region having a longitudinal direction and a lateral direction. As shown in FIG. 3, first acoustic impedance region 12A and second acoustic impedance region 12B are alternately arranged in the lateral direction.

[0057] As shown in FIG. 3, the longitudinal direction of first acoustic impedance region 12A and second acoustic impedance region 12B is aligned in the same direction as the longitudinal direction of electrode finger 51b.

[0058] 4 is a diagram showing the resonance characteristics of the resonator of the acoustic wave device 1 according to the first embodiment. Single crystal lithium tantalate was used for the piezoelectric substrate 11. The thicknesses were set and calculated so that the total thickness of the silicon nitride layer 10 and the piezoelectric substrate 11 was 0.65λ, that is, when the thicknesses of the piezoelectric substrate 11 were 0.2λ, 0.25λ, 0.3λ, 0.4λ, and 0.6λ, the thicknesses of the silicon nitride layer 10 were 0.45λ, 0.4λ, 0.35λ, 0.25λ, and 0.05λ, respectively. FIG. 4 shows the calculation results of the resonance characteristics of 0.2λ when the thickness of piezoelectric substrate 11 is 0.2λ, the resonance characteristics of 0.25λ when the thickness of piezoelectric substrate 11 is 0.25λ, the resonance characteristics of 0.3λ when the thickness of piezoelectric substrate 11 is 0.3λ, the resonance characteristics of 0.4λ when the thickness of piezoelectric substrate 11 is 0.4λ, and the resonance characteristics of 0.6λ when the thickness of piezoelectric substrate 11 is 0.6λ.

[0059] Here, IDT electrode 51 had a thickness of 0.1λ and was made of aluminum. Medium layer 12 had a thickness of 0.25λ. First acoustic impedance region 12A and second acoustic impedance region 12B had the same width in the short side direction, that is, the duty ratio was 50%. First acoustic impedance region 12A was made of silicon dioxide. Second acoustic impedance region 12B was made of alumina. Support substrate 13 was a sapphire substrate.

[0060] In Figure 4, the peaks and valleys seen around 950MHz to 1050MHz are associated with the original resonance mode. The peaks and valleys that appear at higher frequencies, in this case around 1200MHz to 1700MHz, are due to non-original resonance modes and are called spurious. Strong spurious can cause significant degradation of characteristics when assembling resonators to configure a filter, etc., so the smaller the height of the spurious peaks and the depth of the spurious valleys, the better the characteristics.

[0061] 4, the resonator of the acoustic wave device according to the first embodiment has particularly few spurious components at the resonance characteristics 0.2λ, 0.25λ, and 0.3λ of piezoelectric substrate 11 thicknesses of 0.2λ, 0.25λ, and 0.3λ, among the resonance characteristics 0.2λ at the thickness of piezoelectric substrate 11 of 0.2λ, 0.25λ at the thickness of piezoelectric substrate 11 of 0.25λ, 0.3λ at the thickness of piezoelectric substrate 11 of 0.3λ, 0.4λ at the thickness of piezoelectric substrate 11, and 0.6λ at the thickness of piezoelectric substrate 11. It is also found that the spurious components are particularly few when silicon nitride layer 10 is thicker than piezoelectric substrate 11.

[0062] 5 is a diagram showing the resonance characteristics of the acoustic wave device 1 according to the first embodiment and a resonator of a comparative example. In the resonator of the acoustic wave device 1 according to the first embodiment, lithium tantalate is used for the piezoelectric substrate 11. The thicknesses were set and calculated so that the total thickness of the silicon nitride layer 10 and the piezoelectric substrate 11 was 0.65λ, that is, when the thicknesses of the piezoelectric substrate 11 were 0.2λ and 0.3λ, the thicknesses of the silicon nitride layer 10 were 0.45λ and 0.35λ, respectively. The rest is as described in FIG. 4.

[0063] In the comparative example, the thicknesses were set and calculated so that the total thickness of the silicon nitride layer 10 formed on the sapphire substrate and the piezoelectric substrate 11 was 0.9λ, that is, when the thicknesses of the piezoelectric substrate 11 were 0.2λ and 0.3λ, the thicknesses of the silicon nitride layer 10 were 0.7λ and 0.6λ, respectively. The comparative example does not include the medium layer 12. In other words, the comparative example is equivalent to the first embodiment in which silicon dioxide is used for both the first acoustic impedance region 12A and the second acoustic impedance region 12B, and the remaining conditions are the same as those of the first embodiment.

[0064] As shown in Figure 5, the resonator of the acoustic wave device of embodiment 1 shows significantly improved spurious emissions when compared with the resonance characteristics of 0.2λNS when the thickness of piezoelectric substrate 11 is 0.2λ and 0.3λ when the thickness of piezoelectric substrate 11 is 0.3λ in the comparative example, regardless of whether the total thickness of silicon nitride layer 10 and piezoelectric substrate 11 is 0.2λ, which shows resonance characteristics of 0.2λ, or 0.3λ, which shows resonance characteristics of 0.3λ when the thickness of piezoelectric substrate 11 is 0.3λ.

[0065] Here, good results were obtained under the condition that the first acoustic impedance region 12A and the second acoustic impedance region 12B are arranged in three periods for four electrode fingers, but the period of the first acoustic impedance region 12A and the second acoustic impedance region 12B relative to the number of electrode fingers is not limited to this. However, it is preferable that the number of electrode fingers and the number of periods of the first acoustic impedance region 12A and the second acoustic impedance region 12B do not match. This is because, if they match, the spurious reduction effect is reduced. For example, as shown in FIG. 6, a configuration in which five second acoustic impedance regions 12B are arranged within a range of eight electrode fingers 51b may be used. In other words, the good region has width.

[0066] According to the first embodiment described above, it is possible to provide an acoustic wave device having better temperature characteristics and further suppressing spurious emissions.

[0067] Embodiment 2 Fig. 7 is a top view of the functional element 50 of the acoustic wave device 1 according to the second embodiment. As shown in Fig. 7, the longitudinal direction of the first acoustic impedance region 12A and the second acoustic impedance region 12B are arranged in a direction different from the longitudinal direction of the electrode fingers 51b. This arrangement generates an acoustic impedance difference in the transverse mode waves, making it possible to reduce the transverse mode spurious.

[0068] The other configuration is the same as in the first embodiment, so the description will be omitted.

[0069] According to the second embodiment described above, it is possible to provide an acoustic wave device in which high frequency spurious responses are suppressed and transverse mode spurious responses are reduced.

[0070] Next, a method for manufacturing the acoustic wave device 1 according to the first embodiment will be described. Fig. 8 is a diagram for explaining a method for manufacturing the acoustic wave device 1 according to the first embodiment.

[0071] 8(a), a first acoustic impedance film is formed on a support substrate 13. Next, the first acoustic impedance film is patterned. For the patterning process, an appropriate method is selected depending on the material of the first acoustic impedance film, such as a lift-off method or an etching method.

[0072] As shown in Fig. 8(b), the area from which the first acoustic impedance film has been removed by the patterning process is filled with a second acoustic impedance material. The filling method for the second acoustic impedance material is selected from a variety of methods, such as a squeegee method, a vapor deposition method, and a sputtering method, depending on the material.

[0073] As shown in Fig. 8(c), the second acoustic impedance material is polished until the first acoustic impedance film is exposed. The polishing process may be performed by a chemical polishing method or a mechanical polishing method, depending on the material.

[0074] As shown in FIG. 8(d), after the polishing step, a silicon nitride layer 10 is formed. The silicon nitride layer 10 is formed by an appropriate method selected depending on the material, such as a plasma CVD method or a sputtering method. The silicon nitride layer 10 is then bonded to a piezoelectric substrate 11. Alternatively, the silicon nitride layer 10 may be formed on the piezoelectric substrate 11 and then bonded to the medium layer 12. An acoustic wave element 50 is configured on the piezoelectric substrate 11 so as to obtain desired device characteristics, and a packaging step is performed to obtain the acoustic wave device 1 according to the first embodiment.

[0075] 9 is a vertical cross-sectional view of a module to which the acoustic wave device 1 according to the first or second embodiment is applied. Note that the same reference numerals are used to designate the same or corresponding parts as those in the first or second embodiment, and a description of these parts will be omitted.

[0076] In FIG. 9, the module 100 includes a wiring board 130, a plurality of external connection terminals 131, an integrated circuit component IC, an acoustic wave device 1, an inductor 111, and a sealing portion 117.

[0077] A plurality of external connection terminals 31 are formed on the lower surface of the wiring board 130. The plurality of external connection terminals 131 are mounted on a motherboard of a preset mobile communication terminal.

[0078] For example, the integrated circuit component IC is mounted inside the wiring board 130. The integrated circuit component IC includes a switching circuit and a low-noise amplifier.

[0079] The acoustic wave device 1 is mounted on a main surface of a wiring board 130.

[0080] The inductor 111 is mounted on the main surface of the wiring board 130. The inductor 111 is mounted for impedance matching. For example, the inductor 111 is an Integrated Passive Device (IPD).

[0081] The sealing portion 117 seals a plurality of electronic components including the acoustic wave device 1 .

[0082] The module 100 described above includes the acoustic wave device 1. Therefore, it is possible to provide a module including an acoustic wave device that has better temperature characteristics and in which spurious emissions are further suppressed.

[0083] Having described several aspects of at least one embodiment, it should be understood that various alterations, modifications, and improvements will readily occur to those skilled in the art and are intended to be part of this disclosure, and are intended to be within the scope of this disclosure.

[0084] It is to be understood that the embodiments of the method and apparatus described herein are not limited in their application to the details of construction and the arrangement of components set forth in the above description or illustrated in the accompanying drawings, and the method and apparatus can be implemented in other embodiments and practiced or carried out in various ways.

[0085] The specific implementations are provided herein for illustrative purposes only and are not intended to be limiting.

[0086] The phraseology and terminology used in this disclosure are for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," "having," "including" and variations thereof herein means the inclusion of the items listed thereafter and equivalents thereof as well as additional items.

[0087] References to "or" may be construed as meaning that any term described using "or" refers to one, more than one, and all of those described terms.

[0088] All references to front, back, left, right, top, bottom, up, down, horizontal, vertical, front and back are intended for convenience of description. Such references are not intended to limit the components of this disclosure to any one positional or spatial orientation. Accordingly, the foregoing description and drawings are by way of example only. [Explanation of symbols]

[0089] 1 Acoustic wave device, 3 Wiring board, 5 Device chip, 17 Sealing part 10 silicon nitride layer, 11 piezoelectric substrate, 12 medium layer 13 Support substrate, 50 Acoustic wave element 12A First Acoustic Impedance Region 12B Second Acoustic Impedance Region 100 module, 111 inductor, 117 sealing portion, 130 wiring board

Claims

1. A support substrate; a medium layer formed on the support substrate; a silicon nitride layer formed on the medium layer; a piezoelectric substrate formed on the silicon nitride layer; a resonator including an IDT electrode formed on the piezoelectric substrate; Equipped with The medium layer is A first acoustic impedance region having a stripe shape having a longitudinal direction and a lateral direction; a second acoustic impedance region having an acoustic impedance different from that of the first acoustic impedance region, the second acoustic impedance region being striped and having a longitudinal direction and a lateral direction and arranged alternately with the first acoustic impedance region; An acoustic wave device in which the total thickness of the silicon nitride layer and the piezoelectric substrate is 1.0λ or less, where λ is the wavelength of an acoustic wave determined by the electrode pitch of the IDT electrodes.

2. 2. The acoustic wave device according to claim 1, wherein a total thickness of the medium layer, the silicon nitride layer and the piezoelectric substrate is 1.0λ or less, where λ is the wavelength of an acoustic wave determined by the electrode pitch of the IDT electrodes.

3. The acoustic wave device according to claim 1 , wherein the silicon nitride layer has a thickness greater than a thickness of the piezoelectric substrate.

4. 2 . The acoustic wave device according to claim 1 , wherein a total thickness of the silicon nitride layer and the piezoelectric substrate is 0.7λ or less, where λ is the wavelength of an acoustic wave determined by the electrode pitch of the IDT electrodes.

5. The acoustic wave device of claim 1 , further comprising a semiconductor layer between the silicon nitride layer and the piezoelectric substrate.

6. The acoustic wave device according to claim 1 , wherein a longitudinal direction of the first acoustic impedance region and the second acoustic impedance region is arranged in the same direction as a longitudinal direction of electrode fingers of the IDT electrode.

7. The acoustic wave device according to claim 1 , wherein the first acoustic impedance region and the second acoustic impedance region are arranged at a pitch different from an electrode pitch of the IDT electrode.

8. The acoustic wave device according to claim 1 , wherein the thickness of the piezoelectric substrate is 0.1λ or more and 0.3λ or less, where λ is the wavelength of an acoustic wave determined by the electrode pitch of the IDT electrodes.

9. 2 . The acoustic wave device according to claim 1 , wherein the medium layer has a thickness of 0.1λ to 0.5λ, where λ is a wavelength of an acoustic wave determined by an electrode pitch of the IDT electrodes.

10. The acoustic wave device of claim 1 , wherein the first acoustic impedance region is made of silicon dioxide.

11. The acoustic wave device of claim 1 , wherein the second acoustic impedance region is made of alumina, aluminum nitride, silicon nitride, silicon oxynitride, silicon, or silicon carbide.

12. 2. The acoustic wave device according to claim 1, wherein the support substrate is made of sapphire, silicon, alumina, spinel, quartz, or glass.

13. A module comprising an acoustic wave device according to claim 1 .

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