Elastic wave device and module using elastic wave module

Abstract

To provide an elastic wave device in which a process after formation of a resonator is reduced, the damage on the resonator due to the process is reduced, and a lateral mode spurious and a high frequency spurious are suppressed, and a module using the elastic wave device.SOLUTION: An elastic wave device includes a piezoelectric substrate, a resonator formed on a main surface of the piezoelectric substrate, a spurious absorption layer formed on another main surface of the piezoelectric substrate, and a hypersonic film layer formed between the piezoelectric substrate and the spurious absorption layer. The spurious absorption layer includes a tetragonal crystal substrate and its hypersonic speed is lower than that of the piezoelectric substrate.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to an elastic wave device and a module using the elastic wave device. Specifically, it relates to a surface acoustic wave device using an SH wave, such as a filter, a duplexer, or a multiplexer.

Background Art

[0002] In a high-frequency communication system for a mobile communication terminal typified by a smartphone, a high-frequency filter or the like is used to remove unnecessary signals outside the frequency band used for communication.

[0003] For a high-frequency filter or the like, an elastic wave device having a surface acoustic wave (SAW) element or the like is used. A SAW element is an element in which an interdigital transducer (IDT) 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 substrate is created by bonding a piezoelectric substrate that propagates elastic waves and a support substrate having a thermal expansion coefficient smaller than that of the piezoelectric substrate. Next, a large number of IDT electrodes are formed on the multilayer substrate using photolithography technology, and then it is cut into a predetermined size by dicing to obtain a surface acoustic wave device. In this manufacturing method, by using a multilayer substrate, the change in the size of the piezoelectric substrate when the temperature changes is suppressed by the support substrate, so that the frequency characteristics as an elastic wave device are stabilized.

[0005] For example, as described in Patent Document 1 or the like, in order to suppress the lateral mode spurious of an elastic wave device, a groove is formed in the intersection region of electrode fingers, and an additional film is formed, etc., to vary the sound velocity in the lateral direction with respect to the propagation direction of the surface acoustic wave, thereby suppressing the lateral mode spurious.

Prior Art Documents

Patent Documents

[0006] Patent Document 1 Japanese Patent Application Laid-Open No. 2019-50544 Summary of the Invention Problems to be Solved by the Invention

[0007] As disclosed in Patent Document 1, in order to suppress the lateral mode spurious of an elastic wave device, forming a groove in the crossing region of electrode fingers and forming an additional film make the process complicated. In particular, the process of forming these after forming the resonator causes damage to the resonator and accelerates the deterioration of filter characteristics.

[0008] The present disclosure has been made to solve the above problems. An object of the present disclosure is to provide an elastic wave device in which lateral mode spurious and high-frequency spurious are suppressed while reducing the number of processes after resonator formation and reducing damage to the resonator caused by the processes, and a module using the elastic wave device. Means for Solving the Problems

[0009] The elastic wave device according to the present disclosure includes: a piezoelectric substrate, a resonator formed on a main surface of the piezoelectric substrate, and a spurious absorption layer formed on the other main surface of the piezoelectric substrate, and a high sound velocity film layer formed between the piezoelectric substrate and the spurious absorption layer and having a higher sound velocity than the piezoelectric substrate, and the spurious absorption layer is made of a tetragonal crystal substrate and is an elastic wave device having a slower sound velocity than the piezoelectric substrate.

[0010] Providing a temperature characteristic improvement layer formed between the piezoelectric substrate and the spurious absorption layer is one form of the present disclosure.

[0011] The thickness of the spurious absorption layer is 3λ or more and 20λ or less when the wavelength of the wave of the main mode in which the resonator vibrates is λ, and it is one aspect of the present disclosure to provide a support substrate on the main surface of the spurious absorption layer on the side opposite to the piezoelectric substrate.

[0012] In one aspect of the present disclosure, the thickness of the high-velocity film layer is smaller than the thickness of the piezoelectric substrate.

[0013] In one aspect of the present disclosure, the thickness of the high-velocity film layer is smaller than the thickness of the temperature characteristic improvement layer.

[0014] In one aspect of the present disclosure, the thickness of the high-velocity film layer is 0.1λ or more and 0.3λ or less when the wavelength of the wave of the main mode in which the resonator vibrates is λ.

[0015] In one aspect of the present disclosure, the spurious absorption layer has a lower crystal density than the piezoelectric substrate.

[0016] In one aspect of the present disclosure, the spurious absorption layer is a Li2B4O7 single crystal substrate.

[0017] In one aspect of the present disclosure, the support substrate is a substrate made of sapphire, silicon, alumina, or spinel.

[0018] The cut angle of the main surface of the spurious absorption layer is such that the Euler angles (φ, θ, ψ) are φ = 0° ± 2° or 90° ± 2°, θ = 90° ± 2°, ψ = 80° to 100°, which is one aspect of the present disclosure.

[0019] A module including the elastic wave device is one aspect of the present invention.

Advantages of the Invention

[0020] According to the present disclosure, it is possible to provide an elastic wave device in which transverse mode spurious and high-frequency spurious are suppressed while reducing the processes after resonator formation and reducing the damage to the resonator caused by the processes, and a module using the elastic wave device.

Brief Description of the Drawings

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DETAILED DESCRIPTION OF THE INVENTION

[0022] Embodiments will be described with reference to the accompanying drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions of such parts are appropriately simplified or omitted.

[0023] Embodiment 1. FIG. 1 is a sectional view showing the elastic wave device 1 according to Embodiment 1.

[0024] As shown in FIG. 1, the elastic wave device 1 includes a package substrate 3, external connection terminals 31, a device chip 5, electrode pads 9, bumps 15, and a sealing portion 17.

[0025] For example, the package substrate 3 is a multilayer substrate made of resin. For example, the package substrate 3 is a low-temperature co-fired ceramics (LTCC) multilayer substrate composed of a plurality of dielectric layers.

[0026] A plurality of external connection terminals 31 are formed on the lower surface of the package substrate 3.

[0027] A plurality of electrode pads 9 are formed on the main surface of the package substrate 3. For example, the electrode pads 9 are formed of copper or an alloy containing copper. For example, the thickness of the electrode pads 9 is from 10 μm to 20 μm.

[0028] The bumps 15 are formed on the upper surfaces of the respective electrode pads 9. For example, the bumps 15 are gold bumps. For example, the height of the bumps 15 is from 10 μm to 50 μm.

[0029] A gap 16 is formed between the package substrate 3 and the device chip 5.

[0030] The device chip 5 is flip-chip bonded to the package substrate 3 via the bumps 15. The device chip 5 is electrically connected to the plurality of electrode pads 9 via the plurality of bumps 15.

[0031] The device chip 5 is a substrate on which the elastic wave element 50 is formed. For example, on the main surface of the device chip 5, a transmission filter and a reception filter including a plurality of elastic wave elements 50 mainly serving as resonators are formed.

[0032] The transmission filter is formed so that an electrical signal in a desired frequency band can pass therethrough. For example, the transmission filter is a ladder-type filter including a plurality of series resonators and a plurality of parallel resonators.

[0033] The reception filter is formed so that an electrical signal in a desired frequency band can pass therethrough. For example, the reception filter is a ladder-type filter.

[0034] The sealing portion 17 is formed so as to cover the device chip 5. For example, the sealing portion 17 is formed of an insulator such as a synthetic resin. For example, the sealing portion 17 is formed of metal.

[0035] When the sealing portion 17 is formed of a synthetic resin, the synthetic resin is an epoxy resin, a polyimide, or the like. Preferably, the sealing portion 17 is formed of an epoxy resin using a low-temperature curing process.

[0036] FIG. 2 is a cross-sectional view showing the device chip 5 of the elastic wave device 1 according to Embodiment 1.

[0037] As shown in FIG. 2, the device chip 5 includes a piezoelectric substrate 11, a high acoustic velocity film layer 12, and a spurious absorption layer 13. The elastic wave element 50 is formed on the piezoelectric substrate 11.

[0038] The piezoelectric substrate 11 is a substrate formed of a piezoelectric single crystal such as lithium tantalate, lithium niobate, or quartz, for example. In another example, the piezoelectric substrate 11 is a substrate formed of piezoelectric ceramics.

[0039] The thickness of the piezoelectric substrate 11 can be, for example, from 0.1λ to 0.9λ, where λ is the wavelength of the elastic wave determined by the electrode pitch of the IDT electrode.

[0040] The high sound velocity film layer 12 is a member having a higher sound velocity than the piezoelectric substrate 11. Thereby, waves with a high sound velocity can be confined, and spurious signals generated on the high-frequency side can be suppressed. For example, it can be formed of SiN. The thickness of the high sound velocity film layer 12 can be, for example, from 0.1λ to 0.3λ, where λ is the wavelength of the elastic wave determined by the electrode pitch of the IDT electrode.

[0041] The spurious absorption layer 13 can be formed of, for example, a Li2B4O7 single crystal substrate or the like. The Li2B4O7 single crystal is a tetragonal crystal, and the crystal density is 2.44 g / cm 3 is. Also, the crystal density of the lithium tantalate single crystal is 7.45 g / cm 3 is. The Li2B4O7 single crystal substrate has a lower density than the lithium tantalate single crystal substrate, but the sound velocity of the shear wave is slow.

[0042] Although the sound velocity of the Li2B4O7 single crystal substrate is slow, when the SAW vibration reaches the Li2B4O7 single crystal substrate, due to the presence of the unique vibration of the SH wave, the energy is confined to the surface without leaking in the substrate depth direction. The natural vibration of the Li2B4O7 single crystal substrate is faster than the sound velocity of the wave generated by the natural vibration of the lithium tantalate single crystal substrate. Thereby, the resonance energy of the wave in the main mode can be confined.

[0043] In addition, for the Li2B4O7 single crystal substrate, as the spurious absorption layer 13, it is desirable to use an orientation that does not have piezoelectricity. Since the Li2B4O7 single crystal is tetragonal, the wave propagation speed has little orientation dependence, so the wave is less likely to spread laterally. On a tetragonal crystal, the wave has a straight - advancing property of traveling straight with respect to the crystal direction. As a result, the so - called transverse mode waves generated in the direction orthogonal to the SAW propagation direction are reduced. Therefore, the transverse mode spurious is reduced.

[0044] FIG. 3 is a cross - sectional view showing another example of the device chip 5 of the elastic wave device 1 according to Embodiment 1. As shown in FIG. 3, the device chip 5 includes a temperature characteristic improvement layer 14 between the piezoelectric substrate 11 and the high - sound - velocity film layer 12. It is desirable to use a member having a temperature characteristic opposite to that of the piezoelectric substrate 11 for the temperature characteristic improvement layer 14. The temperature characteristic improvement layer 14 is made of, for example, silicon dioxide (SiO2).

[0045] The thickness of the temperature characteristic improvement layer 14 can be, for example, from 0.05λ to 0.45λ, where λ is the wavelength of the elastic wave determined by the electrode pitch of the IDT electrode. The total thickness of the piezoelectric substrate 11 and the temperature characteristic improvement layer 14 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 electrode.

[0046] A semiconductor layer may be provided between the piezoelectric substrate 11 and the temperature characteristic improvement layer 14. For example, silicon can be used for the semiconductor layer. By using silicon with a thickness of, for example, 5 nm to 20 nm for the bonding between the piezoelectric substrate 11 and the temperature characteristic improvement layer 14, bonding can be achieved without increasing unnecessary spurious.

[0047] Next, an example of the elastic wave element 50 formed on the piezoelectric substrate 11 will be described with reference to FIG. 4. FIG. 3 is a top view of the functional element 50 of the elastic wave device 1 according to Embodiment 1.

[0048] As shown in FIG. 4, an elastic wave element 50 including an IDT (Interdigital Transducer) electrode 51 and a pair of reflectors 52 is formed on the main surface of a piezoelectric substrate 11. The IDT electrode 51 and the pair of reflectors 52 are provided so as to be able to excite elastic waves (mainly SH waves).

[0049] For example, the IDT electrode 51 and the pair of reflectors 52 are formed of an alloy of aluminum and copper. For example, the IDT electrode 51 and the pair of reflectors 52 are formed of an appropriate metal such as aluminum, molybdenum, iridium, tungsten, cobalt, nickel, ruthenium, chromium, strontium, titanium, palladium, silver or an alloy thereof.

[0050] 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 from 150 nm to 450 nm.

[0051] The IDT electrode 51 includes a pair of comb-shaped electrodes 51a. The pair of comb-shaped electrodes 51a face each other. The comb-shaped electrode 51a includes a plurality of electrode fingers 51b and a bus bar 51c.

[0052] The plurality of electrode fingers 51b are arranged with their longitudinal directions aligned. The bus bar 51c connects the plurality of electrode fingers 51b.

[0053] 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.

[0054] FIG. 5 is a diagram showing the resonance characteristics of the resonator of the elastic wave device 1 according to Embodiment 1. The piezoelectric substrate 11 uses single crystal lithium tantalate. The thickness of the piezoelectric substrate 11 is set to 0.3λ.

[0055] Here, the IDT electrode 51 had a thickness of 0.1λ and was formed of aluminum. The thickness of the temperature characteristic improvement layer 14 was 0.4λ and it was formed of SiO2. The thickness of the spurious absorption layer 13 was 15λ and a Li2B4O7 single crystal substrate was used. The high acoustic velocity film layer 12 was formed of SiN.

[0056] FIG. 6 is an enlarged view of the resonance characteristics of the elastic wave device 1 shown in the region R of FIG. 5. As shown in FIG. 5, spurious signals are generated in the frequency band from 1550 MHz to 1650 MHz.

[0057] Here, the solid line represents the characteristics when the thickness of the high acoustic velocity film layer 12 is 0.25λ. The long chain line represents the characteristics when the thickness of the high acoustic velocity film layer 12 is 0.2λ. The long dashed line represents the characteristics when the thickness of the high acoustic velocity film layer 12 is 0.15λ. The dash-dotted line represents the characteristics when the thickness of the high acoustic velocity film layer 12 is 0.1λ. The dashed line represents the characteristics when the thickness of the high acoustic velocity film layer 12 is 0.05λ. The dotted line represents the characteristics when the thickness of the high acoustic velocity film layer 12 is 0λ.

[0058] As shown in FIG. 6, when the thickness of the high acoustic velocity film layer 12 is 0.05λ, the spurious suppression effect is slight, but the spurious signal has moved to the high frequency side. When the thickness of the high acoustic velocity film layer 12 is 0.1λ, the spurious suppression effect becomes apparent and the spurious signal has moved further to the high frequency side.

[0059] When the thickness of the high acoustic velocity film layer 12 is 0.15λ or 0.2λ, the spurious suppression effect is most apparent. When the thickness of the high acoustic velocity film layer 12 is 0.25λ, the spurious suppression effect is a significant effect compared to when the thickness of the high acoustic velocity film layer 12 is 0.1λ, but is slightly inferior compared to when the thickness of the high acoustic velocity film layer 12 is 0.15λ or 0.2λ.

[0060] Therefore, it is desirable that the thickness of the high-velocity sound film layer 12 be, for example, from 0.1λ to 0.3λ. More desirably, the thickness of the high-velocity sound film layer 12 is more desirably from 0.15λ to 0.25λ. Even more desirably, the thickness of the high-velocity sound film layer 12 is even more desirably from 0.15λ to 0.2λ.

[0061] Figures 7 to 9 show the resonance characteristics of the resonator of the elastic wave device. The dependence of the resonance characteristics of the elastic wave device on the cut angle of the main surface of the Li2B4O7 single crystal substrate does not change depending on the presence or absence of the high-velocity sound film layer 12. Regardless of the presence or absence of the high-velocity sound film layer 12, since the vibration reaches the Li2B4O7 single crystal substrate, the spurious from the Li2B4O7 single crystal substrate still depends on the cut angle. In Figures 7 to 9, in the calculation of the resonance characteristics of the resonator of the elastic wave device, the case where the thickness of the high-velocity sound film layer 12 is calculated as 0λ is shown.

[0062] Figure 7 is a diagram showing the resonance characteristics of the resonator of the elastic wave device 1 according to Embodiment 1. The piezoelectric substrate 11 uses single crystal lithium tantalate. The thickness of the piezoelectric substrate 11 was 0.3λ.

[0063] Here, the IDT electrode 51 has a thickness of 0.1λ and is formed of aluminum. The thickness of the temperature characteristic improvement layer 14 was 0.4λ. The spurious absorption layer 13 uses a Li2B4O7 single crystal substrate.

[0064] In Figure 7(a), as the cut angle of the main surface of the Li2B4O7 single crystal substrate, the Euler angles (φ, θ, ψ) are (0°, 90°, 90°). In Figure 7(b), as the cut angle of the main surface of the Li2B4O7 single crystal substrate, the Euler angles (φ, θ, ψ) are (0°, 90°, 88°). In Figure 7(c), as the cut angle of the main surface of the Li2B4O7 single crystal substrate, the Euler angles (φ, θ, ψ) are (0°, 90°, 86°).

[0065] The resonance characteristics shown in FIGS. 7(a) and (b) have almost no transverse mode spurs. Thus, a deviation in the cut angle of about ±2% can be tolerated as an error range when there is substantially no problem with the quality of the resonance characteristics. The resonance characteristics shown in FIG. 7(c) have slightly generated transverse mode spurs, but the transverse mode spurs are suppressed to a considerable extent.

[0066] Here, since the crystal is symmetric, the Euler angle φ has the same effect at both 0° and 90°. Similarly, since the crystal is symmetric, the Euler angle ψ has the same effect at both 80° and 100°.

[0067] FIG. 8 is a diagram showing the resonance characteristics of the resonator of the elastic wave device 1 according to Embodiment 1. In FIG. 8(a), the Euler angles (φ, θ, ψ) are (0°, 90°, 84°) as the cut angle of the main surface of the Li2B4O7 single crystal substrate. In FIG. 8(b), the Euler angles (φ, θ, ψ) are (0°, 90°, 82°) as the cut angle of the main surface of the Li2B4O7 single crystal substrate. In FIG. 8(c), the Euler angles (φ, θ, ψ) are (0°, 90°, 80°) as the cut angle of the main surface of the Li2B4O7 single crystal substrate.

[0068] The resonance characteristics shown in FIGS. 8(a) to (c) have slightly generated transverse mode spurs. It can also be seen that the transverse mode spurs deteriorate as the Euler angle ψ approaches 80°. If the resonance characteristics deteriorate further beyond the transverse mode spurs shown in FIG. 8(c), it is considered difficult to use as an elastic wave device, especially in the high-end smartphone market.

[0069] FIG. 9 is a diagram showing the resonance characteristics of a comparative example of the resonator of the elastic wave device 1 according to Embodiment 1. In FIG. 9(a), the Euler angles (φ, θ, ψ) are (0°, 90°, 70°) as the cut angle of the main surface of the Li2B4O7 single crystal substrate. In FIG. 9(b), the Euler angles (φ, θ, ψ) are (0°, 90°, 60°) as the cut angle of the main surface of the Li2B4O7 single crystal substrate.

[0070] In FIG. 9(c), as the cut angle of the main surface of the Li2B4O7 single crystal substrate, the Euler angles (φ, θ, ψ) are (0°, 90°, 50°). In FIG. 9(d), as the cut angle of the main surface of the Li2B4O7 single crystal substrate, the Euler angles (φ, θ, ψ) are (0°, 90°, 45°). Others are as described in FIG. 7.

[0071] As shown in FIG. 9, in the comparative example, large horizontal mode spurs occur. As the cut angle of the main surface of the Li2B4O7 single crystal substrate, when the Euler angles (φ, θ, ψ) are (0°, 90°, 45° - 70°), it was found that as the angle from the crystal plane increases, the resonance characteristics separate and become characteristics combined with spurs.

[0072] Also, since the resonance impedance increases as the propagation direction changes from the crystal plane, energy leakage occurs in the substrate direction. When there are strong spurs, it causes significant characteristic degradation when combining resonators to form filters etc., so it can be said that the smaller the height of the spur peak and the depth of the valley, the better the characteristics.

[0073] According to Embodiment 1 described above, it is possible to provide an elastic wave device in which the horizontal mode spurs are suppressed while reducing the processes after resonator formation and reducing the damage to the resonator caused by the processes.

[0074] Embodiment 2. FIG. 10 is a cross-sectional view showing a device chip 5 of the elastic wave device 1 according to Embodiment 2. As shown in FIG. 10, the device chip 5 of the elastic wave device 1 according to Embodiment 2 includes a support substrate 20 on the other main surface opposite to the piezoelectric substrate 11 of the spur absorption layer 13.

[0075] The support substrate 20 can be formed of, for example, sapphire, silicon, alumina, spinel, silicon nitride, aluminum oxynitride, silicon carbide, silicon oxynitride, diamond, quartz, glass, or the like. The support substrate 20 preferably has a small coefficient of thermal expansion and a high Young's modulus. This is because the temperature characteristics of the surface acoustic wave device 1 are improved.

[0076] A sapphire substrate, which is a typical substrate satisfying such conditions, has high hardness and is chemically stable. Therefore, it is difficult to perform surface processing having an uneven shape or a jagged shape, and the yield is lowered. Accordingly, the support substrate 20 preferably has a flat rectangular parallelepiped shape.

[0077] The thickness of the support substrate 20 can be, for example, from 50 μm to 200 μm.

[0078] FIG. 11 is a diagram showing the resonance characteristics of the resonator of the surface acoustic wave device 1 according to Embodiment 2. The piezoelectric substrate 11 uses single crystal lithium tantalate. The thickness of the piezoelectric substrate 11 is 0.3λ. The IDT electrode 51 has a thickness of 0.1λ and is formed of aluminum. The thickness of the temperature characteristic improvement layer 14 is 0.4λ.

[0079] The spurious absorption layer 13 uses a Li2B4O7 single crystal substrate. As the cut angle of the main surface of the Li2B4O7 single crystal substrate, the Euler angles (φ, θ, ψ) are set to (0°, 90°, 90°). The thicknesses of the spurious absorption layer 13 are 2λ, 5λ, and 10λ.

[0080] FIG. 12 is an enlarged view of the resonance characteristics of the surface acoustic wave device 1 shown in the region R2 of FIG. 11. As shown in FIG. 12, spurious signals are generated in the frequency band from 1500 MHz to 1650 MHz. Here, the solid line represents the characteristics when the thickness of the spurious absorption layer 13 is 10λ. The broken line represents the characteristics when the thickness of the spurious absorption layer 13 is 5λ. The alternate long and short dash line represents the characteristics when the thickness of the spurious absorption layer 13 is 2λ.

[0081] As shown in Fig. 12, when the thickness of the spurious absorption layer 13 is 10λ, spurious is most suppressed. When the thickness of the spurious absorption layer 13 is 2λ, spurious is most generated. When the thickness of the spurious absorption layer 13 is 5λ, spurious is more suppressed than 2λ, but spurious is more generated than 10λ.

[0082] From this, it can be seen that the thicker the thickness of the spurious absorption layer 13, the higher the spurious suppression effect tends to be. Therefore, it is desirable that the thickness of the spurious absorption layer 13 be, for example, from 3λ to 20λ. More desirably, the thickness of the spurious absorption layer 13 is, for example, more desirably from 5λ to 20λ. Even more desirably, the thickness of the spurious absorption layer 13 is, for example, more desirably from 10λ to 20λ. Since other configurations are the same as those in Embodiment 1, the description thereof is omitted.

[0083] According to Embodiment 2 described above, an elastic wave device can be obtained in which the resonance characteristics and the lateral mode spurious on the high-frequency side are suppressed while reducing the damage to the resonator due to the process.

[0084] Embodiment 3. Fig. 13 is a longitudinal sectional view of a module to which the elastic wave device 1 according to Embodiment 1 or 2 is applied. Note that the same reference numerals are given to the same or corresponding parts as those in Embodiment 1 or 2. The description of that part is omitted.

[0085] In Fig. 13, the module 100 includes a package substrate 130, a plurality of external connection terminals 131, an integrated circuit component IC, an elastic wave device 1, an inductor 111, and a sealing portion 117.

[0086] The plurality of external connection terminals 31 are formed on the lower surface of the package substrate 130. The plurality of external connection terminals 131 are mounted on a mother board of a preset mobile communication terminal.

[0087] For example, the integrated circuit component IC is mounted inside the package substrate 130. The integrated circuit component IC includes a switching circuit and a low-noise amplifier.

[0088] The surface acoustic wave device 1 is mounted on the main surface of the package substrate 130.

[0089] The inductor 111 is mounted on the main surface of the package substrate 130. The inductor 111 is mounted for impedance matching. For example, the inductor 111 is an Integrated Passive Device (IPD).

[0090] The sealing portion 117 seals a plurality of electronic components including the surface acoustic wave device 1.

[0091] The module 100 described above includes the surface acoustic wave device 1. Therefore, it is possible to provide a module using a surface acoustic wave device with suppressed transverse mode spurious while reducing the processes after resonator formation and reducing the damage to the resonator due to the processes.

[0092] Although some aspects of at least one embodiment have been described, it should be understood that various modifications, corrections, and improvements will be readily apparent to those skilled in the art. Such modifications, corrections, and improvements are intended to be part of this disclosure and are intended to be within the scope of this disclosure.

[0093] It should be understood that the embodiments of the methods and apparatuses described herein are not limited to the details of the structures and arrangements of the components described in the above description or illustrated in the accompanying drawings. The methods and apparatuses can be implemented in other embodiments and can be implemented or executed in various manners.

[0094] The specific implementation examples are given here for illustrative purposes only and are not intended to be limiting.

[0095] The expressions and terms used in this disclosure are for illustrative purposes and should not be construed as limiting. The use of "including", "comprising", "having", "containing" and their variants herein means the inclusion of the items listed hereinafter, their equivalents and additional items.

[0096] References to "or (alternatively)" can be construed such that any term described using "or (alternatively)" indicates one, more than one, and all of the terms of the description.

[0097] References to front, back, left, right, top, bottom, vertical, horizontal, front, and back are all for the convenience of description. Such references do not limit the components of the present disclosure to any one positional or spatial orientation. Therefore, the above description and drawings are merely illustrative.

Description of Reference Numerals

[0098] 1 Elastic Wave Device, 3 Package Substrate, 5 Device Chip, 17 Sealing Portion 11 Piezoelectric Substrate, 12 High-Speed Sound Film Layer, 13 Spurious Absorption Layer 14 Temperature Characteristic Improvement Layer, 20 Support Substrate, 50 Elastic Wave Element 100 Module, 111 Inductor, 117 Sealing Portion 130 Package Substrate

Claims

1. A piezoelectric substrate, a resonator formed on a main surface of the piezoelectric substrate, a spurious absorption layer formed on another main surface of the piezoelectric substrate, a high sound velocity film layer formed between the piezoelectric substrate and the spurious absorption layer and having a higher sound velocity than the piezoelectric substrate, and the spurious absorption layer is composed of a tetragonal crystal substrate, and an elastic wave device having a slower sound velocity than the piezoelectric substrate.

2. The elastic wave device according to claim 1, further comprising a temperature characteristic improvement layer formed between the piezoelectric substrate and the spurious absorption layer.

3. The thickness of the spurious absorption layer is 3λ or more and 20λ or less, where λ is the wavelength of the wave of the main mode excited by the resonator, and a support substrate is provided on the main surface of the spurious absorption layer opposite to the piezoelectric substrate. The elastic wave device according to claim 1.

4. The elastic wave device according to claim 1, wherein the thickness of the high sound velocity film layer is smaller than the thickness of the piezoelectric substrate.

5. The elastic wave device according to claim 2, wherein the thickness of the high sound velocity film layer is smaller than the thickness of the temperature characteristic improvement layer.

6. The elastic wave device according to claim 1, wherein the thickness of the high sound velocity film layer is 0.1λ or more and 0.3λ or less, where λ is the wavelength of the wave of the main mode excited by the resonator.

7. The elastic wave device according to claim 1, wherein the spurious absorption layer has a lower crystal density than the piezoelectric substrate.

8. The spurious absorption layer is Li ２ B ４ O ７ The elastic wave device according to claim 1, wherein the single crystal substrate is

9. The elastic wave device according to claim 1, wherein the support substrate is a substrate made of sapphire, silicon, alumina or spinel.

10. The cut angle of the main surface of the spurious absorption layer is such that the Euler angles (φ, θ, ψ) are φ = 0° ± 2° or 90° ± 2°, θ = 90° ± 2°, ψ = 80° to 100°. The elastic wave device according to claim 1.

11. A module comprising the elastic wave device according to any one of claims 1 to 10.

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