Elastic wave devices

Abstract

[Problem] To provide an acoustic wave device that exhibits good characteristics in ultra-high frequency bands of 6 GHz or above using overtones. [Solution] The acoustic wave device comprises a piezoelectric substrate 11, an electrode 12 provided in contact with the piezoelectric substrate 11, and an acoustic multilayer film 13 provided in contact with the piezoelectric substrate 11 and / or the electrode 12. The acoustic wave device is configured to utilize an overtone, among the resonance characteristics of a surface acoustic wave. The electrode 12 includes an interdigital electrode 12a provided on one surface of the piezoelectric substrate 11. Preferably, the surface acoustic wave of the overtone has an acoustic velocity of greater than or equal to 9000 m / s. Preferably, the acoustic multilayer film 13 comprises a low-acoustic impedance film 13a and a high-acoustic impedance film 13b that are alternately stacked.

Description

[Technical Field]

[0001] This invention relates to an elastic wave device. [Background technology]

[0002] The 700MHz to 3GHz frequency band, primarily used by smartphones and other devices, comprises nearly 80 bands and is extremely congested. To address this, the 5th generation mobile communication system (5G) is utilizing the 3.3GHz to 4.9GHz frequency band, and plans are underway for the next generation to use frequency bands above 6GHz.

[0003] Conventionally, in the frequency band from 700 MHz to 3 GHz, bulk acoustic resonator (FBAR; Film Bulk Acoustic Resonator) devices using piezoelectric thin films of AlN or ScAlN (see, for example, Non-Patent Document 1 or 2), or surface acoustic wave (SAW) devices and longitudinal leakage acoustic wave (LLSAW) devices using LiNbO3 crystals (LN) or LiTaO3 crystals (LT) as the piezoelectric substrate or thin film have been used (see, for example, Non-Patent Document 3 or 4). In surface acoustic wave (SAW) devices, the bandwidth depends on the electromechanical coupling coefficient (coupling coefficient) of the piezoelectric substrate used, so LN or LT substrates with the coupling coefficient required for that bandwidth are generally used.

[0004] In FBAR devices, since AlN and ScAlN films are c-axis oriented, the only bulk wave vibration mode used is thickness longitudinal vibration. The sound velocity of this longitudinal wave is (c33 D / density) 1 / 2 It is represented by (c33 D (where is the elastic stiffness constant), and the excitation frequency is the value expressed as sound velocity / (2 × film thickness), minus the frequency drop due to the mass load on the electrodes. For this reason, in order to make the excitation frequency high, the thickness of the piezoelectric thin film must be made extremely thin. However, when using AlN or ScAlN as piezoelectric thin films, these are polycrystalline thin films, so the attenuation at ultra-high frequencies is large, making it difficult to achieve good characteristics.

[0005] Furthermore, in surface acoustic wave (SAW) devices using LN or LT as piezoelectric substrates, the frequency f is determined by f = V / λ, where V is the speed of sound in the substrate and λ is the period (wavelength) of the lattice-like electrode. Due to power handling capacity and variations in the manufacturing process, the wavelength of the lattice-like electrode is limited to about 1.2 μm. Therefore, in relation to the speed of sound in the substrate used, the frequency limit on the high-frequency side was approximately 3.2 GHz.

[0006] When a piezoelectric film such as ZnO is formed on a high-sound-velocity substrate such as sapphire, the Rayleigh wave (0th order), its higher-order mode Sezawa wave (1st order), and even higher-order modes (2nd, 3rd, ...) are excited according to the thickness of the piezoelectric film. However, the frequencies of these higher-order modes are not integer multiples of the frequency of the fundamental mode. On the other hand, in the thickness oscillation of bulk waves, in addition to the fundamental mode, overtones with frequencies that are integer multiples of approximately 2, 3, ... (harmonic frequencies) are excited. In this way, SAWs excited at approximately 2, 3, ... frequencies of the fundamental mode will also be referred to as overtones.

[0007] Furthermore, among the plate waves described later, the zero-order mode (A0 mode) of the asymmetric Lamb wave slows down as the substrate thickness decreases, but its higher-order first-order mode, the A1 mode, conversely becomes faster, and the ratio between them varies greatly depending on the thickness of the piezoelectric substrate. Moreover, the two are not related by integer multiples. As with the Sezawa wave mentioned above, the A1 mode is a higher-order mode of the A0 mode and is not an overtone.

[0008] As mentioned above, SAW devices are limited to approximately 3.2 GHz on the high-frequency side, but there are reports of high-frequency devices exceeding 3.2 GHz using plate waves other than SAW. Plate waves include Lamb waves in A0, A1, and S0 modes, which have a longitudinal component and a displacement of the shear vertical (SV) component, and SH-type plate waves in SH0 mode, which have a shear horizontal (SH) component. These plate waves propagate by vibrating throughout the entire substrate, which is significantly different from SAW, where propagation is concentrated on the substrate surface, and plate waves and SAW are used separately.

[0009] When the thickness of the piezoelectric substrate is 0.15 times the wavelength or less, a high sound velocity of 6,000 m / s, approximately 1.5 times that of SAW, can be obtained in S0 mode, and a high sound velocity of 12,000 to 25,000 m / s, approximately 3 to 6 times that of SAW, can be obtained in A1 mode, which is advantageous for realizing high-frequency devices. Therefore, resonant devices of 4.5 to 6.3 GHz have been realized using the A1 mode fundamental wave in LN or LT thin films of 0.34 to 0.48 μm (see, for example, Non-Patent Documents 5 or 6). However, this device requires cavities both above and below the IDT portion on the piezoelectric thin plate that excites the plate wave, and therefore, there is a major problem of weak mechanical strength in thin plates of 0.48 μm or less.

[0010] Therefore, in order to solve the problem of the weak mechanical strength of this plate wave, a structure has been proposed that does not require a cavity below the piezoelectric plate by using an acoustic multilayer film in contact with the piezoelectric plate, and that excites the fundamental modes of the plate wave in A1 mode, S0 mode, and SH0 mode (see, for example, Non-Patent Document 7 or Patent Document 1), or that uses the fundamental mode of the SH0 mode plate wave (see, for example, Patent Document 2). In addition, a structure using LN or LT and the fundamental mode of LLSAW has also been proposed (see, for example, Patent Document 3). [Prior art documents] [Non-patent literature]

[0011] [Non-Patent Document 1] John D. Larson III et al., “Power Handling and Temperature Coefficient Studies in FBAR Duplexers for the 1900 MHz PCS Band”, Proc. IEEE Ultrason. Symp., 2000, p.869-874 [Non-Patent Document 2] Keiichi Umeda et al., “PIEZOELECTRIC PROPERTIES OF ScAlN THIN FILMS FOR PIRZO-MEMS DEVICES”, Proc. MEMS (Taipei, Taiwan), 2013, p.20-24, [Non-Patent Document 3] M. Kadota, Y. Ishii, T. Shimatsu, M. Umoto, and Shuji Tanaka, “Suprious-Free, Near-Zero-TCF Hetero Acoustic Layer (HAL) SAW Resonators Using LiTaO3 Thin Plate on Quartz”, Proc. IEEE Ultrason. Symp., 2018, 6J-2 [Non-Patent Document 4] T. Kimura, Y. Kishimoto, M. Omura and K. Hashimoto, “3.5 GHz longitudinal leaky surface acoustic wave resonator using a multilayered waveguide structure for high acoustic energy confinement”, Jpn. J. Appl. Phys., 2018, vol. 57, 07LD15 [Non-Patent Document 5] M. Kadota, T. Ogami, K. Yamamoto, H. Tochishita, and Y. Negoro, “High frequency Lamb Wave Device composed of MEMS Structure using LiNbO3 Thin Film and Air Gap”, IEEE trans. Ultrason. Ferroelec. Freq. Cont., 2010, vol.57, No.11, p.2564-2571 [Non-Patent Document 6] N. Assila, M. Kadota, and S. Tanaka, “High Frequency Resonator Using A1 Mode Lamb Wave in LiTaO3 Plate”, IEEE trans. Ultrason. Ferroelec. Freq. Cont., 2019, vol. 66, No. 9, p. 1529-1535 [Non-Patent Document 7] T. Kimura, K. Daimon, T. Ogami and M. Kadota, “S0 Mode Lamb Wave Resonators Using Thin Plate LiNbO3 and Acoustic Quarter-Wave Multilayers”, Jpn. J. Appl. Phys., 2013, vol. 52, 07HD03 [Non-Patent Document 8] Yasutaka Shimizu, “Directional Characteristics of Elastic Surface Wave Propagation on LiTaO3 Substrate”, Journal of the Acoustical Society of Japan, 1980, vol. 36, p. 140-145 [Patent Document]

[0012] [Patent Document 1] Japanese Patent No. 5648695 [Patent Document 2] International Publication WO2016 / 047255 [Patent Document 3] Japanese Unexamined Patent Application Publication No. 2018-182615 [Summary of the Invention] [Problems to be Solved by the Invention]

[0013] FBAR devices, as described in Non-Patent Documents 1 and 2, have the problem of not being able to obtain good characteristics with a large impedance ratio in the ultra-high frequency band of 6 GHz or higher. Furthermore, as described in Non-Patent Documents 3 or 4, conventional devices using surface acoustic waves (SAW) or longitudinal leakage acoustic waves (LLSAW) have the problem that, in structures in which a curtain-like electrode (IDT) is formed on a piezoelectric thin film, only the fundamental mode is excited, and even in structures combining a piezoelectric thin film and a support substrate, or an acoustic multilayer film and a support substrate, overtones with frequencies that are integer multiples of the fundamental mode are not excited, and the high-frequency side has the problem of being limited to a resonant frequency of 3.5 GHz.

[0014] In the device described in Patent Document 1, the A1 mode plate wave has a sound velocity of 15,500 m / s, determined by the anti-resonance frequency of the fundamental mode. However, this sound velocity is that of the fundamental mode of the A1 mode plate wave, not the sound velocity of the overtone. Furthermore, in the devices described in Non-Patent Documents 5, 6, and 7, the sound velocity of the S0 mode of LiNbO3 (LN) and LiTaO3 (LT) is 6,000 to 7,000 m / s regardless of the azimuth angle and substrate thickness. However, this also has the problem that it does not utilize the overtone. Although the sound velocity is not specified for the SH0 mode plate wave devices described in Patent Documents 1 and 2, in the devices described in Non-Patent Documents 5, 6, and 7, the sound velocity of the SH0 mode plate wave of LN and LT is approximately 4,000 m / s, regardless of the azimuth angle and substrate thickness.

[0015] The device described in Patent Document 3 uses Al electrodes with thicknesses of 0.05, 0.06, and 0.08 wavelengths to excite LLSAW, but there was a problem that the overtone could not be sufficiently excited with these Al electrode thicknesses. In the device described in Patent Document 3, the sound velocity of the fundamental mode of LLSAW is approximately 6,000 m / s.

[0016] This invention addresses these challenges and aims to provide an elastic wave device that can obtain good characteristics in the ultra-high frequency band of 6 GHz or higher by using overtones. [Means for solving the problem]

[0017] To achieve the above objective, the elastic wave device according to the present invention comprises a piezoelectric substrate, an electrode provided in contact with the piezoelectric substrate, and the piezoelectric substrate Itama The device comprises an acoustic multilayer film provided in contact with the electrode, wherein the acoustic multilayer film excites the overtones among the resonance characteristics of surface acoustic waves and utilizes the overtones.

[0018] The elastic wave device according to the present invention can excite overtones of approximately integer multiples (approximately 2 times, approximately 3 times, ...) of the frequency of the fundamental mode of a surface acoustic wave using an acoustic multilayer film. Furthermore, by adjusting the thickness of the electrodes, the type of piezoelectric substrate, and the thickness of each layer of the acoustic multilayer film, an overtone of a surface acoustic wave with a large impedance ratio can be obtained. By utilizing this overtone, the elastic wave device according to the present invention can obtain good characteristics with a large impedance ratio in the ultra-high frequency band of 6 GHz or higher. The surface acoustic wave of this overtone corresponds, for example, to a sound velocity of 9000 m / s or more, and in some cases to 10000 m / s or more.

[0019] Here, the impedance ratio of the elastic wave device is the ratio of the resonant impedance Zr at the resonant frequency fr to the anti-resonant impedance Za at the anti-resonant frequency fa [20 × log(Za / Zr)]. The bandwidth of the elastic wave device is (fa - fr) / fr.

[0020] In the elastic wave device according to the present invention, it is preferable that the acoustic multilayer film is made up of alternating layers of low acoustic impedance film and high acoustic impedance film. In particular, it is preferable that the acoustic multilayer film has an acoustic film in which low acoustic impedance film and high acoustic impedance film are alternately layered in 3 to 20 layers. In this case, it is preferable that the thickness of at least three layers of each low acoustic impedance film and each high acoustic impedance film of the acoustic multilayer film is, respectively, 0.012 to 0.118 wavelengths, 0.105 to 0.2 wavelengths, or 0.216 to 0.275 wavelengths of the surface acoustic wave. It is even more preferable that it is 0.015 to 0.117 wavelengths, 0.105 to 0.19 wavelengths, or 0.22 to 0.27 wavelengths. It is even more preferable that it is 0.02 to 0.12 wavelengths, 0.114 to 0.172 wavelengths, or 0.225 to 0.26 wavelengths. Furthermore, it is even more preferable that the wavelengths are between 0.03 and 0.082 wavelengths. Moreover, among the combinations of the low-acoustic impedance film and the high-acoustic impedance film of the acoustic multilayer film, it is more preferable that the thickness of either film be between 0.012 and 0.118 wavelengths, or between 0.02 and 0.12 wavelengths, or between 0.03 and 0.082 wavelengths. This allows for efficient excitation of surface acoustic wave overtones.

[0021] In the elastic wave device according to the present invention, each low-acoustic impedance film and / or each high-acoustic impedance film of the acoustic multilayer film is made of Mg alloy, SiO2, SiOF, Al, Y, Si, Ge, Ti, ZnO, Si x N y(where x and y are positive real numbers), preferably the film consists of at least one of AlN, SiC, Al2O3, Ag, ZrO2, Hf, Cu, TiO2, Cr, Ni, Au, Ta, Mo, Pt, and W, or an oxide film, nitride film, carbide film, or iodide film containing at least one of these. Otherwise, the low acoustic impedance film only needs to have a lower acoustic impedance than the adjacent high acoustic impedance film. In the elastic wave device according to the present invention, the longitudinal acoustic impedance Zl and transverse acoustic impedance Zs of each low acoustic impedance film and each high acoustic impedance film are (density × c33), respectively. 1 / 2 and (density × c44) 1 / 2 It is expressed as follows (c33 and c44 are elastic stiffness constants). Of the two acoustic membranes used, the one with the smaller Z1 or Zs is the low acoustic impedance membrane, and the one with the larger Z1 is the high acoustic impedance membrane.

[0022] In the elastic wave device according to the present invention, the piezoelectric substrate is preferably made of a single crystal of LiNbO3 or LiTaO3. In this case, it is easier to excite the overtones of surface acoustic waves.

[0023] In order to obtain a large impedance ratio, the elastic wave device according to the present invention has electrodes consisting of a curtain-like electrode provided on one surface of the piezoelectric substrate, and the acoustic multilayer film is provided so as to be in contact with the other surface of the piezoelectric substrate. The piezoelectric substrate is made of LiNbO3 crystal and preferably has an Euler angle of one of (-30°~30°, 60°~103°, -15°~15°) and (90°±6°, 90°±6°, -20°~48°), or an Euler angle that is crystallographically equivalent to either of these. In this case, it is even more preferable that the piezoelectric substrate has an Euler angle of one of (-30°~30°, 72°~97°, -15°~15°) and (90°±6°, 90°±6°, -10°~43°), or an Euler angle that is crystallographically equivalent to either of these. Furthermore, in this case, it is even more preferable that the piezoelectric substrate has an Euler angle of either (-30°~30°, 78°~92°, -6°~6°) or (90°±6°, 90°±6°, -2°~33°), or an Euler angle that is crystallographically equivalent to either of these.

[0024] In order to obtain a large impedance ratio, the elastic wave device according to the present invention has electrodes comprising a curtain-like electrode provided on one surface of the piezoelectric substrate and a floating electrode provided to cover the other surface of the piezoelectric substrate, the acoustic multilayer film is provided so as to be in contact with the surface of the floating electrode opposite to the piezoelectric substrate, and the piezoelectric substrate is made of LiNbO3 crystal and preferably has an Euler angle of one of (-30°~30°, 64°~98°, -15°~15°) and (90°±6°, 90°±6°, -4°~56°), or an Euler angle crystallographically equivalent to either of these. Furthermore, in this case, it is more preferable that the piezoelectric substrate has an Euler angle of one of (-30°~30°, 68°~95°, -15°~15°) and (90°±6°, 90°±6°, -2°~52°), or an Euler angle crystallographically equivalent to either of these. Furthermore, in this case, it is even more preferable that the piezoelectric substrate has an Euler angle of either (-30°~30°, 72°~92°, -15°~15°) or (90°±6°, 90°±6°, 25°~50°), or an Euler angle that is crystallographically equivalent to either of these. The floating electrode may be connected to one electrode of the curtain-like electrode, or to another common electrode other than the elastic wave device according to the present invention.

[0025] When the piezoelectric substrate is made of LiNbO3 crystal, the thickness of the piezoelectric substrate is preferably 0.002 to 5 wavelengths of the surface acoustic wave, more preferably 1.2 wavelengths or less, and even more preferably 0.02 to 0.3 wavelengths. In this case, a larger impedance ratio can be obtained.

[0026] In order to obtain a large impedance ratio, the elastic wave device according to the present invention preferably has electrodes consisting of a curtain-like electrode provided on one surface of the piezoelectric substrate, and the acoustic multilayer film provided in contact with the other surface of the piezoelectric substrate, and the piezoelectric substrate is made of LiTaO3 crystal and preferably has an Euler angle of any one of (-30°~30°, 55°~100°, -15°~15°), (90°±6°, 90°±6°, -5°~61°), and (90°±6°, 90°±6°, 83°~93°), or an Euler angle crystallographically equivalent to any one of these. Furthermore, in this case, it is more preferable that the piezoelectric substrate has an Euler angle of one of the following: (-30°~30°, 61°~95°, -15°~15°), (90°±6°, 90°±6°, 15°~55°), and (90°±6°, 90°±6°, 85°~91°), or an Euler angle that is crystallographically equivalent to one of these. Furthermore, in this case, it is more preferable that the piezoelectric substrate has an Euler angle of one of the following: (-30°~30°, 70°~89°, -15°~15°), and (90°±6°, 90°±6°, 23°~38°), or an Euler angle that is crystallographically equivalent to one of these.

[0027] In the elastic wave device according to the present invention, in order to obtain a large impedance ratio, the electrode has a grating electrode provided on one surface of the piezoelectric substrate and a floating electrode provided so as to cover the other surface of the piezoelectric substrate. The acoustic multilayer film is provided so as to contact the surface of the floating electrode opposite to the piezoelectric substrate. The piezoelectric substrate is made of LiTaO3 crystal, and the Euler angles are preferably either (-30° to 30°, 65° to 94°, -15° to 15°) and (90° ± 6°, 90° ± 6°, -4° to 56°), or Euler angles crystallographically equivalent to any one of these. In this case, more preferably, the piezoelectric substrate has Euler angles of either (-30° to 30°, 69° to 91°, -15° to 15°) and (90° ± 6°, 90° ± 6°, -2° to 52°), or Euler angles crystallographically equivalent to any one of these. In this case, even more preferably, the piezoelectric substrate has Euler angles of (90° ± 6°, 90° ± 6°, 25° to 50°), or Euler angles crystallographically equivalent thereto. Note that the floating electrode may be connected to one electrode of the grating electrode or another common electrode other than the elastic wave device according to the present invention.

[0028] When the piezoelectric substrate is made of LiTaO3 crystal, the thickness of the piezoelectric substrate is preferably 0.002 to 2.4 wavelengths of the elastic surface wave, more preferably 1 wavelength or less, and even more preferably 0.02 to 0.25 wavelengths. In this case, a larger impedance ratio can be obtained.

[0029] In the elastic wave device according to the present invention, for the grating electrode, when the metallization ratio is MR and the wavelength of the elastic surface wave is λ, the density is 1800 kg / m 3 or more and 6000 kg / m 3 or less, and the thickness is (0.01λ to 0.045λ) × 0.5 / MR or (0.1λ to 0.21λ) × 0.5 / MR, or the density is 6000 kg / m​​​Less than , with a thickness of (0.01λ~0.033λ)×0.5 / MR or (0.06λ~0.2λ)×0.5 / MR, or a density of 10,000 kg / m³ 3 More than 15000kg / m 3 Less than , with a thickness of (0.008λ~0.03λ)×0.5 / MR or (0.055λ~0.19λ)×0.5 / MR, or a density of 15000 kg / m³ 3 More than 25000kg / m 3 Preferably, the thickness is less than (0.005λ~0.02λ)×0.5 / MR or (0.062λ~0.165λ)×0.5 / MR. In this case, a larger impedance ratio can be obtained. The metallization ratio (MR) of the wire mesh electrode (IDT) is the ratio obtained by dividing the width F of the electrode fingers of the wire mesh electrode by half of the period (λ) of the electrode fingers (the sum of the width F of the electrode fingers and the gap G between the electrode fingers), along the propagation direction of the surface acoustic wave, and MR = F / (F+G) = 2×F / λ. Also, the period (wavelength) λ of the electrode fingers of the wire mesh electrode is equal to the wavelength of the surface acoustic wave used.

[0030] Here, the Euler angles (φ, θ, ψ) are in a right-handed system and represent the cross-section of the piezoelectric substrate and the direction of elastic wave propagation. Specifically, with respect to the crystal axes X, Y, and Z of the crystal constituting the piezoelectric substrate, or the LT or LN, the X axis is rotated counterclockwise by φ with the Z axis as the axis of rotation to obtain the X' axis. Next, the Z axis is rotated counterclockwise by θ with the X' axis as the axis of rotation to obtain the Z' axis. At this time, the Z' axis is taken as the normal, and the plane containing the X' axis is taken as the cross-section of the piezoelectric substrate. Furthermore, the direction obtained by rotating the X' axis counterclockwise by ψ with the Z' axis as the axis of rotation is taken as the direction of elastic wave propagation. In addition, the axis perpendicular to the X' and Z' axes, obtained by the movement of the Y axis due to these rotations, is taken as the Y' axis.

[0031] By defining the Euler angle in this way, according to Non-Patent Literature 8, the following relationship holds for LN and LT belonging to the 3m point group of the trigonal system. (φ, θ, ψ)=(60°+φ, -θ, ψ)=(60°-φ, -θ, 180°-ψ) =(φ, 180°+θ, 180°-ψ)=(φ, θ, 180°+ψ) For example, propagation in the X direction of a 40° rotated Y plate is represented by Euler angles (0°, 130°, 0°), and propagation in the X direction of a 40° rotated Y plate at 90° is represented by Euler angles (0°, 130°, 90°). Note that when cutting a piezoelectric substrate to the desired Euler angles, there is a possibility of errors of up to ±0.5° for each component of the Euler angles. Regarding the characteristics of elastic waves, for the Euler angles (φ, θ, ψ), there is almost no difference in characteristics due to deviations of about ±5° for φ and ψ. Also, (0°, θ+360°, 0°) is an equivalent plane in terms of Euler angles to (0°, θ, 0°). On the other hand, (0°, θ+180°, 0°) is not an equivalent plane in terms of Euler angles to (0°, θ, 0°), but it is the front and back of the substrate. However, since elastic wave devices exhibit the same characteristics on both the front and back sides, the orientation of the front and back of the substrate is also considered equivalent to the same surface. [Effects of the Invention]

[0032] According to the present invention, it is possible to provide an elastic wave device that can obtain good characteristics in the ultra-high frequency band of 6 GHz or higher by using overtones. [Brief explanation of the drawing]

[0033] [Figure 1] (a) A side view of an elastic wave device according to an embodiment of the present invention, and (b) A side view showing a modified example having a floating electrode. [Figure 2] (a) A side view of a conventional elastic wave device, and (b) a graph showing its frequency characteristics. [Figure 3](a) A graph showing the frequency characteristics of the elastic wave device shown in Figure 1(a) with a structure of Cu(0.1λ thickness) / (90°,90°,35°)LT(0.2λ thickness) / SiO2(0.25λ thickness) / Ta(0.25λ thickness) / SiO2(0.25λ thickness) / Ta(0.25λ thickness) / SiO2(0.25λ thickness) / Ta(0.25λ thickness) / Si substrate (thickness is omitted below). (b) A graph showing the frequency characteristics of the elastic wave device shown in Figure 1(b) with a structure of Cu(0.1λ) / (90°,90°,42.5°)LN(0.2λ) / floating electrode / SiO2(0.05λ) / Ta / SiO2(0.05λ) / Ta / SiO2(0.05λ) / Ta / Si substrate when the thickness of the Ta film is changed. [Figure 4] (a) Frequency characteristics of the elastic wave device shown in Figure 1(a) with a Cu(0.2λ) / (0°,85°,0°)LN(0.2λ) / Al(0.06λ) / W(0.06λ) / Al(0.06λ) / W(0.06λ) / Al(0.06λ) / W(0.06λ) / Si substrate structure, (b) Frequency characteristics of the elastic wave device shown in Figure 1(b) with a Cu(0.1λ) / (90°,90°,42.5°)LN(0.2λ) / floating electrode / SiO2(0.05λ) / Ta(0.03λ) / SiO2(0.05λ) / Ta(0.03λ) / SiO2(0.05λ) / Ta(0.03λ) / Si substrate structure, (c) Figure 1 (a) is a graph showing the frequency characteristics of the elastic wave device shown in Figure 1(b) with a Cu(0.12λ) / (0°,85°,0°)LT(0.15λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Si substrate structure, and (d) is a graph showing the frequency characteristics of the elastic wave device shown in Figure 1(b) with a Cu(0.1λ) / (90°,90°,35°)LT(0.15λ) / floating electrode / SiO2(0.07λ) / Ta(0.07λ) / SiO2(0.07λ) / Ta(0.07λ) / SiO2(0.07λ) / Ta(0.07λ) / Si substrate structure. [Figure 5]Figure 1(a) shows a graph illustrating the relationship between (a) bandwidth, (b) impedance ratio, and Euler angle θ for an elastic wave device with a Cu(0.1λ) / (0°,θ,0°)LN(0.2λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Si substrate structure. [Figure 6] Figure 1(a) is a graph showing the relationship between the impedance ratio and the Euler angle φ for the elastic wave device with a Cu(0.1λ) / (φ,85°,0°)LN(0.2λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Si substrate structure. [Figure 7] Figure 1(a) is a graph showing the relationship between the impedance ratio and the Euler angle ψ for the elastic wave device with a Cu(0.1λ) / (0°,85°,ψ)LN(0.2λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Si substrate structure. [Figure 8] Figure 1(a) shows a graph illustrating the relationship between the impedance ratio and (a) the W film thickness of the high acoustic impedance film and (b) the Al film thickness of the low acoustic impedance film, for the structure of the elastic wave device with a Cu(0.1λ) / (0°,85°,0°)LN(0.2λ) / Al / W / Al / W / Al / W / Si substrate. [Figure 9] Figure 1(b) shows a graph illustrating the relationship between (a) bandwidth, (b) impedance ratio, and Euler angle θ for an elastic wave device with the structure Cu(0.1λ) / (0°,θ,0°)LN(0.2λ) / floating electrode / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Si substrate. [Figure 10]Figure 1(b) shows a graph illustrating the relationship between the impedance ratio and (a) the W film thickness of the high acoustic impedance film at an Al film thickness of 0.05λ, and (b) the Al film thickness of the low acoustic impedance film at a W film thickness of 0.05λ, for the elastic wave device with a Cu(0.1λ) / (0°,85°,0°)LN(0.2λ) / floating electrode / Al / W / Al / W / Al / W / Si substrate structure, as well as (a) the W film thickness of the high acoustic impedance film at an Al film thickness of 0.05λ. [Figure 11] Figure 1(a) shows a graph illustrating the relationship between (a) bandwidth, (b) impedance ratio, and Euler angle ψ for an elastic wave device with a Cu(0.1λ) / (90°,90°,ψ)LN(0.2λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Si substrate structure. [Figure 12] Figure 1(a) shows a graph illustrating the relationship between the impedance ratio of the elastic wave device with a Cu(0.1λ) / (90°,90°,42.5°)LN(0.2λ) / Al / W / Al / W / Al / W / Si substrate structure and (a) the W film thickness of the high acoustic impedance film at an Al film thickness of 0.05λ, and (b) the Al film thickness of the low acoustic impedance film at a W film thickness of 0.05λ. [Figure 13] Figure 1(b) shows a graph illustrating the relationship between (a) bandwidth, (b) impedance ratio, and Euler angle ψ for an elastic wave device with the structure Cu(0.1λ) / (90°,90°,ψ)LN(0.2λ) / floating electrode / SiO2(0.05λ) / Ta(0.05λ) / SiO2(0.05λ) / Ta(0.05λ) / Si substrate. [Figure 14] Figure 1(b) shows a graph illustrating the relationship between the impedance ratio and the Ta film thickness of the high acoustic impedance film at a Ta film thickness of 0.05λ, and the SiO2 film thickness of the low acoustic impedance film at a Ta film thickness of 0.05λ, respectively, for the elastic wave device with a Cu(0.1λ) / (90°,90°,42.5°)LN(0.2λ) / floating electrode / SiO2 / Ta / SiO2 / Ta / SiO2 / Ta / Si substrate structure shown in Figure 1(b). [Figure 15]Figure 1(a) shows a graph illustrating the relationship between (a) bandwidth, (b) impedance ratio, and Euler angle θ for an elastic wave device with a Cu(0.1λ) / (0°,θ,0°)LT(0.15λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Si substrate structure. [Figure 16] Figure 1(a) shows a graph illustrating the relationship between the impedance ratio and the structure of the elastic wave device with a Cu(0.1λ) / (0°,85°,0°)LT(0.15λ) / Al / W / Al / W / Al / W / Si substrate, (a) the W film thickness of the high acoustic impedance film at an Al film thickness of 0.05λ, and (b) the Al film thickness of the low acoustic impedance film at a W film thickness of 0.05λ. [Figure 17] Figure 1(b) shows a graph illustrating the relationship between (a) bandwidth, (b) impedance ratio, and Euler angle θ for the structure of the elastic wave device shown, specifically the Cu(0.1λ) / (0°,θ,0°)LT(0.15λ) / floating electrode / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Si substrate and the Cu(0.1λ) / (0°,θ,0°)LT(0.15λ) / floating electrode / SiO2(0.05λ) / Ta(0.05λ) / SiO2(0.05λ) / Ta(0.05λ) / SiO2(0.05λ) / Ta(0.05λ) / Si substrate. [Figure 18] Figure 1(b) shows a graph illustrating the relationship between the impedance ratio and (a) the W film thickness of the high acoustic impedance film at an Al film thickness of 0.05λ and (b) the Al film thickness of the low acoustic impedance film at a W film thickness of 0.05λ for the elastic wave device shown in Figure 1(b). [Figure 19] Figure 1(a) shows a graph illustrating the relationship between (a) bandwidth, (b) impedance ratio, and Euler angle ψ for an elastic wave device with a Cu(0.1λ) / (90°,90°,ψ)LT(0.15λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Si substrate structure. [Figure 20] Figure 1(a) shows a graph illustrating the relationship between the impedance ratio and (a) the W film thickness of the high acoustic impedance film at an Al film thickness of 0.05λ, and (b) the Al film thickness of the low acoustic impedance film at a W film thickness of 0.05λ, for the elastic wave device with a Cu(0.1λ) / (90°,90°,35°)LT(0.15λ) / Al / W / Al / W / Al / W / Si substrate structure, as well as the Al film thickness at a W film thickness of 0.05λ. [Figure 21] Figure 1(b) shows a graph illustrating the relationship between (a) bandwidth, (b) impedance ratio, and Euler angle ψ for an elastic wave device with the structure Cu(0.1λ) / (90°,90°,ψ)LT(0.15λ) / floating electrode / SiO2(0.05λ) / Ta(0.05λ) / SiO2(0.05λ) / Ta(0.05λ) / Si substrate. [Figure 22] Figure 1(b) shows a graph illustrating the relationship between the impedance ratio and the Ta film thickness of the high acoustic impedance film at a Ta film thickness of 0.05λ at a Ta film thickness of 0.05λ, and the relationship between the impedance ratio and the structure of the elastic wave device with a Cu(0.1λ) / (90°,90°,35°)LT(0.15λ) / floating electrode / SiO2 / Ta / SiO2 / Ta / SiO2 / Ta / Si substrate, as shown in (a) and (b) the SiO2 film thickness of the low acoustic impedance film at a Ta film thickness of 0.05λ. [Figure 23] Figure 1(b) is a graph showing the relationship between the impedance ratio and the thickness of the piezoelectric substrate (plate thickness) for the elastic wave device structure shown in Figure 1(b), specifically for the Cu(0.1λ) / (90°,90°,42.5°)LN(0.2λ) / floating electrode / SiO2(0.05λ) / Ta(0.05λ) / SiO2(0.05λ) / Ta(0.05λ) / SiO2(0.05λ) / Ta(0.05λ) / Si substrate structure, and for the Cu(0.1λ) / (90°,90°,35°)LT(0.15λ) / floating electrode / SiO2(0.05λ) / Ta(0.05λ) / SiO2(0.05λ) / Ta(0.05λ) / SiO2(0.05λ) / Ta(0.05λ) / Si substrate structure. [Figure 24]Figure 1(b) is a graph showing the relationship between the impedance ratio and the number of acoustic film layers for an elastic wave device with the structure Cu(0.1λ) / (90°,90°,35°)LT(0.15λ) / floating electrode / SiO2(0.05λ) / Ta(0.05λ) / SiO2(0.05λ) / Ta(0.05λ) / Si substrate. [Figure 25] Figure 1(b) is a graph showing the relationship between the impedance ratio and the thickness of each lattice electrode (electrode thickness) at MR=0.5 for the elastic wave device with the structure of a lattice electrode / (90°,90°,35°)LT(0.15λ) / floating electrode / SiO2(0.05λ) / Ta(0.05λ) / SiO2(0.05λ) / Ta(0.05λ) / Si substrate. [Figure 26] Figure 1(b) is a graph showing the relationship between the impedance ratio and the metallization ratio of the lattice-like electrode for the elastic wave device structure shown in Figure 1(b), specifically for the Cu(0.1λ) / (90°,90°,42.5°)LN(0.2λ) / floating electrode / SiO2(0.05λ) / Ta(0.05λ) / SiO2(0.05λ) / Ta(0.05λ) / SiO2(0.05λ) / Ta(0.05λ) / Si substrate structure, and for the Cu(0.1λ) / (90°,90°,35°)LT(0.15λ) / floating electrode / SiO2(0.05λ) / Ta(0.05λ) / SiO2(0.05λ) / Ta(0.05λ) / SiO2(0.05λ) / Ta(0.05λ) / Si substrate structure. [Figure 27](a) A graph showing the displacement distribution of LLSAW in a substrate structure corresponding to the elastic wave device shown in Patent Document 3, Al(0.05λ) / (90°,90°,40°)LN(0.2λ) / SiO2(0.25λ) / Ta(0.25λ) / SiO2(0.25λ) / Ta(0.25λ) / SiO2(0.25λ) / Ta(0.25λ) / Si, (b Figure 1(a) is a graph showing the displacement distribution of the overtone SAW for an elastic wave device with a Cu(0.1λ) / (90°,90°,42.5°)LN(0.2λ) / SiO2(0.05λ) / Ta(0.05λ) / SiO2(0.05λ) / Ta(0.05λ) / SiO2(0.05λ) / Ta(0.05λ) / Si substrate structure. [Modes for carrying out the invention]

[0034] Embodiments of the present invention will be described below with reference to the drawings and examples. Figures 1 to 27 show elastic wave devices according to embodiments of the present invention. As shown in Figure 1, the elastic wave device 10 is configured to utilize the overtones among the resonance characteristics of surface acoustic waves and includes a piezoelectric substrate 11, electrodes 12, an acoustic multilayer film 13, and a support substrate 14.

[0035] As shown in Figure 1(a), the piezoelectric substrate 11 is made of a single crystal of LiNbO3 (LN) or a single crystal of LiTaO3 (LT). The electrode 12 consists of a blind-shaped electrode (IDT) 12a and is formed on one surface of the piezoelectric substrate 11 by a photolithography process or the like. The period (wavelength) λ of the electrode fingers of the blind-shaped electrode 12a is equal to the wavelength of the acoustic surface waves of the fundamental mode and overtones used. In the following, wavelength (λ) represents the period (wavelength) of the electrode fingers, i.e., the wavelength of the acoustic surface waves of the fundamental mode and overtones used.

[0036] The acoustic multilayer film 13 is attached to the surface of the piezoelectric substrate 11 opposite to the IDT. The acoustic multilayer film 13 is constructed by alternately laminating low acoustic impedance films 13a and high acoustic impedance films 13b from the piezoelectric substrate 11 side toward the opposite side. Preferably, the acoustic multilayer film 13 has an acoustic film in which low acoustic impedance films 13a and high acoustic impedance films 13b are laminated alternately in 3 to 20 layers. In the specific example shown in Figure 1(a), the layer closest to the piezoelectric substrate 11 is the low acoustic impedance film 13a, and 6 layers of low acoustic impedance films 13a and high acoustic impedance films 13b are laminated alternately.

[0037] Each low-acoustic-impedance film 13a and each high-acoustic-impedance film 13b consists of a film containing at least one of the materials shown in Table 1 or Table 2. In Table 1, Zl is the acoustic impedance of the longitudinal surface wave, c33 is the elastic stiffness constant, and in Table 2, Zs is the acoustic impedance of the transverse surface wave, c44 is the elastic stiffness constant. Also, in Tables 1 and 2, Si x N y In this equation, x and y are positive real numbers. Furthermore, whether the acoustic impedance Zl in Table 1 or Zs in Table 2 contributes depends on the displacement of the SAW. That is, it depends on Zl for SAWs with a large longitudinal wave component, and on Zs for SAWs with a large SH component.

[0038] [Table 1]

[0039] [Table 2]

[0040] Each low-acoustic-impedance film 13a is made of a material with a lower acoustic impedance than the adjacent high-acoustic-impedance film 13b. Each low-acoustic-impedance film 13a may be made of the same material or different material. Similarly, each high-acoustic-impedance film 13b may be made of the same material or different material.

[0041] The support substrate 14 is attached to the side of the acoustic multilayer film 13 opposite to the piezoelectric substrate 11, sandwiching the acoustic multilayer film 13 between the support substrate 14 and the piezoelectric substrate 11. The support substrate 14 is provided to support the piezoelectric substrate 11, the electrodes 12, and the acoustic multilayer film 13. In the specific example shown in Figure 1(a), the support substrate 14 is made of a Si substrate, but it may also be made of a glass substrate, a quartz substrate, an alumina substrate, a sapphire substrate, a germanium substrate, or the like. In Figure 1(a), an IDT is provided on the surface of the piezoelectric substrate opposite to the acoustic multilayer film, but the IDT may be provided between the piezoelectric substrate and the acoustic multilayer film.

[0042] As shown in Figure 1(b), the elastic wave device 10 may have a floating electrode (sometimes called a short-circuit electrode) 12b provided between the piezoelectric substrate 11 and the acoustic multilayer film 13. The floating electrode 12b may be made of the same material as the blind-shaped electrode 12a, or it may be made of a different material. In Figure 1(b), the IDT is provided on the surface of the piezoelectric substrate opposite to the acoustic multilayer film, and the floating electrode is provided between the piezoelectric substrate and the acoustic multilayer film, but the IDT may be provided between the piezoelectric substrate and the acoustic multilayer film, and the floating electrode may be provided on the surface of the piezoelectric substrate opposite to the acoustic multilayer film. The floating electrode 12b may be connected to one electrode of the blind-shaped electrode 12a, or to another common electrode other than the elastic wave device 10.

[0043] Next, I will explain the mechanism of action. The elastic wave device 10 can excite overtones of approximately integer multiples (approximately 2x, approximately 3x, ...) of the fundamental mode frequency of the surface acoustic wave using the acoustic multilayer film 13. Furthermore, by adjusting the thickness of the electrodes 12, the type of piezoelectric substrate 11, and the thickness of each layer of the acoustic multilayer film 13, surface acoustic wave overtones with a large impedance ratio can be obtained. By utilizing these overtones, the elastic wave device 10 can obtain good characteristics with a large impedance ratio in the ultra-high frequency band of 6 GHz or higher.

[0044] [Conventional elastic wave devices] The frequency characteristics of the SAW resonator 50 shown in Figure 2(a), which is currently in practical use and has an Al electrode (wavelength 1.2 μm, thickness 0.08 wavelengths) as an interlocking electrode (IDT) 52 on the surface of a 42°YX LT film 51, were determined. The results are shown in Figure 2(b). As shown in Figure 2(b), the frequency of the fundamental mode (0th order) was 3.2 GHz, the bandwidth was 3.6%, and the impedance ratio was 65 dB. In addition, a small response resembling an overtone of slightly more than 5 times was observed at 17.2 GHz, but it was confirmed that it was not at a usable level.

[0045] [Examples of the present invention] The frequency characteristics were determined for the elastic wave device 10 shown in Figure 1(a), with a curtain-like electrode 12a made of Cu electrode with a wavelength of 1.2 μm and a thickness of 0.1 wavelength, a piezoelectric substrate 11 made of LT (thickness of 0.2 wavelength) with Euler angles of (90°, 90°, 35°), an acoustic multilayer film 13 made of six alternating layers of low acoustic impedance film 13a (thickness of 0.25 wavelength) made of SiO2 film and high acoustic impedance film 13b (thickness of 0.25 wavelength) made of Ta film, and a Si substrate as the support substrate 14. The results are shown in Figure 3(a). As shown in Figure 3(a), the fundamental mode of SAW was confirmed at 3.8 GHz, and large spurious and harmonic responses were confirmed at 2 GHz, 5.1 GHz, 6.3 GHz, and 8.2 GHz. In addition, an overtone response of approximately three times that of the 0th mode was confirmed at 11 GHz. Note that the 5.1GHz response is LLSAW with a sound speed of 6,100m / s. Also, below, Euler angles (φ, θ, ψ) will be simply represented as (φ, θ, ψ).

[0046] Next, the elastic wave device 10 shown in Figure 1(b) was configured with a curtain-shaped electrode 12a made of Cu electrodes with a thickness of 0.1 wavelengths, a piezoelectric substrate 11 made of (90°,90°,42.5°) LN (thickness of 0.2 wavelengths), and an Al electrode floating electrode 12b (thickness of 0.01 wavelengths) sandwiched between them. The acoustic multilayer film 13 was constructed by alternately stacking a total of 6 layers of low acoustic impedance film 13a (thickness of 0.05 wavelengths) made of SiO2 film and high acoustic impedance film 13b made of Ta film, with a Si substrate 14. The frequency characteristics were then determined when the thickness of the Ta film in the high acoustic impedance film 13b was varied from 0.05 wavelengths to 0.23 wavelengths. The results are shown in Figure 3(b).

[0047] As shown in Figure 3(b), when the Ta film thickness is 0.05 wavelengths, it was confirmed that the characteristics near a center frequency of 3 GHz are the fundamental mode, the characteristics near 10 GHz are approximately 3 times the overtone ("O3" in the figure), the characteristics at 12 GHz are approximately 4 times the overtone ("O4" in the figure), and the characteristics near 15 GHz are approximately 5 times the overtone ("O5" in the figure). It was also confirmed that there is one characteristic (hereinafter referred to as the A characteristic) between the approximately 3 times overtone and the approximately 4 times overtone. When the Ta film thickness is 0.115 wavelengths, it was confirmed that the frequency of the approximately 3 times overtone becomes lower and the response becomes smaller. It was also confirmed that the frequency of the approximately 4 times overtone also becomes lower at the same time, but the response remains small. When the Ta film thickness is 0.13 wavelengths, the frequency of the approximately 4 times overtone compared to the Ta film thickness of 0.05 wavelengths becomes even lower, becoming the approximately 3 times overtone (approximately 10 GHz), but it was confirmed that it has a large impedance ratio. Thus, as shown in Figure 3(b), it was confirmed that as the thickness of the Ta film increases, the frequencies of each characteristic decrease, and the phenomenon of the impedance ratio changing between large and small is repeated. From this result, it can be seen that there is not just one condition for the thickness of the Ta film that yields a large impedance ratio, but multiple conditions. Furthermore, it was confirmed that the same phenomenon is observed even when the thickness of the SiO2 film of the low acoustic impedance film 13a is changed while keeping the thickness of the Ta film constant.

[0048] Next, the frequency characteristics of the elastic wave device 10 shown in Figures 1(a) and (b) were determined under various conditions. First, the frequency characteristics of the elastic wave device 10 shown in Figure 1(a) were determined as follows: the curtain-shaped electrode 12a was a Cu electrode with a wavelength of 1.2 μm and a thickness of 0.1 wavelengths; the piezoelectric substrate 11 was (0°,85°,0°)LN (thickness of 0.2 wavelengths); the acoustic multilayer film 13 was made of six layers of alternating low acoustic impedance film 13a (thickness of 0.06 wavelengths) made of Al film and high acoustic impedance film 13b (thickness of 0.06 wavelengths) made of W film; and the support substrate 14 was a Si substrate. These characteristics are shown in Figure 4(a). Furthermore, Figure 4(b) shows the frequency characteristics of the elastic wave device 10 shown in Figure 1(b), where the curtain-shaped electrode 12a is a Cu electrode 12 with a wavelength of 1.2 μm and a thickness of 0.1 wavelengths, the piezoelectric substrate 11 is (90°,90°,42.5°)LN (thickness of 0.2 wavelengths), the floating electrode 12b is an Al electrode, the acoustic multilayer film 13 is made up of six layers of alternating low acoustic impedance films 13a (thickness of 0.05 wavelengths) made of SiO2 films and high acoustic impedance films 13b (thickness of 0.05 wavelengths) made of Ta films, and the support substrate 14 is a Si substrate.

[0049] Furthermore, Figure 4(c) shows the frequency characteristics when the elastic wave device 10 shown in Figure 1(a) is configured such that the curtain-shaped electrode 12a is a Cu electrode with a wavelength of 1.2 μm and a thickness of 0.1 wavelengths, the piezoelectric substrate 11 is (0°,85°,0°)LT (thickness of 0.15 wavelengths), the acoustic multilayer film 13 is made up of six layers of alternating low acoustic impedance films 13a (thickness of 0.05 wavelengths) made of Al films and high acoustic impedance films 13b (thickness of 0.05 wavelengths) made of W films, and the support substrate 14 is a Si substrate. Furthermore, Figure 4(d) shows the frequency characteristics when the elastic wave device 10 shown in Figure 1(b) has a curtain-shaped electrode 12a made of Cu electrode with a wavelength of 1.2 μm and a thickness of 0.1 wavelength, a piezoelectric substrate 11 made of (90°,90°,35°)LT (thickness of 0.15 wavelengths), a floating electrode 12b made of Al electrode, and an acoustic multilayer film 13 made of SiO2 film with a low acoustic impedance film 13a (thickness of 0.07 wavelengths) and a high acoustic impedance film 13b (thickness of 0.07 wavelengths) made of Ta film stacked alternately in a total of 6 layers, and the support substrate 14 is a Si substrate. Note that if the floating electrode 12b shown in Figure 1(a) is not present, it is preferable that the surface of the Al film in contact with the piezoelectric substrate 11 is an insulating anodized film.

[0050] As shown in Figures 4(a) to 4(d), it was confirmed that the fundamental mode and spurious emission magnitudes of the SAW in the 1-5 GHz range were significantly smaller in all frequency characteristics compared to the fundamental mode in Figure 3. On the other hand, the overtone response in the 9-11 GHz range was large, and it was confirmed that a bandwidth of 3.2-8.1% and an impedance ratio of 71-76 dB were obtained. The frequency of this overtone corresponds to a sound velocity of 12,000-13,000 m / s, which is 3.1 times the frequency of the fundamental mode shown in Figure 2. The following shows the results obtained by changing various conditions in order to obtain overtones with good characteristics.

[0051] [When using an LN substrate] The elastic wave device 10 shown in Figure 1(a) has a structure in which the curtain-shaped electrode 12a is a Cu electrode with a wavelength of 1.2 μm and a thickness of 0.1 wavelength, the piezoelectric substrate 11 is (0°,θ,0°)LN (thickness of 0.2 wavelengths), the acoustic multilayer film 13 is made of six layers of alternating low acoustic impedance film 13a (thickness of 0.05 wavelengths) made of Al film and high acoustic impedance film 13b (thickness of 0.05 wavelengths) made of W film, and the support substrate 14 is a Si substrate (hereinafter referred to as Cu(0.1λ) / (0°,θ,0°)LN(0.2λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Si substrate), and the bandwidth and impedance ratio are as follows (hereinafter referred to as Cu(0.1λ) / (0°,θ,0°)LN(0.2λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Si substrate). The dependence of the ratio on the Euler angle θ is shown in Figures 5(a) and (b), respectively. It is desirable that the surface of the first layer Al film of the acoustic multilayer film 13 on the piezoelectric substrate side is anodized for insulation, or that an insulating low acoustic impedance film such as an SiO2 film is used. Unless otherwise specified, in the absence of a floating electrode 12b in contact with the first layer Al film of the acoustic multilayer film 13, the surface of the first layer Al film in the following examples is assumed to be anodized. As shown in Figures 5(a) and (b), it was confirmed that a bandwidth of 3% or more and an impedance ratio of 60 dB or more can be obtained for θ = 60° to 103°. Furthermore, it was confirmed that the impedance ratio is 65 dB or more for θ = 72° to 97° and 70 dB or more for θ = 78° to 92°.

[0052] Figure 6 shows the dependence of the impedance ratio of the elastic wave device 10 shown in Figure 1(a) on the Euler angle φ when the substrate is Cu(0.1λ) / (φ,85°,0°)LN(0.2λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Si. As shown in Figure 6, it was confirmed that an impedance ratio of 70 dB or more can be obtained when φ = -30° to 30°.

[0053] Figure 7 shows the dependence of the impedance ratio on the Euler angle ψ for the elastic wave device 10 shown in Figure 1(a) when the substrate is Cu(0.1λ) / (0°,85°,ψ)LN(0.2λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Si. As shown in Figure 7, it was confirmed that an impedance ratio of 65 dB or more can be obtained for ψ = -15° to 15°, and 70 dB or more for ψ = -6° to 6°.

[0054] From the results in Figures 5-7, it can be seen that in the elastic wave device 10 shown in Figure 1(a), by using (-30°~30°, 60°~103°, -15°~15°)LN as the piezoelectric substrate 11, a bandwidth of 3% or more and an impedance ratio of 60 dB or more can be obtained. Furthermore, it can be seen that by using (-30°~30°, 72°~97°, -15°~15°)LN, an impedance ratio of 65 dB or more can be obtained, and by using (-30°~30°, 78°~92°, -6°~6°)LN, an impedance ratio of 70 dB or more can be obtained.

[0055] Figure 1(a) shows the elastic wave device 10, which is composed of Cu(0.1λ) / (0°,85°,0°)LN(0.2λ) / Al film / W film / Al film / W film / Al film / W film / Si substrate. Figure 8(a) shows the dependence of the impedance ratio on the W film thickness when the W film thickness of the high acoustic impedance film 13b is varied, with the Al film thickness set to 0.05 wavelengths. Figure 8(b) also shows the dependence of the impedance ratio on the Al film thickness when the Al film thickness of the low acoustic impedance film 13a is varied, with the W film thickness set to 0.05 wavelengths.

[0056] As shown in Figure 8(a), it was confirmed that an impedance ratio of 60 dB or more was obtained when the W thickness of the high acoustic impedance film 13b was 0.026 to 0.108 wavelengths and 0.12 to 0.187 wavelengths, an impedance ratio of 65 dB or more was obtained when it was 0.028 to 0.107 wavelengths and 0.125 to 0.185 wavelengths, and an impedance ratio of 70 dB or more was obtained when it was 0.035 to 0.102 wavelengths. In addition, although not shown in the figures, it was confirmed that a large impedance ratio was also obtained when the W thickness of the high acoustic impedance film 13b was 0.2 wavelengths or more, an impedance ratio of 60 dB or more was obtained when the W thickness was 0.216 to 0.275 wavelengths, an impedance ratio of 65 dB or more was obtained when the W thickness was 0.22 to 0.27 wavelengths, and an impedance ratio of 70 dB or more was obtained when the W thickness was 0.23 to 0.26 wavelengths. Figure 8(a) shows an example when the Al film thickness is 0.05 wavelengths. However, even when the Al film thickness is between 0.02 and 0.118 wavelengths, the optimal W film thickness is the same as when the Al film thickness is 0.05 wavelengths.

[0057] As shown in Figure 8(b), it was confirmed that an impedance ratio of 60 dB or more was obtained when the Al film thickness of the low acoustic impedance film 13a was 0.02 to 0.118 wavelengths and 0.129 to 0.185 wavelengths, an impedance ratio of 65 dB or more was obtained when the Al film thickness was 0.025 to 0.117 wavelengths and 0.135 to 0.18 wavelengths, and an impedance ratio of 70 dB or more was obtained when the Al film thickness was 0.04 to 0.113 wavelengths. In addition, although not shown in the figures, it was confirmed that a large impedance ratio was also obtained when the Al film thickness of the low acoustic impedance film 13a was 0.2 wavelengths or more, an impedance ratio of 60 dB or more was obtained when the Al film thickness was 0.216 to 0.275 wavelengths, an impedance ratio of 65 dB or more was obtained when the Al film thickness was 0.22 to 0.27 wavelengths, and an impedance ratio of 70 dB or more was obtained when the Al film thickness was 0.225 to 0.254 wavelengths. Figure 8(b) shows an example when the W film thickness is 0.05 wavelengths, but even when the W film thickness is between 0.02 and 0.118 wavelengths, the optimal Al film thickness is the same as when the W film thickness is 0.05 wavelengths.

[0058] Figures 9(a) and 9(b) show the dependence of the bandwidth and impedance ratio on the Euler angle θ for the elastic wave device 10 shown in Figure 1(b), when the substrate is Cu(0.1λ) / (0°,θ,0°)LN(0.2λ) / floating electrode / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Si, respectively. The first layer of the acoustic multilayer film 13, the Al film, has an insulating anodized surface. When an unanodized Al electrode is used as the first layer, the first layer of the Al film may also be used as the floating electrode. As shown in Figures 9(a) and (b), it was confirmed that a bandwidth of 4% or more and an impedance ratio of 60 dB or more were obtained for θ = 64° to 98°, an impedance ratio of 65 dB or more was obtained for θ = 68° to 95°, and an impedance ratio of 70 dB or more was obtained for θ = 72° to 92°.

[0059] Figure 10(a) shows the dependence of the impedance ratio on the thickness of the W film when the thickness of the W film of the high acoustic impedance film 13b is changed, with the Al film thickness set to 0.05 wavelengths. Figure 10(b) also shows the dependence of the impedance ratio on the thickness of the Al film when the thickness of the Al film of the low acoustic impedance film 13a is changed, with the W film thickness set to 0.05 wavelengths.

[0060] As shown in Figure 10(a), it was confirmed that an impedance ratio of 60 dB or more was obtained when the W thickness of the high acoustic impedance film 13b was 0.02 to 0.105 wavelengths and 0.121 to 0.183 wavelengths, an impedance ratio of 65 dB or more was obtained when it was 0.027 to 0.103 wavelengths and 0.124 to 0.18 wavelengths, and an impedance ratio of 70 dB or more was obtained when it was 0.036 to 0.095 wavelengths. In addition, although not shown in the figure, it was confirmed that a large impedance ratio was also obtained when the W thickness of the high acoustic impedance film 13b was 0.2 wavelengths or more, an impedance ratio of 60 dB or more was obtained when the W thickness was 0.216 to 0.275 wavelengths, an impedance ratio of 65 dB or more was obtained when the W thickness was 0.22 to 0.27 wavelengths, and an impedance ratio of 70 dB or more was obtained when the W thickness was 0.23 to 0.26 wavelengths. Figure 10(a) shows an example when the Al film thickness is 0.05 wavelengths, but even when the Al film thickness is between 0.02 and 0.113 wavelengths, the optimal W film thickness is the same as when the Al film thickness is 0.05 wavelengths.

[0061] As shown in Figure 10(b), it was confirmed that an impedance ratio of 60 dB or more was obtained when the Al film thickness of the low acoustic impedance film 13a was 0.02 to 0.113 wavelengths and 0.132 to 0.185 wavelengths, an impedance ratio of 65 dB or more was obtained when the Al film thickness was 0.024 to 0.112 wavelengths and 0.135 to 0.18 wavelengths, and an impedance ratio of 70 dB or more was obtained when the Al film thickness was 0.038 to 0.104 wavelengths. In addition, although not shown in the figures, it was confirmed that a large impedance ratio was also obtained when the Al film thickness of the low acoustic impedance film 13a was 0.2 wavelengths or more, an impedance ratio of 60 dB or more was obtained when the Al film thickness was 0.216 to 0.275 wavelengths, an impedance ratio of 65 dB or more was obtained when the Al film thickness was 0.22 to 0.27 wavelengths, and an impedance ratio of 70 dB or more was obtained when the Al film thickness was 0.225 to 0.254 wavelengths. Figure 10(b) shows an example when the W film thickness is 0.05 wavelengths, but even when the W film thickness is between 0.02 and 0.105 wavelengths, the optimal Al film thickness is the same as when the W film thickness is 0.05 wavelengths.

[0062] Figures 11(a) and (b) show the dependence of the bandwidth and impedance ratio on the Euler angle ψ for the elastic wave device 10 shown in Figure 1(a) when the substrate is Cu(0.1λ) / (90°,90°,ψ)LN(0.2λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Si, respectively. As shown in Figures 11(a) and (b), it was confirmed that a bandwidth of 7% or more and an impedance ratio of 60 dB or more were obtained for ψ = 160°~180° and 0°~48°, i.e., -20°~48°; an impedance ratio of 65 dB or more was obtained for ψ = 170°~180° and 0°~43°, i.e., -10°~43°; and an impedance ratio of 70 dB or more was obtained for ψ = 178°~180° and 0°~33°, i.e., -2°~33°. Furthermore, although Euler angles φ and θ are not shown in the diagram, it was confirmed that almost the same values ​​were obtained for ±6°, an impedance ratio of 60 dB or more was obtained for (90°±6°, 90°±6°, -20°~48°), an impedance ratio of 65 dB or more was obtained for (90°±6°, 90°±6°, -10°~43°), and an impedance ratio of 70 dB or more was obtained for (90°±6°, 90°±6°, -2°~33°).

[0063] Figure 12(a) shows the dependence of the impedance ratio on the thickness of the W film in the high acoustic impedance film 13b when the thickness of the W film is varied, with the Al film thickness set to 0.05 wavelengths. Figure 12(b) also shows the dependence of the impedance ratio on the thickness of the Al film in the low acoustic impedance film 13a when the thickness of the Al film is varied, with the W film thickness set to 0.05 wavelengths.

[0064] As shown in Figure 12(a), it was confirmed that an impedance ratio of 60 dB or more was obtained when the W thickness of the high acoustic impedance film 13b was 0.015 to 0.104 wavelengths and 0.12 to 0.183 wavelengths, an impedance ratio of 65 dB or more was obtained when it was 0.018 to 0.101 wavelengths and 0.123 to 0.181 wavelengths, and an impedance ratio of 70 dB or more was obtained when it was 0.024 to 0.097 wavelengths. In addition, although not shown in the figures, it was confirmed that a large impedance ratio was also obtained when the W thickness of the high acoustic impedance film 13b was 0.2 wavelengths or more, an impedance ratio of 60 dB or more was obtained when the W thickness was 0.216 to 0.275 wavelengths, an impedance ratio of 65 dB or more was obtained when the W thickness was 0.22 to 0.27 wavelengths, and an impedance ratio of 70 dB or more was obtained when the W thickness was 0.23 to 0.26 wavelengths. Figure 12(a) shows an example when the Al film thickness is 0.05 wavelengths, but even when the Al film thickness is between 0.014 and 0.113 wavelengths, the optimal W film thickness is the same as when the Al film thickness is 0.05 wavelengths.

[0065] As shown in Figure 12(b), it was confirmed that an impedance ratio of 60 dB or more was obtained when the Al film thickness of the low acoustic impedance film 13a was 0.014 to 0.113 wavelengths and 0.124 to 0.182 wavelengths, an impedance ratio of 65 dB or more was obtained when the Al film thickness was 0.016 to 0.109 wavelengths and 0.13 to 0.176 wavelengths, and an impedance ratio of 70 dB or more was obtained when the Al film thickness was 0.022 to 0.104 wavelengths. In addition, although not shown in the figures, it was confirmed that a large impedance ratio was also obtained when the Al film thickness of the low acoustic impedance film 13a was 0.2 wavelengths or more, an impedance ratio of 60 dB or more was obtained when the Al film thickness was 0.216 to 0.275 wavelengths, an impedance ratio of 65 dB or more was obtained when the Al film thickness was 0.22 to 0.27 wavelengths, and an impedance ratio of 70 dB or more was obtained when the Al film thickness was 0.225 to 0.254 wavelengths. Figure 12(b) shows an example when the W film thickness is 0.05 wavelengths, but even when the W film thickness is between 0.015 and 0.104 wavelengths, the optimal Al film thickness is the same as when the W film thickness is 0.05 wavelengths.

[0066] Figures 13(a) and (b) show the dependence of the bandwidth and impedance ratio on the Euler angle ψ for the elastic wave device 10 shown in Figure 1(b), when the substrate is Cu(0.1λ) / (90°,90°,ψ)LN(0.2λ) / floating electrode / SiO2(0.05λ) / Ta(0.05λ) / SiO2(0.05λ) / Ta(0.05λ) / Si, respectively. As shown in Figures 13(a) and (b), it was confirmed that a bandwidth of 7% or more and an impedance ratio of 65 dB or more were obtained for ψ = 176°~180° and 0°~56°, i.e., -4°~56°, an impedance ratio of 70 dB or more was obtained for ψ = 178°~180° and 0°~52°, i.e., -2°~52°, and an impedance ratio of 75 dB or more was obtained for ψ = 25°~50°.

[0067] Furthermore, although Euler angles φ and θ are not shown in the diagram, it was confirmed that almost the same values ​​were obtained for ±6°, an impedance ratio of 65 dB or more was obtained for (90°±6°, 90°±6°, -4°~56°), an impedance ratio of 70 dB or more was obtained for (90°±6°, 90°±6°, -2°~52°), and an impedance ratio of 75 dB or more was obtained for (90°±6°, 90°±6°, 25°~50°).

[0068] Figure 14(a) shows the dependence of the impedance ratio on the Ta film thickness when the Ta film thickness of the high acoustic impedance film 13b is changed, with the SiO2 film thickness set to 0.05 wavelengths. Figure 14(b) also shows the dependence of the impedance ratio on the SiO2 film thickness when the SiO2 film thickness of the low acoustic impedance film 13a is changed, with the Ta film thickness set to 0.05 wavelengths.

[0069] As shown in Figure 14(a), it was confirmed that an impedance ratio of 60 dB or more was obtained when the Ta film thickness of the high acoustic impedance film 13b was 0.015 to 0.1 wavelengths, 0.118 to 0.175 wavelengths, and 0.216 to 0.275 wavelengths; an impedance ratio of 65 dB or more was obtained when it was 0.017 to 0.093 wavelengths, 0.12 to 0.17 wavelengths, and 0.22 to 0.27 wavelengths; an impedance ratio of 70 dB or more was obtained when it was 0.02 to 0.087 wavelengths, 0.125 to 0.165 wavelengths, and 0.23 to 0.26 wavelengths; and an impedance ratio of 75 dB or more was obtained when it was 0.036 to 0.082 wavelengths. Figure 14(a) shows an example where the SiO2 film thickness is 0.05 wavelengths. However, even when the SiO2 film thickness was between 0.012 and 0.096 wavelengths, the optimal Ta film thickness was the same as when the SiO2 film thickness was 0.05 wavelengths.

[0070] Furthermore, as shown in Figure 14(b), it was confirmed that an impedance ratio of 60 dB or higher was obtained when the SiO2 film thickness of the low acoustic impedance film 13a was 0.012-0.096 wavelengths, 0.12-0.185 wavelengths, and 0.216-0.275 wavelengths; an impedance ratio of 65 dB or higher was obtained when it was 0.015-0.092 wavelengths, 0.125-0.18 wavelengths, and 0.22-0.27 wavelengths; an impedance ratio of 70 dB or higher was obtained when it was 0.02-0.087 wavelengths, 0.133-0.172 wavelengths, and 0.225-0.254 wavelengths; and an impedance ratio of 75 dB or higher was obtained when it was 0.04-0.07 wavelengths. Figure 14(b) shows an example when the Ta film thickness is 0.05 wavelengths. However, even when the Ta film thickness is between 0.015 and 0.1 wavelengths, the optimal SiO2 film thickness is the same as when the Ta film thickness is 0.05 wavelengths.

[0071] [When using an LT substrate] Figures 15(a) and (b) show the dependence of the bandwidth and impedance ratio on the Euler angle θ for the elastic wave device 10 shown in Figure 1(a) when using a Cu(0.1λ) / (0°,θ,0°)LT(0.15λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Si substrate, respectively. As shown in Figures 15(a) and (b), it was confirmed that a bandwidth of 2% or more and an impedance ratio of 60 dB or more can be obtained for θ = 55° to 100°, an impedance ratio of 65 dB or more can be obtained for θ = 61° to 95°, and an impedance ratio of 70 dB or more can be obtained for θ = 70° to 89°.

[0072] Furthermore, since the crystal structure of LT is the same as that of LN, the relationships between φ and ψ in (φ,θ,ψ)LT were also the same as in LN. For this reason, in the case of LT as well, impedance ratios of 60 dB or more can be obtained for (-30°~30°, 55°~100°, -15°~15°)LT, impedance ratios of 65 dB or more can be obtained for (-30°~30°, 61°~95°, -15°~15°)LT, and impedance ratios of 70 dB or more can be obtained for (-30°~30°, 70°~89°, -6°~6°)LT.

[0073] Figure 16(a) shows the dependence of the impedance ratio on the thickness of the W film when the thickness of the W film of the high acoustic impedance film 13b is changed, with the Al film thickness set to 0.05 wavelengths. Figure 16(b) also shows the dependence of the impedance ratio on the thickness of the Al film when the thickness of the Al film of the low acoustic impedance film 13a is changed, with the W film thickness set to 0.05 wavelengths.

[0074] As shown in Figure 16(a), it was confirmed that an impedance ratio of 60 dB or more was obtained when the W thickness of the high acoustic impedance film 13b was 0.02 to 0.10 wavelengths and 0.115 to 0.2 wavelengths, an impedance ratio of 65 dB or more was obtained when it was 0.025 to 0.095 wavelengths and 0.117 to 0.19 wavelengths, and an impedance ratio of 70 dB or more was obtained when it was 0.03 to 0.092 wavelengths and 0.12 to 0.17 wavelengths. In addition, although not shown in the figure, it was confirmed that a large impedance ratio was also obtained when the W thickness of the high acoustic impedance film 13b was 0.2 wavelengths or more, an impedance ratio of 60 dB or more was obtained when the W thickness was 0.216 to 0.275 wavelengths, an impedance ratio of 65 dB or more was obtained when the W thickness was 0.22 to 0.27 wavelengths, and an impedance ratio of 70 dB or more was obtained when the W thickness was 0.225 to 0.26 wavelengths. Figure 16(a) shows an example when the Al film thickness is 0.05 wavelengths, but even when the Al film thickness is between 0.02 and 0.1 wavelengths, the optimal W film thickness is the same as when the Al film thickness is 0.05 wavelengths.

[0075] As shown in Figure 16(b), it was confirmed that when the Al film thickness of the low acoustic impedance film 13a was 0.02-0.1 wavelengths and 0.115-0.2 wavelengths, an impedance ratio of 60 dB or more was obtained; when it was 0.025-0.095 wavelengths and 0.12-0.19 wavelengths, an impedance ratio of 65 dB or more was obtained; and when it was 0.03-0.12 wavelengths and 0.12-0.15 wavelengths, an impedance ratio of 70 dB or more was obtained. In addition, although not shown in the figure, it was confirmed that a large impedance ratio could also be obtained with an Al film thickness of 0.2 wavelengths or more for the high acoustic impedance film 13b, an impedance ratio of 60 dB or more was obtained when the Al film thickness was 0.216-0.275 wavelengths, an impedance ratio of 65 dB or more was obtained when the Al film thickness was 0.22-0.27 wavelengths, and an impedance ratio of 70 dB or more was obtained when the Al film thickness was 0.225-0.26 wavelengths. Figure 16(b) shows an example when the W film thickness is 0.05 wavelengths, but even when the W film thickness is between 0.02 and 0.1 wavelengths, the optimal Al film thickness is the same as when the W film thickness is 0.05 wavelengths.

[0076] Figures 17(a) and (b) show the dependence of the bandwidth and impedance ratio with respect to the Euler angle θ for the elastic wave device 10 shown in Figure 1(b), when it is constructed as a Cu(0.1λ) / (0°,θ,0°)LT(0.15λ) / floating electrode / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Si substrate, and when it is constructed as a Cu(0.1λ) / (0°,θ,0°)LT(0.15λ) / floating electrode / SiO2(0.05λ) / Ta(0.05λ) / SiO2(0.05λ) / Ta(0.05λ) / SiO2(0.05λ) / Ta(0.05λ) / Si substrate, respectively. As shown in Figures 17(a) and (b), it was confirmed that there was almost no difference in the θ dependence of the bandwidth and impedance ratio between the combination of the low acoustic impedance film 13a and the high acoustic impedance film 13b, whether it was the Al film and W film or the SiO2 film and Ta film. Furthermore, it was confirmed that in all combinations, a bandwidth of 2% or more and an impedance ratio of 60 dB or more were obtained at θ = 65° to 94°, and an impedance ratio of 65 dB or more was obtained at θ = 69° to 91°.

[0077] Figure 18(a) shows the dependence of the impedance ratio on the thickness of the W film in the high acoustic impedance film 13b when the thickness of the W film is changed, with the Al film thickness set to 0.05 wavelengths. Figure 18(b) also shows the dependence of the impedance ratio on the thickness of the Al film in the low acoustic impedance film 13a when the thickness of the Al film is changed, with the W film thickness set to 0.05 wavelengths.

[0078] As shown in Figure 18(a), it was confirmed that an impedance ratio of 60 dB or more was obtained when the W film thickness of the high acoustic impedance film 13b was 0.023 to 0.097 wavelengths and 0.116 to 0.194 wavelengths, and an impedance ratio of 65 dB or more was obtained when it was 0.028 to 0.093 wavelengths and 0.118 to 0.18 wavelengths. In addition, although not shown in the figure, a large impedance ratio was also obtained when the W film thickness of the high acoustic impedance film 13b was 0.2 wavelengths or more, and it was confirmed that an impedance ratio of 60 dB or more was obtained when the W film thickness was 0.216 to 0.275 wavelengths, and an impedance ratio of 65 dB or more was obtained when the W film thickness was 0.22 to 0.27 wavelengths. Figure 18(a) shows an example when the Al film thickness is 0.05 wavelengths, but even when the Al film thickness was 0.023 to 0.098 wavelengths, the optimal W film thickness was the same as when the Al film thickness was 0.05 wavelengths.

[0079] As shown in Figure 18(b), it was confirmed that when the Al film thickness of the low acoustic impedance film 13a was 0.023-0.098 wavelengths and 0.125-0.193 wavelengths, an impedance ratio of 60 dB or more was obtained, and when it was 0.028-0.094 wavelengths and 0.135-0.185 wavelengths, an impedance ratio of 65 dB or more was obtained. In addition, although not shown in the figure, it was confirmed that a large impedance ratio was also obtained when the Al film thickness of the high acoustic impedance film 13b was 0.2 wavelengths or more, with an impedance ratio of 60 dB or more obtained when the Al film thickness was 0.216-0.275 wavelengths, and an impedance ratio of 65 dB or more obtained when the Al film thickness was 0.22-0.27 wavelengths. Figure 18(b) shows an example when the W film thickness is 0.05 wavelengths, but even when the W film thickness was 0.023-0.097 wavelengths, the optimal Al film thickness was the same as when the W film thickness was 0.05 wavelengths.

[0080] Figures 19(a) and (b) show the dependence of the bandwidth and impedance ratio on the Euler angle θ for the elastic wave device 10 shown in Figure 1(a) when the substrate is Cu(0.1λ) / (90°,90°,ψ)LT(0.15λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Al(0.05λ) / W(0.05λ) / Si, respectively. As shown in Figures 19(a) and (b), it was confirmed that a bandwidth of 2.3% or more and an impedance ratio of 65 dB or more were obtained for ψ = 175°~180°, 0°~61°, and 83°~93°, i.e., for ψ = -5°~61° and 83°~93°, an impedance ratio of 70 dB or more was obtained for ψ = 15°~55° and 85°~91°, and an impedance ratio of 75 dB or more was obtained for ψ = 23°~38°.

[0081] Furthermore, although Euler angles φ and θ are not shown in the diagram, it was confirmed that almost the same values ​​were obtained for ±6°, impedance ratios of 65 dB or more were obtained for (90°±6°, 90°±6°, -5°~61°) and (90°±6°, 90°±6°, 83°~93°), impedance ratios of 70 dB or more were obtained for (90°±6°, 90°±6°, 15°~55°) and (90°±6°, 90°±6°, 85°~91°), and impedance ratios of 75 dB or more were obtained for (90°±6°, 90°±6°, 23°~83°).

[0082] Figure 1(a) shows the elastic wave device 10, which is composed of Cu(0.1λ) / (90°,90°,35°)LT(0.15λ) / Al film / W film / Al film / W film / Al film / W film / Si substrate. Figure 20(a) shows the dependence of the impedance ratio on the W film thickness when the W film thickness of the high acoustic impedance film 13b is varied, with the Al film thickness set to 0.05 wavelengths. Figure 20(b) also shows the dependence of the impedance ratio on the Al film thickness when the Al film thickness of the low acoustic impedance film 13a is varied, with the W film thickness set to 0.05 wavelengths.

[0083] As shown in Figure 20(a), it was confirmed that an impedance ratio of 65 dB or more was obtained when the W thickness of the high acoustic impedance film 13b was 0.016 to 0.08 wavelengths and 0.105 to 0.172 wavelengths, an impedance ratio of 70 dB or more was obtained when it was 0.02 to 0.074 wavelengths and 0.114 to 0.16 wavelengths, and an impedance ratio of 75 dB or more was obtained when it was 0.03 to 0.067 wavelengths. In addition, although not shown in the figures, it was confirmed that a large impedance ratio was also obtained when the W thickness of the high acoustic impedance film 13b was 0.2 wavelengths or more, an impedance ratio of 60 dB or more was obtained when the W thickness was 0.216 to 0.275 wavelengths, an impedance ratio of 65 dB or more was obtained when the W thickness was 0.22 to 0.27 wavelengths, and an impedance ratio of 70 dB or more was obtained when the W thickness was 0.225 to 0.26 wavelengths. Figure 20(a) shows an example when the Al film thickness is 0.05 wavelengths, but even when the Al film thickness is between 0.018 and 0.08 wavelengths, the optimal W film thickness is the same as when the Al film thickness is 0.05 wavelengths.

[0084] As shown in Figure 20(b), it was confirmed that when the Al film thickness of the low acoustic impedance film 13a was 0.018-0.08 wavelengths and 0.106-0.17 wavelengths, an impedance ratio of 65 dB or more was obtained; when the Al film thickness was 0.022-0.076 wavelengths and 0.117-0.16 wavelengths, an impedance ratio of 70 dB or more was obtained; and when the Al film thickness was 0.032-0.07 wavelengths, an impedance ratio of 75 dB or more was obtained. In addition, although not shown in the figure, it was confirmed that a large impedance ratio could also be obtained with an Al film thickness of 0.2 wavelengths or more for the high acoustic impedance film 13b, an impedance ratio of 60 dB or more was obtained when the Al film thickness was 0.216-0.275 wavelengths, an impedance ratio of 65 dB or more was obtained when the Al film thickness was 0.22-0.27 wavelengths, and an impedance ratio of 70 dB or more was obtained when the Al film thickness was 0.225-0.26 wavelengths. Figure 20(b) shows an example when the W film thickness is 0.05 wavelengths, but even when the W film thickness is between 0.016 and 0.08 wavelengths, the optimal Al film thickness is the same as when the W film thickness is 0.05 wavelengths.

[0085] Figures 21(a) and (b) show the dependence of the bandwidth and impedance ratio on the Euler angle ψ for the elastic wave device 10 shown in Figure 1(b), when the substrate is Cu(0.1λ) / (90°,90°,ψ)LT(0.15λ) / floating electrode / SiO2(0.05λ) / Ta(0.05λ) / SiO2(0.05λ) / Ta(0.05λ) / Si, respectively. As shown in Figures 21(a) and (b), it was confirmed that a bandwidth of 7% or more and an impedance ratio of 65 dB or more were obtained for ψ = 176°~180° and 0°~56°, i.e., -4°~56°, an impedance ratio of 70 dB or more was obtained for ψ = 178°~180° and 0°~52°, i.e., -2°~52°, and an impedance ratio of 75 dB or more was obtained for ψ = 25°~50°.

[0086] Furthermore, although Euler angles φ and θ are not shown in the diagram, it was confirmed that almost the same values ​​were obtained for ±6°, an impedance ratio of 65 dB or more was obtained for (90°±6°, 90°±6°, -4°~56°), an impedance ratio of 70 dB or more was obtained for (90°±6°, 90°±6°, -2°~52°), and an impedance ratio of 75 dB or more was obtained for (90°±6°, 90°±6°, 25°~50°).

[0087] Figure 1(b) shows the elastic wave device 10, which consists of Cu(0.1λ) / (90°,90°,35°)LT(0.15λ) / floating electrode / SiO2 film / Ta film / SiO2 film / Ta film / SiO2 film / Ta film / Si substrate. Figure 22(a) shows the dependence of the impedance ratio on the Ta film thickness when the Ta film thickness of the high acoustic impedance film 13b is changed, with the SiO2 film thickness set to 0.05 wavelengths. Figure 22(b) also shows the dependence of the impedance ratio on the SiO2 film thickness when the SiO2 film thickness of the low acoustic impedance film 13a is changed, with the Ta film thickness set to 0.05 wavelengths.

[0088] As shown in Figure 22(a), it was confirmed that an impedance ratio of 60 dB or more was obtained when the Ta film thickness of the high acoustic impedance film 13b was 0.015-0.085 wavelengths, 0.105-0.183 wavelengths, and 0.216-0.275 wavelengths; an impedance ratio of 65 dB or more was obtained when it was 0.018-0.08 wavelengths, 0.107-0.175 wavelengths, and 0.22-0.27 wavelengths; an impedance ratio of 70 dB or more was obtained when it was 0.02-0.075 wavelengths, 0.115-0.165 wavelengths, and 0.225-0.26 wavelengths; and an impedance ratio of 75 dB or more was obtained when it was 0.034-0.065 wavelengths. Figure 22(a) shows an example when the SiO2 film thickness is 0.05 wavelengths. However, even when the SiO2 film thickness is between 0.015 and 0.085 wavelengths, the optimal Ta film thickness is the same as when the SiO2 film thickness is 0.05 wavelengths.

[0089] Furthermore, as shown in Figure 22(b), it was confirmed that an impedance ratio of 60 dB or higher was obtained when the SiO2 film thickness of the low acoustic impedance film 13a was 0.015-0.085 wavelengths, 0.118-0.18 wavelengths, and 0.216-0.275 wavelengths; an impedance ratio of 65 dB or higher was obtained when it was 0.017-0.093 wavelengths, 0.122-0.175 wavelengths, and 0.22-0.27 wavelengths; an impedance ratio of 70 dB or higher was obtained when it was 0.02-0.087 wavelengths, 0.13-0.17 wavelengths, and 0.225-0.26 wavelengths; and an impedance ratio of 75 dB or higher was obtained when it was 0.035-0.08 wavelengths. Figure 20(b) shows an example when the Ta film thickness is 0.05 wavelengths. However, even when the Ta film thickness is between 0.015 and 0.085 wavelengths, the optimal SiO2 film thickness is the same as when the Ta film thickness is 0.05 wavelengths.

[0090] Figure 23 shows the dependence of the impedance ratio on the thickness of the piezoelectric substrate 11 when the elastic wave device 10 shown in Figure 1(b) is Cu(0.1λ) / (90°,90°,42.5°)LN(0.2λ) / floating electrode / SiO2 film(0.05λ) / Ta film(0.05λ) / SiO2 film(0.05λ) / Ta film(0.05λ) / SiO2 film(0.05λ) / Ta film(0.05λ) / Si substrate, and when it is Cu(0.1λ) / (90°,90°,35°)LT(0.15λ) / floating electrode / SiO2 film(0.05λ) / Ta film(0.05λ) / SiO2 film(0.05λ) / Ta film(0.05λ) / SiO2 film(0.05λ) / Ta film(0.05λ) / Si substrate. As shown in Figure 23, it was confirmed that an impedance ratio of 65 dB or higher was obtained when the thicknesses of LN and LT were 5 wavelengths or less and 2.4 wavelengths or less, respectively; an impedance ratio of 70 dB or higher was obtained when the thicknesses of LN and LT were 1.2 wavelengths or less and 1 wavelength or less, respectively; and an impedance ratio of 75 dB or higher was obtained when the thicknesses of LN and LT were 0.3 to 0.02 wavelengths and 0.25 to 0.02 wavelengths, respectively.

[0091] Figure 24 shows the dependence of the impedance ratio on the number of layers of the acoustic multilayer film 13 when the elastic wave device 10 shown in Figure 1(b) is composed of Cu(0.1λ) / (90°,90°,35°)LT(0.15λ) / floating electrode / SiO2 film (0.05λ) / Ta film (0.05λ) / SiO2 film (0.05λ) / Ta film (0.05λ) / SiO2 film (0.05λ) / Ta film (0.05λ) / Si substrate. As shown in Figure 24, it was confirmed that an impedance ratio of 65 dB was obtained when there were 3 layers of acoustic multilayer film 13, an impedance ratio of 72 dB was obtained when there were 4 layers, an impedance ratio of 74 dB was obtained when there were 5 layers, and an impedance ratio of 76 dB was obtained when there were 6 to 30 layers. Furthermore, the film of Ti or other material added to enhance the adhesive strength when forming each film of the acoustic multilayer film 13 has a thickness of several tens to several hundred nanometers, which is relatively very thin compared to each film of the acoustic multilayer film 13, and therefore is not included as an acoustic impedance film.

[0092] Figure 25 shows the dependence of the impedance ratio of the curtain-shaped electrode 12a on the electrode 12 thickness when the elastic wave device 10 shown in Figure 1(b) has a curtain-shaped electrode 12a / (90°,90°,35°)LT(0.15λ) / floating electrode / SiO2 film (0.05λ) / Ta film (0.05λ) / SiO2 film (0.05λ) / Ta film (0.05λ) / SiO2 film (0.05λ) / Ta film (0.05λ) / Si substrate. In Figure 25, the metallization ratio (MR) of the curtain-shaped electrode 12a is set to 0.5, and the results are shown when Cu electrode, Al electrode, Au electrode, and Mo electrode are used as the curtain-shaped electrode 12a.

[0093] As shown in Figure 25, it was confirmed that with Cu electrodes, an impedance ratio of 65 dB or higher was obtained when the electrode thickness was 0.01 to 0.033 wavelengths and 0.06 to 0.2 wavelengths, an impedance ratio of 70 dB or higher was obtained when the electrode thickness was 0.014 to 0.03 wavelengths and 0.07 to 0.18 wavelengths, and an impedance ratio of 75 dB or higher was obtained when the electrode thickness was 0.1 to 0.14 wavelengths. Furthermore, it was confirmed that with Al electrodes, an impedance ratio of 65 dB or higher was obtained when the electrode thickness was 0.01 to 0.045 wavelengths and 0.1 to 0.21 wavelengths, an impedance ratio of 70 dB or higher was obtained when the electrode thickness was 0.02 to 0.041 wavelengths and 0.135 to 0.197 wavelengths, and an impedance ratio of 75 dB or higher was obtained when the electrode thickness was 0.159 to 0.182 wavelengths.

[0094] Furthermore, it was confirmed that with Au electrodes, an impedance ratio of 65 dB or higher was obtained when the electrode thickness was 0.005 to 0.02 wavelengths and 0.062 to 0.165 wavelengths, an impedance ratio of 70 dB or higher was obtained when the electrode thickness was 0.01 to 0.0152 wavelengths and 0.064 to 0.155 wavelengths, and an impedance ratio of 75 dB or higher was obtained when the electrode thickness was 0.08 to 0.12 wavelengths. Furthermore, it was confirmed that with Mo electrodes, an impedance ratio of 65 dB or higher was obtained when the electrode thickness was 0.008 to 0.03 wavelengths and 0.055 to 0.19 wavelengths, an impedance ratio of 70 dB or higher was obtained when the electrode thickness was 0.0125 to 0.027 wavelengths and 0.065 to 0.165 wavelengths, and an impedance ratio of 75 dB or higher was obtained when the electrode thickness was 0.095 to 0.13 wavelengths.

[0095] The blind-shaped electrode 12a has a density of 1800 kg / m³. 3 More than 6000kg / m 3 When the value is less than 6000 kg / m², the optimal electrode thickness is the same as that of the Al electrode. 3 More than 10000kg / m 3 When the value is less than 10,000 kg / m², the optimal electrode thickness is the same as that of the Cu electrode. 3 More than 15000kg / m 3 When the value is less than 15,000 kg / m², the optimal electrode thickness is the same as that of the Mo electrode. 3 More than 25000kg / m 3 When the value is less than 0.5, the optimal electrode thickness is the same as that of the Au electrode. Here, if the lattice-like electrode 12a is made of an alloy or a multilayer metal film, the optimal thickness is determined by converting it using its average density. When the metallization ratio (MR) of the lattice-like electrode 12a deviates from 0.5, if H is the optimal thickness when MR is 0.5, then H × 0.5 / MR becomes the optimal thickness.

[0096] Figure 26 shows the dependence of the impedance ratio of the lattice-shaped electrode 12a on the MR when the elastic wave device 10 shown in Figure 1(b) is Cu(0.1λ) / (90°,90°,42.5°)LN(0.2λ) / floating electrode / SiO2 film(0.05λ) / Ta film(0.05λ) / SiO2 film(0.05λ) / Ta film(0.05λ) / SiO2 film(0.05λ) / Ta film(0.05λ) / Si substrate, and when it is Cu(0.1λ) / (90°,90°,35°)LT(0.15λ) / floating electrode / SiO2 film(0.05λ) / Ta film(0.05λ) / SiO2 film(0.05λ) / SiO2 film(0.05λ) / Ta film(0.05λ) / Si substrate. As shown in Figure 26, it was confirmed that for both LN and LT, an impedance ratio of 65 dB or higher could be obtained when MR was between 0.35 and 0.8. Furthermore, for LN, an impedance ratio of 70 dB or higher could be obtained when MR was between 0.45 and 0.8, and for LT, an impedance ratio of 68 dB or higher could be obtained when MR was between 0.45 and 0.6.

[0097] [Comparison with Patent Document 3] The characteristics excited near 5.1 GHz shown in Figure 3(a) correspond to an LLSAW with a sound velocity of 6,100 m / s. In contrast, Patent Document 3 uses Al electrodes with thicknesses of 0.05, 0.06, and 0.08 wavelengths to excite an LLSAW, but as shown in Figure 25, the Al electrode thickness is insufficient to significantly excite the SAW overtone.

[0098] Furthermore, Figure 27(a) shows the displacement distribution of the frequency characteristics at a sound velocity of 6,200 m / s, corresponding to LLSAW, for a structure consisting of Al(0.05λ) / 0.2 wavelength (90°,90°,40°)LN(0.2λ) / acoustic multilayer films [Multi acoustic layers; SiO2(0.25λ) / Ta(0.25λ) / SiO2(0.25λ) / Ta(0.25λ) / SiO2(0.25λ) / Ta(0.25λ)] / Si substrate, which corresponds to the elastic wave device shown in Patent Document 3. As shown in Figure 27(a), the displacement distribution is mainly longitudinal wave components ("L" in the figure), and it was confirmed that the excited vibration is LLSAW as shown in Patent Document 3.

[0099] On the other hand, Figure 27(b) shows the displacement distribution of the frequency characteristics of the overtone near a sound velocity of 11,000 m / s for the elastic wave device 10 shown in Figure 1(a), when it is constructed of Cu(0.1λ) / (90°,90°,42.5°)LN(0.2λ) / acoustic multilayer film [Multi acoustic layers;SiO2(0.05λ) / Ta(0.05λ) / SiO2(0.05λ) / Ta(0.05λ) / SiO2(0.05λ) / Ta(0.05λ)] / Si substrate. As shown in Figure 27(b), the displacement distribution was confirmed to be SAW with SH components as the main component. Thus, it is clear that the vibration modes are also different between the elastic wave device of Patent Document 3 and the elastic wave device 10 of the embodiment of the present invention, due to differences in frequency and sound velocity, differences between the basic mode of LLSAW and the overtone of SAW, and completely different displacement distributions. [Explanation of symbols]

[0100] 10. Elastic wave devices 11 Piezoelectric substrate 12 electrodes 12a Bamboo blind-shaped electrode 12b Floating electrode 13 Acoustic multilayer film 13a Low acoustic impedance film 13b High Acoustic Impedance Film 14 Support substrate

Claims

1. Piezoelectric substrate and An electrode consisting of a curtain-shaped electrode is provided so as to be in contact with the piezoelectric substrate, The piezoelectric substrate or the acoustic multilayer film provided in contact with the electrode, The electrode is configured to be provided on the surface of the piezoelectric substrate opposite to the acoustic multilayer film, or between the piezoelectric substrate and the acoustic multilayer film. The acoustic multilayer film has an acoustic film in which low acoustic impedance films and high acoustic impedance films are alternately laminated in a continuous order of 3 to 20 layers, and the thickness of at least three layers of each low acoustic impedance film and each high acoustic impedance film of the acoustic multilayer film is such that the wavelengths of the fundamental modes of surface acoustic waves are 0.012 to 0.118 wavelengths, 0.105 to 0.2 wavelengths, or 0.216 to 0.275 wavelengths, respectively. The acoustic multilayer film makes it possible to excite the overtones among the resonance characteristics of the surface acoustic wave. Using the aforementioned overtone A characteristic elastic wave device.

2. Piezoelectric substrate and An electrode consisting of a curtain-shaped electrode and a floating electrode is provided so as to be in contact with the surface of the piezoelectric substrate, It has an acoustic multilayer film, The blind-shaped electrode is provided on the surface of the piezoelectric substrate opposite to the acoustic multilayer film, and the floating electrode is provided between the piezoelectric substrate and the acoustic multilayer film, or the blind-shaped electrode is provided between the piezoelectric substrate and the acoustic multilayer film, and the floating electrode is provided on the surface of the piezoelectric substrate opposite to the acoustic multilayer film. The acoustic multilayer film has an acoustic film in which low acoustic impedance films and high acoustic impedance films are alternately laminated in a continuous order of 3 to 20 layers, and the thickness of at least three layers of each low acoustic impedance film and each high acoustic impedance film of the acoustic multilayer film is such that the wavelengths of the fundamental modes of surface acoustic waves are 0.012 to 0.118 wavelengths, 0.105 to 0.2 wavelengths, or 0.216 to 0.275 wavelengths, respectively. The acoustic multilayer film makes it possible to excite the overtones among the resonance characteristics of the surface acoustic wave. Using the aforementioned overtone A characteristic elastic wave device.

3. The acoustic wave device according to claim 1 or 2, characterized in that the acoustic multilayer film is alternately laminated with a low acoustic impedance film and a high acoustic impedance film.

4. Each low-acoustic impedance film and / or each high-acoustic impedance film of the aforementioned acoustic multilayer film is made of Mg alloy, SiO ２ , Al, Y, Si, Ge, Ti, ZnO, Si ｘ N ｙ (where x and y are positive real numbers), AlN, SiC, Al ２ O ３ Ag, ZrO ２ , Hf, Cu, TiO ２ The acoustic wave device according to any one of claims 1 to 3, characterized in that it comprises a film containing at least one of Cr, Ni, Au, Ta, Mo, Pt, and W, or an oxide film, nitride film, carbide film, or iodide film containing at least one of these.

5. The piezoelectric substrate is LiNbO ３ or LiTaO ３ The elastic wave device according to any one of claims 1 to 4, characterized in that it is made of a single crystal of

6. The electrode consists of a curtain-shaped electrode provided on one surface of the piezoelectric substrate. The acoustic multilayer film is provided so as to be in contact with the other surface of the piezoelectric substrate, The piezoelectric substrate is LiNbO ３ It is made of crystals and has Euler angles that are one of the following: (-30° to 30°, 60° to 103°, -15° to 15°) and (90°±6°, 90°±6°, -20° to 48°), or crystallographically equivalent to either of these Euler angles. The elastic wave device according to claim 1, characterized by the features described above.

7. The electrode comprises a curtain-shaped electrode provided on one surface of the piezoelectric substrate and a floating electrode provided to cover the other surface of the piezoelectric substrate. The acoustic multilayer film is provided so as to be in contact with the surface of the floating electrode opposite to the piezoelectric substrate, The piezoelectric substrate is LiNbO ３ It is made of crystals and has an Euler angle that is one of the following: (-30° to 30°, 64° to 98°, -15° to 15°) and (90°±6°, 90°±6°, -4° to 56°), or an Euler angle that is crystallographically equivalent to one of these. The elastic wave device according to claim 2, characterized by its features.

8. The elastic wave device according to claim 6 or 7, characterized in that the piezoelectric substrate has a thickness of 0.002 to 5 wavelengths of the fundamental mode of the surface acoustic wave.

9. The electrode consists of a curtain-shaped electrode provided on one surface of the piezoelectric substrate. The acoustic multilayer film is provided so as to be in contact with the other surface of the piezoelectric substrate, The piezoelectric substrate is LiTaO ３ It is made of crystals and has an Euler angle of one of the following: (-30° to 30°, 55° to 100°, -15° to 15°), (90°±6°, 90°±6°, -5° to 61°), and (90°±6°, 90°±6°, 83° to 93°), or an Euler angle that is crystallographically equivalent to one of these. The elastic wave device according to claim 1, characterized by the features described above.

10. The electrode comprises a curtain-shaped electrode provided on one surface of the piezoelectric substrate and a floating electrode provided to cover the other surface of the piezoelectric substrate. The acoustic multilayer film is provided so as to be in contact with the surface of the floating electrode opposite to the piezoelectric substrate, The piezoelectric substrate is LiTaO ３ It is made of crystals and has an Euler angle that is one of the following: (-30° to 30°, 65° to 94°, -15° to 15°) and (90°±6°, 90°±6°, -4° to 56°), or an Euler angle that is crystallographically equivalent to one of these. The elastic wave device according to claim 2, characterized by its features.

11. The elastic wave device according to claim 9 or 10, characterized in that the piezoelectric substrate has a thickness of 0.002 to 2.4 wavelengths of the fundamental mode of the surface acoustic wave.

12. The aforementioned curtain-like electrode has a density of 1800 kg / m³, where MR is the metallization ratio and λ is the wavelength of the fundamental mode of the surface acoustic wave. ３ More than 6000kg / m ３ Less than , with a thickness of (0.01λ to 0.045λ) × 0.5 / MR or (0.1λ to 0.21λ) × 0.5 / MR, or a density of 6000 kg / m³ ３ More than 10000kg / m ３ Less than , with a thickness of (0.01λ to 0.033λ) × 0.5 / MR or (0.06λ to 0.2λ) × 0.5 / MR, or a density of 10,000 kg / m³ ３ More than 15000kg / m ３ Less than , with a thickness of (0.008λ to 0.03λ) × 0.5 / MR or (0.055λ to 0.19λ) × 0.5 / MR, or a density of 15,000 kg / m³ ３ More than 25000kg / m ３ An elastic wave device according to any one of claims 6 to 11, characterized in that it is less than and has a thickness of (0.005λ to 0.02λ) × 0.5 / MR or (0.062λ to 0.165λ) × 0.5 / MR.

13. The elastic wave device according to any one of claims 6 to 11, characterized in that the aforementioned curtain-shaped electrode has a metallization ratio of 0.35 or more.

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