Elastic wave device and communication device

Abstract

Achieved is an elastic wave device that has a small frequency-temperature dependence and has a wide width between a resonance frequency and an anti-resonance frequency. At least one of a plate wave and a bulk wave is excited. The present invention has: a piezoelectric layer that includes lithium niobate; an IDT electrode; and a dielectric layer that has a positive frequency-temperature coefficient. The Euler angles of the piezoelectric layer are (0°, 30° to 42°, 0°). The result of mathematical expression (1) is 0.60 to 0.75. Mathematical expression (1): Thickness of the piezoelectric layer / (thickness of the piezoelectric layer + thickness of the dielectric layer)

Description

Acoustic wave devices and communication devices

[0001] The present disclosure relates to an acoustic wave device and a communication device.

[0002] Patent Document 1 discloses an elastic wave device that includes a piezoelectric layer containing lithium niobate and excites an A1 mode Lamb wave or a thickness shear mode bulk wave.

[0003] WO2024 / 034528 publication

[0004] An elastic wave device according to one aspect of the present disclosure is an elastic wave device that has a resonance portion and excites at least one of a plate wave and a bulk wave, wherein the resonance portion includes: a piezoelectric layer that includes lithium niobate and has a first surface; an IDT electrode located on the first surface side, having a first side surface, and having a plurality of electrode fingers arranged at a repeating interval p; and a dielectric layer located on the first surface side, having a second side surface facing the first side surface, and having a positive frequency temperature coefficient, wherein the Euler angles of the piezoelectric layer are (0°, 30° or more and 42° or less, 0°), and a solution of equation (1) below: thickness of the piezoelectric layer / (thickness of the piezoelectric layer + thickness of the dielectric layer) (1) is 0.60 or more and 0.75 or less.

[0005] 1 is a side view showing a schematic configuration of an elastic wave device according to a first embodiment of the present disclosure.

[0023] FIG. 1 shows the characteristics of TCFr, TCFa, and df when the LN ratio is changed from 0.5 to 0.8 according to the first embodiment of the present disclosure.

[0024] FIG. 1 shows the characteristics of TCFr, TCFa, and df when the LN ratio is changed from 0.5 to 0.7 in a membrane structure described below.

[0025] FIG. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 26°, 0°) and the LN ratio is 0.65 according to the first embodiment of the present disclosure.

[0026] FIG. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 26°, 0°) and the LN ratio is 0.70 according to the first embodiment of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 26°, 0°) and the LN ratio is 0.75 according to a first embodiment of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 30°, 0°) and the LN ratio is 0.65 according to a first embodiment of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 30°, 0°) and the LN ratio is 0.70 according to a first embodiment of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 30°, 0°) and the LN ratio is 0.75 according to a first embodiment of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 34°, 0°) and the LN ratio is 0.65 according to a first embodiment of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 34°, 0°) and the LN ratio is 0.70 according to a first embodiment of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 34°, 0°) and the LN ratio is 0.75 according to a first embodiment of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 38°, 0°) and the LN ratio is 0.65 according to a first embodiment of the present disclosure.1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 38°, 0°) and the LN ratio is 0.70 according to a first embodiment of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 38°, 0°) and the LN ratio is 0.75 according to a first embodiment of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 42°, 0°) and the LN ratio is 0.65 according to a first embodiment of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 42°, 0°) and the LN ratio is 0.70 according to a first embodiment of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 42°, 0°) and the LN ratio is 0.75 according to the first embodiment of the present disclosure. FIG. 1 is a table illustrating a specific example of the configuration of an elastic wave device according to the first embodiment of the present disclosure. FIG. 2 is a side view illustrating a specific example of the configuration of an elastic wave device according to the first embodiment of the present disclosure. FIG. 3 is a first graph illustrating frequency characteristics of impedance in a specific example of the configuration of an elastic wave device according to the first embodiment of the present disclosure. FIG. 4 is a side view illustrating a schematic configuration of an elastic wave device according to the second embodiment of the present disclosure. FIG. 5 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 34°, 0°), the LN ratio is 0.65, and the thickness of the IDT electrode is 0.09 μm according to the second embodiment of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 34°, 0°), the LN ratio is 0.70, and the thickness of the IDT electrode is 0.09 μm according to embodiment 2 of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 34°, 0°), the LN ratio is 0.75, and the thickness of the IDT electrode is 0.09 μm according to embodiment 2 of the present disclosure.1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 34°, 0°), the LN ratio is 0.70, and the thickness of the IDT electrode is 0.05 μm according to embodiment 2 of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 34°, 0°), the LN ratio is 0.70, and the thickness of the IDT electrode is 0.07 μm according to embodiment 2 of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 26°, 0°), the LN ratio is 0.65, and the thickness of the IDT electrode is 0.07 μm according to embodiment 2 of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 26°, 0°), the LN ratio is 0.70, and the thickness of the IDT electrode is 0.07 μm according to embodiment 2 of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 26°, 0°), the LN ratio is 0.75, and the thickness of the IDT electrode is 0.07 μm according to embodiment 2 of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 30°, 0°), the LN ratio is 0.65, and the thickness of the IDT electrode is 0.07 μm according to embodiment 2 of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 30°, 0°), the LN ratio is 0.70, and the thickness of the IDT electrode is 0.07 μm according to embodiment 2 of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 30°, 0°), the LN ratio is 0.75, and the thickness of the IDT electrode is 0.07 μm according to embodiment 2 of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 34°, 0°), the LN ratio is 0.65, and the thickness of the IDT electrode is 0.07 μm according to embodiment 2 of the present disclosure.1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 34°, 0°), the LN ratio is 0.75, and the thickness of the IDT electrode is 0.07 μm according to embodiment 2 of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 38°, 0°), the LN ratio is 0.65, and the thickness of the IDT electrode is 0.07 μm according to embodiment 2 of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 38°, 0°), the LN ratio is 0.70, and the thickness of the IDT electrode is 0.07 μm according to embodiment 2 of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 38°, 0°), the LN ratio is 0.75, and the thickness of the IDT electrode is 0.07 μm according to embodiment 2 of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 42°, 0°), the LN ratio is 0.65, and the thickness of the IDT electrode is 0.07 μm according to embodiment 2 of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 42°, 0°), the LN ratio is 0.70, and the thickness of the IDT electrode is 0.07 μm according to embodiment 2 of the present disclosure. 1 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer are (0°, 42°, 0°), the LN ratio is 0.75, and the thickness of the IDT electrode is 0.07 μm according to a second embodiment of the present disclosure.

[0034] FIG. 1 is a table illustrating a first specific example of the configuration of an elastic wave device according to the second embodiment of the present disclosure.

[0035] FIG. 2 is a side view illustrating first and second specific examples of the configuration of an elastic wave device according to the second embodiment of the present disclosure.

[0036] FIG. 3 is a first graph illustrating frequency characteristics of impedance in a first specific example of the configuration of an elastic wave device according to the second embodiment of the present disclosure.

[0037] FIG. 4 is a table illustrating a second specific example of the configuration of an elastic wave device according to the second embodiment of the present disclosure.

[0038] FIG. 5 is a first graph illustrating frequency characteristics of impedance in a second specific example of the configuration of an elastic wave device according to the second embodiment of the present disclosure.FIG. 2 is a second graph showing frequency characteristics of impedance in a second specific example of the configuration of an elastic wave device according to Example 2 of the present disclosure. FIG. 3 is a side view showing a schematic configuration of a first example of an elastic wave device according to Example 3 of the present disclosure. FIG. 4 is a side view showing a schematic configuration of a second example of an elastic wave device according to Example 3 of the present disclosure. FIG. 5 is a side view showing a schematic configuration of a third example of an elastic wave device according to Example 3 of the present disclosure. FIG. 6 is a side view showing a schematic configuration of a fourth example of an elastic wave device according to Example 3 of the present disclosure. FIG. 7 is a side view showing a schematic configuration of a sixth example of an elastic wave device according to Example 3 of the present disclosure. FIG. 8 is a side view showing a schematic configuration of a seventh example of an elastic wave device according to Example 3 of the present disclosure. FIG. 9 is a side view showing a schematic configuration of an eighth example of an elastic wave device according to Example 3 of the present disclosure. FIG. 10 is a side view showing a schematic configuration of a tenth example of an elastic wave device according to Example 3 of the present disclosure. FIG. 11 is a side view showing a first manufacturing process of an elastic wave device according to Example 4 of the present disclosure. FIG. 12 is a side view showing a second manufacturing process of an elastic wave device according to Example 4 of the present disclosure. 10A to 10D are side views illustrating a third manufacturing process of an elastic wave device according to embodiment 4 of the present disclosure. 10B to 10D are side views illustrating a fourth manufacturing process of an elastic wave device according to embodiment 4 of the present disclosure. 10C to 10D are schematic diagrams of a communication device according to embodiment 5 of the present disclosure.

[0006] The present inventors have devised an elastic wave device that has less frequency temperature dependency and a wider range between the resonant frequency and the antiresonant frequency than the elastic wave device disclosed in Patent Document 1.

[0007] According to one aspect of the present disclosure, an acoustic wave device can be realized that has small frequency temperature dependence and a wide range between the resonant frequency and the antiresonant frequency.

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes an embodiment of the present disclosure. For convenience of explanation, the same reference numerals are used to designate components having the same functions as those previously described, and the description thereof may not be repeated.

[0009] 1 is a side view illustrating a schematic configuration of an elastic wave device 101 according to a first embodiment of the present disclosure. The elastic wave device 101 includes a resonance unit 1. The elastic wave device 101 excites at least one of a plate wave and a bulk wave. The elastic wave device 101 may excite a plate wave such as an A1-mode Lamb wave, a bulk wave such as a thickness-shear-mode bulk wave, or both a plate wave and a bulk wave.

[0010] The resonator section 1 has a piezoelectric layer 2, an IDT electrode 3, and a dielectric layer 4. IDT is an abbreviation for interdigital transducer.

[0011] The piezoelectric layer 2 contains lithium niobate. Lithium niobate is LiNbO ３ The piezoelectric layer 2 has a first surface 5. The Euler angles of the piezoelectric layer 2 are (0°, 30° or more and 42° or less, 0°).

[0012] The IDT electrode 3 is located on the first surface 5 side. The IDT electrode 3 has a first side surface 6. The IDT electrode 3 has a plurality of electrode fingers 7 arranged at a repetition interval p. The repetition interval p may be the pitch of the plurality of electrode fingers 7. Examples of materials for the IDT electrode 3 include Al, an alloy containing Al as a main component, or a laminate of Al and another metal. The main component of a material may be defined as the atom that is contained in the material in the largest number.

[0013] The dielectric layer 4 is located on the first surface 5 side. The dielectric layer 4 has a second side surface 8 opposite to the first side surface 6. The dielectric layer 4 has a positive temperature coefficient of frequency. An example of the main component of the dielectric layer 4 is SiO. ２ , SiOF, SiON, and SiOH. Among these, the main component of the dielectric layer 4 is SiO ２ may be.

[0014] In the elastic wave device 101, the solution of the following equation (1) is greater than or equal to 0.60 and less than or equal to 0.75: thickness T2 of the piezoelectric layer 2 / (thickness T2 of the piezoelectric layer 2+thickness T4 of the dielectric layer 4) (1). Hereinafter, the solution of equation (1) may be referred to as the LN ratio.

[0015] Acoustic wave device 101 can realize an acoustic wave device with small frequency temperature dependence and a wide range between the resonant frequency and the anti-resonant frequency.

[0016] The Euler angles of the piezoelectric layer 2 may be (0°, 34° to 42°, 0°). This allows for the realization of an elastic wave device 101 with a wide range between the resonant frequency and the anti-resonant frequency.

[0017] The sum of thickness T2 of piezoelectric layer 2 and thickness T4 of dielectric layer 4 may be 0.15 to 0.2 times the repeat interval p, or 0.26 to 0.39 times the repeat interval p. This allows for the realization of acoustic wave device 101 with a wide parameter range that minimizes spurious responses.

[0018] The duty of the IDT electrode 3 may be 0.35 or less, thereby realizing an acoustic wave device 101 with small frequency temperature dependence. The duty of the IDT electrode 3 may be defined as the ratio of the sum of the widths of two adjacent electrode fingers 7 to twice the repetition interval p.

[0019] The sum of the thickness T2 of the piezoelectric layer 2 and the thickness T4 of the dielectric layer 4 may be 0.23 times or less the repeat interval p, and the duty of the IDT electrode 3 may be 0.19 or more. This allows for the realization of an acoustic wave device 101 with a wide range between the resonant frequency and the antiresonant frequency.

[0020] The sum of thickness T2 of piezoelectric layer 2 and thickness T4 of dielectric layer 4 may be 0.15 to 0.2 times the repetition interval p, and the duty of IDT electrode 3 may be 0.19 to 0.35. This makes it possible to realize acoustic wave device 101 that has small frequency temperature dependence, a wide range between the resonant frequency and the antiresonant frequency, and a wide parameter range with small spurious responses.

[0021] At least a part of the surfaces 9 of the plurality of electrode fingers 7 located on the opposite side to the first surface 5 may be exposed from the dielectric layer 4 .

[0022] At least a part of the surface 10 of the dielectric layer 4 located on the side opposite to the first surface 5 may be flush with at least a part of the surfaces 9 of the plurality of electrode fingers 7 located on the side opposite to the first surface 5. "At least a part of the surface 10 is flush with at least a part of the surface 9" may mean that the misalignment between at least a part of the surface 9 and at least a part of the surface 10 is 10% or less of the thickness T4 of the dielectric layer 4.

[0023] The piezoelectric layer 2 may have a second surface 11 located on the opposite side of the first surface 5. The acoustic wave device 101 may have an acoustic reflecting film 12. The acoustic reflecting film 12 is located on the second surface 11 side. The acoustic reflecting film 12 includes a low acoustic impedance layer 13 and a high acoustic impedance layer 14.

[0024] The acoustic impedance of the low acoustic impedance layer 13 is lower than the acoustic impedance of the high acoustic impedance layer 14. The low acoustic impedance layer 13 is made of SiO ２ The high acoustic impedance layer 14 may include HfO ２ , Ta ２ O ５ , and ZrO ２ The high acoustic impedance layer 14 may include at least one of W, Mo, Ru, Hf, and Ta.

[0025] The number of layers included in the acoustic reflection film 12 is four in total, two low acoustic impedance layers 13 and two high acoustic impedance layers 14, but is not limited to this. The acoustic reflection film 12 may include one low acoustic impedance layer 13 and one high acoustic impedance layer 14, or three or more layers each.

[0026] A simulation was performed to verify the effects of the elastic wave device 101 according to embodiment 1. The conditions previously determined for the simulation were as follows.

[0027] Euler angles of the piezoelectric layer 2: (0°, 26°, 0°), (0°, 30°, 0°), (0°, 34°, 0°), (0°, 38°, 0°), and (0°, 42°, 0°) are applied depending on the case. Structure of the acoustic reflection film 12: A laminated structure of low acoustic impedance layers 13 and high acoustic impedance layers 14 is repeated four times. Material of the low acoustic impedance layer 13: SiO ２ Thickness of low acoustic impedance layer 13: 0.200 μm Material of high acoustic impedance layer 14: HfO ２ Thickness of the high acoustic impedance layer 14: 0.165 μm; Sum of the thickness T2 of the piezoelectric layer 2 and the thickness T4 of the dielectric layer 4: 0.39 μm; Repetition interval p: 0.5 μm or 0.6 μm to 3.4 μm; Duty of the IDT electrode 3: 0.16 to 0.46; LN ratio: 0.65, 0.70, or 0.75, depending on the case; Thickness of the IDT electrode 3: Same as the thickness T4 of the dielectric layer 4. The conditions for the low acoustic impedance layer 13 and the high acoustic impedance layer 14 are examples of conditions that can reduce leakage of acoustic waves to the substrate at the resonant frequency of the ultra-high frequency SAW resonator of this embodiment, i.e., approximately 5000 MHz. SAW is an abbreviation for surface acoustic wave. Under the condition of the sum of the thickness T2 of the piezoelectric layer 2 and the thickness T4 of the dielectric layer 4, the acoustic wave device 101 resonates around 5000 MHz.

[0028] FOM, TCFa, and df were used as indices for evaluating the effects of elastic wave device 101.

[0029] FOM is an abbreviation for figure of merit. FOM is calculated using the following formula (2): FOM = (90° - average phase value of impedance below resonance frequency) x (90° - average phase value of impedance above anti-resonance frequency) x (90° + minimum phase value of impedance between resonance frequency and anti-resonance frequency) / (180° x 180° x 180°) ... (2). The maximum value of FOM is 1. It can be said that the closer the FOM is to 1, the smaller the spurious.

[0030] TCF is an abbreviation for temperature coefficient of frequency. TCF is also called frequency temperature characteristic and is roughly proportional to half the temperature coefficient of the elastic constant of an elastic wave device. TCF is the rate of change of the resonance or anti-resonance frequency due to temperature normalized by the absolute value of the resonance or anti-resonance frequency, and is usually expressed in units of ppm / K. TCFa is the TCF of the anti-resonance frequency. The closer TCFa is to 0 ppm / K, the smaller the frequency temperature dependence can be said to be.

[0031] df is the ratio of the frequency difference between the anti-resonance frequency and the resonance frequency to the resonance frequency, and its unit is %. The larger df is, the wider the gap between the resonance frequency and the anti-resonance frequency is.

[0032] FIG. 2 shows the TCFr, TCFa, and df characteristics of elastic wave device 101 in accordance with the first preferred embodiment when the LN ratio is changed from 0.5 to 0.8.

[0033] In the elastic wave device 101 according to the first embodiment, the LN ratio may be in the range of 0.6 to 0.75. When the LN ratio is in the range of 0.6 to 0.75, the absolute values ​​of TCFr and TCFa can be reduced. Furthermore, when the LN ratio is in the range of 0.65 to 0.75, the df can be sufficiently increased.

[0034] 3 shows the TCFr, TCFa, and df characteristics when the LN ratio is changed from 0.5 to 0.7 for a membrane structure described below. The same tendency as in elastic wave device 101 according to embodiment 1 having acoustic reflection film 12 is observed for the membrane structure.

[0035] 4 to 18 show simulation results for verifying the effects of the elastic wave device 101 according to the first embodiment.

[0036] Fig. 4 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 26°, 0°) and the LN ratio is 0.65. Fig. 5 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 26°, 0°) and the LN ratio is 0.70. Fig. 6 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 26°, 0°) and the LN ratio is 0.75.

[0037] Fig. 7 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 30°, 0°) and the LN ratio is 0.65. Fig. 8 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 30°, 0°) and the LN ratio is 0.70. Fig. 9 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 30°, 0°) and the LN ratio is 0.75.

[0038] Fig. 10 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 34°, 0°) and the LN ratio is 0.65. Fig. 11 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 34°, 0°) and the LN ratio is 0.70. Fig. 12 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 34°, 0°) and the LN ratio is 0.75.

[0039] Fig. 13 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 38°, 0°) and the LN ratio is 0.65. Fig. 14 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 38°, 0°) and the LN ratio is 0.70. Fig. 15 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 38°, 0°) and the LN ratio is 0.75.

[0040] Fig. 16 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 42°, 0°) and the LN ratio is 0.65. Fig. 17 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 42°, 0°) and the LN ratio is 0.70. Fig. 18 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 42°, 0°) and the LN ratio is 0.75.

[0041] For each of the FOM characteristic, the TCFa characteristic, and the df characteristic, the horizontal axis indicates the repetition interval p, and the vertical axis indicates the duty of the IDT electrode 3.

[0042] 11 reveals the following: In a range 51 where the repetition interval p is 1.0 μm or more and 1.5 μm or less, and in a range 52 where the repetition interval p is 2.0 μm or more and 2.6 μm or less, the FOM is close to 1, and spurious is small. In a range 53 where the duty of the IDT electrode 3 is 0.35 or less, the absolute value of TCFa is 20 ppm / K or less, and the frequency temperature dependence is small. In a range 54 where the repetition interval p is 1.7 μm or more and the duty of the IDT electrode 3 is 0.19 or more, df is 10% or more, and the width between the resonant frequency and the antiresonant frequency is wide.

[0043] The correspondence relationship between the repetition interval p and the sum of the thickness T2 of the piezoelectric layer 2 and the thickness T4 of the dielectric layer 4 is as follows:

[0044] Repeat interval p = 1.0 μm...the sum of the thickness T2 of the piezoelectric layer 2 and the thickness T4 of the dielectric layer 4 = 0.39 times the repeat interval p Repeat interval p = 1.5 μm...the sum of the thickness T2 of the piezoelectric layer 2 and the thickness T4 of the dielectric layer 4 = 0.26 times the repeat interval p Repeat interval p = 2.0 μm...the sum of the thickness T2 of the piezoelectric layer 2 and the thickness T4 of the dielectric layer 4 = 0.20 times the repeat interval p Repeat interval p = 2.6 μm...the sum of the thickness T2 of the piezoelectric layer 2 and the thickness T4 of the dielectric layer 4 = 0.15 times the repeat interval p Repeat interval p = 1.7 μm...the sum of the thickness T2 of the piezoelectric layer 2 and the thickness T4 of the dielectric layer 4 = 0.23 times the repeat interval p Looking at Figures 4 to 18, TCFa and df hardly change with respect to the Euler angles of the piezoelectric layer 2. 4 to 6, it can be seen that the larger the LN ratio, the more the df tends to improve, while the smaller the LN ratio, the more the TCFa tends to improve.

[0045] When the LN ratio is 0.65, there are many conditions where TCFa is close to 0 ppm / K, while df is somewhat small at around 8% to 9%. When the LN ratio is 0.70, df is large at around 10% to 11%, while there are somewhat few conditions where TCFa is close to 0 ppm / K. It can be said that there is a trade-off between TCFa and df, but both TCFa and df are good when the LN ratio is in the range of 0.65 or more and 0.70 or less.

[0046] When the repeat interval p is in the range of 1.0 μm or more and 1.5 μm or less, and when the repeat interval p is in the range of 2.0 μm or more and 2.6 μm or less, the FOM is close to 1, but the former tends to have a smaller df. When the Euler angles of the piezoelectric layer 2 are (0°, 34°, 0°), the effect of the elastic wave device 101 according to embodiment 1 is significant.

[0047] If the duty of the IDT electrode 3 exceeds 0.40, this may adversely affect the TCFa. When the IDT electrode 3 is embedded in the piezoelectric layer 2, the greater the embedding depth, the larger the df becomes, but the smaller the FOM becomes. Therefore, there is little benefit to embedding the IDT electrode 3 in the piezoelectric layer 2.

[0048] In light of the above, the effects of the elastic wave device 101 according to the first embodiment are particularly pronounced in the following configuration, for example.

[0049] Euler angles of piezoelectric layer 2: (0°, 34° to 42°, 0°); LN ratio: 0.65 to 0.70; Repetition interval p: 1.0 μm to 1.5 μm, or 2.0 μm to 2.6 μm; Duty of IDT electrode 3: 0.19 to 0.35. FIG. 19 is a table illustrating a specific example of the configuration of elastic wave device 101 according to embodiment 1. FIG. 20 is a side view illustrating a specific example of the configuration of elastic wave device 101 according to embodiment 1. FIG. 21 is a first graph illustrating impedance-frequency characteristics for a specific example of the configuration of elastic wave device 101 according to embodiment 1. FIG. 22 is a second graph illustrating impedance-frequency characteristics for a specific example of the configuration of elastic wave device 101 according to embodiment 1.

[0050] The acoustic wave device 101 may include a support substrate 50. The support substrate 50 is a substrate that supports the resonator unit 1 and the acoustic reflection film 12, and an example of a material for the support substrate 50 is Si. The TCF of the acoustic wave device 101 can be improved due to stress generated in the support substrate 50.

[0051] 23 is a side view illustrating a schematic configuration of an elastic wave device 101 according to a second embodiment of the present disclosure. At least a portion of a surface 9 of each of the electrode fingers 7 opposite the first surface 5 may be covered with at least a portion of the dielectric layer 4. At least a portion of the dielectric layer 4 may be located on the opposite side of the first surface 5 from at least a portion of a surface 9 of each of the electrode fingers 7 opposite the first surface 5.

[0052] A simulation was performed to verify the effects of the elastic wave device 101 according to Embodiment 2. The predetermined conditions in the simulation were the same as those in the simulation to verify the effects of the elastic wave device 101 according to Embodiment 1, except for the following.

[0053] Thickness of IDT electrode 3: 0.05 μm, 0.07 μm, or 0.09 μm is applied depending on the case. FIGS. 24 to 42 each show the results of a simulation performed to verify the effects of elastic wave device 101 according to the second embodiment.

[0054] Fig. 24 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 34°, 0°), the LN ratio is 0.65, and the thickness of the IDT electrode 3 is 0.09 μm. Fig. 25 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 34°, 0°), the LN ratio is 0.70, and the thickness of the IDT electrode 3 is 0.09 μm. Fig. 26 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 34°, 0°), the LN ratio is 0.75, and the thickness of the IDT electrode 3 is 0.09 μm.

[0055] Fig. 27 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 34°, 0°), the LN ratio is 0.70, and the thickness of the IDT electrode 3 is 0.05 μm. Fig. 28 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 34°, 0°), the LN ratio is 0.70, and the thickness of the IDT electrode 3 is 0.07 μm.

[0056] Fig. 29 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 26°, 0°), the LN ratio is 0.65, and the thickness of the IDT electrode 3 is 0.07 μm. Fig. 30 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 26°, 0°), the LN ratio is 0.70, and the thickness of the IDT electrode 3 is 0.07 μm. Fig. 31 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 26°, 0°), the LN ratio is 0.75, and the thickness of the IDT electrode 3 is 0.07 μm.

[0057] Fig. 32 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 30°, 0°), the LN ratio is 0.65, and the thickness of the IDT electrode 3 is 0.07 μm. Fig. 33 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 30°, 0°), the LN ratio is 0.70, and the thickness of the IDT electrode 3 is 0.07 μm. Fig. 34 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 30°, 0°), the LN ratio is 0.75, and the thickness of the IDT electrode 3 is 0.07 μm.

[0058] Fig. 35 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 34°, 0°), the LN ratio is 0.65, and the thickness of the IDT electrode 3 is 0.07 μm. Fig. 36 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 34°, 0°), the LN ratio is 0.75, and the thickness of the IDT electrode 3 is 0.07 μm.

[0059] Fig. 37 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 38°, 0°), the LN ratio is 0.65, and the thickness of the IDT electrode 3 is 0.07 μm. Fig. 38 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 38°, 0°), the LN ratio is 0.70, and the thickness of the IDT electrode 3 is 0.07 μm. Fig. 39 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 38°, 0°), the LN ratio is 0.75, and the thickness of the IDT electrode 3 is 0.07 μm.

[0060] Fig. 40 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 42°, 0°), the LN ratio is 0.65, and the thickness of the IDT electrode 3 is 0.07 μm. Fig. 41 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 42°, 0°), the LN ratio is 0.70, and the thickness of the IDT electrode 3 is 0.07 μm. Fig. 42 shows the characteristics of FOM, TCFa, and df when the Euler angles of the piezoelectric layer 2 are (0°, 42°, 0°), the LN ratio is 0.75, and the thickness of the IDT electrode 3 is 0.07 μm.

[0061] 24 to 26, it can be seen that the larger the LN ratio, the more the df tends to improve, while the smaller the LN ratio, the more the TCFa tends to improve. When the LN ratio is 0.70, both the TCFa and df are good.

[0062] 25, 27, and 28, the following can be seen: FOM and df hardly change with the thickness of the IDT electrode 3. As the thickness of the IDT electrode 3 decreases, TCFa tends to improve, but the electrical resistance increases.

[0063] 11 and 25 reveal the following: There is no significant difference in FOM, TCFa, or df between the elastic wave device 101 according to Embodiment 1 and the elastic wave device 101 according to Embodiment 2. The elastic wave device 101 according to Embodiment 2 is slightly better than the elastic wave device 101 according to Embodiment 1 in terms of TCFa and df.

[0064] 29 to 42 reveal the following: When the Euler angles of the piezoelectric layer 2 are (0°, 34° or more and 38° or less, 0°), the effect of the elastic wave device 101 according to Embodiment 2 is significant. The Euler angles of the piezoelectric layer 2 at which the effect of the elastic wave device 101 is significant are similar between Embodiments 1 and 2.

[0065] The dependence of the piezoelectric layer 2 on the Euler angles and the LN ratio is similar between the first and second embodiments.

[0066] In light of the above, the effects of the elastic wave device 101 according to the second embodiment are particularly pronounced in the following configuration, for example.

[0067] Euler angles of piezoelectric layer 2: (0°, 34° to 42°, 0°); LN ratio: 0.65 to 0.70; Repetition interval p: 1.0 μm to 1.5 μm, or 2.0 μm to 2.6 μm; Duty of IDT electrode 3: 0.19 to 0.35. FIG. 43 is a table illustrating a first specific example of the configuration of elastic wave device 101 according to embodiment 2. FIG. 44 is a side view illustrating a first specific example of the configuration of elastic wave device 101 according to embodiment 2. FIG. 45 is a first graph illustrating frequency characteristics of impedance in the first specific example of the configuration of elastic wave device 101 according to embodiment 2. FIG. 46 is a second graph illustrating frequency characteristics of impedance in the first specific example of the configuration of elastic wave device 101 according to embodiment 2. The first specific example focuses on the fact that df is large when the LN ratio is 0.75.

[0068] FIG. 47 is a table illustrating a second specific example of the configuration of elastic wave device 101 according to embodiment 2. FIG. 44 is also a side view illustrating the second specific example of the configuration of elastic wave device 101 according to embodiment 2. FIG. 48 is a first graph illustrating the frequency characteristics of impedance in the second specific example of the configuration of elastic wave device 101 according to embodiment 2. FIG. 49 is a second graph illustrating the frequency characteristics of impedance in the second specific example of the configuration of elastic wave device 101 according to embodiment 2. The second specific example is an example that focuses on achieving both a large df and a TCFa close to 0 ppm / K when the LN ratio is 0.70.

[0069] 50 is a side view illustrating a schematic configuration of a first example of an elastic wave device 101 according to a third embodiment of the present disclosure. As in the first example, at least some of the surfaces 9 of the electrode fingers 7 opposite the first surface 5 may be located on the opposite side of the first surface 5 with respect to at least some of the surfaces 10 of the dielectric layer 4 opposite the first surface 5.

[0070] 51 is a side view illustrating a schematic configuration of a second example of an elastic wave device 101 in accordance with Embodiment 3. As in the second example, at least a portion of the dielectric layer 4 may be located on the opposite side of the first surface 5 with respect to at least a portion of the surfaces 9 of the electrode fingers 7 located on the opposite side of the first surface 5.

[0071] Fig. 52 is a side view showing a schematic configuration of a third example of an elastic wave device 101 according to Embodiment 3. Fig. 53 is a side view showing a schematic configuration of a fourth example of an elastic wave device 101 according to Embodiment 3. Fig. 54 is a side view showing a schematic configuration of a fifth example of an elastic wave device 101 according to Embodiment 3. Fig. 55 is a side view showing a schematic configuration of a sixth example of an elastic wave device 101 according to Embodiment 3.

[0072] As in each of the third to sixth examples, the acoustic wave device 101 may have a membrane structure. The acoustic wave device 101 having a membrane structure does not need to include the acoustic reflection film 12. In the acoustic wave device 101 having a membrane structure, an opening may be located on the piezoelectric layer 2 side of the support substrate 50, and the piezoelectric layer 2 may be located so as to cover the opening.

[0073] The third example corresponds to the elastic wave device 101 in accordance with Embodiment 2. The fourth example corresponds to the first example. The fifth example corresponds to the elastic wave device 101 in accordance with Embodiment 1. The sixth example corresponds to the second example.

[0074] 56 is a side view illustrating a schematic configuration of a seventh example of an elastic wave device 101 in accordance with Embodiment 3. As in the seventh example, the first surface 5 may have grooves 15, and at least some of the plurality of electrode fingers 7 may be located inside the grooves 15.

[0075] 57 is a side view illustrating a schematic configuration of an eighth example of an elastic wave device 101 in accordance with Embodiment 3. As in the eighth example, the first side surface 6 and the second side surface 8 may be spaced apart.

[0076] 58 is a side view showing a schematic configuration of a ninth example of an elastic wave device 101 in accordance with Embodiment 3. As in the ninth example, the elastic wave device 101 may include a first resonator 16 and a second resonator 17. The resonant frequency corresponding to the second resonator 17 is lower than the resonant frequency corresponding to the first resonator 16. As in the ninth example, the portion 19 of the dielectric layer 4 corresponding to the second resonator 17 may be thicker than the portion 18 of the dielectric layer 4 corresponding to the first resonator 16. This allows for the elastic wave device 101 to have a thickness T4 of the dielectric layer 4 that is adapted to the difference in resonant frequency between the first resonator 16 and the second resonator 17.

[0077] 59 is a side view illustrating a schematic configuration of a tenth example of an elastic wave device 101 in accordance with Embodiment 3. As in the tenth example, at least some of the electrode fingers 7 may be in contact with at least some of the surface 10 of the dielectric layer 4 opposite to the first surface 5.

[0078] 60 is a side view illustrating a first manufacturing process for an elastic wave device 101 according to a fourth embodiment of this disclosure. The first manufacturing process can also be considered a manufacturing process for the elastic wave device 101 according to the first embodiment.

[0079] The first manufacturing process includes steps S1 to S6. In step S1, a laminated structure of an acoustic reflection film 12 and a piezoelectric layer 2 is prepared. In step S2, a first dielectric film 55 is formed on the first surface 5. In step S3, a photoresist 57 is formed on a portion of a surface 56 of the first dielectric film 55 opposite the first surface 5. In step S4, unnecessary portions of the first dielectric film 55 are removed by etching, thereby patterning the first dielectric film 55. In step S5, a metal film 58 made of, for example, Al is formed on the portion from which the first dielectric film 55 has been removed and on the photoresist 57. In step S5, the difference in thickness between the first dielectric film 55 and the metal film 58 is set to 10% or less of the thickness of the first dielectric film 55. In step S6, the photoresist 57 and the portion of the metal film 58 that is exposed to the photoresist 57 are removed, thereby forming the IDT electrode 3. In the first manufacturing process, the portion of the first dielectric film 55 remaining at the end of step S6 is used as the dielectric layer 4.

[0080] 61 is a side view illustrating a second manufacturing process for the elastic wave device 101 according to Embodiment 4. The second manufacturing process can also be considered a manufacturing process for the elastic wave device 101 according to Embodiment 2.

[0081] The second manufacturing process includes steps S1 to S7. Steps S1 to S6 have been explained in the description of the first manufacturing process, so they will not be shown in FIG. 61 and their explanation will be omitted. In step S7, a second dielectric film 59 is formed on the IDT electrode 3 and the first dielectric film 55. In the second manufacturing process, the second dielectric film 59, in addition to the portion of the first dielectric film 55 that remains at the end of step S6, becomes the dielectric layer 4.

[0082] 62 is a side view illustrating a third manufacturing process for the elastic wave device 101 according to Embodiment 4. The third manufacturing process can also be considered a ninth example manufacturing process for the elastic wave device 101 according to Embodiment 3.

[0083] The third manufacturing process includes steps S1 to S6 and S8. Steps S1 to S6 have been explained in the description of the first manufacturing process, so they will not be illustrated in FIG. 62 and their explanation will be omitted. In step S8, a third dielectric film 60 is formed on the IDT electrode 3 and the first dielectric film 55. In step S8, a portion 62 of the third dielectric film 60 corresponding to the second resonator 17 is formed thicker than a portion 61 of the third dielectric film 60 corresponding to the first resonator 16. In the third manufacturing process, the third dielectric film 60, together with the portion of the first dielectric film 55 remaining at the end of step S6, becomes the dielectric layer 4.

[0084] 63 is a side view illustrating a fourth manufacturing process for the elastic wave device 101 according to Embodiment 4. The fourth manufacturing process can also be considered a first example manufacturing process for the elastic wave device 101 according to Embodiment 3.

[0085] The fourth manufacturing process differs from the first manufacturing process in that in step S5, the thickness of metal film 58 is formed to be greater than the thickness of first dielectric film 55. Steps S1 to S4 are the same in the first manufacturing process and the fourth manufacturing process, and therefore will not be illustrated in FIG.

[0086] 64 is a schematic diagram of a communication device 201 according to a fifth embodiment of the present disclosure. The communication device 201 is an application example of the acoustic wave device 101, and performs wireless communication using radio waves. The communication device 201 may include a transmit filter 111 and a receive filter 112. Each of the transmit filter 111 and the receive filter 112 may include the acoustic wave device 101.

[0087] In the communication device 201, a transmission information signal TIS containing information to be transmitted may be modulated and frequency-raised by an RF-IC 113 and converted into a transmission signal TS. RF-IC is an abbreviation for radio frequency-integrated circuit. In other words, frequency-raising is conversion into a high-frequency signal having a carrier frequency. A band-pass filter 114 may remove unnecessary components from the transmission signal TS outside the transmission passband. Next, the transmission signal TS after removing the unnecessary components may be amplified by an amplifier 115 and input to the transmission filter 111.

[0088] The transmission filter 111 may remove unnecessary components outside the transmission passband from the input transmission signal TS. The transmission filter 111 may output the transmission signal TS after removing the unnecessary components to the antenna 116 via the antenna terminal. The antenna 116 may convert the transmission signal TS, which is an electrical signal input thereto, into radio waves as a wireless signal and transmit the radio signals to the outside of the communication device 201.

[0089] The antenna 116 may convert a received external radio wave into a received signal RS, which is an electrical signal, and input the received signal RS to the receive filter 112 via the antenna terminal. The receive filter 112 may remove unnecessary components outside the receive passband from the input received signal RS. The receive filter 112 may output the received signal RS after the unnecessary components have been removed to the amplifier 117. The output received signal RS may be amplified by the amplifier 117. The bandpass filter 118 may remove unnecessary components outside the receive passband from the amplified received signal RS. The received signal RS after the unnecessary components have been removed may be frequency-downgraded and demodulated by the RF-IC 113, and converted into a received information signal RIS.

[0090] The transmit information signal TIS and the receive information signal RIS may be low-frequency signals containing appropriate information. The low-frequency signals may be baseband signals. For example, the transmit information signal TIS and the receive information signal RIS may be analog audio signals or digitized audio signals. The passband of the radio signals may be set appropriately and may comply with various known standards.

[0091] [Summary] An elastic wave device according to a first aspect of the present disclosure is an elastic wave device that has a resonance portion and excites at least one of a plate wave and a bulk wave, wherein the resonance portion includes lithium niobate and includes: a piezoelectric layer having a first surface; an IDT electrode located on the first surface side, having a first side surface, and having a plurality of electrode fingers arranged at a repeating interval p; and a dielectric layer located on the first surface side, having a second side surface opposing the first side surface, and having a positive frequency temperature coefficient, wherein the Euler angle of the piezoelectric layer is (0°, 30° or more and 42° or less, 0°), and a solution of equation (1) below: thickness of the piezoelectric layer / (thickness of the piezoelectric layer + thickness of the dielectric layer) (1) is 0.60 or more and 0.75 or less.

[0092] According to a second aspect of the present disclosure, in the elastic wave device of the first aspect, the Euler angles of the piezoelectric layer are (0°, 34° or more and 42° or less, 0°).

[0093] The elastic wave device according to aspect 3 of the present disclosure is the same as that according to aspect 1 or 2, wherein the sum of the thickness of the piezoelectric layer and the thickness of the dielectric layer is 0.15 to 0.2 times the repeat interval p, or 0.26 to 0.39 times the repeat interval p.

[0094] According to a fourth aspect of the present disclosure, in the elastic wave device of the first or second aspect, the duty of the IDT electrode is 0.35 or less.

[0095] The elastic wave device according to aspect 5 of the present disclosure is the same as that of aspect 1 or 2, in which the sum of the thickness of the piezoelectric layer and the thickness of the dielectric layer is 0.23 times or less the repetition interval p, and the duty of the IDT electrode is 0.19 or more.

[0096] The elastic wave device according to aspect 6 of the present disclosure is, in aspect 1 or 2, such that the sum of the thickness of the piezoelectric layer and the thickness of the dielectric layer is 0.15 to 0.2 times the repetition interval p, and the duty of the IDT electrode is 0.19 to 0.35.

[0097] An elastic wave device according to aspect 7 of the present disclosure is any one of aspects 1 to 6, wherein at least a portion of the surfaces of the plurality of electrode fingers located opposite the first surface are covered by at least a portion of the dielectric layer.

[0098] An elastic wave device according to aspect 8 of the present disclosure is any one of aspects 1 to 6, wherein at least a portion of the surfaces of the plurality of electrode fingers opposite the first surface is exposed from the dielectric layer.

[0099] An elastic wave device according to aspect 9 of the present disclosure is, in any one of aspects 1 to 6, such that at least a portion of the dielectric layer is located on the opposite side of the first surface relative to at least a portion of the surfaces of the plurality of electrode fingers that are located on the opposite side of the first surface.

[0100] An elastic wave device according to aspect 10 of the present disclosure is one in which, in any one of aspects 1 to 6, at least a portion of the surface of the dielectric layer opposite the first surface is flush with at least a portion of the surfaces of the plurality of electrode fingers opposite the first surface.

[0101] An elastic wave device according to an eleventh aspect of the present disclosure is the elastic wave device of any one of the first to sixth aspects, wherein the first surface has a groove, and at least some of the plurality of electrode fingers are located inside the groove.

[0102] An elastic wave device according to aspect 12 of the present disclosure is such that, in any one of aspects 1 to 6, at least some of the surfaces of the plurality of electrode fingers located opposite the first surface are located opposite the first surface relative to at least some of the surfaces of the dielectric layer located opposite the first surface.

[0103] According to a thirteenth aspect of the present disclosure, in the elastic wave device of any one of the first to twelfth aspects, the dielectric layer is mainly composed of SiO ２ is.

[0104] An elastic wave device according to aspect 14 of the present disclosure is any one of aspects 1 to 13, in which the piezoelectric layer has a second surface located opposite the first surface, and the elastic wave device has an acoustic reflection film located on the second surface side and including a low acoustic impedance layer and a high acoustic impedance layer.

[0105] An elastic wave device according to a fifteenth aspect of the present disclosure is the elastic wave device of any one of the first to fourteenth aspects, wherein the first side surface and the second side surface are spaced apart from each other.

[0106] An elastic wave device according to aspect 16 of the present disclosure is any one of aspects 1 to 6, in which at least a portion of the plurality of electrode fingers contacts at least a portion of a surface of the dielectric layer opposite the first surface.

[0107] An elastic wave device according to aspect 17 of the present disclosure is any one of aspects 1 to 16, and includes a first resonator and a second resonator, wherein the resonant frequency corresponding to the second resonator is lower than the resonant frequency corresponding to the first resonator, and the portion of the dielectric layer corresponding to the second resonator is thicker than the portion of the dielectric layer corresponding to the first resonator.

[0108] A communication device according to an eighteenth aspect of the present disclosure includes the acoustic wave device of any one of the first to seventeenth aspects.

[0109] The invention according to the present disclosure has been described above based on the drawings and examples. However, the invention according to the present disclosure is not limited to the above-described embodiments. In other words, the invention according to the present disclosure can be modified in various ways within the scope of the present disclosure, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the invention according to the present disclosure. In other words, it should be noted that a person skilled in the art can easily make various modifications or corrections based on the present disclosure. It should also be noted that these modifications or corrections are included in the scope of the present disclosure.

[0110] REFERENCE SIGNS LIST 1 Resonator section 2 Piezoelectric layer 3 IDT electrode 4 Dielectric layer 5 First surface 6 First side surface 7 Electrode finger 8 Second side surface 9 Surface of multiple electrode fingers located opposite to the first surface 10 Surface of dielectric layer located opposite to the first surface 11 Second surface 12 Acoustic reflection film 13 Low acoustic impedance layer 14 High acoustic impedance layer 15 Groove 16 First resonator 17 Second resonator 18 Portion of dielectric layer corresponding to first resonator 19 Portion of dielectric layer corresponding to second resonator 101 Acoustic wave device 201 Communication device T2 Thickness of piezoelectric layer T4 Thickness of dielectric layer

Claims

1. An elastic wave device having a resonator portion and exciting at least one of plate waves and bulk waves, wherein the resonator portion comprises: a piezoelectric layer containing lithium niobate and having a first surface; an IDT electrode located on the first surface side, having a first side surface, and having a plurality of electrode fingers arranged at a repeating interval p; and a dielectric layer located on the first surface side, having a second side surface facing the first side surface, and having a positive frequency temperature coefficient; wherein the Euler angle of the piezoelectric layer is (0°, 30° or more and 42° or less, 0°), and a solution of equation (1) below: thickness of the piezoelectric layer / (thickness of the piezoelectric layer + thickness of the dielectric layer) ... (1) is 0.60 or more and 0.75 or less.

2. The acoustic wave device according to claim 1, wherein the Euler angles of the piezoelectric layer are (0°, 34° or more and 42° or less, 0°).

3. An elastic wave device according to claim 1 or 2, wherein the sum of the thickness of the piezoelectric layer and the thickness of the dielectric layer is 0.15 times or more and 0.2 times or less the repeat interval p, or 0.26 times or more and 0.39 times or less the repeat interval p.

4. The acoustic wave device according to claim 1, wherein the duty of the IDT electrode is 0.35 or less.

5. The elastic wave device according to claim 1 or 2, wherein the sum of the thicknesses of the piezoelectric layers and the dielectric layers is 0.23 times or less the repeat interval p, and the duty of the IDT electrodes is 0.19 or more.

6. The elastic wave device according to claim 1 or 2, wherein the sum of the thickness of the piezoelectric layer and the thickness of the dielectric layer is 0.15 to 0.2 times the repetition interval p, and the duty of the IDT electrode is 0.19 to 0.

35.

7. The elastic wave device according to claim 1, wherein at least a portion of the surfaces of the plurality of electrode fingers located opposite the first surface is covered by at least a portion of the dielectric layer.

8. The acoustic wave device according to claim 1, wherein at least a portion of the surfaces of the plurality of electrode fingers opposite the first surface is exposed from the dielectric layer.

9. An elastic wave device according to any one of claims 1 to 6, wherein at least a portion of the dielectric layer is located on the opposite side of the first surface with respect to at least a portion of the surfaces of the plurality of electrode fingers located on the opposite side of the first surface.

10. An elastic wave device according to any one of claims 1 to 6, wherein at least a portion of the surface of the dielectric layer opposite the first surface and at least a portion of the surfaces of the plurality of electrode fingers opposite the first surface are flush with each other.

11. The acoustic wave device according to claim 1, wherein the first surface has a groove, and at least some of the plurality of electrode fingers are located inside the groove.

12. An elastic wave device according to any one of claims 1 to 6, wherein at least a portion of the surfaces of the plurality of electrode fingers located opposite the first surface are located opposite the first surface relative to at least a portion of the surfaces of the dielectric layer located opposite the first surface.

13. The main component of the dielectric layer is SiO ２ The acoustic wave device according to claim 1 , wherein 14. An elastic wave device according to any one of claims 1 to 13, wherein the piezoelectric layer has a second surface located opposite the first surface, and the elastic wave device has an acoustic reflection film located on the second surface side and including a low acoustic impedance layer and a high acoustic impedance layer.

15. The acoustic wave device according to any one of claims 1 to 14, wherein the first side surface and the second side surface are spaced apart.

16. The elastic wave device according to any one of claims 1 to 6, wherein at least a portion of the plurality of electrode fingers contacts at least a portion of a surface of the dielectric layer opposite the first surface.

17. The elastic wave device according to any one of claims 1 to 16, comprising a first resonator and a second resonator, wherein a resonant frequency corresponding to the second resonator is lower than a resonant frequency corresponding to the first resonator, and a portion of the dielectric layer corresponding to the second resonator is thicker than a portion of the dielectric layer corresponding to the first resonator.

18. A communication device comprising the acoustic wave device according to any one of claims 1 to 17.

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