Elastic wave device

Abstract

The present application takes into account both inhibition of adhesion of a space portion and shortening of drying time. An elastic wave device includes a support member including a support substrate having a thickness in a first direction; a piezoelectric layer provided in the first direction of the support member; and a plurality of resonators each having a functional electrode provided in the first direction of the piezoelectric layer. The support member is provided with a plurality of space portions at positions overlapping at least a portion of each of the resonators when viewed in the first direction, the plurality of space portions including a first space portion and a second space portion having a larger area than the first space portion when viewed in the first direction, the piezoelectric layer is provided with a first through-hole communicating with the first space portion and a second through-hole communicating with the second space portion, and the first through-hole has a larger area than the second through-hole when viewed in the first direction.

Description

Technical Field

[0001] This disclosure relates to elastic wave devices. Background Technology

[0002] Patent document 1 describes an elastic wave device.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2012-257019 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] In the elastic wave device shown in Patent Document 1, through holes communicating with the spatial portions are sometimes provided in the piezoelectric layer as etching holes for setting spatial portions of different areas. In this case, the etching solution cannot be dried at a speed suitable for the size of the spatial portion, and adhesion may occur in large spatial portions, while drying becomes slow in small spatial portions.

[0008] This disclosure is intended to solve the above-mentioned problems, and its purpose is to balance the suppression of adhesion in the space and the reduction of drying time.

[0009] Technical solutions for solving the problem

[0010] An elastic wave device includes: a support member having a support substrate having a thickness in a first direction; a piezoelectric layer disposed in the first direction of the support member; and a plurality of resonators, each having a functional electrode disposed in the first direction of the piezoelectric layer. When viewed from above in the first direction, the support member has a plurality of spatial portions overlapping at least a portion of each of the resonators. The plurality of spatial portions include a first spatial portion and a second spatial portion having an area larger than the first spatial portion when viewed from above in the first direction. The piezoelectric layer has a first through-hole communicating with the first spatial portion and a second through-hole communicating with the second spatial portion. When viewed from above in the first direction, the area of ​​the first through-hole is larger than that of the second through-hole.

[0011] Invention Effects

[0012] According to this disclosure, it is possible to both suppress adhesion in the space and shorten the drying time. Attached Figure Description

[0013] Figure 1A This is a perspective view showing the elastic wave device of the first embodiment.

[0014] Figure 1BThis is a top view showing the electrode structure of the first embodiment.

[0015] Figure 2 yes Figure 1A A sectional view of the portion along line II-II.

[0016] Figure 3A This is a schematic cross-sectional view used to illustrate the Lamb wave propagating in the piezoelectric layer of the comparative example.

[0017] Figure 3B This is a schematic cross-sectional view used to illustrate the bulk wave of the thickness shear first-order mode propagating in the piezoelectric layer in the first embodiment.

[0018] Figure 4 This is a schematic cross-sectional view used to illustrate the amplitude direction of the bulk wave of the thickness shear first mode propagating in the piezoelectric layer of the first embodiment.

[0019] Figure 5 This is an explanatory diagram showing an example of the resonant characteristics of the elastic wave device according to the first embodiment.

[0020] Figure 6 This is an explanatory diagram showing the relationship between d / 2p and the relative bandwidth of the resonator when the center-to-center distance or the average center-to-center distance of adjacent electrodes is set as p and the average thickness of the piezoelectric layer is set as d in the elastic wave device of the first embodiment.

[0021] Figure 7 This is a top view showing an example of an elastic wave device in the first embodiment having a pair of electrodes.

[0022] Figure 8 This is a reference diagram showing an example of the resonant characteristics of the elastic wave device according to the first embodiment.

[0023] Figure 9 This is an explanatory diagram showing the relationship between the relative bandwidth and the phase rotation amount of the spurious impedance, which is normalized by 180 degrees, in the case of a first embodiment of the elastic wave device comprising a plurality of elastic wave resonators.

[0024] Figure 10 This is an explanatory graph showing the relationship between d / 2p, metallization ratio (MR), and relative bandwidth.

[0025] Figure 11 This is an illustrative diagram showing the mapping of the relative bandwidth to the Euler angles (0°, θ, ψ) of LiNbO3 with d / p as close to 0 as possible.

[0026] Figure 12 This is a partially cut-off perspective view used to illustrate the elastic wave device involved in the embodiments of this disclosure.

[0027] Figure 13 This is a cross-sectional view used to illustrate the elastic wave device involved in the embodiments of this disclosure.

[0028] Figure 14 This is a top view showing an example of the elastic wave device according to the first embodiment.

[0029] Figure 15 yes Figure 14 A cross-sectional view of the XV-XV line.

[0030] Figure 16 yes Figure 14 The circuit diagram of the elastic wave device according to the first embodiment is shown.

[0031] Figure 17 This is a top view showing a portion of a first variation of the elastic wave device according to the first embodiment.

[0032] Figure 18 This is a top view showing a portion of a second variation of the elastic wave device according to the first embodiment.

[0033] Figure 19 This is a cross-sectional view showing a third variation of the elastic wave device according to the first embodiment.

[0034] Figure 20 This is a cross-sectional view showing a fourth variation of the elastic wave device according to the first embodiment.

[0035] Figure 21 This is a cross-sectional view showing a fifth variation of the elastic wave device according to the first embodiment. Detailed Implementation

[0036] Hereinafter, embodiments of the present disclosure will be described in detail based on the accompanying drawings. However, the present disclosure is not limited to these embodiments. Furthermore, the embodiments described in this disclosure are illustrative, and partial substitutions or combinations of structures can be made between different embodiments. Following the embodiments and modifications, descriptions of matters common to the first embodiment are omitted, and only the differences are described. In particular, the same effects based on the same structure will not be mentioned repeatedly in each embodiment.

[0037] (First Embodiment)

[0038] Figure 1A This is a perspective view showing the elastic wave device of the first embodiment. Figure 1B This is a top view showing the electrode structure of the first embodiment.

[0039] The elastic wave device 1 of the first embodiment has a piezoelectric layer 2 comprising LiNbO3. The piezoelectric layer 2 may also comprise LiTaO3. In the first embodiment, the cutting angle of LiNbO3 and LiTaO3 is Z-cut. The cutting angle of LiNbO3 and LiTaO3 may also be rotational Y-cut or X-cut. Preferably, the propagation orientation is ±30° of Y propagation and X propagation.

[0040] The thickness of the piezoelectric layer 2 is not particularly limited, but in order to effectively excite the first-order mode of thickness shearing, it is preferably 50 nm or more and 1000 nm or less.

[0041] The piezoelectric layer 2 has a first main surface 2a and a second main surface 2b that are opposite to each other in the Z direction. Electrode fingers 3 and 4 are provided on the first main surface 2a.

[0042] Here, electrode finger 3 is an example of "first electrode finger," and electrode finger 4 is an example of "second electrode finger." Figure 1A as well as Figure 1B In this configuration, multiple electrode fingers 3 are multiple "first electrode fingers" connected to the first busbar electrode 5. Multiple electrode fingers 4 are multiple "second electrode fingers" connected to the second busbar electrode 6. The multiple electrode fingers 3 and multiple electrode fingers 4 are interleaved and interlocked with each other. Thus, an IDT (Interdigital Transducer) electrode is formed, comprising electrode fingers 3, electrode fingers 4, the first busbar electrode 5, and the second busbar electrode 6.

[0043] Electrode fingers 3 and 4 have a rectangular shape and a length direction. Electrode finger 3 and its adjacent electrode finger 4 are opposite each other in a direction orthogonal to this length direction. The length directions of electrode fingers 3 and 4, as well as the directions orthogonal to their length directions, intersect the thickness direction of the piezoelectric layer 2. Therefore, it can also be said that electrode finger 3 and its adjacent electrode finger 4 are opposite each other in a direction intersecting the thickness direction of the piezoelectric layer 2. In the following description, the thickness direction of the piezoelectric layer 2 is sometimes defined as the Z direction (or the first direction), the length directions of electrode fingers 3 and 4 as the Y direction (or the second direction), and the direction orthogonal to their length directions as the X direction (or the third direction).

[0044] Furthermore, the length directions of electrode fingers 3 and 4 can also be... Figure 1A as well as Figure 1B The directions shown are reversed, reversing the directions orthogonal to the length directions of electrode fingers 3 and 4. That is, in Figure 1A as well as Figure 1BAlternatively, electrode fingers 3 and 4 can extend in the direction in which the first busbar electrode 5 and the second busbar electrode 6 extend. In this case, the first busbar electrode 5 and the second busbar electrode 6... Figure 1A as well as Figure 1B The electrode fingers 3 and 4 extend in the same direction. Furthermore, multiple pairs of adjacent electrode fingers 3 connected to one potential and electrode fingers 4 connected to another potential are provided in a direction orthogonal to the length direction of the electrode fingers 3 and 4.

[0045] Here, the phrase "electrode fingers 3 and 4 are adjacent" does not mean that electrode fingers 3 and 4 are configured in direct contact, but rather that they are configured with a gap between them. Furthermore, when electrode fingers 3 and 4 are adjacent, no electrodes connected to the signal electrode or ground electrode, including other electrode fingers 3 and 4, are placed between electrode fingers 3 and 4. The number of pairs does not need to be an integer; it can be 1.5 pairs, 2.5 pairs, etc.

[0046] The center-to-center distance, or spacing, between electrode fingers 3 and 4 is preferably in the range of 1 μm or more and 10 μm or less. Furthermore, the center-to-center distance between electrode fingers 3 and 4 is defined as the distance connecting the center of the width dimension of electrode finger 3 in a direction orthogonal to the length direction of electrode finger 3 and the center of the width dimension of electrode finger 4 in a direction orthogonal to the length direction of electrode finger 4.

[0047] Furthermore, when there are multiple electrode fingers 3 and 4 (when there are 1.5 or more electrode groups when electrode fingers 3 and 4 are set as a pair of electrode groups), the center-to-center distance of electrode fingers 3 and 4 refers to the average value of the center-to-center distances of adjacent electrode fingers 3 and 4 in 1.5 or more pairs of electrode fingers 3 and 4.

[0048] Furthermore, the width of electrode fingers 3 and 4, i.e., their dimensions in the opposing directions, are preferably in the range of 150 nm or more and 1000 nm or less. Additionally, the center-to-center distance between electrode fingers 3 and 4 is defined as the distance connecting the center of the width dimension of electrode finger 3 in a direction orthogonal to the length direction of electrode finger 3, and the center of the width dimension of electrode finger 4 in a direction orthogonal to the length direction of electrode finger 4.

[0049] Furthermore, in the first embodiment, a Z-cut piezoelectric layer is used, so the direction orthogonal to the length direction of electrode fingers 3 and 4 becomes the direction orthogonal to the polarization direction of piezoelectric layer 2. This is not a limitation if a piezoelectric material with other cut angles is used as piezoelectric layer 2. Here, "orthogonal" is not limited to strictly orthogonal; it can also be approximately orthogonal (the angle between the direction orthogonal to the length direction of electrode fingers 3 and 4 and the polarization direction is, for example, 90° ± 10°).

[0050] On the second main surface 2b side of the piezoelectric layer 2, a support substrate 8 is stacked across the dielectric layer 7. The dielectric layer 7 and the support substrate 8 have a frame-like shape, such as... Figure 2 As shown, it has openings 7a and 8a. This forms a space (air gap) 9.

[0051] The space portion 9 is provided so as not to interfere with the vibration of the excitation region C of the piezoelectric layer 2. Therefore, the support substrate 8 is stacked on the second main surface 2b with the dielectric layer 7 in a position that does not overlap with the portion where at least one pair of electrode fingers 3 and electrode fingers 4 are provided. Alternatively, the dielectric layer 7 may not be provided. Therefore, the support substrate 8 can be stacked directly or indirectly on the second main surface 2b of the piezoelectric layer 2.

[0052] The dielectric layer 7 is formed of silicon oxide. However, in addition to silicon oxide, the dielectric layer 7 can also be formed of suitable insulating materials such as silicon nitride and bauxite.

[0053] The support substrate 8 is formed of Si. The orientation of the face on the piezoelectric layer 2 side of Si can be (100), (110), or (111). Preferably, it is Si with a high resistivity of 4kΩ or higher. However, the support substrate 8 can also be constructed using suitable insulating materials or semiconductor materials. For example, piezoelectric materials such as alumina, lithium tantalate, lithium niobate, and quartz, bauxite, magnesium oxide, sapphire, silicon nitride, aluminum nitride, silicon carbide, zirconium oxide, cordierite, mullite, block talc, and forsterite, as well as various ceramics such as diamond, glass, and semiconductors such as gallium nitride can be used as materials for the support substrate 8.

[0054] The aforementioned plurality of electrode fingers 3 and 4, as well as the first busbar electrode 5 and the second busbar electrode 6, comprise suitable metals or alloys such as Al or AlCu alloys. In the first embodiment, the electrode fingers 3 and 4, as well as the first busbar electrode 5 and the second busbar electrode 6, have a structure in which an Al film is laminated on a Ti film. Alternatively, a close-fitting layer other than a Ti film may also be used.

[0055] During driving, an AC voltage is applied between multiple electrode fingers 3 and multiple electrode fingers 4. More specifically, an AC voltage is applied between the first busbar electrode 5 and the second busbar electrode 6. As a result, the resonant characteristics of a bulk wave utilizing the thickness shear first-order mode excited in the piezoelectric layer 2 can be obtained.

[0056] Furthermore, in the elastic wave device 1, when the thickness of the piezoelectric layer 2 is set to d and the center-to-center distance between any two adjacent pairs of electrode fingers 3 and 4 is set to p, d / p is set to 0.5 or less. Therefore, a bulk wave with the aforementioned thickness shear first mode can be effectively excited, resulting in good resonance characteristics. More preferably, d / p is 0.24 or less, in which case even better resonance characteristics can be obtained.

[0057] Furthermore, in the case where at least one of the electrode fingers 3 and electrode fingers 4 exists in multiples, as in the first embodiment, that is, when the electrode fingers 3 and electrode fingers 4 are set as a pair of electrode groups, there are 1.5 or more pairs of electrode fingers 3 and electrode fingers 4, the center-to-center distance p of adjacent electrode fingers 3 and electrode fingers 4 becomes the average distance between the center-to-center distances of each adjacent electrode finger 3 and electrode finger 4.

[0058] In the elastic wave device 1 of the first embodiment, the above-described structure is provided, so even if the number of pairs of electrode fingers 3 and 4 is reduced in order to achieve miniaturization, a decrease in the Q value is not easily generated. This is because it is a resonator that does not require reflectors on both sides, resulting in low propagation loss. Furthermore, the reason why the above-described reflectors are not required is because a body wave with a thickness shear first mode is utilized.

[0059] Figure 3A This is a schematic cross-sectional view used to illustrate the Lamb wave propagating in the piezoelectric layer of the comparative example. Figure 3B This is a schematic cross-sectional view used to illustrate the bulk wave of the thickness shear first-order mode propagating in the piezoelectric layer in the first embodiment. Figure 4 This is a schematic cross-sectional view used to illustrate the amplitude direction of the bulk wave of the thickness shear first mode propagating in the piezoelectric layer of the first embodiment.

[0060] exist Figure 3A In this case, it is an elastic wave device as described in Patent Document 1, in which Lamb waves propagate in a piezoelectric layer. For example... Figure 3A As shown, the wave propagates in the piezoelectric layer 201 as indicated by the arrow. Here, the piezoelectric layer 201 has a first main surface 201a and a second main surface 201b, and the thickness direction connecting the first main surface 201a and the second main surface 201b is the Z direction. The X direction is the direction in which the electrode fingers 3 and 4 of the IDT electrodes are arranged. Figure 3AAs shown, if it is a Lamb wave, the wave propagates continuously in the X direction as shown. Because it is a plate wave, although the piezoelectric layer 201 vibrates as a whole, the wave propagates in the X direction. Therefore, by placing reflectors on both sides, a resonant characteristic is obtained. As a result, wave propagation loss occurs, and in the pursuit of miniaturization, that is, by reducing the logarithm of electrode fingers 3 and 4, the Q value decreases.

[0061] In contrast, such as Figure 3B As shown, in the elastic wave device of the first embodiment, the vibration displacement is in the thickness shear direction, so the wave propagates and resonates almost entirely in the Z direction, which is the direction connecting the first principal surface 2a and the second principal surface 2b of the piezoelectric layer 2. That is, the X-direction component of the wave is significantly smaller than the Z-direction component. Moreover, since the resonance characteristic can be obtained through the propagation of the wave in this Z-direction, a reflector is not required. Therefore, no propagation loss occurs during propagation in the reflector. Thus, even if the number of electrode pairs including electrode fingers 3 and electrode fingers 4 is reduced to promote miniaturization, a decrease in the Q value is not easily generated.

[0062] In addition, such as Figure 4 As shown, the amplitude direction of the bulk wave of the first-order thickness shear mode is in the excitation region C of the piezoelectric layer 2 (reference). Figure 1B The first region 251 contained in region C and the second region 252 contained in region C become opposite. Figure 4 The diagram schematically illustrates a body wave when a voltage higher than that of electrode finger 3 is applied between electrode finger 3 and electrode finger 4. The first region 251 is the region in excitation region C between the virtual plane VP1 and the first main surface 2a, wherein the virtual plane VP1 is orthogonal to the thickness direction of the piezoelectric layer 2 and divides the piezoelectric layer 2 into two parts. The second region 252 is the region in excitation region C between the virtual plane VP1 and the second main surface 2b.

[0063] In the elastic wave device 1, at least one pair of electrodes, including electrode fingers 3 and electrode fingers 4, is provided. However, since the wave is not propagated in the X direction, the number of electrode pairs including electrode fingers 3 and electrode fingers 4 does not necessarily have to be multiple. That is, it is sufficient to provide at least one pair of electrodes.

[0064] For example, electrode 3 is an electrode connected to the signal potential, and electrode 4 is an electrode connected to the ground potential. However, it is also possible that electrode 3 is connected to the ground potential, and electrode 4 is connected to the signal potential. In the first embodiment, at least one pair of electrodes is either connected to the signal potential or connected to the ground potential as described above, and no floating electrode is provided.

[0065] Figure 5 This is an explanatory diagram showing an example of the resonant characteristics of the elastic wave device according to the first embodiment. Additionally, [the following is also provided]... Figure 5 The design parameters of the elastic wave device 1 with the resonant characteristics shown are as follows.

[0066] Piezoelectric layer 2: LiNbO3 with Euler angles (0°, 0°, 90°)

[0067] Thickness of piezoelectric layer 2: 400nm

[0068] Excitation region C (reference) Figure 1B Length: 40μm

[0069] Number of electrode pairs including electrode fingers 3 and 4: 21 pairs

[0070] Center-to-center distance (split) between electrode finger 3 and electrode finger 4: 3 μm

[0071] Width of electrode finger 3 and electrode finger 4: 500nm

[0072] d / p: 0.133

[0073] Dielectric layer 7: Silicon oxide film with a thickness of 1 μm

[0074] Support substrate 8: Si

[0075] In addition, the so-called incentive region C (refer to) Figure 1B The region C is the overlapping area of ​​electrode fingers 3 and 4 when viewed in the X direction, which is orthogonal to the length directions of electrode fingers 3 and 4. The length of the excitation region C is its dimension along the length directions of electrode fingers 3 and 4. Here, the excitation region C is an example of an "intersection region".

[0076] In the first embodiment, the distance between the electrodes of the electrode pairs including electrode fingers 3 and electrode fingers 4 is set to be equal in all pairs. That is, the electrode fingers 3 and electrode fingers 4 are arranged at equal intervals.

[0077] according to Figure 5 It is clear that, despite the absence of a reflector, a good resonant characteristic with a relative bandwidth of 12.5% ​​was still achieved.

[0078] Furthermore, when the thickness of the piezoelectric layer 2 is set to d and the center-to-center distance between the electrodes of electrode finger 3 and electrode finger 4 is set to p, in the first embodiment, d / p is 0.5 or less, more preferably 0.24 or less. (Refer to...) Figure 6 This needs to be explained.

[0079] With obtained Figure 5 Similarly, by varying d / 2p, multiple elastic wave devices were obtained, just as shown in the example of the elastic wave device with resonant characteristics. Figure 6This is an explanatory diagram showing the relationship between d / 2p and the relative bandwidth of the resonator when the center-to-center distance or the average center-to-center distance of adjacent electrodes is set as p and the average thickness of the piezoelectric layer 2 is set as d in the elastic wave device of the first embodiment.

[0080] like Figure 6 As shown, if d / 2p exceeds 0.25, i.e., if d / p > 0.5, then even if d / p is adjusted, the relative bandwidth is less than 5%. In contrast, when d / 2p ≤ 0.25, i.e., when d / p ≤ 0.5, if d / p is varied within this range, the relative bandwidth can be increased to 5% or more, i.e., a resonator with a high coupling coefficient can be constructed. Furthermore, when d / 2p is 0.12 or less, i.e., when d / p is 0.24 or less, the relative bandwidth can be increased to 7% or more. In addition, if d / p is adjusted within this range, a resonator with an even wider relative bandwidth can be obtained, and a resonator with a higher coupling coefficient can be achieved. Therefore, it can be seen that by setting d / p to 0.5 or less, a resonator with a high coupling coefficient utilizing the aforementioned thickness shear first-order mode of the bulk wave can be constructed.

[0081] Alternatively, at least one pair of electrodes can be used. In the case of one pair of electrodes, p is defined as the distance between the centers of adjacent electrode fingers 3 and 4. Furthermore, in the case of 1.5 or more pairs of electrodes, p can simply be defined as the average distance between the centers of adjacent electrode fingers 3 and 4.

[0082] Furthermore, regarding the thickness d of the piezoelectric layer 2, even if the piezoelectric layer 2 has a thickness deviation, it is sufficient to use a value that has been averaged over its thickness.

[0083] Figure 7 This is a top view showing an example of an elastic wave device according to the first embodiment, in which a pair of electrodes are provided. In the elastic wave device 101, a pair of electrodes having electrode fingers 3 and electrode fingers 4 are provided on the first main surface 2a of the piezoelectric layer 2. Furthermore, Figure 7 K in this context refers to the cross width. As previously mentioned, in the elastic wave device of this disclosure, the number of electrode pairs can also be one. In this case, as long as the aforementioned d / p is 0.5 or less, it is possible to effectively excite a first-order thickness shear mode volume wave.

[0084] In the elastic wave device 1, preferably, among the plurality of electrode fingers 3 and 4, the metallization ratio MR of any adjacent electrode fingers 3 and 4 relative to the excitation region C preferably satisfies MR ≤ 1.75(d / p) + 0.075, where the excitation region C is the region where the aforementioned adjacent electrode fingers 3 and 4 overlap when viewed in opposite directions. In this case, stray emissions can be effectively reduced. (Refer to...) Figure 8as well as Figure 9 This needs to be explained.

[0085] Figure 8 This is a reference diagram showing an example of the resonant characteristics of the elastic wave device according to the first embodiment. Strays, as indicated by arrow B, appear between the resonant frequency and the anti-resonant frequency. Furthermore, d / p = 0.08, and the Euler angles of LiNbO3 are set to (0°, 0°, 90°). Additionally, the metallization ratio MR is set to 0.35.

[0086] Reference Figure 1B The metallization ratio (MR) is explained. Figure 1B In the electrode structure, considering only a pair of electrode fingers 3 and 4, it is assumed that only this pair of electrode fingers 3 and 4 are provided. In this case, the portion enclosed by the single-dotted line is called the excitation region C. This excitation region C refers to the area where electrode fingers 3 overlaps with electrode finger 4, the area where electrode finger 4 overlaps with electrode finger 3, and the area where electrode fingers 3 and 4 overlap when viewed in a direction orthogonal to the length direction of electrode fingers 3 and 4 (i.e., the opposing direction), as well as the area between electrode fingers 3 and 4. Furthermore, the area of ​​electrode fingers 3 and 4 within the excitation region C relative to the area of ​​the excitation region C is called the metallization ratio MR. That is, the metallization ratio MR is the ratio of the area of ​​the metallized portion to the area of ​​the excitation region C.

[0087] In addition, when multiple pairs of electrode fingers 3 and 4 are provided, it is sufficient to set the ratio of the total area of ​​the metallized portion contained in the entire excitation region C to the total area of ​​the excitation region C as MR.

[0088] Figure 9 This is an explanatory diagram showing the relationship between the relative bandwidth and the phase rotation amount of the stray impedance, which is normalized by 180 degrees, when a plurality of elastic wave resonators are configured in the elastic wave device of the first embodiment. Furthermore, various changes were made to the film thickness of the piezoelectric layer 2 and the dimensions of the electrode fingers 3 and 4, thereby adjusting the relative bandwidth. In addition, Figure 9 This is the result when using piezoelectric layer 2 with Z-cut LiNbO3, but the same tendency occurs even when using piezoelectric layer 2 with other cut angles.

[0089] exist Figure 9 In the region enclosed by ellipse J, the stray energy increases to 1.0. According to... Figure 9 It is clear that if the relative bandwidth exceeds 0.17, that is, if it exceeds 17%, then even if the parameters constituting the relative bandwidth are changed, large spurious signals with a spurious level greater than 1 will appear in the passband. That is, like... Figure 8As shown in the resonance characteristics, large strays appear within the band, as indicated by arrow B. Therefore, a relative bandwidth of 17% or less is preferred. In this case, strays can be reduced by adjusting the thickness of the piezoelectric layer 2, the dimensions of the electrode fingers 3 and 4, etc.

[0090] Figure 10 This is an explanatory diagram showing the relationship between d / 2p, metallization ratio (MR), and relative bandwidth. In the elastic wave device 1 of the first embodiment, various elastic wave devices 1 with different d / 2p and MR were constructed, and the relative bandwidth was measured. Figure 10 The portion shown by adding a shading line to the right of the dashed line D is the area with a relative bandwidth of 17% or less. The boundary between this shaded and unshaded area can be represented by MR = 3.5(d / 2p) + 0.075, that is, MR = 1.75(d / p) + 0.075. Therefore, it is preferable that MR ≤ 1.75(d / p) + 0.075. In this case, it is easy to achieve a relative bandwidth of 17% or less. More preferably... Figure 10 The region to the right of the dashed line D1 in the diagram is MR = 3.5(d / 2p) + 0.05. That is, if MR ≤ 1.75(d / p) + 0.05, the relative bandwidth can be reliably kept below 17%.

[0091] Figure 11 This is an illustrative diagram showing the mapping of the relative bandwidth to the Euler angles (0°, θ, ψ) of LiNbO3 with d / p as close to 0 as possible. Figure 11 The portion shown by the shading is the area where a relative bandwidth of at least 5% can be obtained. If the range of the region is approximated, it becomes the range represented by the following equations (1), (2) and (3).

[0092] (0°±10°, 0°~20°, any ψ) …Equation (1)

[0093] (0°±10°, 20°~80°, 0°~60°(1-(θ-50) 2 / 900) 1 / 2 () or (0°±10°, 20°~80°, [180°-60°(1-(θ-50))) 2 / 900) 1 / 2 [~180°) …Equation (2)

[0094] (0°±10°,[180°-30°(1-(ψ-90) 2 / 8100) 1 / 2 ~180°, any ψ)

[0095] …Formula (3)

[0096] Therefore, it is preferable to have a sufficiently wide relative bandwidth within the range of Euler angles in equations (1), (2), or (3) above.

[0097] Figure 12 This is a partially cut-off perspective view used to illustrate the elastic wave device according to embodiments of this disclosure. Figure 12 In the diagram, the outer periphery of the spatial portion 9 is shown by a dashed line. The elastic wave device of this disclosure can also be an elastic wave device utilizing plate waves. In this case, such as... Figure 12 As shown, the elastic wave device 301 includes reflectors 310 and 311. Reflectors 310 and 311 are disposed on both sides of the electrode fingers 3 and 4 of the piezoelectric layer 2 in the direction of elastic wave propagation. In the elastic wave device 301, by applying an alternating voltage to the electrode fingers 3 and 4 on the spatial portion 9, a Lamb wave, which is a plate wave, is excited. Since reflectors 310 and 311 are disposed on both sides, resonance characteristics based on the Lamb wave as a plate wave can be obtained.

[0098] As explained above, in elastic wave devices 1 and 101, a first-order mode of thickness shearing is utilized for bulk waves. Furthermore, in elastic wave devices 1 and 101, the first electrode finger 3 and the second electrode finger 4 are adjacent electrodes. When the thickness of the piezoelectric layer 2 is set to d and the center-to-center distance between the first electrode finger 3 and the second electrode finger 4 is set to p, d / p is set to 0.5 or less. Therefore, even when miniaturizing the elastic wave device, the Q value can be improved.

[0099] In the elastic wave devices 1 and 101, the piezoelectric layer 2 is formed of lithium niobate or lithium tantalate. On the first main surface 2a or the second main surface 2b of the piezoelectric layer 2, there are first electrode fingers 3 and second electrode fingers 4 facing each other in a direction intersecting the thickness direction of the piezoelectric layer 2, and preferably the first electrode fingers 3 and the second electrode fingers 4 are covered with a protective film.

[0100] Figure 13 This is a cross-sectional view illustrating the elastic wave device according to embodiments of this disclosure. The elastic wave device of this disclosure may also be as follows: Figure 13 The device shown utilizes bulk waves, specifically a BAW (Bulk Acoustic Wave) element. In this case, the elastic wave device 401 has functional electrodes 410 and 411. The functional electrodes 410 and 411 are electrodes disposed on opposite sides relative to the thickness direction of the piezoelectric layer 2. Figure 13 In the example, the support substrate 8 has a space 9 on the piezoelectric layer 2 side, and the functional electrode 411 is disposed in the space 9.

[0101] exist Figure 13In this example, a through-hole 11 is provided in the piezoelectric layer 2. The through-hole 11 is a hole that penetrates the piezoelectric layer 2 in the Z direction. The through-hole 11 communicates with the space portion 9. By providing the through-hole 11 in the piezoelectric layer 2, after the piezoelectric layer 2 is bonded to the support substrate 8, the etching solution flows in through the through-hole 11, thereby enabling the etching of the sacrificial layer that is pre-formed in the space portion 9 before bonding.

[0102] Figure 14 This is a top view showing an example of the elastic wave device according to the first embodiment. Figure 15 yes Figure 14 A cross-sectional view of the XV-XV line. (See example...) Figure 14 as well as Figure 15 As shown, the elastic wave device 500 according to the first embodiment is an elastic wave device provided with a plurality of resonators 501A to 501G. The elastic wave device 500 includes a support member 520, a piezoelectric layer 502, wiring electrodes 512A to 512C, an input terminal 513, an output terminal 514, and grounding devices 515A and 515B.

[0103] A piezoelectric layer 502 is disposed on the support member 520. The piezoelectric layer 502 has a first main surface 502a and a second main surface 502b. In this embodiment, the first main surface 502a is the surface on which resonators 501A to 501F and wiring electrodes 512A to 512C are disposed. On the other hand, the second main surface 502b is the surface on which the support member 520 is disposed. The material of the piezoelectric layer 502 sometimes contains lithium niobate (LiNbO3) or lithium tantalate (LiTaO3) and impurities.

[0104] like Figure 15 As shown, the support member 520 includes a support substrate 521 and a dielectric layer 522. The material of the support substrate 521 is, for example, silicon. The dielectric layer 522 is disposed on the piezoelectric layer 502 side relative to the support substrate 521. The material of the dielectric layer 522 is, for example, silicon oxide.

[0105] Resonators 501A to 501F have functional electrodes and a laminate that overlaps with the functional electrodes when viewed from above in the Z direction. Here, the functional electrode refers to an IDT electrode having a first electrode finger, a second electrode finger, a first busbar electrode, and a second busbar electrode. Furthermore, the laminate includes a portion of the piezoelectric layer 502 and a portion of the support member 520. Hereinafter, resonators 501A and 501C will sometimes be described as first resonators, and resonators 501B and 501D as second resonators.

[0106] In this embodiment, resonators 501A and 501B are provided with electrode fingers 503A and 503B as the first and second electrode fingers of the functional electrodes. That is, electrode fingers 503A and 503B can be considered as the first and second electrode fingers of resonators 501A and 501B, respectively. Electrode fingers 503A and 503B have a length direction in the Y direction. Their ends relative to the Y direction are connected to the first busbar electrode and the second busbar electrode.

[0107] The electrode area of ​​resonator 501A is larger than that of resonator 501B, while the electrode area of ​​resonator 501C is relatively smaller than that of resonator 501D. Here, the electrode area of ​​resonators 501A to 501D refers to the area of ​​the overlapping regions C1 to C4 when the multiple first and second electrode fingers of the resonator are viewed in the direction of their arrangement. That is, the area of ​​the overlapping region C1 of resonator 501A is larger than that of the overlapping region C2 of resonator 501B, and the area of ​​the overlapping region C3 of resonator 501C is smaller than that of the overlapping region C4 of resonator 501D.

[0108] Wiring electrodes 512A to 512C are wirings that electrically connect resonators 501A to 501F. Wiring electrodes 512A to 512D are disposed in piezoelectric layer 502. Wiring electrodes 512A to 512D are electrically connected to the busbar electrodes of resonators 501A to 501F.

[0109] Figure 16 yes Figure 14 The circuit diagram of the elastic wave device according to the first embodiment is shown. Figure 16 As shown, the elastic wave device 500 is a so-called trapezoidal filter, which includes a series arm resonator inserted in series into the signal path from input terminal 513 to output terminal 514 and a parallel arm resonator inserted into the path between the signal path and ground. Figure 16 In this configuration, the series-arm resonators are resonators 501A, 501E, and 501C. One terminal of each of the resonators 501A, 501E, and 501C, which are series-arm resonators, is electrically connected to the input terminal 513, and the other terminal is electrically connected to the output terminal 514. Here, resonators 501A, 501E, and 501C are connected in series. On the other hand, in... Figure 16In this configuration, the parallel arm resonators are resonators 501B, 501F, 501D, and 501G. One terminal of resonator 501B is electrically connected to input terminal 513 via wiring electrode 512A, and the other terminal is electrically connected to ground 515A. One terminal of resonator 501F is electrically connected to wiring electrode 512B, which connects resonators 501A and 501E, and the other terminal is electrically connected to ground 515A. One terminal of resonator 501D is electrically connected to wiring electrode 512C, which connects resonators 501E and 501C, and the other terminal is electrically connected to ground 515B. One terminal of resonator 501G is electrically connected to output terminal 514 via wiring electrode 512D, and the other terminal is electrically connected to ground 515B.

[0110] Furthermore, in the elastic wave device 500 according to this embodiment, the first resonators 501A and 501C are not limited to series-arm resonators, and the second resonators 501B and 501D are not limited to parallel-arm resonators. For example, the first resonators 501A and 501C may be parallel-arm resonators, and the second resonators 501B and 501D may be series-arm resonators. Additionally, the elastic wave device 500 may also include a transmitting resonator and a receiving resonator. In this case, the first resonators 501A and 501C may be transmitting resonators, and the second resonators 501B and 501D may be receiving resonators. Alternatively, the first resonators 501A and 501C may be receiving resonators, and the second resonators 501B and 501D may be transmitting resonators.

[0111] Here, in a portion of the stack of resonators 501A to 501D, the support member 520 has a space portion 509A to 509D and a lead-out portion 510A to 510D on the piezoelectric layer 502 side. For example, in a portion of the stack of resonators 501A, the support member 520 has a space portion 509A and a lead-out portion 510A on the piezoelectric layer 502 side.

[0112] Space portions 509A to 509D are cavities provided on the piezoelectric layer 502 side of the support member 520. Space portions 509A to 509D are positioned where, when viewed from above in the Z direction, at least a portion overlaps with the functional electrodes of each resonator 501A to 501D. That is, each of the resonators 501A to 501D has a space portion 509A to 509D provided on the support member 520 of the laminate. Here, space portions 509A and 509C are examples of a "first space portion," and space portions 509B and 509D are examples of a "second space portion."

[0113] The area of ​​the space portion 509A viewed from above in the Z direction is smaller than the area of ​​the space portion 509B viewed from above in the Z direction. Figure 15In the example, the length Cw1 of the space portion 509A relative to the X direction becomes smaller than the length Cw2 of the space portion 509B relative to the X direction. As a result, the resonator 501A, which has an electrode area larger than that of the resonator 501B, has a space portion 509A with a smaller area than that of the space portion 509B, thus improving heat dissipation.

[0114] exist Figure 14 In the example, the area of ​​the space portion 509C viewed from above in the Z direction is smaller than the area of ​​the space portion 509D viewed from above in the Z direction. As a result, the resonator 501D, whose electrode area is larger than that of the resonator 501C, has a space portion 509D with an area larger than that of the space portion 509C, thus making it easier to ensure the excitation space.

[0115] Furthermore, the depths, i.e., the lengths in the Z-direction, of spatial sections 509A and 509B, or spatial sections 509C and 509D, can also be different. For example, the depth of the second spatial sections 509B and 509D, which have a larger area when viewed from above in the Z-direction, can be greater than the depth of the first spatial sections 509A and 509C, which have a smaller area when viewed from above in the Z-direction.

[0116] Lead-out portions 510A to 510D are voids provided on the piezoelectric layer 502 side of the support member 520. Lead-out portions 510A to 510D are positioned where they do not overlap with spatial portions 509A to 509D when viewed from above in the Z direction. Lead-out portions 510A to 510D are connected to spatial portions 509A to 509D respectively. Figure 14 In the example, the lead-out portions 510A to 510D are respectively configured to communicate with both sides of the space portions 509A to 509D in the X direction. Hereinafter, the lead-out portions 510A and 510C will sometimes be described as the first lead-out portions and the lead-out portions 510B and 510D as the second lead-out portions.

[0117] Through holes 511A to 511D are provided in the piezoelectric layer 502, extending in the Z direction. These through holes 511A to 511D are configured to overlap with the lead-out portions 510A to 510D when viewed from above in the Z direction. That is, the through holes 511A to 511D communicate with the lead-out portions 510A to 510D in the Z direction. Here, through holes 511A and 511C are examples of "first through holes," and through holes 511B and 511D are examples of "second through holes."

[0118] The areas of the first through holes 511A and 511C are larger than the areas of the second through holes 511B and 511D. Here, the area of ​​a through hole refers to the total area occupied by the opening of the through holes in the piezoelectric layer 502 when viewed from above in the Z direction. For example, in Figure 14In the example, two through-holes 511A are provided in the piezoelectric layer 502. Therefore, the area of ​​the so-called through-hole 511A is the sum of the areas occupied by the openings of the two through-holes when viewed from above in the Z direction. Figure 15 In the example shown, the width Ew1 of the first through hole 511A relative to the X direction becomes larger than the width Ew2 of the second through hole 511B. Here, the width of a through hole refers to the length of the opening of a through hole relative to the X direction.

[0119] In the manufacturing process of the elastic wave device 500, the second spatial portions 509B and 509D, due to their large area, are prone to adhesion during the drying of the liquid within the spatial portions during etching. This adhesion occurs when the piezoelectric layer 502 flexes due to surface tension, causing it to adhere to the inner wall of the spatial portion. In this embodiment, the second spatial portions 509B and 509D are connected to the smaller second through holes 511B and 511D. This allows for slower evaporation of the liquid within the second spatial portions 509B and 509D through the second through holes 511B and 511D, enabling the second spatial portions 509B and 509D to dry gradually. Therefore, adhesion can be suppressed.

[0120] On the other hand, in the manufacturing process of the elastic wave device 500, the first spatial portions 509A and 509C have small areas, so when the liquid inside the spatial portions is dried during etching, adhesion is less likely to occur. In this embodiment, the first spatial portions 509A and 509C are connected to the first through holes 511A and 511C, which have large areas. This facilitates the evaporation of liquid inside the first spatial portions 509A and 509C through the first through holes 511A and 511C, enabling rapid drying of the first spatial portions 509A and 509C. Therefore, manufacturing efficiency can be improved.

[0121] The elastic wave device involved in this embodiment is not limited to... Figure 14 The elastic wave device 500 shown is described below. Hereinafter, variations of the elastic wave device according to this embodiment will be described with reference to the accompanying drawings. Furthermore, the same reference numerals will be used for the same structures, and descriptions will be omitted.

[0122] Figure 17 This is a top view showing a portion of a first variation of the elastic wave device according to the first embodiment. Figure 18 This is a top view showing a portion of a second variation of the elastic wave device according to the first embodiment. (As shown) Figure 17 as well as Figure 18As shown, the first through hole 511A and the second through hole 511B can also have openings of the same area when viewed from above in the Z direction, and the widths Ew1 and Ew2 of the first through hole and the second through hole can also be equal. In this case, the first through hole 511A is provided with more openings than the second through hole 511B.

[0123] In the elastic wave device 500A according to the first modified example, three first through holes 511AA are provided, communicating with the first space portion 509A, and two second through holes 511BA are provided, communicating with the second space portion 509B. Here, two first through holes 511AA are provided on one side of the first space portion 509A with respect to the X direction. As a result, the area of ​​the first through holes 511AA becomes larger than the area of ​​the second through holes 511BA, thus suppressing the adhesion of the second space portion 509B and shortening the drying time of the first space portion 509A during the manufacturing of the elastic wave device 500A.

[0124] In the elastic wave device 500B according to the second modification, two first through holes 511AB are provided, communicating with the first spatial portion 509A, and one second through hole 511BB is provided, communicating with the second spatial portion 509B. Here, the second through hole 511BB is provided only on one side of the second spatial portion 509B relative to the X direction. As a result, the area of ​​the first through hole 511AB becomes larger than the area of ​​the second through hole 511BB. Therefore, in the manufacturing of the elastic wave device 500B, adhesion of the second spatial portion 509B can be suppressed, and the drying time of the first spatial portion 509A can be shortened.

[0125] Figure 19 This is a cross-sectional view showing a third variation of the elastic wave device according to the first embodiment. Figure 20 This is a cross-sectional view showing a fourth variation of the elastic wave device according to the first embodiment. Figure 21 This is a cross-sectional view showing a fifth variation of the elastic wave device according to the first embodiment. Here, Figures 19-21 The elastic wave device involved in each variation example and Figure 15 The corresponding sectional view. For example... Figures 19-21 As shown, the structure of the support member 520 is not limited to... Figure 15 The structure shown.

[0126] In the elastic wave device 500C involved in the third modification example, such as Figure 19As shown, the first spatial portion 509AC, the second spatial portion 509BC, the first lead-out portion 510AC, and the second lead-out portion 510BC are disposed on the piezoelectric layer 502 side of the dielectric layer 522C with respect to the Z direction. In this case, during the manufacture of the elastic wave device 500C, the adhesion of the second spatial portion 509BC can be suppressed, and the drying time of the first spatial portion 509AC can be shortened.

[0127] In the elastic wave device 500D involved in the fourth modification example, such as Figure 20 As shown, the first spatial portion 509AD and the second spatial portion 509BD are disposed on the piezoelectric layer 502 side of the support substrate 521D with respect to the Z direction. Furthermore, the first lead-out portion 510AD and the second lead-out portion 510BD are disposed on the support member 520D, allowing the dielectric layer 522D to penetrate in the Z direction. In this case, during the manufacture of the elastic wave device 500D, adhesion of the second spatial portion 509BD can be suppressed, and the drying time of the first spatial portion 509AD can be shortened.

[0128] In the elastic wave device 500E involved in the fifth modification example, such as Figure 21 As shown, the support member serves only as the support substrate 521E. In this case, the first spatial portion 509AE, the second spatial portion 509BE, the first lead-out portion 510AE, and the second lead-out portion 510BE are disposed on the piezoelectric layer 502 side of the support substrate 521E with respect to the Z direction. In this case, during the manufacture of the elastic wave device 500E, adhesion of the second spatial portion 509BE can be suppressed, and the drying time of the first spatial portion 509AE can be shortened.

[0129] As described above, the elastic wave device 500 according to the first embodiment includes: a support member 520 having a support substrate 521 having a thickness in a first direction; a piezoelectric layer 502 disposed in the first direction of the support member 520; and a plurality of resonators 501A to 501G, each having a functional electrode disposed in the first direction of the piezoelectric layer 502. When viewed from above in the first direction, the support member 520 has a plurality of spatial portions 509A to 509D at positions overlapping at least a portion of each resonator. ~509D includes first spatial portions 509A and 509C and second spatial portions 509B and 509D with an area larger than that of the first spatial portions 509A and 509C when viewed from above in the first direction. A first through hole 511A and 511C communicating with the first spatial portions 509A and 509C and a second through hole 511B and 511D communicating with the second spatial portions 509B and 509D are provided in the piezoelectric layer 502. When viewed from above in the first direction, the area of ​​the first through hole 511A and 511C is larger than that of the second through hole 511B and 511D.

[0130] Therefore, since the large-area second spaces 509B and 509D are connected to the small-area second through holes 511B and 511D, the second spaces 509B and 509D can be slowly dried during the manufacture of the elastic wave device 500, preventing adhesion. On the other hand, the small-area first spaces 509A and 509C are connected to the large-area first through holes 511A and 511C, so the first spaces 509A and 509C can be quickly dried during the manufacture of the elastic wave device 500, shortening the drying time. Thus, it is possible to both suppress adhesion in the spaces and shorten the drying time.

[0131] Furthermore, when viewed from above in the first direction, the area of ​​the resonator 501B overlapping with the second space portion 509B can be larger than the area of ​​the resonator 501A overlapping with the first space portion 509A. In this case, the resonator 501A has a first space portion 509A with a smaller area than the second space portion 509B, thus improving the heat dissipation of the resonator 501A.

[0132] Furthermore, when viewed from above in the first direction, the area of ​​the resonator 501C overlapping with the first spatial portion 509C can be larger than the area of ​​the resonator 501D overlapping with the second spatial portion 509D. In this case, the resonator 501D has a second spatial portion 509D with an area larger than the first spatial portion 509C, thus making it easier for the resonator 501D to ensure excitation space.

[0133] Furthermore, when viewed from above in the first direction, the resonators 501A and 501C overlapping with the first spatial portions 509A and 509C, and the resonators 501B and 501D overlapping with the second spatial portions 509B and 509D, can be either series-arm resonators or parallel-arm resonators. In this case, it is also possible to simultaneously suppress adhesion to the spatial portions and shorten the drying time.

[0134] Furthermore, when viewed from above in the first direction, the resonators 501A and 501C overlapping with the first spatial portions 509A and 509C, and the resonators 501B and 501D overlapping with the second spatial portions 509B and 509D, can be either receiving resonators or transmitting resonators. In this case, it is also possible to simultaneously suppress adhesion of the spatial portions and shorten the drying time.

[0135] As a preferred embodiment, in the support member 520, an outlet 510A communicating with at least one of the plurality of spatial portions 509A and 509B is provided at a position that does not overlap with at least one spatial portion 509A when viewed from above in the first direction. A through hole 511A is provided in the piezoelectric layer 502 to penetrate the piezoelectric layer 502 at a position where it overlaps with the outlet 510A when viewed from above in the first direction. In this case, both suppression of adhesion to the spatial portions and reduction of drying time can be achieved.

[0136] As a preferred embodiment, the support member 520 includes a dielectric layer 522, and at least one space portion 509A to 509D is provided in the dielectric layer 522. Thereby, a surface acoustic wave device having good resonance characteristics can be provided.

[0137] As a preferred embodiment, the functional electrode has: one or more first electrode fingers extending in a second direction intersecting the first direction; and one or more second electrode fingers opposed to any one of the one or more first electrode fingers in a third direction orthogonal to the second direction and extending in the second direction. Thereby, a surface acoustic wave device having good resonance characteristics can be provided.

[0138] As a preferred embodiment, when the center-to-center distance between adjacent first electrode fingers 3 and second electrode fingers 4 among the plurality of first electrode fingers 3 and the plurality of second electrode fingers 4 is p, the thickness of the piezoelectric layer 2 is 2p or less. Thereby, the surface acoustic wave device 1 can be miniaturized and the Q value can be increased.

[0139] As a more preferred embodiment, the piezoelectric layer 2 contains lithium niobate or lithium tantalate. Thereby, a surface acoustic wave device having good resonance characteristics can be provided.

[0140] As a further preferred embodiment, the Euler angles of the lithium niobate or lithium tantalate constituting the piezoelectric layer 2 are within the range of the following formula (1), formula (2), or formula (3). In this case, the relative bandwidth can be made sufficiently wide.

[0141] (0° ± 10°, 0° to 20°, any ψ) … Formula (1)

[0142] (0° ± 10°, 20° to 80°, 0° to 60°(1 - (θ - 50) 2 / 900) 1 / 2 ) or (0° ± 10°, 20° to 80°, [180° - 60°(1 - (θ - 50) 2 / 900) 1 / 2 ) … Formula (2)

[0143] (0° ± 10°, [180° - 30°(1 - (ψ - 90) 2 / 8100) 1 / 2 ) to 180°, any ψ)

[0144] … Formula (3)

[0145] As a preferred embodiment, the surface acoustic wave device is configured to be able to utilize a bulk wave in a thickness-shear mode. Thereby, the coupling coefficient is increased, and a surface acoustic wave device having good resonance characteristics can be provided.

[0146] Preferably, when the thickness of the piezoelectric layer 2 is set to d and the center-to-center distance between adjacent first electrode fingers 3 and second electrode fingers 4 is set to p, d / p is 0.5 or less. This allows for miniaturization of the elastic wave device 1 and improves the Q value.

[0147] As a further preferred embodiment, d / p is 0.24 or less. This allows for miniaturization of the elastic wave device 1 and improves the Q value.

[0148] As a preferred embodiment, the region where adjacent electrode fingers 3 and 4 overlap in the opposite direction is the excitation region C. When the metallization ratio of the multiple electrode fingers 3 and 4 relative to the excitation region C is set as MR, MR ≤ 1.75(d / p) + 0.075 is satisfied. In this case, the relative bandwidth can be reliably kept below 17%.

[0149] As a preferred embodiment, the device is configured to utilize plate waves. This provides an elastic wave device with excellent resonance characteristics.

[0150] Furthermore, the above-described embodiments are intended to facilitate understanding of this disclosure and are not intended to limit its interpretation. This disclosure can be modified / improved without departing from its spirit, and it also includes equivalents.

[0151] Explanation of reference numerals in the attached figures

[0152] 1, 101, 301, 401: Elastic wave devices;

[0153] 2: Piezoelectric layer;

[0154] 2a: First main face;

[0155] 2b: Second main face;

[0156] 3: Electrode finger (first electrode finger);

[0157] 4: Electrode finger (second electrode finger);

[0158] 5: Busbar electrode (first busbar electrode);

[0159] 6: Busbar electrode (second busbar electrode);

[0160] 7: Dielectric layer;

[0161] 8: Support base plate;

[0162] 7a, 8a: Openings;

[0163] 9: Space Department;

[0164] 11: Through hole;

[0165] 201: Piezoelectric layer

[0166] 201a: 1st main surface;

[0167] 201b: Second main face;

[0168] 251: Region 1;

[0169] 252: Region 2;

[0170] 310, 311: Reflectors;

[0171] 410, 411: Functional electrodes;

[0172] 500, 500A~500E: Elastic wave device;

[0173] 501A, 501C: Resonators (first resonator);

[0174] 501B, 501D: Resonators (second resonator);

[0175] 501E~501G: Resonators;

[0176] 502: Piezoelectric layer;

[0177] 502a: 1st main surface;

[0178] 502b: 2nd main surface;

[0179] 503A, 503B: Electrode indicators;

[0180] 509A, 509C, 509AC~509AE: Space section (first space section);

[0181] 509B, 509D, 509BC~509BE: Space Section (Second Space Section);

[0182] 510A, 510C, 510AA~510AE: Lead-out section (first lead-out section);

[0183] 510B, 510D, 510BA~510BE: Lead-out section (second lead-out section);

[0184] 511A, 511C, 511AA, 511AB: Through holes (first through hole);

[0185] 511B, 511D, 511BA, 511BB: Through holes (second through hole);

[0186] 512A~512D: Wiring electrodes;

[0187] 513: Input terminal;

[0188] 514: Output terminal;

[0189] 515A, 515B: Grounding;

[0190] 520, 520C, 520D: Supporting components;

[0191] 521, 521C~521E: Support substrate;

[0192] 522, 522C, 522D: Dielectric layer;

[0193] C: Incentive region;

[0194] Cw1, Cw2: Length;

[0195] Ew1, Ew2: Width;

[0196] VP1: Virtual plane.

Claims

1. An elastic wave device, comprising: The support member has a support base plate having a thickness in a first direction; A piezoelectric layer is disposed in the first direction of the support member; and Multiple resonators, each having a functional electrode disposed in the first direction of the piezoelectric layer, The support member has multiple spatial portions located at positions that overlap with at least a portion of each of the resonators when viewed from above in the first direction. The plurality of spatial portions includes a first spatial portion and a second spatial portion having an area larger than the first spatial portion when viewed from above in the first direction. The piezoelectric layer is provided with a first through hole communicating with the first spatial portion and a second through hole communicating with the second spatial portion. When viewed from above in the first direction, the area of ​​the first through hole is larger than that of the second through hole.

2. The elastic wave device according to claim 1, wherein, When viewed from above in the first direction, the area of ​​the resonator overlapping with the second spatial portion is larger than the area of ​​the resonator overlapping with the first spatial portion.

3. The elastic wave device according to claim 1, wherein, When viewed from above in the first direction, the area of ​​the resonator overlapping with the first spatial portion is larger than the area of ​​the resonator overlapping with the second spatial portion.

4. The elastic wave device according to any one of claims 1 to 3, wherein, When viewed from above in the first direction, the resonator overlapping the first spatial portion and the resonator overlapping the second spatial portion are either series-arm resonators or parallel-arm resonators.

5. The elastic wave device according to any one of claims 1 to 3, wherein, When viewed from above in the first direction, the resonator overlapping the first spatial portion and the resonator overlapping the second spatial portion are either a receiving resonator or a transmitting resonator.

6. The elastic wave device according to any one of claims 1 to 3, wherein, In the support member, the lead-out portion communicating with at least one of the plurality of spatial portions is positioned at a location that does not overlap with the at least one spatial portion when viewed from above in the first direction. The piezoelectric layer is provided with a through hole that extends through the piezoelectric layer at a position that overlaps with the lead-out portion when viewed from above in the first direction.

7. The elastic wave device according to any one of claims 1 to 3, wherein, The support member has a dielectric layer. The dielectric layer is provided with at least one of the aforementioned spatial portions.

8. The elastic wave device according to any one of claims 1 to 3, wherein, The functional electrode has: one or more first electrode fingers extending in a second direction intersecting the first direction; and one or more second electrode fingers opposing any one of the one or more first electrode fingers in a third direction orthogonal to the second direction, and extending in the second direction.

9. The elastic wave device according to claim 8, wherein, When the center-to-center distance between adjacent first and second electrode fingers in the one or more first electrode fingers and the one or more second electrode fingers is set as p, the thickness of the piezoelectric layer is 2p or less.

10. The elastic wave device according to claim 8, wherein, The piezoelectric layer contains lithium niobate or lithium tantalate.

11. The elastic wave device according to claim 10, wherein, The Euler angles (φ, θ, ψ) of the lithium niobate or lithium tantalate are within the range of the following equations (1), (2), or (3). (0°±10°, 0°~20°, any ψ) … Equation (1) (0°±10°, 20°~80°, 0°~60° (1-(θ-50) 2 / 900) 1 / 2 ) or (0°±10°, 20°~80°, [180°-60° (1-(θ-50)) 2 / 900) 1 / 2 ~180°) …Equation (2) (0°±10°, [180°-30° (1-(ψ-90) 2 / 8100) 1 / 2 ~180°, any ψ) …Formula (3).

12. The elastic wave device according to claim 8, wherein, The elastic wave device is configured to utilize a body wave with a thickness shear mode.

13. The elastic wave device according to claim 12, wherein, When the thickness of the piezoelectric layer is set to d and the center-to-center distance between adjacent first and second electrode fingers among the more than one first electrode finger and the more than one second electrode finger is set to p, d / p≤0.

5.

14. The elastic wave device according to claim 13, wherein, d / p is below 0.

24.

15. The elastic wave device according to any one of claims 1 to 3, wherein, The functional electrode has: one or more first electrode fingers extending in a second direction intersecting the first direction; and one or more second electrode fingers opposing any one of the one or more first electrode fingers in a third direction orthogonal to the second direction, and extending in the second direction. The area where adjacent first and second electrode fingers overlap when viewed in opposite directions is the excitation region. When the metallization ratio of the more than one first electrode finger and the more than one second electrode finger relative to the excitation region is set as MR, the thickness of the piezoelectric layer is set as d, and the center-to-center distance between adjacent first and second electrode fingers among the more than one first electrode finger and the more than one second electrode finger is set as p, MR ≤ 1.75(d / p) + 0.075 is satisfied.

16. The elastic wave device according to any one of claims 1 to 3, wherein, The elastic wave device is configured to utilize plate waves.

17. The elastic wave device according to any one of claims 1 to 3, wherein, The functional electrode has an upper electrode and a lower electrode sandwiching the piezoelectric layer in the first direction.

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