Elastic wave device

Abstract

Provided is an elastic wave device capable of suppressing deterioration of resonance characteristics. This elastic wave device comprises: a support member having a support substrate and an acoustic multilayer film; a piezoelectric layer having a thickness in a first direction; a functional electrode provided on at least one of the upper side and the lower side of the piezoelectric layer; a first electrode provided on at least one of the upper side and the lower side of the piezoelectric layer and having a first potential; a second electrode provided on at least one of the upper side and the lower side of the piezoelectric layer and having a second potential different from the first potential; and a protection part provided on the upper side of the support substrate. The acoustic multilayer film includes a high acoustic impedance layer and a low acoustic impedance layer. The first electrode and the second electrode are adjacent to each other. In plan view from the first direction, a non-piezoelectric region in which the piezoelectric layer is not provided is present between the first electrode and the second electrode. In the non-piezoelectric region, the protection part covers the surface of at least one low acoustic impedance layer.

Description

Elastic wave device

[0001] This invention relates to an elastic wave apparatus.

[0002] Patent Document 1 describes an elastic wave apparatus comprising an acoustic multilayer film having a laminated structure of a low acoustic impedance layer and a high acoustic impedance layer. Patent Document 2 describes an elastic wave apparatus in which a piezoelectric layer is not provided in at least a portion of the region between wirings.

[0003] International Publication No. 2021 / 060521, International Publication No. 2022 / 014440

[0004] In the acoustic wave apparatus having an acoustic multilayer film as shown in Patent Document 1, by not providing a piezoelectric layer in the region between wiring as shown in Patent Document 2, if the low acoustic impedance layer is exposed, moisture may penetrate from the low acoustic impedance layer, potentially degrading the resonance characteristics of the acoustic wave apparatus.

[0005] The present invention aims to provide an elastic wave device that can suppress the deterioration of resonance characteristics.

[0006] An elastic wave apparatus according to one embodiment comprises a support member having a support substrate and an acoustic multilayer film; a piezoelectric layer provided on the upper side of the acoustic multilayer film and having thickness in a first direction; a functional electrode provided on the upper side of the acoustic multilayer film and provided on at least one of the upper and lower sides of the piezoelectric layer; a first electrode provided on the upper side of the acoustic multilayer film and provided on at least one of the upper and lower sides of the piezoelectric layer and having a first potential; a second electrode provided on the upper side of the acoustic multilayer film and provided on at least one of the upper and lower sides of the piezoelectric layer and having a second potential different from the first potential; and a protective portion provided on the upper side of the support substrate, wherein the acoustic multilayer film includes a high acoustic impedance layer with relatively high acoustic impedance and a low acoustic impedance layer with relatively low acoustic impedance, the first electrode and the second electrode are adjacent to each other, and when viewed from the first direction in plan, there is a non-piezoelectric region between the first electrode and the second electrode where the piezoelectric layer is not provided, and in the non-piezoelectric region, the protective portion covers the surface of at least one layer of the low acoustic impedance layer.

[0007] According to the elastic wave apparatus of the present invention, resonance characteristics can be improved.

[0008] Figure 1 is a plan view showing the elastic wave apparatus of the first embodiment. Figure 2 is a cross-sectional view along the line II-II' in Figure 1. Figure 3 is a schematic cross-sectional view illustrating the bulk wave of the first-order thickness-slip mode propagating through the piezoelectric layer of the first embodiment. Figure 4 is a schematic cross-sectional view illustrating the amplitude direction of the bulk wave of the first-order thickness-slip mode propagating through the piezoelectric layer of the first embodiment. Figure 5 is an explanatory diagram showing an example of the resonance characteristics of the elastic wave apparatus of the first embodiment. Figure 6 is an explanatory diagram showing the relationship between d / 2p and the specific bandwidth as a resonator, where p is the distance between the centers of adjacent electrodes or the average distance between the centers, and d is the average thickness of the piezoelectric layer, in the elastic wave apparatus of the first embodiment. Figure 7 is a plan view showing an example in which a pair of electrodes are provided in the elastic wave apparatus of the first embodiment. Figure 8 is a reference diagram showing an example of the resonance characteristics of the elastic wave apparatus of the first embodiment. Figure 9 is an explanatory diagram showing the relationship between the relative bandwidth of the elastic wave apparatus of the first embodiment when a number of elastic wave resonators are configured, and the phase rotation amount of the spurious impedance normalized to 180 degrees as the spurious magnitude. Figure 10 is an explanatory diagram showing the relationship between d / 2p, the metallization ratio MR, and the relative bandwidth. Figure 11 is an explanatory diagram showing the relative bandwidth map for Euler angles (0°, θ, ψ) of LiNbO3 when d / p approaches 0. Figure 12 is a cross-sectional view along the line XII-XII' in Figure 1. Figure 13 is a diagram showing the resonance characteristics of the elastic wave apparatus according to the first embodiment and the elastic wave apparatus according to the comparative example. Figure 14 is a plan view showing the elastic wave apparatus according to the second embodiment. Figure 15 is a circuit diagram of the elastic wave apparatus according to the second embodiment. Figure 16 is a plan view showing the elastic wave apparatus according to the third embodiment. Figure 17 is a cross-sectional view along the line XVII-XVII' in Figure 16. Figure 18 is a cross-sectional view showing the elastic wave apparatus according to the fourth embodiment. Figure 19 is a cross-sectional view showing an elastic wave apparatus according to the fifth embodiment. Figure 20 is a cross-sectional view showing an elastic wave apparatus according to the sixth embodiment. Figure 21 is a cross-sectional view showing an elastic wave apparatus according to the seventh embodiment. Figure 22 is a cross-sectional view showing an elastic wave apparatus according to the first modified example. Figure 23 is a plan view showing an elastic wave apparatus according to the eighth embodiment. Figure 24 is a cross-sectional view along the line XXIV-XXIV' in Figure 23.

[0009] Embodiments of the present disclosure will be described in detail below with reference to the drawings. However, these embodiments do not limit the present disclosure. Each embodiment described in this disclosure is illustrative, and partial substitution or combination of configurations is possible between different embodiments. In modifications and subsequent embodiments, descriptions of matters common to the first embodiment will be omitted, and only the differences will be described. In particular, similar effects and benefits due to similar configurations will not be mentioned sequentially for each embodiment.

[0010] (First Embodiment) Figure 1 is a plan view showing the elastic wave apparatus of the first embodiment. Figure 2 is a cross-sectional view along the line II-II' in Figure 1. In Figure 1, the region where the piezoelectric layer 20 is not provided (non-piezoelectric region E) is shown in shaded area.

[0011] As shown in Figures 1 and 2, the elastic wave apparatus 10 according to the first embodiment includes a support substrate 11 and an acoustic multilayer film 43 as support members, a piezoelectric layer 20, a functional electrode 30, a first wiring electrode 51, a second wiring electrode 52, and a protective part 60. In the example of Figure 2, the elastic wave apparatus 10 is laminated on the support substrate 11 in the order of acoustic multilayer film 43 and piezoelectric layer 20, and the functional electrode 30, first wiring electrode 51 and second wiring electrode 52 are laminated on the piezoelectric layer 20.

[0012] The piezoelectric layer 20 is a flat plate-shaped layer having a first main surface 20a and a second main surface 20b opposite to the first main surface 20a. The piezoelectric layer 20 is made of lithium niobate (LiNbO ３ ) is formed of ). Alternatively, the piezoelectric layer 20 is lithium tantalate (LiTaO ３ ) may consist of . LiNbo ３ ya LiTaO ３ The cut angle is, for example, a Z-cut. LiNbO ３ ya LiTaO ３ The cut angle may be a rotational Y-cut or an X-cut, and a propagation direction of ±30° for Y propagation and X propagation is preferred. The piezoelectric layer 20 is lithium niobate (LiNbO ３ ) or lithium tantalate (LiTaO) ３It is preferable that the cut is a 120°±10° rotation Y-cut or a 90°±10° rotation Y-cut. Here, 120°±10° includes the range of 120°-10° or more and 120°+10° or less, and 90°±10° includes the range of 90°-10° or more and 90°+10° or less.

[0013] The thickness of the piezoelectric layer 20 is not particularly limited, but to effectively excite the thickness-sliding primary mode, it is preferably 50 nm to 1000 nm. The thickness of the piezoelectric layer 20 according to the first embodiment is, for example, about 180 nm.

[0014] The functional electrode 30 is an electrode of a resonator provided in the elastic wave apparatus 10. In the first embodiment, the functional electrode 30 is an IDT (Interdigital Transducer) electrode. In the example shown in Figures 1 and 2, the functional electrode 30 is provided on the first main surface 20a of the piezoelectric layer 20. As shown in Figure 1, the functional electrode 30 has electrode fingers 31, 32 and busbar electrodes 33, 34. Multiple electrode fingers 31 extend in the Y direction, and one end in the extending direction is connected to the busbar electrode 33. Multiple electrode fingers 32 extend in the Y direction, and the other end in the extending direction is connected to the busbar electrode 34. The multiple electrode fingers 31 and multiple electrode fingers 32 are arranged alternately in the X direction with spacing between them. The busbar electrodes 33 and 34 each extend in the X direction and are spaced apart in the Y direction. Multiple electrode fingers 31 and 32 are arranged between the busbar electrode 33 and the busbar electrode 34.

[0015] In the following description, the thickness direction of the piezoelectric layer 20 may be referred to as the Z direction, the extension direction of the electrode fingers 31 and 32 as the Y direction, and the arrangement direction of the electrode fingers 31 and 32 as the X direction. In the following description, a plan view refers to the arrangement when viewed from a direction perpendicular to the first main surface 20a of the piezoelectric layer 20. Here, the Z direction is an example of the "first direction" in this disclosure. In this disclosure, one of the first directions is referred to as "up" and the other as "down."

[0016] The distance between the centers of the widthwise sides of adjacent electrode fingers 31 and 32 in the X direction (hereinafter referred to as the electrode pitch) is preferably in the range of 1 μm or more and 10 μm or less. The electrode pitch is the distance between the center of the width dimension of electrode finger 31 in a direction perpendicular to the extending direction of electrode finger 31 and the center of the width dimension of electrode finger 32 in a direction perpendicular to the extending direction of electrode finger 32. The width of electrode fingers 31 and 32 (hereinafter referred to as electrode width), that is, the dimension in the direction perpendicular to the extending direction of electrode fingers 31 and 32, is preferably in the range of 150 nm or more and 1000 nm or less. Details of the electrode pitch and electrode width of electrode fingers 31 and 32 will be described later in Figures 12 and 13.

[0017] Furthermore, if at least one of the electrode fingers 31 and electrode fingers 32 is multiple (i.e., if electrode fingers 31 and electrode fingers 32 are considered as a pair of electrode sets, there are 1.5 or more pairs of electrode sets), the electrode pitch of electrode fingers 31 and electrode fingers 32 refers to the average value of the distance between the centers of adjacent electrode fingers 31 and electrode fingers 32 among the 1.5 or more pairs of electrode fingers 31 and electrode fingers 32.

[0018] Furthermore, in the first embodiment, since a Z-cut piezoelectric layer is used, the direction perpendicular to the extending direction of electrode fingers 31 and 32 is perpendicular to the polarization direction of the piezoelectric layer 20. This does not apply when a piezoelectric material with a different cut angle is used as the piezoelectric layer 20. Here, "perpendicular" is not limited to strictly perpendicular, but may also be approximately perpendicular, that is, the angle between the direction perpendicular to the extending direction of electrode fingers 31 and 32 and the polarization direction may be 90°-10° or more and 90°+10° or less.

[0019] The functional electrode 30 is made of a suitable metal or alloy such as Al or AlCu alloy. In the first embodiment, the functional electrode 30 has a structure in which an Al film is laminated on a titanium (Ti) film. However, an adhesion layer other than a Ti film may also be used.

[0020] More specifically, the electrode configuration of the functional electrode 30 is a multilayer film of Ti / AlCu / Ti / AlCu from the piezoelectric layer 20 side, with respective film thicknesses of 12 nm / 70 nm / 18 nm / 12 nm. The functional electrode 30 has a total of 51 electrode fingers 31 and 32. The electrode pitch between electrode fingers 31 and 32 is 2.38 μm, and the electrode width of each is 0.6 μm.

[0021] Here, the crossing region C (excitation region) shown in Figure 1 is the region where electrode fingers 31 and 32 overlap when viewed in the X direction. The length of the crossing region C is the dimension of electrode fingers 31 and 32 in the extending direction within the crossing region C. In this embodiment, the length of the crossing region C is, for example, 40 μm.

[0022] During operation, an AC voltage is applied between multiple electrode fingers 31 and multiple electrode fingers 32. More specifically, an AC voltage is applied between busbar electrode 33 and busbar electrode 34. This makes it possible to obtain resonance characteristics using the bulk wave of the thickness-slip first mode excited in the piezoelectric layer 20.

[0023] Furthermore, in the elastic wave apparatus 10, when the thickness of the piezoelectric layer 20 is d and the pitch between the multiple pairs of electrode fingers 31 and electrode fingers 32 is p, d / p is set to 0.5 or less. As a result, the bulk wave of the thickness-slip first mode is effectively excited, and good resonance characteristics can be obtained. More preferably, d / p is 0.24 or less, in which case even better resonance characteristics can be obtained.

[0024] In the elastic wave device 10 of the first embodiment, because it has the above configuration, even if the logarithm of electrode fingers 31 and 32 is reduced in an attempt to miniaturize it, a decrease in the Q value is unlikely to occur. 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 reflectors are not required is because it utilizes a bulk wave of the first-order mode of thickness sliding.

[0025] The first wiring electrode 51 is an electrode for wiring provided on the upper side of the acoustic multilayer film 43. In the example of FIG. 2, the first wiring electrode 51 is provided on the first main surface 20a of the piezoelectric layer 20. The first wiring electrode 51 is connected to the input potential of the resonator and is connected to the first bus bar electrode 33 of the functional electrode 30. In the example of FIG. 1, the first wiring electrode 51 is connected to one side in the X direction of the first bus bar electrode 33 and extends in the X direction, but this is merely an example.

[0026] The second wiring electrode 52 is an electrode for wiring provided on the upper side of the acoustic multilayer film 43. In the example of FIG. 2, the second wiring electrode 52 is provided on the first main surface 20a of the piezoelectric layer 20. The second wiring electrode 52 is connected to the output potential of the resonator and is connected to the second bus bar electrode 34 of the functional electrode 30. In the example of FIG. 1, the second wiring electrode 52 is connected to the other side in the X direction of the second bus bar electrode 34 and extends in an L shape along the length direction of the electrode finger 31, the first bus bar electrode 33, and the first wiring electrode 51 at the end in the X direction, but this is merely an example.

[0027] The first wiring electrode 51 and the second wiring electrode 52 are made of an appropriate metal or alloy such as Al, an AlCu alloy, etc. The materials of the first wiring electrode 51 and the second wiring electrode 52 may be the same as those of the functional electrode 30.

[0028] The support member is disposed to face the second main surface 20b of the piezoelectric layer 20. The support member includes the support substrate 11 and the acoustic multilayer film 43.

[0029] The support substrate 11 is formed of silicon (Si). The surface orientation on the surface of the Si side of the piezoelectric layer 20 may be (100) or (110), or may be (111). Preferably, high-resistance Si with a resistivity of 4 kΩ or more is desirable. However, the support substrate 11 can also be configured using an appropriate insulating material or semiconductor material. Examples of the material for the support substrate 11 include piezoelectric materials such as aluminum oxide, lithium tantalate, lithium niobate, and quartz, various ceramics such as alumina, magnesia, sapphire, silicon nitride, aluminum nitride, silicon carbide, zirconia, cordierite, mullite, steatite, and forsterite, dielectrics such as diamond and glass, and semiconductors such as gallium nitride.

[0030] The acoustic multilayer film 43 is laminated on the piezoelectric layer 20 side of the support substrate 11. The acoustic multilayer film 43 has a laminated structure including low acoustic impedance layers 43a, 43c, 43e with relatively low acoustic impedance and high acoustic impedance layers 43b, 43d with relatively high acoustic impedance. Thereby, the thickness-slip fundamental mode bulk wave can be confined within the piezoelectric layer 20.

[0031] In the acoustic multilayer film 43, the number of laminated layers of the low acoustic impedance layers 43a, 43c, 43e and the high acoustic impedance layers 43b, 43d is not particularly limited. At least one layer of the high acoustic impedance layers 43b, 43d may be arranged on the side farther from the piezoelectric layer 20 than the low acoustic impedance layers 43a, 43c, 43e. Also, it is preferable that the layer on the uppermost side of the acoustic multilayer film 43 is the low acoustic impedance layer 43a. Thereby, since the difference in acoustic impedance between the piezoelectric layer 20 and the layer of the acoustic multilayer film 43 closest to the piezoelectric layer 20 becomes large, the wave confinement effect of the acoustic multilayer film 43 can be improved.

[0032] The low acoustic impedance layers 43a, 43c, 43e are silicon oxide (SiO ２It is preferable that the layers include the following. This allows the acoustic impedance of the low acoustic impedance layers 43a, 43c, and 43e to be reduced more significantly than that of the high acoustic impedance layers 43b and 43d, thereby improving the wave confinement effect of the acoustic multilayer film 43.

[0033] The materials for the high acoustic impedance layers 43b and 43d include, for example, tungsten carbide (WC), tantalum carbide (TaC), rhenium oxide (ReO3), silicon chromium carbon (CrCSI), niobium carbide (NbC), zinc carbide (ZrC), zinc nitride (TiC), and lanthanum boride (LaB). ６ ), vanadium carbide (VC), aluminum nitride (AlN), silicon carbide (SiC), yttrium oxide (Y ２ O ３ ), magnesium oxide (MgO), silicon nitride (Si ３ N ４ ), boron carbide (B ４ C), Strontium fluoride (SrF ２ ), barium fluoride (BaF ２ ), tantalum oxide (Ta ２ O ５ ), hafnium oxide (HfO ２ ), ytterbium oxide (Yb ２ O ３ ), tungsten oxide (WO ３ ), can be at least one of hafnium nitride (HfN), tungsten nitride (WN), platinum (Pt), tungsten (W), copper (Cu), gold (Au), and silver (Ag).

[0034] The materials for the low acoustic impedance layers 43a, 43c, and 43e and the high acoustic impedance layers 43b and 43d are not limited to these, and can be made of any suitable material as long as the above acoustic impedance relationship is satisfied. Also, the low acoustic impedance layers 43a, 43c, and 43e are not limited to being made of the same material, but may be made of different materials. The high acoustic impedance layers 43b and 43d are not limited to being made of the same material, but may be made of different materials.

[0035] Figure 3 is a schematic cross-sectional view illustrating the bulk wave of the first-order thickness-slip mode propagating through the piezoelectric layer of the first embodiment. Figure 4 is a schematic cross-sectional view illustrating the amplitude direction of the bulk wave of the first-order thickness-slip mode propagating through the piezoelectric layer of the first embodiment.

[0036] As shown in Figure 3, in the elastic wave device 10 of the first embodiment, since the vibration displacement is in the thickness sliding direction, the wave propagates almost entirely in the direction connecting the first main surface 20a and the second main surface 20b of the piezoelectric layer 20, i.e., in the Z direction, and resonates. That is, the X-direction component of the wave is significantly smaller than the Z-direction component. And since the resonance characteristics are obtained by the propagation of this Z-direction wave, a reflector is not required. Therefore, no propagation loss occurs when the wave propagates to the reflector. Accordingly, even if the number of electrode pairs consisting of electrode fingers 31 and electrode fingers 32 is reduced in an attempt to miniaturize the device, a decrease in the Q value is unlikely to occur.

[0037] Furthermore, as shown in Figure 4, the amplitude direction of the bulk wave in the first-order thickness-slip mode is reversed between the first region 251, which is included in the intersection region C (see Figure 1) of the piezoelectric layer 20, and the second region 252, which is also included in the intersection region C. Figure 4 schematically shows the bulk wave when a voltage is applied between electrode finger 31 and electrode finger 32 such that electrode finger 32 is at a higher potential than electrode finger 31. Here, the virtual plane VP1 is a plane that is perpendicular to the thickness direction of the piezoelectric layer 20 and divides the piezoelectric layer 20 in two. The first region 251 is the region between the virtual plane VP1 and the first main surface 20a within the intersection region C. The second region 252 is the region between the virtual plane VP1 and the second main surface 20b within the intersection region C.

[0038] In the elastic wave device 10, at least one pair of electrodes, consisting of electrode finger 31 and electrode finger 32, are arranged. However, since waves are not propagated in the X direction, it is not necessarily required that there be multiple pairs of these electrode fingers 31 and 32. In other words, it is sufficient that at least one pair of electrodes is provided.

[0039] For example, electrode finger 31 is an electrode connected to a hot potential, and electrode finger 32 is an electrode connected to a ground potential. However, electrode finger 31 may be connected to a ground potential and electrode finger 32 may be connected to a hot potential. In the first embodiment, at least one pair of electrodes are, as described above, electrodes connected to a hot potential or electrodes connected to a ground potential, and no floating electrodes are provided.

[0040] Figure 5 is an explanatory diagram showing an example of the resonance characteristics of the elastic wave apparatus of the first embodiment. The design parameters of the elastic wave apparatus 10 that obtained the resonance characteristics shown in Figure 5 are as follows. Here, the first main surface 20a and the second main surface 20b of the piezoelectric layer 20 are provided with a silicon oxide film with a thickness of 1 μm.

[0041] Piezoelectric layer 20: LiNbO with Euler angles (0°, 0°, 90°) ３ Thickness of piezoelectric layer 20: 400 nm

[0042] Length of cross region C: 40 μm Number of electrode pairs consisting of electrode fingers 31 and 32: 21 Pitch between electrode fingers 31 and 32: 3 μm Width of electrode fingers 31 and 32: 500 nm d / p: 0.133 Support substrate 11: Si

[0043] As is clear from Figure 5, good resonance characteristics with a relative bandwidth of 12.5% ​​are obtained despite the absence of a reflector.

[0044] By the way, if the thickness of the piezoelectric layer 20 is d and the pitch between electrode fingers 31 and 32 is p, then in the first embodiment, d / p is 0.5 or less, more preferably 0.24 or less. This will be explained with reference to Figure 6.

[0045] Figure 6 is an explanatory diagram showing the relationship between d / 2p and the specific bandwidth of the resonator in the elastic wave apparatus of the first embodiment, where p is the distance between the centers of adjacent electrodes or the average distance between the centers, and d is the average thickness of the piezoelectric layer. In Figure 6, multiple elastic wave apparatuses were obtained in the same manner as the elastic wave apparatus that obtained the resonance characteristics shown in Figure 5, except that d / 2p was changed.

[0046] As shown in Figure 6, when d / 2p exceeds 0.25, i.e., d / p > 0.5, the relative bandwidth is less than 5% even when d / p is adjusted. In contrast, when d / 2p ≤ 0.25, i.e., d / p ≤ 0.5, the relative bandwidth can be increased to 5% or more by changing d / p within that range, 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, by adjusting d / p within this range, a resonator with an even wider relative bandwidth can be obtained, and a resonator with an even higher coupling coefficient can be realized. Therefore, it can be seen that by setting d / p to 0.5 or less, a resonator with a high coupling coefficient can be constructed using the bulk wave of the thickness-slip first mode described above.

[0047] Regarding the thickness d of the piezoelectric layer 20, if the piezoelectric layer 20 has variations in thickness, the average value of its thickness should be used.

[0048] Figure 7 is a plan view showing an example in which a pair of electrodes is provided in the elastic wave apparatus of the first embodiment. In the elastic wave apparatus 10, a pair of electrodes having electrode fingers 31 and electrode fingers 32 are provided on the first main surface 20a of the piezoelectric layer 20. In Figure 7, K is the crossover width. As described above, in the elastic wave apparatus 10 of this disclosure, the number of electrode pairs may be one. Even in this case, if the above d / p is 0.5 or less, the bulk wave of the thickness-slip first mode can be effectively excited.

[0049] In the elastic wave apparatus 10, it is preferable that the metallization ratio MR of the adjacent electrode fingers 31 and 32 with respect to the crossing region C satisfies MR ≤ 1.75 (d / p) + 0.075. In this case, spurious emissions can be effectively reduced. This will be explained with reference to Figures 8 and 9.

[0050] Figure 8 is a reference diagram showing an example of the resonance characteristics of the elastic wave apparatus of the first embodiment. As shown in Figure 8, the spurious signal indicated by arrow B appears between the resonant frequency and the anti-resonant frequency. Note that d / p = 0.08 and LiNbO ３The Euler angles were set to 0°, 0°, and 90°. Furthermore, the metallization ratio MR was set to 0.35.

[0051] The metallization ratio MR will be explained with reference to Figure 1. In the electrode structure of Figure 1, if we focus on a pair of electrode fingers 31 and 32, we assume that only this pair of electrode fingers 31 and 32 are provided. In this case, the area enclosed by the dashed line becomes the intersection region C. This intersection region C is the area on electrode finger 31 that overlaps with electrode finger 32 when viewed in a direction perpendicular to the extending direction of electrode fingers 31 and 32, i.e., in the opposing direction, the area on electrode finger 31 that overlaps with electrode finger 32, the area on electrode finger 32 that overlaps with electrode finger 31, and the area between electrode finger 31 and electrode finger 32 that overlaps. The area of ​​electrode fingers 31 and 32 within the intersection region C relative to the area of ​​the intersection region C is the metallization ratio MR. In other words, the metallization ratio MR is the ratio of the area of ​​the metallized portion to the area of ​​the intersection region C.

[0052] Furthermore, if multiple pairs of electrode fingers 31 and electrode fingers 32 are provided, the ratio of the metallized portion included in all intersection regions C to the total area of ​​the intersection regions C should be defined as MR.

[0053] Figure 9 is an explanatory diagram showing the relationship between the relative bandwidth of the elastic wave device of the first embodiment, when a large number of elastic wave resonators are configured, and the phase rotation amount of the spurious impedance normalized by 180 degrees as the spurious magnitude. The relative bandwidth was adjusted by changing various aspects of the thickness of the piezoelectric layer 20 and the dimensions of the electrode fingers 31 and 32. Also, Figure 9 shows the Z-cut LiNbO ３ The results shown are for the case where a piezoelectric layer 20 consisting of the above is used, but a similar trend is observed when piezoelectric layers 20 with other cut angles are used.

[0054] In the region enclosed by the ellipse J in Figure 9, the spurious emission is large at 1.0. As is clear from Figure 9, when the relative bandwidth exceeds 0.17, that is, when it exceeds 17%, large spurious emissions with a spurious emission level of 1 or more appear within the passband, even if the parameters constituting the relative bandwidth are changed. In other words, as shown in the resonance characteristics in Figure 8, large spurious emissions indicated by arrow B appear within the bandwidth. Therefore, it is preferable that the relative bandwidth be 17% or less. In this case, spurious emissions can be reduced by adjusting the film thickness of the piezoelectric layer 20 and the dimensions of the electrode fingers 31 and 32.

[0055] Figure 10 is an explanatory diagram showing the relationship between d / 2p, the metallization ratio MR, and the relative bandwidth. In the elastic wave apparatus 10 of the first embodiment, various elastic wave apparatuses 10 with different d / 2p and MR were configured, and the relative bandwidth was measured. The hatched area to the right of the dashed line D in Figure 10 is the region where the relative bandwidth is 17% or less. The boundary between this hatched region and the unhatched region is represented by MR = 3.5(d / 2p) + 0.075. That is, MR = 1.75(d / p) + 0.075. Therefore, preferably, MR ≤ 1.75(d / p) + 0.075. In that case, it is easy to keep the relative bandwidth at 17% or less. More preferably, it is the region to the right of MR = 3.5(d / 2p) + 0.05, shown by the dashed line D1 in Figure 10. In other words, if MR ≤ 1.75 (d / p) + 0.05, the relative bandwidth can be reliably reduced to 17% or less.

[0056] Figure 11 shows LiNbO when d / p approaches 0. ３ This is an explanatory diagram showing the relative bandwidth map for Euler angles (0°, θ, ψ). The hatched area in Figure 11 is the region where a relative bandwidth of at least 5% is obtained. Approximating the range of this region, it is represented by the following equations (1), (2), and (3).

[0057] (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°) ...Formula (2) (0°±10°, {180°-30°(1-(ψ-90) ２ ( / 8100) １／２} ~180°, any ψ) ...Equation (3)

[0058] Therefore, in the case of the Euler angle range of equation (1), equation (2), or equation (3) above, the relative bandwidth can be made sufficiently wide, which is preferable.

[0059] Figure 12 is a cross-sectional view along the line XII-XII' in Figure 1. As shown in Figures 1 and 12, the elastic wave apparatus 10 according to the first embodiment has a non-piezoelectric region E in which, when viewed from the Z direction in a plan view, there is no piezoelectric layer 20 between wirings with different potentials. The non-piezoelectric region E is located between the first electrode and the second electrode when viewed from the Z direction in a plan view.

[0060] Here, the first electrode is an electrode provided on the upper side of the acoustic multilayer film 43 and having a first potential. In the first embodiment, the first wiring electrode 51, the electrode finger 31 at the end in the X direction, and the first busbar electrode 33 correspond to the first electrode. That is, in the first embodiment, the first potential is the input potential of the resonator of the elastic wave device 10.

[0061] Here, the second electrode is an electrode provided on the upper side of the acoustic multilayer film 43, adjacent to the first electrode, and having a second potential different from the first potential. In this disclosure, the second electrode being adjacent to the first electrode means that, when viewed in a plan view in the first direction (Z direction), there are no other electrodes between the first electrode and the second electrode. In the first embodiment, the second wiring electrode 52 corresponds to the second electrode. That is, in the first embodiment, the second potential is the output potential of the resonator of the elastic wave device 10.

[0062] Therefore, in the first embodiment, there is a non-piezoelectric region E between the first wiring electrode 51, the electrode finger 31 at the end in the X direction, and the first busbar electrode 33, and the second wiring electrode 52. This suppresses the propagation of unwanted waves between the first and second electrodes, thereby improving the resonance characteristics. In the example of Figure 1, the non-piezoelectric region E exists throughout the entire region between the first and second electrodes, but it is not limited to this, and it is sufficient if the non-piezoelectric region E is in at least a part of the region between the first and second electrodes.

[0063] In the first embodiment, when viewed in plan in the Z direction, the non-piezoelectric region E has a support substrate 11, an acoustic multilayer film 43, and a protective portion 60 stacked on top of each other. That is, in the non-piezoelectric region E of the first embodiment, only the piezoelectric layer 20 is removed.

[0064] In the first embodiment, the upper surface of the acoustic multilayer film 43 in the non-piezoelectric region E has the main surface of the low acoustic impedance layer 43a. That is, in the non-piezoelectric region E, the uppermost layer of the acoustic multilayer film 43 is the low acoustic impedance layer 43a. Here, since the piezoelectric layer 20 is not provided in the non-piezoelectric region E, if the protective part 60 is not provided, the main surface of the low acoustic impedance layer 43a is exposed. In this case, moisture may penetrate from the main surface of the low acoustic impedance layer 43a, potentially degrading the resonance characteristics. In particular, if the low acoustic impedance layer 43a contains silicon oxide, the low acoustic impedance layer 43a easily absorbs moisture, and it is even more important to prevent moisture from penetrating the low acoustic impedance layer 43a.

[0065] In the first embodiment, the protective portion 60 is provided so as to cover the main surface of the low acoustic impedance layer 43a in the non-piezoelectric region E. As a result, the protective portion 60 suppresses the absorption of moisture by the low acoustic impedance layer 43a, thereby suppressing deterioration of the resonance characteristics.

[0066] In the examples shown in Figures 1 and 12, the protective portion 60 is provided so as to cover the inner surface 20c of the piezoelectric layer 20 and the main surface of the low acoustic impedance layer 43a, and has a tray-like shape.

[0067] The protective part 60 preferably contains at least one of nitrides, carbides, polymer compounds, and metals. Nitrides include, for example, silicon nitride (SiN). Carbides include, for example, silicon carbide (SiC). Metals include, for example, gold (Au). This allows the protective part 60 to better block moisture, thereby further suppressing the deterioration of resonance characteristics.

[0068] The protective portion 60 is preferably made of a material with a higher thermal conductivity than the piezoelectric layer 20. This allows the protective portion 60 to dissipate heat from the support member, thereby improving the heat dissipation performance of the elastic wave device.

[0069] It should be noted that the elastic wave apparatus according to the first embodiment is not limited to the elastic wave apparatus 10 described above. For example, the protective portion 60 may be provided only on the main surface of the low acoustic impedance layer 43a. For example, the protective portion 60 may be in contact with at least one of the piezoelectric layer 20, the first wiring electrode 51, and the second wiring electrode 52. For example, the upper surface of the protective portion 60 may be formed to be flush with the first main surface 20a of the piezoelectric layer 20.

[0070] (Example) Figure 13 shows the resonance characteristics of the elastic wave apparatus according to the first embodiment and the elastic wave apparatus according to the comparative example. Here, the elastic wave apparatus according to the comparative example in Figure 13 is an elastic wave apparatus in which the elastic wave apparatus 10 according to the first embodiment is provided without the protective part 60. As shown in Figure 13, the elastic wave apparatus 10 according to the first embodiment, which has the protective part 60, has smaller attenuation of the main wave compared to the elastic wave apparatus according to the comparative example that does not have the protective part 60, and therefore the resonance characteristics are improved.

[0071] (Second Embodiment) Figure 14 is a plan view showing the elastic wave apparatus according to the second embodiment. Figure 15 is a circuit diagram of the elastic wave apparatus according to the second embodiment. As shown in Figure 14, the elastic wave apparatus 10A according to the second embodiment differs from the elastic wave apparatus 10 according to the first embodiment in that it has a plurality of resonators. Note that in Figure 14, the region where the piezoelectric layer 20 is not provided (non-piezoelectric region E) is shown in shaded area.

[0072] In the examples shown in Figures 14 and 15, the elastic wave apparatus 1A according to the second embodiment is a so-called ladder-type filter that includes a series arm resonator group S10, S20, S30, S40, S50 inserted in series in the signal path from the input terminal IN to the output terminal OUT (first path), and a parallel arm resonator group P10, P20, P30, P40 inserted in the signal path between the node on the first path and the ground GND (second path). Here, each of the series arm resonator group S10, S20, S30, S40, S50 and the parallel arm resonator group P10, P20, P30, P40 has two resonators connected in parallel with each other.

[0073] The series arm resonator group S10 has one terminal electrically connected to the input terminal IN and the other terminal electrically connected to node N1 on the first path. The series arm resonator group S10 includes two series arm resonators S11 and S12 connected in parallel with each other. The two series arm resonators S11 and S12 are split resonators. The series arm resonator group S20 has one terminal electrically connected to node N1 on the first path and the other terminal electrically connected to node N2 on the first path. The series arm resonator group S20 includes two series arm resonators S21 and S22 connected in parallel with each other. The series arm resonator group S30 has one terminal electrically connected to node N2 on the first path and the other terminal electrically connected to node N3 on the first path. The series arm resonator group S30 includes two series arm resonators S31 and S32 connected in parallel with each other. The series arm resonator group S40 has one terminal electrically connected to node N3 on the first path and the other terminal electrically connected to node N4 on the first path. The series arm resonator group S40 includes two series arm resonators S41 and S42 connected in parallel with each other. The series arm resonator group S50 has one terminal electrically connected to node N4 on the first path and the other terminal electrically connected to node N4 on the first path. The series arm resonator group S50 includes two series arm resonators S51 and S52 connected in parallel with each other.

[0074] The parallel arm resonator group P10 has one terminal electrically connected to node N1 on the first path and the other terminal electrically connected to ground GND. The parallel arm resonator group P10 includes two parallel arm resonators P11 and P12 connected in parallel with each other. The parallel arm resonator group P20 has one terminal electrically connected to node N3 on the first path and the other terminal electrically connected to ground GND. The parallel arm resonator group P20 includes two parallel arm resonators P21 and P22 connected in parallel with each other. The parallel arm resonator group P30 has one terminal electrically connected to node N4 on the first path and the other terminal electrically connected to ground GND. The parallel arm resonator group P30 includes two parallel arm resonators P31 and P32 connected in parallel with each other. The parallel arm resonator group P40 has one terminal electrically connected to the output terminal OUT and the other terminal electrically connected to ground GND. The parallel arm resonator group P40 includes two parallel arm resonators P41 and P42 connected in parallel to each other.

[0075] In the second embodiment, the input terminal IN, nodes N1 to N4, or output terminal OUT correspond to the first electrode, and the ground GND corresponds to the second electrode. That is, in the second embodiment, there is a non-piezoelectric region E between the input terminal IN, nodes N1 to N4, output terminal OUT, and ground GND, and the piezoelectric layer 20 is not provided. As a result, the propagation of unwanted waves between the first electrode and the second electrode can be suppressed, and the resonance characteristics can be improved.

[0076] In the second embodiment, there are no non-piezoelectric regions in the regions M1 to M5 between the resonators connected in parallel. In other words, the piezoelectric layer 20 is continuously provided in the regions M1 to M5 between the resonators connected in parallel. Since the input potential and output potential are the same for the resonators connected in parallel, unwanted wave propagation is unlikely to occur even if there is no non-piezoelectric region E in the piezoelectric layer of regions M1 to M5. Therefore, it is possible to suppress the propagation of unwanted waves while also suppressing the intrusion of moisture from regions M1 to M5.

[0077] (Third Embodiment) Figure 16 is a plan view showing an elastic wave apparatus according to the third embodiment. Figure 17 is a cross-sectional view along the line XVII-XVII' in Figure 16. In Figure 16, regions where the piezoelectric layer 20 is not provided (non-piezoelectric region E and region F) are shown in shaded areas. As shown in Figures 16 and 17, the elastic wave apparatus 10B according to the third embodiment differs from the elastic wave apparatus 10 according to the first embodiment in that the acoustic multilayer film 43 is not provided in the non-piezoelectric region E and there is a protective portion 70 outside the outer surface 20d of the piezoelectric layer 20.

[0078] As shown in Figure 17, in the third embodiment, when viewed in plan in the Z direction, the support substrate 11 and the protective portion 60 are stacked in the non-piezoelectric region E. That is, in the non-piezoelectric region E of the first embodiment, the piezoelectric layer 20 and the acoustic multilayer film 43 are removed.

[0079] In the third embodiment, the non-piezoelectric region E has a side surface of the acoustic multilayer film 43. Here, since the piezoelectric layer 20 is not provided in the non-piezoelectric region E, if the protective portion 60 is not provided, the side surfaces of the low acoustic impedance layers 43a, 43c, and 43e will be exposed, and moisture may penetrate from the side surfaces of the low acoustic impedance layers 43a, 43c, and 43e, potentially degrading the resonance characteristics. In particular, when the low acoustic impedance layers 43a, 43c, and 43e contain silicon oxide, the low acoustic impedance layers 43a, 43c, and 43e are prone to absorbing moisture, so it is even more important to prevent moisture from penetrating the low acoustic impedance layers 43a, 43c, and 43e.

[0080] In the third embodiment, the protective portion 60 is provided so as to cover the sides of the low acoustic impedance layers 43a, 43c, and 43e in the non-piezoelectric region E. As a result, the protective portion 60 suppresses the absorption of moisture by the low acoustic impedance layers 43a, 43c, and 43e, thereby suppressing deterioration of the resonance characteristics. In the examples of Figures 16 and 17, the protective portion 60 has a tray-like shape and is provided so as to cover the inner surface 20c of the piezoelectric layer 20, the side of the acoustic multilayer film 43, and the main surface of the support substrate 11.

[0081] In the third embodiment, when viewed in plan in the Z direction, the outer surface 20d of the piezoelectric layer 20 is located within the region enclosed by the outer surface of the support substrate 11. That is, when viewed in plan in the Z direction, the piezoelectric layer 20 is not provided in the region F between the outer surface 11a of the support substrate 11 and the outer surface 20d of the piezoelectric layer 20.

[0082] As shown in Figure 17, in the third embodiment, when viewed in plan in the Z direction, the support substrate 11 and the protective portion 60 are laminated in the region F between the outer surface 11a of the support substrate 11 and the outer surface 20d of the piezoelectric layer 20. In other words, in the third embodiment, the piezoelectric layer 20 and the acoustic multilayer film 43 are removed in the region F between the outer surface 11a of the support substrate 11 and the outer surface 20d of the piezoelectric layer 20.

[0083] In the third embodiment, the protective portion 70 is provided so as to cover the outer surface 11a of the support substrate 11, the sides of the low acoustic impedance layers 43a, 43c, and 43e, and a portion of the main surface of the support substrate 11. As a result, the protective portion 70 suppresses the absorption of moisture by the low acoustic impedance layers 43a, 43c, and 43e, thereby suppressing deterioration of the resonance characteristics.

[0084] In the example shown in Figure 17, the protective portion 70 is provided to cover the outer surface 20d of the piezoelectric layer 20, the side surface of the acoustic multilayer film 43, and the main surface of the support substrate 11, and has an L-shape. The material of the protective portion 70 may be the same as that of the protective portion 60.

[0085] In the third embodiment, the protective parts 60 and 70 are in contact with the support substrate 11 in the non-piezoelectric region E and region F, respectively. In the example shown in Figure 17, the protective part 60 is provided to cover the main surface of the support substrate 11 in the non-piezoelectric region E. The protective part 70 is provided to cover a portion of the main surface of the support substrate 11 in region F. This allows the heat from the support substrate 11 to be dissipated by the protective parts 60 and 70.

[0086] Furthermore, the elastic wave apparatus according to the third embodiment is not limited to the elastic wave apparatus 10B described above.

[0087] For example, the protective portions 60 and 70 may be provided only on the side surface of at least one of the low acoustic impedance layers 43a, 43c, and 43e. That is, the protective portions 60 and 70 do not have to be in contact with the main surface of the support substrate 11. Here, it is preferable that the protective portion 60 is provided on the side surface of the low acoustic impedance layer containing silicon oxide among the low acoustic impedance layers 43a, 43c, and 43e.

[0088] For example, the protective portion 70 is not an essential component and may not be provided. Also, when viewed in plan in the Z direction, the outer surface of the support substrate 11 and the outer surface 20d of the piezoelectric layer 20 may overlap.

[0089] For example, an acoustic multilayer film 43 may be provided in at least a portion of the region between the piezoelectric layer 20 and the outer surface 20d. In this case, it is preferable that the protective portion 70 is provided so as to cover the main surface of the low acoustic impedance layer 43a in region F.

[0090] (Fourth Embodiment) Figure 18 is a cross-sectional view showing an elastic wave apparatus according to the fourth embodiment. As shown in Figure 18, the elastic wave apparatus 10C according to the fourth embodiment differs from the elastic wave apparatus 10C according to the third embodiment in that the protective portion 60A includes a conductor layer.

[0091] In the fourth embodiment, the protective portion 60A includes a first conductor layer 61 and a second conductor layer 62 as conductor layers. This improves the heat dissipation of the support substrate 11 by the protective portion 60A. In the example shown in Figure 18, the first conductor layer 61 extends from the first electrode (first wiring electrode 51) to the support substrate 11, and the second conductor layer 62 is made of a conductor and extends from the second electrode (second wiring electrode 52) to the support substrate 11. The first conductor layer 61 and the second conductor layer 62 are provided so as to cover the inner surface 20c of the piezoelectric layer 20, the side surface of the acoustic multilayer film 43, and a part of the main surface of the support substrate 11.

[0092] In the fourth embodiment, the first conductive layer 41A and the second conductive layer 41B are not in contact in the non-piezoelectric region E. That is, the first conductive layer 41A and the second conductive layer 41B are not electrically connected in the non-piezoelectric region E. This prevents the first electrode and the second electrode, which have different potentials, from being short-circuited by the protective unit.

[0093] (Fifth Embodiment) Figure 19 is a cross-sectional view showing an elastic wave apparatus according to the fifth embodiment. As shown in Figure 19, the elastic wave apparatus 10D according to the fourth embodiment differs from the elastic wave apparatus 10C according to the fourth embodiment in that the first conductor layer 61 and the second conductor layer 62 are laminated on the dielectric layer 63.

[0094] In the fifth embodiment, the protective portion 60B includes a first conductive layer 61, a second conductive layer 62, and a dielectric layer 63. The dielectric layer 63 is a layer made of dielectric material. In the fifth embodiment, the first conductive layer 41A and the second conductive layer 41B are laminated on the inner surface of the dielectric layer 63.

[0095] In the fifth embodiment, the dielectric layer 63 is provided between the conductor layer (first conductor layer 61 and second conductor layer 62) and the support substrate 11. This prevents short circuits between the support substrate and the conductor layer, even if the support substrate is not an insulator. In the example shown in Figure 19, the dielectric layer 63 has a tray-like shape and is provided to cover the inner surface 20c of the piezoelectric layer 20, the side surface of the acoustic multilayer film 43, and the main surface of the support substrate 11.

[0096] (Sixth Embodiment) Figure 20 is a cross-sectional view showing an elastic wave apparatus according to the sixth embodiment. As shown in Figure 20, the elastic wave apparatus 10E according to the sixth embodiment differs from the elastic wave apparatus 10D according to the fifth embodiment in that a dielectric layer 63 is laminated on the first conductor layer 61 and the second conductor layer 62.

[0097] In the example shown in Figure 20, the first conductor layer 61 and the second conductor layer 62 are provided so as to cover the inner surface 20c of the piezoelectric layer 20 and the side surface of the acoustic multilayer film 43. The dielectric layer 63 is tray-shaped and is provided so as to cover the inner surfaces of the first conductor layer 61 and the second conductor layer 62 and the main surface of the support substrate 11.

[0098] (Seventh Embodiment) Figure 21 is a cross-sectional view showing an elastic wave apparatus according to the seventh embodiment. As shown in Figure 21, the elastic wave apparatus 10F according to the seventh embodiment differs from the elastic wave apparatus 10B according to the third embodiment in that the support member further has an intermediate layer 12.

[0099] The intermediate layer 12 is provided between the support substrate 11 and the acoustic multilayer film 43. In the example shown in Figure 21, in the non-piezoelectric region E, the support substrate 11, the intermediate layer 12, and the protective portion 60 are laminated, and the acoustic multilayer film 43 and the piezoelectric layer 20 are removed. The material of the intermediate layer is not particularly limited and can be, for example, silicon oxide.

[0100] In the example shown in Figure 21, the protective portion 60 is tray-shaped and is provided to cover the inner surface 20c of the piezoelectric layer 20, the side surface of the acoustic multilayer film 43, and the main surface of the intermediate layer 12. However, it is not limited to this, and for example, the protective portion 60 does not have to be in contact with the main surface of the intermediate layer 12.

[0101] (First Modified Example) Figure 22 is a cross-sectional view showing an elastic wave apparatus according to the first modified example. The elastic wave apparatus according to the seventh embodiment is not limited to the elastic wave apparatus 10F described above, but may be the elastic wave apparatus 10G shown in Figure 22. In the first modified example, the intermediate layer 12 is not provided in the non-piezoelectric region E. That is, in the non-piezoelectric region E, the support substrate 11 and the protective part 60 are laminated, and the intermediate layer 12, the acoustic multilayer film 43 and the piezoelectric layer 20 are removed.

[0102] In the example shown in Figure 22, the protective portion 60 is tray-shaped and is provided to cover the inner surface 20c of the piezoelectric layer 20, the side surface of the acoustic multilayer film 43, the side surface of the intermediate layer 12, and the main surface of the support substrate 11. However, it is not limited to this, and for example, the protective portion 60 does not have to be in contact with the side surface of the intermediate layer 12.

[0103] (Eighth Embodiment) Figure 23 is a plan view showing the elastic wave apparatus according to the eighth embodiment. Figure 24 is a cross-sectional view along the line XXIV-XXIV' in Figure 23. In Figure 23, the region where the piezoelectric layer 20 is not provided (non-piezoelectric region E) is shown in shaded area. The elastic wave apparatus 10H according to the eighth embodiment differs from the elastic wave apparatus 10 according to the first embodiment in that it is a piezoelectric element that utilizes bulk waves, i.e., a BAW (Bulk Acoustic Wave) element.

[0104] In the eighth embodiment, the functional electrode comprises an upper electrode 35 and a lower electrode 36. As shown in Figure 24, the upper electrode 35 is a flat electrode provided on the upper side of the piezoelectric layer 20. The lower electrode 36 is a flat electrode provided on the lower side of the piezoelectric layer 20. In the example of Figure 23, the upper electrode 35 is provided on the first main surface 20a of the piezoelectric layer 20, and the lower electrode 36 is provided below the second main surface 20b of the piezoelectric layer 20. Here, the lower electrode 36 is connected to the second wiring electrode 52 via an electrode that penetrates the piezoelectric layer 20. In the elastic wave device 10H according to the eighth embodiment, there is an intersection region CA in a plan view in the Z direction where the upper electrode 35 and the lower electrode 36 overlap. In other words, the piezoelectric layer 20 in the intersection region CA is sandwiched between the upper electrode 35 and the lower electrode 36. As a result, bulk waves propagate in the intersection region CA between the upper electrode 35 and the lower electrode 36. Note that in the example shown in Figure 23, the shapes of the upper electrode 35 and the lower electrode 36 are rectangular, but this is merely one example.

[0105] It should be noted that the elastic wave apparatus according to the eighth embodiment is not limited to the elastic wave apparatus 10H described above. For example, the functional electrode is not limited to having both an upper electrode and a lower electrode, but may be provided on either the upper or lower side of the piezoelectric layer 20.

[0106] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit its interpretation. The present invention may be modified or improved without departing from its spirit, and equivalents thereof are also included.

[0107] Furthermore, the invention relating to this disclosure may also take the following forms. <1> An elastic wave apparatus comprising: a support member having a support substrate and an acoustic multilayer film; a piezoelectric layer provided on the upper side of the acoustic multilayer film and having thickness in a first direction; a functional electrode provided on the upper side of the acoustic multilayer film and provided on at least one of the upper and lower sides of the piezoelectric layer; a first electrode provided on the upper side of the acoustic multilayer film and provided on at least one of the upper and lower sides of the piezoelectric layer and having a first potential; a second electrode provided on the upper side of the acoustic multilayer film and provided on at least one of the upper and lower sides of the piezoelectric layer and having a second potential different from the first potential; and a protective portion provided on the upper side of the support substrate, wherein the acoustic multilayer film includes a high acoustic impedance layer with relatively high acoustic impedance and a low acoustic impedance layer with relatively low acoustic impedance; the first electrode and the second electrode are adjacent to each other; when viewed from the first direction in plan, there is a non-piezoelectric region between the first electrode and the second electrode where the piezoelectric layer is not provided; and in the non-piezoelectric region, the protective portion covers the surface of at least one layer of the low acoustic impedance layer. <2> The elastic wave apparatus according to <1>, wherein the upper surface of the acoustic multilayer film in the non-piezoelectric region has the main surface of the at least one low acoustic impedance layer, and in the non-piezoelectric region, the protective portion covers the main surface of the at least one low acoustic impedance layer. <3> The elastic wave apparatus according to <1> or <2>, wherein the non-piezoelectric region has the side surface of the at least one low acoustic impedance layer, and in the non-piezoelectric region, the protective portion covers the side surface of the at least one low acoustic impedance layer. <4> The elastic wave apparatus according to <3>, wherein the protective portion is in contact with the support substrate in the non-piezoelectric region. <5> The elastic wave apparatus according to <4>, wherein the protective portion has a conductor layer.<6> The elastic wave apparatus according to <5>, wherein the protective portion includes a first conductor layer and a second conductor layer, the first conductor layer extending in the first direction from the first electrode to the support substrate, the second conductor layer extending in the first direction from the second electrode to the support substrate, and in the non-piezoelectric region, the first conductor layer and the second conductor layer are not in contact with each other. <7> The elastic wave apparatus according to <5> or <6>, wherein the protective portion further includes a dielectric layer provided between the conductor layer and the support substrate. <8> The elastic wave apparatus according to any one of <1> to <7>, comprising a plurality of resonators connected in parallel with each other, wherein there is no non-piezoelectric region between the resonators connected in parallel with each other. <9> The elastic wave apparatus according to any one of <1> to <8>, wherein, when viewed in plan in the first direction, the outer surface of the piezoelectric layer is located inside the outer surface of the support substrate, and when viewed in plan in the first direction, the protective portion is provided to cover the surface of the at least one layer of the low acoustic impedance layer in the region between the outer surface of the piezoelectric layer and the outer surface of the support substrate. <10> The elastic wave apparatus according to any one of <1> to <9>, wherein the at least one layer of the low acoustic impedance layer contains silicon oxide. <11> The elastic wave apparatus according to any one of <1> to <10>, wherein the protective portion contains at least one of nitrides, carbides, polymer compounds and metals. <12> The elastic wave apparatus according to <11>, wherein the protective portion contains at least one of silicon nitride, silicon carbide and gold. <13> The elastic wave apparatus according to any one of <1> to <12>, wherein the protective portion is made of a material with a higher thermal conductivity than the piezoelectric layer. <14> The elastic wave apparatus according to any one of <1> to <13>, wherein the support member further comprises an intermediate layer provided between the support substrate and the acoustic multilayer film. <15> The elastic wave apparatus according to any one of <1> to <14>, wherein the functional electrode is an IDT electrode including a plurality of electrode fingers arranged in a predetermined direction, and when the thickness of the piezoelectric layer is d and the distance between the centers of adjacent electrode fingers is p, d / p is 0.5 or less. <16> The elastic wave apparatus according to <15>, wherein d / p is 0.24 or less.<17> The elastic wave apparatus according to <15> or <16>, wherein, when viewed from a direction perpendicular to the longitudinal direction of the electrode finger, the region in which adjacent electrode fingers overlap, and the region between the centers of adjacent electrode fingers in a direction perpendicular to the longitudinal direction of the electrode finger, is defined as the excitation region, and when the metallization ratio of the electrode finger with respect to the excitation region is MR, the condition MR ≤ 1.75 (d / p) + 0.075 is satisfied. <18> The elastic wave apparatus according to any one of <15> to <17>, wherein the piezoelectric layer is made of lithium tantalate or lithium niobate. <19> The elastic wave apparatus according to <18>, wherein the Euler angle (φ, θ, ψ) of the lithium niobate or lithium tantalate constituting the piezoelectric layer is 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°) ...Formula (2) (0°±10°, [180°-30°(1-(ψ-90) ２ ( / 8100) １／２ ] ~180°, any ψ) ...Equation (3) <20> The elastic wave apparatus according to any one of <1> to <14>, wherein the functional electrode includes a flat plate electrode provided on at least one of the upper and lower sides of the piezoelectric layer.

[0108] 10, 10A Elastic wave device 11 Support substrate 12 Intermediate layer 20 Piezoelectric layer 30 Functional electrode 31, 32 Electrode fingers 33 First busbar electrode 34 Second busbar electrode 35 Upper electrode 36 Lower electrode 43 Acoustic multilayer film 51 First wiring electrode 52 Second wiring electrode 60, 70 Protective part

Claims

1. An elastic wave apparatus comprising: a support member having a support substrate and an acoustic multilayer film; a piezoelectric layer provided on the upper side of the acoustic multilayer film and having thickness in a first direction; a functional electrode provided on the upper side of the acoustic multilayer film and provided on at least one of the upper and lower sides of the piezoelectric layer; a first electrode provided on the upper side of the acoustic multilayer film and provided on at least one of the upper and lower sides of the piezoelectric layer and having a first potential; a second electrode provided on the upper side of the acoustic multilayer film and provided on at least one of the upper and lower sides of the piezoelectric layer and having a second potential different from the first potential; and a protective portion provided on the upper side of the support substrate, wherein the acoustic multilayer film includes a high acoustic impedance layer with relatively high acoustic impedance and a low acoustic impedance layer with relatively low acoustic impedance; the first electrode and the second electrode are adjacent to each other; when viewed from the first direction in plan, there is a non-piezoelectric region between the first electrode and the second electrode where the piezoelectric layer is not provided; and in the non-piezoelectric region, the protective portion covers the surface of at least one layer of the low acoustic impedance layer.

2. The acoustic wave apparatus according to claim 1, wherein the upper surface of the acoustic multilayer film in the non-piezoelectric region has the main surface of the at least one low acoustic impedance layer, and in the non-piezoelectric region, the protective portion covers the main surface of the at least one low acoustic impedance layer.

3. The elastic wave apparatus according to claim 1 or 2, wherein the non-piezoelectric region has at least one low acoustic impedance side surface, and in the non-piezoelectric region, the protective portion covers the side surface of the at least one low acoustic impedance layer.

4. The elastic wave apparatus according to claim 3, wherein in the non-piezoelectric region, the protective portion is in contact with the support substrate.

5. The elastic wave apparatus according to claim 4, wherein the protective portion has a conductive layer.

6. The elastic wave apparatus according to claim 5, wherein the protective portion includes a first conductor layer and a second conductor layer, the first conductor layer extends in a first direction from the first electrode to the support substrate, the second conductor layer extends in a first direction from the second electrode to the support substrate, and in the non-piezoelectric region, the first conductor layer and the second conductor layer are not in contact with each other.

7. The elastic wave apparatus according to claim 5 or 6, wherein the protective portion further comprises a dielectric layer provided between the conductor layer and the support substrate.

8. An elastic wave apparatus comprising a plurality of resonators connected in parallel with each other, wherein there is no non-piezoelectric region between the resonators connected in parallel with each other, according to any one of claims 1 to 7.

9. The acoustic wave apparatus according to any one of claims 1 to 8, wherein, when viewed in plan in the first direction, the outer surface of the piezoelectric layer is located inside the outer surface of the support substrate, and when viewed in plan in the first direction, the protective portion is provided to cover the surface of the at least one layer of the low acoustic impedance layer in the region between the outer surface of the piezoelectric layer and the outer surface of the support substrate.

10. The elastic wave apparatus according to any one of claims 1 to 9, wherein the at least one low acoustic impedance layer comprises silicon oxide.

11. The elastic wave apparatus according to any one of claims 1 to 10, wherein the protective part comprises at least one of nitrides, carbides, polymer compounds, and metals.

12. The elastic wave apparatus according to claim 11, wherein the protective part includes at least one of silicon nitride, silicon carbide, and gold.

13. The elastic wave apparatus according to any one of claims 1 to 12, wherein the protective portion is made of a material with a higher thermal conductivity than the piezoelectric layer.

14. The elastic wave apparatus according to any one of claims 1 to 13, wherein the support member further comprises an intermediate layer provided between the support substrate and the acoustic multilayer film.

15. The elastic wave apparatus according to any one of claims 1 to 14, wherein the functional electrode is an IDT electrode including a plurality of electrode fingers arranged in a predetermined direction, and when the thickness of the piezoelectric layer is d and the distance between the centers of adjacent electrode fingers is p, d / p is 0.5 or less.

16. The elastic wave apparatus according to claim 15, wherein the d / p is 0.24 or less.

17. The elastic wave apparatus according to claim 15 or 16, wherein, when viewed from a direction perpendicular to the longitudinal direction of the electrode fingers, the region in which adjacent electrode fingers overlap, and the region between the centers of adjacent electrode fingers in a direction perpendicular to the longitudinal direction of the electrode fingers, is defined as the excitation region, and when the metallization ratio of the electrode fingers with respect to the excitation region is denoted as MR, the condition MR ≤ 1.75 (d / p) + 0.075 is satisfied.

18. The elastic wave apparatus according to any one of claims 15 to 17, wherein the piezoelectric layer is made of lithium tantalate or lithium niobate.

19. The elastic wave apparatus according to claim 18, wherein the Euler angles (φ, θ, ψ) of the lithium niobate or lithium tantalate constituting the piezoelectric layer are within the range of the following equations (1), (2), or (3): (0°±10°, 0° to 20°, any ψ) ...Equation (1) (0°±10°, 20° to 80°, 0° to 60° (1 - (θ - 50)) ２ / 900) １／２ ) or (0°±10°, 20°~80°, [180°-60°(1-(θ-50) ２ / 900) １／２ ]~180°) ...Formula (2) (0°±10°, [180°-30°(1-(ψ-90) ２ ( / 8100) １／２ ] ~180°, any ψ) ...Equation (3) 20. The elastic wave apparatus according to any one of claims 1 to 14, wherein the functional electrode includes a flat plate-shaped electrode provided on at least one of the upper and lower sides of the piezoelectric layer.

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