Elastic wave device and elastic wave filter device

Abstract

This elastic wave device comprises: a piezoelectric layer having a first main surface and a second main surface facing the first main surface in a first direction; an IDT electrode provided on at least one of the first main surface and the second main surface of the piezoelectric layer and including a plurality of electrode fingers arrayed in a predetermined direction; a support member facing the second main surface of the piezoelectric layer and having an acoustic reflection part on the second main surface side of the piezoelectric layer; and a load film provided in a region overlapping with at least one end part in the array direction of the plurality of electrode fingers of the IDT electrode in a plan view. The end part includes a first electrode finger positioned on the outermost side in the array direction of the plurality of electrode fingers. 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.

Description

Acoustic wave device and acoustic wave filter device

[0001] The present invention relates to an acoustic wave device and an acoustic wave filter device.

[0002] Patent Documents 1 and 2 describe acoustic wave devices.

[0003] JP-T-2022-524136 Publication U.S. Pat. No. 11,349,450

[0004] The acoustic wave devices disclosed in Patent Documents 1 and 2 have the possibility of acoustic wave leakage occurring in the arrangement direction of the electrode fingers.

[0005] An object of the present invention is to provide an acoustic wave device and an acoustic wave filter device that can suppress leakage of acoustic waves.

[0006] An elastic wave device according to one embodiment includes a piezoelectric layer having a first main surface and a second main surface opposite the first main surface in a first direction; an IDT electrode provided on at least one of the first and second main surfaces of the piezoelectric layer and including a plurality of electrode fingers arranged in a predetermined direction; a support member facing the second main surface of the piezoelectric layer and having an acoustic reflector on the second main surface side of the piezoelectric layer; and a load film provided in a region that overlaps, in a planar view from the first direction, at least one end of the IDT electrode in the arrangement direction of the plurality of electrode fingers, wherein the end includes a first electrode finger that is located outermost in the arrangement direction of the plurality of electrode fingers, and wherein d / p is 0.5 or less, where d is the thickness of the piezoelectric layer and p is the center-to-center distance between adjacent electrode fingers.

[0007] an IDT electrode provided on the first main surface of the piezoelectric layer and including a plurality of electrode fingers arranged in a predetermined direction; a support member facing the second main surface of the piezoelectric layer; a protective film provided on at least one of the first main surface and the second main surface of the piezoelectric layer; and a load film provided in a region that is outward of a first electrode finger that is positioned outermost in an arrangement direction of the plurality of electrode fingers and does not overlap with the IDT electrode, wherein, where d is a thickness of the piezoelectric layer and p is a center-to-center distance between adjacent electrode fingers, d / p is 0.5 or less, and where L is a distance between the first electrode finger and the load film in a planar view and L is a distance between the first electrode finger and the load film in the arrangement direction of the plurality of electrode fingers, L / p is 0.9 or less.

[0008] An acoustic wave filter device according to one aspect is an acoustic wave filter device including at least one resonator connected thereto, the resonator being the acoustic wave device described above.

[0009] According to the acoustic wave device and the acoustic wave filter device of the present invention, leakage of acoustic waves can be suppressed.

[0010] FIG. 1 is a plan view of an elastic wave device according to a first embodiment. FIG. 2 is a cross-sectional view taken along line II-II′ of FIG. 1 . FIG. 3 is a schematic cross-sectional view illustrating a bulk wave in a first-order thickness-shear mode propagating through a piezoelectric layer according to the first embodiment. FIG. 4 is a schematic cross-sectional view illustrating the amplitude direction of a bulk wave in a first-order thickness-shear mode propagating through a piezoelectric layer according to the first embodiment. FIG. 5 is a diagram illustrating an example of the resonance characteristics of the elastic wave device according to the first embodiment. FIG. 6 is a diagram illustrating the relationship between d / 2p and the fractional bandwidth of a resonator, where p is the center-to-center distance or the average center-to-center distance between adjacent electrodes and d is the average thickness of the piezoelectric layer in the elastic wave device according to the first embodiment. FIG. 7 is a plan view illustrating an example of the elastic wave device according to the first embodiment, in which a pair of electrodes is provided. FIG. 8 is a reference diagram illustrating an example of the resonance characteristics of the elastic wave device according to the first embodiment. 9 is a diagram illustrating the relationship between the relative bandwidth when a large number of elastic wave resonators are configured in the elastic wave device according to the first embodiment and the amount of phase rotation of the spurious impedance normalized by 180 degrees as the magnitude of the spurious. FIG. 10 is a diagram illustrating the relationship between d / 2p, the metallization ratio MR, and the relative bandwidth. FIG. 11 is a diagram illustrating the relationship between d / p and the metallization ratio MR of LiNbO when d / p approaches 0. ３FIG. 12 is an explanatory diagram illustrating a map of the fractional bandwidth versus Euler angles (0°, θ, ψ) of the elastic wave device according to the first embodiment. FIG. 13 is an explanatory diagram illustrating an example of the admittance characteristics of an elastic wave device according to a first modification of the first embodiment. FIG. 14 is an explanatory diagram illustrating an example of the admittance characteristics of an elastic wave device according to a first modification of the first embodiment. FIG. 15 is an explanatory diagram illustrating an example of the admittance characteristics of an elastic wave device according to a second modification of the first embodiment. FIG. 16 is an explanatory diagram illustrating an example of the admittance characteristics of an elastic wave device according to a third modification of the first embodiment. FIG. 17 is a cross-sectional diagram illustrating an elastic wave device according to a fourth modification of the first embodiment. FIG. 18 is an explanatory diagram illustrating an example of the admittance characteristics of an elastic wave device according to a fourth modification of the first embodiment. FIG. 19 is a cross-sectional diagram illustrating an elastic wave device according to a fifth modification of the first embodiment. FIG. 20 is an explanatory diagram illustrating the relationship between the number of electrode fingers overlapping with the load film and the phase in elastic wave devices according to the fourth and fifth modifications of the first embodiment. FIG. 21 is a cross-sectional view of an elastic wave device according to a sixth modified example of the first embodiment. FIG. 22 is an explanatory diagram illustrating an example of admittance characteristics of an elastic wave device according to a sixth modified example of the first embodiment. FIG. 23 is a cross-sectional view of an elastic wave device according to a seventh modified example of the first embodiment. FIG. 24 is an explanatory diagram illustrating an example of admittance characteristics of an elastic wave device according to a seventh modified example of the first embodiment. FIG. 25 is a cross-sectional view of an elastic wave device according to a second embodiment. FIG. 26 is an explanatory diagram illustrating an example of admittance characteristics of an elastic wave device according to the second embodiment. FIG. 27 is a cross-sectional view of an elastic wave device according to a third embodiment. FIG. 28 is an explanatory diagram illustrating an example of admittance characteristics of an elastic wave device according to the third embodiment. FIG. 29 is an explanatory diagram illustrating the distribution of vibration modes of an elastic wave device according to the third embodiment. FIG. 30 is an explanatory diagram illustrating the distribution of vibration modes of an elastic wave device according to a comparative example. FIG. 31 is a cross-sectional view of an elastic wave device according to an eighth modified example of the third embodiment. FIG. 32 is an explanatory diagram illustrating an example of admittance characteristics of an elastic wave device according to the eighth modified example of the third embodiment. Fig. 33 is a cross-sectional view illustrating an elastic wave device according to a ninth modified example of Embodiment 3. Fig. 34 is a diagram illustrating an example of admittance characteristics of an elastic wave device according to a ninth modified example of Embodiment 3.FIG. 35 is a diagram illustrating an example of the admittance characteristics of an elastic wave device according to a tenth modified example of the third embodiment. FIG. 36 is a cross-sectional view of an elastic wave device according to an eleventh modified example of the third embodiment. FIG. 37 is a diagram illustrating an example of the admittance characteristics of an elastic wave device according to an eleventh modified example of the third embodiment. FIG. 38 is a diagram illustrating the relationship between the phase of a spurious signal and the Young's modulus of a load film in an elastic wave device according to a twelfth modified example of the third embodiment. FIG. 39 is a diagram illustrating an example of the impedance characteristics of an elastic wave device according to the third embodiment. FIG. 40 is a cross-sectional view of an elastic wave device according to the fourth embodiment. FIG. 41 is a diagram illustrating an example of the admittance characteristics of an elastic wave device according to the fourth embodiment. FIG. 42 is a cross-sectional view of an elastic wave device according to the fifth embodiment. FIG. 43 is a diagram illustrating an example of the admittance characteristics of an elastic wave device according to the fifth embodiment. FIG. 44 is a diagram illustrating an example of the admittance characteristics of an elastic wave device according to a thirteenth modified example of the fifth embodiment. FIG. 45 is a diagram illustrating an example of the admittance characteristics of an elastic wave device according to a fourteenth modified example of the fifth embodiment. FIG. 46 is a cross-sectional view of an elastic wave device according to a fifteenth modified example of the fifth embodiment. FIG. 47 is a diagram illustrating an example of the admittance characteristics of an elastic wave device according to a fifteenth modified example of the fifth embodiment. FIG. 48 is a diagram illustrating an example of the admittance characteristics of an elastic wave device according to a sixteenth modified example of the fifth embodiment. FIG. 49 is a diagram illustrating an example of the admittance characteristics of an elastic wave device according to a seventeenth modified example of the fifth embodiment. FIG. 50 is a cross-sectional view of an elastic wave device according to the sixth embodiment. FIG. 51 is a diagram illustrating an example of the admittance characteristics of an elastic wave device according to the sixth modified example. FIG. 52 is a diagram illustrating an example of the admittance characteristics of an elastic wave device according to an eighteenth modified example of the sixth embodiment. FIG. 53 is a diagram illustrating an example of the admittance characteristics of an elastic wave device according to a nineteenth modified example of the sixth embodiment. FIG. 54 is a cross-sectional view of an elastic wave device according to a twentieth modified example of the sixth embodiment. FIG. 55 is a diagram illustrating an example of the admittance characteristics of an elastic wave device according to the twentieth modified example of the sixth embodiment. FIG. 56 is a cross-sectional view of an elastic wave device according to the seventh embodiment. FIG. 57 is a diagram illustrating an example of admittance characteristics of an elastic wave device according to a seventh embodiment.FIG. 58 is an explanatory diagram showing the relationship between the distance between the load film and the first electrode fingers and the admittance in an elastic wave device according to a seventh preferred embodiment. FIG. 59 is a plan view of an elastic wave device according to an eighth preferred embodiment. FIG. 60 is a plan view of an elastic wave device according to a twenty-first modified example of the eighth preferred embodiment. FIG. 61 is a plan view of an elastic wave device according to a twenty-second modified example of the eighth preferred embodiment. FIG. 62 is a circuit diagram of an elastic wave device according to a ninth preferred embodiment. FIG. 63 is a cross-sectional view of an elastic wave device according to a twenty-third modified example. FIG. 64 is a cross-sectional view of an elastic wave device according to a twenty-fourth modified example. FIG. 65 is a cross-sectional view of an elastic wave device according to a twenty-fifth modified example. FIG. 66 is an explanatory diagram showing an example of the admittance characteristics of an elastic wave device according to a twenty-fifth modified example. FIG. 67 is a cross-sectional view of an elastic wave device according to a twenty-sixth modified example. FIG. 68 is an explanatory diagram showing an example of the admittance characteristics of an elastic wave device according to a twenty-sixth modified example. FIG. 69 is an explanatory diagram showing an example of the admittance characteristics of an elastic wave device according to a twenty-seventh modified example. FIG. 70 is an explanatory diagram showing an example of impedance phase in a higher mode. FIG. 71 is a cross-sectional view of an elastic wave device according to a 28th modification. FIG. 72 is an explanatory diagram showing the relationship between the amount of movement of the load film and admittance in an elastic wave device according to the 28th modification. FIG. 73 is a plan view of an elastic wave device according to a 29th modification. FIG. 74 is an explanatory diagram showing example impedance characteristics of an elastic wave device according to the 29th modification. FIG. 75 is an explanatory diagram showing an enlarged view of dotted line H1 in FIG. 74. FIG. 76 is a plan view of an elastic wave device according to a 30th modification. FIG. 77 is a plan view of an elastic wave device according to a 31st modification. FIG. 78 is a plan view of an elastic wave device according to a 32nd modification. FIG. 79 is a plan view of an elastic wave device according to a 33rd modification. FIG. 80 is a cross-sectional view taken along line LXXX-LXXX′ in FIG. 79. FIG. 81 is a cross-sectional view of an elastic wave device according to a 34th modification. FIG. 82 is a cross-sectional view showing an enlarged portion of FIG. 81. Fig. 83 is an explanatory diagram showing an example of admittance characteristics of an elastic wave device according to a thirty-fourth modification. Fig. 84 is an explanatory diagram showing an example of admittance characteristics of an elastic wave device according to a thirty-fifth modification. Fig. 85 is a plan view showing an elastic wave device according to a thirty-sixth modification. Fig. 86 is a plan view showing an elastic wave device according to a thirty-seventh modification.87 and 88 are plan views illustrating elastic wave devices according to thirty-eighth and thirty-ninth modifications.

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. However, the present disclosure is not limited to these embodiments. Note that each embodiment described in the present disclosure is an example, and in the second and subsequent embodiments, a description of modifications in which partial substitution or combination of configurations is possible between different embodiments, and of matters common to the first embodiment will be omitted, and only differences will be described. In particular, similar effects resulting from similar configurations will not be mentioned in each embodiment.

[0012] First Embodiment Fig. 1 is a plan view showing an elastic wave device according to a first embodiment. Fig. 2 is a cross-sectional view taken along line II-II' in Fig. 1. Note that in Fig. 1, the load film 50 is shown hatched to make the drawing easier to read. Also, in Fig. 1, the first protective film 41 is shown by a two-dot chain line.

[0013] 1 and 2 , an elastic wave device 10 according to the first embodiment includes a piezoelectric layer 20, an IDT electrode 30, a support substrate 11, a first protective film 41, a second protective film 42, and a load film 50. As shown in Fig. 2 , the elastic wave device 10 includes the second protective film 42, the piezoelectric layer 20, the IDT electrode 30, the first protective film 41, and the load film 50 stacked in this order on the support substrate 11.

[0014] The piezoelectric layer 20 is in the form of a flat plate 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 Alternatively, the piezoelectric layer 20 may be made of lithium tantalate (LiTaO ３ ) may be made of LiNbO ３ and LiTaO ３ In the first embodiment, the cut angle is a Z-cut. ３ and LiTaO ３ The cut angle may be a rotated Y cut or an X cut. Preferably, the propagation direction is Y propagation or X propagation ±30°. Preferably, the piezoelectric layer 20 is made of lithium niobate (LiNbO ３) or lithium tantalate (LiTaO ３ ) and is a 120°±10° rotated Y-cut or a 90°±10° rotated Y-cut.

[0015] The thickness of the piezoelectric layer 20 is not particularly limited, but is preferably 50 nm to 1000 nm inclusive in order to effectively excite the first-order thickness shear mode. The thickness of the piezoelectric layer 20 according to the first embodiment is, for example, approximately 180 nm.

[0016] The IDT (Interdigital Transducer) electrode 30 is provided on the first main surface 20a of the piezoelectric layer 20. As shown in FIG. 1 , the IDT electrode 30 has electrode fingers 31 and 32 and busbar electrodes 33 and 34. The plurality of electrode fingers 31 extend in the Y direction, and one end side in the extension direction is connected to the busbar electrode 33. The plurality of electrode fingers 32 extend in the Y direction, and the other end side in the extension direction is connected to the busbar electrode 34. The plurality of electrode fingers 31 and the plurality of electrode fingers 32 are arranged alternately in the X direction with a gap therebetween. The busbar electrodes 33 and 34 each extend in the X direction and are spaced apart in the Y direction. The plurality of electrode fingers 31 and 32 are arranged between the busbar electrode 33 and the busbar electrode 34.

[0017] 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 positional relationship when viewed from a direction perpendicular to the first main surface 20 a of the piezoelectric layer 20.

[0018] The center-to-center distance between the electrode fingers 31 and 32 (hereinafter referred to as the inter-electrode pitch) is preferably in the range of 1 μm to 10 μm. The inter-electrode pitch is the distance between the center of the width of the electrode finger 31 in a direction perpendicular to the extension direction of the electrode fingers 31 and the center of the width of the electrode finger 32 in a direction perpendicular to the extension direction of the electrode fingers 32. The width of the electrode fingers 31 and 32 (hereinafter referred to as the electrode width), i.e., the dimension in the direction perpendicular to the extension direction of the electrode fingers 31 and 32, is preferably in the range of 150 nm to 1000 nm.

[0019] Furthermore, when there are multiple electrode fingers 31 and multiple electrode fingers 32 (when the electrode fingers 31 and the electrode fingers 32 are considered as a pair of electrode sets, there are 1.5 or more pairs of electrode sets), the inter-electrode pitch of the electrode fingers 31 and the electrode fingers 32 refers to the average value of the center-to-center distances of adjacent electrode fingers 31 and electrode fingers 32 among the 1.5 or more pairs of electrode fingers 31 and electrode fingers 32.

[0020] Furthermore, in the first embodiment, since a Z-cut piezoelectric layer is used, the direction perpendicular to the extension direction of the 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 (the angle between the direction perpendicular to the extension direction of the electrode fingers 31 and 32 and the polarization direction is, for example, 90°±10°).

[0021] The IDT electrode 30 (electrode fingers 31, 32 and busbar electrodes 33, 34) is made of an appropriate metal or alloy such as Al or an AlCu alloy. In the first embodiment, the IDT electrode 30 has a structure in which an Al film is laminated on a titanium (Ti) film. Note that an adhesive layer other than the Ti film may also be used.

[0022] More specifically, the IDT electrode 30 has a laminated structure of Ti / AlCu / Ti / AlCu, with respective film thicknesses of 12 nm / 70 nm / 18 nm / 12 nm from the piezoelectric layer 20 side. The IDT electrode 30 has a total of 51 electrode fingers 31 and 32. The interelectrode pitch of the electrode fingers 31 and 32 is 2.38 μm, and the electrode width of each is 0.6 μm.

[0023] 1 is a region where the electrode fingers 31 and 32 overlap when viewed in the X direction. The length of the intersection region C is the dimension in the extension direction of the electrode fingers 31 and 32 in the intersection region C. In this embodiment, the length of the intersection region C is, for example, 40 μm.

[0024] During operation, an AC voltage is applied between the plurality of electrode fingers 31 and the plurality of electrode fingers 32. More specifically, an AC voltage is applied between the bus bar electrode 33 and the bus bar electrode 34. This makes it possible to obtain resonance characteristics using bulk waves in the first thickness-shear mode excited in the piezoelectric layer 20.

[0025] Furthermore, in elastic wave device 10, where d is the thickness of piezoelectric layer 20 and p is the inter-electrode pitch between pairs of electrode fingers 31 and 32, d / p is set to 0.5 or less. This effectively excites the bulk waves in the thickness-shear first-order mode, resulting in good resonance characteristics. More preferably, d / p is set to 0.24 or less, which results in even better resonance characteristics.

[0026] Because the elastic wave device 10 of the first embodiment has the above configuration, even if the number of pairs of electrode fingers 31 and 32 is reduced in an attempt to reduce the device size, the Q value is unlikely to decrease. This is because the resonator does not require reflectors on both sides, resulting in low propagation loss. Furthermore, the reason why the reflectors are not required is because the device utilizes bulk waves in the thickness-shear first-order mode.

[0027] The first protective film 41 is provided on the first main surface 20a of the piezoelectric layer 20, covering the IDT electrode 30. The second protective film 42 is provided on the second main surface 20b of the piezoelectric layer 20. The first protective film 41 and the second protective film 42 are made of silicon oxide (SiO ２ ). The first protective film 41 and the second protective film 42 can be made of an appropriate insulating material such as silicon oxide, silicon nitride, or alumina. The film thickness of the first protective film 41 and the second protective film 42 is greater than the film thickness of the IDT electrode 30. The film thickness of the first protective film 41 and the second protective film 42 is 142 nm. It is sufficient that at least one of the first protective film 41 and the second protective film 42 is provided. For example, a configuration in which the first protective film 41 is provided and the second protective film 42 is not provided may also be used.

[0028] The load film 50 is provided on the first protective film 41. The load film 50 is provided in a region overlapping with the outermost electrode finger 31 (hereinafter referred to as the first electrode finger 31 a) of the plurality of electrode fingers 31, 32 in the arrangement direction of the plurality of electrode fingers 31, 32. The load film 50 is also provided in a region overlapping with the outermost electrode finger 32 (hereinafter referred to as the second electrode finger 32 a) on the side opposite to the first electrode finger 31 a.

[0029] A portion of the load film 50 overlapping with the first electrode finger 31 a is referred to as a first extension portion 51, and a portion overlapping with the second electrode finger 32 a is referred to as a second extension portion 52. The first extension portion 51 and the second extension portion 52 are spaced apart in the arrangement direction of the multiple electrode fingers 31, 32, and the multiple electrode fingers 31, 32 are arranged between the first extension portion 51 and the second extension portion 52. The first extension portion 51 overlaps with a portion of the first electrode finger 31 a and extends in the extension direction of the first electrode finger 31 a. The second extension portion 52 overlaps with a portion of the second electrode finger 32 a and extends in the extension direction of the second electrode finger 32 a. The detailed configuration of the load film 50 will be described later with reference to FIGS. 12 and 13 .

[0030] The support substrate 11 (support member) is disposed opposite the second main surface 20b of the piezoelectric layer 20. The support substrate 11 has a cavity 14 (space) on the surface facing the second main surface 20b of the piezoelectric layer 20. More specifically, the support substrate 11 has a bottom 12 and a wall 13 provided in a frame shape on the upper surface of the bottom 12. The cavity 14 is formed in the space surrounded by the bottom 12 and the wall 13. The piezoelectric layer 20 is stacked on the upper surface of the wall 13 of the support substrate 11 with a second protective film 42 interposed therebetween. In this manner, the acoustic wave device 10 has a so-called membrane structure in which the cavity 14 (hollow portion) is provided on the second main surface 20b side of the piezoelectric layer 20. The support member may include the support substrate 11 and an intermediate (insulating) layer. That is, the support substrate 11 may be stacked indirectly on the second main surface 2b of the piezoelectric layer 2. In this case, the support substrate 11 and the intermediate layer may have a frame-like shape, thereby forming the cavity portion 14. Alternatively, a recess may be provided in the intermediate layer, thereby forming the cavity portion 14.

[0031] The cavity 14 is provided so as not to interfere with vibration of the intersection region C of the piezoelectric layer 20. The second protective film 42 is provided to cover the opening of the cavity 14. However, as described above, the second protective film 42 does not have to be provided. In this case, the support substrate 11 can be stacked directly on the second main surface 20b of the piezoelectric layer 20. Alternatively, the second protective film 42 may be provided in the region between the upper surface of the wall 13 and the second main surface 20b of the piezoelectric layer 20, and not in the region overlapping with the cavity 14.

[0032] The support substrate 11 is made of silicon (Si). The surface of the Si facing the piezoelectric layer 20 may have a (100), (110), or (111) plane orientation. Preferably, Si has a high resistivity of 4 kΩ or more. However, the support substrate 11 may also be made of an appropriate insulating material or semiconductor material. Examples of materials that can be used 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; dielectric materials such as diamond and glass; and semiconductors such as gallium nitride.

[0033] 3 and 4 are schematic cross-sectional views illustrating a bulk wave in a first-order thickness-shear mode propagating through the piezoelectric layer of the first embodiment, respectively.

[0034] As shown in FIG. 3 , in the elastic wave device 10 of the first embodiment, vibration displacement occurs in the thickness shear direction. Therefore, waves propagate and resonate substantially in the direction connecting the first principal surface 20 a and the second principal surface 20 b of the piezoelectric layer 20, i.e., the Z direction. That is, the X direction component of the wave is significantly smaller than the Z direction component. Furthermore, since resonance characteristics are achieved through wave propagation in this Z direction, a reflector is not required. Therefore, no propagation loss occurs during propagation to the reflector. Therefore, even if the number of electrode pairs, each consisting of electrode fingers 31 and 32, is reduced in an effort to achieve miniaturization, the Q value is unlikely to decrease.

[0035] As shown in FIG. 4 , the amplitude direction of the bulk wave in the first thickness-shear mode is opposite between a first region 251 included in the intersection region C (see FIG. 1 ) of the piezoelectric layer 20 and a second region 252 included in the intersection region C. FIG. 4 schematically illustrates the bulk wave when a voltage is applied between the electrode fingers 31 and 32 such that the electrode finger 32 has a higher potential than the electrode finger 31. Here, the imaginary plane VP1 is a plane that is perpendicular to the thickness direction of the piezoelectric layer 20 and divides the piezoelectric layer 20 in half. The first region 251 is the region of the intersection region C between the imaginary plane VP1 and the first main surface 20a. The second region 252 is the region of the intersection region C between the imaginary plane VP1 and the second main surface 20b.

[0036] In acoustic wave device 10, at least one pair of electrodes consisting of electrode finger 31 and electrode finger 32 is arranged, but because waves are not propagated in the X direction, the number of electrode pairs consisting of electrode finger 31 and electrode finger 32 does not necessarily need to be multiple. In other words, it is sufficient that at least one pair of electrodes is provided.

[0037] For example, the electrode finger 31 is an electrode connected to a hot potential, and the electrode finger 32 is an electrode connected to a ground potential. However, the electrode finger 31 may be connected to the ground potential, and the electrode finger 32 may be connected to the hot potential. In the first embodiment, at least one pair of electrodes is an electrode connected to a hot potential or an electrode connected to a ground potential, as described above, and no floating electrode is provided.

[0038] 5 is a diagram illustrating an example of the resonance characteristics of the elastic wave device according to the first embodiment. The design parameters of the elastic wave device 10 that achieved the resonance characteristics shown in FIG.

[0039] Piezoelectric layer 20: LiNbO with Euler angles (0°, 0°, 90°) ３ Thickness of the piezoelectric layer 20: 400 nm

[0040] Length of the crossing region C: 40 μm Number of pairs of electrodes consisting of the electrode fingers 31 and 32: 21 pairs Inter-electrode pitch between the electrode fingers 31 and 32: 3 μm Width of the electrode fingers 31 and 32: 500 nm d / p: 0.133

[0041] First protective film 41, second protective film 42: silicon oxide film with a thickness of 1 μm

[0042] Support substrate 11: Si

[0043] In the first embodiment, the inter-electrode pitch of each of the electrode pairs, each consisting of the electrode finger 31 and the electrode finger 32, is set to be equal in all pairs. That is, the electrode fingers 31 and the electrode fingers 32 are arranged at equal pitches.

[0044] As is clear from FIG. 5, good resonance characteristics with a relative bandwidth of 12.5% ​​are obtained despite the absence of a reflector.

[0045] In the first embodiment, when the thickness of the piezoelectric layer 20 is d and the interelectrode pitch between the electrode fingers 31 and 32 is p, d / p is 0.5 or less, and more preferably 0.24 or less. This will be explained with reference to FIG. 6.

[0046] 6 is an explanatory diagram showing the relationship between d / 2p and the fractional bandwidth of a resonator in the elastic wave device according to the first embodiment, where p is the center-to-center distance or the average center-to-center distance between adjacent electrodes and d is the average thickness of the piezoelectric layer. In FIG. 6, multiple elastic wave devices were obtained by varying d / 2p, similar to the elastic wave device having the resonance characteristics shown in FIG.

[0047] As shown in Figure 6, when d / 2p exceeds 0.25, i.e., when d / p > 0.5, adjusting d / p results in a fractional bandwidth of less than 5%. In contrast, when d / 2p ≤ 0.25, i.e., when d / p ≤ 0.5, varying d / p within this range can increase the fractional bandwidth to 5% or more, thereby enabling the construction of a resonator with a high coupling coefficient. Furthermore, when d / 2p is 0.12 or less, i.e., when d / p is 0.24 or less, the fractional bandwidth can be increased to 7% or more. Furthermore, adjusting d / p within this range can result in a resonator with a wider fractional bandwidth and a higher coupling coefficient. Therefore, by setting d / p to 0.5 or less, a resonator with a high coupling coefficient can be constructed using the bulk wave in the thickness-shear primary mode.

[0048] When the piezoelectric layer 20 has thickness variations, the thickness d of the piezoelectric layer 20 may be an average value of the thickness variations.

[0049] 7 is a plan view illustrating an example in which a pair of electrodes is provided in the elastic wave device according to the first embodiment. In the elastic wave device 10, a pair of electrodes including electrode fingers 31 and 32 is provided on the first main surface 20a of the piezoelectric layer 20. Note that K in FIG. 7 represents the cross width. As described above, in the elastic wave device 10 according to the present disclosure, the number of electrode pairs may be one pair. Even in this case, if the d / p is 0.5 or less, a bulk wave in the thickness-shear first-order mode can be effectively excited.

[0050] In the acoustic wave device 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 signals can be effectively reduced. This will be described with reference to FIGS. 8 and 9.

[0051] 8 is a reference diagram showing an example of the resonance characteristics of the elastic wave device according to the first embodiment. As shown in FIG. 8, a spurious component indicated by an arrow B appears between the resonance frequency and the anti-resonance frequency. Note that, when d / p=0.08 and LiNbO ３ The Euler angles were (0°, 0°, 90°), and the metallization ratio was set to MR=0.35.

[0052] The metallization ratio MR will be explained with reference to FIG. 1 . Focusing on a pair of electrode fingers 31 and 32 in the electrode structure of FIG. 1 , assume that only this pair of electrode fingers 31 and 32 are provided. In this case, the area surrounded by the dashed line is the intersection region C. When the electrode fingers 31 and 32 are viewed in a direction perpendicular to the extension direction of the electrode fingers 31 and 32, i.e., in the opposing direction, the intersection region C includes the region where the electrode fingers 31 overlap with the electrode fingers 32, the region where the electrode fingers 32 overlap with the electrode fingers 31, and the region between the electrode fingers 31 and 32 where the electrode fingers 31 and 32 overlap. The metallization ratio MR is the ratio of the area of ​​the electrode fingers 31 and 32 within the intersection region C to the area of ​​the intersection region C. In other words, the metallization ratio MR is the ratio of the area of ​​the metallization portion to the area of ​​the intersection region C.

[0053] When multiple pairs of electrode fingers 31 and electrode fingers 32 are provided, the ratio of the metallization portion included in all the intersection regions C to the total area of ​​the intersection regions C may be defined as MR.

[0054] 9 is an explanatory diagram showing the relationship between the relative bandwidth when a large number of elastic wave resonators are configured in the elastic wave device according to the first embodiment and the amount of phase rotation of the spurious impedance normalized by 180 degrees as the magnitude of the spurious. The relative bandwidth was adjusted by changing the film thickness of piezoelectric layer 20 and the dimensions of electrode fingers 31 and 32. Also, FIG. 9 shows the relationship between the relative bandwidth and the spurious impedance normalized by 180 degrees as the magnitude of the spurious. ３ Although this is the result when a piezoelectric layer 20 having a cut angle of 100° is used, the same tendency is observed when a piezoelectric layer 20 having a different cut angle is used.

[0055] In the region surrounded by ellipse J in Figure 9, the spurious is as large as 1.0. As is clear from Figure 9, when the fractional bandwidth exceeds 0.17, i.e., 17%, large spurious signals with a spurious level of 1 or more appear within the passband, even if the parameters constituting the fractional bandwidth are changed. That is, as in the resonance characteristics shown in Figure 8, large spurious signals indicated by arrow B appear within the passband. Therefore, it is preferable that the fractional bandwidth be 17% or less. In this case, the spurious signals can be reduced by adjusting the film thickness of piezoelectric layer 20 and the dimensions of electrode fingers 31 and 32.

[0056] FIG. 10 is an explanatory diagram showing the relationship between d / 2p, metallization ratio MR, and fractional bandwidth. Various elastic wave devices 10 with different d / 2p and MR were constructed in the elastic wave device 10 according to the first embodiment, and the fractional bandwidth was measured. The hatched area to the right of dashed line D in FIG. 10 represents the region where the fractional bandwidth is 17% or less. The boundary between this hatched area and the unhatched area 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 this case, the fractional bandwidth is easily maintained at 17% or less. More preferably, the region to the right of MR = 3.5(d / 2p) + 0.05, as indicated by dashed line D1 in FIG. 10 , is the region. That is, if MR≦1.75(d / p)+0.05, the fractional bandwidth can be reliably kept to 17% or less.

[0057] FIG. 11 shows the results of LiNbO when d / p approaches 0. ３ 11 is an explanatory diagram showing a map of fractional bandwidths with respect to Euler angles (0°, θ, ψ). The hatched areas in FIG. 11 are regions where fractional bandwidths of at least 5% or more can be obtained. The range of the regions can be approximated as the ranges expressed by the following formulas (1), (2), and (3).

[0058] (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° to 80°, [180°-60° (1-(θ-50) ２ / 900) １／２ ]~180°) ...Formula (2) (0°±10°, [180°-30°(1-(ψ-90) ２ / 8100) １／２ ] to 180°, any ψ) ...Equation (3)

[0059] Therefore, in the case of the Euler angle range of the above formula (1), formula (2), or formula (3), the relative bandwidth can be made sufficiently wide, which is preferable.

[0060] Next, the detailed configuration of the load film 50 will be described. FIG. 12 is an enlarged cross-sectional view of region A shown in FIG. 2 . Note that FIG. 12 describes the load film 50 (first extension portion 51) overlapping the first electrode finger 31 a, which is located outermost in the arrangement direction of the electrode fingers 31 and 32. However, the second extension portion 52 (see FIGS. 1 and 2 ), which is located opposite the first electrode finger 31 a and overlaps the second electrode finger 32 a, which is located outermost, also has an arrangement relationship that is line-symmetrical to the first extension portion 51. The description of the first extension portion 51 also applies to the second extension portion 52. In the following description, when it is not necessary to distinguish between the first extension portion 51 and the second extension portion 52, they will simply be referred to as the load film 50.

[0061] 12 , the load film 50 is provided on the first protective film 41 and overlaps a portion of the first electrode fingers 31 a. In this embodiment, the upper surface of the first protective film 41 is formed flat. Specifically, the upper surface of the first protective film 41 is formed substantially flat over the region where the electrode fingers 31 and 32 are provided and the region where the electrode fingers 31 and 32 are not provided.

[0062] The load film 50 is provided to protrude from the upper surface of the first protective film 41. A step is formed between the load film 50 and the first protective film 41 in a region overlapping with the first electrode finger 31 a. More specifically, the first main surface 20 a of the piezoelectric layer 20 has a region where the first electrode finger 31 a and the first protective film 41 are stacked in this order, a region where the first electrode finger 31 a, the first protective film 41 and the load film 50 are stacked in this order, and a region where the first protective film 41 and the load film 50 are stacked in this order. In the region overlapping with the first electrode finger 31 a, a step is formed between a portion where the first protective film 41 is provided but the load film 50 is not provided and a portion where the load film 50 and the first protective film 41 are stacked.

[0063] The load film 50 is provided at a position shifted outward relative to the first electrode fingers 31a in the arrangement direction of the multiple electrode fingers 31, 32. One side of the load film 50 is positioned overlapping the midpoint of the first electrode fingers 31a in the width direction, and the other side of the load film 50 is positioned outward relative to the first electrode fingers 31a in the arrangement direction. That is, the load film 50 includes an overlapping region that overlaps with the first electrode fingers 31a and a non-overlapping region that does not overlap with the first electrode fingers 31a. The width W1 of the load film 50 is, for example, 0.8 μm. The width W1a of the overlapping region of the load film 50 is, for example, 0.3 μm. The width W1b of the non-overlapping region of the load film 50 is, for example, 0.5 μm.

[0064] In this embodiment, the thickness t4 of the load film 50 is 55 nm. As described above, the thickness t1 of the first protective film 41 and the thickness t2 of the second protective film 42 are 142 nm, and the thickness t3 of the IDT electrode 30 is 112 nm. The thickness t1 of the first protective film 41 is thicker than the thickness t4 of the load film 50 and is thicker than the thickness t3 of the IDT electrode 30.

[0065] The load film 50 is made of the same material as the first protective film 41. In this embodiment, the load film 50 and the first protective film 41 are made of silicon oxide (SiO ２ ). Even if the load film 50 and the first protective film 41 are made of the same material, the density of the load film 50 may be different from the density of the first protective film 41. For example, if the load film 50 is formed by vapor deposition, the actual density of the load film 50 is smaller than the density of the first protective film 41.

[0066] In this way, the load film 50 is provided overlapping the first electrode finger 31 a, and therefore, in the region overlapping with the first electrode finger 31 a positioned outermost in the arrangement direction of the plurality of electrode fingers 31, 32, the region where the load film 50 and the first protective film 41 are laminated has an acoustic impedance different from that of a region where only the first protective film 41 is laminated without the load film 50. As a result, an acoustic reflection surface R is formed in the step portion between the load film 50 and the first protective film 41 (the portion overlapping with the side surface of the load film 50).

[0067] As a result, the acoustic waves excited in the piezoelectric layer 20 are reflected by the acoustic reflecting surface R, and therefore the acoustic wave device 10 can suppress leakage of the acoustic waves in the arrangement direction of the plurality of electrode fingers 31 and 32 .

[0068] FIG. 13 is an explanatory diagram showing an example of the admittance characteristics of the elastic wave device according to the first embodiment. More specifically, FIG. 13 is an explanatory diagram showing the real part of the admittance, i.e., the conductance component, of the elastic wave device according to the first embodiment. The admittance characteristics shown in FIG. 13 represent simulation results of the admittance characteristics of elastic wave device 10 according to the first embodiment. FIG. 13 also shows simulation results of the admittance characteristics of an elastic wave device according to a comparative example. The comparative example is an elastic wave device that does not have a load film 50 in comparison with the first embodiment.

[0069] As shown in Fig. 13, in the elastic wave device according to the comparative example, ripples occur in a frequency range different from the resonant frequency. In the comparative example, particularly large ripples are generated, as indicated by dotted lines E1 and E2. In contrast, in elastic wave device 10 according to the first embodiment, the provision of load film 50 suppresses the ripples indicated by dotted lines E1 and E2 compared to the comparative example. It can be seen that, because the peak width associated with the resonant frequency is narrower in elastic wave device 10 according to the first embodiment than in the elastic wave device according to the comparative example, propagation loss is suppressed, and leakage of elastic waves is suppressed.

[0070] The shapes, widths, thicknesses, etc. of the load film 50, the first protective film 41, and the IDT electrode 30 described above are merely examples and can be changed as appropriate. For example, the side surfaces of the load film 50 may be tapered. The first extension portion 51 and the second extension portion 52 of the load film 50 shown in FIG. 1 may have the same width and thickness. Alternatively, the first extension portion 51 and the second extension portion 52 of the load film 50 may have different widths and thicknesses due to, for example, variations in the manufacturing process.

[0071] 14 is an explanatory diagram showing an example of the admittance characteristics of an elastic wave device according to a first modification of the first embodiment. The elastic wave device according to the first modification has a load film 50 made of tantalum oxide (TaO), which is different from the elastic wave device 10 according to the first embodiment. ２ O ５ ) is different from the first modified example in that the load film 50 is formed of a material different from that of the first protective film 41. More specifically, the load film 50 of the first modified example is formed of a material having a higher density than silicon oxide used for the first protective film 41. The thickness t4 of the load film 50 is 25 nm. The widths W1, W1a, and W1b of the load film 50, the first protective film 41, the IDT electrode 30, and other configurations are the same as those in the first embodiment. Note that, unless otherwise specified, the term "density" in this embodiment refers to a physical property value specific to the material.

[0072] 14 , the elastic wave device according to the first modification exhibits reduced ripples indicated by dotted lines E1 and E2 compared to the comparative example, similar to elastic wave device 10 according to the first embodiment. Furthermore, the first modification also exhibits reduced peak widths associated with the resonant frequencies, thereby reducing propagation loss.

[0073] Second Modification of First Embodiment FIG. 15 is an explanatory diagram illustrating an example of the admittance characteristics of an elastic wave device according to a second modification of the first embodiment. The elastic wave device according to the second modification is different from the elastic wave device 10 according to the first embodiment in that the load film 50 is made of silicon dioxide (SiOC). That is, in the second modification, the load film 50 is made of a different material than the first protective film 41. More specifically, the load film 50 according to the second modification is made of a material with a lower density than the silicon dioxide used for the first protective film 41. The thickness t4 of the load film 50 is 105 nm. The widths W1, W1a, and W1b of the load film 50, the first protective film 41, the IDT electrode 30, and other configurations are the same as those of the first embodiment.

[0074] 15 , the elastic wave device according to the second modification example, like elastic wave device 10 according to the first embodiment, exhibits reduced ripples indicated by dotted lines E1 and E2 compared to the comparative example. Furthermore, the peak width associated with the resonant frequency is also narrowed in the second modification example, which indicates that propagation loss is reduced.

[0075] 16 is an explanatory diagram showing an example of the admittance characteristics of an elastic wave device according to a third modification of the first embodiment. The elastic wave device according to the third modification has a load film 50 made of silicon nitride (Si ３ N ４ ) in the third modified example. That is, in the third modified example, the load film 50 is formed of a material different from that of the first protective film 41. More specifically, the load film 50 of the third modified example is formed of a material harder than silicon oxide used for the first protective film 41. The thickness t4 of the load film 50 is 55 nm. The widths W1, W1a, and W1b of the load film 50, the first protective film 41, the IDT electrode 30, and other configurations are the same as those in the first embodiment. Note that, unless otherwise specified, "hardness" in this embodiment refers to a physical property value specific to the material.

[0076] 16 , the elastic wave device according to the third modification exhibits reduced ripples indicated by dotted lines E1 and E2 compared to the comparative example. Furthermore, the elastic wave device according to the third modification also exhibits reduced ripples indicated by dotted line E3. Similar to elastic wave device 10 according to the first preferred embodiment, the elastic wave device according to the third modification exhibits reduced ripples and reduced propagation loss.

[0077] The materials of the load film 50 shown in the first to third modified examples are merely examples and are not limited to these. The material of the load film 50 may be, for example, at least one of carbon-added silicon oxide, silicon oxide, silicon nitride, tantalum oxide, aluminum nitride, alumina, hafnium oxide, niobium oxide, and tungsten oxide.

[0078] 17 is a cross-sectional view showing an elastic wave device according to a fourth modification of Embodiment 1. As shown in Fig. 17 , in elastic wave device 10A according to the fourth modification, load film 50 is provided in a region overlapping outermost first electrode finger 31 a and electrode finger 32 adjacent to first electrode finger 31 a.

[0079] The load film 50 is provided continuously across two electrode fingers (first electrode finger 31 a and electrode finger 32). One side surface of the load film 50 is arranged so as to overlap the midpoint of the electrode finger 32 in the width direction, and the other side surface of the load film 50 is positioned outward of the first electrode finger 31 a in the arrangement direction. As in the first embodiment, the load film 50 is made of silicon oxide (SiO ２ ) is formed.

[0080] In the fourth modification, the thickness t4 of the load film 50 is 35 nm. The width W1 of the load film 50 is, for example, 2.88 μm. The width W1a of the overlapping region of the load film 50 is, for example, 2.63 μm. The width W1b of the non-overlapping region of the load film 50 is, for example, 0.25 μm.

[0081] 18 is an explanatory diagram showing an example of the admittance characteristics of an elastic wave device according to a fourth modified example of the first embodiment. As shown in FIG. 18 , elastic wave device 10A according to the fourth modified example, like elastic wave device 10 according to the first embodiment, exhibits reduced ripples indicated by dotted lines E1 and E2 compared to the comparative example. Furthermore, elastic wave device 10A according to the fourth modified example exhibits reduced ripples indicated by dotted line E3. Furthermore, the fourth modified example exhibits reduced propagation loss on the high-frequency side, from dotted line E2 to dotted line E3.

[0082] 19 is a cross-sectional view showing an elastic wave device according to a fifth modification of the first embodiment. As shown in FIG. 19 , unlike the fourth modification, elastic wave device 10B according to the fifth modification includes a plurality of load films 50 for each of a plurality of electrode fingers 31 (first electrode fingers 31 a) and 32. The plurality of load films 50 are provided in regions overlapping with the outermost first electrode finger 31 a and in regions overlapping with the electrode finger 32 adjacent to the first electrode finger 31 a. The load film 50 overlapping with the first electrode finger 31 a and the load film 50 overlapping with the electrode finger 32 are disposed at a distance from each other.

[0083] In the fifth modification, the material and shape of the plurality of load films 50 are the same as those in the first embodiment. That is, the load films 50 are made of silicon oxide (SiO ２ ). The thickness t4 of the load film 50 is 55 nm. The width W1 of the load film 50 is, for example, 0.8 μm. The width W1a of the overlapping region of the load film 50 is, for example, 0.3 μm. The width W1b of the non-overlapping region of the load film 50 is, for example, 0.5 μm.

[0084] 20 is a diagram illustrating the relationship between the number of electrode fingers overlapping with the load film and the phase in elastic wave devices according to fourth and fifth modified examples of the first embodiment, where the phase on the vertical axis indicates the phase near the resonant frequency.

[0085] In the first embodiment and each of the modified examples described above, the load film 50 is arranged so as to overlap one or two of the outermost electrode fingers 31, 32 in the arrangement direction of the plurality of electrode fingers 31, 32. However, this is not limiting. As shown in Fig. 20, when the number of electrode fingers 31, 32 overlapping with the load film 50 is three or less, the phase is large (e.g., 81 degrees or more). When the number of electrode fingers 31, 32 overlapping with the load film 50 is four or more, the phase is small (e.g., 76 degrees or less). This indicates that the load film 50 may be arranged so as to overlap three of the outermost electrode fingers 31, 32 in the arrangement direction of the plurality of electrode fingers 31, 32.

[0086] 21 is a cross-sectional view showing an elastic wave device according to a sixth modification of the first embodiment. As shown in FIG. 21 , in elastic wave device 10B according to the sixth modification of the first embodiment, load film 50 has first extension portions 51 that overlap with first electrode fingers 31 a, and outer load film 53 that is provided in a region that is outward of first extension portions 51 in the arrangement direction and does not overlap with IDT electrode 30 (electrode fingers 31, 32).

[0087] The outer load film 53 is provided on the first protective film 41 in the same layer as the first extension portion 51, and is provided at a distance from the first extension portion 51. The outer load film 53 is made of the same silicon oxide (SiO ２ ). The thickness t5 of the outer load film 53 is 55 nm, the same as the thickness t4 of the first extension portion 51. The width W3 of the outer load film 53 is 0.8 μm, the same as the width W1 of the first extension portion 51. However, without being limited thereto, the thickness t5 and width W3 of the outer load film 53 may be different from the thickness t4 and width W1 of the first extension portion 51.

[0088] 22 is a diagram illustrating an example of the admittance characteristics of an elastic wave device according to a sixth modified example of the first embodiment. As shown in FIG. 22 , elastic wave device 10B according to the sixth modified example exhibits at least reduced ripple, indicated by dotted line E2, compared to the comparative example. Furthermore, elastic wave device 10B according to the sixth modified example exhibits reduced propagation loss at frequencies lower than those indicated by dotted line E1.

[0089] 23 is a cross-sectional view of an elastic wave device according to a seventh modification of the first embodiment. As shown in FIG. 23 , in an elastic wave device 10C according to the seventh modification, the thickness t1 of the first protective film 41 and the thickness t2 of the second protective film 42 are thinner than the thickness of the piezoelectric layer 20. Specifically, the thickness of the piezoelectric layer 20 is, for example, 360 nm. The thickness t1 of the first protective film 41 is 30 nm. The thickness t2 of the second protective film 42 is 30 nm. The layered structure of the IDT electrode 30 is the same as that of the first embodiment, and the thickness t3 of the IDT electrode 30 is 112 nm.

[0090] The material of the load film 50 is silicon oxide, as in the first embodiment, and the thickness t4 of the load film 50 is 70 nm. The thickness t1 of the first protective film 41 is thinner than the thickness t4 of the load film 50 and thinner than the thickness t3 of the IDT electrode 30. The width W1 of the load film 50 is, for example, 0.98 μm. The width W1a of the overlapping region of the load film 50 is, for example, 0.3 μm. The width W1b of the non-overlapping region of the load film 50 is, for example, 0.68 μm.

[0091] In the seventh modification, the first protective film 41 is provided to follow the surfaces and side surfaces of the electrode fingers 31 and 32 and the first main surface 20 a of the piezoelectric layer 20. Since the thickness t1 of the first protective film 41 is thin, irregularities that reflect the shapes of the electrode fingers 31 and 32 are formed on the upper surface of the first protective film 41.

[0092] The load film 50 is provided overlapping the first electrode fingers 31 a, as in the first embodiment. The load film 50 covers the top and side surfaces of the first electrode fingers 31 a and is provided on the first protective film 41 outside the first electrode fingers 31 a in the arrangement direction. In this modification, an acoustic reflection surface R is also formed in the region overlapping with the first electrode fingers 31 a, at the step between the load film 50 and the first protective film 41 (the portion overlapping with the side surface of the load film 50).

[0093] 24 is an explanatory diagram showing an example of the admittance characteristics of an elastic wave device according to a seventh modification of the first embodiment. The comparative example shown in FIG. 24 is an elastic wave device similar to elastic wave device 10C according to the seventh modification, i.e., an elastic wave device in which load film 50 is not provided in elastic wave device 10C in which the thicknesses of first protective film 41 and second protective film 42 are thinner than the thickness of piezoelectric layer 20. In the elastic wave device according to the comparative example, ripples occur in a frequency range different from the resonant frequency. In the comparative example, particularly large ripples are generated, as indicated by dotted lines E2 and E4.

[0094] In contrast, in elastic wave device 10C according to the seventh modification, the provision of load film 50 suppresses the ripples indicated by dotted lines E2 and E4 compared to the comparative example. Elastic wave device 10C according to the seventh modification has a narrower peak width related to the resonant frequency than the elastic wave device according to the comparative example, which indicates that propagation loss and leakage of elastic waves are suppressed. Thus, even when first protective film 41 and second protective film 42 are thin, the provision of load film 50 suppresses ripples and propagation loss.

[0095] Second Embodiment FIG. 25 is a cross-sectional view of an elastic wave device according to a second embodiment. In the first embodiment and the first to seventh modifications, the load film 50 is provided on the first protective film 41 on the first main surface 20 a side of the piezoelectric layer 20. However, the present invention is not limited to this. As shown in FIG. 25 , in an elastic wave device 10D according to the second embodiment, the load film 50 (lower first extension 54) is provided on the second main surface 20 b side of the piezoelectric layer 20 and on the lower surface of the second protective film 42. In other words, the load film 50 is not provided on the first main surface 20 a side of the piezoelectric layer 20, and the upper surface of the first protective film 41 is formed flat. The lower surface of the second protective film 42 is the surface of the second protective film 42 that faces the support substrate 11 (see FIG. 2 ).

[0096] The lower surface of the second protective film 42 is formed flat along the second main surface 20b of the piezoelectric layer 20. The load film 50 is provided on the lower surface of the second protective film 42 and overlaps with a portion of the first electrode finger 31a. The load film 50 is provided to protrude from the lower surface of the second protective film 42. In this embodiment, in the region overlapping with the first electrode finger 31a, the second main surface 20b of the piezoelectric layer 20 has a region where the second protective film 42 is provided but the load film 50 is not provided, and a region where the second protective film 42 and the load film 50 are stacked. As a result, a step is formed between the load film 50 and the second protective film 42 in the region overlapping with the first electrode finger 31a.

[0097] In the second embodiment, the load film 50 is made of the same material as the first protective film 41 and the second protective film 42, for example, silicon oxide (SiO ２ ). The width W2 of the load film 50 is, for example, 0.6 μm. The width W2a of the overlapping region of the load film 50 is, for example, 0.3 μm. The width W2b of the non-overlapping region of the load film 50 is, for example, 0.3 μm. The thickness t4 of the load film 50 is 55 nm.

[0098] The configuration of the lower first extension portion 54 in plan view is the same as that of the first extension portion 51 (see FIG. 1 ), and therefore a repeated description will be omitted. Although not shown, a lower second extension portion is also provided on the opposite side of the lower first extension portion 54 in the arrangement direction of the plurality of electrode fingers 31, 32 at a position overlapping with the second electrode finger 32 a (see FIG. 1 ).

[0099] FIG. 26 is an explanatory diagram illustrating an example of the admittance characteristics of an elastic wave device according to the second embodiment. As shown in FIG. 26 , the elastic wave device 10D according to the second embodiment, even though the load film 50 is provided on the second main surface 20b of the piezoelectric layer 20, exhibits reduced ripples indicated by dotted lines E1, E2, and E3 compared to the comparative example, similar to the elastic wave device 10 according to the first embodiment. Furthermore, the peak width associated with the resonant frequency is narrowed in the second embodiment, thereby suppressing propagation loss. Furthermore, in the second embodiment, the load film 50 is not provided on the first protective film 41, unlike the first embodiment. Therefore, the resonant frequency can be easily adjusted by changing the film thickness of the first protective film 41.

[0100] The second embodiment can be appropriately combined with the first to seventh modifications described above. That is, the load film 50 may be provided on the lower surface of the second protective film 42 and may be made of a different material from that of the second protective film 42. Alternatively, the load film 50 may be provided on the lower surface of the second protective film 42 and may be provided in a region overlapping with two or three electrode fingers (the first electrode finger 31 a and the electrode finger 32) located on the outer sides in the arrangement direction. Alternatively, the load film 50 may be provided on the lower surface of the second protective film 42. The thicknesses of the first protective film 41 and the second protective film 42 may be thinner than the thickness of the piezoelectric layer 20.

[0101] Third Embodiment Fig. 27 is a cross-sectional view showing an elastic wave device according to a third embodiment. As shown in Fig. 27 , in an elastic wave device 10E according to the third embodiment, load films 50 are provided on the top of the first protective film 41 and on the bottom surface of the second protective film 42 (the surface facing the support substrate 11 (see Fig. 2)). In the following description, the load film 50 provided on the first protective film 41 is referred to as an upper load film 50A, and the load film 50 provided on the bottom surface of the second protective film 42 is referred to as a lower load film 50B. Note that when there is no need to distinguish between the upper load film 50A and the lower load film 50B, they are simply referred to as load films 50.

[0102] In this embodiment, the upper load film 50A and the lower load film 50B are formed of the same material, for example, silicon oxide (SiO ２ The first extension portion 51 of the upper load film 50A and the first lower extension portion 54 of the lower load film 50B are provided to overlap with each other, and each overlaps with a part of the first electrode finger 31a.

[0103] The width W1 of the upper load film 50A (first extension portion 51) and the width W2 of the lower load film 50B (lower first extension portion 54) are each 0.6 μm. The width W1a of the overlapping region of the upper load film 50A and the width W2a of the overlapping region of the lower load film 50B are each 0.3 μm, for example. The width W1b of the non-overlapping region of the upper load film 50A and the width W2b of the non-overlapping region of the lower load film 50B are each 0.3 μm, for example. The film thickness t4 of the upper load film 50A and the film thickness of the lower load film 50B are 55 nm.

[0104] Although the upper load film 50A and the lower load film 50B have the same material and the same shape in the above example, the present invention is not limited to this. As will be described later in the eighth to tenth modifications, the upper load film 50A and the lower load film 50B may have different materials and different shapes.

[0105] 28 is an explanatory diagram showing an example of the admittance characteristics of an elastic wave device according to the third embodiment. As shown in FIG. 28 , in elastic wave device 10E according to the third embodiment, load films 50 are provided on both the first principal surface 20 a and the second principal surface 20 b of piezoelectric layer 20, and therefore ripples indicated by dotted lines E1, E2, and E3 are more effectively suppressed than in the comparative example. Furthermore, in the third embodiment, the peak width associated with the resonant frequency is narrowed, thereby suppressing propagation loss.

[0106] Fig. 29 is a diagram illustrating the distribution of vibration modes of an elastic wave device according to a third embodiment. Fig. 30 is a diagram illustrating the distribution of vibration modes of an elastic wave device according to a comparative example. The comparative example illustrated in Fig. 30 is configured such that load film 50 (upper load film 50A and lower load film 50B) is not provided in elastic wave device 10E according to the third embodiment.

[0107] 29 and 30 show the distribution of the magnitude of displacement of piezoelectric layer 20 for the third embodiment and the comparative example, with the horizontal axis representing the X direction (the arrangement direction of electrode fingers 31 and 32) and the vertical axis representing frequency. The upper diagrams of Fig. 29 and Fig. 30 each show a schematic cross-sectional view of an elastic wave device corresponding to the X direction, and the left diagrams of Fig. 29 and Fig. 30 show the impedance characteristics of the elastic wave device.

[0108] As shown in Figure 30, in the elastic wave device of the comparative example, the X-direction dependence of the displacement (the X-direction positions of the antinodes and nodes of the displacement) is significantly frequency-dependent. For example, the X-direction positions indicating the peak displacement vary depending on the frequency, preventing stable excitation between the electrodes. Furthermore, at a specific X-direction position (near X = 5.0 μm), the phase is inverted at the resonant frequency of 5030 MHz and at frequencies of 4900 MHz and 5120 MHz where ripples occur. As such, the elastic wave device of the comparative example may not achieve an ideal excitation mode.

[0109] In contrast, as shown in FIG. 29 , in the elastic wave device 10E according to the third embodiment, the X-direction dependence of the displacement (the X-direction positions of the antinodes and nodes of the displacement) does not have frequency dependence. That is, the X-direction positions indicating the peak displacement are constant regardless of frequency, demonstrating stable excitation between the electrodes. Furthermore, the magnitude (amplitude) of the displacement is also constant for each region between the electrodes, and no phase inversion occurs in the frequency arrangement where the resonant frequency and ripples occur. Thus, it was demonstrated that a better excitation mode than the comparative example can be obtained simply by providing the load film 50 at a position overlapping with the first electrode fingers 31 a located at the outermost positions in the arrangement direction.

[0110] Eighth Modification of Third Embodiment FIG. 31 is a cross-sectional view showing an elastic wave device according to an eighth modification of the third embodiment. As shown in FIG. 31 , in an elastic wave device 10F according to the eighth modification, a width W1 of an upper load film 50A is different from a width W2 of a lower load film 50B. The width W2 of the lower load film 50B is greater than the width W1 of the upper load film 50A. In this modification, the upper load film 50A and the lower load film 50B are made of silicon oxide (SiO ２ ) is formed.

[0111] The width W1 of the upper load film 50A is 0.6 μm. The width W1a of the overlapping region of the upper load film 50A is, for example, 0.3 μm. The width W1b of the non-overlapping region of the upper load film 50A is, for example, 0.3 μm. The thickness t4 of the upper load film 50A is 55 nm.

[0112] The lower load film 50B is provided in a region overlapping the two outermost electrode fingers in the arrangement direction, that is, the first electrode finger 31a and the electrode finger 32 adjacent to the first electrode finger 31a.

[0113] The lower load film 50B is provided continuously across two electrode fingers (the first electrode finger 31 a and the electrode finger 32). One side of the lower load film 50B is arranged so as to overlap the midpoint of the electrode finger 32 in the width direction, and the other side of the lower load film 50B is located outward in the arrangement direction than the first electrode finger 31 a. The other side of the lower load film 50B is provided at a position so as to overlap the side of the upper load film 50A.

[0114] In the eighth modified example, the width W2 of the lower load film 50B is, for example, 2.98 μm. The width W2a of the overlapping region of the lower load film 50B is, for example, 2.68 μm. The width W2b of the non-overlapping region of the lower load film 50B is, for example, 0.3 μm. The film thickness of the lower load film 50B is 40 nm. That is, the film thickness of the lower load film 50B is different from the film thickness of the upper load film 50A.

[0115] Fig. 32 is an explanatory diagram showing an example of the admittance characteristics of an elastic wave device according to an eighth modification of the third embodiment. Fig. 32 shows an enlarged view of the admittance characteristics near a frequency of 5500 MHz. Fig. 32 also shows the admittance characteristics of elastic wave device 10E according to the third embodiment and an elastic wave device according to a comparative example.

[0116] 32 , in elastic wave device 10F according to the eighth modification, by making widths W1 and W2 of upper load film 50A and lower load film 50B different, ripples indicated by dotted line E3 are suppressed compared to the comparative example. Furthermore, in elastic wave device 10F according to the eighth modification, propagation loss is suppressed near the antiresonance frequency indicated by dotted line E3 compared to elastic wave device 10E according to the third embodiment.

[0117] Although the elastic wave device 10F according to the eighth modification has been described with the width W2 of the lower load film 50B being greater than the width W1 of the upper load film 50A, the present invention is not limited to this. The width W1 of the upper load film 50A may be greater than the width W2 of the lower load film 50B.

[0118] 33 is a cross-sectional view of an elastic wave device according to a ninth modification of the third embodiment. As shown in FIG. 33 , in an elastic wave device 10G according to the ninth modification, the thickness of the upper load film 50A is different from the thickness of the lower load film 50B. In this modification, the upper load film 50A and the lower load film 50B are made of silicon oxide (SiO ２ ) is formed.

[0119] In this modification, the thickness of the upper load film 50A is thinner than the thickness of the lower load film 50B. The thickness of the upper load film 50A is, for example, 10 nm, and the thickness of the lower load film 50B is 80 nm. The width W1 of the upper load film 50A and the width W2 of the lower load film 50B are 0.6 μm. The width W1a of the overlapping region of the upper load film 50A and the width W2a of the overlapping region of the lower load film 50B are, for example, 0.3 μm. The width W1b of the non-overlapping region of the upper load film 50A and the width W2b of the non-overlapping region of the lower load film 50B are, for example, 0.3 μm.

[0120] 34 is a diagram illustrating an example of the admittance characteristics of an elastic wave device according to a ninth modification of Embodiment 3. As shown in Fig. 34 , in elastic wave device 10G according to the ninth modification, even when the thicknesses of upper load film 50A and lower load film 50B are different, the ripples indicated by dotted lines E1, E2, and E3 are suppressed, and propagation loss is reduced.

[0121] Furthermore, in this modified example, the thickness of the upper load film 50A is thinner than the thickness of the lower load film 50B, so even if the thickness of the first protective film 41 is changed to adjust the resonant frequency, changes in the admittance characteristics can be suppressed.

[0122] Although the elastic wave device 10G according to the ninth modification has been described with the upper load film 50A being thinner than the lower load film 50B, the present invention is not limited to this. The lower load film 50B may also be thinner than the upper load film 50A.

[0123] 35 is an explanatory diagram illustrating an example of the admittance characteristics of an elastic wave device according to a tenth modification of the third embodiment. In the elastic wave device according to the tenth modification, the material of the upper load film 50A is different from the material of the lower load film 50B, as compared to elastic wave device 10E of the third embodiment (see FIG. 27). Specifically, the material of the upper load film 50A is silicon oxide (SiO ２ ) was used as the material for the lower load film 50B, and carbon-added silicon oxide (SiOC) was used as the material for the lower load film 50B.

[0124] In the elastic wave device of the tenth variant, the other configurations are the same as those of the elastic wave device 10E of the third embodiment (see Figure 27), and the shapes (width, film thickness), positional relationship, etc. of the upper load film 50A and the lower load film 50B are the same as those of the third embodiment described above.

[0125] As shown in Figure 35, in the elastic wave device of the tenth variant, even when the materials of the upper load film 50A and the lower load film 50B are different, the ripples indicated by dotted lines E1, E2, and E3 are suppressed, and propagation loss is also suppressed.

[0126] The combination of materials for the upper load film 50A and the lower load film 50B is merely an example and can be changed as appropriate. The material for the upper load film 50A and the lower load film 50B is at least one of carbon-added silicon oxide, silicon oxide, silicon nitride, tantalum oxide, aluminum nitride, alumina, hafnium oxide, niobium oxide, and tungsten oxide.

[0127] 36 is a cross-sectional view of an elastic wave device according to an eleventh modification of the third embodiment. As shown in FIG. 36 , in elastic wave device 10H according to the eleventh modification, the thicknesses of first protective film 41 and second protective film 42 are thinner than the thickness of piezoelectric layer 20. Specifically, the thickness of piezoelectric layer 20 is, for example, 360 nm. The thickness of first protective film 41 is 30 nm. The thickness of second protective film 42 is 30 nm.

[0128] The width W1 of the upper load film 50A is, for example, 0.98 μm. The width W1a of the overlapping region of the upper load film 50A is, for example, 0.3 μm. The width W1b of the non-overlapping region of the upper load film 50A is, for example, 0.68 μm. The width W2 of the lower load film 50B is, for example, 0.98 μm. The width W2a of the overlapping region of the lower load film 50B is, for example, 0.3 μm. The width W2b of the non-overlapping region of the lower load film 50B is, for example, 0.68 μm.

[0129] The material of the upper load film 50A and the lower load film 50B is silicon oxide (SiO ２The upper load film 50A and the lower load film 50B each have a thickness of 70 nm. The thickness of the first protective film 41 is thinner than the thickness of the load film 50 and thinner than the thickness of the IDT electrode 30.

[0130] In the eleventh modification, the first protective film 41 is provided to follow the surfaces and side surfaces of the electrode fingers 31 and 32 and the first main surface 20 a of the piezoelectric layer 20. The upper surface of the first protective film 41 is formed with projections and depressions that reflect the shapes of the electrode fingers 31 and 32. The second protective film 42 is formed flat along the second main surface 20 b of the piezoelectric layer 20.

[0131] The upper load film 50A covers the top and side surfaces of the first electrode fingers 31 a and is provided on the first protective film 41 and further outward in the arrangement direction than the first electrode fingers 31 a. The lower load film 50B is formed flat along the second main surface 20 b of the piezoelectric layer 20.

[0132] 37 is an explanatory diagram showing an example of the admittance characteristics of an elastic wave device according to an eleventh modification of the third embodiment. As shown in FIG. 37 , elastic wave device 10H according to the eleventh modification exhibits reduced ripples, indicated by dotted lines E1 and E2, compared to the comparative example. Thus, even when load film 50 is provided on both first principal surface 20 a and second principal surface 20 b of piezoelectric layer 20 and first protective film 41 and second protective film 42 are thin, ripples are suppressed, thereby reducing propagation loss.

[0133] Although the elastic wave device 10H according to the eleventh modification has been described as having a configuration in which the thickness of the first protective film 41 and the thickness of the second protective film 42 are thinner than the thickness of the piezoelectric layer 20, the present invention is not limited to this. The thickness of either the first protective film 41 or the second protective film 42 may be thinner than the thickness of the piezoelectric layer 20.

[0134] (Twelfth Modification of Third Embodiment) Fig. 38 is an explanatory diagram showing the relationship between the phase of the spurious response and the Young's modulus of the load film in an elastic wave device according to a twelfth modification of the third embodiment. Fig. 39 is an explanatory diagram showing an example of the impedance characteristics of an elastic wave device according to the third embodiment. Fig. 39 shows the impedance characteristics of elastic wave device 10E according to the third embodiment (see Fig. 27) and an elastic wave device according to a comparative example. Fig. 38 shows the relationship between the phase of the ripple in the spurious region indicated by dotted line E5 in Fig. 39 and the Young's modulus of the load film for an elastic wave device according to the twelfth modification.

[0135] The elastic wave device according to the twelfth modification of the third embodiment differs from elastic wave device 10E according to the third embodiment (see FIG. 27 ) in that the Young's modulus of the materials used for upper load film 50A and lower load film 50B is different. The widths, thicknesses, and other conditions of upper load film 50A and lower load film 50B are the same as those of the third embodiment.

[0136] As shown in FIG. 38, when the Young's modulus of the upper load film 50A and the lower load film 50B is in the range of 50 GPa to 300 GPa, the phase of the spurious becomes small and the ripple is suppressed.

[0137] Although the twelfth modification shows a configuration in which the Young's moduli of the upper load film 50A and the lower load film 50B are different from each other, the present invention is not limited to this. As long as the Young's modulus of at least one of the upper load film 50A and the lower load film 50B is in the range of 50 GPa to 300 GPa, the spurious phase can be suppressed.

[0138] The configurations shown in the third embodiment and the eighth to twelfth modifications can be combined as appropriate. Furthermore, the third embodiment and the eighth to twelfth modifications can be combined as appropriate with the first to seventh modifications. For example, in the third embodiment and the eighth to twelfth modifications, the upper load film 50A and the lower load film 50B may be provided in a region overlapping with two or three electrode fingers (the first electrode finger 31 a and the electrode finger 32) located on the outer sides in the arrangement direction.

[0139] 40 is a cross-sectional view of an elastic wave device according to a fourth embodiment. In the first to third embodiments described above, the load film 50 is provided on at least one of the top surface of the first protective film 41 and the bottom surface of the second protective film 42. However, the present invention is not limited to this.

[0140] 40 , in an elastic wave device 10I according to the fourth embodiment, a load film 50 is provided on the first main surface 20a of a piezoelectric layer 20. The first electrode fingers 31a cover a portion of the load film 50 and are provided on the first main surface 20a of the piezoelectric layer 20. That is, the load film 50 is provided between the first main surface 20a of the piezoelectric layer 20 and the first electrode fingers 31a in the direction perpendicular to the first main surface 20a of the piezoelectric layer 20.

[0141] The first protective film 41 is provided on the first main surface 20a of the piezoelectric layer 20, covering the load film 50 and the IDT electrode 30. That is, in this embodiment, the first main surface 20a of the piezoelectric layer 20 has a region where the first electrode fingers 31a and the first protective film 41 are stacked in this order, a region where the load film 50, the first electrode fingers 31a and the first protective film 41 are stacked in this order, and a region where the load film 50 and the first protective film 41 are stacked in this order. The top surface of the first protective film 41 is formed flat over the region overlapping with the load film 50 and the IDT electrode 30 and over the region where the load film 50 and the IDT electrode 30 are not provided.

[0142] The load film 50 is made of silicon oxide (SiO ２ ). The width W1 of the load film 50 is, for example, 0.6 μm. The width W1a of the overlapping region of the load film 50 is, for example, 0.3 μm. The width W1b of the non-overlapping region of the load film 50 is, for example, 0.3 μm. The film thickness of the load film 50 is 45 nm. As in the first embodiment described above, the film thickness of the first protective film 41 and the film thickness of the second protective film 42 are 142 nm, and the film thickness of the IDT electrode 30 is 112 nm.

[0143] 41 is an explanatory diagram showing an example of the admittance characteristics of an elastic wave device according to the fourth embodiment. As shown in FIG. 41 , elastic wave device 10I according to the fourth embodiment shows that the ripples indicated by dotted lines E1 and E2 are suppressed compared to the comparative example. As such, even in a configuration in which load film 50 is provided on first main surface 20 a of piezoelectric layer 20, ripples are suppressed, and propagation loss is reduced. Furthermore, in this embodiment, the top surface of first protective film 41 is formed flat, and therefore the resonant frequency can be easily adjusted by changing the film thickness of first protective film 41.

[0144] Fifth Embodiment Fig. 42 is a cross-sectional view showing an elastic wave device according to a fifth embodiment. As shown in Fig. 42, in an elastic wave device 10J according to the fifth embodiment, a load film 50 is provided on the outermost first electrode fingers 31a. More specifically, the load film 50 is provided over the top and side surfaces of the first electrode fingers 31a and across the first main surface 20a of the piezoelectric layer 20 in a portion where the electrode fingers 31 and 32 are not provided. The load film 50 is provided to follow the steps formed by the piezoelectric layer 20 and the first electrode fingers 31a.

[0145] The load film 50 is made of tantalum oxide (Ta ２ O ５ ). The width W1 of the load film 50 is, for example, 0.89 μm. The width W1a of the overlapping region of the load film 50 is, for example, 0.3 μm. The width W1b of the non-overlapping region of the load film 50 is, for example, 0.59 μm. The thickness of the load film 50 is 35 nm. As in the first embodiment described above, the thickness of the first protective film 41 and the thickness of the second protective film 42 are 142 nm, and the thickness of the IDT electrode 30 is 112 nm.

[0146] The first protective film 41 is provided on the first main surface 20a of the piezoelectric layer 20, covering the load film 50 and the IDT electrode 30. In this embodiment, the upper surface of the load film 50 is provided in the same plane as the upper surface of the first protective film 41. In addition, the region overlapping with the first electrode finger 31a has a portion where the load film 50 is provided but the first protective film 41 is not provided, and a portion where the first protective film 41 is provided but the load film 50 is not provided. In the region overlapping with the first electrode finger 31a, the thickness of the load film 50 and the thickness of the first protective film 41 are equal.

[0147] 43 is an explanatory diagram showing an example of the admittance characteristics of an elastic wave device according to a fifth embodiment. As shown in FIG. 43 , in elastic wave device 10J according to the fifth embodiment, the ripples indicated by dotted lines E1, E2, and E3 are suppressed compared to the comparative example. As such, even in a configuration in which load film 50 is provided on first electrode fingers 31 a and the upper surface of load film 50 is provided in the same plane as the upper surface of first protective film 41, the ripples are suppressed and propagation loss is reduced.

[0148] 44 is an explanatory diagram illustrating an example of the admittance characteristics of an elastic wave device according to a thirteenth modification of the fifth embodiment. The elastic wave device according to the thirteenth modification is different from elastic wave device 10J according to the fifth embodiment in that the load film 50 is made of silicon dioxide (SiOC). The thickness of the load film 50 is 45 nm. The width of the load film 50, the first protective film 41, the IDT electrode 30, and other configurations are similar to those of the fifth embodiment.

[0149] 44 , the elastic wave device according to the thirteenth modification exhibits at least reduced ripples indicated by dotted lines E1 and E2 compared to the comparative example. Similar to elastic wave device 10J according to the fifth preferred embodiment, the elastic wave device according to the thirteenth modification exhibits reduced ripples and reduced propagation loss.

[0150] 45 is a diagram illustrating an example of the admittance characteristics of an elastic wave device according to a fourteenth modification of the fifth embodiment. The elastic wave device according to the fourteenth modification has a load film 50 made of silicon nitride (Si ３ N ４ The load film 50 has a thickness of 75 nm. The width of the load film 50, the first protective film 41, the IDT electrode 30, and other configurations are the same as those in the fifth embodiment.

[0151] 45 , the elastic wave device according to the fourteenth modification exhibits at least reduced ripples indicated by the dotted line E1 compared to the comparative example. Similar to elastic wave device 10J according to the fifth preferred embodiment, the elastic wave device according to the fourteenth modification exhibits reduced ripples and reduced propagation loss.

[0152] 46 is a cross-sectional view of an elastic wave device according to a fifteenth modification of the fifth embodiment. As shown in FIG. 46 , elastic wave device 10K according to the fifteenth modification is different from elastic wave device 10J of the fifth embodiment in that load film 50 has protruding portions 51 a. Protruding portions 51 a are provided on overlapping portions of load film 50 that overlap first electrode fingers 31 a, and protrude above the upper surface of first protective film 41.

[0153] The material of the load film 50 and the protrusion 51a is tantalum oxide (Ta), as in the fifth embodiment. ２ O ５ The thickness of the load film 50 is 35 nm, and the thickness of the protrusion 51 a (the amount of protrusion from the upper surface of the first protective film 41) is 5 nm. The width of the load film 50, the first protective film 41, the IDT electrode 30, and other configurations are the same as those in the fifth embodiment.

[0154] 47 is an explanatory diagram showing an example of the admittance characteristics of an elastic wave device according to a fifteenth modified example of the fifth embodiment. As shown in Fig. 47, the elastic wave device according to the fifteenth modified example exhibits reduced ripples, indicated by dotted lines E1, E2, and E3, compared to the comparative example. The elastic wave device according to the fifteenth modified example exhibits reduced ripples and reduced propagation loss, similar to elastic wave device 10J according to the fifth embodiment.

[0155] 48 is an explanatory diagram illustrating an example of the admittance characteristics of an elastic wave device according to a sixteenth modification of the fifth embodiment. The elastic wave device according to the sixteenth modification is different from elastic wave device 10K according to the fifteenth modification in that load film 50 is formed of silicon dioxide (SiOC). Furthermore, the thickness of load film 50 is 65 nm, and the thickness of protrusion 51 a (the amount of protrusion from the top surface of first protective film 41) is 35 nm. Furthermore, the width of load film 50, first protective film 41, IDT electrode 30, and other configurations are similar to those of the fifteenth modification.

[0156] 48 , the elastic wave device according to the sixteenth modification exhibits at least reduced ripples indicated by dotted lines E1 and E2 compared to the comparative example. Similar to elastic wave device 10K according to the fifteenth modification, the elastic wave device according to the sixteenth modification exhibits reduced ripples and reduced propagation loss.

[0157] 49 is a diagram illustrating an example of the admittance characteristics of an elastic wave device according to a seventeenth modification of the fifth embodiment. The elastic wave device according to the seventeenth modification has a load film 50 made of silicon nitride (Si ３ N ４ ) is different from the fifteenth modification. The thickness of the load film 50 is 75 nm, and the thickness of the protrusion 51a (the amount of protrusion from the upper surface of the first protective film 41) is 45 nm. The width of the load film 50, the first protective film 41, the IDT electrode 30, and other configurations are the same as those of the fifteenth modification.

[0158] 49 , the elastic wave device according to the seventeenth modification exhibits reduced ripples indicated by dotted lines E1, E2, and E3 compared to the comparative example. Similar to elastic wave device 10K according to the fifteenth modification, the elastic wave device according to the seventeenth modification exhibits reduced ripples and reduced propagation loss.

[0159] Sixth Embodiment Fig. 50 is a cross-sectional view showing an elastic wave device according to a sixth embodiment. As shown in Fig. 50, in an elastic wave device 10L according to the sixth embodiment, a load film 50 is provided on the second main surface 20b of the piezoelectric layer 20. A second protective film 42 is provided on the second main surface 20b of the piezoelectric layer 20, covering the load film 50. The lower surface of the second protective film 42 is provided flat across a region overlapping with the load film 50 and a region not overlapping with the load film 50. In this embodiment, the load film 50 is not provided on the first main surface 20a of the piezoelectric layer 20, and the upper surface of the first protective film 41 is formed flat.

[0160] The load film 50 is provided so as to overlap a part of the first electrode finger 31 a. In the sixth embodiment, the load film 50 is made of a material different from that of the first protective film 41 and the second protective film 42, for example, tantalum oxide (Ta ２ O ５). The width W2 of the load film 50 is, for example, 0.8 μm. The width W2a of the overlapping region of the load film 50 is, for example, 0.3 μm. The width W2b of the non-overlapping region of the load film 50 is, for example, 0.5 μm. The thickness t4 of the load film 50 is 95 nm.

[0161] 51 is an explanatory diagram showing an example of the admittance characteristics of an elastic wave device according to the sixth embodiment. As shown in FIG. 51 , in elastic wave device 10L according to the sixth embodiment, the ripples indicated by dotted lines E1, E2, and E3 are suppressed compared to the comparative example. Thus, in the sixth embodiment, even in a configuration in which load film 50 is provided on second main surface 20 b of piezoelectric layer 20, ripples are suppressed and propagation loss is reduced.

[0162] 52 is an explanatory diagram illustrating an example of the admittance characteristics of an elastic wave device according to an eighteenth modification of the sixth embodiment. The elastic wave device according to the eighteenth modification is different from elastic wave device 10L according to the sixth embodiment in that the load film 50 is made of carbon-doped silicon dioxide (SiOC). The thickness and width of the load film 50, the first protective film 41, the second protective film 42, the IDT electrode 30, and other components are similar to those of the sixth embodiment.

[0163] 52 , in the elastic wave device according to the eighteenth modification, similar to elastic wave device 10L according to the sixth embodiment, the ripples indicated by dotted lines E1, E2, and E3 are suppressed compared to the comparative example. In this way, in the elastic wave device according to the eighteenth modification, similar to elastic wave device 10L according to the sixth embodiment, the ripples are suppressed, and propagation loss is reduced.

[0164] 53 is an explanatory diagram showing an example of the admittance characteristics of an elastic wave device according to a 19th modification of the sixth embodiment. The elastic wave device according to the 19th modification has a load film 50 made of silicon nitride (Si ３ N ４ ) and the thickness of the load film 50 is 55 nm. The width of the load film 50, the first protective film 41, the second protective film 42, the IDT electrode 30, and other configurations are the same as those in the sixth embodiment.

[0165] 53 , the elastic wave device according to the nineteenth modification at least suppresses the ripple indicated by the dotted line E2 compared to the elastic wave device according to the comparative example. The nineteenth modification also suppresses the ripple and reduces the propagation loss, although the effect is smaller than that of elastic wave device 10L according to the sixth embodiment.

[0166] 54 is a cross-sectional view showing an elastic wave device according to a twentieth modification of the sixth embodiment. As shown in Fig. 54, in an elastic wave device 10M according to the twentieth modification, the load film 50 is provided on the second main surface 20b side of the piezoelectric layer 20. More specifically, the load film 50 faces the second main surface 20b of the piezoelectric layer 20 and is spaced apart from the second main surface 20b.

[0167] The load film 50 is disposed within the second protective film 42. That is, the second protective film 42 is disposed between the second main surface 20b of the piezoelectric layer 20 and the load film 50, and covers the side and bottom surfaces (the surfaces opposite the piezoelectric layer 20) of the load film 50. In other words, the load film 50 is disposed outside the second main surface 20b of the piezoelectric layer 20 in a direction perpendicular to the second main surface 20b of the piezoelectric layer 20. The load film 50 is not limited to being disposed within the second protective film 42, and may be disposed on the bottom surface of the second protective film 42.

[0168] The load film 50 is made of tantalum oxide (Ta ２ O ５ ). The width W2 of the load film 50 is, for example, 0.8 μm. The width and film thickness of the load film 50, and the configurations of the first protective film 41, the second protective film 42, the IDT electrode 30, etc. are the same as those in the sixth embodiment. The distance between the load film 50 and the second main surface 20 b of the piezoelectric layer 20 in the direction perpendicular to the second main surface 20 b of the piezoelectric layer 20 is 10 nm.

[0169] 55 is an explanatory diagram showing an example of the admittance characteristics of an elastic wave device according to a twentieth modification of the sixth embodiment. As shown in Fig. 55, the elastic wave device according to the twentieth modification has reduced ripples indicated by dotted lines E1, E2, and E3 compared to the comparative example. Thus, even in a configuration in which load film 50 is disposed apart from second main surface 20b of piezoelectric layer 20, ripples are reduced, and propagation loss is suppressed, similar to elastic wave device 10L according to the sixth embodiment.

[0170] 56 is a cross-sectional view showing an elastic wave device according to a seventh embodiment. As shown in Fig. 56 , in an elastic wave device 10N according to the seventh embodiment, a load film 50 is provided in a region that is outward in the arrangement direction of the electrode fingers 31, 32 from a first electrode finger 31a that is located outermost in the arrangement direction of the electrode fingers 31, 32, and does not overlap with the IDT electrode 30.

[0171] Similar to the third embodiment (see FIG. 27 ), the load film 50 of this embodiment includes an upper load film 50A provided on the first protective film 41 and a lower load film 50B provided on the lower surface of the second protective film 42. Both the upper load film 50A and the lower load film 50B are provided outside the first electrode fingers 31 a in the arrangement direction.

[0172] The upper load film 50A and the lower load film 50B are provided in an overlapping region and have the same shape. The width W1 of the upper load film 50A is equal to the width W2 of the lower load film 50B, both being 0.6 μm. The distance L1 between one side surface of the upper load film 50A and the midpoint of the width of the first electrode finger 31a is 0.4 μm. The distance L2 between one side surface of the lower load film 50B and the midpoint of the width of the first electrode finger 31a is also 0.4 μm, which is the same as the distance L1.

[0173] Fig. 57 is an explanatory diagram showing an example of the admittance characteristics of an elastic wave device according to embodiment 7. Fig. 57 compares the admittance characteristics of elastic wave device 10N according to embodiment 7 with the admittance characteristics of elastic wave device 10E according to embodiment 3 (see Figs. 27 and 28 ).

[0174] 57 , elastic wave device 10N according to the seventh embodiment has a configuration in which load film 50 is provided on the outer side in the arrangement direction of IDT electrodes 30, but similar to elastic wave device 10E according to the third embodiment, ripples are suppressed and propagation loss is also suppressed. Furthermore, in the seventh embodiment, ripples are suppressed more effectively on the high-frequency side indicated by dotted line E6 than in the third embodiment.

[0175] 58 is an explanatory diagram showing the relationship between the distance between the load film and the first electrode fingers and the admittance in an elastic wave device according to the seventh embodiment. Here, the distance between the load film 51 and the outermost first electrode finger 31a in the arrangement direction of the electrode fingers 31 is defined as distance L1a (see FIG. 56 ). In the graph shown in FIG. 58 , the horizontal axis represents the ratio (L1a / p) of distance L1a to inter-electrode pitch p, and the vertical axis represents the real part of admittance at the frequency indicated by dotted line E2 (see FIG. 14 , etc.).

[0176] 58, the admittance decreases as the ratio L1a / p decreases, that is, as the distance L1a between the first electrode finger 31a and the load film 51 decreases. L1a / p is preferably 0.9 or less.

[0177] This embodiment can be combined with the above-described embodiments and modifications. For example, the load film 50 may include only one of the upper load film 50A and the lower load film 50B. Alternatively, the upper load film 50A and the lower load film 50B may have different shapes (width, thickness). Alternatively, the upper load film 50A and the lower load film 50B may be arranged so as to be offset from each other in the arrangement direction of the electrode fingers 31 and 32.

[0178] 59 is a plan view showing an elastic wave device according to an eighth embodiment. As shown in FIG. 59 , in an elastic wave device 10O according to the eighth embodiment, the load film 50 is formed in a frame shape. Specifically, the load film 50 includes a first extension portion 51, a second extension portion 52, a third extension portion 55, and a fourth extension portion 56.

[0179] The first extending portion 51 is provided in a region overlapping with the first electrode finger 31 a located outermost in the arrangement direction of the electrode fingers 31, 32, and extends along the extension direction of the first electrode finger 31 a. The second extending portion 52 is provided in a region overlapping with the second electrode finger 32 a located outermost on the opposite side of the first electrode finger 31 a in the arrangement direction of the electrode fingers 31, 32, and extends along the extension direction of the second electrode finger 32 a.

[0180] The third extending portion 55 is connected to one end of the first extending portion 51 and the second extending portion 52 in the extension direction, and extends in the arrangement direction of the multiple electrode fingers 31, 32. The third extending portion 55 extends while overlapping with the ends of the multiple electrode fingers 31 in the extension direction. The fourth extending portion 56 is connected to the other end of the first extending portion 51 and the second extending portion 52 in the extension direction, and extends in the arrangement direction of the multiple electrode fingers 31, 32. The fourth extending portion 56 extends while overlapping with the ends of the multiple electrode fingers 32 in the extension direction.

[0181] As described above, in the elastic wave device 10O according to the eighth embodiment, the load film 50 is continuously formed in a frame shape. As a result, the acoustic reflecting surface R (see FIG. 12 ) is formed along each of the first extension portion 51, the second extension portion 52, the third extension portion 55, and the fourth extension portion 56. Therefore, the elastic wave device 10O can suppress leakage of elastic waves in the arrangement direction of the electrode fingers 31, 32 and also in the extension direction of the electrode fingers 31, 32.

[0182] The third extension portion 55 and the fourth extension portion 56 are provided in the same layer as the first extension portion 51 and the second extension portion 52 shown in the first embodiment (see FIG. 12 ), and are formed of the same material and with the same film thickness. This allows the third extension portion 55 and the fourth extension portion 56 to be formed in the same process as the first extension portion 51 and the second extension portion 52, thereby reducing manufacturing costs.

[0183] In the eighth embodiment, the load film 50 is provided on the first protective film 41, similarly to the first embodiment (see FIG. 12 ). However, the present invention is not limited to this, and the load film 50 of the eighth embodiment can be combined with each of the above-described embodiments and modified examples.

[0184] 60 is a plan view showing an elastic wave device according to a 21st modification of the eighth embodiment. In the elastic wave device 10O according to the eighth embodiment described above, the load film 50 is continuously formed in a frame shape, but the present invention is not limited to this.

[0185] 60 , in an elastic wave device 10P according to the twenty-first modification, the third extension portion 55 is disposed at one end of the first extension portion 51 and the second extension portion 52 in the extension direction and is spaced apart from the first extension portion 51 and the second extension portion 52 via a slit SL. The fourth extension portion 56 is disposed at the other end of the first extension portion 51 and the second extension portion 52 in the extension direction and is connected to the first extension portion 51 and the second extension portion 52.

[0186] In the 21st variant, the first extension portion 51, the second extension portion 52, the third extension portion 55 and the fourth extension portion 56 have slits SL in at least a portion thereof, which is advantageous compared to the 8th embodiment when forming the load film 50 by the lift-off method.

[0187] The configuration of the load film 50 can be changed as appropriate. For example, the third extension portion 55 may be connected to one end side of the first extension portion 51 and the second extension portion 52 in the extension direction, and the fourth extension portion 56 may be arranged separated from the other end side of the first extension portion 51 and the second extension portion 52 in the extension direction via a slit SL. Alternatively, both the third extension portion 55 and the fourth extension portion 56 may be arranged separated from the first extension portion 51 and the second extension portion 52 via a slit SL.

[0188] 61 is a plan view illustrating an elastic wave device according to a 22nd modification of the eighth embodiment. As shown in FIG. 61 , in an elastic wave device 10Q according to the 22nd modification, a frame-shaped lower load film 50B is provided on the second main surface 20b side of the piezoelectric layer 20. The configurations of the first extension portion 51B, the second extension portion 52B, the third extension portion 55B, and the fourth extension portion 56B of the lower load film 50B are the same as those in the eighth embodiment, and therefore, repeated description will be omitted. However, in the lower load film 50B, the widths (lengths in the direction perpendicular to the extension direction) of the third extension portion 55B and the fourth extension portion 56B are greater than the widths (lengths in the direction perpendicular to the extension direction) of the first extension portion 51B and the second extension portion 52B.

[0189] In elastic wave device 10Q according to the twenty-second modification, an upper load film 50A including first extension portions 51 and second extension portions 52 (see FIGS. 1 and 2 ), similar to load film 50 of the first embodiment, is provided on the first main surface 20a side of piezoelectric layer 20. As in the first embodiment, silicon oxide is used for upper load film 50A and lower load film 50B.

[0190] By differentiating the configuration of the upper load film 50A provided on the first main surface 20a side of the piezoelectric layer 20 from the configuration of the lower load film 50B provided on the second main surface 20b side of the piezoelectric layer 20, the membrane shape of the piezoelectric layer 20 becomes a convex shape on the first main surface 20a side. This makes it possible to suppress sticking of the piezoelectric layer 20.

[0191] Ninth Embodiment Fig. 62 is a circuit diagram showing an elastic wave device according to a ninth embodiment. As shown in Fig. 62, an elastic wave device 10R according to the ninth embodiment includes a plurality of series arm resonators 61, 62, and 63 and a plurality of parallel arm resonators 64, 65, 66, and 67. The plurality of series arm resonators 61, 62, and 63 are connected in series to a signal path between an input terminal 60A and an output terminal 60B. The plurality of parallel arm resonators 64, 65, 66, and 67 are connected in parallel between the signal path between the input terminal 60A and the output terminal 60B and ground 68. The elastic wave device 10R according to the ninth embodiment is a so-called ladder filter.

[0192] One terminal of each of the series-connected series arm resonators 61, 62, and 63 is electrically connected to the input terminal 60A, and the other terminal is electrically connected to the output terminal 60B. One terminal of the parallel arm resonator 64 is electrically connected to the input terminal 60A, and the other terminal is electrically connected to ground 68. One terminal of the parallel arm resonator 65 is electrically connected to a signal path connecting the series arm resonators 61 and 62, and the other terminal is electrically connected to ground 68. One terminal of the parallel arm resonator 66 is electrically connected to a signal path connecting the series arm resonators 62 and 63, and the other terminal is electrically connected to ground 68. One terminal of the parallel arm resonator 67 is electrically connected to the output terminal 60B, and the other terminal is electrically connected to ground 68.

[0193] In this embodiment, the plurality of series arm resonators 61, 62, and 63 and the plurality of parallel arm resonators 64, 65, 66, and 67 employ load films 50 having different configurations. For example, the plurality of series arm resonators 61, 62, and 63 have the load films 50 shown in the first embodiment (see FIGS. 12 and 13). The admittance characteristics of the plurality of series arm resonators 61, 62, and 63 are similar to those shown in FIG. 13, and therefore repeated description will be omitted.

[0194] On the other hand, the parallel arm resonators 64, 65, 66, and 67 have the load film 50 shown in the fourth modified example (see FIGS. 17 and 18). The admittance characteristics of the parallel arm resonators 64, 65, 66, and 67 are the same as those in FIG. 17, and therefore repeated description will be omitted.

[0195] In this embodiment, by changing the configuration of the load film 50 between the plurality of series arm resonators 61, 62, and 63 and the plurality of parallel arm resonators 64, 65, 66, and 67, it is possible to obtain a better output waveform as a filter.

[0196] Although the elastic wave device 10R according to the ninth preferred embodiment is combined with the load film 50 shown in the first preferred embodiment and the fourth modified example, the present invention is not limited to this. The ninth preferred embodiment can be combined with the above-described embodiments and modified examples.

[0197] 63 is a cross-sectional view of an elastic wave device according to Modification 23. In the elastic wave device 10 according to the first embodiment described above, the support substrate 11 has the cavity 14, and the cavity 14 (hollow portion) is provided on the second main surface 20b side of the piezoelectric layer 20, which is a so-called membrane structure. However, the present invention is not limited to this.

[0198] 63 , in an elastic wave device 10S according to the 23rd modification, an acoustic multilayer film 43 is laminated on the second main surface 20b of the piezoelectric layer 20. The acoustic multilayer film 43 has a laminate structure of low acoustic impedance layers 43a, 43c, and 43e, which have a relatively low acoustic impedance, and high acoustic impedance layers 43b and 43d, which have a relatively high acoustic impedance. The low acoustic impedance layers 43a, 43c, and 43e are made of, for example, SiO ２The high acoustic impedance layers 43b and 43d are made of metal such as W or Pt, or AlN or Si ３ N ４ When the acoustic multilayer film 43 is used, bulk waves in the first thickness-shear mode can be confined within the piezoelectric layer 20 without using the cavity portion 14.

[0199] In acoustic wave device 10S, by setting d / p to 0.5 or less, resonance characteristics based on bulk waves in the first thickness-shear mode can be obtained. Note that the number of stacked low acoustic impedance layers 43a, 43c, and 43e and high acoustic impedance layers 43b and 43d in acoustic multilayer film 43 is not particularly limited. It is sufficient that at least one high acoustic impedance layer 43b or 43d is located farther from piezoelectric layer 20 than low acoustic impedance layers 43a, 43c, and 43e.

[0200] The low acoustic impedance layers 43a, 43c, and 43e and the high acoustic impedance layers 43b and 43d can be made of any suitable material as long as the above acoustic impedance relationship is satisfied. For example, the low acoustic impedance layers 43a, 43c, and 43e can be made of silicon oxide or silicon oxynitride. The high acoustic impedance layers 43b and 43d can be made of alumina, silicon nitride, or metal.

[0201] 63 shows an example in which the load film 50 shown in the first embodiment is provided, but the present invention is not limited to this. The twenty-third modified example can be combined with each of the above-described embodiments and modified examples.

[0202] 64 is a cross-sectional view of an elastic wave device according to a 24th modification. In the elastic wave device 10 according to the first embodiment described above, the IDT electrode 30 is provided on the first main surface 20 a of the piezoelectric layer 20. However, this is not limiting. As shown in FIG. 64 , an elastic wave device 10T according to the 24th modification has a first IDT electrode 30A provided on the first main surface 20 a of the piezoelectric layer 20 and a second IDT electrode 30B provided on the second main surface 20 b of the piezoelectric layer 20. The first IDT electrode 30A and the second IDT electrode 30B have the same configuration as the IDT electrode 30 (see FIGS. 1 and 2 ).

[0203] The electrode fingers 36 and 37 of the second IDT electrode 30B are provided in an area overlapping the electrode fingers 31 and 32 of the first IDT electrode 30A. The electrode fingers 36 and 37 of the second IDT electrode 30B are provided with the same width and the same inter-electrode pitch as the electrode fingers 31 and 32 of the first IDT electrode 30A. The load film 50 is provided in an area overlapping the first electrode finger 31 a of the first IDT electrode 30A and the first electrode finger 36 a of the second IDT electrode 30B.

[0204] In the twenty-fourth modification, the first IDT electrode 30A and the second IDT electrode 30B are provided on the first principal surface 20a and the second principal surface 20b of the piezoelectric layer 20, respectively, so that the temperature coefficient of frequency (TCF) can be improved.

[0205] 64 shows an example in which the load film 50 shown in the first embodiment is provided, but the present invention is not limited to this. The 24th modification can be combined with each of the above-described embodiments and modifications.

[0206] 65 is a cross-sectional view illustrating an elastic wave device according to a 25th modification. As shown in FIG. 65 , in elastic wave device 10U according to the 25th modification, the electrode width of first electrode finger 31 a located on the outermost side in the arrangement direction of electrode fingers 31, 32 is smaller than the electrode width of electrode fingers 31, 32 located in the center in the arrangement direction. Furthermore, inter-electrode pitch P2 at the outermost side in the arrangement direction is smaller than inter-electrode pitch P1 at the center. Here, inter-electrode pitch P2 is the inter-electrode distance between first electrode finger 31 a located on the outermost side in the arrangement direction of electrode fingers 31, 32 and the electrode finger 32 adjacent thereto. Inter-electrode pitch P1 is the inter-electrode distance between electrode fingers 31, 32 located more centrally in the arrangement direction than first electrode finger 31 a and the electrode finger 32 adjacent thereto.

[0207] Specifically, for example, the electrode width of the first electrode finger 31 a located on the outermost side in the arrangement direction is 0.3 μm, and the electrode width of the other electrode fingers 31, 32 located in the center is 0.6 μm. The outermost inter-electrode pitch P2 in the arrangement direction is 2.23 μm, and the inter-electrode pitch P1 in the center, which is closer to the inter-electrode pitch P2, is 2.38 μm.

[0208] The load film 50 is provided in a region that does not overlap with the first electrode finger 31 a. That is, the load film 50 is provided in a region that is outward in the arrangement direction of the electrode fingers 31, 32 from the first electrode finger 31 a that is located outermost in the arrangement direction of the electrode fingers 31, 32, and does not overlap with the IDT electrode 30. The width W1 of the load film 50 is 0.6 μm. The thickness of the load film 50 is 90 nm.

[0209] FIG. 66 is an explanatory diagram illustrating an example of the admittance characteristics of an elastic wave device according to the 25th modification. As shown in FIG. 66 , elastic wave device 10U according to the 25th modification exhibits reduced ripples, indicated by dotted lines E1, E2, and E3, compared to the comparative example. Thus, even in a configuration in which the electrode width of first electrode finger 31 a is smaller than the electrode widths of other electrode fingers 31 and 32 and interelectrode pitch P2 is smaller than interelectrode pitch P1, ripples are suppressed, thereby reducing propagation loss. Furthermore, elastic wave device 10U according to the 25th modification effectively suppresses propagation loss over a wide frequency range from 4700 MHz to 5500 MHz, compared to the above-described embodiments and modifications.

[0210] 65 illustrates a configuration in which the electrode width of one first electrode finger 31 a is smaller than the electrode widths of the other electrode fingers 31, 32. However, this is not limiting. Alternatively, the electrode widths of the outermost electrode fingers 31, 32 in the arrangement direction of the electrode fingers 31, 32 may be smaller than the electrode widths of the other electrode fingers 31, 32 located in the center. Similarly, the inter-electrode pitch P of three or more outermost electrode fingers 31, 32 in the arrangement direction of the electrode fingers 31, 32 may be smaller than the inter-electrode pitch P of the other electrode fingers 31, 32 located in the center.

[0211] 65 shows a configuration in which the load film 50 is provided in a region that does not overlap with the first electrode fingers 31 a, but this is not limiting. In the 25th modification, the load film 50 may be provided in a region that overlaps with the first electrode fingers 31 a. The load film 50 is provided on the first protective film 41, but this is not limiting. The 25th modification can be combined with the above-described embodiments and modifications.

[0212] 67 is a cross-sectional view showing an elastic wave device according to Modification 26. As shown in Fig. 67 , in elastic wave device 10V according to Modification 26, electrode width W4 of first electrode finger 31a located on the outermost side in the arrangement direction of multiple electrode fingers 31, 32 is larger than the electrode width of electrode fingers 31, 32 located in the center in the arrangement direction. Furthermore, inter-electrode pitch P2 at the outermost side in the arrangement direction is larger than inter-electrode pitch P1 at the center.

[0213] Specifically, for example, the electrode width of the first electrode finger 31 a located on the outermost side in the arrangement direction is 1.0 μm, and the electrode width of the other electrode fingers 31, 32 located in the center is 0.6 μm. The outermost inter-electrode pitch P2 in the arrangement direction is 2.58 μm, and the inter-electrode pitch P1 in the center, which is closer to the inter-electrode pitch P2, is 2.38 μm.

[0214] In the 26th modification, the load film 50 is provided in a region overlapping with the first electrode finger 31a, which is the outermost of the plurality of electrode fingers 31, 32 in the arrangement direction of the plurality of electrode fingers 31, 32. The width W1 of the load film 50 is 0.8 μm. The thickness of the load film 50 is 15 nm. One side surface of the load film 50 is positioned shifted toward the adjacent electrode finger 32 from the center of the first electrode finger 31a in the width direction. The width of the overlapping region of the load film 50 with the first electrode finger 31a is, for example, 0.7 μm. The width of the non-overlapping region of the load film 50 is, for example, 0.1 μm.

[0215] 68 is an explanatory diagram showing an example of the admittance characteristics of an elastic wave device according to Modification 26. As shown in FIG. 68 , elastic wave device 10V according to Modification 26 exhibits reduced ripples indicated by dotted lines E1 and E2 compared to the comparative example. As such, even in a configuration in which the electrode width of first electrode finger 31 a is greater than the electrode widths of the other electrode fingers 31 and 32 and inter-electrode pitch P2 is greater than inter-electrode pitch P1, ripples are suppressed, thereby reducing propagation loss.

[0216] 67 illustrates a configuration in which the electrode width of one first electrode finger 31 a is larger than the electrode widths of the other electrode fingers 31, 32. However, this is not limiting. Alternatively, the electrode widths of the outermost electrode fingers 31, 32 in the arrangement direction of the electrode fingers 31, 32 may be larger than the electrode widths of the other electrode fingers 31, 32 located in the center. Similarly, the inter-electrode pitch P of three or more outermost electrode fingers 31, 32 in the arrangement direction of the electrode fingers 31, 32 may be larger than the inter-electrode pitch P of the other electrode fingers 31, 32 located in the center.

[0217] 67 shows a configuration in which the load film 50 is provided in a region overlapping with the first electrode fingers 31 a, but this is not limiting. Also, the load film 50 is provided on the first protective film 41, but this is not limiting. The 26th modification can be combined with the above-described embodiments and modifications.

[0218] 69 is a diagram illustrating an example of the admittance characteristics of an elastic wave device according to a 27th modification. Fig. 70 is a diagram illustrating an example of the impedance phase in a higher mode. The elastic wave device according to the 27th modification shown in Fig. 69 has a configuration in which the first protective film 41 and the second protective film 42 have different thicknesses in elastic wave device 10 according to the first embodiment.

[0219] 69 shows the frequency characteristics of the absolute value of admittance for the elastic wave device according to Modification 27. As shown in Fig. 69, in the elastic wave device according to Modification 27, a higher-order mode of resonance (hereinafter referred to as S2 mode) occurs in a frequency region indicated by a dashed dotted line F1 that is different from the resonant frequency.

[0220] The horizontal axis of the graph shown in Fig. 70 represents the ratio ((t1+tLN / 2) / (t2+tLN / 2)) of the sum (t1+tLN / 2) of the thickness t1 of the first protective film 41 and 1 / 2 of the thickness tLN of the piezoelectric layer 20 to the sum (t2+tLN / 2) of the thickness t2 of the second protective film 42 and 1 / 2 of the thickness tLN of the piezoelectric layer 20. The vertical axis of the graph shown in Fig. 70 corresponds to the intensity of the S2 mode.

[0221] 70, the range indicated by arrows F2 and F3 indicates the ratio (t1 + tLN / 2) / (t2 + tLN / 2) in the configuration of the acoustic resonator described in JP-T-2022-524136. In the acoustic resonator described in JP-T-2022-524136, the ratio (t1 + tLN / 2) / (t2 + tLN / 2) is 0.93 or less and 1.07 or more, and the intensity of the S2 mode is large.

[0222] In contrast, in the 27th modification, the ratio (t1 + tLN / 2) / (t2 + tLN / 2) is in the range of 0.94 to 1.06, inclusive, and the intensity of the S2 mode is smaller than that of the acoustic resonator device described in JP-A 2022-524136. In other words, in the 27th modification, when the total distance from the center of the thickness of the piezoelectric layer 20 to the top surface of the first protective film 41 is A and the total distance from the center of the thickness of the piezoelectric layer 20 to the top surface of the second protective film 42 is B, it is preferable that the value of A / B be in the range of 1-0.06 to 1+0.06, inclusive.

[0223] Although the 27th modification has been described with reference to the elastic wave device 10 according to the first embodiment, in which the first protective film 41 and the second protective film 42 have different thicknesses, the present invention is not limited to this. The relationship between the thickness t1 of the first protective film 41, the thickness tLN of the piezoelectric layer 20, and the thickness t2 of the second protective film 42 in the 27th modification can be combined with any of the embodiments and modifications described above.

[0224] 71 is a cross-sectional view showing an elastic wave device according to a 28th modification. Fig. 72 is an explanatory diagram showing the relationship between the amount of movement of the load film and the admittance in an elastic wave device according to the 28th modification. As shown in Fig. 71 , in elastic wave device 10W according to the 28th modification, the position of one side surface of load film 50 is shifted from widthwise midpoint 30C of first electrode finger 31a, which is located outermost in the arrangement direction of multiple electrode fingers 31, 32.

[0225] In the 28th modification, the distance between one side surface of the load film 50 and the midpoint 30C of the first electrode finger 31a in the width direction in the arrangement direction of the electrode fingers 31 and 32 is represented as the "movement amount G of the load film 50." When one side surface of the load film 50 is located inside the midpoint 30C of the first electrode finger 31a in the width direction in the arrangement direction of the electrode fingers 31 and 32, the movement amount is represented as +G. When one side surface of the load film 50 is located outside the midpoint 30C of the first electrode finger 31a in the width direction in the arrangement direction of the electrode fingers 31 and 32, the movement amount is represented as -G. Note that in FIG. 71 , one side surface of the load film 50 is arranged to overlap the midpoint 30C of the first electrode finger 31a in the width direction. In this case, the movement amount G of the load film 50 is G=0.

[0226] Although the following description will be directed to the load film 50 overlapping the first electrode finger 31 a, the distance between one side surface of the load film 50 and the midpoint 30C of the second electrode finger 32 a in the width direction of the load film 50 arranged overlapping the second electrode finger 32 a located on the opposite side of the first electrode finger 31 a is also represented as the movement amount G of the load film 50. The description of the first electrode finger 31 a and the load film 50 overlapping the first electrode finger 31 a can also be applied to the second electrode finger 32 a and the load film 50 overlapping the second electrode finger 32 a.

[0227] 72 represents the ratio G / p of the movement amount G of the load film 50 to the center-to-center distance p between adjacent electrode fingers 31, 32. The vertical axis represents the real part of the admittance at a frequency of 5250 MHz.

[0228] 72, the admittance is at its minimum when the ratio G / p is 0, and the admittance increases as the ratio G / p increases in the positive direction or decreases in the negative direction. In other words, the admittance is at its minimum when one side surface of the load film 50 is positioned so as to overlap the midpoint 30C in the width direction of the first electrode finger 31a that is located outermost in the arrangement direction of the multiple electrode fingers 31, 32. It was also shown that the admittance increases when one side surface of the load film 50 is positioned so as to deviate from the midpoint 30C in the width direction of the first electrode finger 31a.

[0229] More specifically, on the +G side, the admittance increases when the ratio G / p is in the range of +0 to +0.2, and is maximized when the ratio G / p is in the range of +0.2 to +0.3. On the -G side, the admittance increases when the ratio G / p is in the range of -0 to -0.7, and is maximized when the ratio G / p is near -0.7. As described above, in the 28th modification, the ratio G / p of the movement amount G of the load film 50 to the center-to-center distance p between adjacent electrode fingers 31, 32 satisfies -0.2≦G / p≦+0.2.

[0230] 73 is a plan view of an elastic wave device according to a 29th modification. Fig. 74 is a diagram illustrating an example of impedance characteristics of the elastic wave device according to the 29th modification. Fig. 75 is an enlarged diagram illustrating the dotted line H1 in Fig. 74 .

[0231] As shown in FIG. 73 , an elastic wave device 10AA according to the 29th modification differs from the above-described embodiments and modifications in that the width of the load film 50 in the X direction (arrangement direction) varies along the Y direction (direction perpendicular to the column direction). Specifically, the width of the load film 50 in the X direction continuously increases from one side of the Y direction to the other side of the Y direction. The width of the load film 50 in the X direction at the end of the load film 50 on the busbar electrode 33 side is larger than the width of the end of the load film 50 on the busbar electrode 34 side. However, FIG. 73 is merely an example, and the shape of the load film 50 can be modified as appropriate. For example, the width of the load film 50 in the X direction in at least a portion of the extension direction may be different from the width of the other portions of the load film 50 in the X direction.

[0232] The thickness of the piezoelectric layer 20 in the 29th modification is, for example, approximately 180 nm. The first protective film 41 and the second protective film 42 are made of silicon oxide. The thicknesses of the first protective film 41 and the second protective film 42 are each 142 nm. The IDT electrode 30 has an electrode configuration of Ti / AlCu / Ti / AlCu laminated films, with respective thicknesses of 12 nm / 70 nm / 18 nm / 12 nm from the piezoelectric layer 20 side. The IDT electrode 30 has a total of 101 electrode fingers 31 and 32. The interelectrode pitch of the electrode fingers 31 and 32 is 2.38 μm, and each electrode width is 0.6 μm. The length of the electrode fingers 31 and 32 in the extension direction in the intersection region C is, for example, 40 μm.

[0233] The material of the load film 50 was silicon oxide, and the thickness of the load film 50 was 55 nm. The width W1 of the load film 50 was, for example, 0.8 μm. The width W1a of the overlapping region of the load film 50 with the first electrode finger 31 a and the second electrode finger 32 a was, for example, 0.3 μm. The width W1 of the load film 50 was changed by 0.4 μm along the Y direction.

[0234] 74 and 75 , elastic wave device 10AA according to the 29th modification can suppress spurious responses at frequencies lower than the resonant frequency. That is, in the 29th modification, the spurious responses are shifted toward higher frequencies compared to the comparative example in which load film 50 has a constant width.

[0235] 76 is a plan view of an elastic wave device according to Modification 30. As shown in Fig. 76 , elastic wave device 10AB according to Modification 30 differs from the above-described embodiments and modifications in that the extension direction of load film 50 is inclined with respect to the extension direction (Y direction) of first electrode fingers 31 a and second electrode fingers 32 a.

[0236] More specifically, the width of the load film 50 in the X direction is constant along the extension direction of the load film 50. Furthermore, the first extension portion 51 and the second extension portion 52 of the load film 50 are parallel to each other, and the width W1a of the overlapping region of the load film 50 with the first electrode finger 31 a and the second electrode finger 32 a is inclined to the same side with respect to the extension direction (Y direction) of the first electrode finger 31 a and the second electrode finger 32 a.

[0237] The width W1a of the overlapping region with the first electrode finger 31 a at the end of the load film 50 (first extension 51) on the busbar electrode 33 side is smaller than the width W1a of the overlapping region with the first electrode finger 31 a at the end of the load film 50 on the busbar electrode 34 side. The width W1a of the overlapping region with the second electrode finger 32 a at the end of the load film 50 (second extension 52) on the busbar electrode 33 side is larger than the width W1a of the overlapping region with the second electrode finger 32 a at the end of the load film 50 on the busbar electrode 34 side.

[0238] 77 is a plan view of an elastic wave device according to a 31st modification. As shown in FIG. 77 , an elastic wave device 10AC according to the 31st modification differs from the above-described embodiments and modifications in that multiple load films 50 are arranged at a distance from one another along the extension direction (Y direction) of the first electrode finger 31 a and the second electrode finger 32 a. Four load films 50 are arranged overlapping one first electrode finger 31 a. Four load films 50 are arranged overlapping one second electrode finger 32 a. However, the number of load films 50 arranged overlapping one first electrode finger 31 a may be three or less or five or more. The number of load films 50 arranged overlapping one second electrode finger 32 a may be three or less or five or more.

[0239] 78 is a plan view of an elastic wave device according to Modification 32. As shown in Fig. 78 , elastic wave device 10AD according to Modification 32 differs from the above-described embodiments and modifications in the shape of load film 50 (first extension portion 51, second extension portion 52) provided on first main surface 20a of piezoelectric layer 20 and the shape of load film 50 (first lower extension portion 54A, second lower extension portion 54B) provided on second main surface 20b of piezoelectric layer 20.

[0240] The load film 50 (first extension portion 51, second extension portion 52) provided on the first main surface 20a side of the piezoelectric layer 20 increases in width in the X direction from one side to the other in the Y direction. The load film 50 (first lower extension portion 54A, second lower extension portion 54B) provided on the second main surface 20b side of the piezoelectric layer 20 decreases in width in the X direction from one side to the other in the Y direction.

[0241] Note that the shapes of the load film 50 (first extension portion 51, second extension portion 52) provided on the first main surface 20a side of the piezoelectric layer 20 and the shapes of the load film 50 (first lower extension portion 54A, second lower extension portion 54B) provided on the second main surface 20b side of the piezoelectric layer 20 shown in Figure 78 are merely examples, and any shape may be used.

[0242] 79 and 80 , an elastic wave device 10AE according to the 33rd modification is different from the above-described embodiments and modifications in that the load film 50 overlapping the first electrode finger 31a includes a first load film 57A and a second load film 57B overlapping a portion of the first load film 57A, and the load film 50 overlapping the second electrode finger 32a includes a first load film 58A and a second load film 58B overlapping a portion of the first load film 58A. This results in a stepped acoustic reflection surface of the load film 50.

[0243] 80 , the first load film 57A of the load film 50 is provided at a position shifted outward with respect to the first electrode fingers 31a in the arrangement direction of the multiple electrode fingers 31, 32. One side surface of the first load film 57A is located at the center of the first electrode fingers 31a in the width direction, and the other side surface of the first load film 57A is located outward with respect to the first electrode fingers 31a in the arrangement direction. That is, the first load film 57A includes an overlapping region that overlaps with the first electrode fingers 31a and a non-overlapping region that does not overlap with the first electrode fingers 31a.

[0244] The second load film 57B is provided to cover one side surface of the first load film 57A. The second load film 57B includes a portion overlapping the first load film 57A and a portion overlapping the first electrode finger 31a without overlapping the first load film 57A.

[0245] (Thirty-Fourth Modification) FIG. 81 is a cross-sectional view showing an elastic wave device according to a thirty-fourth modification. FIG. 82 is an enlarged cross-sectional view of a portion of FIG. 81 . FIG. 83 is an explanatory diagram showing an example of the admittance characteristics of an elastic wave device according to the thirty-fourth modification. As shown in FIGS. 81 and 82 , elastic wave device 10AF according to the thirty-fourth modification differs from the twenty-third modification (see FIG. 63 ) in that IDT electrode 30 is formed on piezoelectric layer 20 so as to be embedded in high acoustic impedance layers 43 b, 43 d or low acoustic impedance layers 43 a, 43 c, 43 e. Furthermore, in elastic wave device 10AF according to the thirty-fourth modification, the material of load film 50 is different from the layer in which IDT electrode 30 is embedded.

[0246] More specifically, the IDT electrode 30 and the load film 50 are provided on the second main surface 20 b of the piezoelectric layer 20 , and the low acoustic impedance layer 43 a is provided to cover the IDT electrode 30 and the load film 50 .

[0247] In the thirty-fourth modification, the first protective film 41 is made of silicon oxide (SiO ２ ) and the film thickness of the first protective film 41 is 33 nm.

[0248] The piezoelectric layer 20 is made of lithium niobate (LiNbO ３ ) and is a 120°±10° rotated Y-cut. The thickness of the piezoelectric layer 20 is, for example, about 300 nm.

[0249] The IDT electrode 30 is made of Al and has a film thickness of 92 nm. The IDT electrode 30 has a total of 43 electrode fingers 31 and 32. The electrode pitch between the electrode fingers 31 and 32 of the IDT electrode 30 is 3 μm, and each electrode has a width of 0.9 μm.

[0250] The acoustic multilayer film 43 is formed from a second main surface 20 b of the piezoelectric layer 20 , ２ (200nm) / Ta ２ O ５ (122nm) / SiO ２ (188nm) / Ta ２ O ５ (122nm) / SiO ２ (188nm) / Ta ２ O ５ (122nm) / SiO ２ (188 nm) are laminated in this order.

[0251] The support substrate 11 is made of silicon (Si(100)).

[0252] The material of the load film 50 is Ta ２ O ５ The thickness t of the load film 50 is 80 nm. The width W1 of the load film 50 is, for example, 800 nm. The width W1a of the overlapping region of the load film 50 is, for example, 450 nm. The width W1b of the non-overlapping region of the load film 50 is, for example, 350 nm.

[0253] As shown in FIG. 83, elastic wave device 10AF in accordance with the thirty-fourth modification example exhibits reduced loss in the frequency ranges indicated by dotted lines I1 and I2 compared to the comparative example not having load film 50.

[0254] 84 is a diagram illustrating an example of admittance characteristics of an elastic wave device according to a thirty-fifth modification. In the thirty-fifth modification, the material of the load film 50 is Si, which is different from the material of the thirty-fourth modification. ３ N ４ The load film 50 has a thickness t of 100 nm. The load film 50 has a width W1 of, for example, 1000 nm. The load film 50 has a width W1a of an overlapping region of, for example, 450 nm. The load film 50 has a width W1b of a non-overlapping region of, for example, 550 nm.

[0255] As shown in FIG. 84, the elastic wave device according to the thirty-fifth modification example exhibits reduced loss in the frequency range indicated by dotted lines J1 and J2 compared to the comparative example not having load film 50.

[0256] 85 is a plan view of an elastic wave device according to Modification 36. As shown in Fig. 85 , elastic wave device 10AG according to Modification 36 differs from elastic wave device 10O according to the eighth embodiment shown in Fig. 59 in that first extension portion 51, second extension portion 52, third extension portion 55, and fourth extension portion 56 of load film 50 are arranged to be spaced apart with slits SL interposed therebetween.

[0257] Specifically, the first extending portion 51 is provided in a region overlapping with the first electrode finger 31 a positioned outermost in the arrangement direction of the plurality of electrode fingers 31, 32, and extends along the extending direction of the first electrode finger 31 a. The first extending portion 51 is arranged on one end side of the third extending portion 55 and the fourth extending portion 56 in the extending direction, and is arranged separated from the third extending portion 55 and the fourth extending portion 56 via a slit SL.

[0258] One end of the first extending portion 51 in the extending direction (Y direction) extends to a region overlapping with the bus bar electrode 34. The other end of the first extending portion 51 in the extending direction (Y direction) extends to a region overlapping with the bus bar electrode 33.

[0259] The second extending portion 52 is provided in a region overlapping with the second electrode finger 32 a located outermost on the opposite side of the first electrode finger 31 a in the arrangement direction of the plurality of electrode fingers 31, 32, and extends along the extending direction of the second electrode finger 32 a. The second extending portion 52 is arranged on the other end side of the third extending portion 55 and the fourth extending portion 56 in the extending direction, and is arranged separated from the third extending portion 55 and the fourth extending portion 56 via a slit SL.

[0260] One end of the second extending portion 52 in the extending direction (Y direction) extends to a region overlapping with the bus bar electrode 34. The other end of the second extending portion 52 in the extending direction (Y direction) extends to a region overlapping with the bus bar electrode 33.

[0261] The third extending portion 55 is disposed between the first extending portion 51 and the second extending portion 52 in the X direction, and extends in the arrangement direction of the plurality of electrode fingers 31, 32. The third extending portion 55 also extends so as to overlap with the ends of the plurality of electrode fingers 31 in the extension direction.

[0262] The fourth extending portion 56 is disposed between the first extending portion 51 and the second extending portion 52 in the X direction, and extends in the arrangement direction of the plurality of electrode fingers 31, 32. The fourth extending portion 56 also extends so as to overlap with the ends of the plurality of electrode fingers 32 in the extension direction.

[0263] 86 is a plan view of an elastic wave device according to Modification 37. As shown in Fig. 86 , elastic wave device 10AH according to Modification 37 differs from elastic wave device 10O according to the eighth embodiment shown in Fig. 59 in that a slit SL is provided in the X-direction center of third extension portion 55 of load film 50, and a slit SL is provided in the X-direction center of fourth extension portion 56.

[0264] The third extending portion 55 is connected to one end of the first extending portion 51 and the second extending portion 52 in the extending direction, and extends in the arrangement direction of the plurality of electrode fingers 31, 32. The third extending portion 55 extends while overlapping the ends of the plurality of electrode fingers 31 in the extending direction. The third extending portion 55 is divided into two portions by a slit SL.

[0265] The fourth extending portion 56 is connected to the other end of the first extending portion 51 and the second extending portion 52 in the extending direction, and extends in the arrangement direction of the plurality of electrode fingers 31, 32. The fourth extending portion 56 extends while overlapping the ends of the plurality of electrode fingers 32 in the extending direction. The fourth extending portion 56 is divided into two portions by a slit SL.

[0266] The positions of the slits SL are not limited to the central portion in the X direction of the third extension portion 55 and the central portion in the X direction of the fourth extension portion 56, and may be other different positions. Two or more slits SL may be provided in the third extension portion 55, and the third extension portion 55 may be divided into three or more portions by the slits SL. Two or more slits SL may be provided in the fourth extension portion 56, and the fourth extension portion 56 may be divided into three or more portions by the slits SL.

[0267] 87 is a plan view of an elastic wave device according to Modification 38. As shown in Fig. 87 , elastic wave device 10AI according to Modification 38 differs from elastic wave device 10O according to the eighth embodiment shown in Fig. 59 in that a slit SL is provided in the center in the Y direction of first extension portion 51 of load film 50, and a slit SL is provided in the center in the Y direction of second extension portion 52.

[0268] The first extending portion 51 is provided in a region overlapping with the first electrode finger 31 a located outermost in the arrangement direction of the plurality of electrode fingers 31, 32, and extends along the extending direction of the first electrode finger 31 a. The first extending portion 51 is connected to one end side of the third extending portion 55 and the fourth extending portion 56 in the extending direction. The first extending portion 51 is divided into two portions by a slit SL.

[0269] The second extending portion 52 is provided in a region overlapping with the second electrode finger 32a, which is located outermost on the opposite side of the first electrode finger 31a in the arrangement direction of the plurality of electrode fingers 31, 32, and extends along the extending direction of the second electrode finger 32a. The second extending portion 52 is connected to the other end side of the third extending portion 55 and the fourth extending portion 56 in the extending direction. The second extending portion 52 is divided into two portions by a slit SL.

[0270] The positions of the slits SL are not limited to the central portion in the Y direction of the first extension portion 51 and the central portion in the Y direction of the second extension portion 52, and may be other different positions. Two or more slits SL may be provided in the first extension portion 51, and the first extension portion 51 may be divided into three or more portions by the slits SL. Two or more slits SL may be provided in the second extension portion 52, and the second extension portion 52 may be divided into three or more portions by the slits SL.

[0271] 88 is a plan view showing an elastic wave device according to Modification 39. As shown in Fig. 88 , elastic wave device 10AJ according to Modification 39 differs from elastic wave device 10 according to Embodiment 1 shown in Fig. 1 in that load film 50 extends to a position where it overlaps with bus bar electrodes 33, 34.

[0272] One end of the first extending portion 51 of the load film 50 in the extending direction (Y direction) overlaps with the Y-direction end of the bus bar electrode 34 (the end opposite the electrode fingers 32). The other end of the first extending portion 51 in the extending direction (Y direction) overlaps with the Y-direction end of the bus bar electrode 33 (the end opposite the electrode fingers 31).

[0273] One end in the extension direction (Y direction) of the second extension portion 52 of the load film 50 overlaps with the Y direction end of the bus bar electrode 34 (the end opposite the electrode fingers 32). The other end in the extension direction (Y direction) of the second extension portion 52 overlaps with the Y direction end of the bus bar electrode 33 (the end opposite the electrode fingers 31).

[0274] With this configuration, elastic wave device 10AJ according to the thirty-ninth modification can effectively suppress leakage of elastic waves in the arrangement direction of multiple electrode fingers 31, 32. Note that, although the ends of load film 50 in the extension direction coincide with the ends of bus bar electrodes 33, 34, this is not limitative, and the length of load film 50 in the extension direction can be changed as appropriate.

[0275] The materials of the load film 50 shown in the above-described embodiments and modifications are merely examples and can be changed as appropriate. The load film 50 is formed from at least one of carbon-added silicon oxide, silicon oxide, silicon nitride, tantalum oxide, aluminum nitride, alumina, hafnium oxide, niobium oxide, and tungsten oxide. The load film 50 is not limited to a single-layer film and may be a multilayer film. The load film 50 may be a combination of two or more of the above materials.

[0276] The above-described embodiment is intended to facilitate understanding of the present invention, and is not intended to limit the present invention. The present invention may be modified or improved without departing from the spirit and scope of the present invention, and equivalents thereof are also included in the present invention.

[0277] The present disclosure may also have the following configurations.

[0278] (1) An elastic wave device comprising: a piezoelectric layer having a first main surface and a second main surface facing the first main surface in a first direction; an IDT electrode provided on at least one of the first main surface and the second main surface of the piezoelectric layer, the IDT electrode including a plurality of electrode fingers arranged in a predetermined direction; a support member facing the second main surface of the piezoelectric layer and having an acoustic reflector on the second main surface side of the piezoelectric layer; and a load film provided in a region overlapping, in a plan view from the first direction, with at least one end of the IDT electrode in the arrangement direction of the plurality of electrode fingers, wherein the end includes a first electrode finger positioned outermost in the arrangement direction of the plurality of electrode fingers, wherein d is a thickness of the piezoelectric layer and p is a center-to-center distance between adjacent electrode fingers, and d / p is 0.5 or less. (2) The elastic wave device according to (1), further comprising a protective film provided on at least one of the first main surface and the second main surface of the piezoelectric layer. (3) The elastic wave device according to (2), wherein the protective film includes a first protective film provided on the first main surface of the piezoelectric layer to cover the IDT electrode, and the load film is provided on the first protective film. (4) The elastic wave device according to (3), wherein a step is formed between a portion where the first protective film is provided but the load film is not provided and a portion where the load film and the first protective film are stacked in a region overlapping with the first electrode finger located outermost in an arrangement direction of the plurality of electrode fingers. (5) The elastic wave device according to (2), wherein the protective film includes a first protective film provided on the first main surface of the piezoelectric layer to cover the IDT electrode and a second protective film provided on the second main surface of the piezoelectric layer, and the load film is provided on a surface of the second protective film that faces the support member. (6) The elastic wave device according to (1), wherein the load film is provided between the first main surface of the piezoelectric layer and the first electrode finger in the first direction of the piezoelectric layer. (7) The elastic wave device according to any one of (1) to (6), wherein the load film is provided in a region overlapping the first electrode finger and an electrode finger adjacent to the first electrode finger. (8) The elastic wave device according to any one of (1) to (7), wherein the number of the first electrode fingers, the electrode fingers adjacent to the first electrode fingers, the second electrode fingers positioned outermost in the opposite side of the arrangement direction, and the electrode fingers adjacent to the second electrode fingers that overlap with the load film is six or less.(9) The elastic wave device according to any one of (1) to (8), wherein the load film has a first extension portion provided in a region overlapping the first electrode finger, and an outer load film provided in a region that is outward of the first extension portion in the arrangement direction and does not overlap the IDT electrode. (10) The elastic wave device according to (2), wherein the protective film has a first protective film provided on the first main surface of the piezoelectric layer to cover the IDT electrode, and a second protective film provided on the second main surface of the piezoelectric layer, and the load film includes an upper load film provided on the first protective film and a lower load film provided on a surface of the second protective film that faces the support member. (11) The elastic wave device according to (10), wherein a width of the upper load film is different from a width of the lower load film. (12) The elastic wave device according to (10) or (11), wherein a thickness of the upper load film is thinner than a thickness of the lower load film. (13) The elastic wave device according to any one of (10) to (12), in which the upper load film is made of a different material from the lower load film. (14) The elastic wave device according to any one of (2) to (5), in which the thickness of the protective film is thinner than the thickness of the piezoelectric layer. (15) The elastic wave device according to any one of (10) to (13), in which the Young's modulus of at least one of the upper load film and the lower load film is 50 GPa or greater. (16) The elastic wave device according to (2), in which the load film is provided on the first electrode finger positioned outermost in the arrangement direction. (17) The elastic wave device according to (16), in which the protective film includes a first protective film provided on the first main surface of the piezoelectric layer to cover the load film and the IDT electrode, and in which a region overlapping the first electrode finger positioned outermost in the arrangement direction has a portion where the load film is provided but the first protective film is not provided, and a portion where the first protective film is provided but the load film is not provided, in a region overlapping the first electrode finger positioned outermost in the arrangement direction. (18) The elastic wave device according to (16) or (17), wherein the protective film includes a first protective film provided on the first main surface of the piezoelectric layer to cover the load film and the IDT electrode, and the load film has a protruding portion that protrudes beyond an upper surface of the first protective film.(19) The elastic wave device according to (16) or (17), wherein the protective film includes a first protective film provided on the first main surface of the piezoelectric layer to cover the load film and the IDT electrode, and an upper surface of the load film is provided in the same plane as an upper surface of the first protective film. (20) The elastic wave device according to (2), wherein the protective film includes a first protective film provided on the first main surface of the piezoelectric layer to cover the IDT electrode, and a second protective film provided on the second main surface of the piezoelectric layer, wherein the load film is provided on the second main surface of the piezoelectric layer, and the second protective film covers the load film. (21) The elastic wave device according to (2), wherein the protective film includes a first protective film provided on the first main surface of the piezoelectric layer and covering the IDT electrode, and a second protective film provided on the second main surface of the piezoelectric layer, wherein the load film faces the second main surface of the piezoelectric layer and is spaced apart from the second main surface, and wherein the second protective film is provided between the second main surface of the piezoelectric layer and the load film and covers the surface of the load film opposite the piezoelectric layer. (22) The elastic wave device according to (1), wherein the load film is provided outside the second main surface of the piezoelectric layer in the first direction. (23) The elastic wave device according to any one of (1) to (22), wherein the IDT electrode is provided on both the first main surface and the second main surface of the piezoelectric layer. (24) An elastic wave filter device including at least one resonator connected, wherein the resonator is the elastic wave device according to (1). (25) The acoustic wave filter device according to (24), further comprising: an input terminal, an output terminal, a series arm connecting the input terminal and the output terminal; and a parallel arm connecting a node of the series arm and ground; wherein the at least one resonator is a plurality of resonators, including a series arm resonator provided in the series arm and a parallel arm resonator provided in the parallel arm; and wherein the load film of the series arm resonator has a different configuration from the load film of the parallel arm resonator.(26) The elastic wave device according to any one of (1) to (23), wherein the load film includes a first extension portion, a second extension portion, a third extension portion, and a fourth extension portion, wherein the first extension portion is provided in a region overlapping with the first electrode finger located outermost in the arrangement direction and extends along the extension direction of the first electrode finger, the second extension portion is provided in a region overlapping with the second electrode finger located outermost on the opposite side of the arrangement direction and extends along the extension direction of the second electrode finger, the third extension portion is connected to one end side of the extension direction of the first extension portion and the second extension portion and extends in the arrangement direction, and the fourth extension portion is connected to the other end side of the extension direction of the first extension portion and the second extension portion and extends in the arrangement direction. (27) The elastic wave device according to any one of (1) to (23), wherein the load film includes a first extension portion, a second extension portion, a third extension portion, and a fourth extension portion, wherein the first extension portion is provided in a region overlapping with the first electrode finger located outermost in the arrangement direction and extends along the extension direction of the first electrode finger, the second extension portion is provided in a region overlapping with the second electrode finger located outermost on the opposite side of the arrangement direction and extends along the extension direction of the second electrode finger, the third extension portion is arranged at one end side of the extension direction of the first extension portion and the second extension portion and extends in the arrangement direction, and the fourth extension portion is arranged at the other end side of the extension direction of the first extension portion and the second extension portion and extends in the arrangement direction, and at least one of the third extension portion and the fourth extension portion is arranged spaced apart from the first extension portion and the second extension portion.(28) An elastic wave device comprising: a piezoelectric layer having a first main surface and a second main surface opposite the first main surface; an IDT electrode provided on the first main surface of the piezoelectric layer and including a plurality of electrode fingers arranged in a predetermined direction; a support member facing the second main surface of the piezoelectric layer; a protective film provided on at least one of the first and second main surfaces of the piezoelectric layer; and a load film provided in a region that is outward in the arrangement direction of the plurality of electrode fingers from a first electrode finger that is positioned outermost in the arrangement direction of the plurality of electrode fingers and does not overlap with the IDT electrode, wherein d / p is 0.5 or less, where d is a thickness of the piezoelectric layer and p is a center-to-center distance between adjacent electrode fingers, and L / p is 0.9 or less, where L is a distance between the first electrode finger and the load film in the arrangement direction of the plurality of electrode fingers. (29) The elastic wave device according to any one of (2) to (5) and (28), wherein the load film is formed of a material with a higher density than the protective film. (30) The elastic wave device according to any one of (2) to (5) and (28), wherein the load film is formed of a material having a lower density than the protective film. (31) The elastic wave device according to any one of (2) to (5) and (28) to (30), wherein the load film is formed of a material having a higher Young's modulus than the protective film. (32) The elastic wave device according to any one of (2) to (5) and (28), wherein the load film and the protective film are formed of the same material, and wherein the density of the load film is different from the density of the protective film. (33) The elastic wave device according to any one of (2) to (5) and (28) to (32), wherein the protective film is formed of silicon oxide. (34) The elastic wave device according to any one of (1) to (23) and (26) to (33), wherein the piezoelectric layer contains lithium niobate or lithium tantalate and has a 120°±10° rotated Y-cut or a 90°±10° rotated Y-cut. (35) The elastic wave device according to any one of (2) to (5) and (28) to (33), wherein the protective film includes a first protective film provided on the first main surface of the piezoelectric layer to cover the IDT electrode, and a second protective film provided on the second main surface of the piezoelectric layer. (36) The elastic wave device according to any one of (2) to (5) and (28) to (35), wherein the thickness of the protective film is thicker than the thickness of the IDT electrode.(37) The elastic wave device according to (35), wherein a value of A / B is 1-0.06 or more and 1+0.06 or less, where A is the total distance from the center of thickness of the piezoelectric layer to the top surface of the first protective film and B is the total distance from the center of thickness of the piezoelectric layer to the top surface of the second protective film. (38) The elastic wave device according to (35), wherein an upper surface of the first protective film and a lower surface of the second protective film are formed flat. (39) The elastic wave device according to any one of (1) to (23) and (26) to (38), wherein the material of the load film is at least one of carbon-doped silicon oxide, silicon oxide, silicon nitride, tantalum pentoxide, aluminum nitride, aluminum oxide, hafnium oxide, niobium pentoxide, and tungsten oxide. (40) The elastic wave device according to any one of (1) to (23) and (26) to (39), wherein the electrode width of the first electrode finger positioned outermost in the arrangement direction is smaller than the electrode width of the electrode finger positioned centrally in the arrangement direction, and the inter-electrode pitch between the first electrode finger and the electrode finger adjacent to the first electrode finger is smaller than the inter-electrode pitch of the plurality of electrode fingers positioned centrally in the arrangement direction. (41) The elastic wave device according to any one of (1) to (23) and (26) to (39), wherein the electrode width of the first electrode finger positioned outermost in the arrangement direction is larger than the electrode width of the electrode finger positioned centrally in the arrangement direction, and the inter-electrode pitch between the first electrode finger and the electrode finger adjacent to the first electrode finger is larger than the inter-electrode pitch of the plurality of electrode fingers positioned centrally in the arrangement direction. (42) The elastic wave device according to any one of (1) to (23) and (26) to (41), wherein d / p is 0.24 or less. (43) The acoustic wave device according to any one of (1) to (23) and (26) to (42), wherein, when viewed in the electrode finger orthogonal direction, a region where adjacent electrode fingers overlap each other and a region between centers of the adjacent electrode fingers in the electrode finger orthogonal direction is an excitation region, and where MR is a metallization ratio of the electrode fingers to the excitation region, and MR satisfies MR≦1.75(d / p)+0.075. (44) The acoustic wave device according to any one of (1) to (23) and (26) to (43), wherein the piezoelectric layer is made of lithium tantalate or lithium niobate.(45) The elastic wave device according to any one of (1) to (23) and (26) to (44), 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 formula (1), formula (2), or formula (3): (0°±10°, 0° to 20°, any ψ) ... formula (1) (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 ]~180°) ...Formula (2) (0°±10°, [180°-30°(1-(ψ-90) ２ / 8100) １／２] to 180°, any ψ) ...Equation (3) (46) The elastic wave device according to any one of (1) to (23) and (26) to (45), wherein the acoustic reflecting portion is a cavity, and the support member and the piezoelectric layer are arranged so that a part of the support member and a part of the piezoelectric layer face each other with the cavity in between. (47) The elastic wave device according to any one of (1) to (23) and (26) to (45), wherein the acoustic reflecting portion is an acoustic reflecting film including a high acoustic impedance layer having a relatively high acoustic impedance and a low acoustic impedance layer having a relatively low acoustic impedance, and the support member and the piezoelectric layer are arranged so that at least a part of the support member and at least a part of the piezoelectric layer face each other with the acoustic reflecting film in between. (48) The elastic wave device according to any one of (1) to (23) and (26) to (47), wherein, when a distance between one side surface of the load film and a midpoint of the first electrode finger in the width direction is defined as a movement amount G of the load film in the arrangement direction of the plurality of electrode fingers, a ratio G / p of the movement amount G of the load film to a center-to-center distance p between adjacent electrode fingers satisfies -0.2≦G / p≦+0.2. (49) The elastic wave device according to any one of (1) to (23) and (26) to (48), wherein a width of the load film in the arrangement direction varies along a direction orthogonal to the arrangement direction. (50) The elastic wave device according to (47), wherein the IDT electrode is formed on the piezoelectric layer so as to be embedded in the high acoustic impedance layer or the low acoustic impedance layer, and the material of the load film is different from that of the layer in which the IDT electrode is embedded.

[0279] 10, 10A, 10B, 10C, 10D, 10E, 10F, 10G, 10H, 10I, 10J, 10K, 10L, 10M, 10N, 10O, 10P, 10Q, 10R, 10S, 10T, 10U, 10V elastic wave device 11 supporting substrate 12 bottom portion 13 wall portion 14 capacitor portion 20, 201 piezoelectric layer 20a, 201a first principal surface 20b, 201b second principal surface 30 IDT electrodes 31, 32 electrode finger 31a first electrode finger 32a second electrode finger 33, 34 busbar electrode 41 first protective film 42 second protective film 50 load film 50A Upper load film 50B Lower load film 51 First extension 52 Second extension 53 Outer load film 54 Lower first extension

Claims

1. An elastic wave device comprising: a piezoelectric layer having a first main surface and a second main surface facing the first main surface in a first direction; an IDT electrode provided on at least one of the first and second main surfaces of the piezoelectric layer, the IDT electrode including a plurality of electrode fingers arranged in a predetermined direction; a support member facing the second main surface of the piezoelectric layer and having an acoustic reflector on the second main surface side of the piezoelectric layer; and a load film provided in a region that overlaps in a planar view from the first direction with at least one end of the IDT electrode in the arrangement direction of the plurality of electrode fingers, the end including a first electrode finger that is positioned outermost in the arrangement direction of the plurality of electrode fingers, wherein d is a thickness of the piezoelectric layer and p is a center-to-center distance between adjacent electrode fingers, and d / p is 0.5 or less.

2. The acoustic wave device according to claim 1, further comprising a protective film provided on at least one of the first main surface and the second main surface of the piezoelectric layer.

3. The elastic wave device according to claim 2, wherein the protective film comprises a first protective film provided on the first main surface of the piezoelectric layer, covering the IDT electrode, and the load film is provided on the first protective film.

4. The elastic wave device of claim 3, wherein in a region overlapping with the first electrode finger located outermost in the arrangement direction of the plurality of electrode fingers, a step is formed between a portion where the first protective film is provided but the load film is not provided, and a portion where the load film and the first protective film are laminated.

5. The elastic wave device according to claim 2, wherein the protective film comprises a first protective film covering the IDT electrode and provided on the first main surface of the piezoelectric layer, and a second protective film provided on the second main surface of the piezoelectric layer, and the load film is provided on the surface of the second protective film facing the support member.

6. The acoustic wave device according to claim 1, wherein the load film is provided between the first main surface of the piezoelectric layer and the first electrode finger in the first direction of the piezoelectric layer.

7. The elastic wave device according to claim 1, wherein the load film is provided in a region overlapping the first electrode finger and an electrode finger adjacent to the first electrode finger.

8. An elastic wave device according to any one of claims 1 to 7, wherein the number of the first electrode fingers, the electrode fingers adjacent to the first electrode fingers, the second electrode fingers positioned outermost on the opposite side of the arrangement direction, and the electrode fingers adjacent to the second electrode fingers that overlap the load film is six or less.

9. An elastic wave device as claimed in any one of claims 1 to 8, wherein the load film has a first extension portion provided in a region overlapping with the first electrode finger, and an outer load film provided in a region that is outside the first extension portion in the arrangement direction and does not overlap with the IDT electrode.

10. The elastic wave device of claim 2, wherein the protective film comprises a first protective film covering the IDT electrode and provided on the first main surface of the piezoelectric layer, and a second protective film provided on the second main surface of the piezoelectric layer, and the load film includes an upper load film provided on the first protective film, and a lower load film provided on the surface of the second protective film facing the support member.

11. The acoustic wave device according to claim 10, wherein a width of the upper load film is different from a width of the lower load film.

12. The elastic wave device according to claim 10 or 11, wherein the upper load film has a thickness smaller than that of the lower load film.

13. The elastic wave device according to any one of claims 10 to 12, wherein a material of the upper load film is different from a material of the lower load film.

14. The acoustic wave device according to claim 2, wherein the protective film has a thickness smaller than a thickness of the piezoelectric layer.

15. The elastic wave device according to any one of claims 10 to 13, wherein the Young's modulus of at least one of the upper load film and the lower load film is 50 GPa or more.

16. The acoustic wave device according to claim 2, wherein the load film is provided on the first electrode fingers that are positioned outermost in the arrangement direction.

17. The elastic wave device according to claim 16, wherein the protective film includes a first protective film provided on the first main surface of the piezoelectric layer to cover the load film and the IDT electrode, and in a region overlapping with the first electrode finger positioned outermost in the arrangement direction, the protective film has a portion where the load film is provided but the first protective film is not provided, and a portion where the first protective film is provided but the load film is not provided.

18. The elastic wave device according to claim 16 or 17, wherein the protective film includes a first protective film provided on the first main surface of the piezoelectric layer, covering the load film and the IDT electrode, and the load film has a protruding portion that protrudes above an upper surface of the first protective film.

19. The elastic wave device according to claim 16 or 17, wherein the protective film includes a first protective film provided on the first main surface of the piezoelectric layer, covering the load film and the IDT electrode, and an upper surface of the load film is provided in the same plane as an upper surface of the first protective film.

20. The elastic wave device of claim 2, wherein the protective film includes a first protective film provided on the first main surface of the piezoelectric layer and covering the IDT electrode, and a second protective film provided on the second main surface of the piezoelectric layer, the load film is provided on the second main surface of the piezoelectric layer, and the second protective film covers the load film.

21. The elastic wave device of claim 2, wherein the protective film includes a first protective film provided on the first main surface of the piezoelectric layer and covering the IDT electrode, and a second protective film provided on the second main surface of the piezoelectric layer, the load film faces the second main surface of the piezoelectric layer and is spaced apart from the second main surface, and the second protective film is provided between the second main surface of the piezoelectric layer and the load film, and covers the surface of the load film opposite the piezoelectric layer.

22. The acoustic wave device according to claim 1, wherein the load film is provided outside the second main surface of the piezoelectric layer in the first direction.

23. The acoustic wave device according to claim 1, wherein the IDT electrode is provided on both the first principal surface and the second principal surface of the piezoelectric layer.

24. An elastic wave filter device comprising at least one connected resonator, the resonator being the elastic wave device defined in claim 1.

25. The elastic wave filter device according to claim 24, comprising: an input terminal, an output terminal, a series arm connecting the input terminal and the output terminal, and a parallel arm connecting a node of the series arm and ground, wherein the at least one resonator is a plurality of resonators including a series arm resonator provided in the series arm and a parallel arm resonator provided in the parallel arm, and the load film of the series arm resonator has a different configuration from the load film of the parallel arm resonator.

26. The elastic wave device according to any one of claims 1 to 23, wherein the load film includes a first extension portion, a second extension portion, a third extension portion, and a fourth extension portion, wherein the first extension portion is provided in a region overlapping with the first electrode finger located at the outermost position in the arrangement direction and extends along the extension direction of the first electrode finger, the second extension portion is provided in a region overlapping with the second electrode finger located at the outermost position on the opposite side of the arrangement direction and extends along the extension direction of the second electrode finger, the third extension portion is connected to one end side of the extension direction of the first extension portion and the second extension portion and extends in the arrangement direction, and the fourth extension portion is connected to the other end side of the extension direction of the first extension portion and the second extension portion and extends in the arrangement direction.

27. The elastic wave device according to any one of claims 1 to 23, wherein the load film includes a first extension portion, a second extension portion, a third extension portion, and a fourth extension portion, wherein the first extension portion is provided in a region overlapping with the first electrode finger located outermost in the arrangement direction and extends along the extension direction of the first electrode finger, the second extension portion is provided in a region overlapping with the second electrode finger located outermost on the opposite side of the arrangement direction and extends along the extension direction of the second electrode finger, the third extension portion is arranged at one end side of the extension direction of the first extension portion and the second extension portion and extends in the arrangement direction, the fourth extension portion is arranged at the other end side of the extension direction of the first extension portion and the second extension portion and extends in the arrangement direction, and at least one of the third extension portion and the fourth extension portion is arranged spaced apart from the first extension portion and the second extension portion.

28. An elastic wave device comprising: a piezoelectric layer having a first main surface and a second main surface opposite to the first main surface; an IDT electrode provided on the first main surface of the piezoelectric layer and including a plurality of electrode fingers arranged in a predetermined direction; a support member facing the second main surface of the piezoelectric layer; a protective film provided on at least one of the first and second main surfaces of the piezoelectric layer; and a load film provided in a region that is outboard of a first electrode finger that is positioned outermost in an arrangement direction of the plurality of electrode fingers among the plurality of electrode fingers and does not overlap with the IDT electrode, wherein d is a thickness of the piezoelectric layer and p is a center-to-center distance between adjacent electrode fingers, d / p is 0.5 or less, and L / p is 0.9 or less when L is a distance between the first electrode finger and the load film in the arrangement direction of the plurality of electrode fingers.

29. The acoustic wave device according to any one of claims 2 to 5 and claim 28, wherein the load film is formed of a material having a higher density than the protective film.

30. The elastic wave device according to any one of claims 2 to 5 and claim 28, wherein the load film is formed of a material having a lower density than the protective film.

31. The elastic wave device according to any one of claims 2 to 5 and claims 28 to 30, wherein the load film is made of a material having a higher Young's modulus than the protective film.

32. The elastic wave device according to any one of claims 2 to 5 and claim 28, wherein the load film and the protective film are formed of the same material, and the density of the load film is different from the density of the protective film.

33. The acoustic wave device according to any one of claims 2 to 5 and claims 28 to 32, wherein the protective film is made of silicon oxide.

34. The elastic wave device according to any one of claims 1 to 23 and claims 26 to 33, wherein the piezoelectric layer contains lithium niobate or lithium tantalate and is a 120°±10° rotated Y-cut or a 90°±10° rotated Y-cut.

35. An elastic wave device as claimed in any one of claims 2 to 5 and claims 28 to 33, wherein the protective film comprises a first protective film covering the IDT electrode and provided on the first main surface of the piezoelectric layer, and a second protective film provided on the second main surface of the piezoelectric layer.

36. The acoustic wave device according to any one of claims 2 to 5 and claims 28 to 35, wherein the protective film has a thickness greater than a thickness of the IDT electrode.

37. The elastic wave device according to claim 35, wherein the total distance from the center of thickness of the piezoelectric layer to the top surface of the first protective film is A and the total distance from the center of thickness of the piezoelectric layer to the top surface of the second protective film is B, in which A / B is equal to or greater than 1-0.06 and equal to or less than 1+0.

06.

38. The acoustic wave device according to claim 35, wherein an upper surface of the first protective film and a lower surface of the second protective film are formed flat.

39. The elastic wave device according to any one of claims 1 to 23 and claims 26 to 38, wherein the material of the load film is at least one of carbon-doped silicon oxide, silicon oxide, silicon nitride, tantalum pentoxide, aluminum nitride, aluminum oxide, hafnium oxide, niobium pentoxide, and tungsten oxide.

40. An elastic wave device as claimed in any one of claims 1 to 23 and claims 26 to 39, wherein the electrode width of the first electrode finger located at the outermost position in the arrangement direction is smaller than the electrode width of the electrode finger located in the center in the arrangement direction, and the inter-electrode pitch between the first electrode finger and the electrode finger adjacent to the first electrode finger is smaller than the inter-electrode pitch of the multiple electrode fingers located in the center in the arrangement direction.

41. An elastic wave device as described in any one of claims 1 to 23 and claims 26 to 39, wherein the electrode width of the first electrode finger located at the outermost side in the arrangement direction is larger than the electrode width of the electrode finger located in the center in the arrangement direction, and the inter-electrode pitch between the first electrode finger and the electrode finger adjacent to the first electrode finger is larger than the inter-electrode pitch of the multiple electrode fingers located in the center in the arrangement direction.

42. The elastic wave device according to any one of claims 1 to 23 and claims 26 to 41, wherein d / p is 0.24 or less.

43. An elastic wave device as claimed in any one of claims 1 to 23 and claims 26 to 42, wherein, when viewed from the electrode finger orthogonal direction, the region where adjacent electrode fingers overlap each other and the region between the centers of adjacent electrode fingers in the electrode finger orthogonal direction is an excitation region, and when the metallization ratio of the electrode fingers to the excitation region is MR, MR satisfies MR≦1.75(d / p)+0.

075.

44. The acoustic wave device according to any one of claims 1 to 23 and claims 26 to 43, wherein the piezoelectric layer is made of lithium tantalate or lithium niobate.

45. The elastic wave device according to any one of claims 1 to 23 and claims 26 to 44, 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 formula (1), formula (2), or formula (3): (0°±10°, 0° to 20°, any ψ) ... formula (1) (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 ]~180°) ...Formula (2) (0°±10°, [180°-30°(1-(ψ-90) ２ / 8100) １／２ ] ~ 180°, any ψ) ... Equation (3) 46. ​​An elastic wave device as claimed in any one of claims 1 to 23 and claims 26 to 45, wherein the acoustic reflection portion is a hollow portion, and the support member and the piezoelectric layer are arranged so that a portion of the support member and a portion of the piezoelectric layer face each other with the hollow portion in between.

47. An elastic wave device as claimed in any one of claims 1 to 23 and claims 26 to 45, wherein the acoustic reflection portion is an acoustic reflection film including a high acoustic impedance layer having a relatively high acoustic impedance and a low acoustic impedance layer having a relatively low acoustic impedance, and the support member and the piezoelectric layer are arranged such that at least a portion of the support member and at least a portion of the piezoelectric layer face each other across the acoustic reflection film.

48. The elastic wave device according to any one of claims 1 to 23 and claims 26 to 47, wherein, when a distance between one side surface of the load film and a midpoint in a width direction of the first electrode finger in an arrangement direction of the plurality of electrode fingers is defined as a movement amount G of the load film, a ratio G / p of the movement amount G of the load film to a center-to-center distance p between adjacent electrode fingers satisfies -0.2≦G / p≦+0.

2.

49. The elastic wave device according to any one of claims 1 to 23 and claims 26 to 48, wherein the width of the load film in the arrangement direction varies along a direction perpendicular to the arrangement direction.

50. The acoustic wave device of claim 47, wherein the IDT electrode is formed on the piezoelectric layer so as to be embedded in the high acoustic impedance layer or the low acoustic impedance layer, and the material of the load film is different from the layer in which the IDT electrode is embedded.

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