Elastic wave device and composite filter device

Abstract

This makes it possible to provide an elastic wave device that can be set to a wide frequency band and that can suppress unwanted waves. This elastic wave device (1) is provided with: a silicon single crystal substrate (3) having a main surface (first main surface (3a)); a piezoelectric layer provided directly or indirectly on the main surface of the silicon single crystal substrate (3); and an IDT electrode (8) provided on the piezoelectric layer and having a plurality of electrode fingers (a plurality of first electrode fingers (18) and a plurality of second electrode fingers (19)). The piezoelectric layer is a lithium niobate layer (7). In the main surface of the silicon single crystal substrate (3), the plane orientation is (111). When the Euler angles in the main surface of the silicon single crystal substrate (3) are (phi, theta, psi), the psi in the Euler angles of the silicon single crystal substrate (3) is-30 DEG lt. Psi lt; 30 degrees.

Description

Technical Field

[0001] The present invention relates to an elastic wave device and a composite filter device. Background Art

[0002] Traditionally, elastic wave devices have been widely used in filters for mobile phones and other applications. Patent Document 1 below discloses an example of an elastic wave device. In this elastic wave device, IDT (Interdigital Transducer) electrodes are provided on a composite substrate. The composite substrate is formed by laminating a silicon substrate and a lithium tantalate substrate. The silicon substrate has a (111) surface orientation. This elastic wave device achieves suppression of bulk wave spurious emission.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2017 / 209131 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] The elastic wave device described in Patent Document 1 uses lithium tantalate as the piezoelectric layer. This makes it difficult to fully expand the frequency band between the resonant frequency and the antiresonant frequency. On the other hand, expanding this frequency band makes it difficult to suppress spurious emissions in the elastic wave device described in Patent Document 1. In other words, the elastic wave device described in Patent Document 1 cannot achieve both wide bandwidth and unwanted wave suppression.

[0008] An object of the present invention is to provide an elastic wave device and a composite filter device that can provide a wide bandwidth and suppress unnecessary waves.

[0009] Technical solutions to solve problems

[0010] In a broad aspect of the elastic wave device involved in the present invention, it comprises: a silicon single crystal substrate having a main surface; a piezoelectric layer directly or indirectly arranged on the main surface of the silicon single crystal substrate; and an IDT electrode arranged on the piezoelectric layer and having a plurality of electrode fingers, wherein the piezoelectric layer is a lithium niobate layer, and the surface orientation on the main surface of the silicon single crystal substrate is (111), and when the Euler angles in the main surface of the silicon single crystal substrate are set to (φ, θ, ψ), ψ in the Euler angles of the silicon single crystal substrate is -30°<ψ<30°.

[0011] In other broad aspects of the elastic wave device according to the present invention, the device comprises: a silicon single crystal substrate having a main surface; a piezoelectric layer directly or indirectly provided on the main surface of the silicon single crystal substrate; and an IDT electrode provided on the piezoelectric layer and having a plurality of electrode fingers, wherein the main surface of the silicon single crystal substrate has a plane orientation of (111), the piezoelectric layer has an X-axis, a Y-axis, and a Z-axis as crystal axes, the piezoelectric layer is a Y-cut X-propagating lithium niobate layer, and when one of the directions in which the X-axis of the piezoelectric layer extends is set as the +X direction, the angle formed by the +X direction and the [1-10] direction in the silicon single crystal substrate is greater than or equal to -15° and less than or equal to 15°.

[0012] The composite filter device according to the present invention is mounted on a mounting substrate, wherein the composite filter device comprises: a common connection terminal; and a plurality of filter devices commonly connected to the common connection terminal, at least one of the plurality of filter devices is a first filter device including an elastic wave device constructed according to the present invention, and at least one of the plurality of filter devices is a second filter device having a second piezoelectric layer, the first filter device and the second filter device are arranged on the mounting substrate as independent components, and the second piezoelectric layer is a lithium tantalate layer.

[0013] Effects of the Invention

[0014] According to the present invention, it is possible to provide an elastic wave device and a composite filter device that can provide a wide bandwidth and suppress unnecessary waves. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic front cross-sectional view showing a portion of the elastic wave device according to the first embodiment of the present invention.

[0016] Figure 2 It is a schematic plan view of the elastic wave device according to the first embodiment of the present invention.

[0017] Figure 3 Schematic diagram showing the definition of crystal axes of silicon.

[0018] Figure 4 is a schematic diagram showing the (111) plane of silicon.

[0019] Figure 5 This is a diagram showing the relationship between ψ in the Euler angles of the first main surface of a silicon single crystal substrate and the phase of a high-order mode at 7000 MHz.

[0020] Figure 6 This is a projection image of a Y-cut X-propagation lithium niobate single crystal layer observed from

[0001] .

[0021] Figure 7This is a diagram showing the relationship between the plane orientation of the main surface of a silicon single crystal substrate, the third Euler angle, and the phase of a high-order mode at 7000 MHz.

[0022] Figure 8 This is a schematic front cross-sectional view showing a portion of an elastic wave device according to a modified example of the first embodiment of the present invention.

[0023] Figure 9 It is a schematic plan view of an elastic wave device according to a second embodiment of the present invention.

[0024] Figure 10 It is a schematic plan view of an elastic wave device according to a third embodiment of the present invention.

[0025] Figure 11 It is a schematic plan view of an elastic wave device according to a fourth embodiment of the present invention.

[0026] Figure 12 FIG. 1 is a schematic cross-sectional view of an elastic wave device according to a fifth embodiment of the present invention, taken along the direction in which the electrode fingers extend. FIG.

[0027] Figure 13 This is a circuit diagram of a filter device according to a sixth embodiment of the present invention.

[0028] Figure 14 It is a schematic diagram of a composite filter device according to a sixth embodiment of the present invention.

[0029] Figure 15 It is a schematic front cross-sectional view showing a structure in which a composite filter device according to a sixth embodiment of the present invention is mounted on a mounting substrate.

[0030] Figure 16 It is a schematic diagram of a composite filter device according to a seventh embodiment of the present invention. DETAILED DESCRIPTION

[0031] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings to clarify the present invention.

[0032] In addition, it should be noted that each embodiment described in this specification is an example, and some structures can be replaced or combined among different embodiments.

[0033] Figure 1 This is a schematic front cross-sectional view showing a portion of the elastic wave device according to the first embodiment of the present invention. Figure 2 : is a schematic top view of the elastic wave device according to the first embodiment. Figure 1 It is along Figure 2 Schematic cross-sectional view of line II in FIG. Figure 2In the figure, the dielectric film described later is omitted. Figure 2 The same applies to other schematic top views.

[0034] like Figure 1 As shown, elastic wave device 1 includes piezoelectric substrate 2. Piezoelectric substrate 2 includes silicon single crystal substrate 3, intermediate layer 4, and lithium niobate layer 7 as a piezoelectric layer. Piezoelectric substrate 2 is a substrate having piezoelectricity.

[0035] In this embodiment, the intermediate layer 4 is a laminate. More specifically, the intermediate layer 4 includes a first layer 5 and a second layer 6. In the piezoelectric substrate 2, the first layer 5 is provided on a silicon single crystal substrate 3. The second layer 6 is provided on the first layer 5. The lithium niobate layer 7 is provided on the second layer 6.

[0036] The silicon single crystal substrate 3 has a first principal surface 3a and a second principal surface 3b. The first principal surface 3a and the second principal surface 3b are opposed to each other. Of the first and second principal surfaces 3a, the first principal surface 3a is the principal surface facing the lithium niobate layer 7. Furthermore, the first principal surface 3a is the principal surface of the silicon single crystal substrate 3 in the present invention.

[0037] Figure 3 Schematic diagram showing the definition of crystal axes of silicon. Figure 4 is a schematic diagram showing the (111) plane of silicon.

[0038] like Figure 3 As shown in FIG. 1 , the silicon single crystal has a diamond structure. In this specification, the crystal axis of the silicon constituting the silicon single crystal substrate 3 is set to [X Si , Y Si , Z Si In silicon, due to the symmetry of the crystal structure, X Si Axis, Y Si Axis and Z Si The axes are equivalent.

[0039] In this embodiment, the surface orientation of the first main surface 3a of the silicon single crystal substrate 3 is (111). The so-called surface orientation is (111), which means that in the crystal structure of silicon having a diamond structure, the surface is cut on the (111) plane orthogonal to the crystal axis represented by the Miller index

[111] . That is, the first main surface 3a is the (111) plane. In addition, the (111) plane is Figure 4 The (111) plane has three-fold symmetry within the plane, and when rotated 120°, it becomes an equivalent crystal structure. In this specification, the (111) plane also includes crystallographically equivalent planes.

[0040] When the Euler angles on the first principal surface 3a of the silicon single crystal substrate 3 are represented by (φ, θ, ψ), φ is -45°. θ, expressed to the second decimal place, is -54.73°. Furthermore, in this embodiment, ψ satisfies the condition -30°<ψ<30°. In this specification, the angle corresponding to φ is referred to as the first Euler angle, the angle corresponding to θ is referred to as the second Euler angle, and the angle corresponding to ψ is referred to as the third Euler angle.

[0041] Silicon nitride and silicon oxide are used as materials for intermediate layer 4. Specifically, silicon nitride is used as the material for first layer 5. Silicon oxide is used as the material for second layer 6. In elastic wave device 1, the composition of silicon nitride is Si3N4. The ratio of Si to N in silicon nitride is not limited to 3:4. For example, silicon nitride can also be composed of SiN. Meanwhile, the composition of silicon oxide is SiO2. The ratio of Si to O in silicon oxide is not limited to 1:2.

[0042] In the present invention, the intermediate layer 4 may be a single-layer dielectric layer. In this case, silicon nitride or silicon oxide may be used as the material of the single-layer intermediate layer 4. However, the material of the intermediate layer 4 is not limited to the above.

[0043] A lithium niobate layer 7 is provided on the intermediate layer 4. That is, in this embodiment, the lithium niobate layer 7 is indirectly provided on the first main surface 3a of the silicon single crystal substrate 3 via the intermediate layer 4. Alternatively, the intermediate layer 4 may not be provided. Alternatively, the lithium niobate layer 7 may be directly provided on the first main surface 3a of the silicon single crystal substrate 3.

[0044] The lithium niobate layer 7 is a single crystal layer. The lithium niobate layer 7 has X, Y, and Z axes as crystal axes. Furthermore, the lithium niobate layer 7 has a front side and a negative side. The front side and negative side are surfaces determined by the polarization direction of the lithium niobate layer 7. The front side is the surface of the lithium niobate layer 7 with a positive polarization direction. The negative side is the surface of the lithium niobate layer 7 with a negative polarization direction.

[0045] The lithium niobate layer 7 is a Y-cut X-propagation lithium niobate single crystal layer. More specifically, the cut angle of the lithium niobate layer 7 is 30°Y. When the Euler angle in the lithium niobate layer 7 is set to (φ p ,θ p , ψ p ), in this embodiment, the Euler angles of lithium niobate layer 7 are (0°, 120°, 0°). Furthermore, the cut angles and Euler angles of lithium niobate layer 7 are not limited to those described above. Lithium niobate layer 7 does not necessarily need to be a Y-cut, X-propagation lithium niobate single crystal layer.

[0046] like Figure 1As shown, an IDT electrode 8 is provided on the lithium niobate layer 7. Applying an AC voltage to the IDT electrode 8 excites elastic waves. Furthermore, since the lithium niobate layer 7 is a Y-cut, X-propagating lithium niobate single crystal layer, SH waves can be appropriately excited as the main mode.

[0047] like Figure 2 As shown, a pair of reflectors 14A and 14B are provided on lithium niobate layer 7, on either side of IDT electrode 8 in the direction of elastic wave propagation. Each reflector has multiple reflector electrode fingers 14c. The elastic wave device 1 of this embodiment is a surface acoustic wave resonator. The elastic wave device of the present invention can be used in, for example, filter devices and multiplexers.

[0048] In this embodiment, the IDT electrode 8, the reflectors 14A, and the reflectors 14B are provided on the negative surface of the lithium niobate layer 7. However, the surface on which the IDT electrode 8, the reflectors 14A, and the reflectors 14B are provided is not limited to the negative surface.

[0049] IDT electrode 8 includes a pair of bus bars and a plurality of electrode fingers. Specifically, the pair of bus bars is a first bus bar 16 and a second bus bar 17. First bus bar 16 and second bus bar 17 are opposed to each other. Specifically, the plurality of electrode fingers is a plurality of first electrode fingers 18 and a plurality of second electrode fingers 19. One end of each of the plurality of first electrode fingers 18 is connected to the first bus bar 16. One end of each of the plurality of second electrode fingers 19 is connected to the second bus bar 17. The plurality of first electrode fingers 18 and the plurality of second electrode fingers 19 are interlaced with each other. The first electrode fingers 18 and the second electrode fingers 19 are connected to different potentials.

[0050] Hereinafter, the first electrode fingers 18 and the second electrode fingers 19 may be referred to simply as electrode fingers. In this embodiment, the electrode finger extending direction and the elastic wave propagation direction are orthogonal to each other, assuming that the direction in which the plurality of electrode fingers extend is the electrode finger extending direction.

[0051] like Figure 1 As shown, each electrode finger of the IDT electrode 8 has a first surface 8a, a second surface 8b, and a side surface 8c. The first surface 8a and the second surface 8b are opposite to each other in the thickness direction. Of the first surface 8a and the second surface 8b, the second surface 8b is the surface on the side of the lithium niobate layer 7. The side surface 8c is connected to the first surface 8a and the second surface 8b. When the angle formed by the second surface 8b and the side surface 8c is defined as the inclination angle, in this embodiment, the inclination angle is 80°. However, the inclination angle is not limited to the above.

[0052] IDT electrode 8 comprises a stacked metal film. More specifically, in this stacked metal film, a Ti layer, an AlCu layer, and a Ti layer are stacked in this order. Reflectors 14A and 14B also comprise the same material as IDT electrode 8. However, the materials of IDT electrode 8, reflector 14A, and reflector 14B are not limited to the above. Alternatively, IDT electrode 8, reflector 14A, and reflector 14B may comprise a single layer of metal film.

[0053] In elastic wave device 1, when the wavelength defined by the electrode finger pitch of IDT electrode 8 is λ, the thickness of lithium niobate layer 7 is less than 1λ. The electrode finger pitch is the distance between the centers of adjacent first electrode fingers 18 and second electrode fingers 19 in the direction of elastic wave propagation. Specifically, when the electrode finger pitch is p, λ = 2p.

[0054] like Figure 1 As shown, a dielectric film 15 is provided on the lithium niobate layer 7 so as to cover the IDT electrode 8. This prevents damage to the IDT electrode 8. Materials for the dielectric film 15 include, for example, silicon oxide, silicon nitride, or silicon oxynitride. However, the materials for the dielectric film 15 are not limited to the above.

[0055] When silicon oxide is used as the material for dielectric film 15 , the absolute value of the temperature coefficient of frequency (TCF) of elastic wave device 1 can be reduced. This improves the frequency-temperature characteristics of elastic wave device 1 . On the other hand, when silicon nitride is used as the material for dielectric film 15 , the moisture resistance of elastic wave device 1 can be improved. However, dielectric film 15 need not be provided.

[0056] This embodiment is characterized by the following structures. 1) A lithium niobate layer 7 is provided on the first principal surface 3a of the silicon single crystal substrate 3. 2) The plane orientation of the first principal surface 3a is (111), and ψ in the Euler angles (-45°, -54.73°, ψ) of the first principal surface 3a satisfies -30° < ψ < 30°. In the structure 1) above, when the lithium niobate layer 7 is used as the piezoelectric layer of the piezoelectric substrate 2, the frequency band between the resonant frequency and the antiresonant frequency of the elastic wave device 1 can be expanded compared to the case where a lithium tantalate layer is used as the piezoelectric layer. In other words, the elastic wave device 1 can have a wide frequency band.

[0057] As in the structure 2) above, by setting the Euler angles (-45°, -54.73°, ψ) of the first main surface 3 a to -30° < ψ < 30°, it is possible to suppress unwanted waves when the lithium niobate layer 7 is used as the piezoelectric layer. The effect of suppressing unwanted waves in this embodiment is described in detail below.

[0058] In an elastic wave device with the same layer structure as in the first embodiment, the phase of unwanted waves was measured each time ψ in the Euler angles (-45°, -54.73°, ψ) of the first principal surface of a silicon single crystal substrate was varied. Specifically, the phase of the high-order mode around 7000 MHz was measured. The design parameters of this elastic wave device are as follows.

[0059] Silicon single crystal substrate: material…Si single crystal, thickness…50λ, plane orientation of the first main surface…(111), Euler angles in the first main surface…(-45°, -54.73°, ψ), ψ in the Euler angles…is varied in increments of 5° within a range of greater than -60° and less than 60°.

[0060] Intermediate layer 1: Material…Si3N4, thickness…0.15λ

[0061] Intermediate layer 2: Material…SiO2, Thickness…0.15λ

[0062] Lithium niobate layer: Material… 30° Y-cut X-propagation LiNbO3 single crystal, Euler angles… (0°, 120°, 0°), surface with IDT electrode… negative

[0063] IDT electrode: Layer structure…Ti layer / AlCu layer / Ti layer from the lithium niobate layer side, thickness…0.002λ / 0.05λ / 0.006λ from the lithium niobate layer side, inclination angle of the electrode finger side…80°

[0064] Duty cycle of IDT electrode: 0.5

[0065] Wavelength λ: 1 μm

[0066] Dielectric film: Material: SiO2, thickness of the portion provided on the first surface of the IDT electrode finger: 0.01λ, thickness of the portion provided on the side surfaces of the IDT electrode finger: 0.005λ

[0067] Figure 5 This is a diagram showing the relationship between ψ in the Euler angles of the first main surface of a silicon single crystal substrate and the phase of a high-order mode at 7000 MHz.

[0068] like Figure 5 As shown, it can be seen that the phase of the high-order mode, which is an unnecessary wave, is small in the range of -30°<ψ<30°. As in the first embodiment, when ψ is -30°<ψ<30°, unnecessary waves can be suppressed.

[0069] Back to Figure 1The first principal surface 3a of the silicon single crystal substrate 3 of the elastic wave device 1 is a (111) plane. The lithium niobate layer 7 is a Y-cut, X-propagation lithium niobate single crystal layer. In this case, the ψ in the Euler angles (-45°, -54.73°, ψ) of the first principal surface 3a can be represented by the directions based on the crystal structures of the silicon single crystal substrate 3 and the lithium niobate layer 7. Details are described below.

[0070] Figure 6 This is a projection image of a Y-cut X-propagation lithium niobate single crystal layer observed from

[0001] .

[0071] Figure 6 The direction from the base end toward the tip end of the white arrow is the +X direction. The +X direction is one of the directions in which the X axis in the lithium niobate layer 7 extends. On the other hand, Figure 4 The direction from the base end toward the tip end indicated by the white arrow in FIG is the [1-10] direction in the silicon single crystal substrate 3. The angle formed by the +X direction in the lithium niobate layer 7 and the [1-10] direction in the silicon single crystal substrate 3 is equivalent to ψ in the Euler angles (-45°, -54.73°, ψ) of the first principal surface 3a.

[0072] In the first embodiment, lithium niobate layer 7 is used as the piezoelectric layer, and the angle formed between the +X direction of lithium niobate layer 7 and the [1-10] direction of silicon single crystal substrate 3 is greater than -30° and less than 30°. This allows elastic wave device 1 to have a wide bandwidth and suppress unwanted waves.

[0073] Furthermore, the phases of unwanted waves were compared when the plane orientation of the principal surface, corresponding to the first principal surface of the silicon single crystal substrate, was (111), (100), and (110). The phases of unwanted waves were measured when the third Euler angle, corresponding to ψ in the Euler angles (φ, θ, ψ), was varied by 5° within a range of -90° to 90° for the (111), (100), and (110) planes. Specifically, the phases of high-order modes near 7000 MHz were measured.

[0074] Figure 7 This is a diagram showing the relationship between the plane orientation of the main surface of a silicon single crystal substrate, the third Euler angle, and the phase of a high-order mode at 7000 MHz.

[0075] like Figure 7 As shown, when the plane orientation of the main surface of the silicon single crystal substrate is (111) and the third Euler angle is greater than -15° and less than 15°, harmonics as useless waves are suppressed compared to the case where the plane orientation is (110) and the case where it is (100).

[0076] Therefore, in Figure 1In the structure of the first embodiment shown, the third Euler angle ψ of the first principal surface 3a of the silicon single crystal substrate 3 is preferably -15° ≤ ψ ≤ 15°. Alternatively, the angle formed by the +X direction in the lithium niobate layer 7 and the [1-10] direction in the silicon single crystal substrate 3 is preferably not less than -15° and not more than 15°. This further suppresses unwanted waves.

[0077] Furthermore, the first layer 5 of the intermediate layer 4 in the first embodiment is a high-acoustic-velocity film serving as a high-acoustic-velocity material layer. A high-acoustic-velocity material layer is a layer with a relatively high acoustic velocity. More specifically, the acoustic velocity of the bulk wave propagating through the high-acoustic-velocity material layer is higher than the acoustic velocity of the elastic wave propagating through the piezoelectric layer. Furthermore, in the first embodiment, the piezoelectric layer is a lithium niobate layer 7. Examples of high-acoustic-velocity materials include piezoelectric materials such as aluminum nitride, lithium tantalate, lithium niobate, and quartz; ceramics such as alumina, sapphire, magnesium oxide, silicon nitride, silicon carbide, zirconium oxide, cordierite, mullite, steatite, forsterite, spinel, and Sialon; dielectrics such as aluminum oxide, silicon oxynitride, DLC (diamond-like carbon), and diamond; and semiconductors such as silicon, or materials primarily composed of the above materials. Furthermore, the spinel mentioned above includes an aluminum compound containing one or more elements selected from Mg, Fe, Zn, and Mn, and oxygen. Examples of the spinel include MgAl 2 O 4 , FeAl 2 O 4 , ZnAl 2 O 4 , and MnAl 2 O 4 .

[0078] In this specification, the so-called main component refers to a component that accounts for more than 50 wt %. The material of the main component may exist in any state of single crystal, polycrystalline, or amorphous, or in a state of a mixture of these.

[0079] On the other hand, the second layer 6 of the intermediate layer 4 is a low-acoustic-velocity film. A low-acoustic-velocity film is a film with a relatively low acoustic velocity. More specifically, the acoustic velocity of bulk waves propagating through the low-acoustic-velocity film is lower than the acoustic velocity of bulk waves propagating through the piezoelectric layer. Materials for the low-acoustic-velocity film include dielectrics such as glass, silicon oxide, silicon oxynitride, lithium oxide, tantalum oxide, or compounds containing silicon oxide doped with fluorine, carbon, or boron, or materials primarily composed of any of these materials.

[0080] In the first embodiment, the first layer 5 as a high-acoustic-velocity film, the second layer 6 as a low-acoustic-velocity film, and the lithium niobate layer 7 as a piezoelectric layer are sequentially stacked. This effectively confines the energy of the elastic wave to the lithium niobate layer 7 .

[0081] like Figure 1 As shown in FIG. 1 , the first main surface 3a of the silicon single crystal substrate 3 is in contact with the intermediate layer 4. Alternatively, the intermediate layer 4 may not be provided. Figure 8In the illustrated variation of the first embodiment, a lithium niobate layer 7 is directly provided on the first principal surface 3a of the silicon single crystal substrate 3. The first principal surface 3a is in contact with the lithium niobate layer 7. In this case, as in the first embodiment, the elastic wave device can be made broadband and unnecessary waves can be suppressed.

[0082] The elastic wave device according to the present invention may also have a structure utilizing a piston mode. In this case, the transverse mode can be suppressed. This example is described below.

[0083] Figure 9 It is a schematic plan view of an elastic wave device according to the second embodiment.

[0084] This embodiment differs from the first embodiment in that a pair of mass-adding films is provided. Specifically, the pair of mass-adding films is a first mass-adding film 24 and a second mass-adding film 25. Other than these features, the elastic wave device of this embodiment has the same structure as the elastic wave device 1 of the first embodiment. Hereinafter, the first mass-adding film 24 and the second mass-adding film 25 may be referred to simply as "mass-adding films."

[0085] When observing the IDT electrode 8 from the direction of elastic wave propagation, the area where the adjacent first electrode fingers 18 and second electrode fingers 19 overlap is the intersection area A. The intersection area A has a central area C and a pair of edge areas. The pair of edge areas are specifically the first edge area Ea and the second edge area Eb. The first edge area Ea and the second edge area Eb are opposite to each other with the central area C sandwiched therebetween in the direction in which the electrode fingers extend. In addition, the first edge area Ea of the first edge area Ea and the second edge area Eb is located on the first bus bar 16 side. The second edge area Eb of the first edge area Ea and the second edge area Eb is located on the second bus bar 17 side.

[0086] In this embodiment, the dimension of each edge region along the electrode finger extending direction is 0.6λ. However, the dimension of each edge region along the electrode finger extending direction is not limited to the above.

[0087] The area between the intersection region A and the pair of bus bars constitutes a pair of gap regions. Specifically, the pair of gap regions is a first gap region Ga and a second gap region Gb. More specifically, the first gap region Ga is located between the first edge region Ea and the first bus bar 16. The second gap region Gb is located between the second edge region Eb and the second bus bar 17.

[0088] In the first embodiment, the IDT electrode 8 is configured similarly to that of the present embodiment. Therefore, in the first embodiment, the intersection region A and a pair of gap regions can also be defined.

[0089] The first mass adding film 24 and the second mass adding film 25 have strip-like shapes. One first mass adding film 24 is provided across multiple electrode fingers in the first edge region Ea. Similarly, one second mass adding film 25 is provided across multiple electrode fingers in the second edge region Eb. The first mass adding film 24 and the second mass adding film 25 are also provided on the lithium niobate layer 7 between the electrode fingers.

[0090] Because the first mass-added film 24 is provided in the first edge region Ea, the sound velocity in the first edge region Ea becomes lower than the sound velocity in the central region C. Consequently, a low sound velocity region is formed in the first edge region Ea. A low sound velocity region is a region where the sound velocity is lower than that in the central region C. Similarly, a low sound velocity region is also formed in the second edge region Eb.

[0091] In this embodiment, the central region C and a pair of low-acoustic-velocity regions are arranged in this order from the inside to the outside in the electrode finger extending direction. This allows a piston mode to be established, thereby suppressing the transverse mode.

[0092] The mass-adding film may be provided in at least one of the first edge region Ea and the second edge region Eb. However, the mass-adding film is preferably provided in both the first edge region Ea and the second edge region Eb. This allows the piston mode to be established more reliably.

[0093] The mass-adding film only needs to overlap at least one of the multiple electrode fingers when viewed from above. However, when viewed from above, it is preferred that multiple electrode fingers overlap with the mass-adding film, and more preferably, that all electrode fingers overlap with the mass-adding film. This ensures that the piston mode is established more reliably.

[0094] In this specification, the term "top view" refers to a view from the Figure 1 In other words, the elastic wave device is observed from the direction in which the silicon single crystal substrate 3 and the lithium niobate layer 7 are stacked. Figure 1 In the embodiment, for example, the lithium niobate layer 7 side is an upper side between the silicon single crystal substrate 3 side and the lithium niobate layer 7 side.

[0095] In this embodiment, the first mass adding film 24 is laminated not only on the electrode fingers of the IDT electrode 8 but also on the reflector electrode fingers 14c of each reflector. The second mass adding film 25 is also laminated on the electrode fingers of the IDT electrode 8 and the reflector electrode fingers 14c of each reflector. However, the first mass adding film 24 and the second mass adding film 25 do not necessarily need to be laminated on the reflector electrode fingers 14c of each reflector.

[0096] As a material for the mass addition film, for example, a dielectric such as tantalum oxide can be used. The dimension of the mass addition film along the electrode finger extending direction and the thickness of the mass addition film that facilitates suppressing the transverse mode vary depending on the material of the mass addition film.

[0097] In the first gap region Ga, only the first electrode fingers 18 are provided, out of the first electrode fingers 18 and the second electrode fingers 19. Thus, a high-acoustic-velocity region is formed in the first gap region Ga. A high-acoustic-velocity region is a region where the acoustic velocity is higher than that in the central region C. Similarly, a high-acoustic-velocity region is also formed in the second gap region Gb.

[0098] In this embodiment, the central region C, a pair of low-acoustic-velocity regions, and a pair of high-acoustic-velocity regions are arranged in this order from the inside to the outside in the electrode finger extending direction. This makes it possible to more reliably establish the piston mode.

[0099] In this embodiment, as in the first embodiment, a lithium niobate layer 7 is indirectly provided on the first principal surface 3a of the silicon single crystal substrate 3 via an intermediate layer 4. Furthermore, the plane orientation of the first principal surface 3a is (111), and the Euler angles of the first principal surface 3a are in the range of -30° < ψ < 30°. This allows the elastic wave device to have a wide bandwidth and suppress unwanted waves.

[0100] In addition, although Figure 9 Although omitted in the embodiment, in this embodiment, a Figure 1 The dielectric film 15 is shown. In the portion where the electrode fingers, mass-added film, and dielectric film 15 are stacked, the lithium niobate layer 7, electrode fingers, mass-added film, and dielectric film 15 are stacked in this order. However, the stacking order is not limited to this. For example, the lithium niobate layer 7, electrode fingers, dielectric film 15, and mass-added film may be stacked in this order. In this case, a metal may be used as the material for the mass-added film.

[0101] Alternatively, the lithium niobate layer 7, the mass addition film, the electrode fingers, and the dielectric film 15 may be stacked in this order. In this manner, a mass addition film may be provided between the lithium niobate layer 7 and the electrode fingers.

[0102] Other examples utilizing the piston mode are described below through the third to fifth embodiments. In the third to fifth embodiments, as in the second embodiment, the elastic wave device can be made broadband and transverse modes and harmonics, which are unnecessary waves, can be suppressed.

[0103] Figure 10 It is a schematic plan view of an elastic wave device according to a third embodiment.

[0104] This embodiment differs from the second embodiment in that multiple first mass addition films 34 are provided in the first edge region Ea and on the reflector electrode fingers 14c of each reflector. This embodiment also differs from the second embodiment in that multiple second mass addition films 35 are provided in the second edge region Eb and on the reflector electrode fingers 14c of each reflector. Other than these features, the elastic wave device of this embodiment has the same structure as the elastic wave device of the second embodiment.

[0105] Each first mass adding film 34 and each second mass adding film 35 is stacked on one first electrode finger 18, one second electrode finger 19, or one reflector electrode finger 14c. Alternatively, the first mass adding film 34 and the second mass adding film 35 may not be stacked on the reflector electrode finger 14c of each reflector.

[0106] In this embodiment, each of the first mass adding films 34 and the second mass adding films 35 does not contact a plurality of electrode fingers connected to different potentials. In this case, a metal can be used as the material for the first mass adding films 34 and the second mass adding films 35. However, a dielectric can also be used as the material for the first mass adding films 34 and the second mass adding films 35.

[0107] Figure 11 It is a schematic plan view of an elastic wave device according to a fourth embodiment.

[0108] This embodiment differs from the first embodiment in the shape of the electrode fingers. Specifically, in the first embodiment, the width of each electrode finger is fixed. On the other hand, in this embodiment, the width of each electrode finger is not fixed. Furthermore, the width of an electrode finger refers to the dimension of the electrode finger along the direction of propagation of the elastic wave. This embodiment also differs from the first embodiment in the shape of the reflector electrode finger 44c. Except for the above-mentioned aspects, the elastic wave device of this embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0109] More specifically, the plurality of first electrode fingers 48 and the plurality of second electrode fingers 49 have wide portions. More specifically, the first electrode fingers 48 have wide portions 48a and 48b. Wide portions 48a are located in the first edge region Ea. Wide portions 48b are located in the second edge region Eb. The electrode fingers in the wide portions are wider than those in the central region C.

[0110] Similarly, the second electrode finger 49 has a wide portion 49a and a wide portion 49b. The wide portion 49a is located in the first peripheral area Ea, and the wide portion 49b is located in the second peripheral area Eb.

[0111] Since each electrode finger has a wide portion, the acoustic velocity in both edge regions is lower than the acoustic velocity in the central region C. Thus, low acoustic velocity regions are formed in both edge regions.

[0112] The wide portion of the electrode finger only needs to be located in at least one of the first edge region Ea and the second edge region Eb. However, the wide portion is preferably located in both the first edge region Ea and the second edge region Eb. This allows the piston mode to be established more reliably.

[0113] At least one electrode finger may have a wide portion. However, it is preferred that multiple electrode fingers have wide portions, and it is more preferred that all electrode fingers have wide portions. This allows the piston mode to be established more reliably.

[0114] The electrode fingers may have wide portions and be provided with the mass-adding films. In this case, the piston mode can also be established.

[0115] Furthermore, in the present invention, the width of the electrode fingers in the edge region may be narrower than the width of the electrode fingers in the central region C.

[0116] In this embodiment, the plurality of reflector electrode fingers 44 c of each reflector also have wide portions, similar to the plurality of first electrode fingers 48 and the plurality of second electrode fingers 49. However, the reflector electrode fingers 44 c do not need to have wide portions.

[0117] Figure 12 4 is a schematic cross-sectional view of an elastic wave device according to a fifth embodiment, taken along the direction in which the electrode fingers extend.

[0118] This embodiment differs from the first embodiment in the shape of the electrode fingers. Specifically, in the first embodiment, the thickness of each electrode finger is constant. In contrast, in this embodiment, the thickness of each electrode finger is not constant. Other than these features, the elastic wave device of this embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0119] More specifically, the thickness of the first electrode finger 58 located in the first edge region Ea is thicker than the thickness of the first electrode finger 58 located in the central region C. The thickness of the first electrode finger 58 located in the second edge region Eb is thicker than the thickness of the first electrode finger 58 located in the central region C.

[0120] Similarly, the second electrode finger portion located in the first edge region Ea is thicker than the portion located in the central region C. The second electrode finger portion located in the second edge region Eb is thicker than the portion located in the central region C.

[0121] By making the thicknesses of the electrode fingers different, the acoustic velocity in both edge regions is lower than the acoustic velocity in the central region C. Thus, low acoustic velocity regions are formed in both edge regions.

[0122] Furthermore, the thickness of the electrode fingers in at least one of the first edge region Ea and the second edge region Eb is sufficient as compared to that in the central region C. However, it is preferred that the thickness of the electrode fingers in both the first edge region Ea and the second edge region Eb be thicker than that in the central region C. This allows the piston mode to be established more reliably.

[0123] It suffices that the portion located in the edge region of at least one electrode finger is thicker than the portion located in the central region C. However, it is preferred that the portion located in the edge region of a plurality of electrode fingers be thicker than the portion located in the central region C, and it is more preferred that the portion located in the edge region of all electrode fingers be thicker than the portion located in the central region C. This allows the piston mode to be more reliably established.

[0124] Furthermore, in the present invention, the thickness of the electrode fingers in the edge region may be thinner than the thickness of the electrode fingers in the central region C.

[0125] The elastic wave device according to the present invention can be used in a filter device, a composite filter device such as a multiplexer, and the like.

[0126] Figure 13 This is a circuit diagram of a filter device according to a sixth embodiment of the present invention.

[0127] The filter device 60 is a ladder-type filter. In this embodiment, the filter device 60 is a transmission filter. However, the filter device 60 may also be a reception filter. The filter device 60 is mounted on a mounting substrate, for example.

[0128] The filter device 60 includes a first signal terminal 62 and a second signal terminal 63, and a plurality of series arm resonators and a plurality of parallel arm resonators. In this embodiment, all of the series arm resonators and all of the parallel arm resonators are elastic wave resonators. All of the parallel arm resonators and all of the series arm resonators share a piezoelectric substrate. Furthermore, all of the parallel arm resonators and all of the series arm resonators in the filter device 60 are elastic wave devices according to the present invention.

[0129] The first signal terminal 62 and the second signal terminal 63 may be configured as, for example, electrode pads or wiring. In this embodiment, the first signal terminal 62 is an antenna terminal. The antenna terminal is connected to an antenna.

[0130] The plurality of series arm resonators of the filter device 60 are specifically a series arm resonator S1, a series arm resonator S2, and a series arm resonator S3. The plurality of parallel arm resonators are specifically a parallel arm resonator P1 and a parallel arm resonator P2.

[0131] Between the first signal terminal 62 and the second signal terminal 63, the series arm resonator S1, the series arm resonator S2, and the series arm resonator S3 are connected in series. A parallel arm resonator P1 is connected between the connection point between the series arm resonator S1 and the series arm resonator S2 and the ground potential. A parallel arm resonator P2 is connected between the connection point between the series arm resonator S2 and the series arm resonator S3 and the ground potential. In addition, the circuit structure of the filter device 60 is not limited to the above. In the case where the filter device 60 is a ladder-type filter, it is sufficient to have at least one series arm resonator and at least one parallel arm resonator. Alternatively, the filter device 60 may also include a longitudinally coupled resonator-type elastic wave filter.

[0132] Although not shown, the lithium niobate layer in the piezoelectric substrate is provided with a first signal terminal 62, a second signal terminal 63, and a plurality of ground terminals. The plurality of ground terminals are connected to a ground potential. In a configuration where the filter device 60 is mounted on a mounting substrate, the first signal terminal 62, the second signal terminal 63, and the plurality of ground terminals are bonded to the mounting substrate. The bonding between each terminal and the mounting substrate can be achieved using, for example, bumps or a suitable conductive adhesive.

[0133] The filter device according to the present invention can also have a WLP (Wafer Level Package) structure. In this case, a support member is provided on the lithium niobate layer of the piezoelectric substrate so as to surround the IDT electrodes of the multiple elastic wave resonators. A cover member is provided on the support member. This forms a hollow portion surrounded by the piezoelectric substrate, the support member, and the cover member. Each IDT electrode is located within this hollow portion. Furthermore, multiple through-electrodes are provided that penetrate the support member and the cover member. One end of each through-electrode is connected to a terminal. A bump or the like is bonded to the other end of each through-electrode.

[0134] The filter device 60 includes an elastic wave resonator as the elastic wave device according to the present invention. Therefore, similar to the first embodiment and other embodiments, the elastic wave resonator of the filter device 60 can be made broadband. This makes it easy to broaden the passband of the filter device 60. Furthermore, the elastic wave resonator in the filter device 60 can suppress unwanted waves. Consequently, when the filter device 60 is used in a composite filter device, the influence of unwanted waves on other filter devices can be suppressed.

[0135] Figure 14It is a schematic diagram of a composite filter device according to a sixth embodiment of the present invention.

[0136] Composite filter device 70 is a multiplexer. More specifically, composite filter device 70 is a duplexer. Composite filter device 70 includes a first filter device 71A, a second filter device 71B, and a common connection terminal 78. First filter device 71A and second filter device 71B are commonly connected to common connection terminal 78. Common connection terminal 78 can be configured as an electrode pad or wiring, for example. In this embodiment, common connection terminal 78 is an antenna terminal.

[0137] The first filter device 71A is a filter device according to the present invention. On the other hand, the second filter device 71B is not a filter device according to the present invention. Specifically, the first filter device 71A and the second filter device 71B have separate piezoelectric substrates. The structure of the piezoelectric substrate in the second filter device 71B differs from that of the elastic wave device according to the present invention.

[0138] The composite filter device 70 is mounted on a mounting substrate, for example. The first filter device 71A and the second filter device 71B are arranged on the mounting substrate as independent components.

[0139] Figure 15 1 is a schematic front cross-sectional view showing a structure in which a composite filter device according to the sixth embodiment is mounted on a mounting substrate. Figure 15 In FIG. 1 , the IDT electrode and the reflector are shown by a simplified diagram in which two diagonal lines are added to a rectangle.

[0140] The first filter device 71A and the second filter device 71B are each flip-chip mounted on a mounting substrate 74. Specifically, the terminals of the first filter device 71A are bonded to the mounting substrate 74 via bumps 79. Similarly, the terminals of the second filter device 71B are bonded to the mounting substrate 74 via bumps 79. Alternatively, the first filter device 71A and the second filter device 71B may have a WLP structure.

[0141] Hereinafter, the piezoelectric substrate in the elastic wave device according to the present invention is referred to as the first piezoelectric substrate, and the piezoelectric layer is referred to as the first piezoelectric layer. However, the first piezoelectric substrate in this embodiment has the same Figure 1 The piezoelectric substrate 2 of the elastic wave device 1 according to the first embodiment shown in FIG. Figure 15 The lithium niobate layer 7 is shown.

[0142] On the other hand, the second filter device 71B includes a second piezoelectric substrate 72. The second piezoelectric substrate 72 includes a support substrate 73, a third layer 75, a fourth layer 76, and a second piezoelectric layer. Furthermore, the second piezoelectric layer is a lithium tantalate layer 77. The support substrate 73, the third layer 75, the fourth layer 76, and the lithium tantalate layer 77 are stacked in this order. In the composite filter device 70, the material of the first piezoelectric layer in the first filter device 71A and the material of the second piezoelectric layer in the second filter device 71B are different from each other.

[0143] IDT electrodes of the elastic wave resonators of the second filter device 71B are provided on the lithium tantalate layer 77 .

[0144] As a material of the support substrate 73 , for example, semiconductors such as silicon, ceramics such as alumina, or the like can be used.

[0145] The third layer 75 is a high-acoustic-velocity component. More specifically, in this embodiment, the third layer 75 is a high-acoustic-velocity film. The acoustic velocity of the bulk waves propagating through the third layer 75 is higher than the acoustic velocity of the elastic waves propagating through the second piezoelectric layer. Furthermore, in this embodiment, the second piezoelectric layer is a lithium tantalate layer 77.

[0146] The third layer 75 may be a high-acoustic-velocity supporting substrate as a high-acoustic-velocity member. In this case, the second piezoelectric substrate 72 may not include the supporting substrate 73 .

[0147] The fourth layer 76 is a low-acoustic-velocity film. The acoustic velocity of the bulk wave propagating through the fourth layer 76 is lower than the acoustic velocity of the bulk wave propagating through the second piezoelectric layer.

[0148] A lithium tantalate layer 77 serving as a second piezoelectric layer is provided indirectly on the third layer 75 via the fourth layer 76. However, the lithium tantalate layer 77 may be provided directly on the third layer 75. Alternatively, the second piezoelectric substrate 72 may be a stack of the support substrate 73 and the lithium tantalate layer 77. The second piezoelectric substrate 72 may also be a lithium tantalate substrate.

[0149] Composite filter device 70 includes a first filter device 71A that includes the elastic wave device according to the present invention. This makes it easy to broaden the passband of first filter device 71A in composite filter device 70. Furthermore, unwanted waves can be suppressed in the elastic wave resonator in first filter device 71A. This also reduces the effect of unwanted waves on second filter device 71B.

[0150] Figure 16 It is a schematic diagram of a composite filter device according to the seventh embodiment.

[0151] The composite filter device 80 is a multiplexer and includes a plurality of filter devices and a common connection terminal 78 . The plurality of filter devices are commonly connected to the common connection terminal 78 .

[0152] Specifically, the plurality of filter devices are a first filter device 71A, a second filter device 71B, a third filter device 81C, and at least one other filter device. The first filter device 71A and the second filter device 71B have the same structure as in the sixth embodiment. The third filter device 81C and the other filter devices have different passbands.

[0153] Alternatively, the third filter device 81C can be a duplexer. In this case, the communication frequency band of the duplexer formed by the first filter device 71A and the second filter device 71B is different from the communication frequency band of the third filter device 81C. However, the first filter device 71A and the second filter device 71B do not necessarily constitute a duplexer. Alternatively, the composite filter device 80 can include multiple first filter devices 71A. In this case, each first filter device 71A can be a filter device that includes the elastic wave device of the present invention. The circuit structure, elastic wave resonator structure, or design parameters of the multiple first filter devices 71A can also differ. The composite filter device 80 can also include multiple second filter devices 71B. In this case, each second filter device 71B can include the second piezoelectric substrate described in the sixth embodiment. The circuit structure, elastic wave resonator structure, or design parameters of the multiple second filter devices 71B can also differ.

[0154] In this embodiment, as in the sixth embodiment, the passband of the first filter device 71A in the composite filter device 80 can be easily widened. Furthermore, the elastic wave resonator in the first filter device 71A can suppress unwanted waves. This can reduce the effect of unwanted waves on other filter devices.

[0155] Hereinafter, examples of aspects of the elastic wave device and the composite filter device according to the present invention will be summarized and described.

[0156] <1> An elastic wave device comprises: a silicon single crystal substrate having a main surface; a piezoelectric layer directly or indirectly arranged on the main surface of the silicon single crystal substrate; and an IDT electrode arranged on the piezoelectric layer and having a plurality of electrode fingers, wherein the piezoelectric layer is a lithium niobate layer, and the surface orientation on the main surface of the silicon single crystal substrate is (111). When the Euler angles in the main surface of the silicon single crystal substrate are set to (φ, θ, ψ), ψ in the Euler angles of the silicon single crystal substrate is -30°<ψ<30°.

[0157] <2> according to <1> In the elastic wave device described above, ψ in the Euler angles of the silicon single crystal substrate satisfies -15°≤ψ≤15°.

[0158] <3> according to <1> or <2> The elastic wave device described herein further comprises: an intermediate layer arranged between the silicon single crystal substrate and the piezoelectric layer, the piezoelectric layer being indirectly arranged on the main surface of the silicon single crystal substrate via the intermediate layer, and the main surface of the silicon single crystal substrate being in contact with the intermediate layer.

[0159] <4> according to <3> In the elastic wave device described above, the intermediate layer is a single-layer dielectric layer, and silicon oxide is used as a material for the intermediate layer.

[0160] <5> according to <3> The elastic wave device described, wherein the intermediate layer includes a first layer and a second layer, the first layer is arranged on the silicon single crystal substrate, the second layer is arranged on the first layer, and the piezoelectric layer is arranged on the second layer, the sound velocity of the body wave propagating in the first layer is higher than the sound velocity of the elastic wave propagating in the piezoelectric layer, and the sound velocity of the body wave propagating in the second layer is lower than the sound velocity of the body wave propagating in the piezoelectric layer.

[0161] <6> according to <1> or <2> In the elastic wave device described above, the piezoelectric layer is directly provided on the main surface of the silicon single crystal substrate, and the main surface of the silicon single crystal substrate is in contact with the piezoelectric layer.

[0162] <7> according to <1> ~ <6> In the elastic wave device described in any one of claims , when a wavelength defined by an electrode finger pitch of the IDT electrode is denoted as λ, the thickness of the piezoelectric layer is 1λ or less.

[0163] <8> according to <1> ~ <7> The elastic wave device according to any one of the preceding claims, wherein the piezoelectric layer has an X-axis, a Y-axis, and a Z-axis as crystal axes, and is a Y-cut, X-propagation lithium niobate single crystal layer.

[0164] <9> according to <1> ~ <8> The elastic wave device according to any one of the preceding claims further includes a dielectric film provided on the piezoelectric layer so as to cover the IDT electrode.

[0165] <10> according to <9> In the elastic wave device described above, silicon oxide or silicon nitride is used as the material of the dielectric film.

[0166] <11> according to <1> ~ <10> An elastic wave device as described in any one of the items, wherein, when the direction in which the plurality of electrode fingers extend is set as the electrode finger extension direction, when the IDT electrode is observed from the elastic wave propagation direction orthogonal to the electrode finger extension direction, the area where adjacent electrode fingers overlap with each other is an intersection area, and the intersection area has a central area and a pair of edge areas opposite to each other with the central area sandwiched in the electrode finger extension direction, and at least one of the edge areas is further provided with a mass addition film that is arranged to overlap with at least one of the electrode fingers when viewed from above.

[0167] <12> according to <1> ~ <11> An elastic wave device as described in any one of the items, wherein, when the direction in which the plurality of electrode fingers extend is set as the electrode finger extension direction, when the IDT electrode is observed from the elastic wave propagation direction orthogonal to the electrode finger extension direction, the area where adjacent electrode fingers overlap with each other is an intersection area, and the intersection area has a central area and a pair of edge areas opposite to each other with the central area sandwiched in the electrode finger extension direction, and at least one of the electrode fingers has a wide portion located in at least one of the edge areas.

[0168] <13> An elastic wave device comprises: a silicon single crystal substrate having a main surface; a piezoelectric layer directly or indirectly arranged on the main surface of the silicon single crystal substrate; and an IDT electrode arranged on the piezoelectric layer and having a plurality of electrode fingers, wherein the main surface of the silicon single crystal substrate has a plane orientation of (111), the piezoelectric layer has an X-axis, a Y-axis, and a Z-axis as crystal axes, and the piezoelectric layer is a Y-cut X-propagating lithium niobate layer. When one of the directions in which the X-axis of the piezoelectric layer extends is set as the +X direction, the angle formed by the +X direction and the [1-10] direction in the silicon single crystal substrate is greater than or equal to -15° and less than or equal to 15°.

[0169] <14> A composite filter device mounted on a mounting substrate, wherein the composite filter device comprises: a common connection terminal; and a plurality of filter devices commonly connected to the common connection terminal, at least one of the plurality of filter devices comprising the invention <1> ~ <13> The first filter device of the elastic wave device described in any one of the above items, at least one of the multiple filter devices is a second filter device having a second piezoelectric layer, the first filter device and the second filter device are arranged on the mounting substrate as independent components, and the second piezoelectric layer is a lithium tantalate layer.

[0170] <15> according to <14> The composite filter device described, wherein the second filter device has a third layer, the second piezoelectric layer is directly or indirectly provided on the third layer, and the acoustic velocity of the bulk wave propagating in the third layer is higher than the acoustic velocity of the elastic wave propagating in the second piezoelectric layer.

[0171] Description of Reference Numerals

[0172] 1…Elastic wave device

[0173] 2…Piezoelectric substrate

[0174] 3…Silicon single crystal substrate

[0175] 3a, 3b…1st and 2nd main surfaces

[0176] 4…Middle Layer

[0177] 5, 6…1st and 2nd floors

[0178] 7…Lithium niobate layer

[0179] 8…IDT electrode

[0180] 8a, 8b…Pages 1 and 2

[0181] 8c…side

[0182] 14A, 14B…reflectors

[0183] 14c…Reflector electrode finger

[0184] 15…Dielectric film

[0185] 16, 17…1st and 2nd bus bars

[0186] 18, 19…1st and 2nd electrode fingers

[0187] 24, 25…1st and 2nd quality additional films

[0188] 34, 35…1st and 2nd quality additional films

[0189] 44c…Reflector electrode finger

[0190] 48, 49…1st and 2nd electrode fingers

[0191] 48a, 48b, 49a, 49b...wide portion

[0192] 58…1st electrode finger

[0193] 60…Filter device

[0194] 62, 63…1st and 2nd signal terminals

[0195] 70…Compound filter device

[0196] 71A, 71B...1st and 2nd filter devices

[0197] 72…second piezoelectric substrate

[0198] 73…Support base plate

[0199] 74…Mounting base plate

[0200] 75, 76…3rd and 4th floors

[0201] 77…lithium tantalate layer

[0202] 78…Common connection terminal

[0203] 79…bump

[0204] 80…Compound filter device

[0205] 81C…3rd filter device

[0206] A…Intersection Area

[0207] C…Central area

[0208] Ea, Eb…1st and 2nd edge areas

[0209] Ga, Gb...1st and 2nd gap regions

[0210] P1, P2…parallel arm resonator

[0211] S1~S3...series arm resonator.

Claims

1. An elastic wave device comprising: A silicon single crystal substrate having a main surface; a piezoelectric layer provided directly or indirectly on the main surface of the silicon single crystal substrate; and The IDT electrode is provided on the piezoelectric layer and has a plurality of electrode fingers. The piezoelectric layer is a lithium niobate layer, On the main surface of the silicon single crystal substrate, the plane orientation is (111), When the Euler angles on the main surface of the silicon single crystal substrate are represented by (φ, θ, ψ), ψ among the Euler angles of the silicon single crystal substrate satisfies −30°<ψ<30°.

2. The elastic wave device according to claim 1, wherein The Euler angle ψ of the silicon single crystal substrate is -15°≤ψ≤15°.

3. The elastic wave device according to claim 1 or 2, wherein: It further comprises: an intermediate layer provided between the silicon single crystal substrate and the piezoelectric layer; The piezoelectric layer is indirectly provided on the main surface of the silicon single crystal substrate via the intermediate layer, and the main surface of the silicon single crystal substrate is in contact with the intermediate layer.

4. The elastic wave device according to claim 3, wherein The intermediate layer is a single-layer dielectric layer, and silicon oxide is used as a material of the intermediate layer.

5. The elastic wave device according to claim 3, wherein The intermediate layer includes a first layer and a second layer, The first layer is provided on the silicon single crystal substrate, the second layer is provided on the first layer, and the piezoelectric layer is provided on the second layer. The acoustic velocity of the bulk wave propagating in the first layer is higher than the acoustic velocity of the elastic wave propagating in the piezoelectric layer. The acoustic velocity of the bulk wave propagating through the second layer is lower than the acoustic velocity of the bulk wave propagating through the piezoelectric layer.

6. The elastic wave device according to claim 1 or 2, wherein: The piezoelectric layer is directly provided on the main surface of the silicon single crystal substrate, and the main surface of the silicon single crystal substrate is in contact with the piezoelectric layer.

7. The elastic wave device according to any one of claims 1 to 6, wherein: When a wavelength defined by the electrode finger pitch of the IDT electrode is denoted as λ, the thickness of the piezoelectric layer is 1λ or less.

8. The elastic wave device according to any one of claims 1 to 7, wherein The piezoelectric layer has an X-axis, a Y-axis, and a Z-axis as crystal axes, and is a Y-cut X-propagation lithium niobate single crystal layer.

9. The elastic wave device according to any one of claims 1 to 8, wherein The device further includes a dielectric film provided on the piezoelectric layer so as to cover the IDT electrode.

10. The elastic wave device according to claim 9, wherein As a material of the dielectric film, silicon oxide or silicon nitride is used.

11. The elastic wave device according to any one of claims 1 to 10, wherein When the direction in which the plurality of electrode fingers extend is defined as an electrode finger extending direction, when the IDT electrode is viewed from an elastic wave propagation direction perpendicular to the electrode finger extending direction, a region where adjacent electrode fingers overlap with each other is defined as an intersection region. The intersection region includes a central region and a pair of edge regions facing each other across the central region in the direction in which the electrode fingers extend. A mass addition film is further provided in at least one of the edge regions so as to overlap with at least one of the electrode fingers in a plan view.

12. The elastic wave device according to any one of claims 1 to 11, wherein When the direction in which the plurality of electrode fingers extend is defined as an electrode finger extending direction, when the IDT electrode is viewed from an elastic wave propagation direction perpendicular to the electrode finger extending direction, a region where adjacent electrode fingers overlap with each other is defined as an intersection region. The intersection region includes a central region and a pair of edge regions facing each other across the central region in the direction in which the electrode fingers extend. At least one of the electrode fingers has a wide portion located in at least one of the edge regions.

13. An elastic wave device comprising: A silicon single crystal substrate having a main surface; a piezoelectric layer provided directly or indirectly on the main surface of the silicon single crystal substrate; and The IDT electrode is provided on the piezoelectric layer and has a plurality of electrode fingers. On the main surface of the silicon single crystal substrate, the plane orientation is (111), The piezoelectric layer has an X-axis, a Y-axis, and a Z-axis as crystal axes, and is a Y-cut X-propagation lithium niobate layer. When one of the directions in which the X-axis of the piezoelectric layer extends is defined as a +X direction, an angle formed by the +X direction and a [1-10] direction in the silicon single crystal substrate is not less than -15° and not more than 15°.

14. A composite filter device mounted on a mounting substrate, wherein: The composite filter device comprises: Common connection terminals; and A plurality of filter devices are commonly connected to the common connection terminal, At least one of the plurality of filter devices is a first filter device including the elastic wave device according to any one of claims 1 to 13. At least one of the plurality of filter devices is a second filter device having a second piezoelectric layer. The first filter device and the second filter device are arranged on the mounting substrate as independent components. The second piezoelectric layer is a lithium tantalate layer.

15. The composite filter device according to claim 14, wherein The second filter device has a third layer, The second piezoelectric layer is directly or indirectly provided on the third layer. The acoustic velocity of the bulk wave propagating through the third layer is higher than the acoustic velocity of the elastic wave propagating through the second piezoelectric layer.

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