Elastic wave device

Abstract

Even with miniaturization, the Q value can be improved, and miniaturization can be achieved. The elastic wave device also includes a piezoelectric layer (4), a first electrode (51) and a second electrode (52), a first segmented resonator (RS3) and a second segmented resonator (RS4), and a support substrate (2). The support substrate (2) has a first energy sealing layer and a second energy sealing layer. The first energy sealing layer overlaps with at least a portion of a first region (451) of the piezoelectric layer (4). The second energy sealing layer overlaps with at least a portion of a second region (452) of the piezoelectric layer (4). In the support substrate (2), the first energy sealing layer and the second energy sealing layer are integrally formed.

Description

Technical Field

[0001] This invention generally relates to elastic wave devices, and more specifically, to elastic wave devices having a piezoelectric layer. Background Technology

[0002] Conventionally, elastic wave devices utilizing plate waves propagating in a piezoelectric film comprising LiNbO3 or LiTaO3 are known. For example, Patent Document 1 disclosed below discloses an elastic wave device utilizing a Lamb wave as a plate wave. Here, an IDT electrode is provided on the upper surface of a piezoelectric substrate comprising LiNbO3 or LiTaO3. A voltage is applied between a plurality of first electrode fingers and a plurality of second electrode fingers of the IDT electrode. This excites a Lamb wave. A reflector is provided on each side of the IDT electrode. Thus, an elastic wave resonator utilizing a plate wave is constructed.

[0003] Prior art literature

[0004] Patent documents

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

[0006] The problem that the invention aims to solve

[0007] In the elastic wave device described in Patent Document 1, miniaturization is considered by reducing the number of the first and second electrode fingers. However, when the number of the first and second electrode fingers is reduced, the Q value becomes lower. In addition, miniaturization is difficult to achieve because of the wall portion in the support body 10.

[0008] The present invention was made in view of the above aspects, and the object of the present invention is to provide an elastic wave device that can improve the Q value and achieve miniaturization even when miniaturization is promoted.

[0009] Methods for solving problems

[0010] An elastic wave device according to one aspect of the present invention includes a piezoelectric layer, a first electrode, and a second electrode. The first electrode and the second electrode are opposed to each other in a direction intersecting the thickness direction of the piezoelectric layer. The elastic wave device utilizes thickness shearing of a first-order mode bulk wave. The piezoelectric layer is made of lithium niobate or lithium tantalate. The elastic wave device includes a plurality of electrode portions, each including the first electrode and the second electrode. The elastic wave device also includes a first segmented resonator, a second segmented resonator, and a support substrate. The first segmented resonator and the second segmented resonator are connected in series without connecting other resonators to each other, or connected in parallel with each other relative to the same connection node on the path connecting the input terminal and the output terminal. The support substrate has a first main surface and a second main surface that are opposed to each other. The first segmented resonator includes a first mounting portion. The first mounting portion includes a first electrode portion of the plurality of electrode portions and a first region in the piezoelectric layer where the first electrode portion is mounted. The second segmented resonator includes a second mounting portion. The second mounting portion includes a second electrode portion of the plurality of electrode portions and a second region in the piezoelectric layer where the second electrode portion is mounted. The piezoelectric layer is disposed directly or indirectly on the support substrate. The support substrate has a first energy-sealing layer and a second energy-sealing layer. The first energy-sealing layer overlaps with at least a portion of the first region of the piezoelectric layer when viewed from the thickness direction. The second energy-sealing layer overlaps with at least a portion of the second region of the piezoelectric layer when viewed from the thickness direction. In the support substrate, the first energy-sealing layer and the second energy-sealing layer are integrally formed.

[0011] An elastic wave device according to one aspect of the present invention includes a piezoelectric layer, a first electrode, and a second electrode. The first electrode and the second electrode are opposite each other in a direction intersecting the thickness direction of the piezoelectric layer. The first electrode and the second electrode are adjacent electrodes. When the distance between the center lines of the first electrode and the second electrode is defined as p and the thickness of the piezoelectric layer is defined as d in any cross-section along the thickness direction of the piezoelectric layer, d / p is 0.5 or less. The material of the piezoelectric layer is lithium niobate or lithium tantalate. The elastic wave device includes a plurality of electrode portions, each including the first electrode and the second electrode. The elastic wave device also includes a first segmented resonator, a second segmented resonator, and a support substrate. The first segmented resonator and the second segmented resonator are connected in series without connecting other resonators to each other, or connected in parallel with each other relative to the same connection node on the path connecting the input terminal and the output terminal. The support substrate has a first main surface and a second main surface that are opposite each other. The first segmented resonator includes a first mounting portion. The first mounting portion includes a first electrode portion among the plurality of electrode portions and a first region in the piezoelectric layer where the first electrode portion is disposed. The second segmented resonator includes a second mounting portion. The second mounting portion includes a second electrode portion among the plurality of electrode portions and a second region in the piezoelectric layer where the second electrode portion is disposed. The piezoelectric layer is disposed directly or indirectly on the support substrate. The support substrate has a first energy sealing layer and a second energy sealing layer. The first energy sealing layer overlaps with at least a portion of the first region of the piezoelectric layer when viewed from the thickness direction of the piezoelectric layer. The second energy sealing layer overlaps with at least a portion of the second region of the piezoelectric layer when viewed from the thickness direction of the piezoelectric layer. In the support substrate, the first energy sealing layer and the second energy sealing layer are integrally formed.

[0012] Invention Effects

[0013] According to the elastic wave device of the present invention, even with miniaturization, the Q value can be improved, and further miniaturization can be achieved when forming the first segmented resonator and the second segmented resonator. Attached Figure Description

[0014] Figure 1 This is a top view of the elastic wave device according to Embodiment 1.

[0015] Figure 2 Regarding the aforementioned elastic wave device Figure 1 Sectional view along line A1-A1.

[0016] Figure 3 This is the equivalent circuit diagram of the aforementioned elastic wave device.

[0017] Figure 4 This is a top view of the resonator of the aforementioned elastic wave device.

[0018] Figure 5 This is a top view of the main part of the resonator in the aforementioned elastic wave device.

[0019] Figure 6A This is an explanatory diagram of Lamb. Figure 6B This is an illustration of the volume wave of the first-order mode of thickness shear.

[0020] Figure 7 Regarding the aforementioned elastic wave device Figure 4 Sectional view along line A2-A2.

[0021] Figure 8 This is a diagram illustrating the operation of the aforementioned elastic wave device.

[0022] Figure 9 This is an explanatory diagram of the structural model of an elastic wave device in reference mode.

[0023] Figure 10A This is a coordinate graph showing the relationship between the relative bandwidth of the thickness shear mode and the [thickness of the piezoelectric layer] / [distance between the center lines of the first and second electrodes] based on the construction model of the aforementioned elastic wave device. Figure 10B This is a coordinate graph showing the relationship between the relative bandwidth of the thickness shear mode and [thickness of the piezoelectric layer] / [distance between the centerlines of the paired electrodes] for the above-mentioned structural model. Figure 10A The magnified coordinate graph of the horizontal axis in the range of 0 to 0.2.

[0024] Figure 11 This is a coordinate graph showing the relationship between the relative bandwidth of the thickness shear mode and the normalized spurious level based on the construction model of the aforementioned elastic wave device.

[0025] Figure 12 This is the impedance-frequency characteristic diagram of the above-mentioned elastic wave device construction model.

[0026] Figure 13 This is a diagram illustrating the distribution of relative bandwidth in the combination of [thickness of the piezoelectric layer] / [distance between the centerlines of the first and second electrodes] and construction parameters, based on the structural model of the aforementioned elastic wave device.

[0027] Figure 14 This is a top view of the elastic wave device of Embodiment 1, a variation of Embodiment 1.

[0028] Figure 15 This is a cross-sectional view of the elastic wave device of Embodiment 1, Modification 2.

[0029] Figure 16This is a top view of the elastic wave device of variation 4 of embodiment 1.

[0030] Figure 17 This is a top view of the elastic wave device of variation 5 of embodiment 1.

[0031] Figure 18 This is a cross-sectional view of the elastic wave device according to Embodiment 2.

[0032] Figure 19 This is a top view of the elastic wave device according to Embodiment 2.

[0033] Figure 20 This is a top view of the elastic wave device of Embodiment 2, Variation 2.

[0034] Figures 21A to 21D This is a cross-sectional view showing another shape of a pair of electrodes of the aforementioned elastic wave device.

[0035] Figures 22A to 22C This is a cross-sectional view showing another structural example of the above-mentioned elastic wave device. Detailed Implementation

[0036] The following implementation methods, etc., refer to Figure 1 , Figure 2 , Figures 4-9 , Figures 14-20 , Figures 21A to 21D and Figures 22A to 22C These are all schematic diagrams. The size or thickness ratio of each component in the diagram may not necessarily reflect the actual size ratio.

[0037] (Implementation Method 1)

[0038] The following is for reference Figures 1-5 The elastic wave device 1 of Embodiment 1 will be described.

[0039] (1) Overall structure of elastic wave device

[0040] like Figure 1 As shown, the elastic wave device 1 of Embodiment 1 includes a piezoelectric layer 4, a first electrode 51, and a second electrode 52. As... Figure 2As shown, the first electrode 51 and the second electrode 52 are positioned opposite each other in a direction D2 (hereinafter also referred to as the second direction D2) that intersects the thickness direction (first direction) D1 of the piezoelectric layer 4. The elastic wave device 1 is an elastic wave device that utilizes a thickness shear first-order mode bulk wave. The second direction D2 is orthogonal to the polarization directions PZ1 and PZ2 of the piezoelectric layer 4. The thickness shear first-order mode bulk wave is a bulk wave that propagates in the thickness direction D1 of the piezoelectric layer 4 through thickness shear vibration of the piezoelectric layer 4, and is a bulk wave with a segment number of 1 in the thickness direction D1 of the piezoelectric layer 4. The thickness shear vibration is excited by the first electrode 51 and the second electrode 52. The thickness shear vibration is excited in the piezoelectric layer 4 in a defined region 45 between the first electrode 51 and the second electrode 52 when viewed from the thickness direction D1. In the elastic wave device 1, if the second direction D2 is orthogonal to the polarization directions PZ1 and PZ2 of the piezoelectric layer 4, the electromechanical coupling coefficient (hereinafter also referred to as the coupling coefficient) of the bulk wave of the first-order thickness shear mode is relatively large. Here, "orthogonal" is not limited to the strictly orthogonal case, but can also be approximately orthogonal (the angle between the second direction D2 and the polarization directions PZ1 and PZ2 is, for example, 90°±10°).

[0041] like Figure 1 and 2 As shown, the elastic wave device 1 includes multiple pairs of first electrodes 51 and second electrodes 52. In the elastic wave device 1, the multiple first electrodes 51 and multiple second electrodes 52 are arranged alternately, one at a time, in the second direction D2. Figure 1 As shown, the elastic wave device 1 further includes a first wiring portion 61 connected to the first electrode 51 and a second wiring portion 62 connected to the second electrode 52. Multiple first electrodes 51 are connected to the first wiring portion 61. Multiple second electrodes 52 are connected to the second wiring portion 62.

[0042] like Figure 2 As shown, the elastic wave device 1 includes a support substrate 2, a piezoelectric layer 4, a plurality of first electrodes 51, and a plurality of second electrodes 52. The piezoelectric layer 4 is disposed on the support substrate 2. As an example, the piezoelectric layer 4 is disposed on the support substrate 2 with a silicon oxide film 7 in between. The plurality of first electrodes 51 and the plurality of second electrodes 52 are disposed on the piezoelectric layer 4. As a resonator, the elastic wave device 1 has an elastic wave resonator 5 including the first electrodes 51, the second electrodes 52, and the piezoelectric layer 4. The support substrate 2 includes at least a portion of a cavity 26 that exposes a portion of the piezoelectric layer 4. The cavity 26 overlaps the entire elastic wave resonator 5 when viewed from the thickness direction D1 of the piezoelectric layer 4. Here, the cavity 26 overlaps the plurality of first electrodes 51, the plurality of second electrodes 52, and a plurality of defined regions 45 when viewed from the thickness direction D1 of the piezoelectric layer 4. The plurality of defined regions 45 are portions between pairs of first electrodes 51 and second electrodes 52.

[0043] like Figure 1 and Figure 3 As shown, the elastic wave device 1 in Embodiment 1 is an elastic wave filter (here, a trapezoidal filter). The elastic wave device 1 has an input terminal 15, an output terminal 16, a plurality of (two) series-arm resonators RS1 disposed on a first path 12 connecting the input terminal 15 and the output terminal 16, and a plurality of (two) parallel-arm resonators RS2 disposed on each of a plurality of (two) second paths 13 and 14 connecting a plurality of (two) nodes N1 and N2 on the first path 12 to ground (ground terminals 17 and 18). Ground terminals 17 and 18 can also be combined into a single ground.

[0044] Multiple series-arm resonators RS1 each have a first segmented resonator RS3 and a second segmented resonator RS4. The first segmented resonator RS3 and the second segmented resonator RS4 are connected in series. The first segmented resonator RS3 and the second segmented resonator RS4 (multiple segmented resonators) are resonators obtained by segmenting the series-arm resonators RS1, and are connected to each other without any parallel arm resonators RS2 connected to each other. The number of segmented resonators is not limited to two, and can also be three or more.

[0045] It should be noted that, among the various series arm resonators RS1, the first segmented resonator RS3 and the second segmented resonator RS4 can also be connected in parallel. In this case, the first segmented resonator RS3 and the second segmented resonator RS4 are connected in parallel with each other relative to the connection node on the first path 12 connecting the input terminal 15 and the output terminal 16.

[0046] Alternatively, the multiple parallel arm resonators RS2 may each have a first segmented resonator and a second segmented resonator. In each of the multiple parallel arm resonators RS2, the first segmented resonator and the second segmented resonator are connected in series or in parallel.

[0047] In the elastic wave device 1, the first segmented resonator RS3 and the second segmented resonator RS4 in the plurality of series-arm resonators RS1, and the plurality of parallel-arm resonators RS2 are all elastic wave resonators 5. Each of the plurality of elastic wave resonators 5 includes a plurality of first electrodes 51 and a plurality of second electrodes 52, but is not limited thereto; any resonator may include at least one pair of electrodes (first electrode 51, second electrode 52). In the elastic wave device 1, the piezoelectric layer 4 is used in all of the plurality of elastic wave resonators 5. The resonant frequency of the parallel-arm resonator RS2 is lower than the resonant frequency of the series-arm resonator RS1. Here, in the elastic wave resonator 5 constituting the parallel-arm resonator RS2, for example, a silicon oxide film is provided on the first main surface 41 of the piezoelectric layer 4; on the other hand, in the elastic wave resonator 5 constituting the series-arm resonator RS1, a silicon oxide film is not provided on the first main surface 41 of the piezoelectric layer 4. In the elastic wave resonator 5 constituting the series-arm resonator RS1, a silicon oxide film may also be provided on the first main surface 41 of the piezoelectric layer 4. In this case, the thickness of the silicon oxide film of the elastic wave resonator 5 constituting the series arm resonator RS1 can be thinner than the thickness of the silicon oxide film of the elastic wave resonator 5 constituting the parallel arm resonator RS2.

[0048] (2) Components of an elastic wave device

[0049] Next, the constituent elements of the elastic wave device 1 will be described with reference to the accompanying drawings.

[0050] (2.1) Support base plate

[0051] like Figure 2 As shown, the support substrate 2 supports the piezoelectric layer 4. In the elastic wave device 1 of Embodiment 1, the support substrate 2 supports the piezoelectric layer 4, a plurality of first electrodes 51, and a plurality of second electrodes 52 through a silicon oxide film 7. It should be noted that the silicon oxide film 7 is not a necessary component. In addition, other layers may be stacked between the support substrate 2 and the piezoelectric layer 4 besides the silicon oxide film 7.

[0052] The support substrate 2 has a first main surface 21 and a second main surface 22 that are opposite each other. The first main surface 21 and the second main surface 22 are opposite each other in the thickness direction of the support substrate 2. The thickness direction of the support substrate 2 is along the thickness direction D1 of the piezoelectric layer 4. When viewed from the thickness direction D1 of the piezoelectric layer 4, the outer periphery of the support substrate 2 is rectangular, but not limited to this, for example, it can also be square.

[0053] The support substrate 2 is, for example, a silicon substrate. The thickness of the support substrate 2 is, for example, 100 μm or more and 500 μm or less. The support substrate 2 is formed using a monocrystalline silicon substrate having a first main surface and a second main surface that are opposite each other. When the support substrate 2 is a monocrystalline silicon substrate, the orientation of the first main surface 21 can be, for example, a (100) surface, a (110) surface, or a (111) surface. The propagation orientation of the bulk wave can be set without being restricted by the orientation of the monocrystalline silicon substrate. The resistivity of the monocrystalline silicon substrate is, for example, 1 kΩ·cm or more, preferably 2 kΩ·cm or more, and more preferably 4 kΩ·cm or more.

[0054] The support substrate 2 is not limited to a silicon substrate, but can also be a crystal substrate, glass substrate, sapphire substrate, lithium tantalate substrate, lithium niobate substrate, alumina substrate, spinel substrate, gallium arsenide substrate, or silicon carbide substrate.

[0055] The support substrate 2 includes at least a portion of a cavity 26 that exposes a portion of the piezoelectric layer 4. The cavity 26 overlaps with the elastic wave resonator 5 when viewed from the thickness direction D1 of the piezoelectric layer 4. In the elastic wave device 1 of Embodiment 1, the cavity 26 is larger than the elastic wave resonator 5 when viewed from the thickness direction D1 of the piezoelectric layer 4, and overlaps entirely with the elastic wave resonator 5. Furthermore, in the elastic wave device 1 of Embodiment 1, the cavity 26 also overlaps with portions of the first wiring portion 61 and the second wiring portion 62 when viewed from the thickness direction D1 of the piezoelectric layer 4. The opening shape of the cavity 26 when viewed from the thickness direction D1 of the piezoelectric layer 4 is rectangular, but not limited to this.

[0056] (2.2) Silicon oxide film

[0057] A silicon oxide film 7 is disposed between the first main surface 21 of the support substrate 2 and the piezoelectric layer 4. In the elastic wave device 1 of Embodiment 1, the silicon oxide film 7 overlaps the entire area of ​​the first main surface 21 of the support substrate 2 in the thickness direction D1 of the piezoelectric layer 4. In the elastic wave device 1 of Embodiment 1, the support substrate 2 and the piezoelectric layer 4 are bonded together with the silicon oxide film 7 in between. The thickness of the silicon oxide film 7 is, for example, 0.1 μm or more and 10 μm or less.

[0058] (2.3) Piezoelectric layer

[0059] like Figure 2As shown, the piezoelectric layer 4 has a first main surface 41 and a second main surface 42 facing each other. The first main surface 41 and the second main surface 42 face each other in the thickness direction D1 of the piezoelectric layer 4. The piezoelectric layer 4 is disposed on the first main surface 21 of the support substrate 2. Here, the piezoelectric layer 4 overlaps with the first main surface 21 and the cavity 26 of the support substrate 2 when viewed from the thickness direction D1. In the piezoelectric layer 4, the first main surface 41 is located on the side of the first electrode 51 and the second electrode 52, and the second main surface 42 is located on the side of the support substrate 2. The first main surface 41 of the piezoelectric layer 4 is the main surface on the side opposite to the support substrate 2 side of the piezoelectric layer 4. The second main surface 42 of the piezoelectric layer 4 is the main surface on the support substrate 2 side of the piezoelectric layer 4.

[0060] In the elastic wave device 1, the distance between the first main surface 41 of the piezoelectric layer 4 and the supporting substrate 2 is longer than the distance between the second main surface 42 of the piezoelectric layer 4 and the supporting substrate 2. The material of the piezoelectric layer 4 is lithium niobate (LiNbO3) or lithium tantalate (LiTaO3). For example, the piezoelectric layer 4 is Z-cut LiNbO3 or Z-cut LiTaO3. Regarding the Euler angles of the piezoelectric layer 4... The angle is 0°±10°, and θ is 0°±10°. ψ is an arbitrary angle. From the viewpoint of improving the coupling coefficient, the piezoelectric layer 4 is preferably Z-cut LiNbO3 or Z-cut LiTaO3. The piezoelectric layer 4 can also be rotated Y-cut LiNbO3, rotated Y-cut LiTaO3, X-cut LiNbO3, or X-cut LiTaO3. The propagation orientation can be the Y-axis direction in the crystal axis (X, Y, Z) defined relative to the crystal structure of the piezoelectric layer 4, or the X-axis direction, or the direction after rotation from the X-axis within a range of ±90°. The piezoelectric layer 4 is a single crystal, but not limited to this; for example, it can also be a twin crystal or a ceramic.

[0061] The thickness of the piezoelectric layer 4 is, for example, 50 nm or more and 1000 nm or less, and for example, 400 nm.

[0062] The piezoelectric layer 4 has a defined region 45 (refer to...) Figure 5 The specified region 45 is the region that, when viewed from the thickness direction D1 of the piezoelectric layer 4, intersects both the first electrode 51 and the second electrode 52 in the direction D2 where the first electrode 51 and the second electrode 52 are opposite each other in the piezoelectric layer 4, and is located between the first electrode 51 and the second electrode 52.

[0063] (2.4) Electrode

[0064] Multiple first electrodes 51 and multiple second electrodes 52 are disposed on the first main surface 41 of the piezoelectric layer 4.

[0065] In the elastic wave device 1, the paired first electrode 51 and second electrode 52 are at different potentials. In the elastic wave device 1, the first electrode 51 of the paired first electrode 51 and second electrode 52 is a signal electrode, and the second electrode 52 is a ground electrode.

[0066] In the elastic wave device 1, a plurality of first electrodes 51 and a plurality of second electrodes 52 are arranged alternately, spaced apart from each other. Therefore, adjacent first electrodes 51 and second electrodes 52 are separated. The distance between the centerlines of adjacent first electrodes 51 and second electrodes 52 is, for example, 1 μm or more and 10 μm or less, and for example, 3 μm. Here, "adjacent" for the first electrodes 51 and second electrodes 52 means that the first electrodes 51 and second electrodes 52 are spaced apart and facing each other. A group of electrodes including a plurality of first electrodes 51 and a plurality of second electrodes 52 can be configured such that the plurality of first electrodes 51 and the plurality of second electrodes 52 are arranged spaced apart in the second direction D2, or it can be configured such that the plurality of first electrodes 51 and the plurality of second electrodes 52 are not alternately spaced apart from each other. For example, it is also possible to have a region where one first electrode 51 and one second electrode 52 are arranged spaced apart, and a region where two of the first electrodes 51 or the second electrodes 52 are arranged in the second direction D2.

[0067] like Figure 4 As shown, the plurality of first electrodes 51 and the plurality of second electrodes 52, viewed from the thickness direction D1 of the piezoelectric layer 4, are elongated strips (straight lines) with a third direction D3 orthogonal to the second direction D2 as the long side and the second direction D2 as the width direction. The length of each of the plurality of first electrodes 51 is, for example, 20 μm, but is not limited thereto. The width H1 (first electrode width H1) of each of the plurality of first electrodes 51 is, for example, in the range of 50 nm to 1000 nm, and is 500 nm as an example. The length of each of the plurality of second electrodes 52 is, for example, 20 μm, but is not limited thereto. The width H2 (second electrode width H2) of each of the plurality of second electrodes 52 is, for example, in the range of 50 nm to 1000 nm, and is 500 nm as an example.

[0068] Each of the plurality of first electrodes 51 has a first electrode main portion 510. The first electrode main portion 510 is the portion of the first electrode 51 that intersects with the second electrode 52 in the direction in which the first electrode 51 and the second electrode 52 are facing each other. Furthermore, each of the plurality of second electrodes 52 has a second electrode main portion 520. The second electrode main portion 520 is the portion of the second electrode 52 that intersects with the first electrode 51 in the direction in which the first electrode 51 and the second electrode 52 are facing each other.

[0069] In the elastic wave device 1 of Embodiment 1, the first electrode width H1 of the plurality of first electrodes 51 is the same, but is not limited to this and may be different. Similarly, in the elastic wave device 1 of Embodiment 1, the second electrode width H2 of the plurality of second electrodes 52 is the same, but is not limited to this and may be different. In the elastic wave device 1 of Embodiment 1, the first electrode width H1 and the second electrode width H2 are the same, but is not limited to this and may be different.

[0070] Regarding the elastic wave device 1 in Embodiment 1, in Figure 4 In the text, the number of the first electrode 51 and the second electrode 52 is described as 5, but the number of the first electrode 51 and the second electrode 52 is not limited to 5. It can also be 1, 2 to 4, 6 or more, or 50 or more.

[0071] The second direction D2, where the first electrode 51 and the second electrode 52 are positioned opposite each other, is preferably aligned with the polarization directions PZ1 and PZ2 of the piezoelectric layer 4 (refer to...). Figure 2 Orthogonal, but not limited to. For example, if the piezoelectric layer 4 is not a Z-cut piezoelectric material, the first electrode 51 and the second electrode 52 can also be positioned opposite each other in a direction orthogonal to the third direction D3, which is the long side direction. It should be noted that there are also cases where the first electrode 51 and the second electrode 52 are not rectangular. In this case, the third direction D3, which is the long side direction, can also be the long side direction of the circumscribed polygon that is external to the first electrode 51 and the second electrode 52 when viewed from above. It should be noted that the "circumscribed polygon that is external to the first electrode 51 and the second electrode 52" includes the following polygons: when the first electrode 51 and the second electrode 52 are connected to the first wiring portion 61 and the second wiring portion 62, at least the portion external to the first electrode 51 and the second electrode 52 excluding the portion connected to the first wiring portion 61 or the second wiring portion 62.

[0072] like Figure 7 As shown, the plurality of first electrodes 51 each include a first main surface 511 and a second main surface 512 intersecting the thickness direction D1 of the piezoelectric layer 4. In each of the plurality of first electrodes 51, the second main surface 512 of the first main surface 511 and the second main surface 512 is located on the side of the first main surface 41 of the piezoelectric layer 4 and is in planar contact with the first main surface 41 of the piezoelectric layer 4.

[0073] Each of the plurality of second electrodes 52 includes a first main surface 521 and a second main surface 522 that intersect the thickness direction D1 of the piezoelectric layer 4. In each of the plurality of second electrodes 52, the second main surface 522 of the first main surface 521 and the second main surface 522 is located on the side of the first main surface 41 of the piezoelectric layer 4 and is in planar contact with the first main surface 41 of the piezoelectric layer 4.

[0074] The plurality of first electrodes 51 and the plurality of second electrodes 52 are conductive. The materials of each first electrode 51 and each second electrode 52 are, for example, Al (aluminum), Cu (copper), Pt (platinum), Au (gold), Ag (silver), Ti (titanium), Ni (nickel), Cr (chromium), Mo (molybdenum), W (tungsten), or alloys primarily composed of any of these metals. Alternatively, each first electrode 51 and each second electrode 52 may have a structure formed by stacking multiple metal films comprising these metals or alloys. Each first electrode 51 and each second electrode 52, for example, comprises a laminated film of a bonding film and a main electrode film. The bonding film comprises a Ti film, and the main electrode film comprises an Al film or an AlCu film formed on the bonding film. The thickness of the bonding film is, for example, 10 nm. The thickness of the main electrode film is, for example, 80 nm. In the AlCu film, the concentration of Cu is preferably 1 wt% or more and 20 wt% or less.

[0075] (2.5) First wiring section and second wiring section

[0076] like Figure 4 As shown, the first wiring section 61 includes a first busbar 611. The first busbar 611 is a conductor section used to make the plurality of first electrodes 51 have the same potential. The first busbar 611 is a long strip (straight line) with the second direction D2 as its long side direction. The first busbar 611 is connected to the plurality of first electrodes 51. The plurality of first electrodes 51 connected to the first busbar 611 extend toward the second busbar 621. In the elastic wave device 1, the first conductor section including the plurality of first electrodes 51 and the first busbar 611 has a comb-shaped shape when viewed from the thickness direction D1 of the piezoelectric layer 4. The first busbar 611 and the plurality of first electrodes 51 are integrally formed, but are not limited thereto.

[0077] The second wiring section 62 includes a second busbar 621. The second busbar 621 is a conductor section used to bring the plurality of second electrodes 52 to the same potential. The second busbar 621 is a long strip (straight line) with the second direction D2 as its long side direction. The second busbar 621 is connected to the plurality of second electrodes 52. The plurality of second electrodes 52 connected to the second busbar 621 extend toward the first busbar 611. In the elastic wave device 1, the second conductor section including the plurality of second electrodes 52 and the second busbar 621 has a comb-shaped shape when viewed from the thickness direction D1 of the piezoelectric layer 4. The second busbar 621 and the plurality of second electrodes 52 are integrally formed, but are not limited thereto.

[0078] The first bus bar 611 and the second bus bar 621 are positioned opposite each other on the third direction D3.

[0079] The first wiring portion 61 and the second wiring portion 62 are conductive. The materials of the first wiring portion 61 and the second wiring portion 62 are, for example, Al, Cu, Pt, Au, Ag, Ti, Ni, Cr, Mo, W, or alloys primarily composed of any of these metals. Alternatively, the first wiring portion 61 and the second wiring portion 62 may have a structure formed by stacking multiple metal films comprising these metals or alloys. The first wiring portion 61 and the second wiring portion 62 may, for example, comprise a laminated film comprising a bonding film and a main wiring film. The bonding film comprises a Ti film, and the main wiring film comprises an Al film or an AlCu film formed on the bonding film. The thickness of the bonding film is, for example, 10 nm. The thickness of the main wiring film is, for example, 80 nm. In the AlCu film, the concentration of Cu is preferably 1 wt% or more and 20 wt% or less.

[0080] In the elastic wave device 1, from the viewpoint of reducing the resistance of the first busbar 611 and the second busbar 621, a metal film may be included on the main wiring film of each of the first busbar 611 and the second busbar 621. In addition, the thickness of each of the first wiring portion 61 and the second wiring portion 62 may be thicker than the thickness of the first electrode 51 and the second electrode 52.

[0081] (2.6) First segmented resonator, second segmented resonator

[0082] The first segmented resonator RS3 includes a first setting part 401. The first setting part 401 includes a first electrode part 501 among a plurality of electrode parts 50, and a first region 451 in the piezoelectric layer 4 on which the first electrode part 501 is provided.

[0083] The second segmented resonator RS4 includes a second setting part 402. The second setting part 402 includes a second electrode part 502 among a plurality of electrode parts 50, and a second region 452 in the piezoelectric layer 4 on which the second electrode part 502 is provided.

[0084] The support substrate 2 has a plurality of cavities 26. The plurality of cavities 26 includes a first cavity 26a and a second cavity 26b. Here, the first cavity 26a is an example of a "first energy sealing layer," and the second cavity 26b is an example of a "second energy sealing layer." The first cavity 26a exposes at least a portion of the first region 451 of the piezoelectric layer 4. The second cavity 26b exposes at least a portion of the second region 452 of the piezoelectric layer 4. In the support substrate 2, the first cavity 26a and the second cavity 26b are integrally formed. That is, there is no wall-like structure between the first cavity 26a and the second cavity 26b.

[0085] The first cavity 26a, viewed from the thickness direction D1, overlaps with the first electrode 51 and the second electrode 52 of the first electrode portion 501, and the portion between the first electrode 51 and the second electrode 52 of the first electrode portion 501 in the piezoelectric layer 4. The second cavity 26b, viewed from the thickness direction D1, overlaps with the first electrode 51 and the second electrode 52 of the second electrode portion 502, and the portion between the first electrode 51 and the second electrode 52 of the second electrode portion 502 in the piezoelectric layer 4. In other words, viewed from the thickness direction D1 of the piezoelectric layer 4, the first cavity 26a overlaps with the first region 451 where the first electrode portion 501 is located, and the second cavity 26b overlaps with the second region 452 where the second electrode portion 502 is located. Figure 2 In the piezoelectric layer 4, the first void 26a overlaps entirely with the first region 451 when viewed from the thickness direction D1, and the second void 26b overlaps entirely with the second region 452 when viewed from the thickness direction D1. However, the first void 26a and the second void 26b may overlap with at least a portion of the first region 451 and at least a portion of the second region 452, respectively. Alternatively, the void 26 may not overlap with a portion of the first wiring portion 61 and the second wiring portion 62 when viewed from the thickness direction D1.

[0086] Furthermore, the first void 26a and the second void 26b only need to overlap with the first region 451 and the second region 452 respectively when viewed from the thickness direction D1 of the piezoelectric layer 4, and at least a portion of the first region 451 and at least a portion of the second region 452 need not be exposed. Specifically, a dielectric film stacked on the first region 451 of the piezoelectric layer 4 may also be present between the first region 451 and the first void 26a, and a dielectric film stacked on the second region 452 of the piezoelectric layer 4 may also be present between the second region 452 and the second void 26b.

[0087] However, the thickness d1 of the first segmented resonator RS3 and the thickness d2 of the second segmented resonator RS4 are different. Here, the thickness d1 of the first segmented resonator RS3 is the thickness of the first mounting portion 401, and here, it is the thickness of the piezoelectric layer 4 in the first region 451. It should be noted that the thickness of the first mounting portion 401 can be the sum of the thickness of the first electrode portion 501 included in the first mounting portion 401 and the thickness of the piezoelectric layer 4 in the first region 451, i.e., the total thickness, or it can be only the thickness of the first electrode portion 501 included in the first mounting portion 401 or only the thickness of the piezoelectric layer 4 in the first region 451. In addition, when an insulating layer or the like is provided on the first main surface 41 or the second main surface 42 of the piezoelectric layer 4 in the first region 451, the thickness of the first mounting portion 401 can be only the thickness of the insulating layer, or it can be the sum of the thickness of the first electrode portion 501, the thickness of the piezoelectric layer 4 in the first region 451, and the thickness of the insulating layer in the first region 451, i.e., the total thickness. The thickness of the second segmented resonator RS4 is the thickness of the second mounting portion 402, which in this case is the thickness of the piezoelectric layer 4 in the second region 452. It should be noted that the thickness of the second mounting portion 402 can be the sum of the thickness of the second electrode portion 502 included in the second mounting portion 402 and the thickness of the piezoelectric layer 4 in the second region 452, i.e., the total thickness; or it can be only the thickness of the second electrode portion 502 included in the second mounting portion 402 or only the thickness of the piezoelectric layer 4 in the second region 452. Furthermore, if an insulating layer or the like is provided on the first main surface 41 or the second main surface 42 of the piezoelectric layer 4 in the second region 452, the thickness of the second mounting portion 402 can be only the thickness of that insulating layer, or it can be the sum of the thickness of the second electrode portion 502, the thickness of the piezoelectric layer 4 in the second region 452, and the thickness of the insulating layer in the second region 452, i.e., the total thickness. That is, when the thickness d1 of the first segmented resonator RS3 and the thickness d2 of the second segmented resonator RS4 are different, this is not limited to the case where the total thickness of the first mounting portion 401 and the total thickness of the second mounting portion 402 are different, but also includes the case where the total thickness of the first mounting portion 401 and the total thickness of the second mounting portion 402 are the same, and the thicknesses of the constituent elements included in the first mounting portion 401 and the constituent elements included in the second mounting portion 402 are different. Therefore, it is possible to make the resonant frequency of the ripple generated from the first segmented resonator RS3 different from the resonant frequency of the ripple generated from the second segmented resonator RS4. In other words, it is possible to make the resonant frequency of the useless wave of the first electrode portion 501 different from the resonant frequency of the useless wave of the second electrode portion 502, thereby dispersing the useless wave ripple.

[0088] Furthermore, the polarity of the first segmented resonator RS3 is different from that of the second segmented resonator RS4. In Embodiment 1, the polarization direction PZ1 of the piezoelectric layer 4 in the first segmented resonator RS3 is different from that of the piezoelectric layer 4 in the second segmented resonator RS4. This improves linearity.

[0089] (3) Manufacturing method of elastic wave device

[0090] In the manufacturing method of the elastic wave device 1, for example, the first to fifth steps are performed after the support substrate 2 is prepared. In the first step, a silicon oxide film 7 is formed on the first main surface 21 of the support substrate 2. In the second step, a piezoelectric substrate, which will serve as the basis for the piezoelectric layer 4, is bonded to the support substrate 2 through the silicon oxide film 7. In the third step, a piezoelectric layer 4, including a portion of the piezoelectric substrate, is formed by thinning the piezoelectric substrate. In the fourth step, a plurality of first electrodes 51, a plurality of second electrodes 52, a first wiring portion 61, and a second wiring portion 62 are formed on the first main surface 41 of the piezoelectric layer 4. In the fifth step, a cavity 26 is formed from the second main surface 22 of the support substrate 2. In the fourth step, the first electrodes 51, second electrodes 52, first wiring portions 61, and second wiring portions 62 are formed using photolithography, etching, thin film formation, and the like. In the fifth step, the predetermined area for forming the cavity 26 in the support substrate 2 is etched using photolithography and etching techniques. In the fifth step, the silicon oxide film 7 is used as an etching barrier layer to etch the support substrate 2. Then, unwanted portions of the silicon oxide film 7 are etched away to expose a portion of the second main surface 42 of the piezoelectric layer 4. Additionally, when preparing the single-crystal silicon substrate, a single-crystal silicon wafer is prepared, and the piezoelectric wafer is used as the piezoelectric substrate in the second step. In the method for manufacturing the elastic wave device 1, multiple elastic wave devices 1 (chips) are obtained by cutting a wafer comprising multiple elastic wave devices 1.

[0091] The manufacturing method of the elastic wave device 1 is just one example and is not particularly limited. For example, the piezoelectric layer 4 can also be formed using a film deposition technique. In this case, the manufacturing method of the elastic wave device 1 includes a step of forming a film of the piezoelectric layer 4 instead of the third and fourth steps. The piezoelectric layer 4 formed by the film deposition technique can be, for example, a single crystal or a twin crystal. As a film deposition technique, CVD (Chemical Vapor Deposition) is cited as an example, but it is not limited to this. In addition, the piezoelectric layer 4 is subjected to polarization treatment.

[0092] (4) Operation and characteristics of elastic wave devices

[0093] The elastic wave device 1 of Embodiment 1 is an elastic wave device utilizing a first-order thickness shear mode volume wave. As described above, the first-order thickness shear mode volume wave is a volume wave propagating in the thickness direction D1 of the piezoelectric layer 4 through thickness shear vibration of the piezoelectric layer 4, and is a volume wave with a segment number of 1 in the thickness direction D1 of the piezoelectric layer 4. The thickness shear vibration is excited by the first electrode 51 and the second electrode 52. The thickness shear vibration is excited in a defined region 45 between the first electrode 51 and the second electrode 52 in the piezoelectric layer 4 when viewed from the thickness direction D1. The thickness shear vibration can be confirmed, for example, by FEM (Finite Element Method). More specifically, for example, by using parameters of the piezoelectric layer 4 (material, Euler angle, and thickness, etc.), parameters of the first electrode 51 and the second electrode 52 (material, thickness, distance between the center lines of the first electrode 51 and the second electrode 52, etc.), the displacement distribution can be analyzed and the deformation can be analyzed by FEM, thereby confirming the thickness shear vibration. The Euler angles of piezoelectric layer 4 can be determined through analysis.

[0094] Here, refer to Figure 6A and Figure 6B This is to illustrate the difference between the Lamb wave used in conventional elastic wave devices and the aforementioned first-order thickness shear mode volume wave.

[0095] Figure 6A This is a schematic front cross-sectional view illustrating the Lamb wave propagating in the piezoelectric substrate 460 of the elastic wave device described in Patent Document 1. In this elastic wave device, the wave propagates in the piezoelectric substrate 460 as indicated by the arrow. Here, the piezoelectric substrate 460 has a first main surface 461 and a second main surface 462 that are opposite each other. Figure 6A In the diagram, the Z and X directions are shown differently from those of the piezoelectric substrate 460. Figure 6A In the diagram, the Z-direction is the thickness direction connecting the first main surface 461 and the second main surface 462 of the piezoelectric substrate 460. The X-direction is the direction in which the plurality of first electrode fingers and the plurality of second electrode fingers of the IDT electrode are arranged. In Lamb waves, elastic waves are as follows: Figure 6A As shown, the plate wave propagates along the X-direction. Therefore, in conventional elastic wave devices, since the elastic wave propagates along the X-direction, the desired resonance characteristics are obtained by placing one reflector on each side of the IDT electrode. However, in conventional elastic wave devices, propagation losses of the elastic wave occur, thus, even with miniaturization, i.e., by reducing the number of pairs of the first and second electrode fingers, the Q value decreases.

[0096] In contrast, in the elastic wave device of the reference mode, since the vibration displacement is in the thickness shear direction, therefore, as Figure 6BAs shown, the elastic wave propagates and resonates approximately along the Z-direction, which connects the first principal surface 41 and the second principal surface 42 of the piezoelectric layer 4. That is, the X-direction component of the elastic wave is significantly smaller than the Z-direction component. In the elastic wave device of the reference mode, the resonance characteristic is obtained through the propagation of the wave in this Z-direction; therefore, a reflector is not necessarily required. Thus, in the elastic wave device of the reference mode, there is no propagation loss due to wave propagation in a reflector. Therefore, in the elastic wave device of the reference mode, even if the number of electrode pairs, including the first electrode 51 and the second electrode 52, is reduced to promote miniaturization, it is difficult to cause a decrease in the Q value.

[0097] In the elastic wave device 1 of embodiment 1, such as Figure 8 As shown, the vibration width direction of the bulk wave of the first-order mode of thickness shear is opposite in the first region 451 and the second region 452 included in the defined region 45 of the piezoelectric layer 4. Figure 8 The diagram schematically illustrates a bulk wave when a voltage is applied between the first electrode 51 and the second electrode 52, making the second electrode 52 have a higher potential than the first electrode 51. The first region 451 is the region within the defined region 45 between a virtual plane VP1, orthogonal to the thickness direction D1 of the piezoelectric layer 4 and dividing the piezoelectric layer 4 into two parts, and the first main surface 41. The second region 452 is the region within the defined region 45 between the virtual plane VP1 and the second main surface 42.

[0098] Construction model 1r of an elastic wave device using a reference mode for a first-order volume wave with thickness shearing (referencing) Figure 9 The characteristics were simulated. Regarding the construction model 1r, the same labels are used for the same components as those in the elastic wave device 1 of embodiment 1, and the descriptions are omitted.

[0099] Model 1r differs from the elastic wave device 1 of Embodiment 1 in that it lacks the first wiring section 61 and the second wiring section 62. During simulation, the logarithm of the first electrode 51 and the second electrode 52 is set to infinity, and the piezoelectric layer 4 is set to rotate 120°, Y-cutting X-propagating LiNbO3.

[0100] In structural model 1r, the piezoelectric layer 4 is a film-like material, and its second principal surface 42 is in contact with air. In structural model 1r, at any cross-section along the thickness direction D1 of the piezoelectric layer 4 ( Figure 9In the model 1r, the distance between the center lines of the first electrode 51 and the second electrode 52 is set as p, and the thickness of the piezoelectric layer 4 is set as d. Furthermore, in the structural model 1r, viewed from the thickness direction D1 of the piezoelectric layer 4, the area of ​​the main portion 510 of the first electrode is set as S1, the area of ​​the main portion 520 of the second electrode is set as S2, the area of ​​the defined region 45 is set as S0, and the structural parameter defined by (S1+S2) / (S1+S2+S0) is set as MR. It should be noted that when at least one of the multiple first electrodes 51 and second electrodes 52 is formed on the piezoelectric layer 4 (in other words, when the first electrodes 51 and the second electrodes 52 are set as one pair of electrode groups, 1.5 or more electrode groups are provided on the piezoelectric layer 4), the aforementioned distance between the center lines p becomes the distance between the center lines of adjacent first electrodes 51 and second electrodes 52.

[0101] Figure 10A and Figure 10B This is a coordinate graph showing the relationship between relative bandwidth and d / p when different potentials are applied to the first electrode 51 and the second electrode 52, based on the constructed model 1r. Figure 10A and Figure 10B In the figure, the horizontal axis represents d / p, and the vertical axis represents the relative bandwidth. Figure 10A and Figure 10B This refers to the case where the piezoelectric layer 4 is rotated 120° to cut the X-axis propagating LiNbO3, but the same trend occurs even with other cutting angles. Furthermore, in the structural model 1r of the elastic wave device, when the material of the piezoelectric layer 4 is LiTaO3, the relationship between the relative bandwidth and d / p also becomes... Figure 10A and Figure 10B The same trend applies. Furthermore, in the construction model 1r of the elastic wave device, regardless of the logarithm of the first electrode 51 and the second electrode 52, the relationship between the relative bandwidth and d / p becomes... Figure 10A and Figure 10B The same trend applies. Furthermore, in the structural model 1r of the elastic wave device, not limited to the case where the second principal surface 42 of the piezoelectric layer 4 is in contact with air, but also in the case where it is in contact with the acoustic reflection layer, the relationship between the relative bandwidth and d / p also becomes related to... Figure 10A and Figure 10B The same trend.

[0102] according to Figure 10AIt can be seen that in the structural model 1r of the elastic wave device, the relative bandwidth changes drastically with an inflection point of d / p = 0.5. In the structural model 1r of the elastic wave device, when d / p > 0.5, regardless of how d / p is varied within the range of 0.5 < d / p < 1.6, the coupling coefficient remains low, and the relative bandwidth is less than 5%. On the other hand, in the structural model 1r of the elastic wave device, when d / p ≤ 0.5, if d / p is varied within the range of 0 < d / p ≤ 0.5, the coupling coefficient can be increased, making the relative bandwidth greater than 5%.

[0103] Furthermore, in the construction model 1r of the elastic wave device, when d / p ≤ 0.24, if d / p is varied within the range of 0 < d / p ≤ 0.24, the coupling coefficient can be further improved, resulting in a larger relative bandwidth. Regarding the elastic wave device 1 of Embodiment 1, as... Figure 7 As shown, if in any cross section along the thickness direction D1 of the piezoelectric layer 4, the distance between the center lines of the two pairs of first electrodes 51 and second electrodes 52 is set as p, and the thickness of the piezoelectric layer 4 is set as d, then the relationship between its relative bandwidth and d / p also follows the same trend as the relationship between the relative bandwidth and d / p of the construction model 1r of the elastic wave device.

[0104] In addition, by Figure 10A It can be seen that when d / p ≤ 0.10, if d / p is varied within the range of 0 < d / p ≤ 0.10, the coupling coefficient can be further increased, making the relative bandwidth even larger.

[0105] Figure 10B It is Figure 10A A magnified portion of the coordinate graph. For example... Figure 10B As shown, since the relative bandwidth changes with an inflection point of d / p - 0.096, when d / p ≤ 0.096, if d / p is varied within the range of 0 < d / p ≤ 0.096, the coupling coefficient can be further increased compared to the case of 0.096 < d / p, resulting in a larger relative bandwidth. Furthermore, as... Figure 10B As shown, the relative bandwidth changes with inflection points of d / p = 0.072 and 0.048. If 0.048 ≤ d / p ≤ 0.072, the change in coupling coefficient caused by the change in d / p can be suppressed, and the relative bandwidth can be made to be approximately a fixed value.

[0106] Figure 11In the construction model 1r of the elastic wave device using the thickness shear mode reference method, a graph is plotted showing the spurious levels in the frequency band between the resonant frequency and the anti-resonant frequency when the thickness d of the piezoelectric layer 4, the distance p between the center lines of the first electrode 51 and the second electrode 52, the width H1 of the first electrode, and the width H2 of the second electrode are changed. Figure 11 In the diagram, the horizontal axis represents the relative bandwidth, and the vertical axis represents the normalized spurious level. The normalized spurious level is the value obtained by normalizing the spurious level by setting the spurious level in the relative bandwidth (e.g., 22%) to 1, even if the thickness d of the piezoelectric layer 4, the width H1 of the first electrode, and the width H2 of the second electrode are changed. Figure 11 This is the case where Z-cut LiNbO3 is used as the piezoelectric layer 4, which can more appropriately excite the thickness shear mode; however, the same trend occurs with other cut angles. Furthermore, in the construction model 1r of the elastic wave device, when the material of the piezoelectric layer 4 is LiTaO3, the relationship between the normalized stray level and the relative bandwidth also becomes... Figure 11 The same trend applies. Furthermore, in the construction model 1r of the elastic wave device, regardless of the logarithm of the first electrode 51 and the second electrode 52, the relationship between the normalized spurious level and the relative bandwidth becomes... Figure 11 The same trend applies. Furthermore, in the structural model 1r of the elastic wave device, not limited to the case where the second principal surface 42 of the piezoelectric layer 4 is in contact with air, but also in the case where it is in contact with the acoustic reflection layer, the relationship between the normalized stray level and the relative bandwidth also becomes... Figure 11 The same trend.

[0107] according to Figure 11 It can be seen that when the relative bandwidth exceeds 17%, the normalized spurious level converges to 1. This means that when the relative bandwidth is above 17%, such as Figure 12 As illustrated by the frequency characteristics of the impedance, there are certain secondary resonances in the frequency band between the resonant frequency and the anti-resonant frequency. Figure 12 This refers to the frequency response of the impedance when Z-cut LiNbO3 with Euler angles of (0°, 0°, 90°) is used as the piezoelectric layer 4, and d / p = 0.08 and MR = 0.35 are set. Figure 12 In the image, the part of the secondary resonance is surrounded by a dashed line.

[0108] As described above, when the relative bandwidth exceeds 17%, even if the thickness d of the piezoelectric layer 4, the distance p between the centerlines of the first electrode 51 and the second electrode 52, the width H1 of the first electrode, and the width H2 of the second electrode are changed, a large amount of spurious emissions are still present in the frequency band between the resonant frequency and the anti-resonant frequency. Such spurious emissions are generated primarily by harmonics in the planar direction, mainly in the opposite directions of the first electrode 51 and the second electrode 52. Therefore, from the viewpoint of suppressing spurious emissions in the frequency band, the relative bandwidth is preferably 17% or less. The elastic wave device 1 of Embodiment 1 also shows the same trend as the construction model 1r of the elastic wave device regarding the relationship between the normalized spurious emission level and the relative bandwidth; therefore, the relative bandwidth is preferably 17% or less.

[0109] Figure 13 This indicates that, under the following conditions, a first distribution region DA1 with a relative bandwidth exceeding 17% and a second distribution region DA2 with a relative bandwidth below 17% are defined as follows: In the construction model 1r of the elastic wave device, Z-cut LiNbO3 is used as the piezoelectric layer 4, and the thickness d of the piezoelectric layer 4, the distance p between the centerlines of the first electrode 51 and the second electrode 52, the width H1 of the first electrode, and the width H2 of the second electrode are varied. Figure 13 In the first distribution region DA1 and the second distribution region DA2, the point densities are made different, with the point density in the first distribution region DA1 being higher than the point density in the second distribution region DA2. Additionally, in... Figure 13 In the diagram, the approximate straight line DL1, representing the boundary between the first distribution region DA1 and the second distribution region DA2, is shown as a dashed line. The approximate straight line DL1 is represented by the formula MR = 1.75 × (d / p) + 0.075. Therefore, in the structural model 1r of the elastic wave device, by satisfying the condition MR ≤ 1.75 × (d / p) + 0.075, it is easy to make the relative bandwidth less than 17%. Figure 13 In the case where Z-cut LiNbO3 is used as the piezoelectric layer 4 to more appropriately excite the thickness shearing mode, the trend is the same for other cutting angles. Furthermore, in the construction model 1r of the elastic wave device, when the material of the piezoelectric layer 4 is LiTaO3, the approximate straight line DL1 is also the same. Furthermore, in the construction model 1r of the elastic wave device, the approximate straight line DL1 is the same regardless of the logarithm of the first electrode 51 and the second electrode 52. Furthermore, in the construction model 1r of the elastic wave device, the approximate straight line DL1 is the same not only when the second principal surface 42 of the piezoelectric layer 4 is in contact with air, but also when it is in contact with the acoustic reflection layer. Similar to the construction model 1r of the elastic wave device, the elastic wave device 1 of Embodiment 1 easily achieves a relative bandwidth of 17% or less by satisfying the condition MR ≤ 1.75 × (d / p) + 0.075. It should be noted that... Figure 13In the diagram, the approximate line DL2 (hereinafter also referred to as the second approximate line DL2), shown as a dashed line distinct from the approximate line DL1 (hereinafter also referred to as the first approximate line DL1), represents the line used to reliably ensure that the relative bandwidth is below 17%. The second approximate line DL2 is represented by the formula MR = 1.75 × (d / p) + 0.05. Therefore, in the construction model 1r of the elastic wave device in the reference mode and the elastic wave device 1 of Embodiment 1, by satisfying the condition MR ≤ 1.75 × (d / p) + 0.05, it is possible to reliably ensure that the relative bandwidth is below 17%.

[0110] (5) Effect

[0111] The elastic wave device 1 of Embodiment 1 includes a piezoelectric layer 4, a first electrode 51, and a second electrode 52, and utilizes thickness shearing of a first-order mode bulk wave. Furthermore, the elastic wave device 1 includes a first segmented resonator RS3 and a second segmented resonator RS4. Additionally, a first cavity 26a, which overlaps with at least a portion of the first region 451 of the piezoelectric layer 4 when viewed from the thickness direction of the piezoelectric layer 4, and a second cavity 26b, which overlaps with at least a portion of the second region 452 of the piezoelectric layer 4, are formed on the support substrate 2. Moreover, the first cavity 26a and the second cavity 26b are integrally formed on the support substrate 2. Therefore, even with miniaturization, the Q value can be improved, and further miniaturization can be achieved when forming the first segmented resonator RS3 and the second segmented resonator RS4.

[0112] The elastic wave device 1 of Embodiment 1 includes a piezoelectric layer 4, a first electrode 51, and a second electrode 52. The distance p between the centerlines of the first electrode 51 and the second electrode 52, and the thickness d of the piezoelectric layer 4, are such that d / p is 0.5 or less. Furthermore, the elastic wave device 1 includes a first segmented resonator RS3 and a second segmented resonator RS4. Additionally, a first cavity 26a overlapping at least a portion of the first region 451 of the piezoelectric layer 4, and a second cavity 26b overlapping at least a portion of the second region 452 of the piezoelectric layer 4, are formed on the support substrate 2. The first cavity 26a and the second cavity 26b are integrally formed on the support substrate 2. Therefore, even with miniaturization, the Q value can be improved, and miniaturization can be achieved when forming the first segmented resonator RS3 and the second segmented resonator RS4.

[0113] In the elastic wave device 1 of Embodiment 1, the thickness d1 of the first segmented resonator RS3 and the thickness d2 of the second segmented resonator RS4 are different. As a result, ripple can be dispersed.

[0114] In the elastic wave device 1 of Embodiment 1, the polarity of the first segmented resonator RS3 is different from that of the second segmented resonator RS4. This further improves linearity.

[0115] In the elastic wave device 1 of Embodiment 1, d / p is 0.24 or less. As a result, the relative bandwidth can be made larger.

[0116] In the elastic wave device 1 of Embodiment 1, when viewed from above in the thickness direction D1 of the piezoelectric layer 4, the area of ​​the main portion of the first electrode is set as S1, the area of ​​the main portion of the second electrode is set as S2, the area of ​​a predetermined region is set as S0, and the structural parameter defined by (S1+S2) / (S1+S2+S0) is set as MR, MR ≤ 1.75×(d / p)+0.075 is satisfied. This allows for the suppression of spurious signals within the frequency band.

[0117] In the elastic wave device 1 of Embodiment 1, the potential of the first electrode 51 is different from that of the second electrode 52. This prevents the paired first electrodes 51 and second electrodes 52 from becoming floating potentials.

[0118] (Modification 1 of Implementation Method 1)

[0119] The following is for reference Figure 14 The elastic wave device 1a of Modified Example 1 will be described. Regarding the elastic wave device 1a of Modified Example 1, the same reference numerals are used for the same constituent elements as those of the elastic wave device 1 of Embodiment 1, and the description is omitted.

[0120] The elastic wave device 1a of Modified Example 1 differs from the elastic wave device 1 of Embodiment 1 in that each of the multiple elastic wave resonators 5 also has two reflectors 8.

[0121] The two reflectors 8 are short-circuit gratings. Each reflector 8 is not intended to reflect bulk waves of the first shear mode, but rather to reflect unwanted surface acoustic waves propagating along the first principal surface 41 of the piezoelectric layer 4. One of the two reflectors 8 is located on the side of the first electrode 51 located at the end, opposite to the side of the second electrode 52, in the direction of propagation of the unwanted surface acoustic waves of the elastic wave device 1a. The remaining reflector 8 is located on the side of the second electrode 52 located at the end, opposite to the side of the first electrode 51, in the direction of propagation of the unwanted surface acoustic waves of the elastic wave device 1a.

[0122] Each reflector 8 has a plurality of (e.g., four) electrode fingers 81, one end of each electrode finger 81 being short-circuited to the other, and the other end being short-circuited to the other. The number of electrode fingers 81 in each reflector 8 is not particularly limited.

[0123] Each reflector 8 is conductive. The material of each reflector 8 is, for example, Al, Cu, Pt, Au, Ag, Ti, Ni, Cr, Mo, W, or an alloy primarily composed of any of these metals. Alternatively, each reflector 8 may have a structure formed by stacking multiple metal films comprising these metals or alloys. Each reflector 8, for example, includes a laminated film comprising a bonding film and a main electrode film. The bonding film comprises a Ti film formed on the piezoelectric layer 4, and the main electrode film comprises an Al film formed on the bonding film. The thickness of the bonding film is, for example, 10 nm. The thickness of the main electrode film is, for example, 80 nm.

[0124] Furthermore, in the elastic wave device 1a of Modified Example 1, each reflector 8 is a short-circuit grating, but it is not limited to this. For example, it can also be an open grating, a positive and negative reflection type grating, or a grating composed of a combination of a short-circuit grating and an open grating. In addition, in the elastic wave device 1a, each elastic wave resonator 5 has two reflectors 8, but it can also be a structure that has only one of the two reflectors 8.

[0125] (Modification 2 of Implementation Method 1)

[0126] As a variation of implementation method 1, such as Figure 15 As shown, the first electrode 51 and the second electrode 52 in the second segmented resonator RS4 can also be located on the opposite side to the first electrode 51 and the second electrode 52 in the first segmented resonator RS3. Figure 15 In the example, the first electrode 51 and the second electrode 52 of the first segmented resonator RS3 are disposed on the first main surface 41 of the piezoelectric layer 4, and the first electrode 51 and the second electrode 52 of the second segmented resonator RS4 are disposed on the second main surface 42 of the piezoelectric layer 4. In the modified example 2, the polarization direction PZ1 of the piezoelectric layer 4 in the first segmented resonator RS3 is the same as the polarization direction PZ2 of the piezoelectric layer 4 in the second segmented resonator RS4. This further improves the linearity.

[0127] (Modification 3 of Implementation Method 1)

[0128] As a variation of embodiment 1, the distance p between the center lines in the first segmented resonator RS3 and the distance p between the center lines in the second segmented resonator RS4 can also be different. This allows for ripple dispersion without affecting the main resonance.

[0129] (Modification 4 of Implementation Method 1)

[0130] Figure 1 The diagram shows the structure of the series arm resonators (first segmented resonator RS3 and second segmented resonator RS4) overlapping with the same cavity 26 in a top view, but as a variation of embodiment 1, such as... Figure 16As shown, it is also possible that the series arm resonator RS1 and the parallel arm resonator RS2 overlap with the same cavity 26 when viewed from above.

[0131] (Modification 5 of Implementation Method 1)

[0132] As a variation of implementation method 1, such as Figure 17 As shown, regarding the first segmented resonator RS3 and the second segmented resonator RS4, the second bus 621 in the pair of bus bars (first bus bar 611 and second bus bar 621) of the first segmented resonator RS3 and the first bus bar 611 in the pair of bus bars (first bus bar 611 and second bus bar 621) of the second segmented resonator RS4 can also be common interstage bus bar 63.

[0133] (Implementation Method 2)

[0134] The following is for reference Figure 18 and Figure 19 The elastic wave device 1b of Embodiment 2 will be described. Regarding the elastic wave device 1b of Embodiment 2, the same reference numerals are used for the same constituent elements as those of the elastic wave device 1 of Embodiment 1, and descriptions are omitted.

[0135] (1) Structure of elastic wave device

[0136] like Figure 18 As shown, the elastic wave device 1b of Embodiment 2 differs from the elastic wave device 1 of Embodiment 1 in that it has an acoustic reflection layer 3 sandwiched between the support substrate 2 and the piezoelectric layer 4.

[0137] In the elastic wave device 1b of embodiment 2, an acoustic reflection layer 3 is disposed on the first main surface 21 of the support substrate 2, and a piezoelectric layer 4 is disposed on the acoustic reflection layer 3. In the elastic wave device 1b, the elastic wave resonator 5 includes at least one pair of electrodes (first electrode 51, second electrode 52) and the piezoelectric layer 4. In the elastic wave device 1b, the elastic wave resonator 5 also has the aforementioned acoustic reflection layer 3.

[0138] The acoustic reflective layer 3 has a first acoustic reflective layer 3a that overlaps with the first region 451 when viewed from above in the thickness direction of the piezoelectric layer 4, and a second acoustic reflective layer 3b that overlaps with the second region 452. The first acoustic reflective layer 3a is an example of a "first energy sealing layer", and the second acoustic reflective layer 3b is an example of a "second energy sealing layer". The first acoustic reflective layer 3a and the second acoustic reflective layer 3b are integrally formed.

[0139] like Figure 19As shown, the elastic wave device 1b of Embodiment 2 is also an elastic wave filter (here, a trapezoidal filter) similar to the elastic wave device 1 of Embodiment 1. The elastic wave device 1b has an input terminal 15, an output terminal 16, and a first path 12 (see reference 12) connecting the input terminal 15 and the output terminal 16. Figure 3 Multiple (two) series arm resonators RS1 on the first path 12, and multiple (two) nodes N1, N2 (refer to) Figure 3 Multiple (two) second paths 13, 14 (refer to) connected to ground (grounding terminals 17, 18) Figure 3 Each of the two parallel-arm resonators RS2 is provided with one. The grounding terminals 17 and 18 can also be combined into a single ground.

[0140] Multiple series-arm resonators RS1 each have a first segmented resonator RS3 and a second segmented resonator RS4. The first segmented resonator RS3 and the second segmented resonator RS4 are connected in series. It should be noted that in each series-arm resonator RS1, the first segmented resonator RS3 and the second segmented resonator RS4 can also be connected in parallel. Similarly, multiple parallel-arm resonators RS2 can each have a first segmented resonator and a second segmented resonator. In each parallel-arm resonator RS2, the first segmented resonator and the second segmented resonator are connected in series or in parallel.

[0141] In the elastic wave device 1b, the first segmented resonator RS3 and the second segmented resonator RS4 in the plurality of series-arm resonators RS1, and the plurality of parallel-arm resonators RS2 are all elastic wave resonators 5. Each of the plurality of elastic wave resonators 5 includes at least one pair of electrodes (first electrode 51, second electrode 5). In the elastic wave device 1b, the piezoelectric layer 4 is used in all of the plurality of elastic wave resonators 5. Additionally, in the elastic wave device 1b, the acoustic reflection layer 3 is segmented in all of the plurality of elastic wave resonators 5. The resonant frequency of the parallel-arm resonator RS2 is lower than the resonant frequency of the series-arm resonator RS1.

[0142] (2) Acoustic reflector layer

[0143] like Figure 18 As shown, the acoustic reflection layer 3 is positioned opposite to a plurality of first electrodes 51 and a plurality of second electrodes 52 in the thickness direction D1 of the piezoelectric layer 4.

[0144] The acoustic reflection layer 3 has the function of suppressing the leakage of bulk waves (the aforementioned thickness shear first-order mode bulk waves) excited by the paired first electrode 51 and second electrode 52 to the support substrate 2. By including the acoustic reflection layer 3, the elastic wave device 1b can improve the sealing effect of elastic wave energy into the piezoelectric layer 4. Therefore, compared with the case without the acoustic reflection layer 3, the elastic wave device 1b can reduce losses and improve the Q value.

[0145] The acoustic reflective layer 3 has a stacked structure in which at least one (three) low acoustic impedance layers 31 and at least one (two) high acoustic impedance layers 32 are arranged alternately in the thickness direction D1 of the piezoelectric layer 4. The acoustic impedance of the low acoustic impedance layer 31 is lower than that of the high acoustic impedance layer 32.

[0146] For ease of explanation, the two high acoustic impedance layers 32 in the acoustic reflection layer 3 are sometimes referred to as the first high acoustic impedance layer 321 and the second high acoustic impedance layer 322, in order of proximity to the first main surface 21 of the support substrate 2. Alternatively, the three low acoustic impedance layers 31 are sometimes referred to as the first low acoustic impedance layer 311, the second low acoustic impedance layer 312, and the third low acoustic impedance layer 313, in order of proximity to the first main surface 21 of the support substrate 2.

[0147] In the acoustic reflection layer 3, a first low acoustic impedance layer 311, a first high acoustic impedance layer 321, a second low acoustic impedance layer 312, a second high acoustic impedance layer 322, and a third low acoustic impedance layer 313 are arranged sequentially from the support substrate 2 side. Therefore, the acoustic reflection layer 3 can reflect bulk waves (thickness shear first-order mode bulk waves) from the piezoelectric layer 4 at the interfaces of the third low acoustic impedance layer 313 and the second high acoustic impedance layer 322, the second high acoustic impedance layer 322 and the second low acoustic impedance layer 312, the second low acoustic impedance layer 312 and the first high acoustic impedance layer 321, and the first high acoustic impedance layer 321 and the first low acoustic impedance layer 311, respectively.

[0148] The material of the plurality of high acoustic impedance layers 32 is, for example, Pt (platinum). The material of the plurality of low acoustic impedance layers 31 is, for example, silicon oxide. The thickness of each of the plurality of high acoustic impedance layers 32 is, for example, 94 nm. The thickness of each of the plurality of low acoustic impedance layers 31 is, for example, 188 nm. Since the two high acoustic impedance layers 32 are each formed of platinum, the acoustic reflection layer 3 also includes two conductive layers.

[0149] The material of the multiple high acoustic impedance layers 32 is not limited to Pt, but can also be metals such as W (tungsten) and Ta (tantalum). Furthermore, the material of the multiple high acoustic impedance layers 32 is not limited to metals, but can also be insulators.

[0150] Furthermore, the multiple high acoustic impedance layers 32 are not limited to being made of the same material; for example, they can also be made of different materials. Similarly, the multiple low acoustic impedance layers 31 are not limited to being made of the same material; for example, they can also be made of different materials.

[0151] Furthermore, the number of high acoustic impedance layers 32 and low acoustic impedance layers 31 in the acoustic reflection layer 3 is not limited to two or three; it can also be one, three or more, or four or more. Additionally, the number of high acoustic impedance layers 32 and low acoustic impedance layers 31 is not limited to being different; they can be the same, or the number of low acoustic impedance layers 31 can be one less than the number of high acoustic impedance layers 32. Furthermore, the thickness of each of the high acoustic impedance layers 32 and low acoustic impedance layers 31 is appropriately set according to the desired frequency of the elastic wave device 1 and the materials used in the high acoustic impedance layers 32 and low acoustic impedance layers 31 respectively, so that good reflection is achieved in the acoustic reflection layer 3.

[0152] (3) Manufacturing method of elastic wave device

[0153] In the manufacturing method of the elastic wave device 1b, for example, the first to fourth processes are performed after the support substrate 2 is prepared. In the first process, an acoustic reflection layer 3 is formed on the first main surface 21 of the support substrate 2. In the second process, a piezoelectric substrate, which will serve as the basis for the piezoelectric layer 4, is bonded to the support substrate 2 via the acoustic reflection layer 3. In the third process, a piezoelectric layer 4, including a portion of the piezoelectric substrate, is formed by thinning the piezoelectric substrate. In the fourth process, a plurality of first electrodes 51, a plurality of second electrodes 52, a first wiring portion 61, and a second wiring portion 62 are formed on the piezoelectric layer 4. In the first to fourth processes, a silicon wafer is used as the support substrate 2. In the second process, a piezoelectric wafer is used as the piezoelectric substrate. In the manufacturing method of the elastic wave device 1b, a plurality of elastic wave devices 1b (chips) are obtained by dicing a wafer including a plurality of elastic wave devices 1b.

[0154] The manufacturing method of the elastic wave device 1b is just one example and is not particularly limited. For example, the piezoelectric layer 4 can also be formed using a film deposition technique. In this case, the manufacturing method of the elastic wave device 1b can also include a step of forming a film of the piezoelectric layer 4 instead of the second and third steps. The piezoelectric layer 4 formed by the film deposition technique can be, for example, a single crystal or a twin crystal. As a film deposition technique, CVD is an example, but it is not limited to this. In addition, the piezoelectric layer 4 is subjected to a polarization treatment.

[0155] (4) Effect

[0156] The elastic wave device 1b of Embodiment 2, like the elastic wave device 1 of Embodiment 1, utilizes a body wave with a first-order mode sheared by thickness. Therefore, in the elastic wave device 1b of Embodiment 2, the resonant frequency is not limited by the distance between the centerlines of the paired first electrode 51 and second electrode 52, and the resonant frequency can be increased by reducing the thickness of the piezoelectric layer 4. Thus, high-frequency operation can be achieved without increasing the planar size of the elastic wave device 1b.

[0157] In the elastic wave device 1b of Embodiment 2, since the second principal surface 42 of the piezoelectric layer 4 in the elastic wave resonator 5 is constrained by the acoustic reflection layer 3, unwanted waves can be suppressed. Furthermore, in the elastic wave device 1b of Embodiment 2, the material of the piezoelectric layer 4 is LiNbO3 or LiTaO3, and the material of the low acoustic impedance layer 31 is silicon oxide. Here, the frequency-temperature characteristics of LiNbO3 and LiTaO3 each have a negative slope, while the frequency-temperature characteristics of silicon oxide have a positive slope. Therefore, in the elastic wave device 1b of Embodiment 2, the absolute value of the TCF (Temperature Coefficient of Frequency) can be reduced, and the frequency-temperature characteristics can be improved.

[0158] The elastic wave device 1b of Embodiment 2 includes an acoustic reflection layer 3 disposed between the support substrate 2 and the piezoelectric layer 4.

[0159] (Modification 1 of Implementation Method 2)

[0160] In the elastic wave device 1b of embodiment 2, the acoustic reflection layer 3 is used in multiple elastic wave resonators 5, but the high acoustic impedance layer 32 (second high acoustic impedance layer 322) closest to the piezoelectric layer 4 among multiple high acoustic impedance layers 32 can also be separated according to each elastic wave resonator 5.

[0161] (Modification 2 of Implementation Method 2)

[0162] The following is for reference Figure 20 The elastic wave device 1c of Modification 2 of Embodiment 2 will be described. Regarding the elastic wave device 1c of Modification 2, the same reference numerals are used for the same constituent elements as those of the elastic wave device 1b of Embodiment 2, and the description is omitted.

[0163] The elastic wave device 1c of Embodiment 2 differs from the elastic wave device 1b of Embodiment 2 in that each of the plurality of elastic wave resonators 5 also has two reflectors 8. The structure of each reflector 8 is the same as that of each reflector 8 in the elastic wave device 1a of Embodiment 1.

[0164] As another variation of Embodiment 2, similarly to Variation 4 of Embodiment 1, the series arm resonator RS1 and the parallel arm resonator RS2 overlap with the same cavity 26 when viewed from above. Alternatively, similarly to Variation 5 of Embodiment 1, regarding the first split resonator RS3 and the second split resonator RS4, the second bus 621 of the pair of bus bars (first bus bar 611 and second bus bar 621) of the first split resonator RS3 and the first bus bar 611 of the pair of bus bars (first bus bar 611 and second bus bar 621) of the second split resonator RS4 are common interstage bus bars 63.

[0165] The above-described embodiments 1 and 2 are merely one embodiment of the various embodiments of the present invention. Embodiments 1 and 2 described above are acceptable as long as they achieve the purpose of the present invention, and various modifications can be made according to design, etc.

[0166] For example, in the elastic wave device 1 of Embodiment 1, the piezoelectric layer 4 is bonded to the support substrate 2 through the silicon oxide film 7, but the silicon oxide film 7 is not an essential component.

[0167] In addition, in the elastic wave device 1 of Embodiment 1, the cavity 26 is formed to penetrate the support substrate 2 along the thickness direction of the support substrate 2, but it is not limited to this. It may not penetrate the support substrate 2, but may be formed by the internal space of the recess formed on the first main surface 21 of the support substrate 2.

[0168] Furthermore, in the elastic wave devices 1 to 1c, the cross-sectional shape of the first electrode 51 and the second electrode 52 is rectangular, but not limited to this. Here, the cross-sectional shape is, for example, the shape in the cross-section along the thickness direction D1 and the second direction D2 of the piezoelectric layer 4. The first electrode 51 and the second electrode 52 may also be, for example, as shown in... Figures 21A to 21D As shown in any of the figures, the shape is such that the width at the bottom is wider than the width at the top. Therefore, it is possible to achieve this without increasing the size of the first main surface 511 of the first electrode 51 (see Figure 51). Figure 7 ) and the first main surface 521 of the second electrode 52 (refer to Figure 7 In the state of the width of ), the capacitance between the paired first electrode 51 and second electrode 52 is increased.

[0169] Figure 21A The first electrode 51 and the second electrode 52 shown have a portion with a substantially fixed width at the upper end and a portion with a gradually increasing width at the lower end. Furthermore, Figure 21B The first electrode 51 and the second electrode 52 shown are trapezoidal in cross-section. Additionally, Figure 21C The first electrode 51 and the second electrode 52 shown are shaped with extended ends, and their two sides in the width direction are curved surfaces. Furthermore, Figure 21DThe first electrode 51 and the second electrode 52 shown have a trapezoidal section on the upper end side and a trapezoidal section on the lower end side that is wider than the trapezoidal section on the upper end side.

[0170] In addition, such as Figures 22A to 22C As shown in any of the figures, the elastic wave devices 1-1c may also include a dielectric film 9 covering the first main surface 41 of the piezoelectric layer 4, the first electrode 51 on the first main surface 41, and the second electrode 52 on the first main surface 41. By including the dielectric film 9, the elastic wave devices 1-1c can increase the capacitance between the paired first electrode 51 and second electrode 52. Figure 22A In this process, the thickness of the dielectric film 9 is thinner than the thickness of the first electrode 51 and the second electrode 52, and the surface of the dielectric film 9 has an uneven shape along the shape of the substrate. Figure 22B In this process, the surface of the dielectric film 9 is planarized to become planar. Figure 22C In the process, the thickness of the dielectric film 9 is greater than the thickness of the first electrode 51 and the second electrode 52, and the surface of the dielectric film 9 has an uneven shape along the shape of the substrate.

[0171] Furthermore, in the elastic wave devices 1 to 1c, the cross-sectional shape of the first electrode 51 and the cross-sectional shape of the second electrode 52 may be different. Here, the cross-sectional shape is, for example, the shape in the cross-section along the thickness direction D1 and the second direction D2 of the piezoelectric layer 4.

[0172] In addition, in the elastic wave devices 1 to 1c, the elastic wave resonator 5 has a plurality of first electrodes 51 and a plurality of second electrodes 52, but is not limited thereto, and may have at least one pair of electrodes (first electrode 51 and second electrode 52).

[0173] Furthermore, in the elastic wave devices 1 to 1c, the shapes of the first electrode 51 and the second electrode 52 may differ for each elastic wave resonator 5. Additionally, the shapes of the first electrode 51 and the second electrode 52 may differ in the elastic wave resonator 5 constituting the series arm resonator RS1 and the elastic wave resonator 5 constituting the parallel arm resonator RS2.

[0174] Furthermore, the first electrode 51 and the second electrode 52 are not limited to being straight when viewed from the thickness direction D1 of the piezoelectric layer 4. For example, the first electrode 51 and the second electrode 52 may also be curved, or may have a shape that includes both straight and curved portions.

[0175] (Way)

[0176] The following methods are disclosed in this specification.

[0177] The elastic wave device (1-1c) of the first type includes a piezoelectric layer (4), a first electrode (51), and a second electrode (52). The first electrode (51) and the second electrode (52) are positioned opposite each other in a direction (long side direction D2) intersecting the thickness direction (D1) of the piezoelectric layer (4). The elastic wave device (1-1c) utilizes a thickness-sheared first-order mode bulk wave. The material of the piezoelectric layer (4) is lithium niobate or lithium tantalate. The elastic wave device (1-1c) includes multiple electrode portions (50) including the first electrode (51) and the second electrode (52). The elastic wave device (1-1c) also includes a first segmented resonator (RS3), a second segmented resonator (RS4), and a support substrate (2). The first segmented resonator (RS3) and the second segmented resonator (RS4) are connected in series without connecting other resonators to each other, or they are connected in parallel with each other at the same connection node on the path (first path 12) connecting the input terminal (15) and the output terminal (16). The support substrate (2) has a first main surface (21) and a second main surface (22) facing each other. The first segmented resonator (RS3) includes a first mounting portion (401). The first mounting portion (401) includes a first electrode portion (501) among a plurality of electrode portions (50) and a first region (451) in the piezoelectric layer (4) in which the first electrode portion (501) is mounted. The second segmented resonator (RS4) includes a second mounting portion (402). The second mounting portion (402) includes a second electrode portion (502) among a plurality of electrode portions (50) and a second region (452) in the piezoelectric layer (4) in which the second electrode portion (502) is mounted. The piezoelectric layer (4) is disposed directly or indirectly on the support substrate (2). The support substrate (2) has a first energy sealing layer (first void 26a; first acoustic reflection layer 3a) and a second energy sealing layer (second void 26b; second acoustic reflection layer 3b). The first energy-sealing layer overlaps with at least a portion of the first region (451) of the piezoelectric layer (4). The second energy-sealing layer overlaps with at least a portion of the second region (452) of the piezoelectric layer (4). The first energy-sealing layer and the second energy-sealing layer are integrally formed in the support substrate (2).

[0178] According to the elastic wave device (1-1c) of the first method, even with miniaturization, the Q value can be improved, and further miniaturization can be achieved when forming the first segmented resonator (RS3) and the second segmented resonator (RS4).

[0179] The second type of elastic wave device (1-1c) includes a piezoelectric layer (4), a first electrode (51), and a second electrode (52). The first electrode (51) and the second electrode (52) are positioned opposite each other in a direction (second direction D2) intersecting the thickness direction (D1) of the piezoelectric layer (4). The first electrode (51) and the second electrode (52) are adjacent electrodes. When the distance between the center lines of the first electrode (51) and the second electrode (52) is set as p and the thickness of the piezoelectric layer (4) is set as d in any cross-section along the thickness direction (D1) of the piezoelectric layer (4), d / p is 0.5 or less. The material of the piezoelectric layer (4) is lithium niobate or lithium tantalate. The elastic wave device (1-1c) includes multiple electrode portions (50) including the first electrode (51) and the second electrode (52). The elastic wave device (1-1c) also includes a first segmented resonator (RS3), a second segmented resonator (RS4), and a support substrate (2). The first segmented resonator (RS3) and the second segmented resonator (RS4) are connected in series without any other resonators connected to each other, or they are connected in parallel with each other at the same connection node on the path (first path 12) connecting the input terminal (15) and the output terminal (16). The support substrate (2) has a first main surface (21) and a second main surface (22) that are opposite each other. The first segmented resonator (RS3) includes a first mounting portion (401). The first mounting portion (401) includes a first electrode portion (501) among a plurality of electrode portions (50) and a first region (451) in the piezoelectric layer (4) in which the first electrode portion (501) is mounted. The second segmented resonator (RS4) includes a second mounting portion (402). The second mounting portion (402) includes a second electrode portion (502) among a plurality of electrode portions (50) and a second region (452) in the piezoelectric layer (4) in which the second electrode portion (502) is mounted. The piezoelectric layer (4) is disposed directly or indirectly on the support substrate (2). The support substrate (2) has a first energy sealing layer (first void 26a; first acoustic reflection layer 3a) and a second energy sealing layer (second void 26b; second acoustic reflection layer 3b). The first energy sealing layer exposes at least a portion of a first region (451) of the piezoelectric layer (4). The second energy sealing layer exposes at least a portion of a second region (452) of the piezoelectric layer (4). In the support substrate (2), the first energy sealing layer and the second energy sealing layer are integrally formed.

[0180] According to the elastic wave device (1-1c) of the second method, even with miniaturization, the Q value can be improved, and further miniaturization can be achieved when forming the first segmented resonator (RS3) and the second segmented resonator (RS4).

[0181] The third type of elastic wave device (1-1c) is based on either the first or second type, wherein the thickness (d1) of the first segmented resonator (RS3) is the same as the thickness of the first mounting section (401). The thickness of the second segmented resonator (RS4) is the same as the thickness of the second mounting section (402). The thickness (d1) of the first segmented resonator (RS3) and the thickness (d2) of the second segmented resonator (RS4) are different from each other.

[0182] According to the third-party elastic wave device (1~1c), the ripple can be dispersed.

[0183] The elastic wave device of the fourth type (1 to 1c) is based on any one of the first to third types, wherein the polarity of the first segmented resonator (RS3) is different from that of the second segmented resonator (RS4).

[0184] According to the elastic wave device of the fourth method (1-1c), the linearity can be further improved.

[0185] The fifth type of elastic wave device (1b; 1c) is based on any one of the first to fourth types, wherein at least one of the first energy sealing layer and the second energy sealing layer is an acoustic reflection layer (3). The acoustic reflection layer (3) has a high acoustic impedance layer (32) and a low acoustic impedance layer (31). The acoustic impedance of the low acoustic impedance layer (31) is lower than that of the high acoustic impedance layer (32).

[0186] According to the elastic wave device of the fifth method (1b; 1c), the linearity can be further improved.

[0187] The sixth type of elastic wave device (1; 1a) is based on any one of the first to fourth types, wherein the first energy sealing layer and the second energy sealing layer are voids (26).

[0188] The elastic wave device (1-1c) of the seventh type is based on the second type, wherein the distance (p) between the center lines in the first segmented resonator (RS3) is different from the distance (p) between the center lines in the second segmented resonator (RS4).

[0189] According to the elastic wave device of the seventh method (1-1c), the ripple can be dispersed without affecting the main resonance.

[0190] The elastic wave device (1 to 1c) of the eighth type is based on the second type, wherein d / p is 0.24 or less.

[0191] According to the elastic wave device of the eighth method (1-1c), the relative bandwidth can be made larger.

[0192] The elastic wave device (1-1c) of the ninth embodiment is based on the eighth embodiment, wherein the first electrode (51) and the second electrode (52) are adjacent electrodes. The first electrode (51) has a first electrode main portion (510). The first electrode main portion (510) intersects the second electrode (52) in the direction (long side direction D2) opposite to the first electrode (51). The second electrode (52) has a second electrode main portion (520). The second electrode main portion (520) intersects the first electrode (51) in the direction (long side direction D2) opposite to the first electrode (51). The piezoelectric layer (4) has a defined region (45). The specified region (45), viewed from the thickness direction (D1) of the piezoelectric layer (4), intersects both the first electrode (51) and the second electrode (52) in the direction opposite to each other (long side direction D2) in the piezoelectric layer (4), and is located between the first electrode (51) and the second electrode (52). Viewed from the thickness direction (D1) of the piezoelectric layer (4), with the area of ​​the main portion of the first electrode (510) set as S1, the area of ​​the main portion of the second electrode (520) set as S2, the area of ​​the specified region (45) set as S0, and the structural parameter defined by (S1+S2) / (S1+S2+S0) set as MR, the elastic wave device (1~1c) satisfies the following condition: MR≤1.75×(d / p)+0.075.

[0193] According to the elastic wave device of the ninth method (1 to 1c), spurious signals within the frequency band can be suppressed.

[0194] The elastic wave device (1-1c) of the tenth type is based on any one of the first to ninth types, wherein the first electrode (51) and the second electrode (52) are respectively electrodes that become signal potential or ground potential.

[0195] According to the elastic wave device (1-1c) of the tenth method, it is possible to prevent the two paired first electrodes (51) and second electrodes (52) from becoming floating potentials.

[0196] The elastic wave device (1-1c) of the eleventh type is based on any one of the first to tenth types, wherein the first energy sealing layer (first cavity 26a; first acoustic reflection layer 3a), when viewed from the thickness direction (D1), partially overlaps with the first electrode (51) and second electrode (52) of the first electrode portion (501), and the portion between the first electrode (51) and second electrode (52) of the first electrode portion (501) in the piezoelectric layer (4). The second energy sealing layer (second cavity 26b; second acoustic reflection layer 3b), when viewed from the thickness direction (D1), partially overlaps with the first electrode (51) and second electrode (52) of the second electrode portion (502), and the portion between the first electrode (51) and second electrode (52) of the second electrode portion (502) in the piezoelectric layer (4).

[0197] The elastic wave device (1-1c) of the twelfth type is based on any one of the first to eleventh types, wherein the first electrode (51) and the second electrode (52) are opposite each other on the same main surface (first main surface 41; second main surface 42) of the piezoelectric layer (4).

[0198] Explanation of reference numerals in the attached figures

[0199] 1~1c Elastic wave device;

[0200] 1r Construct the model;

[0201] 12. First path;

[0202] 13, 14 Second path;

[0203] 15 Input terminals;

[0204] 16 Output terminals;

[0205] 17 and 18 are grounding terminals;

[0206] 2 supporting base plate;

[0207] 21 First main face;

[0208] 22 Second Main Face;

[0209] 26. Hollow;

[0210] 26a First Void (First Energy Sealing Layer);

[0211] 26b Second Void (Second Energy Sealing Layer);

[0212] 3. Sound-reflecting layer;

[0213] 3a First acoustic reflection layer (first energy sealing layer);

[0214] 3b Second acoustic reflector layer (second energy sealing layer);

[0215] 31. Low acoustic impedance layer;

[0216] 311 First low acoustic impedance layer;

[0217] 312 Second low acoustic impedance layer;

[0218] 313 Third low acoustic impedance layer;

[0219] 32. High acoustic impedance layer;

[0220] 321 First high acoustic impedance layer;

[0221] 322 Second high acoustic impedance layer;

[0222] 4. Piezoelectric layer;

[0223] 401 First Setting Department;

[0224] 402 Second Setting Section;

[0225] 41 First main face;

[0226] 42 Second main face;

[0227] 45. Designated area;

[0228] 451 First Region;

[0229] 452 Second Zone;

[0230] 5. Elastic wave resonator;

[0231] 50 Electrode section;

[0232] 501 First electrode section;

[0233] 502 Second electrode section;

[0234] 51 First electrode;

[0235] 510 First electrode main part;

[0236] 511 First Main Face;

[0237] 512 Second main face;

[0238] 52 Second electrode;

[0239] 520 Second electrode main part;

[0240] 521 First main face;

[0241] 522 Second main face;

[0242] 61 First Wiring Department;

[0243] 611 First busbar;

[0244] 62 Second Wiring Section;

[0245] 621 Second busbar;

[0246] 63-level inter-busbar;

[0247] 7. Silicon oxide film;

[0248] 8. Reflectors;

[0249] 81 Electrode finger;

[0250] 9. Dielectric film;

[0251] RS1 series arm resonator;

[0252] RS2 parallel arm resonator;

[0253] RS3 First Segment Resonator;

[0254] RS4 second segmented resonator;

[0255] d, d1, d2 are thicknesses;

[0256] DA1 First Distribution Region;

[0257] DA2 second distribution region;

[0258] DL1 is an approximate straight line (the first approximate straight line);

[0259] DL2 approximates a straight line (the second approximate straight line);

[0260] H1 is the width of the first electrode;

[0261] H2 Second electrode width;

[0262] Nodes N1 and N2;

[0263] p is the distance between centerlines;

[0264] PZ1 and PZ2 polarization directions;

[0265] D1 Thickness direction (first direction);

[0266] D2 Long side direction (second direction);

[0267] D3 third direction.

Claims

1. An elastic wave device, comprising: piezoelectric layer; and The first electrode and the second electrode are positioned opposite each other in a direction that intersects the thickness direction of the piezoelectric layer. The elastic wave device utilizes thickness shearing of first-order mode volume waves. in, The piezoelectric layer is made of lithium niobate or lithium tantalate. The elastic wave device includes multiple electrode sections, each including a first electrode and a second electrode. The elastic wave device also includes: The first segmented resonator and the second segmented resonator are connected in series without any other resonators connected to each other, or connected in parallel with each other with respect to the same connection node on the path connecting the input terminal and the output terminal. as well as The supporting substrate has a first main surface and a second main surface that are opposite each other. The first segmented resonator includes a first mounting portion, which includes a first electrode portion among the plurality of electrode portions and a first region in the piezoelectric layer in which the first electrode portion is mounted. The second segmented resonator includes a second mounting portion, which includes a second electrode portion among the plurality of electrode portions and a second region in the piezoelectric layer in which the second electrode portion is mounted. The piezoelectric layer is disposed directly or indirectly on the supporting substrate. The support substrate has: A first energy-sealing layer, which, when viewed from above in the thickness direction of the piezoelectric layer, overlaps at least a portion of the first region of the piezoelectric layer; as well as A second energy-sealing layer, which, when viewed from above in the thickness direction of the piezoelectric layer, overlaps at least a portion of the second region of the piezoelectric layer. In the support substrate, the first energy sealing layer and the second energy sealing layer are integrally formed.

2. An elastic wave device, comprising: piezoelectric layer; and The first electrode and the second electrode are positioned opposite each other in a direction that intersects the thickness direction of the piezoelectric layer. The first electrode and the second electrode are adjacent to each other. In any cross-section along the thickness direction of the piezoelectric layer, if the distance between the centerlines of the first electrode and the second electrode is set to p, and the thickness of the piezoelectric layer is set to d, d / p is below 0.5 in, The piezoelectric layer is made of lithium niobate or lithium tantalate. The elastic wave device includes multiple electrode sections, each including a first electrode and a second electrode. The elastic wave device also includes: The first segmented resonator and the second segmented resonator are connected in series without any other resonators connected to each other, or connected in parallel with each other with respect to the same connection node on the path connecting the input terminal and the output terminal. as well as The supporting substrate has a first main surface and a second main surface that are opposite each other. The first segmented resonator includes a first mounting portion, which includes a first electrode portion among the plurality of electrode portions and a first region in the piezoelectric layer in which the first electrode portion is mounted. The second segmented resonator includes a second mounting portion, which includes a second electrode portion among the plurality of electrode portions and a second region in the piezoelectric layer in which the second electrode portion is mounted. The piezoelectric layer is disposed directly or indirectly on the supporting substrate. The support substrate has: A first energy-sealing layer, which, when viewed from above in the thickness direction of the piezoelectric layer, overlaps at least a portion of the first region of the piezoelectric layer; as well as A second energy-sealing layer, which, when viewed from above in the thickness direction of the piezoelectric layer, overlaps at least a portion of the second region of the piezoelectric layer. In the support substrate, the first energy sealing layer and the second energy sealing layer are integrally formed.

3. The elastic wave device according to claim 1 or 2, wherein, The thickness of the first segmented resonator is the same as the thickness of the first mounting portion. The thickness of the second segmented resonator is the same as the thickness of the second mounting portion. The thickness of the first segmented resonator is different from that of the second segmented resonator.

4. The elastic wave device according to claim 1 or 2, wherein, The polarity of the first segmented resonator is different from that of the second segmented resonator.

5. The elastic wave device according to claim 1 or 2, wherein, The first energy-sealing layer and the second energy-sealing layer are acoustic reflective layers. The acoustic reflective layer has the following characteristics: High acoustic impedance layer; as well as A low acoustic impedance layer, wherein the acoustic impedance of the low acoustic impedance layer is lower than that of the high acoustic impedance layer.

6. The elastic wave device according to claim 1 or 2, wherein, The first energy sealing layer and the second energy sealing layer are voids.

7. The elastic wave device according to claim 2, wherein, The distance between the center lines in the first segmented resonator is different from the distance between the center lines in the second segmented resonator.

8. The elastic wave device according to claim 2, wherein, The d / p ratio is below 0.

24.

9. The elastic wave device according to claim 8, wherein, The first electrode and the second electrode are adjacent to each other. The first electrode has a first electrode main portion, which intersects the second electrode in a direction opposite to the first electrode. The second electrode has a second electrode main portion, which intersects the first electrode in a direction opposite to the first electrode. The piezoelectric layer has a defined region that, when viewed from above along the thickness direction of the piezoelectric layer, intersects both the first and second electrodes in the direction opposite to the first and second electrodes, and is located between the first and second electrodes. Viewed from above along the thickness direction of the piezoelectric layer, Let the area of ​​the main part of the first electrode be S1. Let the area of ​​the main part of the second electrode be S2. Let the area of ​​the specified region be S0. When the construction parameters specified by (S1+S2) / (S1+S2+S0) are set as MR, The elastic wave device satisfies the following conditions. The conditions are as follows: MR≤1.75×(d / p)+0.

075.

10. The elastic wave device according to claim 1 or 2, wherein, The first electrode and the second electrode are respectively the electrodes that become the signal potential or the ground potential.

11. The elastic wave device according to claim 1 or 2, wherein, When viewed from above in the thickness direction, the first energy sealing layer overlaps with the first electrode and the second electrode of the first electrode portion, as well as the portion between the first electrode and the second electrode of the first electrode portion in the piezoelectric layer. The second energy sealing layer, viewed from the thickness direction, partially overlaps with the first electrode and the second electrode of the second electrode portion, as well as the portion between the first electrode and the second electrode of the second electrode portion in the piezoelectric layer.

12. The elastic wave device according to claim 1 or 2, wherein, The first electrode and the second electrode are positioned opposite each other on the same main surface of the piezoelectric layer.

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