Elastic wave device

Abstract

Even with miniaturization, the present invention improves the Q value and maintains strength. 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). The support substrate (2) has a wall portion (27) located between the first energy sealing layer and the second energy sealing layer.

Description

Technical Field

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

[0002] Conventional elastic wave devices utilizing plate waves propagating in a piezoelectric film containing LiNbO3 or LiTaO3 are known. For example, Patent Document 1 disclosed 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 containing 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, in order to achieve miniaturization, the number of the first and second electrode fingers can be reduced. However, if the number of the first and second electrode fingers is reduced, the Q value becomes lower. Furthermore, since the piezoelectric substrate is thin, the strength cannot be guaranteed.

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

[0009] Technical solutions for solving the problem

[0010] One aspect of the present invention relates to an elastic wave device comprising 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 a thickness-sheared first-order mode bulk wave. The piezoelectric layer is made of lithium niobate or lithium tantalate. The elastic wave device comprises a plurality of electrode portions including the first electrode and the second electrode. The elastic wave device further comprises a first segmented resonator and 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 setting portion. The first setting portion 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 disposed. The second segmented resonator includes a second setting portion. The second setting portion 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 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. The support substrate has a wall portion located between the first energy sealing layer and the second energy sealing layer.

[0011] One aspect of the present invention relates to an elastic wave device comprising 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 first electrode and the second electrode are adjacent electrodes. 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 defined as p, and the thickness of the piezoelectric layer is defined as d, then d / p is 0.5 or less. The material of the piezoelectric layer is lithium niobate or lithium tantalate. The elastic wave device comprises a plurality of electrode portions including the first electrode and the second electrode. The elastic wave device further comprises 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 setting portion. The first setting 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 setting portion. The second setting 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. The support substrate has a wall portion located between the first energy sealing layer and the second energy sealing layer.

[0012] Invention Effects

[0013] The elastic wave device according to the above-described manner of the present invention can improve the Q value and maintain the strength of the elastic wave device even when miniaturization is promoted. Attached Figure Description

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

[0015] Figure 2 The elastic wave device mentioned above is Figure 1 Sectional view along line A1-A1.

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

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

[0018] Figure 5 This is a top view of the main part of the resonator in the same 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 The elastic wave device mentioned above is Figure 4 Sectional view along line A2-A2.

[0021] Figure 8 This is an instructional diagram of the operation of the elastic wave device, as described above.

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

[0023] Figure 10A The structural model of the elastic wave device mentioned above is a graph showing the relationship between the relative bandwidth of the thickness shear mode and the [thickness of the piezoelectric layer] / [distance between the centerlines of the first and second electrodes]. Figure 10B The same structural model, involving the above, is a 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]. Figure 10A The horizontal axis is a magnified curve ranging from 0 to 0.2.

[0024] Figure 11 The structural model of the elastic wave device mentioned above is a graph showing the relationship between the relative bandwidth and the normalized spurious level of the thickness shear mode.

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

[0026] Figure 13 The structural model of the elastic wave device mentioned above is a diagram illustrating the distribution of relative bandwidth under the combination of [thickness of the piezoelectric layer] / [distance between the centerlines of the first and second electrodes] and structural parameters.

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

[0028] Figure 15 This is a cross-sectional view of the elastic wave device involved in variation 2 of embodiment 1.

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

[0030] Figure 17 This is a cross-sectional view of the elastic wave device according to Embodiment 2.

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

[0032] Figure 19 This is a top view of the elastic wave device involved in Variation 2 of Embodiment 2.

[0033] Figures 20A to 20D This is a cross-sectional view showing another shape of a pair of electrodes of the same elastic wave device.

[0034] Figures 21A to 21C This is a cross-sectional view showing other structural examples of the same elastic wave device. Detailed Implementation

[0035] The following implementation methods, etc., refer to Figure 1 , Figure 2 , Figures 4-9 , Figures 14-19 , Figures 20A to 20D ,as well as Figures 21A to 21C These are all schematic diagrams, and the size and thickness ratios of the constituent elements in the diagrams may not necessarily reflect the actual size ratios.

[0036] (Implementation Method 1)

[0037] The following is for reference Figures 1-5 The elastic wave device 1 according to Embodiment 1 will be described.

[0038] (1) Overall structure of elastic wave device

[0039] like Figure 1 As shown, the elastic wave device 1 according to Embodiment 1 includes a piezoelectric layer 4, a first electrode 51, and a second electrode 52. 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 number of nodes equal to 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. Viewed from the thickness direction D1, the thickness shear vibration is excited in a defined region 45 in the piezoelectric layer 4 between the first electrode 51 and the second electrode 52. 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 mode of thickness shear is large. Here, "orthogonal" is not limited to the case of strict orthogonality, 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°).

[0040] like Figure 1 as well as Figure 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 after another in the second direction D2. Figure 1 As shown, the elastic wave device 1 further includes a first wiring section 61 connected to the first electrode 51 and a second wiring section 62 connected to the second electrode 52. Multiple first electrodes 51 are commonly connected to the first wiring section 61. Multiple second electrodes 52 are commonly connected to the second wiring section 62.

[0041] 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 via a silicon oxide film 7. The plurality of first electrodes 51 and the plurality of second electrodes 52 are disposed on the piezoelectric layer 4. The elastic wave device 1 has an elastic wave resonator 5 comprising the first electrodes 51 and the second electrodes 52 and the piezoelectric layer 4 as a resonator. The support substrate 2 includes at least a portion of a cavity 26 that exposes a portion of the piezoelectric layer 4. Viewed from the thickness direction D1 of the piezoelectric layer 4, the cavity 26 overlaps entirely with the elastic wave resonator 5. Here, viewed from the thickness direction D1 of the piezoelectric layer 4, the cavity 26 overlaps with the plurality of first electrodes 51, the plurality of second electrodes 52, and a plurality of defined regions 45. Each of the plurality of defined regions 45 is the portion between a pair of first electrodes 51 and second electrodes 52.

[0042] like Figure 1 as well as Figure 3 As shown, the elastic wave device 1 according to 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, N2 on the first path 12 and ground (ground terminals 17, 18). The ground terminals 17, 18 can also be common to a single ground.

[0043] 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 formed by segmenting the series-arm resonator RS1, and are connected in series without connecting any of the parallel-arm resonators RS2. The number of segmented resonators is not limited to two, and can also be three or more.

[0044] Alternatively, in each of the multiple 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 that connects the input terminal 15 and the output terminal 16.

[0045] Furthermore, each of the multiple parallel arm resonators RS2 may also 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.

[0046] 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 each elastic wave resonators 5. Each of the plurality of elastic wave resonators 5 is a resonator comprising a plurality of first electrodes 51 and a plurality of second electrodes 52, but is not limited thereto; any resonator comprising at least one pair of electrodes (first electrode 51, second electrode 52) is acceptable. 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, it is sufficient to make the thickness of the silicon oxide film of the elastic wave resonator 5 constituting the series arm resonator RS1 thinner than the thickness of the silicon oxide film of the elastic wave resonator 5 constituting the parallel arm resonator RS2.

[0047] (2) Components of an elastic wave device

[0048] Next, the constituent elements of the elastic wave device 1 will be described with reference to the accompanying drawings.

[0049] (2.1) Support base plate

[0050] like Figure 2 As shown, the support substrate 2 supports the piezoelectric layer 4. In the elastic wave device 1 according to Embodiment 1, the support substrate 2 supports the piezoelectric layer 4, a plurality of first electrodes 51, and a plurality of second electrodes 52 via a silicon oxide film 7. Furthermore, the silicon oxide film 7 is not a necessary component. In addition to the silicon oxide film 7, other layers may be laminated between the support substrate 2 and the piezoelectric layer 4.

[0051] The support substrate 2 has a first main surface 21 and a second main surface 22 facing each other. The first main surface 21 and the second main surface 22 are facing 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.

[0052] 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 limited 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.

[0053] The support substrate 2 is not limited to a silicon substrate. For example, it can also be a quartz substrate, a glass substrate, a sapphire substrate, a lithium tantalate substrate, a lithium niobate substrate, an alumina substrate, a spinel substrate, a gallium arsenide substrate, or a silicon carbide substrate.

[0054] The support substrate 2 includes at least a portion of a cavity 26 that exposes a portion of the piezoelectric layer 4. Viewed from the thickness direction D1 of the piezoelectric layer 4, the cavity 26 overlaps with the elastic wave resonator 5. In the elastic wave device 1 according to Embodiment 1, viewed from the thickness direction D1 of the piezoelectric layer 4, the cavity 26 is larger than the elastic wave resonator 5 and overlaps entirely with the elastic wave resonator 5. Furthermore, in the elastic wave device 1 according to Embodiment 1, viewed from the thickness direction D1 of the piezoelectric layer 4, the cavity 26 also overlaps with portions of the first wiring portion 61 and the second wiring portion 62. The opening shape of the cavity 26 viewed from the thickness direction D1 of the piezoelectric layer 4 is rectangular, but not limited to this.

[0055] (2.2) Silicon oxide film

[0056] 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 according to 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 according to Embodiment 1, the support substrate 2 and the piezoelectric layer 4 are bonded via the silicon oxide film 7. The thickness of the silicon oxide film 7 is, for example, 1 μm or more and 3 μm or less.

[0057] (2.3) Piezoelectric layer

[0058] 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 are facing 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, viewed from the thickness direction D1, the piezoelectric layer 4 overlaps with the first main surface 21 of the support substrate 2 and the cavity 26. In the piezoelectric layer 4, of the first main surface 41 and the second main surface 42, 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.

[0059] 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). The piezoelectric layer 4 is, for example, Z-cut LiNbO3 or Z-cut LiTaO3. Regarding the Euler angle of the piezoelectric layer 4 (… θ,ψ), 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 by the crystal structure of the piezoelectric layer 4, or the X-axis direction, or a direction rotated 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.

[0060] The thickness of the piezoelectric layer 4 is, for example, 50 nm or more and 1000 nm or less, and for example, 400 nm.

[0061] 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 opposite to the first electrode 51 and the second electrode 52, and is located between the first electrode 51 and the second electrode 52.

[0062] (2.4) Electrode

[0063] Multiple first electrodes 51 and multiple second electrodes 52 are disposed on the first main surface 41 of the piezoelectric layer 4.

[0064] 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, among the paired first electrode 51 and second electrode 52, the first electrode 51 is a signal electrode and the second electrode 52 is a ground electrode.

[0065] In the elastic wave device 1, a plurality of first electrodes 51 and a plurality of second electrodes 52 are arranged alternately and separately 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, more than 1 μm and less than 10 μm, and for example, 3 μm. Here, "adjacent" means that the first electrodes 51 and second electrodes 52 are placed opposite each other with a gap. Regarding a group of electrodes comprising a plurality of first electrodes 51 and a plurality of second electrodes 52, any structure in which the plurality of first electrodes 51 and a plurality of second electrodes 52 are arranged separately in the second direction D2 is acceptable, or a structure in which the plurality of first electrodes 51 and a plurality of second electrodes 52 are not arranged alternately and separately from each other is also acceptable. For example, a region in which the first electrodes 51 and second electrodes 52 are arranged separately one by one and a region in which two first electrodes 51 or two second electrodes 52 are arranged in the second direction D2 may also exist.

[0066] Viewed from above along the thickness direction D1 of the piezoelectric layer 4, as shown... Figure 4 As shown, the plurality of first electrodes 51 and the plurality of second electrodes 52 are elongated strips (straight lines) with a third direction D3 orthogonal to the second direction D2 as the length direction 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.

[0067] 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.

[0068] In the elastic wave device 1 according to Embodiment 1, the width H1 of the plurality of first electrodes 51 is the same, but it is not limited to this and may be different. Furthermore, in the elastic wave device 1 according to Embodiment 1, the width H2 of the plurality of second electrodes 52 is the same, but it is not limited to this and may be different. In the elastic wave device 1 according to Embodiment 1, the width H1 of the first electrode and the width H2 of the second electrode are the same, but it is not limited to this and may be different.

[0069] Regarding the elastic wave device 1 involved 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 one, 2 to 4, 6 or more, or 50 or more.

[0070] The second direction D2 of the first electrode 51 and the second electrode 52 facing each other is preferably 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 may be positioned opposite each other in a direction orthogonal to the third direction D3, which is the longitudinal direction. Additionally, there are cases where the first electrode 51 and the second electrode 52 are not rectangular. In this case, the third direction D3, which is the longitudinal direction, may be set as the direction of the long side of the circumscribed polygon that is externally tangent to the first electrode 51 and the second electrode 52 when viewed from above. Furthermore, the term "circumscribed polygon that is externally tangent to the first electrode 51 and the second electrode 52" includes, when the first electrode 51 and the second electrode 52 are connected to the first wiring portion 61 and the second wiring portion 62, a polygon that is externally tangent to at least the portions of the first electrode 51 and the second electrode 52 other than those connected to the first wiring portion 61 or the second wiring portion 62.

[0071] like Figure 7 As shown, each of the plurality of first electrodes 51 includes a first main surface 511 and a second main surface 512 that intersect 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.

[0072] 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.

[0073] 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. Furthermore, each first electrode 51 and each second electrode 52 may also have a structure in which multiple metal films comprising these metals or alloys are stacked. Each first electrode 51 and each second electrode 52, for example, comprises a stacked film comprising a contact film and a main electrode film formed on the contact film, wherein the contact film is composed of a Ti film and the main electrode film is composed of an Al film or an AlCu film. The thickness of the contact film is, for example, 10 nm. Furthermore, 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.

[0074] (2.5) First wiring section and second wiring section

[0075] like Figure 4 As shown, the first wiring section 61 includes a first busbar 611. The first busbar 611 is a conductor section for setting a plurality of first electrodes 51 to the same potential. The first busbar 611 is an elongated strip (straight line) with the second direction D2 as its longitudinal direction. The first busbar 611 is connected to a 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, viewed from above in the thickness direction D1 of the piezoelectric layer 4, the first conductor section including the plurality of first electrodes 51 and the first busbar 611 has a comb-shaped form. The first busbar 611 is formed integrally with the plurality of first electrodes 51, but is not limited thereto.

[0076] The second wiring section 62 includes a second busbar 621. The second busbar 621 is a conductor section for setting a plurality of second electrodes 52 to the same potential. The second busbar 621 is an elongated strip (straight line) with the second direction D2 as its longitudinal direction. The second busbar 621 is connected to a 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, viewed from above in the thickness direction D1 of the piezoelectric layer 4, the second conductor section including the plurality of second electrodes 52 and the second busbar 621 has a comb-shaped form. The second busbar 621 is integrally formed with the plurality of second electrodes 52, but is not limited thereto.

[0077] The first busbar 611 and the second busbar 621 are opposite each other in the third direction D3.

[0078] 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. Furthermore, the first wiring portion 61 and the second wiring portion 62 may also have a structure in which multiple metal films comprising these metals or alloys are stacked. For example, the first wiring portion 61 and the second wiring portion 62 comprise a stacked film comprising a tight-fitting film and a main wiring film formed on the tight-fitting film, wherein the tight-fitting film is composed of a Ti film, and the main wiring film is composed of an Al film or an AlCu film. The thickness of the tight-fitting film is, for example, 10 nm. Furthermore, 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.

[0079] 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 in each of the first busbar 611 and the second busbar 621. Furthermore, the thickness of each of the first wiring portion 61 and the second wiring portion 62 may be greater than the thickness of the first electrode 51 and the second electrode 52.

[0080] (2.6) First segmented resonator, second segmented resonator

[0081] 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 in which the first electrode part 501 is disposed.

[0082] The second segmented resonator RS4 includes a second setting section 402. The second setting section 402 includes a second electrode section 502 among a plurality of electrode sections 50 and a second region 452 in the piezoelectric layer 4 in which the second electrode section 502 is disposed.

[0083] The support substrate 2 has a plurality of holes 26. The plurality of holes 26 includes a first hole 26a and a second hole 26b. Here, the first hole 26a is an example of a "first energy sealing layer," and the second hole 26b is an example of a "second energy sealing layer." The first hole 26a exposes at least a portion of a first region 451 of the piezoelectric layer 4. The second hole 26b exposes at least a portion of a second region 452 of the piezoelectric layer 4. The support substrate 2 has a wall portion 27 located between the first hole 26a and the second hole 26b.

[0084] Viewed from the thickness direction D1, the first cavity 26a partially overlaps with the first electrode 51 and the second electrode 52 of the first electrode portion 501, and with the portion between the first electrode 51 and the second electrode 52 of the first electrode portion 501 in the piezoelectric layer 4. Viewed from the thickness direction D1, the second cavity 26b partially overlaps with the first electrode 51 and the second electrode 52 of the second electrode portion 502, and with 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 cavity 26a overlaps the entire first region 451 when viewed from the thickness direction D1, and the second cavity 26b overlaps the entire second region 452 when viewed from the thickness direction D1. However, the first cavity 26a and the second cavity 26b need only overlap with at least a portion of the first region 451 and at least a portion of the second region 452, respectively. Furthermore, when viewed from the thickness direction D1, the cavity 26 may not overlap with a portion of the first wiring portion 61 and the second wiring portion 62, respectively.

[0085] Furthermore, as long as the first cavity 26a and the second cavity 26b overlap with the first region 451 and the second region 452 respectively when viewed from the thickness direction D1 of the piezoelectric layer 4, at least a portion of the first region 451 and at least a portion of the second region 452 may not be exposed. Specifically, a dielectric film of the first region 451 may exist between the first region 451 and the first cavity 26a, and a dielectric film of the second region 452 may exist between the second region 452 and the second cavity 26b.

[0086] Furthermore, the thickness d1 of the first segmented resonator RS3 and the thickness d2 of the second segmented resonator RS4 are different from each other. Here, the thickness d1 of the first segmented resonator RS3 is the thickness of the first mounting portion 401, which is the thickness of the piezoelectric layer 4 in the first region 451. Alternatively, the thickness of the first mounting portion 401 can be the total thickness, which is 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, 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. Furthermore, in the first region 451, 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, the thickness of the first setting portion 401 may be only the thickness of the insulating layer, or it may be the total thickness, which is 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. The thickness of the second segmented resonator RS4 is the thickness of the second setting portion 402, which here is the thickness of the piezoelectric layer 4 in the second region 452. Alternatively, the thickness of the second setting portion 402 may be the total thickness, which is the sum of the thickness of the second electrode portion 502 included in the second setting portion 402 and the thickness of the piezoelectric layer 4 in the second region 452, or it may be only the thickness of the second electrode portion 502 included in the second setting portion 402, or only the thickness of the piezoelectric layer 4 in the second region 452. Furthermore, in the second region 452, 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, the thickness of the second mounting portion 402 may be only the thickness of the insulating layer, or it may be the total thickness, which is 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. That is, when the thickness d1 of the first segmented resonator RS3 and the thickness d2 of the second segmented resonator RS4 are different from each other, it 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 from each other. It 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 thickness of the constituent elements included in the first mounting portion 401 and the thickness of the constituent elements included in the second mounting portion 402 are different from each other. Therefore, the resonant frequency of the ripple generated from the first segmented resonator RS3 can be different from the resonant frequency of the ripple generated from the second segmented resonator RS4. In other words, the resonant frequency of the useless wave of the first electrode section 501 can be different from the resonant frequency of the useless wave of the second electrode section 502, thereby dispersing the useless wave ripple.

[0087] Furthermore, the polarities of the first segmented resonator RS3 and the second segmented resonator RS4 are different. In Embodiment 1, the polarization direction PZ1 of the piezoelectric layer 4 in the first segmented resonator RS3 and the polarization direction PZ2 of the piezoelectric layer 4 in the second segmented resonator RS4 are different. As a result, linearity can be improved.

[0088] (3) Manufacturing method of elastic wave device

[0089] Regarding the manufacturing method of the elastic wave device 1, for example, after preparing the support substrate 2, steps 1 to 5 are performed. 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, the piezoelectric substrate, which will form the basis of the piezoelectric layer 4, and the support substrate 2 are bonded via the silicon oxide film 7. In the third step, the piezoelectric substrate is thinned to form a piezoelectric layer 4 composed of a portion of the piezoelectric substrate. In the fourth step, a plurality of first electrodes 51, a plurality of second electrodes 52, and 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 described above, the first electrodes 51, the second electrodes 52, and the first wiring portion 61 and the second wiring portion 62 are formed using photolithography, etching, thin film formation, and the like. Furthermore, in the fifth step described above, the predetermined area for forming the voids 26 in the support substrate 2 is etched using photolithography and etching techniques. In the fifth step, the support substrate 2 is etched using a silicon oxide film 7 as an etching barrier layer, and then the useless portions of the silicon oxide film 7 are etched away, thereby exposing a portion of the second main surface 42 of the piezoelectric layer 4. In addition, 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 (small wafers) are obtained by dicing a wafer containing multiple elastic wave devices 1.

[0090] The manufacturing method of the elastic wave device 1 is an 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 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 (Chemical Vapor Deposition) can be listed as an example, but it is not limited to this. In addition, the piezoelectric layer 4 is subjected to a polarization treatment.

[0091] (4) Operation and characteristics of elastic wave devices

[0092] The elastic wave device 1 according to Embodiment 1 is an elastic wave device utilizing a thickness shear first-order mode volume wave. As described above, the thickness shear first-order 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 one node 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. Viewed from the thickness direction D1, the thickness shear vibration is excited in a defined region 45 in the piezoelectric layer 4 between the first electrode 51 and the second electrode 52. The thickness shear vibration can be confirmed, for example, by FEM (Finite Element Method). More specifically, thickness shear vibration can be confirmed, for example, by analyzing the displacement distribution and strain using FEM with parameters of the piezoelectric layer 4 (material, Euler angles, and thickness, etc.) and parameters of the first electrode 51 and the second electrode 52 (material, thickness, distance between the centerlines of the first electrode 51 and the second electrode 52, etc.). The Euler angles of the piezoelectric layer 4 can be determined through analysis.

[0093] Here, refer to Figure 6A as well as Figure 6B The differences between the Lamb wave used in conventional elastic wave devices and the aforementioned first-order thickness shear mode volume wave are explained.

[0094] Figure 6A This is a schematic front sectional view illustrating a Lamb wave propagating in a piezoelectric substrate 460 of an elastic wave device as 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 addition to the piezoelectric substrate 460, the Z-direction and X-direction are also illustrated. 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. If it is a Lamb wave, then the elastic wave is as follows: Figure 6A The plate wave propagates in the X direction as shown. Therefore, in conventional elastic wave devices, the elastic wave propagates in the X direction, and two reflectors are placed on either side of the IDT electrode to obtain the desired resonance characteristics. Consequently, in conventional elastic wave devices, propagation losses of the elastic wave occur, so in the pursuit of miniaturization, i.e., by reducing the number of logarithms of the first and second electrode fingers, the Q value decreases.

[0095] In contrast, in the elastic wave device involved in the reference method, the vibration displacement is in the thickness shear direction, therefore, as Figure 6BAs shown, the elastic wave propagates and resonates approximately in 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 according to the reference scheme, the resonance characteristic can be obtained through the propagation of the wave in this Z-direction, so a reflector is not necessarily required. Therefore, in the elastic wave device according to the reference scheme, there is no propagation loss when the wave propagates towards the reflector. Therefore, in the elastic wave device according to the reference scheme, even if the number of electrode pairs including the first electrode 51 and the second electrode 52 is reduced to promote miniaturization, a decrease in the Q value is not easily generated.

[0096] In the elastic wave device 1 according to Embodiment 1, such as Figure 8 As shown, the amplitude direction of the bulk wave of the first-order mode of thickness shear becomes 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 higher than that of the first electrode 51 is applied between the first electrode 51 and the second electrode 52. The first region 451 is the region within the defined region 45 between the imaginary plane VP1 and the first main surface 41. The imaginary plane VP1 is orthogonal to the thickness direction D1 of the piezoelectric layer 4 and divides the piezoelectric layer 4 into two parts. The second region 452 is the region within the defined region 45 between the imaginary plane VP1 and the second main surface 42.

[0097] For the construction model 1r of the elastic wave device using the reference mode of the first-order mode of the body wave with thickness shearing (reference) Figure 9 The characteristics were simulated. Regarding the construction model 1r, for the same components as the elastic wave device 1 according to Embodiment 1, the same reference numerals are used and the description is omitted.

[0098] The difference between the structural model 1r and the elastic wave device 1 according to Embodiment 1 is that it does not have the first wiring section 61 and the second wiring section 62. In the 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° to cut LiNbO3 and propagate it.

[0099] In structural model 1r, the piezoelectric layer 4 is a film, and the second principal surface 42 of the piezoelectric layer 4 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 centerlines 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. Additionally, when at least one of the first electrode 51 and the second electrode 52 is formed in multiples in the piezoelectric layer 4 (in other words, when the first electrode 51 and the second electrode 52 are considered as a pair of electrode groups, and 1.5 or more pairs of electrode groups are provided in the piezoelectric layer 4), the aforementioned distance between the centerlines p becomes the distance between the centerlines of adjacent first electrodes 51 and second electrodes 52.

[0100] Figure 10A as well as Figure 10B This is a graph showing the relationship between relative bandwidth and d / p when different potentials are provided to the first electrode 51 and the second electrode 52, based on the construction model 1r. Figure 10A as well as Figure 10B In the figure, the horizontal axis represents d / p, and the vertical axis represents the relative bandwidth. Figure 10A as well as Figure 10B This applies to the case where the piezoelectric layer 4 is rotated 120° to cut the X-axis propagating LiNbO3, but the same tendency applies to 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 as well as Figure 10B The same tendency applies. Furthermore, in the construction model 1r of the elastic wave device, regardless of the logarithms of the first electrode 51 and the second electrode 52, the relationship between the relative bandwidth and d / p becomes... Figure 10A as well as Figure 10B The same tendency applies. Furthermore, in the structural model 1r of the elastic wave device, it is not limited to the case where the second principal surface 42 of the piezoelectric layer 4 is in contact with air; even when in contact with the acoustic reflection layer, the relationship between the relative bandwidth and d / p also becomes related to... Figure 10A as well as Figure 10B The same tendency.

[0101] 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, the coupling coefficient remains low and the relative bandwidth is less than 5% regardless of how much d / p is changed within the range of 0.5 < d / p < 1.6. On the other hand, in the structural model 1r of the elastic wave device, when d / p ≤ 0.5, if d / p is changed within the range of 0 < d / p ≤ 0.5, the coupling coefficient can be increased, resulting in a relative bandwidth of over 5%.

[0102] 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 increased, resulting in a larger relative bandwidth. Regarding the elastic wave device 1 according to 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 tends to be the same as the relationship between the relative bandwidth and d / p of the construction model 1r of the elastic wave device.

[0103] Furthermore, according to Figure 10A It is clear 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, resulting in a larger relative bandwidth.

[0104] Figure 10B It is Figure 10A A magnified portion of the curve. (For example...) Figure 10B As shown, the relative bandwidth changes with an inflection point of d / p = 0.096. Therefore, when d / p ≤ 0.096, if d / p is varied within this range, the coupling coefficient can be further increased, resulting in a larger relative bandwidth compared to the case where 0.096 < d / p. Furthermore, as... Figure 10B As shown, the relative bandwidth changes with inflection points of d / p = 0.072 and 0.048. If we set it to 0.048 ≤ d / p ≤ 0.072, we can suppress the change in coupling coefficient caused by the change in d / p and set the relative bandwidth to a roughly constant value.

[0105] Figure 11The following figure illustrates the spurious levels in the band between the resonant and anti-resonant frequencies, showing variations in the piezoelectric layer 4 thickness d, 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, within the structural model 1r of the elastic wave device using the reference method of thickness shearing. 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 a value that normalizes the spurious level by setting the spurious level to 1 at a relative bandwidth (e.g., 22%), which is a relative bandwidth in which the spurious level remains the same 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 is more suitable for exciting the thickness shear mode; however, the same tendency exists for other cut 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 normalized stray level and the relative bandwidth also becomes... Figure 11 The same tendency applies. Furthermore, in the construction model 1r of the elastic wave device, regardless of the logarithms 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 tendency applies. Furthermore, in the structural model 1r of the elastic wave device, it is not limited to the case where the second principal surface 42 of the piezoelectric layer 4 is in contact with air; even when in contact with the acoustic reflection layer, the relationship between the normalized stray level and the relative bandwidth also becomes... Figure 11 The same tendency.

[0106] according to Figure 11 It can be seen that when the relative bandwidth exceeds 17%, the normalized spurious level concentrates at 1. This means that if the relative bandwidth is greater than 17%, it is like... Figure 12 As illustrated by the frequency characteristics of the impedance, there exists a certain secondary resonance in the frequency band between the resonant frequency and the anti-resonant frequency. Figure 12 This is the frequency response of the impedance when using Z-cut LiNbO3 with Euler angles of (0°, 0°, 90°) as piezoelectric layer 4, and setting d / p = 0.08 and MR = 0.35. Figure 12 In the image, the secondary resonant portion is enclosed by a dashed line.

[0107] As described above, if 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, large spurious emissions will still be present in the frequency band between the resonant frequency and the anti-resonant frequency. Such spurious emissions are generated by harmonics in the planar direction, primarily by harmonics in the opposing directions of the first electrode 51 and the second electrode 52. Therefore, from the viewpoint of suppressing spurious emissions within the frequency band, a relative bandwidth of 17% or less is preferable. The elastic wave device 1 according to Embodiment 1 also shows the same tendency as the construction model 1r of the elastic wave device regarding the relationship between the normalized spurious level and the relative bandwidth; therefore, a relative bandwidth of 17% or less is preferred.

[0108] exist Figure 13 In the structural model 1r of the elastic wave device, for the case where LiNbO3 is Z-cut 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 changed, d / p and MR are used as parameters to represent the first distribution region DA1 with a relative bandwidth exceeding 17% and the second distribution region DA2 with a relative bandwidth of less than 17%. 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. Furthermore, in... Figure 13 In the diagram, the approximate straight line DL1 of 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 can be represented by the mathematical formula MR = 1.75 × (d / p) + 0.075. Therefore, in the construction model 1r of the elastic wave device, by satisfying the condition MR ≤ 1.75 × (d / p) + 0.075, it becomes easy to set the relative bandwidth to below 17%. Figure 13 The case where Z-cut LiNbO3 is used as the piezoelectric layer 4, which can more appropriately excite the thickness shear mode, is an example of this, but the same tendency applies to 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 approximate straight line DL1 is also the same. Furthermore, in the structural 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 structural 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. The elastic wave device 1 according to Embodiment 1, by satisfying the condition MR ≤ 1.75 × (d / p) + 0.075 in the same way as the structural model 1r of the elastic wave device, makes it easier to set the relative bandwidth to 17% or less. Additionally, in Figure 13 In the diagram, the approximate line DL2 (hereinafter referred to as the second approximate line DL2), shown as a dashed line other than the approximate line DL1 (hereinafter also referred to as the first approximate line DL1), is the line used to show the boundary for reliably setting the relative bandwidth to 17% or less. The second approximate line DL2 can be represented by the mathematical formula MR = 1.75 × (d / p) + 0.05. Therefore, in the construction model 1r of the elastic wave device according to the reference method and the elastic wave device 1 according to Embodiment 1, by satisfying the condition MR ≤ 1.75 × (d / p) + 0.05, it is possible to reliably set the relative bandwidth to 17% or less.

[0109] (5) Effect

[0110] The elastic wave device 1 according to Embodiment 1 includes a piezoelectric layer 4, a first electrode 51, and a second electrode 52, and utilizes a thickness-sheared first-order mode bulk wave. Furthermore, the elastic wave device 1 includes a first segmented resonator RS3 and a second segmented resonator RS4. Moreover, 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 D1, 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. Furthermore, the support substrate 2 has a wall portion 27 located between the first cavity 26a and the second cavity 26b. Therefore, even with miniaturization, the Q value can be improved, and the strength of the elastic wave device 1 can be maintained.

[0111] The elastic wave device 1 according to 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, 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. Moreover, 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 D1, 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. Furthermore, the support substrate 2 has a wall portion 27 located between the first cavity 26a and the second cavity 26b. Therefore, even with miniaturization, the Q value can be improved, and the strength of the elastic wave device 1 can be maintained.

[0112] In the elastic wave device 1 according to Embodiment 1, the thickness d1 of the first segmented resonator RS3 and the thickness d2 of the second segmented resonator RS4 are different from each other. As a result, ripple can be dispersed.

[0113] In the elastic wave device 1 according to Embodiment 1, the polarities of the first segmented resonator RS3 and the second segmented resonator RS4 are different. As a result, the linearity can be further improved.

[0114] In the elastic wave device 1 according to Embodiment 1, d / p is 0.24 or less. As a result, a larger relative bandwidth can be achieved.

[0115] In the elastic wave device 1 according to 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. At this time, MR ≤ 1.75×(d / p)+0.075 is satisfied. As a result, spurious emissions within the frequency band can be suppressed.

[0116] In the elastic wave device 1 according to Embodiment 1, the potential of the first electrode 51 and the potential of the second electrode 52 are different. This prevents the paired first electrodes 51 and second electrodes 52 from becoming floating potentials.

[0117] (Modification 1 of Implementation Method 1)

[0118] The following is for reference Figure 14 The elastic wave device 1a according to Modification Example 1 will be described. Regarding the elastic wave device 1a according to Modification Example 1, the same reference numerals are used for the same constituent elements as those of the elastic wave device 1 according to Embodiment 1, and the description is omitted.

[0119] The difference between the elastic wave device 1a in Modified Example 1 and the elastic wave device 1 in Embodiment 1 is that each of the plurality of elastic wave resonators 5 also has two reflectors 8.

[0120] Each of the two reflectors 8 is a short-circuit grating. Each reflector 8 is not used to reflect first-order shear mode bulk waves, 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 opposite side of the first electrode 51 at the end of the plurality of first electrodes 51 in the direction of propagation of the unwanted surface acoustic waves within the elastic wave device 1a. The remaining reflector 8 is located on the opposite side of the second electrode 52 at the end of the plurality of second electrodes 52 in the direction of propagation of the unwanted surface acoustic waves within the elastic wave device 1a.

[0121] Each reflector 8 has a plurality of (e.g., 4) 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.

[0122] 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. Furthermore, each reflector 8 may also have a structure in which multiple metal films comprising these metals or alloys are stacked. Each reflector 8, for example, includes a stacked film comprising a close-fitting film formed on the piezoelectric layer 4 and a main electrode film formed on the close-fitting film; the close-fitting film is composed of a Ti film, and the main electrode film is composed of an Al film. The thickness of the close-fitting film is, for example, 10 nm. Furthermore, the thickness of the main electrode film is, for example, 80 nm.

[0123] Furthermore, in the elastic wave device 1a according to Modification 1, each reflector 8 is a short-circuit grating, but it is not limited to this. For example, it may also be an open-circuit grating, a positive and negative reflection type grating, or a grating that combines a short-circuit grating and an open-circuit grating. In addition, in the elastic wave device 1a, each elastic wave resonator 5 has two reflectors 8, but it may also be a structure that has only one of the two reflectors 8.

[0124] (Modification 2 of Implementation Method 1)

[0125] 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 and the polarization direction PZ2 of the piezoelectric layer 4 in the second segmented resonator RS4 are the same. This allows for further improvement in linearity.

[0126] (Modification 3 of Implementation Method 1)

[0127] 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 ripple dispersion without affecting the main resonance.

[0128] (Modification 4 of Implementation Method 1)

[0129] As a variation of implementation method 1, example 4 can also be as follows: Figure 16As 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 are common interstage bus bars 63.

[0130] (Implementation Method 2)

[0131] The following is for reference Figure 17 as well as Figure 18 The elastic wave device 1b according to Embodiment 2 will be described. Regarding the elastic wave device 1b according to Embodiment 2, the same reference numerals are used for the same constituent elements as those in the elastic wave device 1 according to Embodiment 1, and the description is omitted.

[0132] (1) Structure of elastic wave device

[0133] like Figure 17 As shown, the elastic wave device 1b according to Embodiment 2 differs from the elastic wave device 1 according to Embodiment 1 in that it has an acoustic reflection layer 3 between the support substrate 2 and the piezoelectric layer 4.

[0134] In the elastic wave device 1b according to 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.

[0135] 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".

[0136] Furthermore, the support substrate 2 has a wall portion 27 located between the first acoustic reflection layer 3a and the second acoustic reflection layer 3b. This allows for handling of higher frequencies and improved linearity while maintaining the strength of the elastic wave device 1b.

[0137] like Figure 18 As shown, the elastic wave device 1b according to Embodiment 2 is also an elastic wave filter (here, a trapezoidal filter) as the elastic wave device 1 according to 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 The multiple (two) series arm resonators RS1, and the multiple (two) nodes N1, N2 on the first path 12 (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 configured with one on each of the terminals. The grounding terminals 17 and 18 can also be common to a single ground.

[0138] Each of the multiple series-arm resonators RS1 has a first-segment resonator RS3 and a second-segment resonator RS4. The first-segment resonator RS3 and the second-segment resonator RS4 are connected in series. Alternatively, in each of the multiple series-arm resonators RS1, the first-segment resonator RS3 and the second-segment resonator RS4 can also be connected in parallel. Furthermore, each of the multiple parallel-arm resonators RS2 can also have a first-segment resonator and a second-segment resonator. In each of the multiple parallel-arm resonators RS2, the first-segment resonator and the second-segment resonator are connected in series or in parallel.

[0139] 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 each elastic wave resonators 5. Each of the plurality of elastic wave resonators 5 is a resonator comprising at least one pair of electrodes (first electrode 51, second electrode 52). In the elastic wave device 1b, the piezoelectric layer 4 is used in all of the plurality of elastic wave resonators 5. Furthermore, 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.

[0140] (2) Acoustic reflector layer

[0141] like Figure 17 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.

[0142] 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 into the support substrate 2. By including the acoustic reflection layer 3, the elastic wave device 1b can improve the containment 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.

[0143] The acoustic reflective layer 3 has a stacked structure in which at least one (3) low acoustic impedance layers 31 and at least one (2) 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.

[0144] For ease of explanation, in the acoustic reflection layer 3, the two high acoustic impedance layers 32 are sometimes referred to as the first high acoustic impedance layer 321 and the second high acoustic impedance layer 322 in order of their proximity to the second main surface 22 of the support substrate 2. Furthermore, 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 their proximity to the second main surface 22 of the support substrate 2.

[0145] In the acoustic reflection layer 3, starting from the support substrate 2 side, 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. Therefore, the acoustic reflection layer 3 can reflect the bulk wave (thickness shear first-order mode bulk wave) 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.

[0146] The material of the plurality of high acoustic impedance layers 32 is, for example, Pt (platinum). Furthermore, 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. Furthermore, the thickness of each of the plurality of low acoustic impedance layers 31 is, for example, 188 nm. In the acoustic reflection layer 3, two high acoustic impedance layers 32 are each formed of platinum, thus comprising two conductive layers.

[0147] The material of the multiple high acoustic impedance layers 32 is not limited to Pt; for example, it 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; for example, it can also be an insulator.

[0148] 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.

[0149] 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. Moreover, 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 can be appropriately set according to the desired frequency of the elastic wave device 1 and the materials used in each of the high acoustic impedance layers 32 and low acoustic impedance layers 31, so that good reflection can be obtained in the acoustic reflection layer 3.

[0150] (3) Manufacturing method of elastic wave device

[0151] Regarding the manufacturing method of the elastic wave device 1b, for example, after preparing the support substrate 2, steps 1 to 4 are performed. In the first step, an acoustic reflection layer 3 is formed on the first main surface 21 of the support substrate 2. In the second step, the piezoelectric substrate, which will become the basis of the piezoelectric layer 4, and the support substrate 2 are bonded via the acoustic reflection layer 3. In the third step, the piezoelectric substrate is thinned to form a piezoelectric layer 4 composed of a portion of 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 piezoelectric layer 4. In steps 1 to 4, a silicon wafer is used as the support substrate 2. Furthermore, in the second step, 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 (small pieces) are obtained by dicing a wafer containing a plurality of elastic wave devices 1b.

[0152] The manufacturing method of the elastic wave device 1b is an 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 includes 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 can be cited as an example, but it is not limited to this. Furthermore, the piezoelectric layer 4 is subjected to a polarization treatment.

[0153] (4) Effect

[0154] The elastic wave device 1b according to Embodiment 2, like the elastic wave device 1 according to Embodiment 1, utilizes a first-order mode bulk wave sheared by thickness. Therefore, in the elastic wave device 1b according to Embodiment 2, the resonant frequency is not limited by the distance between the center lines of the paired first electrode 51 and second electrode 52, and the resonant frequency can be increased by thinning the piezoelectric layer 4. Thus, high frequencies can be addressed without increasing the planar size of the elastic wave device 1b.

[0155] In the elastic wave device 1b according to Embodiment 2, the second principal surface 42 of the piezoelectric layer 4 in the elastic wave resonator 5 is bound by the acoustic reflection layer 3, thus suppressing unwanted waves. Furthermore, in the elastic wave device 1b according to 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 according to Embodiment 2, the absolute value of the TCF (Temperature Coefficient of Frequency) can be reduced, and the frequency-temperature characteristics can be improved.

[0156] The elastic wave device 1b according to Embodiment 2 includes an acoustic reflection layer 3 disposed between the support substrate 2 and the piezoelectric layer 4.

[0157] (Modification 1 of Implementation Method 2)

[0158] In the elastic wave device 1b according to embodiment 2, the acoustic reflection layer 3 is used in multiple elastic wave resonators 5. However, it is also possible that the high acoustic impedance layer 32 (the second high acoustic impedance layer 322) closest to the piezoelectric layer 4 among the multiple high acoustic impedance layers 32 is separated for each elastic wave resonator 5.

[0159] (Modification 2 of Implementation Method 2)

[0160] The following is for reference Figure 19 The elastic wave device 1c according to Modification 2 of Embodiment 2 will be described. Regarding the elastic wave device 1c according to Modification 2, the same reference numerals are used for the same constituent elements as those in the elastic wave device 1b according to Embodiment 2, and the description is omitted.

[0161] The difference between the elastic wave device 1c in Embodiment 2 and the elastic wave device 1b in Embodiment 2 is that each of the plurality of elastic wave resonators 5 also includes two reflectors 8. The structure of each reflector 8 is the same as that of each reflector 8 in the elastic wave device 1a in Embodiment 1.

[0162] As another variation of Embodiment 2, similar to Variation 4 of Embodiment 1, the second bus 621 of 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 of the pair of bus bars (first bus bar 611 and second bus bar 621) of the second segmented resonator RS4 are common interstage bus bars 63.

[0163] The above-described embodiments 1, 2, etc., are merely one of the various embodiments of the present invention. Various modifications can be made to embodiments 1, 2, etc., based on design and other factors, as long as the objective of the present invention is achieved.

[0164] For example, in the elastic wave device 1 according to Embodiment 1, the piezoelectric layer 4 is bonded to the support substrate 2 via a silicon oxide film 7, but the silicon oxide film 7 is not an essential component.

[0165] Furthermore, in the elastic wave device 1 according to Embodiment 1, the cavity 26 is formed to penetrate the support substrate 2 in the thickness direction of the support substrate 2. However, 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.

[0166] 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 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, like... Figures 20A to 20D Like any of them, it is a shape in which the width at the lower end is wider than the width at the upper end. Therefore, it is possible to achieve this without increasing the width of the first main surface 511 of the first electrode 51 (refer to...). Figure 7 ) and the first main surface 521 of the second electrode 52 (refer to Figure 7 In the case of the width of the electrode, the capacitance between the paired first electrode 51 and second electrode 52 is increased.

[0167] Figure 20A The first electrode 51 and the second electrode 52 shown have portions with a generally constant width at their upper ends and portions with a gradually increasing width at their lower ends. Furthermore, Figure 20B The first electrode 51 and the second electrode 52 shown are trapezoidal in cross-section. Furthermore, Figure 20C The first electrode 51 and the second electrode 52 shown are widened at the ends, and their two sides in the width direction are curved surfaces. Furthermore, Figure 20D The 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.

[0168] In addition, elastic wave devices 1 to 1c can also be used as follows: Figures 21A to 21CAs shown in any of them, a dielectric film 9 is provided, which covers the first main surface 41 of the piezoelectric layer 4 and the first electrode 51 and the second electrode 52 on the first main surface 41. The elastic wave devices 1-1c, by providing the dielectric film 9, are able to increase the capacitance between the paired first electrode 51 and second electrode 52. Figure 21A In this process, the thickness of the dielectric film 9 is thinner than the thicknesses of the first electrode 51 and the second electrode 52, and the surface of the dielectric film 9 has an uneven shape following the shape of the substrate. Figure 21B In this process, the surface of the dielectric film 9 is planarized, becoming planar. Figure 21C 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.

[0169] 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 along the thickness direction D1 and the second direction D2 of the piezoelectric layer 4.

[0170] Furthermore, 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, as long as it has at least one pair of electrodes (first electrode 51 and second electrode 52).

[0171] Furthermore, in the elastic wave devices 1 to 1c, the shapes of the first electrode 51 and the second electrode 52 may be different in each elastic wave resonator 5. Additionally, the shapes of the first electrode 51 and the second electrode 52 may be different in the elastic wave resonator 5 constituting the series arm resonator RS1 and the elastic wave resonator 5 constituting the parallel arm resonator RS2.

[0172] 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.

[0173] (Way)

[0174] The following methods are disclosed in this specification.

[0175] The elastic wave device (1-1c) according to the first embodiment 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 (longitudinal 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) containing the first electrode (51) and the second electrode (52). The elastic wave device (1-1c) also includes a first segmented resonator (RS3) and 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 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 setting part (401). The first setting part (401) includes a first electrode part (501) of a plurality of electrode parts (50) and a first region (451) in which the first electrode part (501) is provided in the piezoelectric layer (4). The second segmented resonator (RS4) includes a second setting part (402). The second setting part (402) includes a second electrode part (502) of a plurality of electrode parts (50) and a second region (452) in which the second electrode part (502) is provided in the piezoelectric layer (4). A piezoelectric layer (4) is disposed directly or indirectly on a support substrate (2). The support substrate (2) has a first energy sealing layer (first cavity 26a; first acoustic reflection layer 3a) and a second energy sealing layer (second cavity 26b; second acoustic reflection layer 3b). 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). The support substrate (2) has a wall portion (27) located between the first energy sealing layer and the second energy sealing layer.

[0176] According to the elastic wave device (1-1c) involved in the first method, even with the promotion of miniaturization, the Q value can be improved and the strength of the elastic wave device (1-1c) can be maintained.

[0177] The elastic wave device (1-1c) according to the second method includes a piezoelectric layer (4), a first electrode (51), and a second electrode (52). The first electrode (51) and the second electrode (52) are 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. In any cross-section along the thickness direction (D1) of the piezoelectric layer (4), 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 this case, 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 a plurality of 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) and 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 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 which the first electrode portion (501) is disposed in the piezoelectric layer (4). 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 which the second electrode portion (502) is disposed within the piezoelectric layer (4). 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 cavity 26a; first acoustic reflection layer 3a) and a second energy sealing layer (second cavity 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 support substrate (2) has a wall portion (27) located between the first energy sealing layer and the second energy sealing layer.

[0178] According to the elastic wave device (1-1c) involved in the second method, even with the promotion of miniaturization, the Q value can be improved and the strength of the elastic wave device (1-1c) can be maintained.

[0179] In the elastic wave device (1-1c) according to the third method, in the first or second method, the thickness (d1) of the first segmented resonator (RS3) is the same as the thickness of the first mounting section (401). The thickness (d2) 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.

[0180] According to the elastic wave device (1-1c) involved in the third method, the ripple can be dispersed.

[0181] In the elastic wave device (1 to 1c) involved in the fourth method, in any of the first to third methods, the polarity of the first segmented resonator (RS3) and the polarity of the second segmented resonator (RS4) are different from each other.

[0182] According to the elastic wave device (1-1c) involved in the fourth method, the linearity can be further improved.

[0183] In the elastic wave device (1b; 1c) according to the fifth method, at least one of the first energy sealing layer and the second energy sealing layer in any of the first to fourth methods 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).

[0184] According to the elastic wave device (1b; 1c) involved in the fifth method, the linearity can be further improved.

[0185] In the elastic wave device (1; 1a) according to the sixth method, at least one of the first energy sealing layer and the second energy sealing layer is void (26) in any of the first to fourth methods.

[0186] In the elastic wave device (1-1c) according to the seventh method, in the second method, the center line distance (p) in the first segmented resonator (RS3) and the center line distance (p) in the second segmented resonator (RS4) are different from each other.

[0187] According to the elastic wave device (1-1c) involved in the seventh method, the ripple can be dispersed without affecting the main resonance.

[0188] In the elastic wave device (1 to 1c) involved in the eighth method, in the second method, d / p is 0.24 or less.

[0189] According to the elastic wave device (1-1c) involved in the eighth method, a larger relative bandwidth can be achieved.

[0190] In the elastic wave device (1-1c) according to the 9th embodiment, in the 8th embodiment, 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 (longitudinal direction D2) opposite to the first electrode (51) and the second electrode (52). 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 (longitudinal direction D2) opposite to the first electrode (51) and the second electrode (52). The piezoelectric layer (4) has a defined region (45). Regarding the specified region (45), viewed from the thickness direction (D1) of the piezoelectric layer (4), in the piezoelectric layer (4), it intersects both the first electrode (51) and the second electrode (52) in the direction opposite to the first electrode (51) and the second electrode (52) in the long dimension direction (D2), and is located between the first electrode (51) and the second electrode (52). Viewed from the thickness direction (D1) of the piezoelectric layer (4), the area of ​​the main part of the first electrode (510) is set as S1, the area of ​​the main part of the second electrode (520) is set as S2, the area of ​​the specified region (45) is set as S0, and the structural parameter specified by (S1+S2) / (S1+S2+S0) is set as MR. At this time, the elastic wave device (1~1c) satisfies the following condition: MR≤1.75×(d / p)+0.075.

[0191] According to the elastic wave device (1-1c) involved in the ninth method, it is possible to suppress spurious signals within the frequency band.

[0192] In the elastic wave device (1 to 1c) according to the 10th method, in any of the 1st to 9th methods, the first electrode (51) and the second electrode (52) are each electrodes that become signal potential or ground potential.

[0193] According to the elastic wave device (1-1c) involved in the 10th method, it is possible to prevent the pair of first electrodes (51) and second electrodes (52) from becoming floating potentials.

[0194] In the elastic wave device (1-1c) according to the 11th embodiment, in any of the 1st to 10th embodiments, when viewed from the thickness direction (D1), the first energy sealing layer (first cavity 26a; first acoustic reflection layer 3a) partially overlaps with the first electrode (51) and the second electrode (52) of the first electrode portion (501), and the first electrode (51) and the second electrode (52) of the first electrode portion (501) in the piezoelectric layer (4). When viewed from the thickness direction (D1), the second energy sealing layer (second cavity 26b; second acoustic reflection layer 3b) partially overlaps with the first electrode (51) and the second electrode (52) of the second electrode portion (502), and the first electrode (51) and the second electrode (52) of the second electrode portion (502) in the piezoelectric layer (4).

[0195] In the elastic wave device (1 to 1c) according to the 12th method, in any of the 1st to 11th methods, 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).

[0196] Explanation of reference numerals in the attached figures

[0197] 1~1c: Elastic wave device;

[0198] 1r: Constructing the model;

[0199] 12: Path 1;

[0200] 13, 14: Path 2;

[0201] 15: Input terminals;

[0202] 16: Output terminals;

[0203] 17, 18: Grounding terminals;

[0204] 2: Support base plate;

[0205] 21: 1st main side;

[0206] 22: The second main surface;

[0207] 26: Hollow;

[0208] 26a: Void 1 (Energy Sealing Layer 1);

[0209] 26b: Second Void (Second Energy Sealing Layer);

[0210] 27: Wall section;

[0211] 3: Sound-reflecting layer;

[0212] 3a: First acoustic reflection layer (first energy sealing layer);

[0213] 3b: Second acoustic reflector layer (second energy sealing layer);

[0214] 31: Low acoustic impedance layer;

[0215] 311: First low acoustic impedance layer;

[0216] 312: Second low acoustic impedance layer;

[0217] 313: Third low acoustic impedance layer;

[0218] 32: High acoustic impedance layer;

[0219] 321: First high acoustic impedance layer;

[0220] 322: Second high acoustic impedance layer;

[0221] 4: Piezoelectric layer;

[0222] 401: First Setting Section;

[0223] 402: Second Setting Section;

[0224] 41: 1st main surface;

[0225] 42: 2nd main surface;

[0226] 45: Designated area;

[0227] 451: Region 1;

[0228] 452: Region 2;

[0229] 5: Elastic wave resonator;

[0230] 50: Electrode section;

[0231] 501: First electrode section;

[0232] 502: Second electrode section;

[0233] 51: First electrode;

[0234] 510: Main part of the first electrode;

[0235] 511: 1st main surface;

[0236] 512: 2nd main surface;

[0237] 52: Second electrode;

[0238] 520: Main part of the second electrode;

[0239] 521: 1st main surface;

[0240] 522: 2nd main surface;

[0241] 61: First wiring section;

[0242] 611: Busbar 1;

[0243] 62: Second wiring section;

[0244] 621: Second busbar;

[0245] 63: Interstage busbar;

[0246] 7: Silicon oxide film;

[0247] 8: Reflector;

[0248] 81: Electrode finger;

[0249] 9: Dielectric film;

[0250] RS1: Series arm resonator;

[0251] RS2: Parallel arm resonator;

[0252] RS3: First segmented resonator;

[0253] RS4: Second Segment Resonator

[0254] d, d1, d2: thickness;

[0255] DA1: Distribution region 1;

[0256] DA2: Second distribution region;

[0257] DL1: Approximate straight line (first approximate straight line);

[0258] DL2: Approximate straight line (second approximate straight line);

[0259] H1: Width of the first electrode;

[0260] H2: Width of the second electrode;

[0261] N1, N2: Nodes;

[0262] p: Distance between centerlines;

[0263] PZ1, PZ2: Polarization directions;

[0264] D1: Thickness direction (first direction);

[0265] D2: Long dimension direction (second direction);

[0266] D3: The 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 intersecting 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, let p be the distance between the centerlines of the first electrode and the second electrode, and d be the thickness of the piezoelectric layer. Then, 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 comprising the first electrode and the second electrode. The elastic wave device also includes: The first and second segmented resonators 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 and output terminals. and 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 setting 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 disposed. 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 disposed. The piezoelectric layer is disposed directly or indirectly on the support substrate. The support substrate has: The first energy sealing layer overlaps with at least a portion of the first region of the piezoelectric layer when viewed from above in the thickness direction of the piezoelectric layer; and The second energy-sealing layer, when viewed from above along the thickness direction of the piezoelectric layer, overlaps with at least a portion of the second region of the piezoelectric layer. The support substrate has a wall portion located between the first energy sealing layer and the second energy sealing layer.

2. The elastic wave device according to claim 1, 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 thicknesses of the first segmented resonator and the second segmented resonator are different from each other.

3. The elastic wave device according to claim 1 or 2, wherein, The polarities of the first segmented resonator and the second segmented resonator are different from each other.

4. The elastic wave device according to claim 1 or 2, wherein, At least one of the first energy sealing layer and the second energy sealing layer is an acoustic reflector layer. The acoustic reflective layer has the following characteristics: High acoustic impedance layer; and The low acoustic impedance layer has a lower acoustic impedance than the high acoustic impedance layer.

5. The elastic wave device according to claim 1 or 2, wherein, At least one of the first energy sealing layer and the second energy sealing layer is void.

6. The elastic wave device according to claim 1, 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.

7. The elastic wave device according to claim 1, wherein, The d / p ratio is below 0.

24.

8. The elastic wave device according to claim 7, wherein, The first electrode has a first electrode main portion, which intersects the second electrode in the direction in which the first electrode and the second electrode face each other. The second electrode has a second electrode main portion, which intersects the first electrode in the direction opposite to the first electrode and the second electrode. The piezoelectric layer has a defined region that, when viewed from the thickness direction of the piezoelectric layer, intersects with and lies between the first and second electrodes in the direction opposite to 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. Let the construction parameter specified by (S1+S2) / (S1+S2+S0) be MR. Then… The elastic wave device satisfies the following conditions. The conditions are: MR≤1.75×(d / p)+0.

075.

9. The elastic wave device according to claim 1 or 2, wherein, The first electrode and the second electrode are each electrodes that serve as signal potentials or ground potentials.

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

11. 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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