Elastic wave device

Abstract

Provided is an elastic wave device capable of improving a Q value and a distortion characteristic even when downsizing is promoted. An elastic wave device (1) includes a piezoelectric layer (4) and a first electrode (51) and a second electrode (52). The first electrode (51) and the second electrode (52) face each other in a direction (D2) intersecting a thickness direction (D1) of the piezoelectric layer (4). The elastic wave device (1) uses a bulk wave of a thickness shear first mode. A material of the piezoelectric layer (4) is lithium niobate or lithium tantalate. The first electrode (51) and the second electrode (52) each include an aluminum layer (511, 521) formed on the piezoelectric layer (4). An orientation direction of a crystal constituting the aluminum layer (511, 521) is a direction orthogonal to a second principal surface (514, 524) of the piezoelectric layer (4) side in the aluminum layer (511, 521).

Description

Technical Field

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

[0002] Previously, elastic wave devices utilizing plate waves propagating in a piezoelectric layer containing LiNbO3 or LiTaO3 were known. For example, Patent Document 1 disclosed an elastic wave device utilizing a Lamb wave as a plate wave. In the elastic wave device described in Patent Document 1, IDT electrodes (first electrode and second electrode) are provided on the upper surface of a piezoelectric substrate (piezoelectric layer) containing LiNbO3 or LiTaO3. Moreover, a Lamb wave can be excited by applying a voltage between a plurality of electrode fingers connected to one potential and a plurality of electrode fingers connected to another potential of the IDT electrodes. Furthermore, reflectors are provided on both sides of the IDT electrodes, and the IDT electrodes and reflectors constitute an elastic wave resonator utilizing a plate wave.

[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 electrode fingers can be reduced. However, if the number of electrode fingers is reduced, the Q value will decrease. In addition, in the elastic wave device described in Patent Document 1, it is difficult to improve the distortion characteristics.

[0008] The object of the present invention is to provide an elastic wave device that can improve the Q value and enhance distortion characteristics even when miniaturization is achieved.

[0009] Methods for solving problems

[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. Each of the first and second electrodes comprises an aluminum layer formed on the piezoelectric layer. The orientation direction of the crystals constituting the aluminum layer is orthogonal to the face of the piezoelectric layer in the aluminum 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 the elastic wave device, in any cross-section along the thickness direction, 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, where d / p is 0.5 or less. The material of the piezoelectric layer is lithium niobate or lithium tantalate. Each of the first electrode and the second electrode comprises an aluminum layer formed on the piezoelectric layer. The orientation direction of the crystals constituting the aluminum layer is orthogonal to the face of the piezoelectric layer side in the aluminum layer.

[0012] Invention Effects

[0013] The elastic wave device according to one aspect of the present invention has the effect that the Q value can be improved even when miniaturization is promoted, and the distortion characteristics can be improved. Attached Figure Description

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

[0015] Figure 2A The elastic wave device mentioned above is Figure 1 A sectional view along line AA. Figure 2B yes Figure 2A A magnified portion of the image.

[0016] Figure 3 This is a top view of the main parts of the same elastic wave device.

[0017] Figure 4A This is an explanatory diagram of Lamb. Figure 4B This is an illustration of the volume wave of the first-order mode of thickness shear.

[0018] Figure 5 This is the same diagram illustrating the operation of the elastic wave device.

[0019] Figure 6 This is an explanatory diagram of the structural model of the elastic wave device involved in the reference method.

[0020] Figure 7A The graph shows 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] for the same construction model as above. Figure 7B The graph shows the relationship between the relative bandwidth of the thickness shear mode and [thickness of the piezoelectric layer] / [distance between the centerlines of the paired electrodes] for the same structural model as above. Figure 7AThe horizontal axis is a magnified curve ranging from 0 to 0.2.

[0021] Figure 8 The graph shows the relationship between the relative bandwidth and the normalized spurious level of the thickness shear mode based on the same construction model.

[0022] Figure 9 It is the impedance-frequency response diagram of the same construction model as above.

[0023] Figure 10 This is a diagram of the distribution of relative bandwidth under the same construction model used to illustrate the combination of [thickness of the piezoelectric layer] / [distance between the centerlines of the first and second electrodes] and construction parameters.

[0024] Figure 11 This is a top view of the elastic wave device involved in a variation of Embodiment 1, Example 1.

[0025] Figure 12 This is the equivalent circuit diagram of the elastic wave device mentioned above.

[0026] Figure 13 This is a top view of the elastic wave device involved in Variation 2 of Embodiment 1.

[0027] Figures 14A-14D This is a cross-sectional view showing the shapes of the first electrode and the second electrode of the elastic wave device according to a variation 3 of Embodiment 1.

[0028] Figures 15A-15C This is a cross-sectional view showing a structural example of an elastic wave device according to a variation 4 of embodiment 1.

[0029] Figure 16 This is a top view of the elastic wave device according to Embodiment 2.

[0030] Figure 17 The elastic wave device mentioned above is Figure 16 A sectional view along line AA.

[0031] Figure 18 This is a top view of the elastic wave device involved in Variation 1 of Embodiment 2. Detailed Implementation

[0032] The following implementation methods, etc., refer to Figures 1-6 , Figure 11 , Figures 13-18 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.

[0033] (Implementation Method 1)

[0034] The following is for reference Figures 1-3 The elastic wave device 1 according to Embodiment 1 will be described.

[0035] (1.1) Overall structure of the elastic wave device

[0036] 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 2A As shown, the first electrode 51 and the second electrode 52 are positioned opposite each other in a direction D2 (hereinafter referred to as "second direction D2") that intersects the thickness direction D1 (hereinafter also referred to as "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 direction PZ1 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 due to the thickness shear vibration of the piezoelectric layer 4, and is a bulk wave in the thickness direction D1 of the piezoelectric layer 4 with a number of nodes equal to 1. The thickness shear vibration is excited by the first electrode 51 and the second electrode 52. In the piezoelectric layer 4, when viewed from the thickness direction D1, the thickness shear vibration is excited in a defined region 45 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 direction PZ1 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 direction PZ1 is, for example, 90°±10°).

[0037] like Figure 1 as well as Figure 2A As shown, the first electrode 51 and the second electrode 52 intersect each other when viewed from the second direction D2. "Intersect each other when viewed from the second direction D2" means that they overlap when viewed from the second direction D2. The elastic wave device 1 also includes a first wiring portion 61 connected to the first electrode 51 and a second wiring portion 62 connected to the second electrode 52. The first wiring portion 61 is connected to a first terminal T1. The second wiring portion 62 is connected to a second terminal T2, which is different from the first terminal T1. The elastic wave device 1 includes a plurality of first electrodes 51 and a plurality of second electrodes 52. That is, when the first electrodes 51 and the second electrodes 52 are set as a pair of electrode groups, the elastic wave device 1 has multiple pairs of electrode groups. In the elastic wave device 1, the plurality of first electrodes 51 and the plurality of second electrodes 52 are arranged alternately, one each in the second direction D2. In the elastic wave device 1, a plurality of first electrodes 51 are connected to a first wiring section 61, and a plurality of second electrodes 52 are connected to a second wiring section 62.

[0038] like Figure 2A As shown, the elastic wave device 1 includes a support substrate 2, an acoustic reflection layer 3, a piezoelectric layer 4, a first electrode 51, and a second electrode 52. The acoustic reflection layer 3 is disposed on the support substrate 2. The piezoelectric layer 4 is disposed on the acoustic reflection layer 3. The first electrode 51 and the second electrode 52 are connected to the piezoelectric layer 4. The acoustic reflection layer 3 has at least one (e.g., two) high acoustic impedance layers 32 and at least one (e.g., three) low acoustic impedance layers 31. The acoustic impedance of the low acoustic impedance layers 31 is lower than that of the high acoustic impedance layers 32. The elastic wave device 1 also includes an elastic wave resonator 5 as a resonator, which comprises the aforementioned first electrode 51, second electrode 52, and piezoelectric layer 4. In the elastic wave device 1, the elastic wave resonator 5 further includes the aforementioned acoustic reflection layer 3.

[0039] (1.2) Components of an elastic wave device

[0040] Next, the constituent elements of the elastic wave device 1 will be described with reference to the accompanying drawings.

[0041] (1.2.1) Support base plate

[0042] like Figure 2A 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 also supports the acoustic reflection layer 3, and supports the piezoelectric layer 4, the first electrode 51, and the second electrode 52 via the acoustic reflection layer 3.

[0043] 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 it is not limited to this, for example, it can also be square.

[0044] The support substrate 2 is, for example, a silicon substrate. The thickness of the support substrate 2 is, for example, 120 μm, but is not limited thereto. The silicon substrate is a single-crystal silicon substrate. When the support substrate 2 is a 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 described above can be set without being limited by the orientation of the silicon substrate. The resistivity of the silicon substrate is, for example, 1 kΩcm or more, preferably 2 kΩcm or more, and more preferably 4 kΩcm or more.

[0045] 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.

[0046] (1.2.2) Acoustic reflector layer

[0047] like Figure 2A As shown, the acoustic reflection layer 3 is disposed on the first main surface 21 of the support substrate 2. The acoustic reflection layer 3 is opposite to the first electrode 51 and the second electrode 52 in the thickness direction D1 of the piezoelectric layer 4.

[0048] 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 first electrode 51 and the second electrode 52 into the support substrate 2. By including the acoustic reflection layer 3, the elastic wave device 1 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 1 can reduce losses and improve the Q value.

[0049] The acoustic reflector layer 3 has a stacked structure in which multiple (3) low acoustic impedance layers 31 and multiple (2) high acoustic impedance layers 32 are alternately arranged 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.

[0050] 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 proximity to the first main surface 21 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 proximity to the first main surface 21 of the support substrate 2.

[0051] 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 each of 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.

[0052] 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, since the two high acoustic impedance layers 32 are each formed of platinum, two conductive layers are included.

[0053] The material of the multiple high acoustic impedance layers 32 is not limited to Pt, but can also be metals such as W (tungsten) and Ta (tantalum). Furthermore, the material of the multiple high acoustic impedance layers 32 is not limited to metals, but can also be insulators, for example.

[0054] 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.

[0055] Furthermore, the number of low acoustic impedance layers 31 in the acoustic reflection layer 3 is not limited to three; it can be one, two, or more than four. Similarly, the number of high acoustic impedance layers 32 in the acoustic reflection layer 3 is not limited to two; it can be one, or more than three. Moreover, the number of high acoustic impedance layers 32 and the number of low acoustic impedance layers 31 are not limited to being different; they can be the same, and the number of low acoustic impedance layers 31 can be one less than the number of high acoustic impedance layers 32.

[0056] Furthermore, the film thickness of the high acoustic impedance layer 32 and the low acoustic impedance layer 31 in the acoustic reflection layer 3 can be appropriately set according to the desired frequency of the elastic wave device 1 and the materials used for the high acoustic impedance layer 32 and the low acoustic impedance layer 31, so that good reflection is obtained in the acoustic reflection layer 3.

[0057] (1.2.3) Piezoelectric layer

[0058] like Figure 2A As 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. 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 acoustic reflection layer 3. Therefore, in the elastic wave device 1, the distance between the first main surface 41 of the piezoelectric layer 4 and the acoustic reflection layer 3 is longer than the distance between the second main surface 42 of the piezoelectric layer 4 and the acoustic reflection layer 3. 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) The angle is 0°±10°, and θ is 0°±10°. ψ is an arbitrary angle. From the viewpoint of improving the coupling coefficient, the piezoelectric layer 4 is preferably Z-cut LiNbO3 or Z-cut LiTaO3. The 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 is not limited to this; for example, it can also be a twin crystal, or it can be ceramic.

[0059] The thickness of the piezoelectric layer 4 is, for example, 50 nm or more and 1000 nm or less, and for example, 400 nm.

[0060] The piezoelectric layer 4 has a defined region 45. The defined region 45 is a 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 opposite to the first electrode 51 and the second electrode 52, and is located between the first electrode 51 and the second electrode 52.

[0061] (1.2.4) Electrode

[0062] In the elastic wave device 1, of the first electrode 51 and the second electrode 52, the first electrode 51 is a signal (HOT) electrode, and the second electrode 52 is a ground electrode. In the elastic wave device 1, multiple first electrodes 51 and multiple second electrodes 52 are arranged alternately, one at a time. Therefore, adjacent first electrodes 51 and second electrodes 52 are separated. The distance between the center lines of adjacent first electrodes 51 and second electrodes 52 is, for example, more than 1 μm and less than 10 μm, and as an example, 3 μm. Here, "adjacent" means that the first electrodes 51 and second electrodes 52 are positioned opposite each other with a gap between them.

[0063] Regarding a group of electrodes comprising multiple first electrodes 51 and multiple second electrodes 52, any structure in which the multiple first electrodes 51 and multiple second electrodes 52 are arranged separately in the second direction D2 is acceptable, or a structure in which the multiple first electrodes 51 and multiple second electrodes 52 are arranged separately without alternation. For example, a region may exist where one first electrode 51 and one second electrode 52 are arranged separately, and a region may exist where two of the first electrodes 51 or the second electrodes 52 are arranged in the second direction D2. Furthermore, for example, one or more of the multiple first electrodes 51 or the second electrodes 52 may be set to an electrically floating state.

[0064] Viewed from above along the thickness direction D1 of the piezoelectric layer 4, as shown... Figure 1As 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, 50 nm or more and 1000 nm or less; as an example, it is 500 nm. 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, 50 nm or more and 1000 nm or less; as an example, it is 500 nm.

[0065] The first electrode 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, the second electrode 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.

[0066] like Figure 2A As shown, each of the plurality of first electrodes 51 comprises a stacked film of a main electrode film 511 and a close-fitting film 512. Figure 2A As shown, each of the plurality of second electrodes 52 comprises a stacked film of a main electrode film 521 and a bonding film 522. The main electrode films 511 and 521 are formed on the bonding films 512 and 522. That is, the main electrode films 511 and 521 are formed on the piezoelectric layer 4 with the bonding films 512 and 522 in between. The main electrode films 511 and 521 are, for example, composed of an Al film or an AlCu film. The bonding films 512 and 522 are, for example, composed of a Ti film. The thickness of the main electrode films 511 and 521 is, for example, 80 nm. The thickness of the bonding films 512 and 522 is, for example, 10 nm. When the main electrode films 511 and 521 are AlCu films, the Cu content is preferably 1 to 20 wt%. Furthermore, the main electrode films 511 and 521 are not limited to Al films or AlCu films; for example, they may also be composed of an alloy with Al (aluminum) as the main component and containing Mn (manganese) or Si (silicon). In the elastic wave device 1 according to Embodiment 1, the main electrode films 511 and 521 are aluminum layers.

[0067] In the elastic wave device 1 according to Embodiment 1, such as Figure 2BAs shown, the crystals constituting the main electrode film 511, which is an aluminum layer, are... <111> The direction is orthogonal to the surface of the piezoelectric layer 4 in the main electrode film 511 (here, the surface of the close-fitting film 512 in the main electrode film 511). In other words, the direction is orthogonal to the crystals constituting the main electrode film 511 as an aluminum layer. <111> The direction is orthogonal to the principal plane (here, the first principal plane 41) of the piezoelectric layer 4. Furthermore, the C-axis 101 of the piezoelectric layer 4 is the Z-axis direction within the crystal axes (X, Y, Z) defined by the crystal structure of the piezoelectric layer 4. Here, "orthogonal" is not limited to strictly orthogonal; it can also be approximately orthogonal (the angle between the first principal plane 41 of the piezoelectric layer 4 and the C-axis 101 is, for example, 90° ± 10°). Additionally, the crystal constituting the main electrode film 511 as an aluminum layer... <111> The orientation is the orientation of the crystals that constitute the main electrode film 511.

[0068] In the elastic wave device 1 according to Embodiment 1, such as Figure 2B As shown, the orientation axis 102 of the main electrode film (aluminum layer) 521, which constitutes part of the second electrode 52, the orientation axis 103 of the close-fitting film 522, which constitutes part of the second electrode 52, and the C-axis 101 of the piezoelectric layer 4 are all oriented in the same direction. In other words, the crystals constituting the main electrode film 521, which is the aluminum layer, are aligned in the same direction. <111> The orientation (orientation axis 102) is orthogonal to the surface of the piezoelectric layer 4 in the main electrode film 521 (here, the surface of the close-fitting film 522 in the main electrode film 521). In other words, the crystals constituting the main electrode film 521 as an aluminum layer... <111> The direction is orthogonal to the main surface (here, the first main surface 41) of the piezoelectric layer 4.

[0069] In the elastic wave device 1 according to Embodiment 1, the main electrode films 511 and 521, which are aluminum layers, are epitaxial layers. Here, "epitaxy layer" refers to a metal layer grown with the same orientation as the single crystal of the substrate. In Embodiment 1, the orientation of the main electrode films 511 and 521, which are epitaxial layers, is the same as the orientation of the piezoelectric layer 4.

[0070] Here, we envision a case where the orientation axis 102 of the main electrode films 511, 521 is tilted relative to the first principal surface 41 of the piezoelectric layer 4. In this case, if the elastic wave resonator 5 is excited, distortion (intermodulation distortion, IMD) occurs between the input and output signals due to the tilt of the orientation axis 102 of the main electrode films 511, 521. In contrast, in the elastic wave device 1 according to Embodiment 1, the orientation axis 102 of the main electrode films 511, 521 is orthogonal to the first principal surface 41 of the piezoelectric layer 4, thus suppressing distortion between the input and output signals. In other words, the distortion characteristics can be improved according to the elastic wave device 1 according to Embodiment 1.

[0071] In the elastic wave device 1 according to Embodiment 1, the width H1 of the first electrode is the same among the plurality of first electrodes 51, 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 second electrode is the same among the plurality of second electrodes 52, 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.

[0072] Regarding the elastic wave device 1 involved in Embodiment 1, in Figure 1 In this process, there are 5 of each of the first electrode 51 and the second electrode 52. However, the number of the first electrode 51 and the second electrode 52 is not limited to 5. It can also be one, two to four, six or more, or even more than 50.

[0073] The second direction D2 of the first electrode 51 and the second electrode 52 facing each other is preferably the polarization direction PZ1 of the piezoelectric layer 4 (refer to...). Figure 2A The directions are orthogonal, but not limited to this. 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 opposite each other in a direction orthogonal to the third direction D3, which is the length 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 length direction, may be 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.

[0074] In elastic wave device 1, such as Figure 2A As shown, a plurality of first electrodes 51 are each disposed on the first main surface 41 of the piezoelectric layer 4. Furthermore, in the elastic wave device 1, a plurality of second electrodes 52 are each disposed on the first main surface 41 of the piezoelectric layer 4. That is, in the elastic wave device 1, the first electrodes 51 and the second electrodes 52 are disposed on the same main surface (here, the first main surface 41) of the piezoelectric layer 4 and are opposite each other on the same main surface.

[0075] In the elastic wave device 1 according to Embodiment 1, the thickness of each of the plurality of first electrodes 51 is thinner than the thickness of the piezoelectric layer 4. Each of the plurality of first electrodes 51 includes a first main surface 513 and a second main surface 514 intersecting the thickness direction D1 of the piezoelectric layer 4, and two side surfaces 515, 515 intersecting the width direction of the first electrode 51. In each of the plurality of first electrodes 51, of the first main surface 513 and the second main surface 514, the second main surface 514 is located on the side of the acoustic reflection layer 3. Therefore, in the elastic wave device 1, the shortest distance between the first main surface 513 of the first electrode 51 and the acoustic reflection layer 3 is longer than the shortest distance between the second main surface 514 of the first electrode 51 and the acoustic reflection layer 3. In each of the plurality of first electrodes 51, the second main surface 514 is in planar contact with the piezoelectric layer 4.

[0076] In the elastic wave device 1 according to Embodiment 1, the thickness of each of the plurality of second electrodes 52 is thinner than the thickness of the piezoelectric layer 4. Each of the plurality of second electrodes 52 includes a first main surface 523 and a second main surface 524 intersecting the thickness direction D1 of the piezoelectric layer 4, and two side surfaces 525, 525 intersecting the width direction of the second electrode 52. In each of the plurality of second electrodes 52, of the first main surface 523 and the second main surface 524, the second main surface 524 is located on the acoustic reflection layer 3 side. Therefore, in the elastic wave device 1, the shortest distance between the first main surface 523 of the second electrode 52 and the acoustic reflection layer 3 is longer than the shortest distance between the second main surface 524 of the second electrode 52 and the acoustic reflection layer 3. In each of the plurality of second electrodes 52, the second main surface 524 is in planar contact with the piezoelectric layer 4.

[0077] (1.2.5) First wiring section and second wiring section

[0078] The first wiring section 61 includes a first busbar 611. The first busbar 611 is a conductor section used to bring the plurality of first electrodes 51 to the same potential. The first busbar 611 is a long strip (straight line) with the second direction D2 as its length direction. The plurality of first electrodes 51 connected to the first busbar 611 extend toward the second busbar 621. In the elastic wave device 1, when 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.

[0079] The second wiring section 62 includes a second busbar 621. The second busbar 621 is a conductor section used to bring the plurality of second electrodes 52 to the same potential. The second busbar 621 is a long strip (straight line) with the second direction D2 as its length direction. The plurality of second electrodes 52 connected to the second busbar 621 extend toward the first busbar 611. In the elastic wave device 1, when 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 formed integrally with the plurality of second electrodes 52, but is not limited thereto.

[0080] The first busbar 611 and the second busbar 621 are opposite each other in the third direction D3. The third direction D3 is orthogonal to both the first direction D1 and the second direction D2.

[0081] 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 (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, 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 containing a tight-fitting film and a main wiring film, wherein the tight-fitting film is composed of a Ti film, and the main wiring film is formed on the tight-fitting film and 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, Cu is preferably 1 to 20 wt%.

[0082] 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.

[0083] (1.3) Manufacturing method of elastic wave device

[0084] In the manufacturing method of the elastic wave device 1, 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 forms 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 first electrode 51, a second electrode 52, a first wiring portion 61, and a second wiring portion 62 are formed on the piezoelectric layer 4. In the fourth step, the first electrode 51, the second electrode 52, the first wiring portion 61, and the second wiring portion 62 are formed using photolithography, etching, thin film formation, or the like. Furthermore, in steps 1 to 4, a silicon wafer is used as the support substrate 2, and a piezoelectric wafer is used as the piezoelectric substrate. In the manufacturing method of elastic wave device 1, multiple elastic wave devices 1 (chips) are obtained by cutting a wafer containing multiple elastic wave devices 1.

[0085] 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 cited as an example, but it is not limited to this.

[0086] (1.4) Operation and characteristics of elastic wave devices

[0087] The elastic wave device 1 according to Embodiment 1 is an elastic wave device utilizing a first-order thickness shear mode volume wave. As described above, the first-order thickness shear mode volume wave is a volume wave propagating in the thickness direction D1 of the piezoelectric layer 4 due to the 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. In the piezoelectric layer 4, when viewed from the thickness direction D1, the thickness shear vibration is excited in a defined region 45 between the first electrode 51 and the second electrode 52. For example, the thickness shear vibration can be confirmed by FEM (Finite Element Method). More specifically, for example, by using 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 displacement distribution can be analyzed using FEM, and the distortion can be analyzed, thereby confirming thickness shear vibration. The Euler angles of the piezoelectric layer 4 can be determined through analysis. For example, Femtet (registered trademark) from Murata Manufacturing Co., Ltd. can be used as analytical simulation software in FEM.

[0088] Here, refer to Figure 4A as well as Figure 4B The differences between the Lamb wave used in conventional elastic wave devices and the aforementioned first-order thickness shear mode volume wave are explained.

[0089] Figure 4A This is a schematic front sectional view illustrating the Lamb wave propagating in a piezoelectric substrate of an elastic wave device such as the surface acoustic wave device described in Patent Document 1. In conventional elastic wave devices, the elastic wave propagates in the piezoelectric substrate 400 as indicated by the arrow. Here, the piezoelectric substrate 400 has a first main surface 401 and a second main surface 402 facing each other. Figure 4A In addition to the piezoelectric substrate 400, the Z-direction and X-direction are also illustrated. Figure 4A In the diagram, the Z-direction is the thickness direction connecting the first main surface 401 and the second main surface 402 of the piezoelectric substrate 400. The X-direction is the orientation of the multiple electrode fingers of the IDT electrode. If it is a Lamb wave, then the elastic wave is as follows: Figure 4A As shown, a plate wave propagates continuously in the X direction. Therefore, in conventional elastic wave devices, since the elastic wave propagates in the X direction, two reflectors are placed on each side of the IDT electrode to obtain the desired resonance characteristics. As a result, propagation losses of the elastic wave occur in conventional elastic wave devices, so the Q value decreases when miniaturization is sought, i.e., when the number of electrode finger pairs is reduced.

[0090] In contrast, such as Figure 4BAs shown, in the elastic wave device 1 according to Embodiment 1, the vibration displacement is in the thickness shear direction. Therefore, the elastic wave propagates approximately in the Z direction, which is the direction connecting the first principal surface 41 and the second principal surface 42 of the piezoelectric layer 4, and resonates. That is, the X-direction component of the elastic wave is significantly smaller than the Z-direction component. Moreover, since the resonant characteristics can be obtained through the propagation of the elastic wave in this Z-direction, a reflector is not necessarily required. Therefore, there is no propagation loss of the elastic wave when propagating in a reflector. Therefore, even if the number of electrode pairs formed by the first electrode 51 and the second electrode 52 is reduced in order to promote miniaturization, it is not easy to cause a decrease in the Q value.

[0091] In the elastic wave device 1 according to Embodiment 1, such as Figure 5 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 5 The diagram schematically illustrates a bulk wave when a voltage is applied between the first electrode 51 and the second electrode 52, with the second electrode 52 having a higher potential than the first electrode 51. The first region 451 is the region within the defined region 45 between the imaginary plane VP1 and the first main surface 41, which 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.

[0092] 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 6 The characteristics were simulated. Regarding the construction model 1r, the same reference numerals are used for the same components as those in the elastic wave device 1 according to embodiment 1, and the descriptions are omitted.

[0093] The difference between the structural model 1r and the elastic wave device 1 according to Embodiment 1 is that it does not have a first wiring section 61 and a 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.

[0094] 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 6In the model 1r, the distance between the centerlines of adjacent first electrodes 51 and second electrodes 52 is defined as p, and the thickness of the piezoelectric layer 4 is defined 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 defined as S1, the area of ​​the main portion 520 of the second electrode is defined as S2, the area of ​​the defined region 45 is defined as S0, and the structural parameter defined by (S1+S2) / (S1+S2+S0) is defined as MR. Additionally, when at least one of the first electrodes 51 and the second electrode 52 is formed in multiple piezoelectric layers 4, the aforementioned distance between the centerlines p becomes the distance between the centerlines of adjacent first electrodes 51 and second electrodes 52, respectively.

[0095] Figure 7A as well as Figure 7B 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 7A as well as Figure 7B In the figure, the horizontal axis represents d / p, and the vertical axis represents the relative bandwidth. Figure 7A as well as Figure 7B This refers to the case where the piezoelectric layer 4 is rotated 120° to cut the X-axis propagating LiNbO3, but the same trend 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 7A as well as Figure 7B 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 7A as well as Figure 7B 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 3, the relationship between the relative bandwidth and d / p becomes similar to... Figure 7A as well as Figure 7B The same tendency.

[0096] Depend on Figure 7A It can be seen that in the structural model 1r of the elastic wave device, the relative bandwidth value changes drastically with an inflection point of d / p = 0.5. In the structural model 1r of the elastic wave device, when d / p > 0.5, regardless of how much d / p is changed within the range of 0.5 < d / p < 1.6, the coupling coefficient is low and the relative bandwidth is less than 5%. On the other hand, in the structural model 1r of the elastic wave device, when d / p ≤ 0.5, if d / p is changed within the range of 0 < d / p ≤ 0.5, the coupling coefficient can be increased and the relative bandwidth can be set to more than 5%.

[0097] Furthermore, in the construction model 1r of the elastic wave device, when d / p ≤ 0.24, if d / p is varied within the range of 0 < d / p ≤ 0.24, the coupling coefficient can be further improved and the relative bandwidth can be increased. Regarding the elastic wave device 1 according to Embodiment 1, as... Figure 2A As shown, in any cross section along the thickness direction D1 of the piezoelectric layer 4, if 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, 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.

[0098] Furthermore, by Figure 7A 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 and the relative bandwidth can be made larger.

[0099] Figure 7B It is Figure 7A A magnified portion of the curve. (For example...) Figure 7B 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 the range of 0 < d / p ≤ 0.096, the coupling coefficient can be further improved and the relative bandwidth increased compared to the case where 0.096 < d / p. Furthermore, as... Figure 7B 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.

[0100] Figure 8 This diagram was created by plotting the spurious levels in the frequency band between the resonant and anti-resonant frequencies in a construction model 1r of an elastic wave device utilizing a thickness shear mode, where 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 were varied. Figure 8 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 obtained by normalizing the spurious level by setting the spurious level at a relative bandwidth (e.g., 22%) where the spurious level remains the same even when the thickness d of the piezoelectric layer 4, the distance p between the center lines of the first electrode 51 and the second electrode 52, the width H1 of the first electrode, and the width H2 of the second electrode are changed. Figure 8This is the case where Z-cut LiNbO3 is used as the piezoelectric layer 4, which can more appropriately excite the thickness shear mode; however, the same trend applies to 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 8 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 8 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 in the case where it is in contact with the acoustic reflection layer, the relationship between the normalized stray level and the relative bandwidth becomes... Figure 8 The same tendency.

[0101] Depend on Figure 8 It can be seen that when the relative bandwidth exceeds 17%, the normalized spurious level is concentrated at 1. This means that if the relative bandwidth is above 17%, it is like... Figure 9 As illustrated by the frequency characteristics of the impedance, there are certain secondary resonances in the frequency band between the resonant frequency and the anti-resonant frequency. Figure 9 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 9 In the image, the secondary resonant portion is enclosed by a dashed line.

[0102] 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 emission level and the relative bandwidth; therefore, a relative bandwidth of 17% or less is preferable.

[0103] exist Figure 10In 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 10 In the distribution region DA1 and the distribution region DA2, the point densities are made different, with the point density in distribution region DA1 being higher than that in distribution region DA2. Furthermore, in... Figure 10 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, the relative bandwidth can be set to below 17%.

[0104] Figure 10 In the case where Z-cut LiNbO3 is used as the piezoelectric layer 4 to more appropriately excite the thickness shearing mode, 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 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, like the structural model 1r of the elastic wave device, can achieve a relative bandwidth of 17% or less by satisfying the condition MR ≤ 1.75 × (d / p) + 0.075. Additionally, in Figure 10 In the model 1r of the elastic wave device, besides the approximate line DL1 (hereinafter also referred to as the first approximate line DL1), the approximate line DL2 (hereinafter also referred to as the second approximate line DL2), shown by a single-dotted line, is the line used to reliably set 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, by satisfying the condition MR ≤ 1.75 × (d / p) + 0.05, it is possible to reliably set the relative bandwidth to 17% or less.

[0105] (1.5) Effect

[0106] The elastic wave device 1 according to Embodiment 1 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 D2 intersecting the thickness direction D1 of the piezoelectric layer 4. The elastic wave device 1 utilizes thickness shearing of a first-order mode bulk wave. The material of the piezoelectric layer 4 is lithium niobate or lithium tantalate. The first electrode 51 and the second electrode 52 each include aluminum layers (main electrode films) 511 and 521 formed on the piezoelectric layer 4. The crystals constituting the aluminum layers 511 and 521... <111> The direction is orthogonal to the face of the piezoelectric layer 4 in aluminum layers 511 and 521.

[0107] In the elastic wave device 1 according to Embodiment 1, the Q value can be improved even with miniaturization, and the distortion characteristics can be enhanced. Here, in the elastic wave device 1 according to Embodiment 1, resonance characteristics can be obtained by propagating a first-order mode of a thickness sheared bulk wave through wave propagation in the Z direction, thus a reflector is not necessarily required. Therefore, propagation loss during reflector propagation does not occur. Therefore, even if the number of electrode pairs formed by the first electrode 51 and the second electrode 52 is reduced to further miniaturize the planar dimensions, a decrease in the Q value is not easily observed. Furthermore, in the elastic wave device 1 according to Embodiment 1, the crystals constituting the aluminum layers (main electrode films) 511 and 521... <111> The orientation is orthogonal to the planes of the piezoelectric layer 4 in the aluminum layers 511 and 521, thus improving the distortion characteristics when the elastic wave resonator 5 is excited.

[0108] Furthermore, the elastic wave device 1 according to Embodiment 1 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 D2 intersecting the thickness direction D1 of the piezoelectric layer 4. In the elastic wave device 1, 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 defined as p, and the thickness of the piezoelectric layer 4 is defined as d, where d / p is 0.5 or less. The material of the piezoelectric layer 4 is lithium niobate or lithium tantalate. The first electrode 51 and the second electrode 52 each include aluminum layers (main electrode films) 511 and 521 formed on the piezoelectric layer 4. The crystals constituting the aluminum layers 511 and 521... <111> The direction is orthogonal to the face of the piezoelectric layer 4 in aluminum layers 511 and 521.

[0109] In the elastic wave device 1 according to Embodiment 1, the Q value can be improved even when miniaturization is promoted, and the distortion characteristics can be improved.

[0110] Furthermore, in the elastic wave device 1 according to Embodiment 1, the second main surface 42 of the piezoelectric layer 4 can suppress unwanted waves through the acoustic reflection layer 3. In addition, in the elastic wave device 1 according to Embodiment 1, the material of the piezoelectric layer 4 is lithium niobate or lithium tantalate, and the material of the low acoustic impedance layer 31 is silicon oxide. Here, lithium niobate and lithium tantalate each have negative frequency-temperature characteristics, while silicon oxide has a positive frequency-temperature characteristic. Therefore, in the elastic wave device 1 according to Embodiment 1, the absolute value of TCF (Temperature Coefficient of Frequency) can be reduced, and the frequency-temperature characteristics can be improved.

[0111] (1.6) Variation Example

[0112] The above-described embodiment 1 is merely one of the various embodiments of the present invention. As long as the purpose of the present invention can be achieved, the above-described embodiment 1 can be modified in various ways according to design, etc.

[0113] (1.6.1) Variation Example 1

[0114] The following is for reference Figure 11 as well as Figure 12 The elastic wave device 1a according to Modification Example 1 will be described. In addition, for 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.

[0115] The elastic wave device 1a involved in Variation 1 is an elastic wave filter (here, a trapezoidal filter). The elastic wave device 1a 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, one 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 grounding (grounding terminals 17, 18). Grounding terminals 17 and 18 can also be common to a single ground.

[0116] In the elastic wave device 1a, multiple series-arm resonators RS1 and multiple parallel-arm resonators RS2 are each elastic wave resonators 5. Each of the multiple elastic wave resonators 5 includes a first electrode 51 and a second electrode 52. In the elastic wave device 1a, the piezoelectric layer 4 is shared in the multiple elastic wave resonators 5. Furthermore, in the elastic wave device 1a, the acoustic reflection layer 3 is shared in the multiple 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.

[0117] In the elastic wave device 1a, the support substrate 2 and the acoustic reflection layer 3 are shared in multiple elastic wave resonators 5, but the high acoustic impedance layer 32 closest to the piezoelectric layer 4 (the second high acoustic impedance layer 322) among the multiple high acoustic impedance layers 32 can also be separated for each elastic wave resonator 5.

[0118] (1.6.2) Variation Example 2

[0119] The following is for reference Figure 13 The elastic wave device 1b according to Modification Example 2 will be described. In addition, for the elastic wave device 1b according to Modification Example 2, 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.

[0120] The elastic wave device 1b in Modified Example 2 differs from the elastic wave device 1 in Embodiment 1 in that it also includes two reflectors 8.

[0121] 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 1b. 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 1b.

[0122] 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.

[0123] Each reflector 8 is conductive. The material of each reflector 8 is, for example, Al, Cu, Pt, Au, Ag, Ti, Ni, Cr, Mo, W, or an alloy primarily composed of any of these metals. 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, comprises a stacked film containing a bonding film and a main electrode film. The bonding film is formed on the piezoelectric layer 4 and is composed of a Ti film, while the main electrode film is formed on the bonding film and is composed of an Al film. The thickness of the bonding film is, for example, 10 nm. Furthermore, the thickness of the main electrode film is, for example, 80 nm.

[0124] Furthermore, in the elastic wave device 1b according to Modification 2, each reflector 8 is a short-circuit grating, but it is not limited to this. For example, it can 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, the elastic wave device 1b has two reflectors 8, but it can also have a structure that has only one of the two reflectors 8.

[0125] (1.6.3) Variation Example 3

[0126] In the elastic wave device 1 according to Embodiment 1, the cross-sectional shape of the first electrode 51 and the second electrode 52 is rectangular, but it is not limited to this. For example, the first electrode 51 and the second electrode 52 may also be as follows: Figures 14A to 14D As shown in either of them, the shape is such that the width at the lower end is wider than the width at the upper end. Therefore, the capacitance between the first electrode 51 and the second electrode 52 can be increased without increasing the width of the upper surfaces of the first electrode 51 and the second electrode 52.

[0127] exist Figure 14A In the middle, the first electrode 51 and the second electrode 52 have a portion with a generally constant width on the upper end side, and a portion with a gradually increasing width on the lower end side. Furthermore, in... Figure 14B In this configuration, the first electrode 51 and the second electrode 52 have a trapezoidal cross-section. Furthermore, in... Figure 14C In this design, the first electrode 51 and the second electrode 52 have a shape that widens at the ends, and their two sides in the width direction are curved surfaces. Furthermore, in... Figure 14D In the middle, the first electrode 51 and the second electrode 52 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.

[0128] (1.6.4) Variation Example 4

[0129] In the elastic wave device 1 according to Embodiment 1, 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 are exposed, but it is not limited thereto. The elastic wave device 1 can also be, for example, as shown in the figure. Figures 15A-15C Each of the following has a dielectric film 9 covering 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, as shown.

[0130] exist Figure 15A 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 15B In this process, the surface of the dielectric film 9 is planarized, becoming planar. Figure 15C 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.

[0131] (1.6.5) Other variations

[0132] In Embodiment 1, the first electrode 51 and the second electrode 52 are disposed on the first main surface 41 of the piezoelectric layer 4, but this is not a limitation. The first electrode 51 and the second electrode 52 may also be disposed on the second main surface 42 of the piezoelectric layer 4. That is, the first electrode 51 and the second electrode 52 may also be disposed on the main surface (here, the second main surface 42) of the piezoelectric layer 4 and face each other on the main surface.

[0133] In embodiment 1, the first electrode 51 and the second electrode 52 are disposed on the first main surface 41 of the piezoelectric layer 4, but this is not a limitation. At least a portion of each of the first electrode 51 and the second electrode 52 may also be embedded in the piezoelectric layer 4.

[0134] In Embodiment 1, the cross-sectional shape of the first electrode 51 is the same as that of the second electrode 52, but the cross-sectional shapes of the first electrode 51 and the second electrode 52 may also be different. Here, the cross-sectional shape is, for example, the shape of the cross-section along the thickness direction D1 and the second direction D2 of the piezoelectric layer 4.

[0135] In the case where the elastic wave filter is configured as in the elastic wave device 1a of the modified embodiment 1, the shapes of the first electrode 51 and the second electrode 52 may differ for each elastic wave resonator 5. Furthermore, the shapes of the first electrode 51 and the second electrode 52 may differ in the elastic wave resonator 5 that constitutes the series arm resonator RS1 and the elastic wave resonator 5 that constitutes the parallel arm resonator RS2.

[0136] In Embodiment 1, when viewed from above in the thickness direction D1 of the piezoelectric layer 4, the first electrode 51 and the second electrode 52 are straight, but this is not a limitation. 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.

[0137] Alternatively, the elastic wave resonator 5 of any of the following embodiments can be used instead of the elastic wave resonator 5 in the elastic wave device 1a of the modified embodiment 1: embodiments 2 to 4, the following embodiment 2, and the following modification 1 of embodiment 2.

[0138] In embodiment 1, the first electrode 51 and the second electrode 52 each include main electrode films 511 and 521 and close-fitting films 512 and 522, but the close-fitting films 512 and 522 may be omitted. That is, the first electrode 51 and the second electrode 52 may each only include main electrode films 511 and 521.

[0139] In Embodiment 1, the bonding layers (bonding films 512, 522) are one layer, but there can also be two or more bonding layers. As an example, consider the case where there are two bonding layers. In this case, if one of the bonding layers is a Ti film and the other is a NiCr film, it is preferable to stack them in the order of piezoelectric layer 4, Ti film, NiCr film, and main electrode films 511, 521.

[0140] Alternatively, other metal films can be formed on the main electrode films 511 and 521. As an example, consider the case where the metal film is a Ti film. In this case, it is sufficient to stack the piezoelectric layer 4, the Ti film as a close-fitting layer, the main electrode films 511 and 521, and the Ti film as another metal film in that order.

[0141] In embodiment 1, the thickness of each of the plurality of first electrodes 51 is thinner than the thickness of the piezoelectric layer 4, but the thickness of each of the plurality of first electrodes 51 may be the same as the thickness of the piezoelectric layer 4, or it may be thicker than the thickness of the piezoelectric layer 4.

[0142] Furthermore, the aforementioned variations 1 to 4 and other variations can also be applied to the elastic wave devices 1c and 1d described in Embodiment 2 below.

[0143] (Implementation Method 2)

[0144] The following is for reference Figure 16 as well as Figure 17 The elastic wave device 1c according to Embodiment 2 will be described. Furthermore, regarding the elastic wave device 1c 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 descriptions are omitted.

[0145] (2.1) Structure of elastic wave device

[0146] The elastic wave device 1c according to Embodiment 2 does not have the acoustic reflection layer 3 of the elastic wave device 1 according to Embodiment 1. In the elastic wave device 1c according to Embodiment 2, a piezoelectric layer 4 is disposed on a support substrate 2. Here, the support substrate 2 is a silicon substrate. The piezoelectric layer 4 is bonded to the support substrate 2 via a silicon oxide film 7. The elastic wave device 1c also has a cavity 26. The cavity 26 is located directly below the elastic wave resonator 5. That is, the cavity 26 sandwiches the piezoelectric layer and is disposed on the opposite side to the resonator 5. The elastic wave resonator 5, viewed from the thickness direction D1 of the piezoelectric layer 4, includes a first electrode 51 and a second electrode 52, and, viewed from the thickness direction D1 of the piezoelectric layer 4, includes a portion (defined region 45) of the piezoelectric layer 4 located between the first electrode 51 and the second electrode 52. In the elastic wave device 1c according to Embodiment 2, the cavity 26 is formed over the support substrate 2 and the silicon oxide film 7, and a portion of the piezoelectric layer 4 (a portion of the second main surface 42) is exposed. In the elastic wave device 1c according to Embodiment 2, the elastic wave resonator 5 does not have the acoustic reflection layer 3 of the elastic wave device 1 according to Embodiment 1. When viewed from the thickness direction D1 of the piezoelectric layer 4, the cavity 26 overlaps with a portion of each of the first wiring portion 61 and the second wiring portion 62. Alternatively, when viewed from the thickness direction D1 of the piezoelectric layer 4, the cavity 26 may not overlap with a portion of each of the first wiring portion 61 and the second wiring portion 62.

[0147] The thickness of the support substrate 2 is, for example, 50 μm or more and 500 μm or less. The thickness of the silicon oxide film 7 is, for example, 0.01 μm or more and 10 μm or less. The thickness of the piezoelectric layer 4 is the same as the thickness of the piezoelectric layer 4 of the elastic wave device 1 according to Embodiment 1.

[0148] (2.2) Manufacturing method of elastic wave device

[0149] In the manufacturing method of the elastic wave device 1c, 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 forms the basis of the piezoelectric layer 4, and the support substrate 2 are bonded together 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, a first wiring portion 61, and a second wiring portion 62 are formed on the piezoelectric layer 4. In the fifth step, a cavity 26 is formed. In the fourth step, the plurality of first electrodes 51, a plurality of second electrodes 52, a first wiring portion 61, and a second wiring portion 62 are formed using photolithography, etching, thin film formation, or the like. In step 5, the predetermined areas for forming cavities 26 in the support substrate 2 and the silicon oxide film are etched using photolithography and etching techniques. In step 5, the silicon oxide film 7 is etched as an etching stop layer, and then the unwanted 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. Furthermore, in steps 1 through 5, a silicon wafer is used as the support substrate 2, and a piezoelectric wafer is used as the piezoelectric substrate. In the method for manufacturing the elastic wave device 1c, multiple elastic wave devices 1c (chips) are obtained by dicing a wafer containing multiple elastic wave devices 1c.

[0150] The manufacturing method of the elastic wave device 1c 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 1c 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.

[0151] (2.3) Effects

[0152] The elastic wave device 1c according to Embodiment 2, like the elastic wave device 1 according to Embodiment 1, 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 D2 intersecting the thickness direction D1 of the piezoelectric layer 4. The elastic wave device 1c utilizes a thickness-sheared first-order mode bulk wave. The material of the piezoelectric layer 4 is lithium niobate or lithium tantalate. The first electrode 51 and the second electrode 52 each comprise aluminum layers 511 and 521 formed on the piezoelectric layer 4. The crystals constituting the aluminum layers 511 and 521... <111> The direction is orthogonal to the planes of the piezoelectric layer 4 in the aluminum layers 511 and 521. With the above structure, in the elastic wave device 1c according to Embodiment 2, the Q value can be improved even when miniaturization is promoted, and the distortion characteristics can be improved.

[0153] Furthermore, the elastic wave device 1c according to Embodiment 2, like the elastic wave device 1 according to Embodiment 1, 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 D2 intersecting the thickness direction D1 of the piezoelectric layer 4. In the elastic wave device 1c, 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 defined as p, and the thickness of the piezoelectric layer 4 is defined as d, where d / p is 0.5 or less. The material of the piezoelectric layer 4 is lithium niobate or lithium tantalate. The first electrode 51 and the second electrode 52 each include aluminum layers 511 and 521 formed on the piezoelectric layer 4. The crystals constituting the aluminum layers 511 and 521... <111> The direction is orthogonal to the planes of the piezoelectric layer 4 in the aluminum layers 511 and 521. With the above structure, in the elastic wave device 1c according to Embodiment 2, the Q value can be improved even when miniaturization is promoted, and the distortion characteristics can be improved.

[0154] Furthermore, the elastic wave device 1c according to Embodiment 2, by having a cavity 26, is able to confine the energy of the bulk wave within the piezoelectric layer 4, thereby obtaining a good Q value.

[0155] In the elastic wave device 1c according to Embodiment 2, the piezoelectric layer 4 is bonded to the support substrate 2 via the silicon oxide film 7, but the silicon oxide film 7 is not an essential component. Furthermore, in addition to the silicon oxide film 7, other layers may be stacked between the support substrate 2 and the piezoelectric layer 4. Furthermore, in the elastic wave device 1c according to Embodiment 2, the cavity 26 is formed to penetrate the support substrate 2 in its thickness direction, but it is not limited to this; it may not penetrate the support substrate 2 and may be formed by the internal space of a recess formed on the first main surface 21 of the support substrate 2. Furthermore, the elastic wave resonator 5 may also include other films (e.g., a dielectric film such as the silicon oxide film 7) stacked on the second main surface 42 of the piezoelectric layer 4.

[0156] (2.4) Variation Example

[0157] The above-described embodiment 2 is merely one of the various embodiments of the present invention. As long as the purpose of the present invention can be achieved, the above-described embodiment 2 can be modified in various ways according to design, etc.

[0158] (2.4.1) Variation Example 1

[0159] The following is for reference Figure 18 The elastic wave device 1d according to the variation 1 of Embodiment 2 will be described. In addition, for the elastic wave device 1d according to the variation 1 of Embodiment 2, the same reference numerals are used for the same constituent elements as those of the elastic wave device 1c according to Embodiment 2, and the description is omitted.

[0160] The elastic wave device 1d according to Variation 1 of Embodiment 2 differs from the elastic wave device 1c according to Embodiment 2 in that, like the elastic wave device 1b according to Variation 2 of Embodiment 1, it 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 1b.

[0161] (2.4.2) Other variations

[0162] The variations 1 to 4 of Embodiment 1 and other variations described above can also be applied to the elastic wave device 1c of Embodiment 2 and the elastic wave device 1d of Variation 1.

[0163] (Way)

[0164] Based on the embodiments described above, the following methods are disclosed in this specification.

[0165] The elastic wave device (1; 1a; 1b; 1c; 1d) 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 opposite each other in a direction (D2) intersecting the thickness direction (D1) of the piezoelectric layer (4). The first electrode (51) and the second electrode (52) are adjacent electrodes. The elastic wave device (1; 1a; 1b; 1c; 1d) utilizes a thickness-sheared first-order mode bulk wave. The material of the piezoelectric layer (4) is lithium niobate or lithium tantalate. The first electrode (51) and the second electrode (52) each contain an aluminum layer (511, 521) formed on the piezoelectric layer (4). The orientation direction of the crystals constituting the aluminum layer (511, 521) is orthogonal to the face of the piezoelectric layer (4) in the aluminum layer (511, 521).

[0166] According to this method, the Q value can be improved even when miniaturization is advanced, and the distortion characteristics can be enhanced.

[0167] The elastic wave device (1; 1a; 1b; 1c; 1d) 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 positioned opposite each other in a direction (D2) intersecting the thickness direction (D1) of the piezoelectric layer (4). In the elastic wave device (1; 1a; 1b; 1c; 1d), in any cross-section along the thickness direction (D1), 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, where d / p is 0.5 or less. The material of the piezoelectric layer (4) is lithium niobate or lithium tantalate. The first electrode (51) and the second electrode (52) each include an aluminum layer (511, 521) formed on the piezoelectric layer (4). The orientation of the crystals constituting the aluminum layers (511, 521) is orthogonal to the face of the piezoelectric layer (4) in the aluminum layers (511, 521).

[0168] According to this method, the Q value can be improved even when miniaturization is advanced, and the distortion characteristics can be enhanced.

[0169] In the elastic wave device (1; 1a; 1b; 1c; 1d) involved in the third method, in the first or second method, the first electrode (51) and the second electrode (52) are opposite each other on the same main surface (e.g., the first main surface 41) of the piezoelectric layer (4).

[0170] In the elastic wave device (1; 1a; 1b; 1c; 1d) involved in the fourth method, in any of the first to third methods, the orientation direction is a direction orthogonal to the main surface (e.g., the first main surface 41) of the piezoelectric layer (4).

[0171] According to this method, the Q value can be improved even when miniaturization is advanced, and the distortion characteristics can be enhanced.

[0172] In the elastic wave device (1; 1a; 1b; 1c; 1d) involved in the fifth method, in any of the methods 1 to 4, the aluminum layer (511, 521) is an epitaxial layer.

[0173] According to this method, the Q value can be improved even when miniaturization is advanced, and the distortion characteristics can be enhanced.

[0174] In the elastic wave device (1; 1a; 1b; 1c; 1d) involved in the sixth method, in any of the methods 1 to 5, the Euler angle of the piezoelectric layer (4) is ( , θ, ψ) is (0°±10°, 0°±10°, ψ).

[0175] According to this method, the Q value can be improved even when miniaturization is advanced, and the distortion characteristics can be enhanced.

[0176] In the elastic wave device (1; 1a; 1b; 1c; 1d) involved in the seventh method, in the second method, d / p is 0.24 or less.

[0177] This method allows for a larger relative bandwidth.

[0178] In the elastic wave device (1; 1a; 1b; 1c; 1d) according to the eighth embodiment, in the seventh embodiment, the first electrode (51) and the second electrode (52) are electrodes adjacent to each other. The first electrode (51) has a first electrode main portion (510) that intersects the second electrode (52) in the direction opposite to the first electrode (51) and the second electrode (52). The second electrode (52) has a second electrode main portion (520) that intersects the first electrode (51) in the direction opposite to the first electrode (51) and the second electrode (52). The piezoelectric layer (4) has a defined region (45) that, when viewed from the thickness direction (D1), 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) and is located between the first electrode (51) and the second electrode (52). The elastic wave device (1; 1a; 1b; 1c; 1d) satisfies the following condition: MR ≤ 1.75 × (d / p) + 0.075. Here, S1 is the area of ​​the first electrode main part (510) viewed from the thickness direction (D1). S2 is the area of ​​the second electrode main part (520) viewed from the thickness direction (D1). S0 is the area of ​​the specified region (45) viewed from the thickness direction (D1). MR is the structural parameter defined by (S1 + S2) / (S1 + S2 + S0).

[0179] This method can suppress spurious signals within the frequency band.

[0180] In the elastic wave device (1; 1a; 1b; 1c; 1d) according to the 9th method, in any of the 1st to 8th methods, it 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).

[0181] Explanation of reference numerals in the attached figures

[0182] 1, 1a, 1b, 1c, 1d: Elastic wave devices;

[0183] 2: Support base plate;

[0184] 21: 1st main side;

[0185] 22: The second main surface;

[0186] 3: Sound-reflecting layer;

[0187] 31: Low acoustic impedance layer;

[0188] 311: First low acoustic impedance layer;

[0189] 312: Second low acoustic impedance layer;

[0190] 313: Third low acoustic impedance layer;

[0191] 32: High acoustic impedance layer;

[0192] 321: First high acoustic impedance layer;

[0193] 322: Second high acoustic impedance layer;

[0194] 4: Piezoelectric layer;

[0195] 41: 1st main surface;

[0196] 42: 2nd main surface;

[0197] 45: Designated area;

[0198] 451: Region 1;

[0199] 452: Region 2;

[0200] 5: Elastic wave resonator;

[0201] 51: First electrode;

[0202] 510: Main part of the first electrode;

[0203] 511: Main electrode film (aluminum layer);

[0204] 512: Adhesive film;

[0205] 513: 1st main surface;

[0206] 514: 2nd main surface;

[0207] 515: Side view;

[0208] 52: Second electrode;

[0209] 520: Main part of the second electrode;

[0210] 521: Main electrode film (aluminum layer);

[0211] 522: Adhesive film;

[0212] 523: 1st main surface;

[0213] 524: 2nd main surface;

[0214] 525: Side view;

[0215] 61: First wiring section;

[0216] 611: Busbar 1;

[0217] 62: Second wiring section;

[0218] 621: Second busbar;

[0219] 7: Silicon oxide film;

[0220] 8: Reflector;

[0221] 81: Electrode finger;

[0222] 9: Dielectric film;

[0223] 12: Path 1;

[0224] 13: Path 2;

[0225] 14: Path 2;

[0226] 15: Input terminals;

[0227] 16: Output terminals;

[0228] 17: Grounding terminal;

[0229] 18: Grounding terminal;

[0230] 400: Piezoelectric substrate;

[0231] 401: 1st main surface;

[0232] 402: 2nd main surface;

[0233] RS1: Series arm resonator;

[0234] RS2: Parallel arm resonator;

[0235] D1: Thickness direction (first direction);

[0236] D2: Second direction;

[0237] D3: 3rd direction;

[0238] DA1: Distribution region 1;

[0239] DA2: Second distribution region;

[0240] DL1: Approximate straight line;

[0241] DL2: Approximate straight line;

[0242] MR: Construction parameters;

[0243] N1, N2: Nodes;

[0244] PZ1: Polarization direction;

[0245] VP1: Imaginary plane;

[0246] d: Thickness of the piezoelectric layer;

[0247] p: Distance between center lines.

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 elastic wave device utilizes thickness shearing of first-order mode volume waves. in, The piezoelectric layer is made of lithium niobate or lithium tantalate. The first electrode and the second electrode each comprise an aluminum layer formed on the piezoelectric layer. The orientation direction of the crystals constituting the aluminum layer is orthogonal to the plane of the piezoelectric layer side in the aluminum layer.

2. 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, 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 first electrode and the second electrode each comprise an aluminum layer formed on the piezoelectric layer. The orientation direction of the crystals constituting the aluminum layer is orthogonal to the plane of the piezoelectric layer side in the aluminum layer.

3. 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.

4. The elastic wave device according to claim 1 or 2, wherein, The orientation direction is orthogonal to the main surface of the piezoelectric layer.

5. The elastic wave device according to claim 1 or 2, wherein, The aluminum layer is an epitaxial layer.

6. The elastic wave device according to claim 1 or 2, wherein, The Euler angles (φ, θ, ψ) of the piezoelectric layer are (0°±10°, 0°±10°, ψ).

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

24.

8. The elastic wave device according to claim 7, wherein, The first electrode has a main portion that intersects the second electrode in a direction opposite to the first electrode and the second electrode. The second electrode has a main portion that intersects the first electrode in a direction opposite to the first electrode and the second electrode. The piezoelectric layer has a defined region, viewed from the thickness direction, intersecting both the first and second electrodes in the direction opposite to the first and second electrodes, and located between the first and second electrodes. Viewed from above in the thickness direction, 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 condition: MR≤1.75×(d / p)+0.

075.

9. The elastic wave device of Claim 1 or 2, wherein, It also has: The first wiring portion is connected to the first electrode; and The second wiring section is connected to the second electrode.

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