Filters and multiplexers

Abstract

To improve a pass characteristic of a filter.SOLUTION: A filter comprises: a series resonator; and a parallel resonator. The series resonator comprises: a piezoelectric layer 14 that is formed by a single crystal lithium niobate layer or a single crystal lithium tantalate layer, and in which a X-shaft direction of a crystal direction is a flat surface direction and a thickness direction is a direction where a +Z-shaft direction of the crystal direction is rotated about 105° in +Y-shaft direction; and a lower electrode 12 and an upper electrode 16 which face each other across the piezoelectric layer 14 to form a resonance region 50 and which are led out from the resonance region 50 in a direction that is similar to the X-shaft direction of the crystal direction of the piezoelectric layer 14. The parallel resonator comprises: the piezoelectric layer 14 that is formed by the single crystal lithium niobate layer or the single crystal lithium tantalate layer, and in which the X-shaft direction of the crystal direction is the flat surface direction, and the thickness direction is a direction obtained by rotating the +Z-shaft direction of the crystal direction about 105° in the +Y-shaft direction; and the lower part electrode 12 and the upper part electrode 16 which face each other across the piezoelectric layer 14 to form the resonance region 50, and which are led from the resonance region 50 in a direction orthogonal to the X-shaft direction of the crystal direction of the piezoelectric layer 14.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The present invention relates to a filter and a multiplexer.

Background Art

[0002] As a filter and a duplexer for a high-frequency circuit of a wireless terminal such as a mobile phone, filters and duplexers using a piezoelectric thin-film resonator are known. The piezoelectric thin-film resonator includes a piezoelectric layer and a pair of electrodes sandwiching the piezoelectric layer. A region where a pair of electrodes face each other with the piezoelectric layer interposed therebetween is a resonance region where elastic waves resonate. It is known to use a lithium niobate layer, a lithium tantalate layer, or the like for the piezoelectric layer (for example, Patent Documents 1 to 3).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a single crystal piezoelectric material such as lithium niobate, lithium tantalate, or quartz is used for the piezoelectric layer, the vibration in the resonance region may become thickness-shear vibration. When a filter is formed using a piezoelectric thin-film resonator having thickness-shear vibration as a series resonator and a parallel resonator, there is still room for improvement in terms of improving the passing characteristics.

[0005] An object of the present invention is to improve the passing characteristics.

Means for Solving the Problems

[0006] The present invention relates to a series resonator comprising: a substrate; a first piezoelectric layer provided on the substrate and connected in series between an input terminal and an output terminal, wherein the first piezoelectric layer is a single-crystal lithium niobate layer or a single-crystal lithium tantalate layer, the X-axis direction of the crystal orientation is in the planar direction and the thickness direction is in the direction obtained by rotating the +Z axis direction of the crystal orientation by approximately 105° in the +Y axis direction; and a pair of first electrodes that form a first resonant region opposite to the first piezoelectric layer, and are drawn out from the first resonant region in the same first direction as the X-axis direction of the crystal orientation of the first piezoelectric layer; and the substrate The filter comprises a parallel resonator comprising: a second piezoelectric layer provided on top and connected in parallel between the input terminal and the output terminal, which is a single-crystal lithium niobate layer or a single-crystal lithium tantalate layer whose X-axis direction of crystal orientation is in the planar direction and whose thickness direction is in the direction obtained by rotating the +Z-axis direction of crystal orientation by approximately 105° in the +Y-axis direction; and a pair of second electrodes that form a second resonance region opposite to the second piezoelectric layer on either side of the second piezoelectric layer and are drawn out from the second resonance region in a second direction perpendicular to the X-axis direction of the crystal orientation of the second piezoelectric layer.

[0007] The present invention relates to a series resonator comprising: a substrate; a substrate and connected in series between an input terminal and an output terminal, comprising: a first piezoelectric layer provided on the substrate and connected in series between an input terminal and an output terminal, wherein the X-axis direction of the crystal orientation is in the thickness direction and the Y-axis and Z-axis directions of the crystal orientation are in the planar direction; and a pair of first electrodes that form a first resonant region opposite to the first piezoelectric layer, with the +Y-axis direction of the crystal orientation of the first piezoelectric layer facing each other, and are drawn out from the first resonant region in a first direction orthogonal to the direction obtained by rotating the +Y-axis direction of the crystal orientation of the first piezoelectric layer by 42° in the -Z-axis direction; and a parallel resonator provided on the substrate and connected in parallel between the input terminal and the output terminal, comprising: a second piezoelectric layer provided on the substrate and connected in parallel between the input terminal and the output terminal, wherein the X-axis direction of the crystal orientation is in the thickness direction and the Y-axis and Z-axis directions of the crystal orientation are in the planar direction; and a pair of second electrodes that form a second resonant region opposite to the second piezoelectric layer, with the +Y-axis direction of the crystal orientation of the second piezoelectric layer by 42° in the -Z-axis direction, and are drawn out from the second resonant region in the same second direction as the direction obtained by rotating the +Y-axis direction of the crystal orientation of the second piezoelectric layer by 42°.

[0008] The present invention relates to a filter comprising: a substrate; a series resonator provided on the substrate and connected in series between an input terminal and an output terminal, comprising a first piezoelectric layer and a pair of first electrodes that form a first resonant region opposite to the first piezoelectric layer, excite the first piezoelectric layer to generate thickness-slip vibrations, and are drawn out from the first resonant region in a first direction perpendicular to the vibration direction of the thickness-slip vibrations excited by the first piezoelectric layer; and a parallel resonator provided on the substrate and connected in parallel between the input terminal and the output terminal, comprising a second piezoelectric layer and a pair of second electrodes that form a second resonant region opposite to the second piezoelectric layer, excite the second piezoelectric layer to generate thickness-slip vibrations, and are drawn out from the second resonant region in the same second direction as the vibration direction of the thickness-slip vibrations excited by the second piezoelectric layer.

[0009] In the above configuration, the pair of first electrodes are linearly drawn out in the first direction from the first resonance region with a length of 0.75 times or more the thickness of the first piezoelectric layer in the first resonance region, and the pair of second electrodes are linearly drawn out in the second direction from the second resonance region with a length of 0.75 times or more the thickness of the second piezoelectric layer in the second resonance region.

[0010] In the above configuration, the first wiring is connected to the end of the pair of first electrodes opposite to the first resonant region, and the second wiring is connected to the end of the pair of second electrodes opposite to the second resonant region, wherein the length of the first wiring changes in a direction perpendicular to the first direction as it moves away from the pair of first electrodes and / or the length of the second wiring changes in a direction perpendicular to the second direction as it moves away from the pair of second electrodes.

[0011] In the above configuration, a plurality of series resonators are arranged in the same direction as the first direction, and the first series resonator and the second series resonator among the plurality of series resonators are connected to the input terminal and the output terminal, respectively, by first wiring, the length of which increases in the direction perpendicular to the first direction as it moves away from the pair of first electrodes.

[0012] In the above configuration, the parallel resonators can be connected to the first wiring between the plurality of series resonators by a second wiring whose length in the direction perpendicular to the second direction decreases as it moves away from the pair of second electrodes.

[0013] In the above configuration, the system may include a first wiring connected to the end of the pair of first electrodes opposite to the first resonant region, and a second wiring connected to the end of the pair of second electrodes opposite to the second resonant region, wherein the first wiring is drawn out from the pair of first electrodes in a direction intersecting the first direction and / or the second wiring is drawn out from the pair of second electrodes in a direction intersecting the second direction.

[0014] In the above configuration, the system may be configured to include a plurality of series resonators arranged in a direction perpendicular to the first direction, wherein the first series resonator and the second series resonator are connected to the input terminal and the output terminal, respectively, by first wiring drawn from the pair of first electrodes in a direction intersecting the first direction, and the parallel resonator is connected to the ground terminal by second wiring drawn from the pair of second electrodes in a direction intersecting the second direction.

[0015] In the above configuration, the first piezoelectric layer and the second piezoelectric layer can be configured as a continuous single piezoelectric layer.

[0016] The present invention is a multiplexer comprising the filter described above. [Effects of the Invention]

[0017] According to the present invention, the passage characteristics can be improved. [Brief explanation of the drawing]

[0018] [Figure 1]Fig. 1(a) is a plan view of a piezoelectric thin film resonator used in the filter according to Example 1, and Fig. 1(b) is a cross-sectional view taken along the line A-A of Fig. 1(a). [Figure 2] Fig. 2 is a perspective view of the model used in Simulation 1. [Figure 3] Figs. 3(a) to 3(c) are perspective views showing the crystal orientation of the piezoelectric layer in Sample A. [Figure 4] Figs. 4(a) and 4(b) are perspective views showing the crystal orientation of the piezoelectric layer in Sample B. [Figure 5] Fig. 5 is a simulation result of the admittance |Y| with respect to the frequency for Sample A and Sample B. [Figure 6] Fig. 6 is a perspective view of the model used in Simulation 2. [Figure 7] Fig. 7 is a simulation result of the admittance |Y| with respect to the frequency for the piezoelectric thin film resonator R1. [Figure 8] Fig. 8 is a circuit diagram of the filter according to Example 1. [Figure 9] Fig. 9(a) is a plan view of the filter according to Example 1, and Fig. 9(b) is a cross-sectional view taken along the line A-A of Fig. 9(a). [Figure 10] Fig. 10(a) is a perspective view of the series resonator in the filter according to Example 1, and Fig. 10(b) is a perspective view of the parallel resonator. [Figure 11] Fig. 11 is a plan view of the filter according to Modified Example 1 of Example 1. [Figure 12] Fig. 12 is a cross-sectional view of the piezoelectric thin film resonator according to the modified example. [Figure 13] Figs. 13(a) to 13(c) are plan views showing other examples of the resonance region. [Figure 14] Figs. 14(a) to 14(c) are plan views showing examples of the lower wiring and the upper wiring. [Figure 15] Figs. 15(a) to 15(c) are perspective views showing the crystal orientation of the piezoelectric layer when the piezoelectric layer is a single crystal lithium tantalate layer. [Figure 16]Figure 16(a) is a perspective view of the series resonator in the filter according to Example 2, and Figure 16(b) is a perspective view of the parallel resonator. [Figure 17] Figure 17 is a block diagram of the duplexer according to Example 3.

[0019] The embodiments of the present invention will be described below with reference to the drawings. [Example 1]

[0020] Figure 1(a) is a plan view of the piezoelectric thin-film resonator 100 used in the filter according to Example 1, and Figure 1(b) is a cross-sectional view AA of Figure 1(a). As shown in Figures 1(a) and 1(b), the piezoelectric thin-film resonator 100 has an acoustic reflective film 31 provided on a substrate 10, and a piezoelectric layer 14 provided on the acoustic reflective film 31. The upper and lower surfaces of the piezoelectric layer 14 are substantially flat. A lower electrode 12 and an upper electrode 16 are provided above and below the piezoelectric layer 14. The region in which the lower electrode 12 and the upper electrode 16 overlap in a plan view, with at least a part of the piezoelectric layer 14 in between, is the resonance region 50.

[0021] When high-frequency power is applied between the lower electrode 12 and the upper electrode 16, elastic waves are excited in the piezoelectric layer 14 within the resonant region 50, vibrating in a direction where the displacement of the elastic wave is approximately perpendicular to the Z direction (i.e., the strain direction relative to the thickness). This vibration is called thickness-slip vibration. The direction in which the displacement of the thickness-slip vibration is greatest (the direction of displacement of the thickness-slip vibration) is defined as the vibration direction of the thickness-slip vibration. The wavelength of the elastic wave is approximately twice the thickness of the piezoelectric layer 14. The planar shape of the resonant region 50 is, for example, approximately rectangular. The rectangle has four sides that are approximately straight. The extension directions of the four sides are the X and Y directions.

[0022] The acoustic reflective film 31 is made up of alternating layers of film 31b with low acoustic impedance and film 31a with high acoustic impedance. The thickness of films 31a and 31b is, for example, approximately λ / 4 (where λ is the wavelength of an elastic wave). As a result, the acoustic reflective film 31 reflects elastic waves. The number of layers of films 31a and 31b can be set arbitrarily. The acoustic reflective film 31 only needs to consist of at least two layers with different acoustic properties stacked at intervals. Alternatively, the substrate 10 may be one of the at least two layers with different acoustic properties of the acoustic reflective film 31. For example, the acoustic reflective film 31 may be made up of a single layer of film with different acoustic impedances provided in the substrate 10. In a plan view, the acoustic reflective film 31 overlaps the resonance region 50, and the acoustic reflective film 31 is the same size as or larger than the resonance region 50.

[0023] The substrate 10 is, for example, a silicon substrate, sapphire substrate, alumina substrate, spinel substrate, quartz substrate, crystal substrate, glass substrate, ceramic substrate, or GaAs substrate. The piezoelectric layer 14 is, for example, a single-crystal lithium niobate layer, a single-crystal lithium tantalate layer, or a single-crystal crystal. Example 1 will describe the case where the piezoelectric layer 14 is a single-crystal lithium niobate layer.

[0024] The lower electrode 12 and the upper electrode 16 are single-layer films or multilayer films of, for example, ruthenium (Ru), chromium (Cr), aluminum (Al), titanium (Ti), copper (Cu), molybdenum (Mo), tungsten (W), tantalum (Ta), platinum (Pt), rhodium (Rh), or iridium (Ir).

[0025] Furthermore, in the resonance region 50, the first additional film may be provided on the upper surface of the lower electrode 12, the lower surface of the lower electrode 12, and / or within the lower electrode 12. Similarly, in the resonance region 50, the first additional film may be provided on the upper surface of the upper electrode 16, the lower surface of the upper electrode 16, and / or within the upper electrode 16. The first additional film is a metal film or insulating film with a density lower than that of the lower electrode 12 and the upper electrode 16. By providing the first additional film, the electromechanical coupling coefficient can be adjusted without significantly degrading the resonance characteristics.

[0026] Furthermore, a second additional film may be provided on the upper electrode 16 and / or below the lower electrode 12 in the edge regions located on both sides in the X and / or Y directions relative to the central region of the resonance region 50. The second additional film is not provided in the central region of the resonance region 50 that is sandwiched between the edge regions. The second additional film provided in the edge regions located on both sides in the X direction is stretched substantially in the Y direction, and its width in the X direction is substantially constant in the Y direction. Similarly, the second additional film provided in the edge regions located on both sides in the Y direction is stretched substantially in the X direction, and its width in the Y direction is substantially constant in the X direction. The second additional film is an insulating film such as a metal film or silicon oxide film, silicon nitride film, aluminum oxide film, tantalum oxide film, or niobium oxide film, as exemplified for the lower electrode 12 and upper electrode 16. By providing the second additional film, a piston mode is realized, and spurious emissions can be suppressed.

[0027] [Simulation 1] Figure 2 is a perspective view of the model used in Simulation 1. As shown in Figure 2, the model used in Simulation 1 has a piezoelectric layer 14 provided on a lower electrode 12 having a lower layer 11a and an upper layer 11b, and an upper electrode 16 provided on the piezoelectric layer 14. The simulation conditions are as follows. Wavelength λ of the elastic wave: twice the thickness of the piezoelectric layer 14 Lower layer 11a of lower electrode 12: 18 nm thick chromium layer Upper layer 11b of lower electrode 12: Ruthenium layer with a thickness of 100 nm Piezoelectric layer 14: Lithium niobate layer with a thickness of 1300 nm Upper electrode 16: Ruthenium layer with a thickness of 100 nm Conditions in the X direction: The width of the resonant region 50 in the X direction is 30λ Conditions in the Y direction: The width of the resonant region 50 in the Y direction is 0.5λ, and the boundary conditions are infinitely continuous.

[0028] In Simulation 1, the resonance characteristics of Sample A and Sample B were simulated for samples A and B, which differ in the extraction directions of the lower electrode 12 and upper electrode 16 relative to the vibration direction of the thickness shear vibration excited in the piezoelectric layer 14. Figures 3(a) to 3(c) are perspective views showing the crystal orientation of the piezoelectric layer 14 in Sample A. Figures 4(a) and 4(b) are perspective views showing the crystal orientation of the piezoelectric layer 14 in Sample B. Here, the Euler angles (α, β, γ) are defined as follows. In a right-handed XYZ coordinate system, the normal direction to the upper surface of the piezoelectric layer 14 is defined as the Z direction, and the directions perpendicular to the Z direction and mutually perpendicular in the plane direction of the upper surface of the piezoelectric layer 14 are defined as the X and Y directions. First, the X, Y, and Z directions are defined as the X-axis, Y-axis, and Z-axis directions of the crystal orientation, respectively. Next, it is rotated α from the +X-axis direction to the +Y-axis direction around the Z-axis direction. After the α rotation, it is rotated β from the +Y-axis direction to the +Z-axis direction around the X-axis direction. The crystal is rotated γ from the +X axis to the +Y axis around the Z axis after β rotation. The Euler angles of the crystal whose crystal orientation has been rotated in this way are (α, β, γ). In this embodiment, α, β, and γ are expressed using values ​​from 0° to 180°, but the Euler angles expressed using (α, β, γ) include equivalent Euler angles. For example, equivalent Euler angles include Euler angles obtained by fixing the crystal axis of the crystal orientation of the piezoelectric layer 14 and rotating the coordinate axes of the orthogonal coordinate system of the piezoelectric layer 14.

[0029] First, the crystal orientation of the piezoelectric layer 14 in sample A will be explained using Figures 3(a) to 3(c). As shown in Figure 3(a), the +X direction, +Y direction, and +Z direction are defined as the +X axis direction, +Y axis direction, and +Z axis direction of the piezoelectric layer 14's crystal orientation, respectively. As shown in Figure 3(b), from the state in Figure 3(a), the +X axis direction and +Y axis direction are rotated by 90° from the +X axis direction to the +Y axis direction on the X-Y axis plane, centered on the Z axis direction. Next, as shown in Figure 3(c), the +Y axis direction and +Z axis direction are rotated by 105° from the +Y axis direction to the +Z axis direction on the Y-Z axis plane, centered on the X axis direction. With this rotation, the +Z direction becomes the direction obtained by rotating the +Z axis direction by 105° toward the +Y axis direction. At this time, the X direction is the vibration direction 60 of the thickness shear vibration. In Euler angles, this is (90°, 105°, 0°).

[0030] The lower electrode 12 is drawn out in the +X direction from the resonant region 50, and the upper electrode 16 is drawn out in the -X direction from the resonant region 50. Therefore, in sample A, the lower electrode 12 and the upper electrode 16 are drawn out in the same direction as the vibration direction 60 of the thickness shear vibration from the resonant region 50.

[0031] Next, the crystal orientation of the piezoelectric layer 14 in sample B will be explained using Figures 4(a) and 4(b). As shown in Figure 4(a), the +X direction, +Y direction, and +Z direction are defined as the +X axis direction, +Y axis direction, and +Z axis direction of the piezoelectric layer 14 crystal orientation, respectively. As shown in Figure 4(b), from the state in Figure 4(a), the +Y axis direction and +Z axis direction are rotated by 105° from the +Y axis direction toward the +Z axis direction on the Y-Z axis plane, centered on the X axis direction. When rotated in this way, the +Z direction becomes the direction obtained by rotating the +Z axis direction toward the +Y axis direction by 105°. At this time, the Y direction is the vibration direction 60 of the thickness shear vibration. In Euler angles, this becomes (0°, 105°, 0°).

[0032] The lower electrode 12 is drawn out in the +X direction from the resonant region 50, and the upper electrode 16 is drawn out in the -X direction from the resonant region 50. Therefore, in sample B, the lower electrode 12 and the upper electrode 16 are drawn out from the resonant region 50 in a direction perpendicular to the vibration direction 60 of the thickness shear vibration.

[0033] Figure 5 shows the simulation results of admittance |Y| as a function of frequency for samples A and B. As shown in Figure 5, at the resonant frequency fr, sample B had a larger admittance |Y| and a larger Q value compared to sample A. At the anti-resonant frequency fa, sample A had a larger admittance |Y| and a larger Q value compared to sample B.

[0034] Here, the amount of displacement generated in the resonant region 50 when high-frequency power is applied between the lower electrode 12 and the upper electrode 16 was simulated for samples A and B. The simulation results showed that the maximum displacement at the resonant frequency was 1.5 nm for sample A and 2.0 nm for sample B.

[0035] Thus, at the resonant frequency, sample B showed a larger maximum displacement compared to sample A. Larger displacements tend to result in a larger Q-factor. Therefore, as shown in Figure 5, at the resonant frequency fr, sample B's Q-factor is considered to be larger than that of sample A. The same is likely true at the anti-resonant frequency fa.

[0036] The insertion loss in the passband of a filter decreases as the Q value of the resonator increases. In a ladder-type filter, the passband is located near the resonant frequency of the series resonator and near the anti-resonant frequency of the parallel resonator. Therefore, the passband characteristics of the filter can be improved by using a resonator with a large Q value at the resonant frequency as the series resonator and a resonator with a large Q value at the anti-resonant frequency as the parallel resonator. From the above simulation results, it can be seen that it is preferable to use sample A, which has a large Q value at the anti-resonant frequency fa, as the parallel resonator and sample B, which has a large Q value at the resonant frequency fr, as the series resonator.

[0037] In Sample A, the lower electrode 12 and upper electrode 16 are drawn out from the resonance region 50 in the same direction as the vibration direction 60 of the thickness shear vibration. In Sample B, the lower electrode 12 and upper electrode 16 are drawn out from the resonance region 50 in a direction perpendicular to the vibration direction 60 of the thickness shear vibration. Therefore, a piezoelectric thin film resonator in which the lower and upper electrodes are drawn out from the resonance region in the same direction as the vibration direction of the thickness shear vibration is used as the parallel resonator of a ladder-type filter. A piezoelectric thin film resonator in which the lower and upper electrodes are drawn out from the resonance region in a direction perpendicular to the vibration direction of the thickness shear vibration is used as the series resonator of a ladder-type filter. This improves the transmission characteristics of the ladder-type filter.

[0038] [Simulation 2] Figure 6 is a perspective view of the model used in Simulation 2. As shown in Figure 6, the model used in Simulation 2 has a piezoelectric layer 14 on a lower electrode 12 having a lower layer 11a and an upper layer 11b, and upper electrodes 16a and 16b on the piezoelectric layer 14. As a result, a piezoelectric thin film resonator R1 having a lower electrode 12, a piezoelectric layer 14 and an upper electrode 16a, and a piezoelectric thin film resonator R2 having a lower electrode 12, a piezoelectric layer 14 and an upper electrode 16b are provided adjacent to each other. Piezoelectric thin film resonators R1 and R2 share a single lower electrode 12 and a single piezoelectric layer 14. In the piezoelectric thin film resonators R1 and R2, an additional film 28 is provided on the upper electrodes 16a and 16b in the edge regions 52 located on both sides in the X direction with respect to the central region 54 of the resonance region 50.

[0039] The resonance characteristics of piezoelectric thin-film resonator R1 were simulated for multiple samples with different distances L between piezoelectric thin-film resonators R1 and R2, when the same high-frequency power was applied between the lower electrode 12 and the upper electrode 16a and between the lower electrode 12 and the upper electrode 16b. The simulation conditions were as follows. Wavelength λ of the elastic wave: twice the thickness of the piezoelectric layer 14 Vibration direction of thickness sliding vibration: Y direction Lower layer 11a of lower electrode 12: 18 nm thick chromium layer Upper layer 11b of lower electrode 12: Ruthenium layer with a thickness of 100 nm Piezoelectric layer 14: Lithium niobate layer with a thickness of 1300 nm Upper electrode 16: Ruthenium layer with a thickness of 100 nm Addition film 28: Ruthenium film with a thickness of 100 nm and a width of 1.95 μm in the X direction. Conditions in the X direction: The width of the resonant region 50 in the X direction is 30λ Conditions in the Y direction: The width of the resonant region 50 in the Y direction is 0.5λ, and the boundary conditions are infinitely continuous. Distance L: 0.5λ, 0.625λ, 0.75λ, 0.875λ, 1.0λ

[0040] Figure 7 shows the simulation results of the admittance |Y| of the piezoelectric thin film resonator R1 as a function of frequency. As shown in Figure 7, when the distance L is short, spurious emissions occur at frequencies lower than the resonant frequency fr due to the influence of the adjacent piezoelectric thin film resonator R2, but as the distance L increases, the spurious emissions are reduced. When the distance L is 0.75λ, the spurious emissions are sufficiently reduced, and when the distance L is 1.0λ, almost no spurious emissions occur.

[0041] The results of Simulation 2 show that the distance L between adjacent piezoelectric thin film resonators is preferably 0.75λ or greater, more preferably 0.875λ or greater, and even more preferably 1.0λ or greater. In other words, in a single piezoelectric thin film resonator, the lower electrode 12 and the upper electrode 16 are preferably drawn out from the resonance region 50 with a length of 0.375λ or greater, more preferably 0.4375λ or greater, and even more preferably 0.5λ or greater.

[0042] Figure 8 is a circuit diagram of the filter 500 according to Embodiment 1. As shown in Figure 8, the filter 500 has one or more series resonators S1 to S4 connected in series and one or more parallel resonators P1 to P3 connected in parallel between the input terminal Tin and the output terminal Tout. The one or more series resonators S1 to S4 are provided in the path between the input terminal Tin and the output terminal Tout. One end of the one or more parallel resonators P1 to P3 is connected to the path between the input terminal Tin and the output terminal Tout, and the other end is grounded (connected to the ground terminal Tg). The number of resonators in the ladder-type filter can be set as appropriate.

[0043] Figure 9(a) is a plan view of the filter 500 according to Embodiment 1, and Figure 9(b) is a cross-sectional view of AA in Figure 9(a). In Figure 9(a), the lower electrode 12 and lower wirings 22a and 22b are shown with dashed lines, and the upper electrode 16 and upper wirings 26a and 26b are shown with solid lines. Also in Figure 9(a), hatching is applied to the resonance regions 50 of the series resonators S1 to S4 and the parallel resonators P1 to P3. As shown in Figures 9(a) and 9(b), the series resonators S1 to S4 and the parallel resonators P1 to P3 are formed on a single piezoelectric layer 14.

[0044] Figure 10(a) is a perspective view of the series resonators S1 to S4 in the filter 500 according to Example 1, and Figure 10(b) is a perspective view of the parallel resonators P1 to P3. Since the piezoelectric layer 14 is a single-crystal lithium niobate layer, as shown in Figures 10(a) and 10(b), the vibration direction 60 of the thickness shear vibration is perpendicular to the X-axis direction of the crystal orientation of the piezoelectric layer 14, and is approximately in the X direction. For example, the Euler angles are (90°±5°, 105°±5°, 0°±5°).

[0045] As shown in Figure 10(a), the lower electrodes 12 and upper electrodes 16 of the series resonators S1 to S4 are linearly drawn from the resonance region 50 in the same direction as the X-axis direction of the crystal orientation of the piezoelectric layer 14 (for example, the Y-direction). In other words, the lower electrodes 12 and upper electrodes 16 of the series resonators S1 to S4 are linearly drawn from the resonance region 50 in a direction perpendicular to the vibration direction 60 of the thickness shear vibration. As shown in Figure 10(b), the lower electrodes 12 and upper electrodes 16 of the parallel resonators P1 to P3 are linearly drawn from the resonance region 50 in a direction perpendicular to the X-axis direction of the crystal orientation of the piezoelectric layer 14 (for example, the X-direction). In other words, the lower electrodes 12 and upper electrodes 16 of the parallel resonators P1 to P3 are linearly drawn from the resonance region 50 in the same direction as the vibration direction 60 of the thickness shear vibration.

[0046] As shown in Figures 9(a) and 9(b), the series resonators S1 to S4 are arranged in a straight line in the Y direction. Therefore, the direction in which the series resonators S1 to S4 are arranged is the same as the direction in which the lower electrodes 12 and upper electrodes 16 of the series resonators S1 to S4 are drawn out from the resonance region 50. The lower electrodes 12 and upper electrodes 16 of the parallel resonators P1 to P3 are drawn out from the resonance region 50 in a direction perpendicular to the direction in which the series resonators S1 to S4 are arranged. In the series resonators S1 to S4 and the parallel resonators P1 to P3, the length (width) of the lower electrodes 12 and upper electrodes 16 in the direction perpendicular to the drawing direction at the point where they are drawn out from the resonance region 50 is a constant length that is greater than or equal to the length (width) of the resonance region 50 in the direction perpendicular to the drawing direction.

[0047] The series resonator S1 is connected to the input terminal Tin by an upper wiring 26a that widens as it moves away from the upper electrode 16. The series resonator S4 is connected to the output terminal Tout by an upper wiring 26a that widens as it moves away from the upper electrode 16. The parallel resonator P1 is connected to the lower wiring 22a between the series resonators S1 and S2 by a lower wiring 22b that narrows as it moves away from the lower electrode 12, and the parallel resonator P3 is connected to the lower wiring 22a between the series resonators S3 and S4 by a lower wiring 22b that narrows as it moves away from the lower electrode 12. The parallel resonator P2 is connected to the upper wiring 26a between the series resonators S2 and S3 by an upper wiring 26b that narrows as it moves away from the upper electrode 16. Here, the lower electrode 12 and the upper electrode 16 refer to portions that are linearly drawn out from the resonant region 50 for a predetermined length. The lower wiring 22a, 22b and the upper wiring 26a, 26b are the parts that connect between the electrodes of the resonator or between the electrodes of the resonator and the terminals, and are connected to the end opposite to the resonant region 50 of the electrodes. The electrodes and wiring may be formed of the same material or of different materials.

[0048] [Modified Example 1] Figure 11 is a plan view of filter 510 according to Modification 1 of Embodiment 1. As shown in Figure 11, the series resonators S1 to S4 are arranged in a straight line in the X direction. Therefore, the direction in which the series resonators S1 to S4 are arranged is perpendicular to the direction in which the lower electrodes 12 and upper electrodes 16 of the series resonators S1 to S4 are drawn out from the resonance region 50. The lower electrodes 12 and upper electrodes 16 of the parallel resonators P1 to P3 are drawn out from the resonance region 50 in the same direction as the series resonators S1 to S4 are arranged. The series resonator S1 is connected to the input terminal Tin by an upper wiring 26a drawn out from the upper electrode 16 in a direction intersecting the Y direction. The series resonator S4 is connected to the output terminal Tout by an upper wiring 26a drawn out from the upper electrode 16 in a direction intersecting the Y direction. The parallel resonators P1 and P3 are connected to the ground terminal Tg by upper wiring 26b drawn from the upper electrode 16 in a direction intersecting the X direction, and the parallel resonator P2 is connected to the ground terminal Tg by lower wiring 22b drawn from the lower electrode 12 in a direction intersecting the X direction. The other configurations are the same as in Embodiment 1 and will not be described.

[0049] In Example 1 and its modified form, as shown in Figures 10(a) and 10(b), the piezoelectric layer 14 is a single-crystal lithium niobate layer, where the X-axis direction of the crystal orientation is in the planar direction and the thickness direction is in the direction obtained by rotating the +Z-axis direction of the crystal orientation by approximately 105° in the +Y-axis direction. In this case, the vibration direction 60 of the thickness shear vibration is perpendicular to the X-axis direction of the crystal orientation of the piezoelectric layer 14. As shown in Figure 10(a), the lower electrodes 12 and upper electrodes 16 (a pair of first electrodes) of the series resonators S1 to S4 are drawn out from the resonance region 50 in the same direction as the X-axis direction of the crystal orientation of the piezoelectric layer 14. As shown in Figure 10(b), the lower electrodes 12 and upper electrodes 16 (a pair of second electrodes) of the parallel resonators P1 to P3 are drawn out from the resonance region 50 in a direction perpendicular to the X-axis direction of the crystal orientation of the piezoelectric layer 14. As a result, the series resonators S1 to S4 have a larger Q value at the resonant frequency, and the parallel resonators P1 to P3 have a larger Q value at the anti-resonant frequency, thereby improving the pass-through characteristics of the filter. The direction obtained by rotating the +Z axis direction of the crystal orientation of the piezoelectric layer 14 by approximately 105° in the +Y axis direction is within the range of 105° ± 5°, preferably within the range of 105° ± 3°, and more preferably within the range of 105° ± 1°. The direction perpendicular to the X axis direction of the crystal orientation of the piezoelectric layer 14 includes not only cases where it is perfectly perpendicular, but also cases where it is within ±5° from the direction perpendicular to the X axis direction, and may also be within the range of ±3° or ±1°. Similarly, the direction in the same direction as the X axis direction of the crystal orientation of the piezoelectric layer 14 includes not only cases where it is exactly the same, but also cases where it is within ±5° from the X axis direction, and may also be within the range of ±3° or ±1°.

[0050] For series resonators S1 to S4, the length L1 (see Figure 10(a)) of the lower electrode 12 and upper electrode 16 drawn linearly from the resonant region 50 in the same direction as the X-axis direction of the crystal orientation of the piezoelectric layer 14 is preferably 0.75 times (0.375λ) or more the thickness of the piezoelectric layer 14 in the resonant region 50. Similarly, for parallel resonators P1 to P3, the length L2 (see Figure 10(b)) of the lower electrode 12 and upper electrode 16 drawn linearly from the resonant region 50 in a direction perpendicular to the X-axis direction of the crystal orientation of the piezoelectric layer 14 is preferably 0.75 times (0.375λ) or more the thickness of the piezoelectric layer 14 in the resonant region 50. This reduces spurious emissions, as shown in Figure 7. Note that since Figure 7 shows the simulation results regarding the interference of elastic wave leakage between adjacent resonators, it is considered that similar results can be obtained regardless of the crystal orientation of the piezoelectric layer 14. From the viewpoint of reducing spurious emissions, the length L1 of the lower electrode 12 and upper electrode 16 of the series resonators S1 to S4, linearly extended from the resonance region 50, is preferably 0.8 times or more the thickness of the piezoelectric layer 14 in the resonance region 50, more preferably 0.9 times or more, and even more preferably 1.0 times or more. Similarly, the length L2 of the lower electrode 12 and upper electrode 16 of the parallel resonators P1 to P3, linearly extended from the resonance region 50, is preferably 0.8 times or more the thickness of the piezoelectric layer 14 in the resonance region 50, more preferably 0.9 times or more, and even more preferably 1.0 times or more.

[0051] In Example 1, as shown in Figure 9(a), the series resonators S1 to S4 are arranged in the same direction as the direction in which the lower electrodes 12 and upper electrodes 16 of the series resonators S1 to S4 are drawn out from the resonance region 50. This arrangement suppresses the complexity of the lower wiring 22a, 22b and the upper wiring 26a, 26b. Arranging in the same direction means that the series resonators S1 to S4 are arranged within a range of ±10° from the direction in which the lower electrodes 12 and upper electrodes 16 of the series resonators S1 to S4 are drawn out from the resonance region 50. When the series resonators S1 to S4 are arranged in the same direction as the direction in which the lower electrodes 12 and upper electrodes 16 are drawn out, it is preferable that the series resonator S1 is connected to the input terminal Tin by an upper wiring 26a (first wiring) that widens as it moves away from the upper electrode 16, and the series resonator S4 is connected to the output terminal Tout by an upper wiring 26a (first wiring) that widens as it moves away from the upper electrode 16. This allows for larger input terminal Tin and output terminal Tout, and reduces the electrical resistance between the input terminal Tin and output terminal Tout and the series resonators S1 to S4. Furthermore, it is preferable that the parallel resonators P1 to P3 are connected to the lower wiring 22a or upper wiring 26a (first wiring) by the lower wiring 22b or upper wiring 26b (second wiring), which narrows in width as it moves away from the lower electrode 12 or upper electrode 16. This allows for miniaturization of the filter 500.

[0052] In a modified example of Embodiment 1, as shown in Figure 11, the series resonators S1 to S4 are arranged in a direction perpendicular to the direction in which the lower electrodes 12 and upper electrodes 16 of the series resonators S1 to S4 are drawn out from the resonance region 50. Being arranged in a perpendicular direction means that the series resonators S1 to S4 are arranged within a range of ±10° from the direction perpendicular to the direction in which the lower electrodes 12 and upper electrodes 16 of the series resonators S1 to S4 are drawn out from the resonance region 50. Series resonator S1 is connected to the input terminal Tin by an upper wiring 26a (first wiring) drawn out from the upper electrode 16 in a direction intersecting the direction in which the lower electrodes 12 and upper electrodes 16 are drawn out from the resonance region 50. Series resonator S4 is connected to the output terminal Tout by an upper wiring 26a (first wiring) drawn out from the upper electrode 16 in a direction intersecting the direction in which the lower electrodes 12 and upper electrodes 16 are drawn out from the resonance region 50. The parallel resonators P1 to P3 are connected to the ground terminal Tg by lower wiring 22b or upper wiring 26b (second wiring) drawn from the lower electrode 12 or upper electrode 16 in a direction that intersects the direction in which the lower electrode 12 and upper electrode 16 are drawn from the resonant region 50. This allows the input terminal Tin, output terminal Tout, and ground terminal Tg to be placed in appropriate positions, and also allows the filter 510 to be miniaturized.

[0053] In the series resonators S1 to S4 and parallel resonators P1 to P3, it is preferable that the resonance region 50 is formed when the upper electrode 16 and the lower electrode 12, which has a width wider than the upper electrode 16 in the direction perpendicular to the direction in which the upper electrode 16 is drawn out of the resonance region 50, face each other across the piezoelectric layer 14, as shown in Figure 1(a). This suppresses changes in the size and shape of the resonance region 50 even when the lower electrode 12 and the upper electrode 16 are formed misaligned from predetermined positions. From the viewpoint of misalignment, the difference D in width between the lower electrode 12 and the upper electrode 16 is preferably 0.5 μm or more, more preferably 0.7 μm or more, and even more preferably 0.9 μm or more. On the other hand, from the viewpoint of miniaturization, it is preferably 1.5 μm or less, more preferably 1.3 μm or less, and even more preferably 1 μm or less. Note that it is not limited to the case where the width of the lower electrode 12 is greater than the width of the upper electrode 16; the case where the width of the upper electrode 16 is greater than the width of the lower electrode 12 is also acceptable.

[0054] As shown in Figures 9(a) and 9(b), from the viewpoint of ease of manufacturing and miniaturization of the filter, it is preferable that the piezoelectric layers of the series resonators S1 to S4 and the piezoelectric layers of the parallel resonators P1 to P3 are a continuous single piezoelectric layer 14.

[0055] [Modified examples of piezoelectric thin-film resonators] Figure 12 is a cross-sectional view of a modified piezoelectric thin-film resonator 110. As shown in Figure 12, in the piezoelectric thin-film resonator 110, instead of providing an acoustic reflective film 31 on the substrate 10, a recess is formed in the substrate 10, and an air gap 30 is provided between the substrate 10 and the lower electrode 12. The other configurations are the same as those of the piezoelectric thin-film resonator 100 in Figures 1(a) and 1(b), so their explanation is omitted.

[0056] The piezoelectric thin-film resonator used in the filter of Example 1 and its modified form may be an SMR (Solid Mounted Resonator) having an acoustic reflective film 31 overlapping the resonance region 50, as shown in Figures 1(a) and 1(b). Alternatively, it may be an FBAR (Film Bulk Acoustic Resonator) having an air gap 30 overlapping the resonance region 50, as shown in Figure 12.

[0057] The example shown is a roughly rectangular planar shape of the resonance region 50, but other shapes are also possible. Figures 13(a) to 13(c) are planar views showing other examples of the resonance region 50. In Figures 13(a) to 13(c), the vibration direction 60 of the thickness shear vibration is indicated by an arrow, a piezoelectric thin film resonator used in a series resonator is shown on the left, and a piezoelectric thin film resonator used in a parallel resonator is shown on the right. As shown in Figure 13(a), the planar shape of the resonance region 50 may be a roughly polygonal shape such as a roughly pentagon. As shown in Figure 13(b), the planar shape of the resonance region 50 may be a roughly elliptical shape. As shown in Figure 13(c), the planar shape of the resonance region 50 may be a roughly circular shape.

[0058] Figures 14(a) to 14(c) are plan views showing examples of lower wiring 22a, 22b and upper wiring 26a, 26b. In Figures 14(a) to 14(c), the vibration direction 60 of thickness shear vibration is indicated by an arrow, with a piezoelectric thin film resonator used in a series resonator shown on the left and a piezoelectric thin film resonator used in a parallel resonator shown on the right. As shown in Figure 14(a), at least one of the lower wiring 22a connected to the lower electrode 12 and the upper wiring 26a connected to the upper electrode 16 of the series resonator may have a width that increases or decreases as it moves away from the lower electrode 12 or the upper electrode 16. Similarly, at least one of the lower wiring 22b connected to the lower electrode 12 and the upper wiring 26b connected to the upper electrode 16 of the parallel resonator may have a width that increases or decreases as it moves away from the lower electrode 12 or the upper electrode 16.

[0059] As shown in Figure 14(b), at least one of the lower wiring 22a connected to the lower electrode 12 and the upper wiring 26a connected to the upper electrode 16 of a series resonator may be drawn out from the lower electrode 12 or the upper electrode 16 in a direction that intersects the direction in which the lower electrode 12 and the upper electrode 16 are drawn out from the resonant region 50. Similarly, at least one of the lower wiring 22b connected to the lower electrode 12 and the upper wiring 26b connected to the upper electrode 16 of a parallel resonator may be drawn out from the lower electrode 12 or the upper electrode 16 in a direction that intersects the direction in which the lower electrode 12 and the upper electrode 16 are drawn out from the resonant region 50.

[0060] As shown in Figure 14(c), at least one of the lower wiring 22a connected to the lower electrode 12 and the upper wiring 26a connected to the upper electrode 16 of a series resonator may be drawn out from the lower electrode 12 or the upper electrode 16 with a constant width narrower than the lower electrode 12 and the upper electrode 16. Similarly, at least one of the lower wiring 22b connected to the lower electrode 12 and the upper wiring 26b connected to the upper electrode 16 of a parallel resonator may be drawn out from the lower electrode 12 or the upper electrode 16 with a constant width narrower than the lower electrode 12 and the upper electrode 16.

[0061] By routing the lower wiring 22a, 22b and upper wiring 26a, 26b as shown in Figures 14(a) to 14(c), the flexibility of wiring is improved, and the input terminal Tin, output terminal Tout, and ground terminal Tg can be placed in appropriate positions.

[0062] In Example 1, the case where the piezoelectric layer 14 is a single-crystal lithium niobate layer was shown as an example, but it is not limited to this case. The piezoelectric layer 14 may also be a single-crystal lithium tantalate layer. Even when the piezoelectric layer 14 is a single-crystal lithium tantalate layer, the vibration direction 60 of the thickness-slip vibration is the same when the crystal orientation is the same as when the piezoelectric layer 14 is a single-crystal lithium niobate layer. That is, even when the piezoelectric layer 14 is a single-crystal lithium tantalate layer, as in Figures 3(a) to 3(c), the X direction is the vibration direction 60 of the thickness-slip vibration when the Euler angles are (90°, 105°, 0°). As in Figures 4(a) and 4(b), the Y direction is the vibration direction 60 of the thickness-slip vibration when the Euler angles are (0°, 105°, 0°).

[0063] Therefore, even when the piezoelectric layer 14 is a single-crystal lithium tantalate layer, if the X-axis direction of the crystal orientation is in the planar direction and the thickness direction is in the direction where the +Z-axis direction of the crystal orientation is rotated approximately 105° in the +Y-axis direction, the vibration direction 60 of the thickness shear vibration will be perpendicular to the X-axis direction of the crystal orientation of the piezoelectric layer 14. Thus, even when the piezoelectric layer 14 is a single-crystal lithium tantalate layer, the lower electrodes 12 and upper electrodes 16 (a pair of first electrodes) of the series resonators S1 to S4 are drawn out of the resonance region 50 in the same direction as the X-axis direction of the crystal orientation of the piezoelectric layer 14, just as in the case of a single-crystal lithium niobate layer. The lower electrodes 12 and upper electrodes 16 (a pair of second electrodes) of the parallel resonators P1 to P3 are drawn out of the resonance region 50 in a direction perpendicular to the X-axis direction of the crystal orientation of the piezoelectric layer 14. As a result, the Q-factor at the resonance frequency becomes larger for the series resonators S1 to S4, and the Q-factor at the anti-resonance frequency becomes larger for the parallel resonators P1 to P3, thereby improving the pass-through characteristics of the filter. Furthermore, since lithium tantalate and lithium niobate have similar crystal structures, it is expected that the same effect can be obtained when a lithium tantalate layer is used in the piezoelectric layer 14 as when a lithium niobate layer is used. [Example 2]

[0064] Example 2 describes the case where the piezoelectric layer 14 is a single-crystal lithium tantalate layer having a different crystal orientation than in Example 1. The plan view and cross-sectional view of the filter according to Example 2 are the same as those in Figures 9(a) and 9(b) of Example 1, so their description is omitted.

[0065] Figures 15(a) to 15(c) are perspective views showing the crystal orientation of the piezoelectric layer 14 when the piezoelectric layer 14 is a single-crystal lithium tantalate layer. As shown in Figure 15(a), the +X direction, +Y direction, and +Z direction are the +X axis direction, +Y axis direction, and +Z axis direction of the crystal orientation of the piezoelectric layer 14, respectively. As shown in Figure 15(b), from the state in Figure 15(a), the +X axis direction and +Y axis direction are rotated by 132° from the +X axis direction to the -Y axis direction on the X-Y axis plane, centered on the Z axis direction. Next, as shown in Figure 15(c), the +Y axis direction and +Z axis direction are rotated by 90° from the +Y axis direction to the +Z axis direction, centered on the X axis direction, and then the +X axis direction and +Y axis direction are rotated by 90° from the +X axis direction to the +Y axis direction, centered on the Z axis direction. When rotated in this way, the +Z direction becomes the +X axis direction, and the +X direction becomes the direction obtained by rotating the +Y axis direction by 42° in the -Z axis direction. In this case, the X direction becomes the vibration direction 60 of the thickness shear vibration. That is, the direction in which the +Y axis of the crystal orientation of the piezoelectric layer 14 is rotated 42° in the -Z axis direction becomes the vibration direction 60 of the thickness shear vibration. In Euler angles, this is (-132°, 90°, 90°).

[0066] Figure 16(a) is a perspective view of the series resonator in the filter according to Example 2, and Figure 16(b) is a perspective view of the parallel resonator. As shown in Figures 16(a) and 16(b), the vibration direction 60 of the thickness shear vibration is the direction obtained by rotating the +Y axis direction of the crystal orientation of the piezoelectric layer 14 by 42° in the -Z axis direction, which is approximately the X direction. For example, the Euler angles of the piezoelectric layer 14 are (-132°±5°, 90°±5°, 90°±5°).

[0067] As shown in Figure 16(a), the lower electrodes 12 and upper electrodes 16 of the series resonators S1 to S4 are drawn out of the resonance region 50 in a direction perpendicular to the direction obtained by rotating the +Y axis direction of the crystal orientation of the piezoelectric layer 14 by 42° in the -Z axis direction (for example, the Y direction). In other words, the lower electrodes 12 and upper electrodes 16 of the series resonators S1 to S4 are drawn out of the resonance region 50 in a direction perpendicular to the vibration direction 60 of the thickness shear vibration. As shown in Figure 16(b), the lower electrodes 12 and upper electrodes 16 of the parallel resonators P1 to P3 are drawn out of the resonance region 50 in the same direction (for example, the X direction) as the direction obtained by rotating the +Y axis direction of the crystal orientation of the piezoelectric layer 14 by 42° in the -Z axis direction. In other words, the lower electrodes 12 and upper electrodes 16 of the parallel resonators P1 to P3 are drawn out of the resonance region 50 in the same direction as the vibration direction 60 of the thickness shear vibration.

[0068] According to Example 2, as shown in Figures 16(a) and 16(b), the piezoelectric layer 14 is a single-crystal lithium tantalate layer, where the X-axis direction of the crystal orientation is the thickness direction and the Y-axis and Z-axis directions of the crystal orientation are planar. In this case, the vibration direction 60 of the thickness shear vibration is the direction obtained by rotating the +Y-axis direction of the crystal orientation of the piezoelectric layer 14 by approximately 42° in the -Z-axis direction. The direction rotated by approximately 42° is within the range of 42°±5°, preferably within the range of 42°±3°, and more preferably within the range of 42°±1°. As shown in Figure 16(a), the lower electrode 12 and upper electrode 16 (a pair of first electrodes) of the series resonators S1 to S4 are drawn out from the resonance region 50 in a direction perpendicular to the direction obtained by rotating the +Y-axis direction of the crystal orientation of the piezoelectric layer 14 by 42° in the -Z-axis direction. As shown in Figure 16(b), the lower electrodes 12 and upper electrodes 16 (a pair of second electrodes) of the parallel resonators P1 to P3 are drawn out from the resonance region 50 in the same direction as the direction obtained by rotating the +Y axis direction of the crystal orientation of the piezoelectric layer 14 by 42° in the -Z axis direction. As a result, the series resonators S1 to S4 have a larger Q value at the resonance frequency, and the parallel resonators P1 to P3 have a larger Q value at the anti-resonance frequency, thereby improving the pass characteristics of the filter. Since lithium tantalate and lithium niobate have similar crystal structures, it is thought that the same effect can be obtained when a lithium tantalate layer is used for the piezoelectric layer 14 as when a lithium niobate layer is used. The direction perpendicular to the direction obtained by rotating the +Y axis direction of the crystal orientation of the piezoelectric layer 14 by 42° in the -Z axis direction includes not only cases where it is perfectly perpendicular, but also cases within ±5° of the direction perpendicular to the direction of the 42° rotation, and may also be within a range of ±3° or ±1°. Similarly, the direction obtained by rotating the +Y axis direction of the crystal orientation of the piezoelectric layer 14 by 42° in the -Z axis direction includes not only cases where it is exactly the same, but also cases where it is within ±5° of the direction rotated by 42°, and may also be within ±3° or ±1°.

[0069] In Example 2, as shown in Figure 9(a) of Example 1, the series resonators S1 to S4 may be arranged in a direction perpendicular to the vibration direction 60 of the thickness shear vibration, or, as shown in Figure 11 of the modified example of Example 1, the series resonators S1 to S4 may be arranged in the same direction as the vibration direction 60 of the thickness shear vibration. In Example 2, the series resonators S1 to S4 and the parallel resonators P1 to P3 may be SMRs or FBARs.

[0070] Furthermore, according to Example 1, a modified example of Example 1, and Example 2, the lower electrodes 12 and upper electrodes 16 of the series resonators S1 to S4 are drawn out from the resonance region 50 in a direction perpendicular to the vibration direction 60 of the thickness shear vibration excited by the piezoelectric layer 14. The lower electrodes 12 and upper electrodes 16 of the parallel resonators P1 to P3 are drawn out from the resonance region 50 in the same direction as the vibration direction 60 of the thickness shear vibration excited by the piezoelectric layer 14. As a result, the Q value at the resonance frequency increases for the series resonators S1 to S4, and the Q value at the anti-resonance frequency increases for the parallel resonators P1 to P3, thereby improving the pass-through characteristics of the filter. The direction perpendicular to the vibration direction 60 of the thickness shear vibration includes not only cases where it is perfectly perpendicular, but also cases within ±5° of the direction perpendicular to the vibration direction 60 of the thickness shear vibration, and may also be within a range of ±3° or ±1°. Similarly, "same direction as the vibration direction 60 of the thickness shear vibration" includes not only cases where it is exactly the same, but also cases where it is within ±5° of the vibration direction 60 of the thickness shear vibration, and may also be within ±3° or ±1°.

[0071] In Example 1, a modified example of Example 1, and Example 2, the case in which the lower electrode 12 and upper electrode 16 are drawn out of the resonance region 50 in a direction perpendicular to the vibration direction 60 of the thickness shear vibration is shown as an example. However, the example is not limited to this case, and in at least one of the series resonators S1 to S4, the lower electrode 12 and upper electrode 16 may be drawn out of the resonance region 50 in a direction perpendicular to the vibration direction 60 of the thickness shear vibration. Similarly, the case in which the lower electrode 12 and upper electrode 16 are drawn out of the resonance region 50 in the same direction as the vibration direction 60 of the thickness shear vibration is shown as an example, and in which the lower electrode 12 and upper electrode 16 are drawn out of the resonance region 50 in the same direction as the vibration direction 60 of the thickness shear vibration is shown as an example. However, the example is not limited to this case, and in at least one of the parallel resonators P1 to P3, the lower electrode 12 and upper electrode 16 may be drawn out of the resonance region 50 in the same direction as the vibration direction 60 of the thickness shear vibration. [Example 3]

[0072] Figure 17 is a block diagram of the duplexer 600 according to Embodiment 3. As shown in Figure 17, the duplexer 600 has a transmit filter 40 connected between the common terminal Ant and the transmit terminal Tx, and a receive filter 42 connected between the common terminal Ant and the receive terminal Rx. The transmit filter 40 allows signals in the transmit band from the signal input from the transmit terminal Tx to pass to the common terminal Ant as the transmit signal, and suppresses signals of other frequencies. The receive filter 42 allows signals in the receive band from the signal input from the common terminal Ant to pass to the receive terminal Rx as the received signal, and suppresses signals of other frequencies. At least one of the transmit filter 40 and the receive filter 42 can be the filter of Embodiment 1, a modified example of Embodiment 1, and Embodiment 2. Although a duplexer is shown as an example of a multiplexer, a triplexer or quadplexer may also be used.

[0073] Although embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of Symbols]

[0074] 10 circuit boards 12 Lower electrode 14 Piezoelectric layer 16, 16a, 16b upper electrode 22a, 22b Lower wiring 26a, 26b Upper wiring 30 void 31 Acoustic reflective film 40 Transmission Filters 42 Receiving Filter 50 resonance area 60 Vibration direction 100, 110 Piezoelectric Thin Film Resonators 500, 510 filters 600 Duplexa Tin input terminal Tout output terminal Tg Ground terminal S1~S4 series resonator P1~P3 parallel resonator

Claims

1. circuit board and A series resonator comprising: a first piezoelectric layer provided on the substrate and connected in series between an input terminal and an output terminal, wherein the first piezoelectric layer is a single-crystal lithium niobate layer or a single-crystal lithium tantalate layer whose X-axis direction of crystal orientation is planar and whose thickness direction is rotated approximately 105° in the +Y-axis direction from the +Z-axis direction of crystal orientation; and a pair of first electrodes that form a first resonant region opposite each other across the first piezoelectric layer and are drawn out from the first resonant region in the same first direction as the X-axis direction of the crystal orientation of the first piezoelectric layer; A filter comprising: a parallel resonator provided on the substrate and connected in parallel between the input terminal and the output terminal, comprising: a second piezoelectric layer which is a single-crystal lithium niobate layer or a single-crystal lithium tantalate layer whose X-axis direction of crystal orientation is in the planar direction and whose thickness direction is in the direction obtained by rotating the +Z-axis direction of crystal orientation by approximately 105° in the +Y-axis direction; and a pair of second electrodes which form a second resonant region opposite to the second piezoelectric layer on either side of the second piezoelectric layer and are drawn out from the second resonant region in a second direction perpendicular to the X-axis direction of the crystal orientation of the second piezoelectric layer.

2. circuit board and A series resonator comprising: a first piezoelectric layer provided on the substrate and connected in series between an input terminal and an output terminal, wherein the first piezoelectric layer is a single-crystal lithium tantalate layer whose X-axis direction of crystal orientation is in the thickness direction and whose Y-axis and Z-axis directions of crystal orientation are in the planar direction; and a pair of first electrodes that form a first resonant region opposite to the first piezoelectric layer, and are drawn out from the first resonant region in a first direction perpendicular to the direction obtained by rotating the +Y-axis direction of the crystal orientation of the first piezoelectric layer by 42° in the -Z-axis direction; A filter comprising: a parallel resonator provided on the substrate and connected in parallel between the input terminal and the output terminal, comprising: a second piezoelectric layer which is a single-crystal lithium tantalate layer in which the X-axis direction of the crystal orientation is in the thickness direction and the Y-axis and Z-axis directions of the crystal orientation are in the planar direction; and a pair of second electrodes which form a second resonant region opposite each other across the second piezoelectric layer and are drawn out from the second resonant region in the same second direction as the direction in which the +Y-axis direction of the crystal orientation of the second piezoelectric layer is rotated by 42° in the -Z-axis direction.

3. circuit board and A series resonator provided on the substrate and connected in series between an input terminal and an output terminal, comprising: a first piezoelectric layer; a pair of first electrodes that form a first resonant region opposite to the first piezoelectric layer, excite the first piezoelectric layer with thickness-slip vibrations, and are drawn out from the first resonant region in a first direction perpendicular to the vibration direction of the thickness-slip vibrations excited by the first piezoelectric layer; A filter comprising: a parallel resonator provided on the substrate and connected in parallel between the input terminal and the output terminal, comprising: a second piezoelectric layer; and a pair of second electrodes that form a second resonant region opposite to the second piezoelectric layer, excite the second piezoelectric layer with thickness-slip vibrations, and are drawn out from the second resonant region in the same second direction as the vibration direction of the thickness-slip vibrations excited by the second piezoelectric layer.

4. The pair of first electrodes are drawn linearly from the first resonant region in the first direction with a length of 0.75 times or more the thickness of the first piezoelectric layer in the first resonant region. The filter according to any one of claims 1 to 3, wherein the pair of second electrodes are drawn linearly in the second direction from the second resonant region with a length of 0.75 times or more the thickness of the second piezoelectric layer in the second resonant region.

5. A first wiring connected to the end of the pair of first electrodes opposite to the first resonant region, The pair of second electrodes comprises a second wiring connected to the end opposite to the second resonant region of the pair of second electrodes, The filter according to claim 4, wherein the length of the first wiring changes in a direction perpendicular to the first direction as it moves away from the pair of first electrodes and / or the length of the second wiring changes in a direction perpendicular to the second direction as it moves away from the pair of second electrodes.

6. The series resonators are arranged in the same direction as the first direction, The filter according to claim 5, wherein the first series resonator and the second series resonator among the plurality of series resonators are connected to the input terminal and the output terminal, respectively, by first wiring, the length of which increases in a direction perpendicular to the first direction as it moves away from the pair of first electrodes.

7. The filter according to claim 6, wherein the parallel resonators are connected to the first wiring between the plurality of series resonators by the second wiring, the length of which decreases in a direction perpendicular to the second direction as it moves away from the pair of second electrodes.

8. A first wiring connected to the end of the pair of first electrodes opposite to the first resonant region, The pair of second electrodes comprises a second wiring connected to the end opposite to the second resonant region of the pair of second electrodes, The filter according to claim 4, wherein the first wiring is drawn from the pair of first electrodes in a direction intersecting the first direction and / or the second wiring is drawn from the pair of second electrodes in a direction intersecting the second direction.

9. The series resonators are arranged in a line perpendicular to the first direction, Of the plurality of series resonators, the first series resonator and the second series resonator are connected to the input terminal and the output terminal, respectively, by the first wiring drawn out from the pair of first electrodes in a direction intersecting the first direction. The filter according to claim 8, wherein the parallel resonator is connected to the ground terminal by the second wiring drawn out from the pair of second electrodes in a direction intersecting the second direction.

10. The filter according to any one of claims 1 to 3, wherein the first piezoelectric layer and the second piezoelectric layer are a continuous single piezoelectric layer.

11. A multiplexer comprising the filter according to any one of claims 1 to 3.

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