Elastic wave device, filter and multiplexer

Abstract

To provide an elastic wave device that can be miniaturized.SOLUTION: An elastic wave device comprises a substrate 10, a lower electrode 12 provided on the substrate, a piezoelectric film 14 on the lower electrode, a first upper electrode 16a provided on the piezoelectric film to form a resonance region 50 where the lower electrode and the first upper electrode overlap across at least a portion of the piezoelectric film, viewed from the thickness direction of the piezoelectric film, an insulating film 20 provided on the lower electrode from the periphery 52 of the resonance region to an outer region 56 surrounding the resonance region, and a second upper electrode 16b provided in the outer region to form a region 58 where the lower electrode and the second upper electrode overlap by sandwiching at least a part of the insulating film without sandwiching the piezoelectric film, viewed from the thickness direction.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an elastic wave device, a filter, and a multiplexer.

Background Art

[0002] Filters and multiplexers having piezoelectric thin film resonators are used for high-frequency circuits of wireless terminals such as mobile phones. It is known to provide a capacitor connected in parallel to the piezoelectric thin film resonator on a substrate (for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] By forming a piezoelectric thin film resonator and a capacitor on a substrate, it is possible to reduce the manufacturing process and miniaturize compared to the case where the capacitor is provided as a separate component. However, even when forming a piezoelectric thin film resonator and a capacitor on a substrate, further miniaturization is required.

[0005] The present invention has been made in view of the above problems, and an object thereof is to miniaturize.

Means for Solving the Problems

[0006] The present invention relates to an elastic wave device including a substrate, a lower electrode provided on the substrate, a piezoelectric film provided on the lower electrode, a first upper electrode provided on the piezoelectric film so as to form a resonance region in which at least a part of the piezoelectric film is sandwiched in the thickness direction of the piezoelectric film and the lower electrode and the first upper electrode overlap, an insulating film provided on the lower electrode from the peripheral portion of the resonance region to an external region surrounding the resonance region, and a second upper electrode provided in the external region so as to form a region in which at least a part of the insulating film is sandwiched without sandwiching the piezoelectric film in the thickness direction and the lower electrode and the second upper electrode overlap.

[0007] In the above configuration, the first upper electrode and the second upper electrode can be integrally provided.

[0008] In the above configuration, the overlapping region can be provided between a lead-out region where the lower electrode is led out from the resonance region and the resonance region in the external region.

[0009] In the above configuration, the first upper electrode and the second upper electrode can be connected between the lead-out region and the resonance region.

[0010] In the above configuration, the region where the first upper electrode and the second upper electrode are connected can be provided in a part of the region where the overlapping region surrounds the resonance region and not provided in the remaining part of the surrounding region.

[0011] In the above configuration, the first upper electrode and the second upper electrode can be configured not to be electrically connected.

[0012] In the above configuration, the overlapping region can be provided in a part of the region where the lower electrode surrounds the resonance region and not provided in the remaining part of the surrounding region.

[0013] In the above configuration, in the resonance region, the insulating film can be provided between the lower electrode and the piezoelectric film.

[0014] In the above configuration, the insulating film is not provided at the central portion of the resonance region, and can be configured to be provided so as to surround at least a part of the central portion.

[0015] In the above configuration, a gap is provided between the substrate and the lower electrode, and the resonance region and the overlapping region can be configured to overlap the gap when viewed from the thickness direction.

[0016] The present invention is a filter including the above elastic wave device.

[0017] The present invention is a multiplexer including the above filter.

Advantages of the Invention

[0018] According to the present invention, miniaturization can be achieved.

Brief Description of the Drawings

[0019]

Figure 1

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BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Hereinafter, examples will be described with reference to the drawings.

EXAMPLE

[0021] Example 1 is an example in which a piezoelectric thin film resonator and a capacitor are connected in parallel as an elastic wave device. FIG. 1 is a plan view of the elastic wave device according to Example 1. FIGS. 2(a) to 2(c) are a cross-sectional view taken along line A-A, a cross-sectional view taken along line B-B, and a cross-sectional view taken along line C-C of FIG. 1, respectively. The thickness direction of the substrate 10 is defined as the Z direction, the direction in which the lower electrode 12 is drawn out from the resonance region 50 is defined as the X direction, and the direction orthogonal to the X direction in the plane direction of the substrate 10 is defined as the Y direction.

[0022] As shown in FIGS. 1 to 2(c), in the elastic wave device 100 of Example 1, a lower electrode 12 is provided on a substrate 10 with a gap 30 therebetween. The gap 30 has a dome shape. In the gap 30, the central height is higher than the surrounding. An insulating film 20 is provided on the lower electrode 12. A piezoelectric film 14 is provided on the lower electrode 12 and the insulating film 20. An upper electrode 16a is provided on the piezoelectric film 14. An upper electrode 16b is provided on the insulating film 20. The upper electrode 16c electrically connects the upper electrodes 16a and 16b. A protective film 24 is provided on the substrate 10 so as to cover the lower electrode 12, the insulating film 20, the piezoelectric film 14, and the upper electrodes 16a and 16b.

[0023] The resonance region 50 is defined by a region where at least a part of the piezoelectric film 14 is sandwiched when viewed from the Z direction and the lower electrode 12 and the upper electrode 16a overlap. The capacitor region 58 is defined by a region where at least a part of the insulating film 20 is sandwiched and the lower electrode 12 and the upper electrode 16b overlap without sandwiching the piezoelectric film 14. The piezoelectric thin film resonator 70 includes the resonance region 50, and the capacitor 72 includes the capacitor region 58. Elastic waves such as thickness longitudinal vibration mode or thickness shear vibration resonate in the piezoelectric film 14 in the resonance region 50. The resonance region 50 has a central portion 54 and a peripheral portion 52 that surrounds the central portion 54 and includes the outer periphery of the resonance region 50. An external region 56 is provided so as to surround the resonance region 50. The insulating film 20 is provided in the peripheral portion 52 and the external region 56 and is not provided in the central portion 54.

[0024] The region where the lower electrode 12 is drawn out from the resonance region 50 and the capacitor region 58 is the extraction region 60. The region where the upper electrode 16a is drawn out from the resonance region 50 is the extraction region 62. A metal layer 22a is provided on the lower electrode 12 in the extraction region 60. A metal layer 22b is provided on the upper electrode 16a in the extraction region 62. The metal layers 22a and 22b function as wirings or pads.

[0025] The capacitor region 58 is provided in a partial region 65 of the external region 56 surrounding the resonance region 50. The region 65 includes the area between the resonance region 50 and the extraction region 60. The upper electrodes 16a and 16b are electrically connected via the upper electrode 16c in a partial region 64 of the region 65. The upper electrode 16c is provided on the side surface of the piezoelectric film 14.

[0026] The substrate 10 is an insulating substrate or a semiconductor substrate such as a silicon substrate, a sapphire substrate, a spinel substrate, an alumina substrate, a quartz substrate, a glass substrate, a ceramic substrate, or a GaAs substrate. The lower electrode 12 and the upper electrodes 16a to 16c are single-layer films mainly composed of, for example, ruthenium (Ru), chromium (Cr), aluminum (Al), titanium (Ti), copper (Cu), silver (Ag), gold (Au), molybdenum (Mo), tungsten (W), tantalum (Ta), platinum (Pt), rhodium (Rh), or iridium (Ir), or laminated films thereof.

[0027] The piezoelectric film 14 is aluminum nitride (AlN), zinc oxide (ZnO), lead zirconate titanate (PZT), lead titanate (PbTiO3), lithium tantalate (TaLiO3), lithium niobate (NbLiO3), or quartz. The piezoelectric film 14 mainly contains, for example, aluminum nitride and may contain other elements for improving resonance characteristics or piezoelectricity. For example, by using scandium (Sc), two elements of a Group 2 element and a Group 4 element, or two elements of a Group 2 element and a Group 5 element as additive elements, the piezoelectricity of the piezoelectric film 14 is improved. Therefore, the effective electromechanical coupling coefficient of the piezoelectric thin film resonator can be improved. The Group 2 element is, for example, calcium (Ca), magnesium (Mg), strontium (Sr), or zinc (Zn). The Group 4 element is, for example, titanium, zirconium (Zr), or hafnium (Hf). The Group 5 element is, for example, tantalum, niobium (Nb), or vanadium (V). Further, the piezoelectric film 14 may contain boron (B) with aluminum nitride as the main component.

[0028] The insulating film 20 is an inorganic insulating film such as silicon oxide, silicon nitride, or aluminum oxide that contains impurities such as fluorine or does not contain impurities. The Young's modulus of the insulating film 20 is, for example, smaller than that of the piezoelectric film 14. The sign of the temperature coefficient of the elastic constant of the insulating film 20 is, for example, opposite to the sign of the temperature coefficient of the elastic constant of the piezoelectric film 14. The metal layer 22a is a metal with a low resistivity such as gold or copper. The protective film 24 is an inorganic insulating film such as silicon oxide, silicon nitride, or aluminum oxide.

[0029] In the case of a piezoelectric thin film resonator having a resonance frequency of 2 GHz, the lower electrode 12 is, for example, a chromium film with a thickness of 100 nm and a ruthenium film with a thickness of 250 nm from the substrate 10 side. The piezoelectric film 14 is, for example, aluminum nitride with a thickness of 11000 nm. The upper electrodes 16a and 16b are a ruthenium film with a thickness of 250 nm and a chromium film with a thickness of 50 nm from the piezoelectric film 14 side. The insulating film 20 is a silicon oxide film with a thickness of 100 nm. The film thickness of each layer can be appropriately set to obtain desired resonance characteristics.

[0030] [Manufacturing Method of Example 1] Figures 3(a) to 4(c) are cross-sectional views showing the manufacturing method of the piezoelectric thin film resonator according to Example 1. As shown in Figure 3(a), a sacrificial layer 32 is formed on the substrate 10. The sacrificial layer 32 is, for example, magnesium oxide (MgO), zinc oxide (ZnO), germanium (Ge), or silicon oxide (SiO2). The thickness of the sacrificial layer 32 is, for example, from 10 nm to 100 nm. The sacrificial layer 32 is patterned into a desired shape. The lower electrode 12 is formed on the substrate 10 and the sacrificial layer 32. The lower electrode 12 is patterned into a desired shape.

[0031] As shown in FIG. 3(b), an insulating film 20 is formed on the substrate 10 and the lower electrode 12. The insulating film 20 is patterned into a desired shape. A piezoelectric film 14 is formed on the substrate 10, the lower electrode 12, and the insulating film 20. The insulating film 20 is patterned into a desired shape. For the formation of the sacrificial layer 32, the lower electrode 12, the insulating film 20, and the piezoelectric film 14, for example, a sputtering method, a vacuum evaporation method, or a CVD (Chemical Vapor Deposition) method is used. For the patterning of the sacrificial layer 32, the lower electrode 12, the insulating film 20, and the piezoelectric film 14, for example, a photolithography method and an etching method are used.

[0032] As shown in FIG. 3(c), an upper electrode 16 is formed on the substrate 10, the lower electrode 12, the insulating film 20, and the piezoelectric film 14. The upper electrode 16 is formed, for example, by using a sputtering method over the entire surface on the substrate 10.

[0033] FIG. 4(a) includes the B-B cross section of FIG. 1, and FIG. 4(b) shows the C-C cross section of FIG. 1. As shown in FIGS. 4(a) and 4(b), the upper electrode 16 is patterned by using, for example, a photolithography method and an etching method. Thereby, an upper electrode 16a is formed on the piezoelectric film 14 in the resonance region 50, and an upper electrode 16b is formed on the insulating film 20 in the capacitor region 58. In FIG. 4(a), an upper electrode 16c is left on the side surface of the piezoelectric film 14. In FIG. 4(b), the upper electrode 16 is not left on the side surface of the piezoelectric film 14.

[0034] FIG. 4(c) includes the B-B cross section of FIG. 1. As shown in FIG. 4(c), a protective film 24 is formed on the substrate 10, the lower electrode 12, the insulating film 20, the piezoelectric film 14, and the upper electrode 16. The protective film 24 is formed by using, for example, a CVD method. A part of the protective film 24 on the lower electrode 12 and a part of the protective film 24 on the upper electrode 16a are removed to form openings. The formation of the openings in the protective film 24 uses, for example, a photolithography method and an etching method. Metal layers 22a and 22b that are electrically in contact with the lower electrode 12 and the upper electrode 16a are formed on the lower electrode 12 and the upper electrode 16a through the openings in the protective film 24.

[0035] Thereafter, the sacrificial layer 32 is removed using a medium (etching solution) for etching the sacrificial layer 32. When the sacrificial layer 32 is removed, a gap 30 is formed between the lower electrode 12 and the substrate 10. The gap 30 has a dome shape. Thus, the surface acoustic wave device 100 shown in FIGS. 1 to 2(c) is manufactured.

[0036] According to Example 1, the insulating film 20 is provided on the lower electrode 12 from the peripheral portion 52 of the resonance region 50 to the external region 56 outside the resonance region 50. The resonance region 50 is a region where at least a part of the piezoelectric film 14 is sandwiched when viewed from the Z direction, and the lower electrode 12 and the upper electrode 16a (first upper electrode) overlap. The capacitor region 58 (overlapping region) is a region in the external region 56 where at least a part of the insulating film 20 is sandwiched without sandwiching the piezoelectric film 14 when viewed from the Z direction, and the lower electrode 12 and the upper electrode 16b (second upper electrode) overlap.

[0037] In this way, by providing the insulating film 20 provided in the resonance region 50 of the piezoelectric thin film resonator 70 to the external region 56 and forming the upper electrode 16a on the insulating film 20, the capacitor 72 is formed. Thereby, the piezoelectric thin film resonator 70 and the capacitor 72 electrically connected via the lower electrode 12 can be formed in proximity to each other. Therefore, the surface acoustic wave device 100 can be miniaturized. Further, the insulating film 20 used for the piezoelectric thin film resonator 70 is used as the dielectric layer of the capacitor 72. Thereby, it is not necessary to separately form the dielectric layer of the capacitor 72, and the manufacturing process can be reduced.

[0038] The upper electrodes 16a and 16b are continuously provided integrally via the upper electrode 16c. Thereby, the upper electrodes 16a and 16b are electrically connected. Therefore, between the metal layers 22a and 22b, the capacitor 72 can be connected in parallel with the piezoelectric thin film resonator 70.

[0039] The capacitor region 58 is provided between the extraction region 60 and the resonance region 50 in the external region 56. Thereby, the electrical resistance between the capacitor 72 and the lower electrode 12 of the extraction region 60 can be reduced.

[0040] When a capacitor region 58 is provided so as to surround the resonance region 50, elastic waves of the piezoelectric film 14 leak through the upper electrode 16b of the capacitor region 58. As a result, the Q value of the piezoelectric thin film resonator 70 decreases and the loss increases. Therefore, it is preferable that the lower electrode 12 of the capacitor region 58 is provided in a partial region 65 of the region surrounding the resonance region 50 and is not provided in the remaining region 66 of the surrounding region. The length of the region 65 is preferably 80% or less, more preferably 50% or less, of the length of the region where the lower electrode 12 surrounds the resonance region 50.

[0041] The upper electrodes 16a and 16b are connected between the lead-out region 60 and the resonance region 50. Thereby, the electrical resistance between the capacitor 72 and the piezoelectric thin film resonator 70 can be reduced.

[0042] When the upper electrode 16c is provided on the side surface of the piezoelectric film 14, elastic waves of the piezoelectric film 14 leak through the upper electrode 16c. As a result, the Q value of the piezoelectric thin film resonator 70 decreases and the loss increases. Therefore, it is preferable that the region 64 where the upper electrodes 16a and 16b are connected is provided in a part of the region 65 where the capacitor region 58 surrounds the resonance region 50 and is not provided in the remaining part of the surrounding region 65. The length of the region 64 is preferably 80% or less, more preferably 50% or less, of the length of the region 65.

[0043] The insulating film 20 may be provided on the lower electrode 12. For example, the piezoelectric film 14 may have two laminated piezoelectric films, and the insulating film 20 may be provided between the two piezoelectric films in the resonance region 50. In the resonance region 50, the insulating film 20 may be provided between the piezoelectric film 14 and the upper electrode 16a. When the insulating film 20 covers at least a part of the side surface of the piezoelectric film 14, elastic waves are likely to leak from the resonance region 50 through the insulating film 20. Therefore, as in the first embodiment, in the resonance region 50, it is preferable to provide the insulating film 20 between the lower electrode 12 and the piezoelectric film 14.

[0044] The insulating film 20 only needs to be provided in at least a part of the resonance region 50. In the first embodiment, the insulating film 20 is not provided in the central portion 54 of the resonance region 50, but is provided so as to surround at least a part of the central portion 54. Thereby, leakage of elastic waves to the outside of the resonance region 50 can be suppressed, and loss can be suppressed.

[0045] The Young's modulus of the insulating film 20 is lower than that of the piezoelectric film 14. Thereby, leakage of elastic waves to the outside of the resonance region 50 can be further suppressed, and loss can be further suppressed. For example, the piezoelectric film 14 is mainly composed of aluminum nitride, and the insulating film 20 is mainly composed of silicon oxide. Thereby, the Young's modulus of the insulating film 20 can be made lower than that of the piezoelectric film 14.

[0046] When the insulating film 20 is used as a temperature compensation film, the sign of the temperature coefficient of the elastic constant of the insulating film 20 is opposite to the sign of the temperature coefficient of the elastic constant of the piezoelectric film 14. The insulating film 20 is also provided in the central portion 54. Thereby, the frequency temperature coefficient of the piezoelectric thin film resonator 70 can be reduced. For example, the piezoelectric film 14 is mainly composed of aluminum nitride, and the insulating film 20 is mainly composed of silicon oxide. Thereby, the signs of the temperature coefficients of the elastic constants of the insulating film 20 and the piezoelectric film 14 can be made opposite.

[0047] A gap 30 is provided between the substrate 10 and the lower electrode 12, and the resonance region 50 and the capacitor region 58 overlap the gap 30. Thereby, the elastic wave device can be miniaturized.

[0048] [Modification Example 1 of the First Embodiment] FIG. 5 is a plan view of an elastic wave device according to Modification Example 1 of the first embodiment. FIGS. 6(a) and 6(b) are cross-sectional views taken along line A-A and line B-B of FIG. 5, respectively.

[0049] As shown in FIGS. 5 to 6(b), in the elastic wave device 102 of Modification 1 of Example 1, the capacitor region 58 is provided in all regions 65 of the region where the lower electrode 12 surrounds the resonance region 50. The region 64 where the upper electrodes 16a and 16b are connected is provided in all of the regions 65 where the capacitor region 58 surrounds the resonance region 50. Other configurations are the same as those of Example 1 and the description thereof is omitted.

[0050] In Modification 1 of Example 1, although the leakage of elastic waves from the resonance region 50 is large, the area of the capacitor region 58 can be increased, so that the capacitance of the capacitor 72 can be increased.

Example

[0051] Example 2 is an example in which a piezoelectric thin film resonator and a capacitor are connected in series as an elastic wave device. FIG. 7 is a plan view of the elastic wave device according to Example 2. FIGS. 8(a) and 8(b) are cross-sectional views taken along line A-A and line B-B of FIG. 7, respectively.

[0052] As shown in FIGS. 7 to 8(b), in the elastic wave device 104 of Example 2, the upper electrodes 16a and 16b are not electrically connected. The metal layer 22a is not provided on the lower electrode 12, and the upper electrode 16b is provided in the extraction region 60. The metal layer 22a is provided on the upper electrode 16b in the extraction region 60. In the region where the lower electrode 12 surrounds the resonance region 50, the insulating film 20 is provided up to the outside of the lower electrode 12. The upper electrode 16b is provided outside the lower electrode 12. The lower electrode 12 and the upper electrode 16b are not electrically connected.

[0053] A capacitor region 58 is provided in an external region 56 between the resonance region 50 and the extraction region 60. In a region 65 where the capacitor region 58 is provided among the regions surrounding the resonance region 50 of the lower electrode 12, the upper electrode 16b is provided from the outside of the insulating film 20 up to the insulating film 20 of the region where the lower electrode 12 is provided. In the capacitor region 58, the lower electrode 12 and the upper electrode 16b overlap with each other with the insulating film 20 therebetween. In a region 66 other than the region 65 among the regions surrounding the resonance region 50 of the lower electrode 12, the upper electrode 16b is provided up to the insulating film 20 of the region where the lower electrode 12 is not provided, and is not provided on the insulating film 20 of the region where the lower electrode 12 is provided. As a result, the capacitor region 58 is not formed in the region 66. Other configurations are the same as those in the first embodiment and the description thereof is omitted.

[0054] [Manufacturing Method of Example 2] FIGS. 9(a) to 9(c) are cross-sectional views showing a manufacturing method of a piezoelectric thin film resonator according to the second embodiment. FIGS. 9(a) and 9(b) are cross-sectional views including the A-A cross-section of FIG. 7, and FIG. 9(c) is a cross-sectional view including the B-B cross-section of FIG. 7.

[0055] As shown in FIG. 9(a), similar to FIGS. 3(a) to 3(c) of the first embodiment, the upper electrode 16 is formed. As shown in FIGS. 9(b) and 9(c), the upper electrode 16 is patterned using, for example, photolithography and etching methods. As a result, the upper electrode 16a is formed on the piezoelectric film 14 of the resonance region 50, and the upper electrode 16b is formed on the insulating film 20 of the capacitor region 58. In FIG. 9(b), the upper electrode 16b is formed on the insulating film 20 on the lower electrode 12. In FIG. 9(c), the upper electrode 16b is not formed on the insulating film 20 on the lower electrode 12. Thereafter, by performing the steps after FIG. 4(c) of the first embodiment, an elastic wave device according to the second embodiment is manufactured.

[0056] In the second embodiment, the upper electrodes 16a and 16b are not electrically connected. As a result, a capacitor 72 can be connected in series with the piezoelectric thin film resonator 70 between the metal layers 22a and 22b.

[0057] The capacitor region 58 is provided in a part of the region 65 where the lower electrode 12 surrounds the resonance region 50, and is not provided in the remaining region 66. Thereby, leakage of the elastic wave of the piezoelectric film 14 through the upper electrode 16b of the capacitor region 58 can be suppressed, and the loss of the piezoelectric thin film resonator 70 can be suppressed.

[0058] In the region 66, the insulating film 20 and the upper electrode 16b are overlapped outside the lower electrode 12. Thereby, the piezoelectric thin film resonator 70 and the capacitor 72 can be supported on the gap 30.

[0059] [Modification Example 1 of Embodiment 2] FIG. 10 is a plan view of an elastic wave device according to Modification Example 1 of Embodiment 2. FIGS. 11(a) and 11(b) are a cross-sectional view taken along line A-A and a cross-sectional view taken along line B-B of FIG. 10, respectively.

[0060] As shown in FIGS. 10 to 11(b), in the elastic wave device 106 of Modification Example 1 of Embodiment 2, the capacitor region 58 is provided in all of the regions 65 where the lower electrode 12 surrounds the resonance region 50. Other configurations are the same as those in Embodiment 2 and the description thereof is omitted.

[0061] In Modification Example 1 of Embodiment 2, although the leakage of the elastic wave from the resonance region 50 is large, the area of the capacitor region 58 can be increased, so that the capacitance of the capacitor 72 can be increased.

[0062] [Modification Example 2 of Embodiment 2] FIG. 12 is a plan view of an elastic wave device according to Modification Example 2 of Embodiment 2. FIGS. 13(a) and 13(b) are a cross-sectional view taken along line A-A and a cross-sectional view taken along line B-B of FIG. 12, respectively.

[0063] As shown in FIGS. 12 to 13(b), in the elastic wave device 108 of Modification 2 of Example 2, the insulating film 20 is formed larger than the gap 30. As shown in FIG. 13(b), in the region 56 where the capacitor region 58 is not provided, the upper electrode 16b is not provided on the gap 30. Other configurations are the same as those of Example 2 and the description thereof is omitted.

[0064] In the region 66 of Modification 2 of Example 2, outside the lower electrode 12, the piezoelectric thin film resonator 70 and the capacitor 72 can be supported on the gap 30 by the insulating film 20.

Example

[0065] Example 3 and Modification 1 thereof are examples in which the configuration of the gap is changed. FIG. 14(a) is a cross-sectional view of the elastic wave device according to Example 3. As shown in FIG. 14(a), in the elastic wave device 110 of Example 3, a depression is formed on the upper surface of the substrate 10. The lower electrode 12 is formed flat on the substrate 10. Thereby, the gap 30 is formed in the depression of the substrate 10. In plan view, the gap 30 is formed to include the resonance region 50 and the capacitor region 58. Other configurations are the same as those of Example 1 and the description thereof is omitted. The gap 30 may be formed to penetrate the substrate 10.

[0066] [Modification 1 of Example 3] FIG. 14(b) is a cross-sectional view of the elastic wave device according to Modification 1 of Example 3. As shown in FIG. 14(b), in the elastic wave device 112 of Modification 1 of Example 3, an acoustic reflection film 31 is formed under the lower electrode 12 in the resonance region 50. The acoustic reflection film 31 is provided with a film 31a having a low acoustic impedance and a film 31b having a high acoustic impedance alternately. The film thicknesses of the films 31a and 31b are, for example, approximately λ / 4 (λ is the wavelength of the elastic wave) respectively. The number of stacked layers of the films 31a and 31b can be arbitrarily set. Other configurations are the same as those of Example 1 and the description thereof is omitted.

[0067] In Examples 1 and 2 and their modified examples, voids 30 similar to those in Example 3 may be formed, or an acoustic reflection film 31 may be formed instead of the voids 30 as in Modified Example 1 of Example 3.

[0068] Although the planar shape of the resonance region 50 has been described by taking an elliptical shape as an example, the planar shape of the resonance region 50 may be any shape such as a polygonal shape such as a rectangular shape or a pentagonal shape.

Example

[0069] Example 4 is an example of a filter and a duplexer using the elastic wave devices of Examples 1 to 3 and their modified examples. FIG. 15(a) is a circuit diagram of the filter according to Example 4. As shown in FIG. 15(a), between an input terminal Tin and an output terminal Tout, one or a plurality of series resonators S1 to S4 are connected in series. Between the input terminal Tin and the output terminal Tout, one or a plurality of parallel resonators P1 to P4 are connected in parallel. One ends of the parallel resonators P1 to P4 are electrically connected to a ground terminal Tgnd. A capacitor C1 is connected in parallel to the series resonator S1. The series resonator S1 and the capacitor C1 are elastic wave devices according to Examples 1 and 3 and their modified examples. By connecting the capacitor C1 in parallel to the series resonator S1, the electromechanical coupling coefficient of the series resonator S1 can be reduced. Thereby, the skirt characteristic on the high-frequency side of the passband can be made steep.

[0070] [Modified Example 1 of Example 4] FIG. 15(b) is a circuit diagram of the filter according to Modified Example 1 of Example 4. As shown in FIG. 15(b), a capacitor C2 is connected in series to the series resonator S1. The series resonator S1 and the capacitor C2 are elastic wave devices according to Example 2 and its modified examples. By providing the capacitor C2, the attenuation characteristic on the lower band side than the passband can be improved. Other configurations are the same as those in Example 4 and the description thereof is omitted.

[0071] In Example 4 and Modification 1 thereof, a capacitor can be connected in parallel or in series to at least one resonator among one or more series resonators S1 to S4 and one or more parallel resonators P1 to P4. The number of resonators of the ladder-type filter and the like can be set as appropriate.

[0072] [Modification 2 of Example 4] FIG. 15(c) is a circuit diagram of a duplexer according to Modification 2 of Example 4. As shown in FIG. 15(c), a transmission filter 40 is connected between the common terminal Ant and the transmission terminal Tx. A reception filter 42 is connected between the common terminal Ant and the reception terminal Rx. The transmission filter 40 passes, as a transmission signal, a signal in the transmission band among the signals input from the transmission terminal Tx to the common terminal Ant, and suppresses signals of other frequencies. The reception filter 42 passes, as a reception signal, a signal in the reception band among the signals input from the common terminal Ant to the reception terminal Rx, and suppresses signals of other frequencies. At least one of the transmission filter 40 and the reception filter 42 can be the filter of Example 4 and Modification 1 thereof.

[0073] Although the duplexer has been described as an example of the multiplexer, a triplexer or a quadplexer may also be used.

[0074] As described above in detail with respect to the embodiments of the present invention, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

Explanation of Reference Numerals

[0075] 10 Substrate 12 Lower electrode 14 Piezoelectric film 16 Upper electrode 20 Insulating film 22a, 22b Metal layer 30 Gap 31 Acoustic reflection film 40 Transmission filter 42 Reception filter 50 Resonance region 52 peripheral part 54 central part 56 outer region 58 region 60, 62 extraction regions 64, 65, 66 regions

Claims

1. A substrate, a lower electrode provided on the substrate, a piezoelectric film provided on the lower electrode, a first upper electrode provided on the piezoelectric film so as to form a resonance region in which the lower electrode and the first upper electrode overlap with each other with at least a part of the piezoelectric film sandwiched therebetween when viewed from the thickness direction of the piezoelectric film, an insulating film provided on the lower electrode from the peripheral portion of the resonance region to an external region surrounding the resonance region, a second upper electrode provided in the external region so as to form a region in which the lower electrode and the second upper electrode overlap with each other with at least a part of the insulating film sandwiched therebetween without sandwiching the piezoelectric film when viewed from the thickness direction, and an elastic wave device comprising the same.

2. The elastic wave device according to claim 1, wherein the first upper electrode and the second upper electrode are provided integrally.

3. The elastic wave device according to claim 2, wherein the overlapping region is provided between a lead-out region where the lower electrode is led out from the resonance region and the resonance region in the external region.

4. The elastic wave device according to claim 3, wherein the first upper electrode and the second upper electrode are connected to each other between the lead-out region and the resonance region.

5. The elastic wave device according to any one of claims 2 to 4, wherein a region where the first upper electrode and the second upper electrode are connected is provided in a part of a region where the overlapping region surrounds the resonance region and is not provided in the remaining part of the surrounding region.

6. The elastic wave device according to claim 1, wherein the first upper electrode and the second upper electrode are not electrically connected to each other.

7. The elastic wave device according to claim 6, wherein the overlapping region is provided in a part of a region where the lower electrode surrounds the resonance region and is not provided in the remaining part of the surrounding region.

8. The elastic wave device according to any one of claims 1 to 4, 6, and 7, wherein in the resonance region, the insulating film is provided between the lower electrode and the piezoelectric film.

9. The elastic wave device according to any one of claims 1 to 4, 6, and 7, wherein the insulating film is not provided at the center of the resonance region and is provided so as to surround at least a part of the center.

10. The elastic wave device according to any one of claims 1 to 4, 6, and 7, wherein a gap is provided between the substrate and the lower electrode, and the resonance region and the overlapping region overlap with the gap when viewed from the thickness direction.

11. A filter including the elastic wave device according to any one of 1 to 4, 6, and 7.

12. A multiplexer including the filter according to Claim 11.

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