JP7344011B2 - Piezoelectric thin film resonators, filters and multiplexers - Google Patents

Description

The present invention relates to piezoelectric thin film resonators, filters and multiplexers, and for example to piezoelectric thin film resonators, filters and multiplexers having a piezoelectric thin film resonator with a vibration suppression layer.

Piezoelectric thin film resonators are used, for example, as filters and multiplexers in wireless devices such as mobile phones. A piezoelectric thin film resonator has a structure in which a lower electrode and an upper electrode face each other with a piezoelectric film in between (Patent Documents 1 and 2).

Japanese Patent Application Publication No. 2013-168748 Japanese Patent Application Publication No. 2006-203304

When a high-power high-frequency signal is applied to the piezoelectric thin film resonator, the laminated film including the lower electrode, piezoelectric film, and upper electrode is damaged. This reduces the power resistance.

The present invention has been made in view of the above problems, and an object of the present invention is to increase the durability of power.

The present invention includes a substrate, a lower electrode provided on the substrate, a piezoelectric film provided on the lower electrode, and a piezoelectric film provided on the piezoelectric film with at least a portion of the piezoelectric film sandwiched between the lower electrodes. an upper electrode provided to form a first region defined by an area overlapping in plan view, and a piezoelectric film in a central region within a second region defined by a region surrounded by the outer periphery of the first region. a vibration suppression layer that is inserted into the piezoelectric film and is not provided in a peripheral area within the second area and suppresses vibrations within the piezoelectric film , and the Young's modulus of the vibration suppression layer is equal to the Young's modulus of the piezoelectric film. It is a smaller piezoelectric thin film resonator.

The present invention includes a substrate, a lower electrode provided on the substrate, a piezoelectric film provided on the lower electrode, and a piezoelectric film provided on the piezoelectric film with at least a portion of the piezoelectric film sandwiched between the lower electrodes. an upper electrode provided to form a first region defined by an area overlapping in plan view, and a piezoelectric film in a central region within a second region defined by a region surrounded by the outer periphery of the first region. a vibration suppression layer that is inserted into the piezoelectric film and is not provided in a peripheral area within the second area and suppresses vibrations within the piezoelectric film, the vibration suppression layer being located at the center of gravity of the planar shape of the second area. A piezoelectric thin film resonator containing

The present invention includes a substrate, a lower electrode provided on the substrate, a piezoelectric film provided on the lower electrode, and a piezoelectric film provided on the piezoelectric film with at least a portion of the piezoelectric film sandwiched between the lower electrodes. an upper electrode provided to form a first region defined by an area overlapping in plan view, and a piezoelectric film in a central region within a second region defined by a region surrounded by the outer periphery of the first region. a vibration suppression layer that is inserted into the piezoelectric film and is not provided in a peripheral area within the second area and suppresses vibrations within the piezoelectric film, and the second area has a substantially elliptical planar shape; The vibration suppression layer is a piezoelectric thin film resonator including a center and/or focal point of the substantially elliptical shape .

The present invention includes a substrate, a lower electrode provided on the substrate, a piezoelectric film provided on the lower electrode, and a piezoelectric film provided on the piezoelectric film with at least a portion of the piezoelectric film sandwiched between the lower electrodes. an upper electrode provided to form a first region defined by an area overlapping in plan view, and a piezoelectric film in a central region within a second region defined by a region surrounded by the outer periphery of the first region. a vibration suppressing layer that is inserted into the piezoelectric film and is not provided in a peripheral area in the second area and suppresses vibrations in the piezoelectric film, and there is only one vibration suppressing layer in the second area. A piezoelectric thin film resonator is provided .

In the above structure, the Young's modulus of the vibration suppression layer may be smaller than the Young's modulus of the piezoelectric film .

In the above configuration, the first area and the second area may be configured to match .

In the above structure, the upper electrode may not be provided in the central region .

In the above structure, the planar area of the vibration suppression layer may be 1/2 or less of the area of the second region .

In the above configuration, an insertion film is provided in a region including the outer periphery of at least a portion of the first region surrounding the central region, spaced apart from the vibration suppression layer in a plane direction, and inserted into the piezoelectric film. be able to.

In the above structure, a gap may be provided between the substrate and the lower electrode, overlapping the second region and larger than the second region in plan view.

The present invention is a filter including the piezoelectric thin film resonator described above.

The present invention is a multiplexer including the above filter.

According to the present invention, high power durability can be achieved.

FIG. 1(a) is a plan view of the piezoelectric thin film resonator according to Example 1, and FIG. 1(b) is a sectional view taken along line AA in FIG. 1(a). FIG. 2(a) is a plan view of a piezoelectric thin film resonator according to Modification Example 1 of Example 1, and FIG. 2(b) is a cross-sectional view taken along line AA in FIG. 2(a). 3(a) is a plan view of a piezoelectric thin film resonator according to a second modification of the first embodiment, and FIG. 3(b) is a sectional view taken along line AA in FIG. 3(a). FIGS. 4A to 4C are cross-sectional views of piezoelectric thin film resonators according to Modifications 3 to 5 of Example 1, respectively. FIG. 5 is a cross-sectional view of a piezoelectric thin film resonator according to a sixth modification of the first embodiment. FIG. 6 is a cross-sectional view of a piezoelectric thin film resonator according to Modification Example 7 of Example 1. FIG. 7 is a cross-sectional view of a piezoelectric thin film resonator according to Modification Example 8 of Example 1. FIGS. 8A and 8B are cross-sectional views of piezoelectric thin film resonators in Modifications 9 and 10 of Example 1, respectively. 9A is a circuit diagram of a filter according to a second embodiment, and FIG. 9B is a circuit diagram of a duplexer according to a first modification of the second embodiment.

Examples will be described below with reference to the drawings.

FIG. 1(a) is a plan view of the piezoelectric thin film resonator according to Example 1, and FIG. 1(b) is a sectional view taken along line AA in FIG. 1(a). FIG. 1A mainly shows the lower electrode 12, the upper electrode 16, and the vibration suppression layer 28.

As shown in FIGS. 1A and 1B, a lower electrode 12 is provided on the substrate 10 and the gap 30. As shown in FIGS. The substrate 10 is, for example, a silicon (Si) substrate, and the lower electrode 12 is, for example, a ruthenium (Ru) film. A gap 30 (air layer) having a dome-shaped bulge is formed between the flat main surface of the substrate 10 and the lower electrode 12. The dome-shaped bulge is, for example, a bulge having a shape such that the height of the void 30 is small around the void 30 and becomes larger toward the inside of the void 30.

A piezoelectric film 14 is provided on the lower electrode 12. The piezoelectric film 14 is mainly composed of, for example, aluminum nitride (AlN) whose main axis is in the C-axis direction. The piezoelectric film 14 includes a lower piezoelectric film 14a and an upper piezoelectric film 14b provided on the lower piezoelectric film 14a. An upper electrode 16 is provided on the piezoelectric film 14 . The upper electrode 16 is, for example, a ruthenium film. Laminated film 18 includes lower electrode 12, piezoelectric film 14, and upper electrode 16.

The resonance region 50 is defined by a region where the lower electrode 12 and the upper electrode 16 overlap in plan view with at least a portion of the piezoelectric film 14 sandwiched therebetween. The planar shape of the resonance region 50 is approximately elliptical. A region surrounded by the outer periphery 51 of the resonance region 50 is defined as a region 58. In the first embodiment, the resonance region 50 and the region 58 coincide. A vibration suppressing layer 28 is provided between the lower piezoelectric film 14a and the upper piezoelectric film 14b in the central region 52 including the center 60 of the region 58. The vibration suppression layer 28 is not provided in the peripheral region 54 including the outer periphery 51 of the resonance region 50 . That is, the vibration suppression layer 28 is provided apart from the outer periphery 51 of the resonance region 50 in plan view.

The resonance region 50 is a region where elastic waves in the thickness longitudinal vibration mode resonate. In the central region 52 where the vibration suppression layer 28 is provided, vibrations of elastic waves are suppressed. For example, the resonant frequency of central region 52 is significantly different from the resonant frequency of peripheral region 54.

As the substrate 10, in addition to a silicon substrate, a sapphire substrate, a spinel substrate, an alumina substrate, a quartz substrate, a glass substrate, a ceramic substrate, a GaAs substrate, or the like can be used. In addition to Ru, the lower electrode 12 and the upper electrode 16 may be made of chromium (Cr), aluminum (Al), titanium (Ti), copper (Cu), molybdenum (Mo), tungsten (W), tantalum (Ta), or platinum. (Pt), rhodium (Rh), iridium (Ir), etc., or a laminated film of these can be used.

In addition to aluminum nitride, the piezoelectric film 14 can be made of zinc oxide (ZnO), lead zirconate titanate (PZT), lead titanate (PbTiO ₃ ), or the like. Further, for example, the piezoelectric film 14 mainly contains aluminum nitride, and may also contain other elements to improve resonance characteristics or piezoelectricity. For example, the piezoelectricity of the piezoelectric film 14 is improved by using Sc (scandium), two elements, a group 2 element and a group 4 element, or two elements, a group 2 element and a group 5 element, as additive elements. do. Therefore, the effective electromechanical coupling coefficient of the piezoelectric thin film resonator can be improved. Group 2 elements are, for example, Ca (calcium), Mg (magnesium), Sr (strontium), or Zn (zinc). The Group 4 element is, for example, Ti, Zr (zirconium) or Hf (hafnium). The Group 5 element is, for example, Ta, Nb (niobium) or V (vanadium). Furthermore, the piezoelectric film 14 mainly contains aluminum nitride and may also contain B (boron).

The vibration suppression layer 28 has a Young's modulus smaller than the Young's modulus of the piezoelectric film 14 . In addition to silicon oxide, the vibration suppressing layer 28 can use a single layer film or a laminated film of aluminum (Al), gold (Au), copper, titanium, platinum, tantalum, chromium, or the like.

The material and thickness of each layer in a piezoelectric thin film resonator having a resonance frequency of approximately 2.5 GHz will be illustrated. The lower electrode 12, the piezoelectric film 14, and the upper electrode 16 are, for example, a 180 nm thick ruthenium film, a 1 μm thick aluminum nitride film, and a 160 nm thick ruthenium film. The vibration suppression layer 28 is, for example, a silicon oxide film with a thickness of 100 nm provided at the center of the piezoelectric film 14 in the thickness direction. The area of the resonant region 50 is between 5000 μm ² and 30000 μm ² .

In response to HPUE (High Power User Equipment) and CA (Carrier Aggregation), piezoelectric thin film resonators are required to have high power durability. When a high-power high-frequency signal is applied between the lower electrode 12 and the upper electrode 16, the temperature of the laminated film 18 near the center 60 within the resonance region 50 increases. In particular, when the gap 30 is provided, the heat of the laminated film 18 in the resonance region 50 is radiated via the outer periphery 51, so that the temperature of the laminated film 18 near the center 60 of the resonance region 50 becomes the highest. As a result, the laminated film 18 near the center 60 of the resonance region 50 is easily damaged. For example, separation of the interface between the lower electrode 12 and the upper electrode 16 or damage to the lower electrode 12 and the upper electrode 16 is likely to occur.

In the first embodiment, heat generation in the central region 52 can be suppressed by providing the vibration suppressing layer 28 in the central region 52 including the center 60 of the resonance region 50. Therefore, even if a high-power high-frequency signal is applied between the lower electrode 12 and the upper electrode 16, damage to the laminated film 18 is suppressed, and the piezoelectric thin film resonator can have high power durability.

Near the center 60 of the resonance region 50, standing waves of transverse mode elastic waves interfere and strengthen each other. In particular, when the outer periphery 51 of the resonance region 50 is curved, the standing waves near the center 60 become stronger. As a result, the laminated film 18 becomes easily damaged and its power resistance decreases. Therefore, by providing the vibration suppression layer 28 in the central region 52 including the center 60, damage to the laminated film 18 is suppressed, and the piezoelectric thin film resonator can have high power durability. In addition, spurious components can be suppressed by weakening standing waves. When the planar shape of the resonance region 50 is approximately elliptical, the standing waves are concentrated near the focal point 62 of the ellipse. Therefore, it is preferable to provide the vibration suppression layer 28 in the central region 52 including the center 60 and/or the focal point 62.

[Modification 1 of Example 1]
FIG. 2(a) is a plan view of a piezoelectric thin film resonator according to Modification Example 1 of Example 1, and FIG. 2(b) is a cross-sectional view taken along line AA in FIG. 2(a). As shown in FIGS. 2(a) and 2(b), an insertion film 26 is inserted between the lower piezoelectric film 14a and the upper piezoelectric film 14b in the outer peripheral region 56 including the outer periphery 51 of the resonance region 50 and along the outer periphery 51. It is provided. The insertion membrane 26 is provided so as to surround the central region 52 and is provided apart from the central region 52 in the plane direction. The material of the insertion film 26 is the same as the material exemplified for the vibration suppression layer 28, and the Young's modulus of the insertion film 26 is smaller than the Young's modulus of the piezoelectric film 14.

By providing the insertion film 26, leakage of elastic waves propagating in the plane direction to the outside of the resonance region 50 can be suppressed, and loss can be suppressed. The insertion film 26 may be provided in at least a part of the area surrounding the central area 52.

By providing the insertion film 26 between the lower piezoelectric film 14a and the upper piezoelectric film 14b, the vibration suppression layer 28 and the insertion film 26 can be formed at the same time. This allows the manufacturing process to be omitted. In this case, the main component of the vibration suppression layer 28 and the main component of the insertion film 26 are the same, and the thickness of the vibration suppression layer 28 and the thickness of the insertion film 26 are approximately the same. The materials of the vibration suppression layer 28 and the insert membrane 26 may be different.

[Modification 2 of Example 1]
3(a) is a plan view of a piezoelectric thin film resonator according to a second modification of the first embodiment, and FIG. 3(b) is a sectional view taken along line AA in FIG. 3(a). As shown in FIGS. 3A and 3B, in the second modification of the first embodiment, the upper electrode 16 is not provided in the central region 52, and a recess 53 is formed. As a result, vibrations of elastic waves are suppressed in the central region 52.

Resonant region 50 includes a peripheral region 54 and does not include a central region 52. Therefore, the region 58 surrounded by the outer periphery 51 of the resonance region 50 and the resonance region 50 do not coincide. The planar shape of the region 58 is approximately elliptical, and the central region 52 includes a center 60 and a focal point 62 of the approximately ellipse. The other configurations are the same as those in Example 1, and their explanation will be omitted.

[Modification 3 of Example 1]
FIG. 4A is a cross-sectional view of a piezoelectric thin film resonator according to a third modification of the first embodiment. As shown in FIG. 4A, in the third modification of the first embodiment, the upper electrode 16 and the upper piezoelectric film 14b are not provided in the central region 52. Thereby, a recess 53 is provided in the central region 52. The other configurations are the same as the second modification of the first embodiment, and the explanation will be omitted.

As in Modifications 2 and 3 of Embodiment 1, at least one of the lower electrode 12, the piezoelectric film 14, and the upper electrode 16 is not provided in the central region 52 including the center 60 and/or focal point 62 of the region 58. You can. As a result, the central region 52 is no longer the resonant region 50, and the elastic waves do not resonate. Therefore, the piezoelectric thin film resonator can have high power durability. Furthermore, since the central region 52 is no longer included in the resonance region 50, the capacitance of the piezoelectric thin film resonator is reduced, and the electromechanical coupling coefficient can be increased. As in the first modification of the first embodiment, when the insertion film 26 is provided, at least one of the lower electrode 12, the piezoelectric film 14, and the upper electrode 16 may not be provided in the central region 52.

[Modification 4 of Example 1]
FIG. 4(b) is a cross-sectional view of a piezoelectric thin film resonator according to a fourth modification of the first embodiment. As shown in FIG. 4B, in the fourth modification of the first embodiment, a vibration suppression layer 28 is provided between the piezoelectric film 14 and the upper electrode 16. The other configurations are the same as those in Example 1, and their explanation will be omitted.

[Modification 5 of Example 1]
FIG. 4C is a cross-sectional view of a piezoelectric thin film resonator according to a fifth modification of the first embodiment. As shown in FIG. 4C, in the fifth modification of the first embodiment, a vibration suppression layer 28 is provided between the lower electrode 12 and the piezoelectric film 14. The other configurations are the same as those in Example 1, and their explanation will be omitted.

As in Modifications 4 and 5 of Example 1, the vibration suppression layer 28 may be inserted into the piezoelectric film 14. Also in the first to third modifications of the first embodiment, the vibration suppression layer 28 only needs to be inserted into the piezoelectric film 14. From the viewpoint of suppressing vibrations of elastic waves, it is preferable that the vibration suppressing layer 28 is provided between the lower piezoelectric film 14a and the upper piezoelectric film 14b as in the first embodiment.

[Modification 6 of Example 1]
FIG. 5 is a cross-sectional view of a piezoelectric thin film resonator according to a sixth modification of the first embodiment. As shown in FIG. 5, in the sixth modification of the first embodiment, the planar shape of the region 58 is approximately elliptical. When the region 58 is approximately elliptical, the vicinity of the center 60 of the approximately ellipse is far from the outer periphery 51 and generates heat easily. Furthermore, transverse mode standing waves tend to concentrate at the focal point 62. Therefore, three vibration suppression layers 28 are provided at each of the center 60 and two focal points 62. Thereby, power durability can be improved. By providing a plurality of vibration suppressing layers 28, the proportion of vibration suppressing layers 28 within the region 58 can be reduced, making it possible to downsize. The other configurations are the same as those in Example 1, and their explanation will be omitted.

[Modification 7 of Example 1]
FIG. 6 is a cross-sectional view of a piezoelectric thin film resonator according to Modification Example 7 of Example 1. As shown in FIG. 6, in the seventh modification of the first embodiment, the region 58 has a substantially circular planar shape. When the region 58 is substantially circular, the vicinity of the substantially circular center 60 is far from the outer periphery 51 and tends to generate heat. Furthermore, transverse mode standing waves tend to concentrate at the center 60. Therefore, by providing the vibration suppression layer 28 near the center 60, power durability can be improved. The other configurations are the same as those in Example 1, and their explanation will be omitted.

[Modification 8 of Example 1]
FIG. 7 is a cross-sectional view of a piezoelectric thin film resonator according to Modification Example 8 of Example 1. As shown in FIG. 7, in the eighth modification of the first embodiment, the planar shape of the region 58 is approximately polygonal. When the planar shape of the region 58 is substantially polygonal, the vicinity of the center 60 (center of gravity) of the substantially polygonal region is far from the outer periphery 51 and easily generates heat. Furthermore, transverse mode standing waves tend to concentrate at the center 60. Therefore, by providing the vibration suppression layer 28 near the center 60, power durability can be improved. The other configurations are the same as those in Example 1, and their explanation will be omitted.

As in Modifications 7 and 8 of Embodiment 1, the planar shape of region 58 can be set arbitrarily. The vibration suppression layer 28 is preferably provided at the center of gravity of the region 58. In Modifications 1 to 6 of Embodiment 1 as well, the planar shape of the region 58 can be made arbitrary. The vibration suppression layer 28 is preferably provided at the center of gravity of the planar shape of the region 58.

[Modification 9 of Example 1]
FIG. 8(a) is a cross-sectional view of a piezoelectric thin film resonator in modification example 9 of example 1. As shown in FIG. 8(a), a depression is formed on the upper surface of the substrate 10. The lower electrode 12 is formed flat on the substrate 10. As a result, a void 30 is formed in the depression of the substrate 10. The air gap 30 is formed to include a resonance region 50. The other configurations are the same as in Example 1, and the explanation will be omitted. The void 30 may be formed to penetrate the substrate 10. Note that an insulating film may be formed in contact with the lower surface of the lower electrode 12. That is, the void 30 may be formed between the substrate 10 and the insulating film in contact with the lower electrode 12. For example, an aluminum nitride film can be used as the insulating film. The other configurations are the same as those in the first embodiment, and their explanation will be omitted.

[Modification 10 of Example 1]
FIG. 8(b) is a cross-sectional view of a piezoelectric thin film resonator in Modification 10 of Example 1. As shown in FIG. 8(b), an acoustic reflection film 31 is formed under the lower electrode 12 in the resonance region 50. The acoustic reflection film 31 includes films 31b with low acoustic impedance and films 31a with high acoustic impedance alternately provided. The thicknesses of the films 31a and 31b are, for example, approximately λ/4 (λ is the wavelength of the elastic wave). The number of laminated films 31a and 31b can be set arbitrarily. The acoustic reflection film 31 may be formed by laminating at least two types of layers having different acoustic characteristics with an interval between them. Further, the substrate 10 may be one of at least two types of layers of the acoustic reflection film 31 having different acoustic characteristics. For example, the acoustic reflection film 31 may have a structure in which two films with different acoustic impedances are provided in the substrate 10. The other configurations are the same as in Example 1, and the explanation will be omitted.

In Embodiment 1 and Modifications 1 to 8 thereof, a void 30 may be formed as in Modification 9 of Embodiment 1, and an acoustic reflective film 31 may be formed in place of the void 30 as in Modification 10 of Embodiment 1. may be formed.

As in Example 1 and Modifications 1 to 9 thereof, the piezoelectric thin film resonator may be an FBAR (Film Bulk Acoustic Resonator) in which a gap 30 is formed between the substrate 10 and the lower electrode 12 in the resonance region 50. . Further, as in Modification 10 of Embodiment 1, the piezoelectric thin film resonator is an SMR (Solidly Mounted Resonator) including an acoustic reflection film 31 that reflects elastic waves propagating through the piezoelectric film 14 under the lower electrode 12 in the resonance region 50. ) is also fine. The acoustic reflection layer including the resonance region 50 may include the void 30 or the acoustic reflection film 31.

According to the first embodiment and its modifications, the vibration suppression layer 28 is located in the central region 52 within the region 58 (second region) defined by the region surrounded by the outer periphery 51 of the resonance region 50 (first region). It is inserted into the piezoelectric film 14 and is not provided in the peripheral region 54 within the region 58 to suppress vibrations within the piezoelectric film 14 . This enables high power durability.

As in the first embodiment and its modifications 1, 4 to 10, the resonance region 50 and the region 58 may coincide. The upper electrode 16 may not be provided in the central region 52 as in Modifications 2 and 3 of the first embodiment. Thereby, capacitance can be reduced.

The vibration suppression layer 28 includes the center of gravity of the planar shape of the region 58 . This makes it possible to achieve higher power durability.

As in Example 1 and its modifications 1 to 6, 9, and 10, the planar shape of the vibration suppression layer 28 is approximately elliptical, and the vibration suppression layer 28 has a center 60 and/or a focal point 62 of the approximately ellipse. include. This makes it possible to achieve higher power durability.

The region where the vibration suppression layer 28 is provided does not contribute to resonance. Therefore, if the area of the vibration suppression layer 28 becomes large, the piezoelectric thin film resonator becomes large. Therefore, it is preferable that only one vibration suppressing layer 28 is provided in the region 58, as in the first embodiment and its modified examples 1 to 5 and 7 to 10. This allows downsizing.

When the planar shape of the region 58 is approximately elliptical, as in the first embodiment and its modifications 1 to 5, 9 and 10, only one vibration suppressing layer 28 including the center 60 and the focal point 62 is present in the region 58. However, other vibration suppressing layers 28 may not be provided within the region 58 . As in the sixth modification of the first embodiment, two or three vibration suppression layers 28 including a center 60 and a focal point 62 are provided within the region 58, and no other vibration suppression layers 28 are provided within the region 58. You can. Further, the vibration suppressing layer 28 may include the center 60 and not include the focal point 62, or may include at least one of the focal points 62 and not include the center 60. This allows downsizing.

The planar area of the vibration suppression layer 28 is preferably 1/2 or less of the area of the region 58, more preferably 1/4 or less, and even more preferably 1/10 or less. This allows the piezoelectric thin film resonator to be miniaturized. The planar area of the vibration suppression layer 28 is preferably 1/100 or more of the area of the region 58. This makes it possible to achieve higher power durability.

The Young's modulus of the vibration suppression layer 28 is smaller than the Young's modulus of the piezoelectric film 14. This further suppresses vibration and enables higher power durability.

As in Example 1 and Modifications 1 to 9 thereof, the gap 30 is provided between the substrate 10 and the lower electrode 12, overlapping with the region 58 and larger than the region 58 in plan view. In this case, the laminated film 18 near the center 60 of the resonance region 50 becomes high temperature. Therefore, by providing the vibration suppression layer 28, it becomes possible to achieve higher power durability.

Example 2 is an example of a filter and a duplexer using the piezoelectric thin film resonator of Example 1 and its modification. FIG. 9(a) is a circuit diagram of a filter according to the second embodiment. As shown in FIG. 9(a), one or more series resonators S1 to S4 are connected in series between the input terminal T1 and the output terminal T2. One or more parallel resonators P1 to P4 are connected in parallel between the input terminal T1 and the output terminal T2. The piezoelectric thin film resonator of Example 1 and its modifications can be used for at least one of the one or more series resonators S1 to S4 and the one or more parallel resonators P1 to P4. The number of resonators of the ladder filter can be set as appropriate.

When a high-power high-frequency signal is input to the input terminal T1, the highest high-frequency signal is applied to the series resonator S1 that is closest in circuit configuration to the input terminal T1 among the plurality of series resonators S1 to S4. Therefore, it is preferable that the series resonator S1 be the piezoelectric thin film resonator of the first embodiment and its modifications. It is preferable that at least one of the series resonators S1 to S4 and the parallel resonators P1 to P4 not be provided with the vibration suppression layer 28. This allows the filter to be made smaller.

FIG. 9(b) is a circuit diagram of a duplexer according to a first modification of the second embodiment. As shown in FIG. 9(b), 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 signals in the transmission band among the signals input from the transmission terminal Tx to the common terminal Ant as transmission signals, and suppresses signals at other frequencies. The reception filter 42 passes signals in the reception band among the signals input from the common terminal Ant to the reception terminal Rx as reception signals, and suppresses signals at other frequencies. At least one of the transmission filter 40 and the reception filter 42 can be the filter of the second embodiment. A high-power high-frequency signal is applied to the transmission filter 40 . Therefore, it is preferable to use the filter of the second embodiment as the transmission filter 40.

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

Although the 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 variations can be made within the scope of the gist of the present invention as described in the claims. Changes are possible.

10 Substrate 12 Lower electrode 14 Piezoelectric film 16 Upper electrode 18 Laminated film 26 Insert film 28 Vibration suppression layer 30 Gap 40 Transmission filter 42 Reception filter 50 Resonance region 51 Outer 52 Central region 54 Peripheral region 56 Outer region 58 Region 60 Center 62 Focus

Claims (12)

A substrate and
a lower electrode provided on the substrate;
a piezoelectric film provided on the lower electrode;
an upper electrode provided on the piezoelectric film so as to form a first region defined by a region that overlaps the lower electrode in plan view with at least a portion of the piezoelectric film sandwiched therebetween;
It is inserted into a piezoelectric film in a central region within a second region defined by an area surrounded by the outer periphery of the first region, is not provided in a peripheral region within the second region, and is not provided in a peripheral region within the second region, and is inserted into a piezoelectric film in a central region defined by an area surrounded by the outer periphery of the first region. a vibration suppression layer that suppresses
Equipped with
A piezoelectric thin film resonator in which the vibration suppression layer has a Young's modulus smaller than that of the piezoelectric film . A substrate and
a lower electrode provided on the substrate;
a piezoelectric film provided on the lower electrode;
an upper electrode provided on the piezoelectric film so as to form a first region defined by a region that overlaps the lower electrode in plan view with at least a portion of the piezoelectric film sandwiched therebetween;
It is inserted into a piezoelectric film in a central region within a second region defined by an area surrounded by the outer periphery of the first region, is not provided in a peripheral region within the second region, and is not provided in a peripheral region within the second region, and is inserted into a piezoelectric film in a central region defined by an area surrounded by the outer periphery of the first region. a vibration suppression layer that suppresses
Equipped with
The vibration suppression layer is a piezoelectric thin film resonator including a center of gravity of the planar shape of the second region. A substrate and
a lower electrode provided on the substrate;
a piezoelectric film provided on the lower electrode;
an upper electrode provided on the piezoelectric film so as to form a first region defined by a region that overlaps the lower electrode in plan view with at least a portion of the piezoelectric film sandwiched therebetween;
It is inserted into a piezoelectric film in a central region within a second region defined by an area surrounded by the outer periphery of the first region, is not provided in a peripheral region within the second region, and is not provided in a peripheral region within the second region, and is inserted into a piezoelectric film in a central region defined by an area surrounded by the outer periphery of the first region. a vibration suppression layer that suppresses
Equipped with
A piezoelectric thin film resonator in which the second region has a substantially elliptical planar shape, and the vibration suppression layer includes a center and/or focal point of the substantially elliptical shape. A substrate and
a lower electrode provided on the substrate;
a piezoelectric film provided on the lower electrode;
an upper electrode provided on the piezoelectric film so as to form a first region defined by a region that overlaps the lower electrode in plan view with at least a portion of the piezoelectric film sandwiched therebetween;
It is inserted into a piezoelectric film in a central region within a second region defined by an area surrounded by the outer periphery of the first region, is not provided in a peripheral region within the second region, and is not provided in a peripheral region within the second region, and is inserted into a piezoelectric film in a central region defined by an area surrounded by the outer periphery of the first region. a vibration suppression layer that suppresses
Equipped with
In the piezoelectric thin film resonator, only one vibration suppression layer is provided in the second region. The piezoelectric thin film resonator according to any one of claims 2 to 4 , wherein the Young's modulus of the vibration suppression layer is smaller than the Young's modulus of the piezoelectric film. The piezoelectric thin film resonator according to any one of claims 1 to 5, wherein the first region and the second region coincide. The piezoelectric thin film resonator according to any one of claims 1 to 5, wherein the upper electrode is not provided in the central region. The piezoelectric thin film resonator according to any one of claims 1 to 7 , wherein the planar area of the vibration suppression layer is 1/2 or less of the area of the second region. Any one of claims 1 to 8 , further comprising an insertion film provided in a region including an outer periphery of at least a portion of the first region surrounding the central region and spaced apart from the vibration suppression layer in a plane direction and inserted into the piezoelectric film. The piezoelectric thin film resonator according to item 1. The piezoelectric thin film resonator according to any one of claims 1 to 9, wherein a gap that overlaps with the second region and is larger than the second region is provided between the substrate and the lower electrode in plan view. . A filter comprising a piezoelectric thin film resonator according to any one of claims 1 to 10. A multiplexer comprising a filter according to claim 11.

Images