JP2018101964A - Acoustic wave device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To downsize an acoustic wave device.SOLUTION: An acoustic wave device comprises a piezoelectric thin film resonator 40 which includes a piezoelectric film 14 provided on a substrate 10, and an electrode 12 and an electrode 16, provided that the piezoelectric film 14 is located between the electrodes in direction of a c-axis of the piezoelectric film 14 or a polarization axis, and which has a resonance region 24 consisting of a region overlapping with a gap 22 formed between the substrate 10 and the electrode 12 in plane view in a region where the electrode 12 and the electrode 16 are opposed to each other with the piezoelectric film 14 located therebetween. The acoustic wave device further comprises a piezoelectric thin film resonator 42 which includes the electrode 16, a piezoelectric film 18 provided on the electrode 16 and having a thickness substantially the same as that of the piezoelectric film 14, and a c-axis or polarization axis in the same direction as that of the c-axis of the piezoelectric film 14 or polarization axis, and an electrode 20 provided on the piezoelectric film 18, provided that the electrode is at the same potential as the electrode 12, and which has a resonance region 26 which is a region overlapping with the gap 22 in plane view in a region where the electrode 16 and the electrode 20 are opposed to each other with the piezoelectric film 18 located therebetween and which has an area substantially the same as that of the resonance region 24 and overlapping with the resonance region 24.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an acoustic wave device.

  It is known to use a piezoelectric thin film resonator for a filter or duplexer of a wireless communication device such as a mobile phone terminal. The piezoelectric thin film resonator includes a piezoelectric film and two electrodes facing each other with the piezoelectric film interposed therebetween. When the direction of the c-axis or polarization axis of the piezoelectric film and the direction of the electric field applied between the two electrodes are in the same direction, the piezoelectric thin film resonator contracts, and in the opposite direction, Piezoelectric thin film resonators expand. For this reason, in the piezoelectric thin film resonator, the second-order strain characteristic is deteriorated due to nonlinearity depending on the direction of the c-axis or the polarization axis of the piezoelectric film. Therefore, a method is known that reduces nonlinearity and suppresses the degradation of secondary distortion characteristics (for example, Patent Document 1). In addition, it is known that a plurality of piezoelectric thin film resonators are stacked and arranged (for example, Patent Documents 2 and 3).

JP 2007-6495 A JP-T-2006-502634 JP 2005-137002 A

  In Patent Document 1, a secondary distortion characteristic is obtained by connecting these two piezoelectric thin film resonators in parallel so that electrodes in the same direction of the polarization axes of the two piezoelectric thin film resonators have opposite potentials. However, there is still room for improvement in terms of downsizing the acoustic wave device.

  The present invention has been made in view of the above problems, and aims to reduce the size of an acoustic wave device.

  The present invention includes a first piezoelectric film provided on a substrate, and a first electrode and a second electrode sandwiching the first piezoelectric film in the direction of the c-axis or the polarization axis of the first piezoelectric film, A region overlapping the gap or acoustic reflection film formed between the substrate and the first electrode in plan view in a region where the first electrode and the second electrode face each other across the first piezoelectric film. A first piezoelectric thin film resonator having a first resonance region; the second electrode; and the second piezoelectric electrode. The first piezoelectric thin film resonator has substantially the same thickness as the first piezoelectric film. A second piezoelectric film having a c-axis or a polarization axis in the same direction as the axis or the polarization axis, and a third electrode provided on the second piezoelectric film and having the same potential as the first electrode. A region overlapping the gap or the acoustic reflection film in a plan view among regions where the second electrode and the third electrode face each other with the piezoelectric film interposed therebetween There are a acoustic wave device and a second piezoelectric thin-film resonator having a second resonant region overlapping with the first resonance region and substantially have the same area and the first resonance region.

  In the above configuration, the first electrode and the third electrode may be connected to each other outside the first resonance region and the second resonance region.

  In the above configuration, the second electrode may have a thickness that is approximately twice the thickness of the first electrode and the thickness of the third electrode.

  In the above configuration, the acoustic wave device is a ladder filter including one or more series resonators and one or more parallel resonators, and the one or more series resonators and the one or more parallel resonances. At least one of the resonators is divided into two resonators, and the two resonators are the first piezoelectric thin film resonator and the second piezoelectric thin film resonator. it can.

  In the above configuration, a resonator other than the at least one resonator among the one or more series resonators and the one or more parallel resonators includes a third piezoelectric film provided on the substrate, A lower electrode and an upper electrode sandwiching the third piezoelectric film, wherein the lower electrode has substantially the same thickness as the first electrode, and the upper electrode has substantially half the thickness of the second electrode It can be.

  In the above configuration, at least one parallel resonator of the one or more parallel resonators is divided into the two resonators, and the first piezoelectric thin film resonance constituting the at least one parallel resonator. The first frequency adjusting film may be provided in the second electrode shared by the resonator and the second piezoelectric thin film resonator.

  In the above configuration, a parallel resonator other than the at least one parallel resonator among the one or a plurality of parallel resonators includes a second frequency adjustment film having a thickness approximately half that of the first frequency adjustment film. It can be.

  In the above configuration, the acoustic wave device is a dual filter including a first ladder filter and a second ladder filter having a lower pass band than the first ladder filter, and the first ladder filter includes At least one of the one or more series resonators and the one or more parallel resonators is divided into two resonators, and the two resonators are the first piezoelectric thin film resonator and the first resonator. A series resonator and a parallel resonator that are piezoelectric thin film resonators provided in the second ladder type filter, and the at least one resonator provided in the first ladder type filter is a second piezoelectric thin film resonator. It can be set as the structure provided on one said board | substrate.

  In the above configuration, the acoustic wave device is a duplexer including a transmission filter connected between an antenna terminal and a transmission terminal, and a reception filter connected between the antenna terminal and the reception terminal, At least one of the transmission filter and the reception filter is a ladder type filter including one or more series resonators and one or more parallel resonators, and the one or more series resonators and the one or more parallel resonances. At least one of the resonators may be divided into two resonators, and the two resonators may be the first piezoelectric thin film resonator and the second piezoelectric thin film resonator.

  According to the present invention, the acoustic wave device can be reduced in size.

FIG. 1A and FIG. 1B are diagrams for explaining a secondary strain voltage generated in the piezoelectric film of the piezoelectric thin film resonator. 2A and 2B are diagrams for explaining an elastic wave device according to Comparative Example 1, and FIGS. 2C and 2D are for explaining an elastic wave device according to Comparative Example 2. FIG. FIG. FIG. 3A is a plan view illustrating the acoustic wave device according to the first embodiment, and FIG. 3B is a cross-sectional view taken along a line AA in FIG. FIG. 4 is an exploded plan view of the acoustic wave device according to the first embodiment. FIG. 5A and FIG. 5B are diagrams for explaining the secondary strain characteristics of the acoustic wave device according to the first embodiment. FIG. 6 is a cross-sectional view in the case where the electrodes are connected via other wiring outside the resonance region. FIG. 7A to FIG. 7F are cross-sectional views of acoustic wave devices according to the first to sixth modifications of the first embodiment. FIG. 8 is a cross-sectional view of the acoustic wave device according to the second embodiment. FIG. 9 is a cross-sectional view of the acoustic wave device according to the third embodiment. FIG. 10 is a circuit diagram of a ladder filter according to the fourth embodiment. FIG. 11A to FIG. 11D are cross-sectional views showing a series resonator and a parallel resonator. FIG. 12 is a circuit diagram of a dual filter according to the fifth embodiment. FIG. 13A and FIG. 13B are cross-sectional views of chips that constitute the dual filter according to the fifth embodiment. FIG. 14 is a block diagram illustrating a duplexer according to the sixth embodiment.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, the secondary strain voltage generated in the piezoelectric film of the piezoelectric thin film resonator will be described. FIG. 1A and FIG. 1B are diagrams for explaining a secondary strain voltage generated in the piezoelectric film of the piezoelectric thin film resonator. As shown in FIG. 1A, the piezoelectric thin film resonator 1 has a structure in which a piezoelectric film 2 is sandwiched between a lower electrode 4 and an upper electrode 6. In the piezoelectric thin film resonator, ½ of the wavelength (λ) of the resonance frequency corresponds to the thickness of the piezoelectric material. That is, the piezoelectric thin film resonator is a resonator using 1 / 2λ thickness resonance. For this reason, excitation is performed so that the upper and lower surfaces of the piezoelectric film 2 are polarized to either + or −.

  On the other hand, the wavelength of the secondary strain frequency corresponds to the thickness of the piezoelectric film. For this reason, excitation is performed so that the upper and lower surfaces of the piezoelectric film 2 are both polarized to + or −. If the piezoelectric film 2 has symmetry, the upper and lower electrodes have the same potential in the secondary mode, so that no distortion component should occur. However, in order to obtain good characteristics, aluminum nitride, zinc oxide or the like is used as the piezoelectric film 2, and the piezoelectric film 2 is sandwiched between the lower electrode 4 and the upper electrode 6 in the c-axis direction of the piezoelectric film 2. In FIG. 1B, the c-axis orientation direction of the piezoelectric film 2 is indicated by a white arrow. In FIG. 2 and subsequent figures, the c-axis orientation direction is indicated by white arrows. In this case, the symmetry in the c-axis direction may be lost, and the electric field distribution may be biased, causing a potential difference between the upper and lower sides of the piezoelectric film 2. The voltage generated thereby is called a secondary distortion voltage, and is indicated by a black arrow in FIG. In FIG. 2 and subsequent figures, the direction of the secondary distortion voltage is indicated by a black arrow. In FIG. 1B, the c-axis orientation direction is the direction from the lower electrode 4 to the upper electrode 6, and a secondary strain voltage is generated in this direction.

  2A and 2B are diagrams for explaining an elastic wave device according to Comparative Example 1, and FIGS. 2C and 2D are for explaining an elastic wave device according to Comparative Example 2. FIG. FIG. As shown in FIGS. 2A and 2B, the acoustic wave device 1000 of Comparative Example 1 includes the piezoelectric thin film resonator 1a and the piezoelectric thin film resonator 1b connected in parallel between the terminal T1 and the terminal T2. Yes. The piezoelectric thin film resonator 1 a and the piezoelectric thin film resonator 1 b are provided on the substrate 8. The piezoelectric thin film resonator 1a and the piezoelectric thin film resonator 1b are connected so that electrodes in the same direction of the c-axis have the same potential. That is, the upper electrodes 6 in the c-axis orientation direction of the piezoelectric thin film resonator 1a and the piezoelectric thin film resonator 1b are connected so as to have the same potential, and the lower electrodes 4 opposite in the c-axis orientation direction have the same potential. So connected. Thus, in both the piezoelectric thin film resonator 1a and the piezoelectric thin film resonator 1b, the c-axis orientation direction and the direction of the secondary strain voltage are opposite to each other. For this reason, the non-linearity of the piezoelectric thin film resonator 1a and the piezoelectric thin film resonator 1b reinforces, and the secondary distortion characteristics deteriorate.

  2C and 2D, in the acoustic wave device 1100 of the comparative example 2, the piezoelectric thin film resonator 1a and the piezoelectric thin film resonator 1b are connected in parallel, and the piezoelectric thin film resonator 1a The piezoelectric thin film resonator 1b is connected so that the electrodes in the same direction of the c-axis have a reverse potential. That is, the upper electrode 6 of the piezoelectric thin film resonator 1a and the lower electrode 4 of the piezoelectric thin film resonator 1b are connected, and the lower electrode 4 of the piezoelectric thin film resonator 1a and the upper electrode 6 of the piezoelectric thin film resonator 1b are connected. Thereby, in the piezoelectric thin film resonator 1a, the c-axis orientation direction and the direction of the secondary strain voltage are the same, and in the piezoelectric thin film resonator 1b, the c-axis orientation direction and the direction of the secondary strain voltage are opposite. ing. For this reason, the nonlinearity of the piezoelectric thin film resonator 1a and the piezoelectric thin film resonator 1b is canceled or reduced, and deterioration of the secondary distortion characteristics can be suppressed.

  However, in the acoustic wave device 1100 of Comparative Example 2, since the piezoelectric thin film resonator 1a and the piezoelectric thin film resonator 1b are provided side by side on the substrate 8, it is difficult to reduce the size.

  FIG. 3A is a plan view illustrating the acoustic wave device according to the first embodiment, and FIG. 3B is a cross-sectional view taken along a line AA in FIG. FIG. 4 is an exploded plan view of the acoustic wave device according to the first embodiment. As shown in FIGS. 3A to 4, the acoustic wave device 100 according to the first embodiment is provided by stacking a piezoelectric thin film resonator 40 and a piezoelectric thin film resonator 42 on a substrate 10. The substrate 10 is, for example, a silicon substrate.

  The piezoelectric thin film resonator 40 includes an electrode 12 provided on the substrate 10, a piezoelectric film 14 provided on the electrode 12, and an electrode 16 provided on the piezoelectric film 14 with a region facing the electrode 12. And including. In the piezoelectric thin film resonator 40, the electrode 12 functions as a lower electrode, and the electrode 16 functions as an upper electrode. The electrodes 12 and 16 are, for example, ruthenium films. The piezoelectric film 14 is an aluminum nitride film having c-axis orientation with the c-axis as a main axis, for example.

  The piezoelectric thin film resonator 42 includes an electrode 16, a piezoelectric film 18 provided on the electrode 16, and an electrode 20 provided on the piezoelectric film 18 with a region facing the electrode 16. In the piezoelectric thin film resonator 42, the electrode 16 functions as a lower electrode, and the electrode 20 functions as an upper electrode. The electrode 20 is a ruthenium film, for example. The piezoelectric film 18 is an aluminum nitride film having c-axis orientation with the c-axis as a main axis, for example.

  The c-axis orientation direction of the piezoelectric film 14 and the c-axis orientation direction of the piezoelectric film 18 face the same direction. The piezoelectric film 14 and the piezoelectric film 18 have substantially the same thickness, for example, 1200 nm. It should be noted that the substantially same thickness means that the difference in manufacturing error is regarded as the same thickness.

  The electrode 12 and the electrode 16 sandwich the piezoelectric film 14 in the c-axis orientation direction of the piezoelectric film 14. The electrode 16 and the electrode 20 sandwich the piezoelectric film 18 in the c-axis orientation direction of the piezoelectric film 18. The electrode 12 and the electrode 20 have substantially the same thickness, for example, 200 nm. The electrode 16 has a thickness approximately twice that of the electrode 12 and the electrode 20 and is, for example, 400 nm. It should be noted that the substantially same thickness and approximately twice the thickness are regarded as the same thickness and twice the difference in manufacturing error.

  An air gap 22 is provided in the substrate 10 below the flat electrode 12. The gap 22 penetrates the substrate 10, for example, but may be a recess provided on the upper surface of the substrate 10. The piezoelectric thin film resonator 40 has a resonance region 24 that is a region overlapping the gap 22 in a region where the electrode 12 and the electrode 16 face each other with the piezoelectric film 14 interposed therebetween. The piezoelectric thin film resonator 42 has a resonance region 26 that is a region overlapping the gap 22 in a region where the electrode 16 and the electrode 20 face each other with the piezoelectric film 18 interposed therebetween. The resonance regions 24 and 26 have substantially the same area and overlap, for example, have an elliptical shape. The resonance regions 24 and 26 only have to overlap at least partially. Note that “substantially the same area” means that differences in manufacturing errors are regarded as the same area.

  In the resonance region 24, an elastic wave in a thickness longitudinal vibration mode is excited in the piezoelectric film 14 by applying a high-frequency electric signal between the electrode 12 and the electrode 16. In the resonance region 26, an elastic wave in a thickness longitudinal vibration mode is excited in the piezoelectric film 18 by applying a high-frequency electric signal between the electrode 16 and the electrode 20. The resonance regions 24 and 26 are not limited to an elliptical shape, and may have other shapes such as a rectangular shape.

  The electrode 12 and the electrode 20 are electrically connected. For example, the electrode 12 and the electrode 20 are electrically connected by directly contacting the upper surface of the electrode 12 having a flat shape extending from the end faces of the piezoelectric films 14 and 18 outside the resonance regions 24 and 26. Has been. As a result, the electrode 12 and the electrode 20 are at the same potential. The electrode 16 has a potential different from that of the electrode 12 and the electrode 20.

  As the substrate 10, in addition to the silicon substrate, a sapphire substrate, a quartz substrate, a glass substrate, a ceramic substrate, a gallium arsenide substrate, or the like may be used. As the electrode 12, the electrode 16, and the electrode 20, a single-layer metal film of aluminum, copper, chromium, molybdenum, tungsten, tantalum, platinum, ruthenium, rhodium, or iridium, or a stacked film thereof may be used.

  As the piezoelectric films 14 and 18, a zinc oxide film, a lead zirconate titanate film, a lead titanate film, or the like may be used in addition to the aluminum nitride film. The piezoelectric films 14 and 18 may be films containing aluminum nitride as a main component and containing other elements for improving the resonance characteristics or the piezoelectricity. For example, by using scandium as the additive element, the piezoelectricity can be improved and the electromechanical coupling coefficient can be improved.

  FIG. 5A and FIG. 5B are diagrams for explaining the secondary strain characteristics of the acoustic wave device according to the first embodiment. As shown in FIG. 5A and FIG. 5B, the piezoelectric thin film resonator 40 and the piezoelectric thin film resonator 42 having substantially the same impedance characteristics are connected in parallel between the terminal T1 and the terminal T2. In addition, the electrodes in the same direction of the c-axis are connected so as to have a reverse potential. That is, the electrode 12 of the piezoelectric thin film resonator 40 and the electrode 20 of the piezoelectric thin film resonator 42 are connected, and the piezoelectric thin film resonator 40 and the piezoelectric thin film resonator 42 share the electrode 16. Thereby, in the piezoelectric thin film resonator 40, the c-axis orientation direction and the direction of the secondary strain voltage are the same direction, and in the piezoelectric thin film resonator 42, the c-axis orientation direction and the direction of the secondary strain voltage are opposite directions. ing. For this reason, the nonlinearity of the piezoelectric thin film resonator 40 and the piezoelectric thin film resonator 42 is canceled or reduced, and deterioration of the secondary strain characteristics can be suppressed.

  According to the first embodiment, the piezoelectric thin film resonator 40 and the piezoelectric thin film resonator 42 are provided on the substrate 10. The piezoelectric thin film resonator 40 includes a piezoelectric film 14 provided on the substrate 10, and an electrode 12 and an electrode 16 that sandwich the piezoelectric film 14 in the c-axis direction of the piezoelectric film 14. The piezoelectric thin film resonator 42 is provided on the electrode 16, the piezoelectric film 18 having substantially the same thickness as the piezoelectric film 14, and having the c-axis direction in the same direction as the piezoelectric film 14, and the piezoelectric film 18. And an electrode 20 having the same potential as that of the electrode 12. The resonance region 24 of the piezoelectric thin film resonator 40 and the resonance region 26 of the piezoelectric thin film resonator 42 have substantially the same area and overlap each other. As a result, as described with reference to FIGS. 5A and 5B, it is possible to suppress the deterioration of the secondary distortion characteristics. In addition, since the piezoelectric thin film resonator 40 and the piezoelectric thin film resonator 42 are stacked on the substrate 10, the acoustic wave device can be miniaturized.

  Further, according to the first embodiment, as illustrated in FIG. 3B, the electrode 12 and the electrode 20 are connected outside the resonance regions 24 and 26. Thereby, the electrode 12 and the electrode 20 can be made into the same electric potential. The electrode 12 and the electrode 20 are not limited to the case where they are in direct contact outside the resonance regions 24 and 26, and may be connected via other wiring. FIG. 6 is a cross-sectional view in the case where the electrodes are connected via other wiring outside the resonance region. As shown in FIG. 6, a wiring 28 is provided in contact with the upper surface of the electrode 12 exposed in the recess formed in the piezoelectric film 14 and extending on the upper surface of the piezoelectric film 14. The electrode 20 extends from the end surface of the piezoelectric film 18 and is in contact with the upper surface of the wiring 28. Thereby, the electrode 12 and the electrode 20 are connected outside the resonance regions 24 and 26.

  Further, according to the first embodiment, the electrode 16 has a thickness that is approximately twice the thickness of the electrode 12 and the thickness of the electrode 20. Since the electrode 16 is shared as the lower electrode or the upper electrode of the piezoelectric thin film resonator 40 and the piezoelectric thin film resonator 42, the electrode 16 has a thickness approximately twice that of the electrode 12 and the electrode 20, thereby obtaining good characteristics. be able to.

  FIG. 7A to FIG. 7F are cross-sectional views of acoustic wave devices according to the first to sixth modifications of the first embodiment. As shown in FIG. 7A, the gap 50 may be provided in the electrode 16. As shown in FIG. 7B, an insertion film 52 made of an insulating film such as a silicon oxide film may be provided in the piezoelectric films 14 and 18 in the outer peripheral area in the resonance areas 24 and 26. Thereby, the Q value of the resonator can be improved. Further, a gap may be provided instead of the insertion film 52. The insertion film 52 may be provided in contact with the electrode 16 as shown in FIG. 7C, or may be provided in contact with the electrode 12 and the electrode 20 as shown in FIG. 7D. The insertion film 52 is preferably provided on both the piezoelectric films 14 and 18, but may be provided on only one of them.

  A temperature compensation film 54 may be provided in the piezoelectric films 14 and 18 as shown in FIG. The temperature compensation film 54 is a film having an elastic constant with a temperature coefficient opposite to that of the piezoelectric films 14 and 18, and is, for example, a silicon oxide film or a silicon oxide film to which an additive such as fluorine is added. The temperature compensation film 54 is preferably provided on both the piezoelectric films 14 and 18, but may be provided on only one of them. As shown in FIG. 7F, the temperature compensation film 54 may be provided in the electrode 12, the electrode 16, and the electrode 20.

  FIG. 8 is a cross-sectional view of the acoustic wave device according to the second embodiment. As shown in FIG. 8, in the acoustic wave device 200 according to the second embodiment, no through-holes and depressions are formed in the substrate 10, and a dome-shaped bulge is formed on the electrode 12 side between the flat upper surface of the substrate 10 and the electrode 12. A gap 22a having the following is provided. The dome-shaped bulge is, for example, a bulge having a shape in which the height of the gap 22a is low around the gap 22a and the height of the gap 22a is increased toward the inside of the gap 22a. Since other configurations are the same as those of the acoustic wave device 100 of the first embodiment, description thereof is omitted.

  FIG. 9 is a cross-sectional view of the acoustic wave device according to the third embodiment. As shown in FIG. 9, in the acoustic wave device 300 according to the third embodiment, the acoustic reflection film 30 is provided on the lower side of the electrode 12 instead of the gap. The acoustic reflection film 30 is a film that reflects elastic waves, and alternately includes films 32 having a low acoustic impedance and films 34 having a high acoustic impedance. Since other configurations are the same as those of the acoustic wave device 100 of the first embodiment, description thereof is omitted.

  As described above, the piezoelectric thin film resonators 40 and 42 may be FBARs (Film Bulk Acoustic Resonators) or SMRs (Solidly Mounted Resonators).

  In the first to third embodiments, the case where the aluminum nitride film is used as the piezoelectric films 14 and 18 is shown as an example. However, other piezoelectric materials may be used as the direction of the polarization axis instead of the direction of the c axis. Also good. Even in this case, it is possible to suppress the deterioration of the secondary distortion characteristics.

  FIG. 10 is a circuit diagram of a ladder filter according to the fourth embodiment. As illustrated in FIG. 10, the ladder filter 400 according to the fourth embodiment includes one or more series resonators S <b> 1 to S <b> 4 connected in series between the input terminal IN and the output terminal OUT, and one or more parallel resonances. Devices P1 to P3 are connected in parallel. The series resonator S4 is divided into a resonator S4a and a resonator S4b, and the resonator S4a and the resonator S4b are connected in parallel. The parallel resonator P3 is divided into a resonator P3a and a resonator P3b, and the resonator P3a and the resonator P3b are connected in parallel. The capacitances of the resonators S4a and S4b are half of the capacitance of the series resonator S4, and the resonance frequency is the same as that of the series resonator S4. Similarly, the capacitances of the resonator P3a and the resonator P3b are half of the capacitance of the parallel resonator P3, and the resonance frequency is the same as that of the parallel resonator P3.

  FIG. 11A to FIG. 11D are cross-sectional views showing a series resonator and a parallel resonator. As shown in FIGS. 11A and 11B, the resonator S4a constituting the series resonator S4 includes the piezoelectric film 14 provided on the substrate 10, the electrodes 12 and 16 sandwiching the piezoelectric film 14, and ,including. The resonator S4b includes an electrode 16, a piezoelectric film 18 provided on the electrode 16, and an electrode 20 provided on the piezoelectric film 18.

  As shown in FIG. 11C and FIG. 11D, the resonator P3a constituting the parallel resonator P3 includes a piezoelectric film 14 provided on the substrate 10, and electrodes 12 and 16 sandwiching the piezoelectric film 14. ,including. The resonator P3b includes an electrode 16, a piezoelectric film 18 provided on the electrode 16, and an electrode 20 provided on the piezoelectric film 18. A frequency adjusting film 66 is provided in the electrode 16.

  As described above, the resonators S4a and S4b obtained by dividing the series resonator S4, and the resonators P3a and P3b obtained by dividing the parallel resonator P3 are the piezoelectric thin film resonator 40 and the piezoelectric thin film resonance of the first embodiment. Device 42.

  As shown in FIGS. 11A and 11C, the series resonators S1 to S3 include a lower electrode 60 provided on the substrate 10, a piezoelectric film 62 provided on the lower electrode 60, and a piezoelectric film. And an upper electrode 64 provided with a region facing the lower electrode 60 on 62. 11B and 11D, the parallel resonators P1 and P2 include a frequency adjustment film 68 in addition to the lower electrode 60, the piezoelectric film 62, and the upper electrode 64. The frequency adjustment film 68 may be a solid film or may be formed with a pattern such as a hole.

  The lower electrode 60 is made of, for example, the same material as the electrode 12 and has substantially the same thickness. The piezoelectric film 62 is formed of, for example, the same material as the piezoelectric film 14 and has substantially the same thickness. The upper electrode 64 is formed of, for example, the same material as that of the electrode 16 and has a thickness that is substantially half. The frequency adjustment film 68 is formed of the same material as the frequency adjustment film 66, for example, and has a thickness that is substantially half.

  As in the fourth embodiment, the resonator S4a and the resonator S4b obtained by dividing the series resonator S4 may be used as the piezoelectric thin film resonator 40 and the piezoelectric thin film resonator 42 in the first embodiment. The resonator P3a and the resonator P3b obtained by dividing the parallel resonator P3 may be used as the piezoelectric thin film resonator 40 and the piezoelectric thin film resonator 42 according to the first embodiment. That is, at least one of the one or more series resonators S1 to S4 and the one or more parallel resonators P1 to P3 constituting the ladder filter 400 is divided into two resonators, and the two divided The resonator may be the piezoelectric thin film resonator 40 and the piezoelectric thin film resonator 42 according to the first to third embodiments.

  Note that most of the harmonics radiated from the output terminal OUT are harmonics radiated from the series resonator S4 and the parallel resonator P3 close to the output terminal OUT. Therefore, it is preferable that at least one of the series resonator S4 and the parallel resonator P3 is divided into two resonators to be the piezoelectric thin film resonator 40 and the piezoelectric thin film resonator 42 of the first to third embodiments.

  According to the fourth embodiment, the frequency adjustment film 66 is provided in the electrode 16 shared by the resonator P3a and the resonator P3b obtained by dividing the parallel resonator P3. In order to make the resonance frequency different between the series resonator and the parallel resonator, a frequency adjustment film is provided in the parallel resonator. By providing the frequency adjustment film 66 in the electrode 16, the resonator P3a and the resonator P3b are provided. Thus, one frequency adjustment film 66 can be shared. Instead of providing the frequency adjustment film 66 in the electrode 16, a frequency adjustment film may be provided on the lower surface of the electrode 12 and the upper surface of the electrode 20. In this case, the frequency adjustment film provided on the lower surface of the electrode 12 and the upper surface of the electrode 20 is preferably approximately half the thickness of the frequency adjustment film 66 provided in the electrode 16.

  Further, according to the fourth embodiment, the frequency adjustment film 68 included in the parallel resonators P <b> 1 and P <b> 2 has approximately half the thickness of the frequency adjustment film 66 provided in the electrode 16. As described above, since the frequency adjustment film 66 provided in the electrode 16 is shared by the resonator P3a and the resonator P3b, the frequency adjustment film 66 is approximately twice as thick as the frequency adjustment film 68 (that is, the frequency adjustment film 68). The frequency adjustment film 68 is preferably approximately half the thickness of the frequency adjustment film 66.

  FIG. 12 is a circuit diagram of a dual filter according to the fifth embodiment. As illustrated in FIG. 12, the dual filter 500 according to the fifth embodiment includes a ladder filter 400 and a ladder filter 410. The pass band of the ladder filter 410 is lower than the pass band of the ladder filter 400, for example, about half. For example, the pass band of the ladder filter 400 is 3.5 GHz, and the pass band of the ladder filter 410 is 2 GHz.

  Since the ladder filter 400 has been described in the fourth embodiment, the description thereof is omitted here. The ladder filter 410 has one or more series resonators S11 to S14 connected in series between an input terminal IN and an output terminal OUT, and one or more parallel resonators P11 to P13 connected in parallel. Yes. The series resonators S11 to S14 and the parallel resonators P11 to P13 are not divided.

  FIG. 13A and FIG. 13B are cross-sectional views of chips that constitute the dual filter according to the fifth embodiment. As shown in FIG. 13A, on one substrate 10, series resonators S11 to S14, parallel resonators P11 to P13, series resonator S4, and parallel resonator P3 are provided. That is, in addition to the series resonators S11 to S14 and the parallel resonators P11 to P13 included in the ladder type filter 410, the series resonator S4 and the parallel resonator P3 included in the ladder type filter 400 are provided on one chip. ing.

  The series resonators S11 to S14 and the parallel resonators P11 to P13 include a piezoelectric film 72 including a piezoelectric film 72a and a piezoelectric film 72b provided on the substrate 10, and a lower electrode 70 and an upper electrode facing each other with the piezoelectric film 72 interposed therebetween. 74. Although the temperature compensation film 76 is provided between the piezoelectric film 72a and the piezoelectric film 72b, the temperature compensation film 76 may not be provided. The frequency adjustment films provided in the parallel resonators P11 to P13 are not shown.

  As described in the fourth embodiment, the resonator S4a and the resonator S4b obtained by dividing the series resonator S4 and the resonator P3a and the resonator P3b obtained by dividing the parallel resonator P3 are the piezoelectric thin film resonators of the first embodiment. 40 and a piezoelectric thin film resonator 42.

  The lower electrode 70 and the electrode 12 are made of, for example, the same material and have substantially the same film thickness. The piezoelectric film 72a and the piezoelectric film 14 are formed of the same material, for example, and have substantially the same film thickness. The temperature compensation film 76 and the electrode 16 have, for example, substantially the same film thickness. The piezoelectric film 72b and the piezoelectric film 18 are formed of the same material, for example, and have substantially the same film thickness. The upper electrode 74 and the electrode 20 are made of, for example, the same material and have substantially the same film thickness.

  As shown in FIG. 13B, series resonators S1 to S3 and parallel resonators P1 and P2 are provided on another substrate 10. That is, the series resonators S1 to S3 and the parallel resonators P1 and P2 included in the ladder filter 400 are provided on the other chip. The series resonators S1 to S3 and the parallel resonators P1 and P2 include a piezoelectric film 82 provided on the substrate 10, and a lower electrode 80 and an upper electrode 84 that face each other with the piezoelectric film 82 interposed therebetween. The frequency adjustment films provided in the parallel resonators P1 and P2 are not shown.

  According to the fifth embodiment, one ladder filter 410 constituting the dual filter 500 has a lower pass band (for example, about half) than the other ladder filter 400. Therefore, the thickness of the laminated film in the resonance region of the series resonators S11 to S14 and the parallel resonators P11 to P13 included in the ladder filter 410 is the same as that of the series resonators S1 to S4 and the parallel resonator included in the ladder filter 400. It becomes thicker (for example, about twice as thick) as the laminated film in the resonance region of P1 to P3. For this reason, as shown in FIG. 13A, the series resonators S11 to S14 and the parallel resonators P11 to P13 included in the ladder filter 410 and the ladder filter 400 are divided into two resonators. It is preferable to provide the series resonator S4 and the parallel resonator P3 on one substrate 10.

  FIG. 14 is a block diagram illustrating a duplexer according to the sixth embodiment. As illustrated in FIG. 14, the duplexer 600 according to the sixth embodiment includes a transmission filter 90 and a reception filter 92. The transmission filter 90 is connected between the antenna terminal Ant and the transmission terminal Tx. The reception filter 92 is connected between the antenna terminal Ant common to the transmission filter 90 and the reception terminal Rx.

  The transmission filter 90 passes signals in the transmission band among the signals input from the transmission terminal Tx as transmission signals to the antenna terminal Ant, and suppresses signals of other frequencies. The reception filter 92 passes a signal in the reception band among the signals input from the antenna terminal Ant to the reception terminal Rx as a reception signal, and suppresses signals of other frequencies. The transmission band and the reception band have different frequencies. Note that a matching circuit that matches impedance so that a transmission signal that has passed through the transmission filter 90 is output from the antenna terminal Ant without leaking to the reception filter 92 may be provided.

  At least one of the transmission filter 90 and the reception filter 92 can be the ladder filter 400 of the fourth embodiment.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

DESCRIPTION OF SYMBOLS 10 Substrate 12 Electrode 14 Piezoelectric film 16 Electrode 18 Piezoelectric film 20 Electrode 22, 22a Air gap 24 Resonance area 26 Resonance area 28 Wiring 30 Acoustic reflection film 32 Low acoustic impedance film 34 High acoustic impedance film 40 Piezoelectric thin film resonator 42 Piezoelectric thin film Resonator 50 Gap 52 Insertion film 54 Temperature compensation film 60 Lower electrode 62 Piezoelectric film 64 Upper electrode 66, 68 Frequency adjustment film 70 Lower electrode 72, 72a, 72b Piezoelectric film 74 Upper electrode 76 Temperature compensation film 80 Lower electrode 82 Piezoelectric film 84 Upper electrode 90 Transmission filter 92 Reception filter 100-300 Elastic wave device 400, 410 Ladder type filter 500 Dual filter 600 Duplexer S1-S4, S11-S14 Series resonator P1-P3, P11-P13 Parallel resonator S4a, S4b Resonance P3a, P3b resonator

Claims (8)

A first piezoelectric film provided on a substrate; and a first electrode and a second electrode sandwiching the first piezoelectric film in a direction of a c-axis or a polarization axis of the first piezoelectric film, and the first piezoelectric film A first resonance region that is a region overlapping a gap or an acoustic reflection film formed between the substrate and the first electrode in plan view in a region where the first electrode and the second electrode are opposed to each other A first piezoelectric thin film resonator having:
The second electrode is provided on the second electrode, has the same thickness as the first piezoelectric film, and has a c-axis or polarization axis in the same direction as the c-axis or polarization axis of the first piezoelectric film. A second piezoelectric film provided on the second piezoelectric film, and a third electrode having the same potential as the first electrode, the second electrode and the third electrode sandwiching the second piezoelectric film Is a region that overlaps the air gap or the acoustic reflection film in a plan view among regions facing each other, and has a second resonance region that has substantially the same area as the first resonance region and overlaps the first resonance region. An elastic wave device comprising: a second piezoelectric thin film resonator.   The acoustic wave device according to claim 1, wherein the first electrode and the third electrode are connected to each other outside the first resonance region and the second resonance region.   3. The acoustic wave device according to claim 1, wherein the second electrode has a thickness approximately twice as large as a thickness of the first electrode and a thickness of the third electrode. The acoustic wave device is a ladder type filter including one or more series resonators and one or more parallel resonators,
At least one of the one or more series resonators and the one or more parallel resonators is divided into two resonators,
4. The acoustic wave device according to claim 1, wherein the two resonators are the first piezoelectric thin film resonator and the second piezoelectric thin film resonator. 5. At least one of the one or more parallel resonators is divided into the two resonators;
5. The acoustic wave according to claim 4, further comprising a first frequency adjustment film in the second electrode shared by the first piezoelectric thin film resonator and the second piezoelectric thin film resonator constituting the at least one parallel resonator. device.   6. The parallel resonator other than the at least one parallel resonator among the one or more parallel resonators includes a second frequency adjustment film having a thickness approximately half that of the first frequency adjustment film. Acoustic wave device. The acoustic wave device is a dual filter comprising a first ladder filter and a second ladder filter having a pass band lower than that of the first ladder filter,
At least one of the one or more series resonators and the one or more parallel resonators included in the first ladder filter is divided into two resonators, and the two resonators are the first resonator. 1 piezoelectric thin film resonator and the second piezoelectric thin film resonator,
A series resonator and a parallel resonator composed of piezoelectric thin film resonators provided in the second ladder type filter, and the at least one resonator provided in the first ladder type filter are provided on one substrate. The elastic wave device according to any one of claims 1 to 3. The acoustic wave device is a duplexer comprising a transmission filter connected between an antenna terminal and a transmission terminal, and a reception filter connected between the antenna terminal and a reception terminal,
At least one of the transmission filter and the reception filter is a ladder type filter including one or more series resonators and one or more parallel resonators,
At least one of the one or more series resonators and the one or more parallel resonators is divided into two resonators, and the two resonators are the first piezoelectric thin film resonator and the first resonator. The acoustic wave device according to claim 1, wherein the acoustic wave device is the second piezoelectric thin film resonator.

Images