JP2006246290A - Thin-film piezoelectric resonator and thin-film piezoelectric filter employing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin-film piezoelectric resonator including an absorption and/or transmission spectrum that does not contain an irregular component such as spike caused by transverse mode vibration. <P>SOLUTION: The thin-film piezoelectric resonator includes a first dielectric layer having a first face and a second face, a lower electrode constituted of a conductive layer on the first face, and an upper electrode constituted of a conductive layer on the second face. The lower electrode and the upper electrode overlap with each other in at least a portion with the first dielectric layer in between and form a piezoelectric vibration area together with the piezoelectric layer held between the lower electrode and the upper electrode. A second piezoelectric layer is further formed at least on the upper electrode or on the lower electrode so as to cover the piezoelectric vibration area, and no electrode is included on the face of the second piezoelectric layer confronted with the upper electrode or the lower electrode. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thin film piezoelectric resonator used in communication equipment and the like and a thin film piezoelectric filter using the same.

  In order to keep the cost and size of electronic devices lower, there is always a need for smaller filter elements. In consumer electronic devices such as mobile phones and small radios, strict restrictions are imposed on both the size and cost of the components used therein. On the other hand, many such devices utilize filters that must be precisely tuned in frequency. Thus, efforts have been made to supply cheaper and more compact filter units.

  Some filter elements that have the ability to meet these needs are made from acoustic resonators. As a filter element made from these acoustic resonators, there is a thin film piezoelectric resonator using bulk longitudinal acoustic waves in a piezoelectric layer. In one simple configuration, the piezoelectric layer is sandwiched between two metal electrodes. This sandwich structure is placed in a state that does not prevent vibration by supporting the outer periphery thereof. When an electric field is created between the two electrodes by applying a voltage, the piezoelectric layer converts some of the electrical energy into mechanical energy in the form of sound waves. Sound waves propagate longitudinally in the same direction as the electric field and are reflected at the electrode / air interface, or propagate across the electric field and are reflected at various breaks at the end of the electrode or its structure. At this time, even if the sandwich structure is a laminated structure in which a plurality of layers are stacked, the same is true even if the place to be supported is an acoustic mirror layer constituted by a plurality of layers having different acoustic impedances rather than in the air.

  This type of thin film piezoelectric resonator is a mechanical resonator that can be electrically coupled, and has a filter function when combined. The mechanical resonance frequency for a given phase velocity with sound traveling through the material is the frequency at which the half wavelength of the acoustic wave traveling longitudinally through the device is equal to the total thickness of the device. Since the speed of sound is four orders of magnitude lower than the speed of light, the resonator can be made quite small. Resonators used for applications in the GHz range can be made with physical dimensions less than 300 microns in diameter and several microns in thickness.

  A thin film piezoelectric resonator using bulk longitudinal acoustic waves in a piezoelectric layer has a piezoelectric layer with a thickness of about 1 to 2 μm at the center, and has a structure in which the upper and lower sides of the piezoelectric layer are sandwiched between electrodes. An electric field is created through the piezoelectric layer by applying a voltage to the electrodes. Then, part of the electric field is converted into a mechanical field. In this way, the thin film piezoelectric resonator acts as a resonator according to the mechanical resonance frequency for a predetermined phase velocity with sound transmitted through the material.

  This type of thin film piezoelectric resonator is disclosed in, for example, Patent Document 1 and Patent Document 2.

JP 2000-332568 A JP 2002-372974 A

  Regarding the fundamental vibration mode in the thin film piezoelectric resonator, whether the sound wave is a compression wave, a shear wave, or a Lamb wave, it propagates in a direction perpendicular to the electrode surface. However, there are other vibration modes that can be excited. These vibration modes correspond to sound waves that move in parallel with the electrode surface and are reflected at the wall of the piezoelectric vibration region or the cut off portion at the end of the electrode layer. This mode is called a transverse mode, and its resonance frequency is determined by the acoustic velocity of the transverse resonance mode of the piezoelectric layer and the lateral dimension of the metal electrode layer. Although the fundamental frequency of these modes is significantly lower than that of the fundamental mode, higher harmonics of these transverse modes may appear in the fundamental mode frequency band. These harmonics cause a plurality of spikes in the absorption spectrum of the thin film piezoelectric resonator, which is a problem.

  The present invention has been made to solve the above problems. That is, an object of the present invention is to provide a thin film piezoelectric resonator having an absorption and / or transmission spectrum that does not include irregular components such as spikes caused by transverse mode vibration.

  The present invention provides a first piezoelectric layer having a first surface and a second surface, a lower electrode composed of a conductive layer on the first surface, and a conductive layer on the second surface. A thin film piezoelectric resonator having an upper electrode made of a layer, wherein the lower electrode and the upper electrode overlap at least partly with the first piezoelectric layer interposed therebetween, and the lower electrode and the upper electrode A piezoelectric vibration region is formed together with the sandwiched piezoelectric layer, and a second piezoelectric layer is further formed on at least the upper electrode or the lower electrode so as to cover the piezoelectric vibration region. The present invention relates to a thin film piezoelectric resonator having no electrode on a surface of the piezoelectric layer facing the upper electrode or the lower electrode.

  One embodiment of the thin film piezoelectric resonator of the present invention is characterized in that the first piezoelectric body and the second piezoelectric body are made of the same material.

  In the thin film piezoelectric resonator of the present invention, it is preferable that the thickness of the second piezoelectric layer is 25 to 35% of the thickness of the first piezoelectric layer. Moreover, it is preferable that the thickness of the second piezoelectric layer is 1.0 to 1.8 times the thickness of the upper electrode.

  The present invention also relates to a thin film piezoelectric filter using a plurality of the piezoelectric thin film resonators of the present invention.

  According to the present invention, a thin film piezoelectric resonator having an absorption and / or transmission spectrum that does not include an irregular component generated by a transverse mode by adding a simple method to a resonator having a piezoelectric vibration region in which the transverse mode is a problem according to the present invention. Can be provided.

  Hereinafter, the present invention will be described with reference to the drawings. FIG. 1A is a schematic cross-sectional view of a thin film piezoelectric resonator 10 showing an embodiment of the thin film piezoelectric resonator of the present invention. As shown in FIG. 1A, an embodiment of the thin film piezoelectric resonator of the present invention includes a piezoelectric layer 12 having a first surface and a second surface, and a conductive layer on the first surface. A lower electrode 11 made of a layer and an upper electrode 13 made of a conductive layer on the second surface are provided. The piezoelectric layer 12 having electrodes on both sides is usually formed on a substrate 16 having a cavity 15, and a part thereof is in contact with air. Further, a part of the lower electrode 11 overlaps at least a part of the upper electrode 13 with the piezoelectric layer 12 interposed therebetween to form a piezoelectric vibration region 17. That is, the piezoelectric vibration region 17 is a region where the electrodes 11 and 13 are present on both surfaces of the piezoelectric layer 12 and resonance occurs in the thickness direction of the piezoelectric layer 12 when a voltage is applied. As seen from the above, the lower electrode 11 and the upper electrode 13 overlap each other. However, the wiring to the lower electrode 11 or the upper electrode 13 is not substantially included. The thin film piezoelectric resonator of the present invention is characterized in that a second piezoelectric layer 14 is further formed on at least the upper electrode 13 or the lower electrode so as to cover the piezoelectric vibration region 17. In the embodiment of FIG. 1, the second piezoelectric layer 14 is formed on the upper electrode. However, in the thin film piezoelectric resonator of the present invention, the second piezoelectric layer 14 is formed on the lower electrode on the side different from the first piezoelectric layer. A second piezoelectric layer may be formed. Further, the second piezoelectric layer may be formed on both the upper electrode and the lower electrode. However, since the periphery of the lower electrode is fixed by the substrate, and the upper electrode has a higher degree of freedom than the lower electrode, the lateral mode vibration is suppressed by forming the second piezoelectric layer on the upper electrode. The effect is large and preferable. Hereinafter, the piezoelectric thin film resonator in which the second piezoelectric layer is formed on the upper electrode will be described, but the present invention is not limited to this. Note that the piezoelectric thin film resonator of the present invention is a resonator different from a stacked crystal filter (SCF) in which a plurality of resonators are stacked, and thus faces the upper electrode or the lower electrode of the second piezoelectric layer. There are no electrodes on the surface.

  FIG. 1B is a schematic plan view showing the shape of the piezoelectric vibration region 17 (hereinafter referred to as the shape of the piezoelectric vibration region) viewed from the thickness direction of the piezoelectric layer of the thin film piezoelectric resonator. The shape of the piezoelectric vibration region 17 is illustrated in FIG. 1B as a rectangle including parallel straight lines having the same length, but is not particularly limited to this rectangle. Conventionally, with regard to the shape of this piezoelectric vibration region, particularly when it is a polygon including parallel straight lines, the thin film piezoelectric resonator has a problem that it has an absorption and / or transmission spectrum including an irregular component due to transverse mode vibration. For this reason, the shape of the piezoelectric vibration region as shown in FIG. 2 having no parallel sides has been proposed. However, in the shape of the piezoelectric vibration region as shown in FIG. 2, there are design restrictions such as the arrangement of the resonators, and there is a problem such as a large loss that adversely affects the characteristics because the mounting density does not increase. .

  In the thin film piezoelectric resonator of the present invention, the second piezoelectric layer 14 is further formed on at least the upper electrode 13 so as to cover the piezoelectric vibration region 17, thereby suppressing the transverse mode vibration and preventing the transverse mode vibration. It has the characteristic of having a good absorption and / or transmission spectrum free of regular components (spikes). By forming such a thin film piezoelectric resonator, it is possible to provide a resonator and a filter that are small and easy to manufacture.

  Hereinafter, the transverse mode of vibration that is the cause of the occurrence of spikes will be described with reference to FIG. A conventional thin film piezoelectric resonator in which the shape of the piezoelectric vibration region, which is the overlapping portion 30 of the lower electrode and the upper electrode serving as the piezoelectric vibration region, is rectangular will be described. The rectangle is composed of two sets of two parallel sides, so that even if transverse mode vibration occurs from any point, it is reflected at one point on the parallel side and returns to the same point. For example, a transverse mode wave generated from the boundary point 31 of the piezoelectric vibration region is reflected by the facing side through the propagation path 32 and returns to the path 32 again. That is, the path length is 2W. Similarly, the transverse mode generated from the boundary point 33 of the piezoelectric vibration region is reflected by the opposite side through the path 34 having the path length W and returns again to the path 34, so that the path length is 2W. Thus, spikes are generated by the presence of transverse mode vibration having the same frequency on the outer periphery.

  4A and 4B are explanatory views of the transverse mode vibration control of the thin film piezoelectric resonator of the present invention. FIG. 4A is a schematic cross-sectional view of the thin film piezoelectric resonator, and FIG. It is an enlarged view. The shape of the piezoelectric vibration region of the thin film piezoelectric resonator of the present invention is not particularly limited, and may be a rectangle including parallel straight lines having the same length as shown in FIG. The thin film piezoelectric resonator of the present invention has a structure in which the upper electrode is sandwiched between two piezoelectric layers as shown in FIG. 4A, and the surface of the upper electrode as shown in FIG. 4B. It is considered that the transverse mode vibration occurs in the upper electrode surface, but the transverse mode vibration generated near the upper electrode surface is canceled by the upper and lower piezoelectric layers. As a result, it is considered that the occurrence of spikes is suppressed by making it difficult for resonance or standing waves due to transverse mode vibration having the same frequency on the outer periphery to exist.

  In the thin film piezoelectric resonator of the present invention, there are no particular restrictions on the components, but examples of the material for the piezoelectric layer include zinc oxide (ZnO) and aluminum nitride (AlN). In particular, aluminum nitride (AlN) is preferable in that it has a high sound speed and a small frequency fluctuation / film pressure fluctuation, so that it is excellent in mass productivity and has a temperature coefficient of less than half that of ZnO.

  In addition, examples of the lower electrode and the upper electrode include molybdenum (Mo), platinum (Pt), aluminum (Al), etc., but molybdenum (Mo) is relatively inexpensive and easy to handle in the manufacturing process. To preferred.

Examples of the substrate include silicon (Si), silicon oxide (SiO ₂ ), gallium arsenide (GaAs), and glass.

  The cavity of the substrate may be one in which a recess is formed in the substrate, or one in which a space is formed by etching or the like from the back surface of the substrate. Further, the hollow portion may be replaced with one in which material layers 55 having different acoustic impedances are alternately stacked as shown in FIG. Moreover, the thin film piezoelectric resonator of the present invention may be a laminated resonator having a plurality of electrode layers and piezoelectric layers, and may have a structure in which the piezoelectric layer of the present invention is formed on the top.

  In the thin film piezoelectric resonator according to the aspect of the invention, it is preferable that the first piezoelectric body and the second piezoelectric body are made of the same material. This is because waves generated near the electrode surface are more easily canceled when the sound speed of the transverse mode of the physical properties of the piezoelectric body is equal.

  In the thin film piezoelectric resonator of the present invention, it is preferable that the thickness of the second piezoelectric layer is 25 to 35% of the thickness of the first piezoelectric layer. If the thickness of the second piezoelectric layer is less than 25% of the thickness of the first piezoelectric layer, spike noise due to the occurrence of a transverse mode near the electrode surface is not sufficiently suppressed, and the thickness of the second piezoelectric layer is too small. This is because when the thickness of the first piezoelectric layer is more than 35% of the thickness, spike noise is suppressed, but the piezoelectric characteristics deteriorate.

  Furthermore, in the thin film piezoelectric resonator of the present invention, it is preferable that the thickness of the second piezoelectric layer is 1.0 to 1.8 times the thickness of the upper electrode. If the thickness of the second piezoelectric layer is less than 1.0 times the thickness of the upper electrode, the suppression of spike noise due to the occurrence of transverse modes near the electrode surface is not sufficient, and the thickness of the second piezoelectric layer is too small. This is because if the thickness of the upper electrode is greater than 1.8 times, spike noise is suppressed, but the piezoelectric characteristics deteriorate.

The thin film piezoelectric resonator of the present invention can be manufactured in the same manner as a conventionally known manufacturing method such as Patent Document 1 and Patent Document 2. For example, on the substrate made of silicon (Si), silicon oxide (SiO ₂ ), gallium arsenide (GaAs), glass, etc., the bottom made of molybdenum (Mo), platinum (Pt), aluminum (Al), etc. Electrode (lower electrode or upper electrode) is deposited by a vapor deposition method such as sputtering, and a piezoelectric material such as zinc oxide (ZnO) or aluminum nitride (AlN) is deposited by a vapor deposition method such as sputtering, and molybdenum (Mo). A top electrode (upper electrode or lower electrode) made of platinum (Pt), aluminum (Al) or the like is deposited by a vapor deposition method such as sputtering, and a piezoelectric material such as zinc oxide (ZnO) or aluminum nitride (AlN) is deposited. Thin film piezoelectric resonators are manufactured by depositing materials by vapor deposition such as sputtering. It is. At this time, the lower layer of the bottom electrode is a hollow region or molybdenum (Mo) having high acoustic impedance, tungsten (W), silicon (Si) having low acoustic impedance, silicon oxide (SiO ₂ ), aluminum (Al). Is an acoustic mirror layer composed of layers alternately stacked.

  The thin film piezoelectric filter of the present invention is a filter using the thin film piezoelectric resonator of the present invention. As one of the filter structures, a plurality of resonators as shown in FIG. There is a ladder type filter in which resonators 64, 66, and 68 connected in parallel with the resonators 63, 65, and 67 are arranged in a ladder shape. Such a filter can be manufactured by forming a plurality of piezoelectric thin film resonators on one substrate so as to have the circuit configuration of the ladder type filter.

Example 1
The thin film piezoelectric resonator shown in FIG. 7 was manufactured using the materials and thicknesses shown in Table 1. At that time, the shape of the piezoelectric vibration region was a square having a side of 180 μm. The resonance frequency was set to about 1.9 GHz.

  FIG. 7 shows a partial cross-sectional view of the manufactured thin film piezoelectric resonator.

First, as shown in FIG. 7, about 1 μm of SiO ₂ was formed on the surface of the Si substrate 76 as the insulating layer 77 by thermal oxidation. Subsequently, 50 nm of Ti was deposited on the insulating layer 77 by a sputtering method as a preliminary layer for forming a cavity. This was patterned by etching in accordance with the shape of the piezoelectric vibration region of the thin film resonator. The Ti layer is not shown in the figure because it is much thinner than the other thin film layers.

  Subsequently, about 300 nm of Mo was deposited as the lower electrode 71 by sputtering, and patterning was performed by etching to obtain a desired shape. Subsequently, AlN was used as the piezoelectric material, and AlN was deposited by about 1200 nm by a sputtering method to form the first piezoelectric layer 72, and patterning was performed by etching to obtain a desired shape. Subsequently, about 300 nm of Mo was deposited as the upper electrode 73 in the same manner as the Mo of the lower electrode, and patterning was performed.

  Subsequently, in order to suppress transverse mode noise, AlN was deposited as a second piezoelectric layer 74 by a method similar to that for AlN of the first piezoelectric layer 340 nm, followed by patterning.

  Subsequently, 4 to 5 through-holes 79 of about 10 μmφ per resonator were opened by etching from the second piezoelectric layer 74 to Ti of the cavity forming preliminary layer.

  Subsequently, the etching solution is injected into the cavity formation preliminary layer through the through-hole 79 to remove Ti of the cavity formation preliminary layer, and the insulating layer in contact with the pattern is removed in a pattern shape in the vertical direction. Thus, the cavity layer 75 was formed under the first electrode, and the thin film piezoelectric resonator 70 according to the present invention was obtained. The pass characteristics of the resonator thus obtained are shown in FIG. It was not affected by transverse mode vibrations in the piezoelectric vibration region, and excellent resonator characteristics with suppressed irregular components such as spikes could be obtained. Note that the thickness of the second piezoelectric layer of the thin film piezoelectric resonator obtained in this example is 29.3% of the first piezoelectric layer, which is 1.17 times that of the upper electrode.

(Comparative Example 1)
A thin film piezoelectric resonator was fabricated in the same manner as in Example 1 except that the second piezoelectric layer was not formed. The pattern shape of the resonator and the film thickness of each layer of the configuration are the same as in Example 1 (Table 1). The pass characteristics of the obtained resonator are shown in FIG. Compared with the thin-film piezoelectric resonator of the present invention shown in FIG. 8, irregular components such as spikes were included, and preferable characteristics could not be obtained.

(Example 2)
A thin film piezoelectric resonator was fabricated in the same manner as in Example 1 except that the thickness of the second piezoelectric layer was as thin as 150 nm. The pattern shape of the resonator and the film thickness of each layer of the configuration are the same as in Example 1 (Table 1). The pass characteristics of the obtained resonator were good pass characteristics with suppressed irregular components such as spikes compared with the pass characteristics of Comparative Example 1 shown in FIG. It was observed. Note that the thickness of the second piezoelectric layer of the thin film piezoelectric resonator obtained in this example is 29.3% of the first piezoelectric layer, which is 0.51 times that of the upper electrode.

(Example 3)
A thin film piezoelectric resonator was fabricated in the same manner as in Example 1 except that the thickness of the second piezoelectric layer was 600 nm. The pattern shape of the resonator and the film thickness of each layer of the configuration are the same as in Example 1 (Table 1). The pass characteristics of the obtained resonator did not contain irregular components such as spikes as in Example 1. The piezoelectric characteristic (electromechanical coupling coefficient Kt2) tended to be slightly smaller than that of Example 1. Note that the thickness of the second piezoelectric layer of the thin film piezoelectric resonator obtained in this example is 29.3% of the first piezoelectric layer, which is 2.07 times that of the upper electrode.

Example 4
Filters using the thin film piezoelectric resonators of the ladder circuit of FIG. At that time, the shape of the piezoelectric vibration region was a rectangle having one side in a range of 100 to 180 μm. The resonance frequency was set to about 1.9 GHz.

FIG. 10 shows a partial cross-sectional view of the filter made of the manufactured thin film piezoelectric resonator. First, as shown in FIG. 10, about 1 μm of SiO ₂ was formed on the surface of the Si substrate 96 as an insulating layer 97 by thermal oxidation. Subsequently, Ti was deposited by sputtering to a thickness of 50 nm on the insulating layer 97 as a cavity formation preliminary layer for forming a cavity (not shown). This was patterned by etching in accordance with the piezoelectric vibration region shape of each thin film resonator.

  Subsequently, about 300 nm of Mo was deposited as the lower electrode 91 by sputtering, and patterning was performed by etching to obtain a desired shape. Subsequently, AlN was used as the piezoelectric material, and AlN was deposited to a thickness of about 1200 nm by a sputtering method to form the first piezoelectric layer 92, and patterning was performed by etching to obtain a desired shape. Subsequently, about 300 nm of Mo was deposited as the upper electrode 93 by the same method as that for the Mo of the lower electrode, and patterning was performed. Further, in order to adjust the frequency of the shunt resonator of the ladder circuit, Mo was deposited on the shunt resonator as a frequency adjusting electrode 100 by a method similar to 45 nm.

  Subsequently, in order to suppress lateral mode noise, AlN was deposited as a second piezoelectric layer 94 at a thickness of 340 nm in the same manner as AlN of the first piezoelectric layer, and was patterned.

  Subsequently, 4 to 5 through-holes 99 having a diameter of about 10 μm per each resonator were opened from the second piezoelectric layer 94 to Ti as a cavity forming preliminary layer.

  Subsequently, an etchant is injected into the cavity formation preliminary layer from the through-hole 99 to remove Ti in the cavity formation preliminary layer, and also remove a part of the layer in contact with the cavity formation preliminary layer. A cavity layer 95 was formed under the electrode to obtain a filter 90 composed of a thin film piezoelectric resonator according to the present invention. FIG. 11 shows the pass characteristics of the filter thus obtained. Excellent filter characteristics were obtained with no influence of transverse mode vibration in the piezoelectric vibration region, and irregular components such as spikes were suppressed. The thickness of the second piezoelectric layer of the thin film piezoelectric resonator obtained in this example is 29.3% of the first piezoelectric layer, and the thickness of the upper electrode including the frequency adjustment electrode of the shunt resonator. 1.01 times the value.

(Comparative Example 2)
A ladder circuit filter using a thin film piezoelectric resonator was produced in the same manner as in Example 2 except that the second piezoelectric layer was not formed. The pattern shape of the filter, the film thickness of each layer of the configuration, and the circuit are the same as in Example 2 (Table 2). The pass characteristics of the obtained filter are shown in FIG. Compared with the filter characteristics of the present invention shown in FIG. 11, irregular components such as spikes are included, and preferable characteristics cannot be obtained.

(A) Typical sectional drawing of one Embodiment of the thin film piezoelectric resonator of this invention, (b) The typical top view which shows a piezoelectric vibration area | region. It is explanatory drawing which shows the shape of the piezoelectric vibration area | region of the conventional thin film piezoelectric resonator. It is explanatory drawing which shows the spike noise by the transverse mode of a piezoelectric vibration area | region. (A) Typical sectional drawing of thin film piezoelectric resonator of this invention, (b) It is an enlarged view of an upper electrode part. It is sectional drawing of other one Embodiment of the thin film piezoelectric resonator of this invention. It is a block diagram of the ladder type filter comprised by the thin film piezoelectric resonator by this invention. 1 is a schematic cross-sectional view of a thin film piezoelectric resonator manufactured in Example 1. FIG. FIG. 4 is a waveform diagram of pass characteristics of the thin film piezoelectric resonator manufactured in Example 1. 6 is a pass characteristic waveform diagram of a conventional thin film piezoelectric resonator obtained in Comparative Example 1. FIG. 6 is a schematic cross-sectional view of a thin film piezoelectric filter using the thin film piezoelectric resonator of the present invention obtained in Example 4. FIG. It is a filter passage characteristic waveform figure of the thin film piezoelectric filter using the thin film piezoelectric resonator of the present invention obtained in Example 4. It is a filter passage characteristic waveform diagram of a thin film piezoelectric filter using a conventional thin film piezoelectric resonator obtained in Comparative Example 2.

Explanation of symbols

10, 20, 30, 63 to 68, 70 Thin film piezoelectric resonator 11, 91 Lower electrode 12, 92 First piezoelectric layer 13, 93 Upper electrode 14, 94 Second piezoelectric layer 15, 95 Cavity region 17 Piezoelectric Vibration region 16, 96 Si substrate 31, 33 Arbitrary point 32, 34 on piezoelectric vibration region boundary Transverse mode wave propagation path 55 Acoustic mirror 79, 99 Through-hole 90 Thin film piezoelectric filter 100 Frequency adjusting Mo

Claims (5)

A first piezoelectric layer having a first surface and a second surface; a lower electrode comprising a conductive layer on the first surface; and an upper portion comprising a conductive layer on the second surface. A piezoelectric film sandwiched between the lower electrode and the upper electrode, wherein the lower electrode and the upper electrode overlap at least partially across the first piezoelectric layer. A piezoelectric vibration region is formed together with the body layer, and a second piezoelectric layer is further formed on at least the upper electrode or the lower electrode so as to cover the piezoelectric vibration region, and the second piezoelectric layer A thin film piezoelectric resonator having no electrode on a surface facing the upper electrode or the lower electrode. 2. The thin film piezoelectric resonator according to claim 1, wherein the first piezoelectric body and the second piezoelectric body are made of the same material. 3. The thin film piezoelectric resonator according to claim 2, wherein the thickness of the second piezoelectric layer is 25 to 35% of the thickness of the first piezoelectric layer. 4. The thin film piezoelectric resonator according to claim 3, wherein the thickness of the second piezoelectric layer is 1.0 to 1.8 times the thickness of the upper electrode. A thin film piezoelectric filter using a plurality of the piezoelectric thin film resonators according to claim 1.

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