JP4384306B2 - Piezoelectric resonator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric resonator used in a cellular phone, a wireless LAN, and the like, and more particularly to a piezoelectric resonator using resonance of a thickness longitudinal vibration of a piezoelectric body.
[0002]
[Prior art]
In the field of electronic devices, the frequency of radio communication and electric circuits is becoming higher, and along with this, filters used for these electric signals are also required to support high frequencies. Development is underway.
[0003]
Recently, the development of a resonator called a bulk acoustic wave resonator (BAWR) is in progress. This is a resonator using the fact that the vibration of the piezoelectric thin film causes resonance in the thickness direction of the thin film with respect to the input high-frequency electric signal, and is applied to a resonator having a high resonance frequency in the GHz range. Application is expected.
[0004]
As shown in FIG. 5, the conventional BAWR includes a base 51, a support film 52 formed on the surface of the base 51, a buffer layer 53 formed on the support film 52, and the buffer layer 53. A first electrode 54 formed on the first electrode 54, a piezoelectric body 55 formed on the first electrode 54, and two second electrodes 56 formed on the piezoelectric body 55 (USP 4,320). , 365). A vibrating body 57 is configured by the first electrode 54, the piezoelectric body 55, and the second electrode 56. By applying a high frequency electric field between the first electrode 54 and the second electrode 56, the vibrating body 57 and its The buffer layer 53 formed below and the support film 52 vibrate to become a vibrating portion. The vibration portion of the support film 52 is exposed to the vibration space A.
[0005]
However, in the above-described thin film piezoelectric resonator, the vibration space A needs to be formed below the vibrating body 57 via the supporting film 52, and the supporting film 52 having sufficient strength to support the vibrating body 57 is obtained. There was a problem that it was not possible.
[0006]
Therefore, a piezoelectric resonator that does not require the use of a support film has been proposed (Japanese Patent Laid-Open No. 6-295181). As shown in FIG. 6, this piezoelectric resonator forms an acoustic reflector 64 composed of a multilayer film in which two types of reflection layers 62 and 63 having different acoustic impedances are alternately formed on a base 61. A vibrating body 68 in which a piezoelectric body 66 is sandwiched between a pair of electrodes 65 and 67 is formed on 64.
[0007]
Since the vibration generated by the vibrating body 68 is reflected by the acoustic reflector 64, the vibration energy can be confined to the vibrating body 68 and the acoustic reflector 64. Therefore, since it has a structure without a support film, there is no need to worry about the strength of the support film.
[0008]
[Problems to be solved by the invention]
However, the acoustic reflector 64 disclosed in Japanese Patent Laid-Open No. 6-295181 reflects vibration waves at the interface between two films having different acoustic impedances, for example, the interfaces between the reflective layers 62 and 63, but is not totally reflective. Part of the light is reflected and the rest is transmitted.
[0009]
Therefore, in order to increase the reflectance, two materials having different acoustic impedances must be alternately stacked. However, it is necessary to make the thickness of the reflective layers 62 and 63 constituting the acoustic reflector 64 ¼ of the frequency, which causes a problem in that it is difficult to manufacture. Further, in practice, the thickness of the reflective layers 62 and 63 varies and the reflectance decreases, so that even if the reflective layers 62 and 63 are repeatedly formed, a transmitted wave is generated. Therefore, there is a problem that energy is lost and the characteristics of the piezoelectric resonator are deteriorated.
[0010]
An object of the present invention is to provide a piezoelectric resonator that is less likely to malfunction due to breakage or deformation and that has less energy loss.
[0011]
[Means for Solving the Problems]
The piezoelectric resonator according to the present invention includes a base, a waveguide having at least two inclined surfaces, the bottom of which is in contact with the substrate, and a pair of electrodes provided on the inclined surface of the waveguide. And a vibrating body sandwiching a piezoelectric body, and the inclined surface forms an angle of approximately 45 ° with respect to the base. By adopting such a configuration, a piezoelectric resonator that does not require a support film can be provided, and the problem of breakage and deformation caused by the support film is released.
[0012]
In addition, the acoustic wave generated by the vibrating body formed on one inclined surface travels through the waveguide, is reflected at the interface between the base and the waveguide, and travels to the other inclined surface. The reflected and advanced path travels in the opposite direction to reach the inclined surface on which the vibrating body is formed. By reciprocating the acoustic wave along this path and controlling the length of one reciprocal path, it is possible to confine the acoustic wave inside the waveguide, realizing a piezoelectric resonator with less energy loss. it can.
[0013]
Here, it is preferable to provide a vibrating body on each of the pair of inclined surfaces. By adopting such a configuration, it becomes possible to increase the amplitude of the standing wave in the waveguide by synchronizing the phases of the acoustic waves emitted from the two vibrators. can get.
[0014]
In the piezoelectric resonator of the present invention, the angle at which the acoustic wave is incident on the bottom surface of the waveguide is approximately 45 °, and the reflectance is larger than that of the normal incidence, so that the energy loss is small. It is desirable that the sound speed is 2 ^1/2 times or more the sound speed in the waveguide. By adopting such a configuration, the acoustic wave is totally reflected at the interface between the waveguide and the substrate, and the energy of the acoustic wave is lost when reflected, so that the energy loss can be extremely reduced.
[0015]
Furthermore, a reflection layer that reflects acoustic waves is provided between the waveguide and the substrate, and the sound velocity in the reflection layer is 2 ^1/2 times or more the sound velocity in the waveguide. It is desirable. By adopting such a configuration, for example, by selecting a material having a large sound speed so that the sound speed in the reflection layer is 2 ^1/2 times or more the sound speed in the waveguide, a substrate having a low sound speed is obtained. Can be used, and can deal with substrates of various sound speeds.
[0016]
Here, the reflective layer is preferably made of silicon nitride, silicon carbide, or diamond. Since these materials have a high sound speed, it is possible to employ a waveguide body having a high sound speed, and the resonance frequency can be increased.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
In the piezoelectric resonator of the present invention, as shown in FIG. 1, the waveguide 3 is provided on the base 1, and the bottom surface 4 is in contact with the base 1. The waveguide 3 has at least two inclined surfaces 5a and 5b, and the angle θ between the inclined surfaces 5a and 5b and the substrate 1 is approximately 45 °. On the inclined surface 5a, a vibrating body 9 including a first electrode 6, a piezoelectric body 7, and a second electrode 8 is provided.
[0018]
Here, in the case of FIGS. 1A and 1B, two inclined surfaces are overlapped to form a triangular prism-shaped waveguide 3 whose section is a right-angled isosceles triangle and has a maximum area. A bottom surface 4 which is a surface is in contact with the base 1. Therefore, the inclined surfaces 5 a and 5 b, that is, the exposed side surfaces of the waveguide 3 form an angle of approximately 45 ° with the substrate 1.
[0019]
As shown in FIG. 1 (c), a part of the waveguide including the apex angle of the right triangle in FIG. 1 (a) may be removed in parallel with the substrate surface.
[0020]
Further, it is desirable that the angle θ formed by the inclined surfaces 5a and 5b of the waveguide 3 with the base body 1 is precisely 45 ° so that the acoustic wave reciprocates along the same path inside the waveguide and resonates. . However, in actual manufacturing, if the angle is set within a range that does not deteriorate the resonance characteristics, resonance is maintained and there is substantially no problem. That is, the angle θ between the inclined surfaces 5a and 5b of the waveguide 3 and the base 1 is in the range of 42.5 to 47.5 °, preferably 44 to 46 °, and the left-right symmetry is maintained. Preferably it is.
[0021]
Here, the waveguide 3 can form a thin film by a technique such as sputtering or CVD, and can form an inclined surface by processing. In this processing, for example, mechanical processing or anisotropic etching is used to form a V-shaped groove, and an inclined surface having an angle of about 45 ° with respect to the surface of the substrate 1 can be formed. The height h of the waveguide 3 is preferably 10 μm or less, particularly preferably 5 μm or less in order to achieve a resonance frequency of 1 GHz or more.
[0022]
The piezoelectric body 7 can be formed by a sol-gel method, a gas phase synthesis method represented by a sputtering method, or the like. The thickness of the piezoelectric body 7 is preferably 1 μm or less, although it depends on the frequency band of the resonator used. This is to obtain a resonance frequency of 1 GHz or more by thickness longitudinal vibration.
[0023]
The first electrode 6 and the second electrode 8 are obtained by a vapor phase synthesis method such as a CVD method, a sputtering method, or a vacuum evaporation method, but the CVD method represented by the MOCVD method or the like has a complicated shape. Since relatively good film thickness uniformity is obtained, it is particularly preferable. The thickness of the electrode is preferably 0.05 to 0.3 μm, and particularly preferably 0.1 to 0.2 μm.
[0024]
In addition, it goes without saying that a pair of extraction electrodes 10 is formed and used for electrical connection between the first electrode 6 or the second electrode 8 and the external electrode. For example, as shown in FIG. 1B, the first electrode 6 and the second electrode 8 are respectively connected to a pair of extraction electrodes 10 to enable external input.
[0025]
The substrate 1 is made of silicon or sapphire, and has sufficient flatness and surface roughness such that the acoustic wave is totally reflected on the surface of the substrate, for example, a flatness of 5 μm or less and a surface roughness of Ra 0.1 μm or less. The material is not particularly limited. In particular, it is desirable that the sound speed in the substrate 1 be 2 ^1/2 times or more the sound speed in the waveguide 3.
[0026]
This is because the condition of total reflection at the interface between the substrate 1 and the waveguide 3 (hereinafter referred to as total reflection condition) is given by the ratio of the sound velocity in the substrate 1 and the sound velocity in the waveguide 3. ^Because more than ^1/2 is necessary. For example, the sound velocity in the substrate refers to the velocity of an acoustic wave traveling in the substrate.
[0027]
The waveguide 3 can be determined in consideration of the total reflection condition. For example, when SiO ₂ is used as a waveguide and silicon nitride is used as the substrate 1, the total reflection condition is satisfied and vibration energy can be confined in the waveguide 3.
[0028]
In addition, if a resonator is formed using a piezoelectric material other than a ferroelectric material such as ZnO or AlN as the piezoelectric material 7, a large-sized resonator cannot be realized. A ferroelectric having a large relative dielectric constant is suitable.
[0029]
In particular, a ferroelectric thin film having a perovskite type structure such as Pb (Zr _1-x Ti _x ) O ₃ has a large spontaneous polarization and can provide a large piezoelectricity, and a piezoelectric material other than the ferroelectric material ZnO Since the relative dielectric constant is about 100 times larger than that of AlN and the electrode area, which is one of the factors determining impedance, can be reduced to about 1/100, the size of the resonator can be reduced.
[0030]
Examples of the ferroelectric having a perovskite structure include Pb (Zr _1-x Ti _x ) O ₃ , PbTiO ₃ , and BaTiO ₃ . Further, a ferroelectric thin film other than the perovskite structure, for example, Sr ₂ KNb ₅ O ₁₅ having a tungsten bronze structure can be used.
[0031]
Among the ferroelectric materials, those having a basic composition of Pb (Zr _1-x Ti _x ) O ₃ are particularly preferable. This is because Pb (Zr _1-x Ti _x ) O ₃ as a basic composition exhibits large piezoelectricity and relative dielectric constant even when it is a thin film.
[0032]
The first electrode 6 and the second electrode 8 may be made of a metal material such as Al or Au that has been conventionally used. Al is desirable because the mass load on the piezoelectric body 7 is small and it is difficult to suppress piezoelectric vibration, and the electrical resistivity is small and the Q value of the resonator is small. Note that a thin film of titanium or the like may be formed between the waveguides in order to improve the adhesion of the electrode of Al or the like.
[0033]
In the piezoelectric resonator of the present invention configured as described above, the vibrating body 9 vibrates in the thickness direction of the vibrating body 9, that is, in the direction perpendicular to the inclined surface 5 a of the waveguide 3, and the generated vibration is acoustic. It is confined inside the waveguide 3 as a wave and resonates.
[0034]
More specifically, as indicated by the arrow, the acoustic wave generated by the vibration generated in the vibrating body 9 travels along the waveguide 3 and is reflected at the interface between the base 1 and the waveguide 3. It reaches another inclined surface 5b that is not formed. Since reflection at the interface between the substrate 1 and the waveguide 3 is total reflection, there is no energy loss at the time of reflection unlike the conventional reflector. This acoustic wave travels in the reverse direction after reflection on the inclined surface 5b and returns to the vibrating body.
[0035]
Therefore, the acoustic wave is emitted from the inclined surface 5a, reflected by the bottom surface 4, and reaches the inclined surface 5b. And after reflecting on the inclined surface 5b, it reflects on the bottom face 4, and returns to the inclined surface 5a. This round trip is repeated, but resonance occurs when the length of one round trip of the acoustic wave is an integral multiple of a half wavelength of the propagating acoustic wave.
[0036]
For this reason, as in the prior art, it is not necessary to provide a vibration space in order to increase the resonance frequency and prevent vibration attenuation, so that a structure without a support film is possible, and problems such as cracks in the support film are considered. There is no need. In addition, since there is no loss in the reflective layer, excellent characteristics as a piezoelectric resonator can be maintained.
[0037]
FIG. 2 shows another example of the present invention, in which a reflective layer 12 is provided on a substrate 11, a waveguide 13 is provided on the reflective layer 12, and its bottom surface 14 is in contact with the reflective layer 12. . The waveguide 13 has at least two inclined surfaces 15a and 15b, and an angle θ formed by the inclined surfaces 15a and 15b with respect to the reflective layer 12 is approximately 45 °. Furthermore, a vibrating body 19 including a first electrode 16, a piezoelectric body 17, and a second electrode 8 is provided on the inclined surface 15 a of the waveguide body 13. It is desirable that the sound speed in the reflective layer 12 is 2 ^1/2 times or higher than the sound speed in the waveguide 13.
[0038]
By adopting this structure, there is no restriction on the speed of sound of the base 11, so that the material selection range of the base 11 is widened, and various materials can be used. For example, a suitable silicon substrate can be selected as the material of the substrate 11 in consideration of surface flatness and uniformity of characteristics.
[0039]
On the other hand, the reflection layer 12 and the waveguide 13 need to be combined in consideration of the total reflection condition. In consideration of process consistency and ease of manufacture, a combination using silicon nitride for the reflective layer 12 and amorphous SiO ₂ for the waveguide 13 is desirable.
[0040]
In consideration of the resonator characteristics, a combination using a diamond thin film for the reflective layer 12 and a silicon nitride thin film for the waveguide 13 is preferable. Here, since the frequency is proportional to the sound speed, the resonance frequency can be greatly increased by using silicon nitride whose sound speed is as large as twice or more that of amorphous SiO ₂ .
[0041]
FIG. 3 shows another example of the present invention, in which a waveguide 23 is formed on a base 21, and a bottom surface 24 of the waveguide 23 is in contact with the base 21. The waveguide 23 has at least two inclined surfaces 25a and 25b, and an angle θ between the inclined surfaces 25a and 25b and the bottom surface 24 is approximately 45 °. On the two inclined surfaces 25a, b of the waveguide 23, a vibrating body 29a, a first electrode 26b, a piezoelectric body 27b, a first electrode 26a, a piezoelectric body 27a, and a second electrode 28a, A vibrating body 29b including two electrodes 28b is provided.
[0042]
Therefore, when the acoustic wave emitted from the vibrating body 29a formed on one inclined surface 25a travels through the waveguide 23 and reaches the other side surface 25b, the acoustic wave reaches the inclined surface portion. In order to increase the output strength, it is desirable that the vibrating body 29b is disposed at least partially.
[0043]
FIG. 4 shows still another example of the present invention. That is, the reflective layer 32 is provided on the base 31 and the waveguide 33 is formed thereon. The waveguide 33 has a bottom surface 34 in contact with the reflective layer 32 and has two inclined surfaces 35a and 35b. In addition, on the two inclined surfaces 35a and b of the waveguide 33, a vibrating body 39a including a first electrode 36a, a piezoelectric body 37a, and a second electrode 38a, a first electrode 36b, a piezoelectric body 37b, and a second electrode are provided. A vibrating body 39b including the electrode 38b is provided.
[0044]
Also here, when the acoustic wave emitted from the vibrating body 39a formed on the inclined surface 35a travels through the waveguide 33 and reaches the other inclined surface 35b, at least the inclined surface portion to which the acoustic wave has reached has been reached. In order to increase the output strength, it is desirable that the vibrating body 39b is partially disposed.
[0045]
【Example】
Example 1
1 (c) using a 4-inch φ silicon (100) wafer for the substrate 1, amorphous SiO ₂ for the waveguide 3, Al for the first electrode 6 and second electrode 8, and PZT for the piezoelectric 7. A piezoelectric resonator having the structure shown in FIG.
[0046]
First, after cleaning the wafer by the RCA method, an SiO ₂ thin film having a film thickness of 10 μm was formed by RF sputtering at an RF output of 350 W and a substrate temperature of 400 ° C.
[0047]
The sound speed in the obtained SiO ₂ thin film was calculated based on the result of hardness measurement. The sound velocity in the wafer was 8.4 km / s, and the sound velocity in the SiO ₂ thin film was 4.7 km / s. Therefore, the sound speed in the wafer was 1.8 times the sound speed in the SiO ₂ thin film, and the total reflection condition was satisfied.
[0048]
Next, V-shaped grooves were formed in the amorphous SiO ₂ thin film by cutting. The angles formed by the inclined surfaces 5a and 5b of the waveguide 3 with respect to the substrate were 45.5 °, respectively. At this time, the height h of the waveguide 3 was 10 μm.
[0049]
Further, an Al thin film having a film thickness of about 0.3 μm was formed as the first electrode 6 by MOCVD using Al (C ₂ H ₅ ) ₃ as a source gas, and unnecessary portions were removed.
[0050]
On the first electrode 6, PZT having a film thickness of about 0.4 μm was formed as the piezoelectric body 7 by MOCVD using TiO (DPM) ₂ , Zr (DPM) ₄ , and Pb (DPM) ₂ as raw materials. DPM is dipivaloylmethanato.
[0051]
Then, an Al thin film was produced as the second electrode 8 on the piezoelectric body 7 by the same method as that for the first electrode 6, and unnecessary portions were removed. The film thickness is about 0.3 μm.
[0052]
Finally, pattern formation using a photoresist, RIE etching, and Al deposition of an extraction electrode were performed to produce a resonator. The amorphous SiO ₂ thin film including the waveguide 3 was thinned to 8 μm by CMP (Chemical Mechanical Polishing).
[0053]
As a result of measuring the high frequency characteristics of the resonator structure fabricated in this manner, a result of a basic resonance frequency of 500 MHz was obtained. The loss strength of the piezoelectric resonator was calculated from the input / output signal strength. As a result, the loss was 2.3%.
Example 2
The substrate 11 is a (100) -plane silicon wafer, the reflective layer 12 is silicon nitride, the waveguide 13 is amorphous SiO ₂ , the first electrode 16 and the second electrode 18 are Al, and the piezoelectric body 17 is Pb (Zr). A piezoelectric resonator having the structure shown in FIG. 2 was fabricated using _0.47 Ti _0.53 ) O ₃ .
[0054]
First, after cleaning the wafer by the RCA method, a silicon nitride thin film was produced by the ECR sputtering method. That is, Ar is introduced into a plasma chamber (PC) at 16 sccm and N2 is introduced at 5 sccm, and plasma is generated by a microwave having an output of 600 W, and ECR plasma satisfying electron cyclotron resonance (ECR) conditions is generated by a coil magnetic field surrounding the plasma chamber. .
[0055]
A high frequency (RF) 300 W is applied to a silicon target installed near the boundary of the deposition chamber adjacent to the PC and the silicon is sputtered and heated to 400 ° C. A silicon nitride thin film is formed by reaction. The film thickness was 2 μm.
[0056]
Subsequently, a SiO ₂ thin film was formed on the silicon nitride thin film by RF sputtering. The production conditions were an RF output of 350 W, a substrate temperature of 400 ° C., and a film thickness of 10 μm. The obtained SiO ₂ thin film was amorphous.
[0057]
The sound speed in the obtained thin film was calculated based on the result of hardness measurement. The sound velocity in the silicon nitride thin film was 10.8 km / s, and the sound velocity in the SiO ₂ thin film was 4.7 km / s. Therefore, the sound velocity in the silicon nitride thin film was 2.3 times the sound velocity in the SiO ₂ thin film, satisfying the total reflection condition.
[0058]
Next, a V-shaped groove was formed in the waveguide 13 in the same manner as in Example 1, and the SiO ₂ thin film was made 9 μm high.
[0059]
Further, the first electrode 16 was formed in the same manner as in Example 1, and the piezoelectric body 17 was formed on the first electrode 16. Pb (Zr _0.47 Ti _0.53 ) O ₃ is used as the piezoelectric body 17. The film forming method was an MOCVD method, and a thin film having a thickness of about 0.4 μm was formed using TiO (DPM) ₂ , Zr (DPM) ₄ , and Pb (DPM) ₂ . DPM is dipivaloylmethanato.
[0060]
Then, an Al thin film was produced on the piezoelectric body 17 as the second electrode 18 by the same method as the first electrode 16. The film thickness is about 0.3 μm.
[0061]
Finally, using CMP, the top of the waveguide 33 where both the inclined surfaces 15a and 15b are in contact is ground to make the SiO ₂ thin film 9 μm high. Then, pattern formation using a photoresist, RIE etching, and Al deposition of an extraction electrode were performed to produce a resonator.
[0062]
The high frequency characteristics of the fabricated resonator structure were measured, and a result of a basic resonance frequency of 530 MHz was obtained. Considering the sound velocity of amorphous SiO _{2 and} the sound velocity of the vibrating body, the vibration wave reflected by the vibrating body formed on both sides is totally reflected through the interface between the amorphous SiO ₂ layer and the silicon nitride layer. It seems that they are resonating. By using secondary and tertiary resonances, a resonator having an operating frequency of 1 GHz or more can be formed. The loss was 2.2%.
Example 3
Using a 4-inch φ silicon (100) wafer for the base 21, amorphous SiO ₂ for the waveguide 23, Al for the first electrodes 25 a and b and the second electrodes 28 a and b, and PZT for the piezoelectric bodies 28 a and b, A piezoelectric resonator having the structure shown in FIG. 3 was produced in the same manner as in Example 1.
[0063]
The high frequency characteristics of the fabricated resonator structure were measured, and a result of a basic resonance frequency of 500 MHz was obtained. The loss was 2.2%.
Example 4
The substrate 31 is a 4 inch φ (100) plane silicon wafer, the reflective layer 32 is diamond, the waveguide 33 is silicon nitride, the first electrodes 36a and 36b and the second electrodes 38a and 38b are Al, and the piezoelectric body 37a. A piezoelectric resonator having the structure shown in FIG. 4 was fabricated using Pb (Zr _0.47 Ti _0.53 ) O ₃ for b and b. The production method other than the diamond thin film was the same as in Example 2.
[0064]
The diamond thin film was produced by a plasma CVD method. As a manufacturing method and conditions, a microwave is input at 6 kw using a CH ₄ , CO ₂ , and H ₂ mixed gas under reduced pressure. The film thickness is 2 μm.
[0065]
The high frequency characteristics of the obtained resonator structure were measured, and the basic resonance frequency was 800 MHz and the loss was 2.0%. The value of the basic resonance frequency of 800 MHz is about 1.6 times larger than that of the third embodiment. This is due to the difference in sound speed between the waveguides that confine the vibration wave. That is, a resonator having a higher resonance frequency can be obtained by using a material having a higher sound speed while maintaining the ratio of the sound speed between the reflective layer and the waveguide. A resonator having an operating frequency of 1 GHz or more could be formed by using secondary or tertiary resonance.
Comparative Example First, a Si wafer was used as a substrate, and after cleaning by the RCA method, a thin film to be the acoustic reflector 64 was formed. That is, four layers of SiO ₂ film 62 and Si ₃ N ₄ film 63 were repeatedly formed on the Si substrate 61 by sputtering.
[0066]
Next, each layer of the first electrode 65, the piezoelectric body 66, and the second electrode 67 was formed on the acoustic reflector 64 by sputtering. Pt was used as the electrode material, and PZT was used as the piezoelectric material. A metal mask was used for pattern formation.
[0067]
When the high-frequency characteristics of the resonator structure fabricated in this way were measured, a result that the resonance frequency of the fundamental wave was 450 MHz was obtained. The loss was 5.5%.
[0068]
【The invention's effect】
The piezoelectric resonator of the present invention requires a support film because the acoustic wave travels in a waveguide having an inclined surface that forms an angle of 45 ° with the substrate and uses total reflection and resonance on the substrate surface. Therefore, it is not necessary to consider the damage of the element due to insufficient strength of the support film, and efficient vibration confinement can be realized by utilizing total reflection of vibration waves, and a large resonance frequency can be obtained with low loss.
[Brief description of the drawings]
FIG. 1 shows a piezoelectric resonator of the present invention, in which (a) is a cross-sectional view, (b) is a perspective view, and (c) is a cross-sectional view.
FIG. 2 is a cross-sectional view showing another piezoelectric resonator of the present invention.
FIG. 3 is a cross-sectional view showing another piezoelectric resonator of the present invention.
FIG. 4 is a cross-sectional view showing still another piezoelectric resonator according to the present invention.
FIG. 5 is a cross-sectional view showing a basic structure of a conventional piezoelectric resonator.
FIG. 6 is a perspective view showing another conventional piezoelectric resonator.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Base | substrate 3 ... Waveguide 4 ... Bottom 5a, 5b ... Inclined surface 6 ... 1st electrode 7 ... Piezoelectric body 8 ... 2nd electrode 9 ... Vibration body

Claims (5)

A base body, a waveguide having a bottom surface in contact with the base body and a pair of inclined surfaces formed at an angle of about 45 ° with respect to the bottom surface, and a pair of inclined surfaces provided on the waveguide body; And a vibrating body having a piezoelectric body sandwiched between the electrodes. 2. The piezoelectric resonator according to claim 1, wherein a vibrating body is provided on each of the pair of inclined surfaces. 3. The piezoelectric resonator according to claim 1, wherein the sound velocity in the substrate is 2 ^1/2 times or more the sound velocity in the waveguide. A reflection layer for reflecting acoustic waves is provided between the waveguide and the substrate, and the sound velocity in the reflection layer is at least 2 ^1/2 times the sound velocity in the waveguide; The piezoelectric resonator according to claim 1 or 2, characterized in that: The piezoelectric resonator according to claim 4, wherein the reflective layer is made of any one of silicon nitride, silicon carbide, and diamond.

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