JP4350445B2 - Piezoelectric resonator and filter - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to an end surface reflection type piezoelectric resonator and a filter using SH wave surface waves applied to a resonator, a filter, and the like.
[0002]
[Prior art]
Conventionally, microcomputers and the like have been frequently used for communication devices and electronic devices, and a clock oscillation circuit or the like has been connected to such microcomputers.
Here, in the oscillation circuit, as shown in the equivalent circuit shown in FIG. 9, two load capacitance components 15 (C1, C2) are connected between both ends of the piezoelectric resonance element 1 and the ground potential. A feedback resistor 13 and an inverter 14 are connected between both ends of 1.
Generally, in order to obtain stable oscillation, it is necessary to increase the P / V value of the main vibration of the piezoelectric resonant element. The P / V value is expressed by 20 × log (Ra / Rb), where Ra is defined as an anti-resonance impedance and Rb is defined as a resonance impedance.
Conventionally, in order to reduce the size of a piezoelectric resonator element as an oscillator, an end surface reflection type surface wave resonator using a surface wave or a surface wave device with a lead in which the surface wave resonator is covered with an exterior resin, etc. The structure is proposed.
[0003]
As such an end surface reflection type surface acoustic wave filter, in order to suppress spurious, a groove or a recess is provided in the piezoelectric substrate, and an IDT and a region where the groove or the recess is formed with a flexible coating layer resin. An end surface reflection type surface acoustic wave filter that covers and a coating layer partially enters a groove is disclosed (for example, see Patent Document 1).
[0004]
[Patent Document 1]
JP 2003-133888 A
[Problems to be solved by the invention]
However, in the conventional end surface reflection type surface acoustic wave filter as described above, the coating layer resin partially enters the groove, and the coating layer resin also enters the groove adjacent to the overlapping portion of the electrode finger of the IDT. As a result, there is a problem that the SH type surface wave is hardly reflected by the groove, and the P / V value of the surface wave is deteriorated.
In addition, since the amount of resin that partially enters the groove is slightly different, the reflectivity of the SH type surface wave differs depending on the groove in the groove adjacent to the overlapping portion of the electrode finger, and this tends to cause spurious. was there.
Further, since the coating layer resin partially enters the groove, a part of the resin is opened, and there is a problem that outside air easily enters from the opening and seal reliability is poor.
The present invention has been devised in view of the above-mentioned problems, and an object of the present invention is to provide a piezoelectric resonator and a filter having good SH-type surface wave reflection characteristics in a groove and high sealing reliability. With the goal.
[0006]
[Means for Solving the Problems]
The present invention is a piezoelectric resonator in which an interdigital transducer (IDT) composed of comb-teeth electrodes is formed on a part of one side main surface of a piezoelectric substrate and driven using SH type surface waves, outside of the IDT electrode fingers in one main surface of the piezoelectric substrate, grooves provided Rutotomoni for reflecting the surface wave of the SH type in parallel and adjacent to the electrode fingers, IDT of the piezoelectric substrate as opposed to the formed surface, and the not hinder the vibration of the SH type surface wave, the base substrate so that a space for housing the grooves in the adjacent portion of the overlapped portion of the electrode fingers is formed a is bonded to the piezoelectric substrate, further wherein being a synthetic resin in the groove present in the adhesive portion filled between the piezoelectric substrate and the base substrate, the grooves in adjacent parts of the parts of the electrode fingers is synthesized resin And wherein the unfilled.
[0007]
In the present invention, the piezoelectric resonator may further (1) that the groove is formed is extended to the end surface of the piezoelectric substrate,
(2) the depth of the groove is 1 wavelength (lambda) or more of the depth of the SH type surface wave,
(3) the thickness of the piezoelectric substrate is less than 320 .mu.m,
(4) to the base substrate, that the electrodes forming a capacitor are formed,
Is desirable.
[0008]
In the present invention, a plurality of interdigital transducers (IDTs) composed of comb-teeth electrodes are formed on a part of one main surface of the piezoelectric substrate, and each IDT is electrically connected to generate SH type surface waves. a filter which is driven by utilizing, on the outside of the IDT electrode fingers in one main surface of the piezoelectric substrate, grooves for reflecting the surface wave of the SH type in parallel and adjacent to the electrode fingers provided It is not Rutotomoni, so as to face the surface on which IDT is formed of the piezoelectric substrate, and does not interfere with the vibration of the surface wave of the SH type, accommodating the grooves in the adjacent portion of the overlapped portion of the electrode fingers space are bonded to the base substrate to the piezoelectric substrate so that is formed, is further synthetic resin filled in the groove present in the bonding portion between the piezoelectric substrate and the base substrate, the electrode fingers weight The grooves in the adjacent portion of the relate filter, wherein the synthetic resin is not filled.
[0009]
[Action]
According to the piezoelectric resonator of the present invention, an IDT consisting of a comb-teeth electrode is partially provided on one side main surface of the piezoelectric substrate, and an SH type surface wave is used. Therefore, the vibration part is concentrated only on one side of the piezoelectric substrate. can do. Therefore, the base substrate and the coating resin arranged for the purpose of forming and sealing a vibration space that does not hinder vibration may be arranged only on one side main surface on which the comb electrode of the piezoelectric substrate is formed, A laminated structure of two sheets of a piezoelectric substrate, a base substrate and a coating resin can be used as a basic structure, and the thickness as a piezoelectric resonator can be remarkably reduced.
In particular, in the present invention, a space for accommodating a groove in a portion adjacent to the overlapping portion of the electrode finger is formed so as to face the surface on which the IDT of the piezoelectric substrate is formed and does not disturb the vibration of the SH type surface wave. Since the base substrate and the coating resin are bonded to the piezoelectric substrate, air is present in the groove in the portion adjacent to the overlapping portion of the electrode finger without being filled with the synthetic resin. Waves can be reflected effectively, and can be uniformly reflected by the grooves, and spurious generation can be prevented without reducing the P / V value of surface waves.
In addition, since the groove existing in the bonding portion between the piezoelectric substrate and the base substrate or the coating resin other than the portion adjacent to the overlapping portion of the electrode finger is filled with the synthetic resin, the piezoelectric substrate and the base substrate The space in the base substrate and the coating resin is completely sealed by the fixing portion and the synthetic resin in the groove, and the reliability of sealing with the outside air can be improved.
[0010]
In addition, if the length of the groove constituting the reflection end surface for reflecting the SH type surface wave is longer than the overlapping length of the electrode fingers of the comb-teeth electrode, the reflection of the SH type surface wave can be further improved and spurious is generated. Can be suppressed more effectively. That is, spurious generation near the resonance and anti-resonance can be suppressed, and a large P / V value can be obtained.
Furthermore, it is possible to prevent the intrusion of moisture etc. by filling the groove in the vicinity of the end face of the piezoelectric substrate and filling the groove with the synthetic resin, and extending the groove to the end face of the piezoelectric substrate. By doing so, it is possible to reinforce that the strength of the groove portion is weakened, and to improve the sealing property and the air tightness of the vibration part region.
[0011]
Further, it is desirable that the depth of the groove constituting the reflection end face for reflecting the SH type surface wave is deeper than the wavelength λ. Thereby, the reflection of the SH type surface wave is facilitated, and spurious generation is less likely to occur.
[0012]
When using an SH type surface wave, there is a problem that the frequency of the bulk wave vibration is superimposed on the frequency of the SH type surface wave and the P / V of the SH type surface wave is significantly reduced. It is important to separate the wave frequency from the bulk wave vibration frequency.
In the present invention, by thinning the piezoelectric substrate, the frequency of the SH type surface wave is constant, but the bulk wave moves to a high frequency, so it is more possible to separate the SH type surface wave from the bulk wave vibration. It becomes possible.
Accordingly, it is desirable that the thickness of the porcelain as the piezoelectric substrate is 320 μm or less, particularly 300 μm or less. FIG. 8 shows the relationship between the resonance frequency fr and antiresonance frequency fa of the SH type surface wave and the spurious resonance frequency fb1 of the bulk wave. As the thickness of the porcelain decreases, the spurious fb1 of the bulk wave moves to the high frequency side, so that the SH type surface wave fr and fa and the spurious fb1 of the bulk wave are easily separated. Therefore, since spurious waves do not overlap between the fr and fa of the SH type surface wave and in the vicinity thereof, when applied as a piezoelectric resonator, stable oscillation can be obtained. Therefore, it can be said that a thinner piezoelectric substrate is better.
[0013]
Big electromechanical coupling coefficient of the piezoelectric substrate, a piezoelectric ceramic mainly composed of lead titanate PbTiO ₃ and lead zirconate titanate PbZrTiO ₃ and sodium niobate NaNbO _3, and easier to excite SH type surface acoustic wave A large P / V value can be obtained. In particular, suitable piezoelectric material in resonator applications, the dielectric constant has a smaller value of about 300 or less, the piezoelectric ceramic is preferable that a main component of lead titanate PbTiO ₃ and sodium niobate NaNbO _3.
[0014]
Furthermore, it is possible to form two capacitors by applying a dielectric ceramic to the base substrate of the piezoelectric resonator, and a piezoelectric resonator suitable for an oscillator having a built-in load capacitor can be obtained.
Furthermore, by providing a plurality of independent comb-teeth electrodes on one surface of the piezoelectric substrate, and changing the number of each comb-teeth electrode and adjusting the capacitance ratio, the function of a bandpass filter having an attenuation characteristic as a filter can be obtained. Can do.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
1 is an external perspective view of the piezoelectric resonator of the present invention, FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1, and FIG. 4 is an IDT formed of comb-shaped electrodes in FIG. FIG. 5 is a plan view of the surface, and is grooved in parallel to the outer surface of the electrode finger of the IDT to the end face of the porcelain.
1 to 4, reference numeral 1 is a piezoelectric resonance element, 1a is a piezoelectric substrate, 2 is a base substrate, 3 is an insulating adhesive, 4 is an external terminal, 5 is a comb electrode (IDT), and 5a and 5b are IDTs. Electrically connected lead electrodes, 6 are grooves formed in parallel with the IDT made of comb-teeth electrodes, and 8 are conductive bumps.
Since the synthetic resin may be the same as or different from the insulating adhesive 3, the filling location of the synthetic resin is commonly shown as the filling location of the insulating adhesive 3 in FIGS.
[0016]
The piezoelectric resonator of the present invention is configured by forming IDT 5 on one side main surface of piezoelectric substrate 1a, and IDT 5 is configured by a pair of comb-tooth electrodes. That is, the comb electrode is configured by forming a plurality of electrode fingers 55b in parallel on the electrode base 55a, a pair of comb electrode electrodes 55b are alternately arranged, and a pair of comb electrode electrodes 55b are arranged. The piezoelectric substrate 1a is overlapped at the center.
Lead electrodes 5a and 5b are connected to the pair of electrode bases 55a, and conductive bumps 8 are provided on the lead electrodes 5a and 5b, respectively, and are electrically connected to the external terminals 4, respectively.
In the present invention, there are grooves 6 for reflecting SH type surface waves in parallel with the electrode fingers 55b along the outermost electrode fingers 55b, in other words, on both sides of the electrode fingers 55b group. It is formed in a straight line. In the groove 6 near the end surface of the piezoelectric substrate 1a, in other words, both ends of the linear groove 6 are filled with synthetic resin, and the groove 6 in the remaining central portion is not filled at all. Furthermore, in other words, the synthetic resin 3 is filled in the groove 6 existing in the bonded portion (around the space B) between the piezoelectric resonant element 1 and the base substrate 2.
The synthetic resin 3 in the groove 6 is filled when the piezoelectric resonant element 1 and the base substrate 2 are bonded (the same as the filler). In addition, after filling the groove 6 with the synthetic resin in advance, the piezoelectric resonant element 1 and the base substrate 2 may be bonded. The adhesion region is a region from the end face of the piezoelectric substrate to a position indicated by a broken line A in FIG.
As can be understood from FIG. 4, the base substrate 2 is disposed in the piezoelectric substrate 1a so as to form a space B that does not hinder the vibration of the SH type surface wave, and the piezoelectric substrate 1a and the base substrate 2 are provided with electrodes. It is fixed so as to surround the groove 6 in the portion (resonating portion) adjacent to the overlapping portion (intersection portion) of the finger 55b. That is, the base substrate 2 is filled with the synthetic resin only at the portions located at both ends of the groove 6 formed along the overlapping portion of the electrode fingers 55b, and the portion filled with the synthetic resin is filled with the synthetic resin. The central part is not filled at all. In other words, the outer peripheral portion of the rectangular plate-shaped piezoelectric resonance element 1 is bonded to the outer peripheral portion of the rectangular plate-shaped base substrate 2, and the central portion is not bonded, and a space B is formed.
In FIG. 3, the vicinity of the end face of the groove 6 processed to the end face portion of the piezoelectric resonance element 1 can be closed by filling with synthetic resin or by applying an adhesive 3 that bonds the piezoelectric resonance element 1 and the base substrate 2. In addition, since it can be closed by forming an external terminal, the driving part of the interdigital transducer (IDT) composed of comb electrodes can be completely hermetically sealed.
[0017]
The piezoelectric substrate 1a is, PT (lead titanate), PZT (lead zirconate titanate) or a piezoelectric ceramic material such as sodium niobate NaNbO _3, lithium tantalate, lithium niobate, a single crystal material such as Yontanasan lithium Is formed. Preferably, the electromechanical coupling factor large, easy to obtain a large P / V value If it is piezoelectric ceramics mainly composed of lead titanate PbTiO ₃ and lead zirconate titanate PbZrTiO ₃ and sodium niobate NaNbO _3. Furthermore, if the resonator applications, the dielectric constant is desirable piezoelectric ceramic mainly composed of lead titanate PbTiO ₃ and sodium niobate NaNbO ₃ to be 300 or less. In this case, the thickness of the piezoelectric substrate 1a is desirably 320 μm or less, particularly 300 μm or less.
[0018]
The base substrate 2 is not particularly limited as long as it has an insulating property. For example, the base substrate 2 has a heat resistance such as a dielectric material containing barium titanate, ceramics such as an alumina substrate, polyimide, liquid crystal polymer, or the like. It is desirable to be composed of an excellent resin material.
Moreover, the material of the comb electrode can be suitably used Al, Cr, Ag, Au, Pt, Ni or the like.
Further, the groove provided on the outer side of the electrode finger of the comb-teeth electrode can be processed from the end face to the end face of the piezoelectric resonant element by a slicer processing machine, a laser processing machine, a sand blasting machine, or the like.
Here, when the electrode width of the outermost electrode finger of the comb-teeth electrode is set to a width of about λ / 8, the outermost electrode finger is formed adjacent to the groove to reflect the end face reflection of the SH type surface wave. It becomes possible to be more effective. Further, from the point of end face reflection of the surface wave, it is desirable that the length of the groove adjacent to the outside of the electrode finger is processed to be longer than the overlapping length of the electrode finger. Further, it is desirable that the depth of the groove is processed to be deeper than the wavelength λ from the point of reflection of the end face of the surface wave.
[0019]
As for the synthetic resin used for filling the groove, spurious can be effectively suppressed when the Young's modulus is 1 × 10 ¹⁰ Pa or less. Examples of such a synthetic resin include, but are not limited to, epoxy resins, silicon resins, acrylic resins, and urethane resins.
In the piezoelectric resonator configured as described above, the base substrate 2 is disposed so as to face the surface of the piezoelectric substrate 1a where the IDT 5 is formed and to form a space that does not hinder the vibration of the SH type surface wave. Since the piezoelectric substrate 1a and the base substrate 2 are fixed so as to surround the groove 6 adjacent to the overlapping portion of the electrode finger 55b, air exists in the groove 6 adjacent to the overlapping portion of the electrode finger 55b. In addition, the SH type surface wave can be effectively reflected, and the groove 6 can be reflected uniformly, and the occurrence of spurious can be prevented without reducing the P / V value of the surface wave.
Since the groove 6 in the portion where the piezoelectric substrate 1a and the base substrate 2 are bonded is filled with the synthetic resin 3, the fixing portion between the piezoelectric substrate 1a and the base substrate 2 and the synthetic resin 3 in the groove 6 are filled. Thus, the space in the base substrate 2 is completely sealed, and the sealing reliability with the outside air can be improved.
Further, the surface of the piezoelectric resonator element 1 on which the IDT 5 is formed is fixed and sealed with the base substrate 2 and the synthetic resin 3 so as to maintain a vibration space that is excited by the IDT 5 and does not suppress the SH type surface wave. Thus, a piezoelectric resonator that can be reduced in height can be obtained. Furthermore, by forming the groove 6 adjacent to the outside of the electrode finger 55b of the IDT 5, it is possible to reflect the end face of the SH type surface wave, suppress the occurrence of spurious, and increase the P / V value.
Furthermore, by using the wafer constituting the wafer and the base substrate of the piezoelectric resonator element in which a plurality of IDT5 is formed by bonding at the wafer state, high productivity enables multi-cavity, the cost Can be planned.
[0020]
In addition, by applying a dielectric material to the base substrate 2 to form a laminated structure, two load capacitors are formed, and a piezoelectric resonator having a built-in load capacitor can be obtained. Moreover, a filter can be obtained by forming an independent comb-tooth electrode and achieving electrical connection. For example, in the case of a ladder filter, the center frequency of the filter is determined by combining the resonance frequency of the piezoelectric resonance element arranged in series with the anti-resonance frequency arranged in parallel, and the guaranteed attenuation amount is arranged in a series row. A desired attenuation can be obtained by increasing the capacitance arranged in parallel to the capacitance. That is, the amount of attenuation can be increased by increasing the number of IDTs of the resonators arranged in parallel to the IDTs of the resonators arranged in series. FIG. 5 shows a ladder type filter.
Furthermore, a low-profile composite substrate can be obtained by mounting a microcomputer IC chip and a piezoelectric resonator on a circuit mother substrate.
In the above embodiment, the example in which the space B is formed using the base substrate 2 has been described. However, the space B is formed using a coating resin instead of the base substrate 2, and a groove between the coating resin and the piezoelectric substrate is formed. The same effect can be obtained even if a piezoelectric resonator is formed by filling a synthetic resin inside.
[0021]
【Example】
Example 1
A PT-based piezoelectric ceramic wafer (L = 21 mm, W = 40 mm, t = 0.2 mm) was polarized in the (L) direction, and an Au electrode was vapor-deposited on the main surface of the mirrored ceramic. A plurality of IDTs composed of comb-tooth electrodes and lead electrodes that are electrically connected to the IDTs were formed using a photolithography process. The IDT is disposed in a region corresponding to the central portion of each piezoelectric resonant element. At this time, the direction of the electrode finger of the IDT composed of comb-teeth electrodes was matched with the polarization direction. Thereafter, a groove for reflecting the SH type surface wave was formed by processing with a slicer on the outermost side of the IDT composed of comb-tooth electrodes. At this time, the number of IDT overlap electrodes was 16 pairs, and the electrode finger overlap length was 400 μm. Furthermore, the width of the electrode finger of the IDT was 15 μm, the distance between the electrode finger was 15 μm, and the metallization ratio (IDT electrode width / no electrode width between electrodes) was set to 1. The electrode width of the outermost electrode finger of the IDT electrode is λ / 8 (about 7.5 μm), the depth of the groove for reflecting the SH type surface wave is 120 μm, and the groove extends to the end face of the piezoelectric substrate The piezoelectric substrate wafer was processed as described above. Both ends of the groove were filled with an epoxy resin having a Young's modulus of 1 × 10 ⁹ Pa as shown in FIG. Thereafter, conductive bumps were printed on a part of the lead electrode portion that was electrically connected to the IDT.
[0022]
Next, an Ag electrode serving as a terminal electrode is printed and printed on both main surfaces of a wafer of a base substrate (L = 21 mm, W = 40 mm, t = 0.1 mm) based on a BaTiO ₃ system dielectric as a main component. A base substrate wafer with a built-in load capacitance (20 to 50 pF each) was fabricated. Thereafter, an epoxy resin was printed in a ring shape on the base substrate wafer so as not to face the IDT (shown in FIG. 4), and bonded and fixed so as to face the surface of the piezoelectric ceramic wafer on which the IDT was formed. . Then, it cut | disconnected with the dicing machine to the shape of each piezoelectric resonator (L = 2.0mm, W = 2.5mm, t = 0.35mm). Thereafter, an external terminal was formed by Ag sputtering, and electrical conduction between the IDT and the external terminal was performed to obtain a piezoelectric resonator as shown in FIGS.
When the impedance characteristic at this time was measured, spurious was not generated in the main frequency band as shown in FIG. 6, and the P / V value was as large as 70 dB. At this time, the capacitance of only the piezoelectric resonator is 16 pF, which is substantially equivalent to 15 pF of the resonator element used in the related art, and also in the oscillation characteristics within the range of 15 to 30 pF of the load capacity used conventionally. Stable oscillation was shown.
[0023]
Comparative Example 1
A piezoelectric resonator in which a synthetic resin having a Young's modulus of 1 × 10 ⁹ Pa is filled in the entire groove for reflecting an SH type surface wave, that is, a portion adjacent to the overlapping portion of the electrode finger, and its impedance is produced. The characteristics are shown in FIG. As can be seen from FIG. 7, the P / V value is reduced to 40 dB, which is not suitable for a resonator.
[0024]
Example 2
Next, in Example 1, the relationship between the resonance frequency fr and anti-resonance frequency fa of the surface wave and the spurious of the bulk vibration when the thickness of the piezoelectric ceramic is changed is shown in FIG. It can be seen that when the thickness of the piezoelectric ceramic is 320 μm or less, spurious vibration due to the bulk wave is not superimposed between fr and fa of the surface wave vibration. Accordingly, the thickness of the piezoelectric ceramic is desirably 320 μm or less.
[0025]
【The invention's effect】
According to the piezoelectric resonator of the present invention, the groove in the portion adjacent to the overlapping portion of the electrode finger is accommodated so as to face the surface of the piezoelectric substrate on which the IDT is formed and does not disturb the vibration of the SH type surface wave. Since the base substrate and the coating resin are provided so as to form a space to be bonded and the piezoelectric substrate, the base substrate, and the coating resin are bonded, air exists in the groove in the portion adjacent to the overlapping portion of the electrode finger, and SH The surface wave of the type can be effectively reflected and can be uniformly reflected by the groove, and spurious can be prevented without reducing the P / V value of the surface wave.
In addition, since the synthetic resin is filled in the grooves existing between the piezoelectric substrate, the base substrate, and the coating resin, except for the portion adjacent to the overlapping portion of the electrode fingers, the piezoelectric substrate, the base substrate, and the coating resin The space where the IDT is accommodated is completely sealed by the fixing portion and the synthetic resin in the groove, and the reliability of sealing with the outside air can be improved.
Further, by using SH type surface waves provided with IDTs that are partially composed of comb-teeth electrodes on one side main surface of the piezoelectric substrate, it is possible to concentrate the vibration part only on one side main surface of the piezoelectric substrate. For this purpose, the thickness of the piezoelectric resonator is remarkably reduced because the base substrate and the coating resin disposed for the purpose of forming and sealing a vibration space that does not hinder vibration and a two-layer structure are used as a basic structure. In addition, the reliability of the electrical connection between the IDT and the external terminal can be increased. Furthermore, the man-hours are easy and greatly contribute to cost reduction.
[Brief description of the drawings]
FIG. 1 is an external perspective view showing a piezoelectric resonator according to the present invention. FIG. 2 is a longitudinal sectional view taken along line AA of the piezoelectric resonator shown in FIG. FIG. 4 is a plan view showing an adhesion state with a base substrate. FIG. 5 is a plan view showing a filter of the present invention. FIG. 6 is an impedance characteristic of a piezoelectric resonator in Example 1. FIG. 7 is a diagram showing impedance characteristics of the piezoelectric resonator in Comparative Example 1;
FIG. 8 is a diagram showing the relationship between the thickness of the piezoelectric substrate and the resonance frequency.
FIG. 9 is a view showing a piezoelectric filter of the present invention.
[Explanation of symbols]
1a Piezoelectric substrate 2 Base substrate 3 Insulating adhesive 5 Comb electrode (IDT)
6 groove

Claims (7)

A piezoelectric resonator in which an interdigital transducer (IDT) composed of comb-teeth electrodes is formed on a part of one side main surface of a piezoelectric substrate and driven using SH type surface waves. outside of the IDT electrode fingers in the main surface, Rutotomoni have grooves provided for reflecting the surface wave of the SH type in parallel and adjacent to the electrode fingers, the IDT of the piezoelectric substrate is formed as opposed to the face, and the not hinder the vibration of the SH type surface wave, the base substrate so that a space for housing the grooves in the adjacent portion of the overlapped portion of the electrode fingers is formed the piezoelectric substrate are bonded, further the piezoelectric substrate and the base substrate synthetic resin in the groove present in the adhered portion is filled with the synthetic resin is filled in the grooves in the adjacent parts of the parts of the electrode fingers Piezoelectric resonator, characterized in that not. Claim 1 Symbol placement of the piezoelectric resonator, wherein said groove is formed extending to the end surface of the piezoelectric substrate. 3. The piezoelectric resonator according to claim 1, wherein a depth of the groove is a depth of one wavelength (λ) or more of the SH type surface wave. 4. The piezoelectric resonator according to any one of claims 1 to 3 the thickness of the piezoelectric substrate is less than 320 .mu.m. The base substrate, the piezoelectric resonator according to any one of claims 1 to 4, characterized in that the electrode forming the capacitance is formed. A filter in which a plurality of interdigital transducers (IDTs) composed of comb-teeth electrodes are formed on a part of one side main surface of a piezoelectric substrate, each IDT is electrically connected, and driven using SH type surface waves a is, the outside of the IDT electrode fingers in one main surface of the piezoelectric substrate, grooves for reflecting the surface wave of the SH type in parallel and adjacent to the electrode fingers provided Rutotomoni, wherein as opposed to the surface on which the IDT is formed of a piezoelectric substrate, and wherein not hinder the vibration of SH-type surface wave, so that a space is formed for accommodating the grooves in the adjacent portion of the overlapped portion of the electrode fingers adjacent portions of the base substrate said is bonded to the piezoelectric substrate, further the piezoelectric substrate and the base substrate synthetic resin in the groove present in the adhered portion is filled with, parts of the electrode fingers In Filter takes the groove synthetic resin and wherein the unfilled. The filter according to claim 6, wherein the groove is formed to extend to an end surface of the piezoelectric substrate.

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