JP2011018959A - Piezoelectric vibrator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric vibrator including a structure capable of changing a plurality of characteristics of the piezoelectric vibrator including at least an electromechanical coupling coefficient even when adjusted separately from electrode thickness using a flexural vibration mode.SOLUTION: This piezoelectric vibrator 1 includes a vibration part flexurally vibrating in a normal direction of a principal surface by application of a frequency signal. The vibration part has a structure wherein a plurality of layers including an upper principal surface electrode 2, a piezoelectric substrate 3, a lower principal surface electrode 4 and a dielectric layer 5 are laminated in the principal surface normal direction. The upper principal surface electrode 2 is formed on the upper principal surface of the piezoelectric substrate 3. The lower principal surface electrode 4 is formed on the lower principal surface of the piezoelectric substrate 3. The dielectric layer 5 is laminated on the lower principal surface electrode 4.

Description

  The present invention relates to a piezoelectric vibrator in which vibration is excited in a normal direction of a main surface by applying a frequency signal to electrodes provided on both main surfaces of a plate-like piezoelectric body.

  Piezoelectric vibrators that use electromechanical vibrations of piezoelectric bodies may be used in filters and gyros. There are various shapes and variations of vibration modes in the piezoelectric vibrating body, for example, there is a piezoelectric vibrator that uses an in-plane vibration mode of a ring-shaped piezoelectric vibrating body (see, for example, Patent Document 1).

  As a main characteristic value of the piezoelectric vibrator, there is an electromechanical coupling coefficient. For example, in the case of a gyro, since the rotation detection accuracy depends on the conversion efficiency between the mechanical amplitude and voltage of the piezoelectric vibrator, there is a demand to increase the conversion efficiency between mechanical amplitude and voltage by increasing the electromechanical coupling coefficient. .

  Conventionally, in a piezoelectric vibrator using a bulk wave vibration that is totally reflected at the interface between the electrode and air, the electromechanical coupling coefficient of the piezoelectric body is increased by making the lower surface driving electrode of the piezoelectric body thicker than the upper surface driving electrode. (See, for example, Patent Document 2).

Japanese Patent Laid-Open No. 11-304494 JP 2006-319479 A

  Even in a piezoelectric vibrator using a flexural vibration mode which is a vibration mode different from the in-plane vibration mode, the electromechanical coupling coefficient can be influenced by changing the electrode thickness. However, in addition to the electromechanical coupling coefficient, other characteristics of the piezoelectric vibrator that need to be adjusted include resonance frequency, anti-resonance frequency, mechanical quality factor Qm, etc., and make them appropriate only by adjusting the electrode thickness. I can't.

  An object of the present invention is to provide a piezoelectric vibrator having a structure in which a plurality of characteristics of a piezoelectric vibrator including at least an electromechanical coupling coefficient can be changed by using a flexural vibration mode and adjusting separately from an electrode thickness. And

The piezoelectric vibrator according to the present invention includes a vibration part that bends and vibrates in the normal direction of the principal surface when a frequency signal is applied. The vibration part has a configuration in which a plurality of layers including an upper main surface electrode, a piezoelectric single crystal substrate, a lower main surface electrode, and a dielectric layer are laminated in the main surface normal direction. The upper main surface electrode is provided on the upper main surface of the piezoelectric single crystal substrate. The lower main surface electrode is provided on the lower main surface of the piezoelectric single crystal substrate. The dielectric layer is laminated on at least one of the upper main surface electrode and the lower main surface electrode.
When the finite element method analysis is performed on the piezoelectric vibrator having such a configuration, the thickness of the dielectric layer is adjusted to make the structure of both main surfaces of the vibration part asymmetric, so that the electromechanical coupling coefficient and the resonance frequency are reduced. You can see that it changes. Therefore, using the thickness of the dielectric layer as a design variable separately from the electrode thicknesses of the upper main surface electrode and the lower main surface electrode, various characteristics including at least the electromechanical coupling coefficient and the resonance frequency of the piezoelectric vibrator are high. Can be set with degrees of freedom. If the electromechanical coupling coefficient and the resonance frequency can be adjusted, the mechanical quality factor and the anti-resonance frequency of the piezoelectric single crystal substrate can be adjusted.

  In the present invention, the upper main surface electrode and the lower main surface electrode may have different electrode thicknesses. If only the thickness of the dielectric layer is adjusted, the electromechanical coupling coefficient and the resonance frequency change at the same time, and it is difficult to arbitrarily set each of them. However, by using the adjustment of the electrode thickness in combination, at least the electromechanical coupling coefficient and the resonance frequency can be set arbitrarily. This facilitates the setting of the mechanical quality factor and antiresonance frequency of the piezoelectric single crystal substrate.

The vibrating part of the present invention has a configuration in which an upper main surface electrode, a piezoelectric single crystal substrate, a lower main surface electrode, and a dielectric layer are laminated in this order, and it is preferable that the lower main surface electrode is connected to a reference potential. Thus, the lower main surface electrode can be shielded by the lower main surface electrode between the dielectric layer and the piezoelectric single crystal substrate, and the influence on the electromagnetic field can be eliminated by providing the dielectric layer. It is preferable that the dielectric layer covers the entire lower main surface of the vibration part. Thereby, the continuity of the structure of the vibration part in the direction parallel to the main surface can be increased, and the piezoelectric characteristics can be improved.

  The dielectric layer of the present invention is preferably formed by depositing silicon nitride. Silicon nitride can be formed by a method such as sputtering. Therefore, the thickness of the dielectric layer can be set precisely.

  The piezoelectric vibrator of the present invention preferably includes a support portion that supports the vibration portion. The support portion preferably has a structure in which a plurality of layers including a piezoelectric single crystal substrate, a dielectric layer, and a support substrate stacked on the lower main surface of the dielectric layer are stacked. As a result, by laminating the piezoelectric single crystal substrate and the dielectric layer, the vibration part and the support part can be configured at the same time.

  The piezoelectric single crystal substrate of the present invention is preferably lithium niobate or lithium tantalate. By employing lithium niobate or lithium tantalate, the electromechanical coupling coefficient and the Q value can be increased, and good sensitivity characteristics can be obtained. In particular, the use of lithium tantalate can improve the balance of temperature characteristics as compared with lithium niobate.

  The piezoelectric vibrator according to the present invention is vibrated by a frame-shaped vibrating portion that is line-symmetrical about two axes that are parallel to the main surface and orthogonal to each other, and a support beam that is line-symmetrically about each of the two axes. It is preferable that the upper main surface electrode and the lower main surface electrode are provided symmetrically with respect to each of the two axes. As a result, the position of the vibrating portion supported by the support beam portion becomes a node of bending vibration, and the position of the vibrating portion on the detection axis becomes the antinode of bending vibration. In addition, since the frame-like vibrating portion is supported by the support beam, the bending vibration of the vibrating portion can be supported to the maximum extent without being constrained.

  According to the present invention, various characteristics of the piezoelectric vibrator including at least the electromechanical coupling coefficient and the resonance frequency can be changed by adjusting the thickness of the dielectric layer. Therefore, a plurality of characteristics of the piezoelectric vibrator can be set with a high degree of freedom by using the thickness of the dielectric layer as a design variable different from the electrode thickness.

It is a figure explaining the structural example of the piezoelectric vibrator which concerns on embodiment of this invention. It is a figure explaining the Euler angle display of a right-hand system. It is a figure explaining the circuit structure of a vibration gyro apparatus provided with the piezoelectric vibrator shown in FIG. It is a figure explaining operation | movement of the piezoelectric vibrator shown in FIG. It is a figure explaining the influence on the various characteristics of a piezoelectric vibrator by the setting of the thickness of a dielectric material layer. It is a figure explaining the influence on the various characteristics of a piezoelectric vibrator by the setting of electrode thickness. It is a figure explaining the relationship between a temperature change and the fluctuation | variation of a frequency change rate.

A piezoelectric gyro vibrator according to an embodiment of the present invention will be described using a vibration gyro device as a configuration example.
FIG. 1 is a diagram illustrating a configuration example of a piezoelectric vibrator. 1A is a plan view, FIG. 1B is a central sectional view, FIG. 1C is an AA ′ sectional view, and FIG. 1D is a BB ′ sectional view.

The piezoelectric vibrator 1, the detection axis orthogonal two axes (X ₁ axis and the X ₂ axis), for detecting the rotation of the detection axis. Therefore, line-symmetric shape of the piezoelectric vibrator 1 X ₁ axis as a symmetrical axis, and constitute a line-symmetrical shape to the X ₂ axis as a symmetrical axis. Further, the support substrate 6, the dielectric layer 5, the lower main surface electrode 4, the piezoelectric substrate 3, and the upper main surface electrode 2 are laminated in order from the bottom along the X ₃ axis perpendicular to the X ₁ -X ₂ surface. It is composed.

The piezoelectric substrate 3 and the support substrate 6 are a lithium niobate (LiNbO ₃ ) piezoelectric single crystal substrate or a lithium tantalate (LiTaO ₃ ) piezoelectric single crystal substrate, the support substrate 6 is 0.34 mm thick, and the piezoelectric substrate 3 is 1 μm. It is thick. The dielectric layer 5 is silicon nitride of 1 μm or less. The lower main surface electrode 4 is a tungsten (W) electrode having an electrode thickness of 500 nm, and the upper main surface electrode 2 is an aluminum (Al) electrode. Since the tungsten electrode has a high melting point, it is possible to suppress diffusion of the electrode due to heat load, and since the specific gravity is large and the specific acoustic impedance is large, damping of the elastic wave mechanical vibration excited by the piezoelectric vibrator can be suppressed. Since the aluminum electrode has a small specific resistance, the series equivalent resistance of the piezoelectric vibrator can be suppressed.

The piezoelectric substrate 3 is converted by a right-handed Euler angle display (φ, θ, ψ) = (0 °, θ °, 45 °) from the crystal coordinate system (X, Y, Z) of the piezoelectric substrate 3. In the coordinate system (X ₁ , X ₂ , X ₃ ), the X ₁ -X ₂ plane is the principal plane, and the crystal axis X coincides with the axis that equally divides the detection axes X ₁ , X ₂ at 45 °. Configure. FIG. 2 is a diagram showing the relationship between the right-handed Euler angle display (φ, θ, ψ) and the transformed coordinate system (X ₁ , X ₂ , X ₃ ) (for example, the Japan Society for the Promotion of Acoustic Wave Technology) (Refer to 150th Committee of Acoustic Wave Element Technology, Ohmsha, 1991; P.549.)

The piezoelectric substrate 3 is viewed piezoelectric substrate main surface _(X 1 -X ₂ side) from the _{X 3} axis, it is divided into an inner region 3A and the frame-shaped region 3B and outer region 3C. The frame-shaped region 3B has a circular inner shape / circular outer shape with an inner diameter of 400 μm and an outer diameter of 500 μm. The inner region 3A is a circle having a diameter of 300 μm. The outer region 3C has a circular inner shape and a rectangular outer shape with an inner diameter of 600 μm. Four inner open holes 31 and four inner beam portions 32 are provided between the inner region 3A and the frame-like region 3B, and four outer open holes are provided between the outer region 3C and the frame-like region 3B. 33 and four inner beam portions 32 are provided. The inner beam portion 32 and the outer beam portion _34, the _{X 1} axis positive direction in the X 1 -X ₂ side as 0 °, 45 °, 135 ° , 225 °, of width 20μm along the direction of 315 ° beam-like As an area. The inner beam portion 32 and the outer beam portion 34 support the frame-shaped region 3 </ b> B in a state where it floats from the support substrate 6.

  The lower main surface electrode 4 is provided in a region covering at least the frame-shaped region 3B of the lower main surface of the piezoelectric substrate 3, and is connected to a reference potential.

  Dielectric layer 5 is formed by sputtering silicon nitride over the entire lower main surface of piezoelectric substrate 3 and lower main surface electrode 4 by sputtering. By using sputtering, the thickness of the dielectric layer 5 can be set precisely.

Supporting substrate 6, the supporting substrate principal _(X 1 -X ₂ side) as viewed from the _{X 3} axis, it is divided into an inner region 6A and vibration region 6B and the outer region 6C. The vibration region 6B is a region in which a vibration space is provided by digging the support substrate 6 at a depth of 3 μm from the upper main surface into a circular inner shape / circular outer shape with an inner shape of 300 μm and an outer shape of 600 μm. The region 3B, the inner opening hole 31, the inner beam portion 32, the outer opening hole 33, and the inner beam portion 32 are provided at positions facing each other. The vibration space communicates with the inner opening hole 31 and the outer opening hole 33 to prevent interference between the frame-shaped region 3 </ b> B and the support substrate 6. The inner region 6A is a region having a diameter of 300 μm, and is a region where the inner region 3A of the piezoelectric substrate 3 overlaps. The outer area 6C is an area having an inner diameter of 600 μm, and is an area where the outer area 3C of the piezoelectric substrate 3 overlaps. By using the same piezoelectric material as that of the piezoelectric substrate 3 for the support substrate 6, the difference in linear expansion coefficient can be suppressed. The support substrate 6 may be made of Si or glass, which has a thermal expansion coefficient different from that of the piezoelectric substrate 3 but has excellent heat resistance and is easily available and inexpensive.

The upper main surface electrode 2 includes eight drive detection electrodes 2A, eight circuit connection electrodes 2B, four reference potential connection electrodes 2C, and eight wirings 2D. The drive detection electrode 2A is patterned on the upper surface of the frame-like region 3B. The circuit connection electrode 2B and the reference potential connection electrode 2C are patterned on the upper surface of the outer region 3C. The wiring 2D is provided from the frame-like region 3B to the outer region 3C via the outer beam portion. Drive detection electrodes 2A is two by two, the positive direction of the X ₁ axis sides, arranged in the negative direction of the X ₁ axis sides, the positive direction of the X ₂ axis sides, the spacing of the negative direction of the X ₂ axis both sides about 5μm Yes. Specifically, each drive detection electrode 2A is about 0 ° to 30 °, 60 ° to 90 °, 90 ° to 120 °, 150 ° to 150 ° with the X ₂ axis positive direction on the X ₁ -X ₂ plane being 0 °. It occupies ranges of 180 °, 180 ° to 210 °, 240 ° to 270 °, 270 ° to 300 °, 330 ° to 360 °. The adjacent drive detection electrodes 2A are spaced at an interval of about 5 μm. The circuit connection electrode 2B is connected to a drive detection circuit that will be described in detail later. Reference potential connection electrode 2C is connected to lower main surface electrode 4 through a through hole. The wiring 2D connects between the drive detection electrode 2A and the circuit connection electrode 2B, and is joined to the piezoelectric substrate 3 via the insulating layer 2E.

  In the above configuration, the drive detection electrode 2A is provided on the upper main surface of the frame-shaped region 3B in the piezoelectric substrate 3, and the lower main surface electrode 4 and the dielectric layer 5 are stacked on the lower main surface of the frame-shaped region 3B. Thus, the vibration part of the present invention is configured. The vibration part bends and vibrates when a frequency signal is applied.

  FIG. 3 is a circuit diagram illustrating an example of a circuit configuration when a drive detection circuit is connected to the piezoelectric vibrator 1 to configure a vibration gyro apparatus. The drive detection circuit includes a frequency signal generation circuit 9, differential circuits 7A and 7B, and smoothing circuits 8A and 8B. A ground is connected to the reference potential connection electrode 2 </ b> C of the piezoelectric vibrator 1.

The frequency signal generation circuit 9 is connected to the eight circuit connection electrodes 2B via the drive resistor R, and gives a frequency signal to each of the eight drive detection electrodes 2A. The frequency signals given to each drive detection electrode 2A have the same phase and the same amplitude. The frequency is the resonance frequency of the frame region. The resonance frequency, the vibration of the _{X 3} axially of the frame-shaped region 3B _is located on the _{X 1} axis and _{the X 2} axis in X 1 -X ₂ side (0 °, 90 °, 180 °, 270 °) oscillating in A vibration node is formed at a position (45 °, 135 °, 225 °, 315 °) supported by the beam portion.

Two drive detection electrodes 2A disposed on the X ₁ axis negative direction (the left side in the drawing) of the four drive detection electrodes 2A disposed on both sides of the X ₂ axis, to a first input terminal of the differential circuit 7A Connected. Further, two drive detection electrodes 2A disposed on the X ₁ axis positive direction (the right side in the drawing) is connected to a second input terminal of the differential circuit 7A. Further, two drive detection electrodes 2A disposed in the X ₂ axis negative direction (lower side) of the four drive detection electrodes 2A disposed on both sides of X ₁ axis, a first input terminal of the differential circuit 7B Connected to. Two drive detection electrodes 2A disposed in the X ₂ axis positive direction (upward) is connected to a second input terminal of the differential circuit 7B.

  The output terminals of the differential circuits 7A and 7B are connected to the smoothing circuits 8A and 8B, and the differential circuits 7A and 7B output the voltage difference between the first input terminal and the second input terminal. Smoothing circuits 8A and 8B smooth the output voltages of the differential circuits 7A and 7B.

FIG. 4 is a diagram for explaining the operation of the piezoelectric vibrator 1. Figure 4 is an example of rotation (A) in the _{X 1} axis, FIG. 4 (B) shows an example of rotating the _{X 2} axis.

When bending vibration at the resonance frequency, when X ₂ axes of angular velocity is applied to the vibration gyro device, the Coriolis force is applied to the X ₁ axis direction. Then, the phase of the frequency signal being applied to the four drive detection electrodes 2A disposed on both sides of the X ₂ axis, and drive detection electrodes 2A disposed on the X ₁ axis positive direction, arranged in the X ₁ axis negative direction The driving detection electrode 2A changes in the opposite direction. For this reason, the differential output by the differential circuit 7A becomes a voltage corresponding to the magnitude of the Coriolis force.

Further, when the X ₁ axis in the angular velocity is applied to the vibration gyro device, the Coriolis force is applied to the X ₂ axis direction. Then, the phase of the frequency signal being applied to the four drive detection electrodes 2A disposed on both sides of X ₁ axis, and the drive detection electrodes 2A disposed in the X ₂ axis positive direction, arranged in the X ₂ axis negative direction The driving detection electrode 2A changes in the opposite direction. For this reason, those differential outputs by the differential circuit 7B become voltages according to the magnitude of the Coriolis force.

In the state where the piezoelectric vibrator 1 is not rotating, the frequency signals are removed in the differential circuits 7A and 7B because they have the same phase and the same amplitude. The signal for exciting the respective drive signals and for exciting the detection electrodes, the drive detection electrodes arranged along the X ₂ axis when X ₁ of the axis rotation when acting like impact on the vibration gyro apparatus, X signal to excite the arranged drive detection electrodes along the X ₁ axis in the _biaxial rotation about will be removed differential circuit 7A, by 7B since also in phase, same amplitude.

Hereinafter, various characteristics of the piezoelectric vibrator will be described by way of example.
FIG. 5 shows the thickness of the dielectric layer and various characteristics of the piezoelectric vibrator when a right-handed Euler angle display (0 °, 50 °, 45 °) lithium niobate substrate is used for the piezoelectric substrate 3. It is a figure which shows a relationship. In this example, the upper main surface electrode is 500 nm and the lower main surface electrode is 500 nm.

  FIG. 5A is a diagram showing the relationship between the electromechanical coupling coefficient and the thickness of the dielectric layer.

The electromechanical coupling coefficient takes into consideration the material constant of the piezoelectric substrate 3 and the structure of the vibrator, and kv = (Cn / Cf) ^ (1 using the free capacity Cf and the equivalent vibration capacity Cn of the focused vibration mode. / 2). The free volume Cf and an equivalent value capacitor Cn between both terminals Specifically, 0V lower electrode, a terminal electrode adjacent to the X ₁ axis of the upper electrode are connected in parallel, the electrode adjacent to the X ₂ axis parallel It can be obtained by applying a voltage of opposite polarity to each of the terminals connected to. As shown in the figure, the electromechanical coupling coefficient is changed by changing the film thickness of the dielectric layer (SiN), and the electromechanical coupling coefficient is increased as the film thickness of the dielectric layer (SiN) is increased.

  FIG. 5B is a diagram showing the relationship between the resonance frequency and the thickness of the dielectric layer. The resonance frequency takes into consideration the material constant of the piezoelectric substrate 3 and the structure of the vibrator. As shown in the figure, in the lithium niobate substrate, the resonant frequency changes by changing the thickness of the dielectric layer (SiN), and the resonant frequency increases as the thickness of the dielectric layer (SiN) increases. To do.

  FIG. 6 shows the electrode thickness of the upper principal surface electrode and various characteristics of the piezoelectric vibrator when a right-handed Euler angle display (0 °, 132 °, 45 °) lithium tantalate substrate is used for the piezoelectric substrate 3. It is a figure explaining the relationship. Here, an example in which the lower main surface electrode is 500 nm and the electrode thickness of the upper main surface electrode and the thickness of the dielectric layer are changed is shown.

  FIG. 6A is a diagram illustrating the relationship between the electromechanical coupling coefficient and the electrode thickness of the upper principal surface electrode.

  As shown in the figure, the electromechanical coupling coefficient is changed by changing the electrode thickness of the upper main surface electrode, and the electromechanical coupling coefficient is reduced as the electrode thickness of the upper main surface electrode is increased.

  FIG. 6B is a diagram for explaining the relationship between the resonance frequency and the electrode thickness of the upper principal surface electrode. As shown in the figure, the resonance frequency hardly changes even if the electrode thickness of the upper main surface electrode is changed.

  From the data shown in FIGS. 5 and 6, it can be seen that only the adjustment of the electrode thickness can set the electromechanical coupling coefficient, and the resonance frequency cannot be set. Therefore, it is possible to set the resonance frequency only by adjusting the thickness of the dielectric layer, and by using both the adjustment of the electrode thickness and the thickness adjustment of the dielectric layer, both the electromechanical coupling coefficient and the resonance frequency are set. It can be said that it can be set arbitrarily. If both the electromechanical coupling coefficient and the resonance frequency can be set arbitrarily, it becomes easy to set the mechanical quality coefficient and the anti-resonance frequency of the piezoelectric single crystal substrate. As described above, by using the thickness of the dielectric layer as a design variable in addition to the electrode thickness, various characteristics including at least the electromechanical coupling coefficient and the resonance frequency of the piezoelectric vibrator can be set with a high degree of freedom.

  FIG. 7 shows a change in temperature when the piezoelectric substrate 3 and the support substrate 6 are set to (0 °, 120 °, 45 °) in a right-handed Euler angle display, and a change in the frequency change rate based on 25 ° C. It is a figure explaining a relationship. FIG. 7A shows an example in which a lithium niobate substrate is adopted as the piezoelectric substrate 3, and FIG. 7B shows an example in which a lithium tantalate substrate is adopted as the piezoelectric substrate 3. In the case of a lithium niobate substrate, the change in frequency change rate per 1 ° C. of temperature change was −35.1 ppm, while in the case of lithium tantalate, the change in frequency change rate per 1 ° C. of temperature change was −9. It was 0 ppm. Therefore, in order to improve the temperature characteristic of the resonance frequency, lithium tantalate is used rather than adopting a lithium niobate substrate that can increase the electromechanical coupling coefficient and the Q value of the vibrator and obtain good sensitivity characteristics. It can be said that it is desirable to employ a substrate.

  In the above embodiment, although the circular shape is shown as the shape of the frame-like region, the present invention can be implemented with various shapes such as a square, an oval, a rectangle, and a polygon. Moreover, the structure which excluded either the inner side area | region and the outer side area | region of the piezoelectric substrate may be sufficient, and the structure which excluded both may be sufficient.

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric vibrator 2 ... Upper main surface electrode 2A ... Drive detection electrode 2B ... Circuit connection electrode 2C ... Reference potential connection electrode 2D ... Wiring 2E ... Insulating layer 3 ... Piezoelectric substrate 31 ... Inner opening hole 32 ... Inner beam part 33 ... Outer open hole 34 ... outer beam portion 3A ... inner region 3B ... frame-like region 3C ... outer region 4 ... lower main surface electrode 5 ... dielectric layer 6 ... support substrate 6A ... inner region 6B ... vibrating region 6C ... outer region 7A, 7B: Differential circuit 8A, 8B: Smoothing circuit 9: Frequency signal generation circuit

Claims (8)

A piezoelectric vibrator including a vibration part that bends and vibrates in the principal surface normal direction by application of a frequency signal,
The vibrating portion is configured by laminating a plurality of layers including an upper main surface electrode, a piezoelectric single crystal substrate, a lower main surface electrode, and a dielectric layer in the main surface normal direction,
The upper main surface electrode is provided on the upper main surface of the piezoelectric single crystal substrate,
The lower main surface electrode is provided on the lower main surface of the piezoelectric single crystal substrate,
The dielectric layer is a piezoelectric vibrator laminated on at least one of the upper main surface electrode and the lower main surface electrode.   The piezoelectric vibrator according to claim 1, wherein the upper main surface electrode and the lower main surface electrode have different electrode thicknesses.   The vibrating section has a configuration in which the upper main surface electrode, the piezoelectric single crystal substrate, the lower main surface electrode, and the dielectric layer are stacked in this order, and the lower main surface electrode is connected to a reference potential. Item 3. The piezoelectric vibrator according to Item 1 or 2.   The piezoelectric vibrator according to claim 3, wherein the lower main surface electrode and the dielectric layer cover the entire lower main surface of the vibration section.   The piezoelectric vibrator according to claim 1, wherein the dielectric layer is formed by depositing silicon nitride.   The piezoelectric vibrator includes a support unit that supports the vibration unit, and the support unit includes the piezoelectric single crystal substrate, the dielectric layer, and a support substrate laminated on a lower main surface of the dielectric layer. The piezoelectric vibrator according to claim 1, wherein the piezoelectric vibrator has a configuration in which a plurality of layers are stacked. The vibrating portion has a frame shape that is axisymmetric about each of two axes that are parallel to the main surface and orthogonal to each other.
The support portion supports the vibration portion by a support beam provided symmetrically about each of the two axes.
The piezoelectric vibrator according to claim 6, wherein the upper main surface electrode and the lower main surface electrode are provided line-symmetrically with respect to each of the two axes.   The piezoelectric vibrator according to claim 1, wherein the piezoelectric single crystal substrate is lithium niobate or lithium tantalate.

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