Piezoelectric Vibration Element

Abstract

This piezoelectric vibration element (10) comprises a piezoelectric piece (11) and an excitation electrode (14a) that overlap in the thickness direction. The piezoelectric vibration element (10) has a high acoustic velocity region (17) and a low acoustic velocity region (18) that has a lower acoustic velocity than the high acoustic velocity region (17). The high acoustic velocity region (17) is provided in a region that overlaps a central portion of the excitation electrode (14a) in a plan view in the thickness direction. The low acoustic velocity region (18) includes a first low acoustic velocity region (18A) and a second low acoustic velocity region (18B) that are provided in regions that overlap end portions of the excitation electrode (14a) that surrounds the high acoustic velocity region (17) in a plan view in the thickness direction. In a first direction intersecting the thickness direction, the first low acoustic velocity region (18A) is adjacent to the high acoustic velocity region (17), and the second low acoustic velocity region (18B) is adjacent to the high acoustic velocity region (17) on the side opposite to the first low acoustic velocity region (18A). When the length of the excitation electrode (14a) in the first direction is Ea, the length of the first low acoustic velocity region (18A) in the first direction is Wa1, and the length of the second low acoustic velocity region (18B) in the first direction is Wa2, the relationships 0.20 ≤ Wa1 / Ea, 0.20 ≤ Wa2 / Ea, and 0.5 ≤ (Wa1 + Wa2) / Ea ≤ 0.96 are satisfied.

Description

[Technical field]

[0001] The present invention relates to a piezoelectric vibration element. [Background technology]

[0002] Piezoelectric vibration elements are used in various electronic devices such as mobile communication terminals, communication base stations, home appliances, etc. as timing devices, sensors, oscillators, etc. The piezoelectric vibration element includes a piezoelectric piece having a pair of main surfaces, and a pair of excitation electrodes provided on the pair of main surfaces of the piezoelectric piece.

[0003] For example, Patent Document 1 discloses a configuration in which the mesa thickness ratio of the inverted mesa shape of an excitation electrode is changed while the shape of the vibration displacement is flattened to reduce spurious oscillations, which are vibrations occurring at frequencies other than the main vibration. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. WO 98 / 38736 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the prior art, it is desirable to further reduce spurious oscillations and improve the electromechanical coupling coefficient.

[0006] The present invention has been made in view of the above circumstances, and has an object to provide a piezoelectric vibration element that can improve the electromechanical coupling coefficient. [Means for solving the problem]

[0007] A piezoelectric vibration element according to one aspect of the present invention is a piezoelectric vibration element including a piezoelectric piece and an excitation electrode that overlap in a thickness direction, the piezoelectric vibration element having a high acoustic velocity region and a low acoustic velocity region having a lower acoustic velocity than the high acoustic velocity region, the high acoustic velocity region being provided in a region that overlaps a central portion of the excitation electrode in a planar view in the thickness direction, and the low acoustic velocity region including a first low acoustic velocity region and a second low acoustic velocity region that are provided in a region that overlaps an end portion of the excitation electrode surrounding the high acoustic velocity region in a planar view in the thickness direction, In a first direction intersecting with the first direction, the first low acoustic velocity region is adjacent to the high acoustic velocity region, and the second low acoustic velocity region is adjacent to the high acoustic velocity region on the opposite side to the first low acoustic velocity region. When the length of the excitation electrode in the first direction is Ea, the length of the first low acoustic velocity region in the first direction is Wa1, and the length of the second low acoustic velocity region in the first direction is Wa2, the relationships 0.20≦Wa1 / Ea, 0.20≦Wa2 / Ea, and 0.5≦(Wa1+Wa2) / Ea≦0.96 hold.

[0008] A piezoelectric vibration element according to another aspect of the present invention is a piezoelectric vibration element including a piezoelectric piece and an excitation electrode that overlap in a thickness direction, and has a high acoustic velocity region and a low acoustic velocity region in which the acoustic velocity is lower than that of the high acoustic velocity region, the high acoustic velocity region is provided in a region that overlaps a center portion of the excitation electrode in a planar view in the thickness direction, and the low acoustic velocity region includes a first low acoustic velocity region, a second low acoustic velocity region, a third low acoustic velocity region, and a fourth low acoustic velocity region that are provided in a region that overlaps an end portion of the excitation electrode surrounding the high acoustic velocity region in a planar view in the thickness direction, and in a first direction intersecting the thickness direction, the first low acoustic velocity region is adjacent to the high acoustic velocity region. The second low sound velocity region is adjacent to the high sound velocity region on the opposite side to the first low sound velocity region, the third low sound velocity region is adjacent to the high sound velocity region in a second direction intersecting the thickness direction and the first direction, and the fourth low sound velocity region is adjacent to the high sound velocity region on the opposite side to the third low sound velocity region, and when the length of the excitation electrode in the first direction is Ea, the length of the excitation electrode in the second direction is Eb, the length of each of the first low sound velocity region and the second low sound velocity region in the first direction is Wa, and the length of each of the third low sound velocity region and the fourth low sound velocity region in the second direction is Wb, 0.8<5.0×(Wa / Ea) 2 +4.0×(Wb / Eb) 2 Furthermore, the relationships Wa / Ea≦0.48 and Wb / Eb≦0.48 are satisfied. Effect of the Invention

[0009] According to the present invention, it is possible to provide a piezoelectric vibration element capable of improving the electromechanical coupling coefficient. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view of a crystal oscillator according to a first embodiment. [Diagram 2] FIG. 1 is an exploded perspective view of a crystal resonator according to a first embodiment. [Diagram 3] 1 is a cross-sectional view of a quartz crystal resonator according to a first embodiment. [Figure 4] 1 is a cross-sectional view of a quartz crystal vibration element according to a first embodiment. [Diagram 5] FIG. 1 is a plan view of a quartz crystal vibration element according to a first embodiment. [Figure 6] FIG. 11 is a diagram showing a simulation result based on the first embodiment. [Figure 7] FIG. 11 is a diagram showing a simulation result based on the first embodiment. [Figure 8] FIG. 11 is a diagram showing a simulation result based on the first embodiment. [Figure 9] FIG. 11 is a diagram showing a simulation result based on the first embodiment. [Figure 10] 13 is a graph showing the influence of the planar dimensions of the low sound velocity region. [Figure 11] 13 is a graph showing the influence of the planar dimensions of the low sound velocity region. [Figure 12] 13 is a graph showing the influence of the planar dimensions of the low sound velocity region. [Figure 13] 13 is a graph showing the effect of the thickness of a low sound velocity region. [Figure 14] 13 is a graph showing the effect of the thickness of a high sound velocity region. [Figure 15] FIG. 11 is a plan view of a quartz crystal vibrating element according to a second embodiment. [Figure 16] FIG. 11 is a plan view of a quartz crystal vibrating element according to a third embodiment. [Figure 17]FIG. 11 is a plan view of a quartz crystal vibrating element according to a fourth embodiment. [Figure 18] FIG. 11 is a cross-sectional view of a quartz crystal vibrating element according to a fourth embodiment. [Figure 19] FIG. 13 is a diagram showing a simulation result based on the fourth embodiment. [Figure 20] FIG. 11 is a diagram comparing simulation results based on the first and fourth embodiments. [Figure 21] 13 is a graph showing the influence of the planar dimensions of a hole. [Figure 22] 11 is a graph showing the influence of the planar dimensions and pitch of holes. [Figure 23] 11 is a graph showing the influence of the planar dimensions and pitch of holes. [Figure 24] FIG. 13 is a cross-sectional view of a quartz crystal vibrating element according to a fifth embodiment. [Diagram 25] FIG. 13 is a diagram showing a comparison of simulation results based on the fourth and fifth embodiments. [Figure 26] FIG. 13 is a cross-sectional view of a quartz crystal vibrating element according to a sixth embodiment. [Figure 27] FIG. 13 is a diagram showing a simulation result based on the sixth embodiment. [Figure 28] FIG. 13 is a cross-sectional view of a quartz crystal vibrating element according to a seventh embodiment. [Figure 29] FIG. 13 is a cross-sectional view of a quartz crystal vibrating element according to an eighth embodiment. [Diagram 30] FIG. 13 is a cross-sectional view of a quartz crystal vibrating element according to a ninth embodiment. [Diagram 31] FIG. 13 is a plan view of a modified example of the high sound velocity region according to the fourth embodiment. [Diagram 32] FIG. 13 is a plan view of a modified example of the high sound velocity region according to the fourth embodiment. [Diagram 33] FIG. 13 is a plan view of a modified example of the high sound velocity region according to the fourth embodiment. [Diagram 34] FIG. 13 is a plan view of a modified example of the high sound velocity region according to the fourth embodiment. [Diagram 35] FIG. 13 is a plan view of a modified example of the high sound velocity region according to the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described. In the following description of the drawings, the same or similar components are represented by the same or similar reference numerals. The drawings are illustrative, and the dimensions and shapes of each part are schematic, and the technical scope of the present invention should not be interpreted as being limited to the embodiment.

[0012] In order to clarify the mutual relationships between the drawings and to aid in understanding the positional relationships of the various components, an orthogonal coordinate system consisting of an X-axis, a Y'-axis, and a Z'-axis may be conveniently attached to each drawing. The X-axis, the Y'-axis, and the Z'-axis correspond to each other in each drawing. The X-axis, the Y'-axis, and the Z'-axis each correspond to the crystallographic axes of the quartz blank 11, which will be described later. The X-axis corresponds to the electrical axis (polarity axis) of the quartz, the Y-axis corresponds to the mechanical axis of the quartz, and the Z-axis corresponds to the optical axis of the quartz. The Y'-axis and the Z'-axis are respectively axes obtained by rotating the Y-axis and Z-axis around the X-axis by 35 degrees 15 minutes ± 1 minute 30 seconds in the direction from the Y-axis to the Z-axis.

[0013] In the following description, the direction parallel to the X-axis is referred to as the "X-axis direction", the direction parallel to the Y'-axis is referred to as the "Y'-axis direction", and the direction parallel to the Z'-axis is referred to as the "Z'-axis direction". The directions of the tips of the arrows of the X-axis, Y'-axis, and Z'-axis are referred to as "positive" or "+ (plus)", and the directions opposite to the arrows are referred to as "negative" or "- (minus)". For convenience, the +Y'-axis direction is described as the upward direction, and the -Y'-axis direction is described as the downward direction, but the up-down directions of the crystal resonator element 10, the crystal resonator 1, and the crystal oscillator 100 are not limited to these directions. The plane specified by the X-axis and the Z'-axis is referred to as the Z'X plane, and the same applies to the planes specified by the other axes.

[0014] First Embodiment

[0015] First, a schematic configuration of a crystal oscillator according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a cross-sectional view of the crystal oscillator according to the first embodiment.

[0016] In the following description, a crystal oscillator (XO: Crystal Oscillator) having a crystal resonator (Quartz Crystal Resonator Unit) is taken as an example of a piezoelectric oscillator. A crystal resonator unit having a crystal resonator element (Quartz Crystal Resonator) is taken as an example of a piezoelectric resonator unit. A crystal resonator element having a crystal piece is taken as an example of a piezoelectric resonator element. A crystal piece is a type of piezoelectric body (piezoelectric piece) that vibrates in response to an applied voltage. The piezoelectric oscillator is not limited to a crystal resonator, and may use other piezoelectric bodies such as ceramics. Similarly, the piezoelectric resonator is not limited to a crystal resonator, and may use other piezoelectric bodies such as ceramics. Similarly, the piezoelectric resonator element is not limited to a crystal resonator element, and may use other piezoelectric bodies such as ceramics.

[0017] As shown in FIG. 1, the crystal oscillator 100 includes a crystal unit 1, a mounting substrate 130, a cover 140, and an electronic component 156.

[0018] The crystal unit 1 and the electronic component 156 are housed in a space formed between the mounting substrate 130 and the lid 140. The space formed by the mounting substrate 130 and the lid 140 is, for example, hermetically sealed. This space may be hermetically sealed in a vacuum state, or may be hermetically sealed in a state filled with a gas such as an inert gas.

[0019] The mounting substrate 130 is a flat circuit board and is configured to include, for example, a glass epoxy plate and a wiring layer patterned on the glass epoxy plate.

[0020] The quartz crystal unit 1 is provided on one surface (the upper surface in FIG. 1) of the mounting substrate 130. More specifically, the quartz crystal unit 1 is electrically connected to a wiring layer of the mounting substrate 130 by solder 153.

[0021] The lid 140 includes an opening with a bottom that is open on one side (the lower side in FIG. 1). In other words, the lid 140 includes a flat top wall, a side wall extending from the outer edge of the top wall toward the mounting substrate 130, and a flange extending outward from the tip of the side wall. The flange is bonded to one surface (the upper surface in FIG. 1) of the mounting substrate 130. In this way, the crystal unit 1 bonded to the mounting substrate 130 is housed inside the lid 140. The lid 140 is made of a metal material and is formed, for example, by drawing a metal plate.

[0022] The electronic component 156 is provided on one surface (the upper surface in FIG. 1) of the mounting board 130. More specifically, the wiring layer of the mounting board 130 and the electronic component 156 are joined by solder 153. In this way, the electronic component 156 is mounted on the mounting board 130.

[0023] The electronic component 156 is electrically connected to the crystal unit 1 through the wiring layer of the mounting board 130. The electronic component 156 includes, for example, a capacitor, an IC chip, and the like. The electronic component 156 is, for example, a part of an oscillation circuit that oscillates the crystal unit 1, or a part of a temperature compensation circuit that compensates for the temperature characteristics of the crystal unit 1. When the electronic component 156 includes a temperature compensation circuit, the crystal oscillator 100 corresponds to an example of a temperature compensated crystal oscillator (TCXO). The crystal oscillator 100 may correspond to an example of a voltage controlled crystal oscillator (VCXO) or an example of an oven controlled crystal oscillator (OCXO).

[0024] Next, the configuration of the crystal resonator 1 according to the first embodiment will be described with reference to Fig. 2 and Fig. 3. Fig. 2 is an exploded perspective view of the crystal resonator according to the first embodiment. Fig. 3 is a cross-sectional view of the crystal resonator according to the first embodiment.

[0025] The Z'-axis direction corresponds to an example of a "first direction", the X-axis direction corresponds to an example of a "second direction", and the Y'-axis direction corresponds to an example of a "third direction". The Y'-axis direction corresponds to an example of a "thickness direction". However, the first direction, second direction, and third direction are not limited to the above. For example, the X-axis direction may be the first direction, and the Z'-axis direction may be the second direction.

[0026] The quartz crystal resonator 1 includes a quartz crystal resonator element 10, a base member 30, a cover member 40, and a bonding portion 50.

[0027] The quartz crystal element 10 is an electromechanical energy conversion element that converts electrical energy into mechanical energy and vice versa by the piezoelectric effect. The main mode frequency of the quartz crystal element 10 is, for example, about 0.8 GHz to 2.0 GHz, for example, about 0.95 GHz. The inharmonic mode frequency of the quartz crystal element 10 is, for example, within a range of about 1% of the main mode frequency. The quartz crystal element 10 includes a thin quartz crystal piece 11, a first excitation electrode 14a and a second excitation electrode 14b that constitute a pair of excitation electrodes, a first extraction electrode 15a and a second extraction electrode 15b that constitute a pair of extraction electrodes, and a first connection electrode 16a and a second connection electrode 16b that constitute a pair of connection electrodes.

[0028] The crystal blank 11 has an upper surface 11A and a lower surface 11B that face each other. The upper surface 11A is located on the side that faces the top wall portion 41 of the cover member 40. The lower surface 11B is located on the side that faces the base member 30. The upper surface 11A and the lower surface 11B correspond to a pair of main surfaces of the crystal blank 11.

[0029] The quartz blank 11 is, for example, an AT-cut quartz crystal. An AT-cut quartz crystal is formed so that the XZ' plane is the main surface and the thickness is in the direction parallel to the Y' axis. As an example, when the upper surface 11A is viewed in a plan view in the thickness direction (hereinafter simply referred to as "plan view"), the shape of the quartz blank 11 (hereinafter referred to as "planar shape") is a square having a pair of sides extending in the Z'-axis direction and a pair of sides extending in the X-axis direction. Furthermore, the quartz blank 11 has a thickness in the Y'-axis direction. As an example, the shape of the quartz blank 11 is a flat plate with a uniform thickness.

[0030] The planar shape of the crystal piece is not limited to the above. For example, the planar shape of the crystal piece may be a rectangle having a long side extending in the Z'-axis direction and a short side extending in the X-axis direction, or a rectangle having a short side extending in the Z'-axis direction and a long side extending in the X-axis direction. The planar shape of the crystal piece may be a polygonal shape, a circular shape, an elliptical shape, or a combination of these. In addition, the crystal piece is not limited to a flat plate shape. The crystal piece may have a mesa structure or an inverted mesa structure having unevenness on at least one of the upper surface 11A and the lower surface 11B. The crystal piece may have a convex structure in which the amount of change in thickness changes continuously, or a bevel structure in which the amount of change in thickness changes discontinuously.

[0031] The AT-cut quartz piece 11 is cut out with the XZ' plane as the principal surface, and the Y'-axis and Z'-axis are respectively determined by rotating the Y-axis and Z-axis around the X-axis by 35 degrees 15 minutes ± 1 minute 30 seconds from the Y-axis in the direction of the Z-axis out of the X-axis, Y-axis, and Z-axis, which are the crystal axes of synthetic quartz crystal.

[0032] The quartz crystal vibrating element 10 using the AT-cut quartz crystal blank 11 has high frequency stability over a wide temperature range. In addition, the AT-cut quartz crystal vibrating element has excellent aging characteristics and can be manufactured at low cost. Furthermore, the AT-cut quartz crystal vibrating element uses the thickness shear vibration mode as its main vibration.

[0033] The cut angle of the quartz crystal piece is not limited to the above. The rotation angle of the Y'-axis and Z'-axis of the AT-cut quartz crystal piece 11 may be inclined from 35°15′ to −5° or +15°. The cut angle of the quartz crystal piece may be a cut other than the AT cut, such as a BT cut, a GT cut, or an SC cut.

[0034] The first excitation electrode 14a and the second excitation electrode 14b apply an alternating voltage to the crystal blank 11 to excite the crystal blank 11. The first excitation electrode 14a and the second excitation electrode 14b are provided in the center of the crystal blank 11 in a plan view. The first excitation electrode 14a is provided on the upper surface 11A, and the second excitation electrode 14b is provided on the lower surface 11B. The first excitation electrode 14a and the second excitation electrode 14b face each other in the Y'-axis direction with the crystal blank 11 in between. The first excitation electrode 14a corresponds to an example of an "excitation electrode".

[0035] The planar shape of the first excitation electrode 14 is a rectangle having short sides extending in the Z'-axis direction and long sides extending in the X-axis direction. The first excitation electrode 14a has a thickness in the Y'-axis direction. The second excitation electrode 14b has a similar shape.

[0036] The planar shapes of the first excitation electrode and the second excitation electrode are not limited to the above. The planar shapes of the first excitation electrode and the second excitation electrode may be rectangular with short sides extending in the X-axis direction. The planar shapes of the first excitation electrode and the second excitation electrode may be square, polygonal, circular, elliptical, or a combination of these.

[0037] The first extraction electrode 15a electrically connects the first excitation electrode 14a and the first connection electrode 16a, and the second extraction electrode 15b electrically connects the second excitation electrode 14b and the second connection electrode 16b. The first extraction electrode 15a is provided across the upper surface 11A and the lower surface 11B of the crystal piece 11, and the second extraction electrode 15b is provided on the lower surface 11B of the crystal piece 11.

[0038] The first connection electrode 16a and the second connection electrode 16b electrically connect the quartz crystal vibrating element 10 to the base member 30. The first connection electrode 16a and the second connection electrode 16b are provided on the lower surface 11B of the quartz crystal piece 11.

[0039] The first excitation electrode 14a, the first extraction electrode 15a, and the first connection electrode 16a are integrally provided. The second excitation electrode 14b, the second extraction electrode 15b, and the second connection electrode 16b are also integrally provided. The electrodes of the quartz crystal vibrating element 10 have a multi-layer structure in which, for example, a base layer and a surface layer are laminated in this order. For example, the base layer is a chromium (Cr) layer that has good adhesion to the quartz crystal blank 11, and the surface layer is a gold (Au) layer that has good chemical stability. The electrodes of the quartz crystal vibrating element 10 may contain aluminum (Al), molybdenum (Mo), or an aluminum-copper alloy (AlCu) mainly composed of aluminum. The electrodes of the quartz crystal vibrating element 10 may have a single-layer structure.

[0040] The base member 30 holds the quartz crystal vibrating element 10 in an excitable manner. The base member 30 includes a substrate 31, connection electrodes 33a and 33b, lead electrodes 34a and 34b, external electrodes 35a, 35b, 35c and 35d, and conductive holding members 36a and 36b.

[0041] The base 31 is a plate-shaped insulator having an upper surface 31A and a lower surface 31B that face each other in the thickness direction. The upper surface 31A and the lower surface 31B correspond to a pair of main surfaces of the base 31. The upper surface 31A is located on the side facing the quartz crystal vibrating element 10 and the lid member 40, and corresponds to a mounting surface on which the quartz crystal vibrating element 10 is mounted. From the viewpoint of suppressing thermal stress acting from the base 31 to the quartz crystal vibrating element 10 due to thermal history such as reflow, the base 31 is preferably made of a heat-resistant material. From the same viewpoint, the base 31 may be made of a material having a thermal expansion coefficient close to that of the quartz crystal blank 11. The base 31 is made of, for example, a ceramic substrate, a glass substrate, or a quartz crystal substrate.

[0042] The corner portion of the base 31 has a cutout side surface formed in a part of a cylindrical curved surface shape (also called a castellation shape). Note that the shape of the corner portion of the base 31 is not limited to this. The corner portion of the base may have a cutout side surface formed in a prismatic column shape, or may be a substantially right-angled corner portion without a cutout.

[0043] The connection electrodes 33a and 33b are electrically connected to the quartz crystal vibrating element 10. The connection electrode 33a is electrically connected to the connection electrode 16a of the quartz crystal vibrating element 10, and the connection electrode 33b is connected to the connection electrode 16b of the quartz crystal vibrating element 10.

[0044] The lead electrode 34a electrically connects the connection electrode 33a to the external electrode 35a, and the lead electrode 34b electrically connects the connection electrode 33b to the external electrode 35b. The lead electrodes 34a and 34b are provided on the upper surface 31A of the base 31.

[0045] The external electrodes 35a and 35b are external terminals for electrically connecting the quartz crystal vibrating element 10 to an external substrate. The external electrode 35a electrically connects the first excitation electrode 14a of the quartz crystal vibrating element 10 to the mounting substrate 130, and the external electrode 35b electrically connects the second excitation electrode 14b of the quartz crystal vibrating element 10 to the mounting substrate 130. One of the external electrodes 35c and 35d is a ground electrode that grounds the cover member 40, and the other is a dummy electrode that is not electrically connected to the quartz crystal vibrating element 10 and the cover member 40. Each of the external electrodes 35a, 35b, 35c, and 35d is continuously provided from the cutout side surfaces provided at the four corners of the base 31 to the lower surface 31B. In the example shown in FIG. 2, the external electrodes 35a and 35b are located at diagonal corners on the upper surface 31A of the base 31, and the external electrodes 35c and 35d are located at another diagonal corner on the upper surface 31A of the base 31. However, the external electrodes 35a, 35b, 35c, and 35d are not limited to the above. The external electrodes 35c and 35d may both be ground electrodes, or both may be dummy electrodes. The external electrodes 35c and 35d may be omitted. The external electrode 35c may be electrically connected to one of the external electrodes 35a and 35b, and the external electrode 35d may be electrically connected to the other of the external electrodes 35a and 35b.

[0046] The conductive holding members 36a and 36b electrically connect the base member 30 and the crystal vibration element 10, and mechanically hold the crystal vibration element 10. The conductive holding member 36a electrically connects the first connection electrode 16a of the crystal vibration element 10 to the connection electrode 33a of the base member 30. The conductive holding member 36b electrically connects the second connection electrode 16b of the crystal vibration element 10 to the connection electrode 33b of the base member 30. The conductive holding members 36a and 36b are a cured product of a conductive adhesive containing a thermosetting resin, a photocurable resin, or the like. The main component of the conductive holding members 36a and 36b is, for example, a silicone resin. The conductive holding members 36a and 36b contain conductive particles, and the conductive particles are, for example, metal particles containing silver (Ag).

[0047] The main component of the conductive holding members 36a, 36b is not limited to silicone resin, and may be, for example, epoxy resin, acrylic resin, etc. The conductive particles contained in the conductive holding members 36a, 36b are not limited to silver particles, and may be formed of other metals, conductive ceramics, conductive organic materials, etc. The conductive holding members 36a, 36b may include a conductive polymer.

[0048] The cover member 40 forms an internal space 20 between the cover member 40 and the base member 30 in which the crystal vibration element 10 is accommodated. The cover member 40 has a top wall portion 41, a side wall portion 42 extending from the outer edge of the top wall portion 41 toward the base member 30, and a flange portion 43 extending outward from the tip of the mounting substrate 130. The top wall portion 41 faces the base member 30 in the Y'-axis direction, sandwiching the crystal vibration element 10 therebetween. The side wall portion 42 surrounds the crystal vibration element 10 at a distance in the XZ'-plane direction. The flange portion 43 is provided in a frame shape in a plan view, and is provided in the cover member 40 closest to the base member 30. The material of the cover member 40 is preferably a conductive material, and more preferably a metal material with high airtightness. By making the cover member 40 out of a conductive material, the cover member 40 is provided with an electromagnetic shielding function that reduces the ingress and egress of electromagnetic waves into the internal space 20. In order to suppress the occurrence of thermal stress, the material of the cover member 40 is desirably a material having a thermal expansion coefficient close to that of the base member 30, such as an Fe-Ni-Co alloy whose thermal expansion coefficient at room temperature matches that of glass or ceramic over a wide temperature range. The cover member 40 is electrically connected to at least one of the external electrodes 35c, 35d by a ground member (not shown).

[0049] The joint 50 joins the base member 30 and the lid member 40 to seal the internal space 20. The joint 50 is provided in a frame shape around the entire circumference of the flange portion 43 of the base member 30, and is sandwiched between the lower surface of the flange portion 43 of the lid member 40 and the upper surface 31A of the base member 30. The joint 50 is provided by an insulating material. The joint 50 is provided by an organic adhesive containing, for example, an epoxy-based, vinyl-based, acrylic-based, urethane-based, or silicone-based resin. The material of the joint 50 is not limited to an organic adhesive, and may be an inorganic adhesive such as a silicon-based adhesive containing water glass or a calcium-based adhesive containing cement. The material of the joint 50 may be a low-melting point glass (for example, a lead borate-based or tin phosphate-based).

[0050] Next, the configuration of the quartz crystal vibrating element 10 according to the first embodiment will be described with reference to Fig. 4 and Fig. 5. Fig. 4 is a cross-sectional view of the quartz crystal vibrating element according to the first embodiment. Fig. 5 is a plan view of the quartz crystal vibrating element according to the first embodiment. Note that, for the sake of simplicity, the first extraction electrode 15a, the second extraction electrode 15b, the first connection electrode 16a, and the second connection electrode 16b are omitted from Figs. 4 and 5.

[0051] The quartz crystal vibrating element 10 has a high acoustic velocity region 17 and a low acoustic velocity region 18 in a region overlapping with the first excitation electrode 14a in a plan view. The high acoustic velocity region 17 is a region of the excitation region where the acoustic velocity is high. The low acoustic velocity region 18 is a region of the excitation region where the acoustic velocity is low, i.e., a region where the acoustic velocity is lower than that of the high acoustic velocity region 17.

[0052] As shown in FIG. 4, the thickness of the crystal blank 11 in the high sound velocity region 17 is the same as the thickness of the crystal blank 11 in the low sound velocity region 18. The thickness of the second excitation electrode 14b in the high sound velocity region 17 is the same as the thickness of the second excitation electrode 14b in the low sound velocity region 18. However, the thickness of the first excitation electrode 14a in the low sound velocity region 18 is greater than the thickness of the first excitation electrode 14a in the high sound velocity region 17. In other words, the high sound velocity region 17 is lighter than the low sound velocity region 18 by the difference in thickness of the first excitation electrode 14a. The sound velocity in the low sound velocity region 18 is lower than the sound velocity in the high sound velocity region 17 by adding mass by the difference in thickness of the first excitation electrode 14a.

[0053] The reason why the sound velocity in the low sound velocity region is smaller than the sound velocity in the high sound velocity region is not limited to the difference in thickness of the first excitation electrode. For example, the reason may be that the thickness of the second excitation electrode in the low sound velocity region is larger than the thickness of the second excitation electrode in the high sound velocity region. The reason may be that the thickness of the crystal piece in the low sound velocity region is larger than the thickness of the crystal piece in the high sound velocity region. The reason may be that the material of at least one of the first excitation electrode and the second excitation electrode is different between the low sound velocity region and the high sound velocity region. The reason may be that a mass-adding film that adds mass is further provided in a region that is outside the high sound velocity region in a plan view and overlaps with the low sound velocity region.

[0054] 5, in a plan view, the high acoustic velocity region 17 is provided in a region overlapping the center of the first excitation electrode 14a. The planar shape of the high acoustic velocity region 17 is a rectangle having a long side extending along the X-axis direction and a short side extending along the Z'-axis direction.

[0055] The planar shape of the high sound velocity region is not limited to the above. The planar shape of the high sound velocity region may be a rectangle having a short side extending along the X-axis direction and a long side extending along the Z'-axis direction. The planar shape of the high sound velocity region may be a square, polygon, circle, ellipse, or a combination thereof.

[0056] 5, in a plan view, the low acoustic velocity region 18 is provided in a region overlapping the end of the first excitation electrode 14a. The low acoustic velocity region 18 is provided in a continuous rectangular frame shape in the circumferential direction surrounding the center of the first excitation electrode 14a. The low acoustic velocity region 18 has a first low acoustic velocity region 18A, a second low acoustic velocity region 18B, a third low acoustic velocity region 18C, and a fourth low acoustic velocity region 18D.

[0057] The planar shape of the low sound speed region is not limited to a rectangular frame shape that is continuous in the circumferential direction. The planar shape of the low sound speed region may be a frame shape that extends along the contour of a polygonal shape, a circular shape, an elliptical shape, or a shape that is a combination of these. The low sound speed region may also be a frame shape that is discontinuous in the circumferential direction.

[0058] The first low sound speed region 18A is adjacent to the high sound speed region 17 on the negative side of the Z' axis and extends along the X-axis direction. The second low sound speed region 18B is adjacent to the high sound speed region 17 on the positive side of the Z' axis and extends along the X-axis direction. The third low sound speed region 18C is adjacent to the high sound speed region 17 on the positive side of the X-axis and extends along the Z' axis. The fourth low sound speed region 18D is adjacent to the high sound speed region 17 on the negative side of the X-axis and extends along the Z' axis. The end of the first low sound speed region 18A on the positive side of the X-axis is connected to the end of the third low sound speed region 18C on the negative side of the Z' axis, and the end of the first low sound speed region 18A on the negative side of the X-axis is connected to the end of the fourth low sound speed region 18D on the negative side of the Z' axis. The end of the second low sound speed region 18B on the positive side of the X-axis is connected to the end of the third low sound speed region 18C on the positive side of the Z'-axis, and the end of the second low sound speed region 18B on the negative side of the X-axis is connected to the end of the fourth low sound speed region 18D on the positive side of the Z'-axis.

[0059] In plan view, the end of the first low sound speed region 18A on the positive X-axis side overlaps with the end of the third low sound speed region 18C on the negative Z'-axis side, and the end of the first low sound speed region 18A on the negative X-axis side overlaps with the end of the fourth low sound speed region 18D on the negative Z'-axis side. The end of the second low sound speed region 18B on the positive X-axis side overlaps with the end of the third low sound speed region 18C on the positive Z'-axis side, and the end of the second low sound speed region 18B on the negative X-axis side overlaps with the end of the fourth low sound speed region 18D on the positive Z'-axis side.

[0060] The configuration of the low acoustic velocity region is not limited to the above. The third low acoustic velocity region and the fourth low acoustic velocity region may be omitted. That is, the high acoustic velocity region, the first low acoustic velocity region, and the second low acoustic velocity region may extend parallel to the X-axis direction and be provided in a strip shape from the end of the first excitation electrode on the negative side of the X-axis to the end on the positive side of the X-axis in a plan view. The first low acoustic velocity region and the second low acoustic velocity region may be omitted. That is, the high acoustic velocity region, the third low acoustic velocity region, and the fourth low acoustic velocity region may extend parallel to the Z'-axis direction and be provided in a strip shape from the end of the first excitation electrode on the negative side of the Z'-axis to the end on the positive side of the Z'-axis in a plan view. The end of the first low acoustic velocity region on the positive side of the X-axis may be separated from the third low acoustic velocity region, and the end of the first low acoustic velocity region on the negative side of the X-axis may be separated from the fourth low acoustic velocity region. The end of the second low sound speed region on the positive side of the X-axis may be spaced apart from the third low sound speed region, and the end of the second low sound speed region on the negative side of the X-axis may be spaced apart from the fourth low sound speed region.

[0061] In addition, the positional relationship of the first low sound velocity region, the second low sound velocity region, the third low sound velocity region, and the fourth low sound velocity region is not limited to the above. The first low sound velocity region may be adjacent to the high sound velocity region on the positive side of the Z' axis, and the second low sound velocity region may be adjacent to the high sound velocity region on the negative side of the Z' axis. The third low sound velocity region may be adjacent to the high sound velocity region on the negative side of the X axis, and the fourth low sound velocity region may be adjacent to the high sound velocity region on the positive side of the X axis. One of the first low sound velocity region and the second low sound velocity region may be adjacent to the high sound velocity region on the negative side of the X axis, and the other may be adjacent to the high sound velocity region on the positive side of the X axis. One of the third low sound velocity region and the fourth low sound velocity region may be adjacent to the high sound velocity region on the negative side of the Z' axis, and the other may be adjacent to the high sound velocity region on the positive side of the Z' axis.

[0062] As shown in FIG. 4 and FIG. 5, the dimension of the crystal blank 11 along the Y'-axis direction is defined as thickness Tp. The dimension of the first excitation electrode 14a in the high acoustic velocity region 17 along the Y'-axis direction is defined as thickness Te1. The dimension of the first excitation electrode 14a in the low acoustic velocity region 18 along the Y'-axis direction is defined as thickness Te1+Tf. The dimension of the second excitation electrode 14b along the Y'-axis direction is defined as thickness Te2. The dimension of the crystal blank 11 along the X-axis direction is defined as length Px, and the dimension of the crystal blank 11 along the Z'-axis direction is defined as length Pz. The dimension of the first excitation electrode 14a along the X-axis direction is defined as length Ex, and the dimension of the first excitation electrode 14a along the Z'-axis direction is defined as length Ez. The dimension of the first low acoustic velocity region 18A along the Z'-axis direction is defined as length Wz1. The dimension of the second low acoustic velocity region 18B along the Z'-axis direction is defined as length Wz2. The dimension of the third low acoustic velocity region 18C along the X-axis direction is defined as length Wx1. The dimension of the fourth low sound speed region 18D along the X-axis direction is length Wx2. The dimension of the first low sound speed region 18A along the X-axis direction is length Lx1. The dimension of the second low sound speed region 18B along the X-axis direction is length Lx2. The dimension of the third low sound speed region 18C along the Z'-axis direction is length Lz1. The dimension of the fourth low sound speed region 18D along the Z'-axis direction is length Lz2.

[0063] 5, when the first low acoustic velocity region 18A has a pair of ends parallel to the X-axis direction in a plan view, the length Wz1 is determined by measuring the distance in the Z'-axis direction between a pair of ends of the first low acoustic velocity region 18A parallel to the X-axis direction. Of the pair of ends of the first low acoustic velocity region 18A parallel to the X-axis direction, one end is the boundary between the high acoustic velocity region 17 and the first low acoustic velocity region 18A, and the other end is the outer edge of the first excitation electrode 14a on the negative Z'-axis side.

[0064] Similarly, the length Wz2 is determined by measuring the distance in the Z'-axis direction between a pair of ends of the second low acoustic velocity region 18B parallel to the X-axis direction. Of the pair of ends of the second low acoustic velocity region 18B parallel to the X-axis direction, one end is the boundary between the high acoustic velocity region 17 and the second low acoustic velocity region 18B, and the other end is the outer edge of the first excitation electrode 14a on the positive Z'-axis direction side.

[0065] Similarly, the length Wx1 is determined by measuring the distance in the X-axis direction between a pair of ends parallel to the Z'-axis direction of the third low sound velocity region 18C. Of the pair of ends parallel to the Z'-axis direction of the third low sound velocity region 18C, one end is the boundary between the high sound velocity region 17 and the third low sound velocity region 18C, and the other end is the outer edge of the first excitation electrode 14a on the positive X-axis direction side.

[0066] Similarly, the length Wx2 is determined by measuring the distance in the X-axis direction between a pair of ends parallel to the Z'-axis direction of the fourth low sound velocity region 18D. Of the pair of ends parallel to the Z'-axis direction of the fourth low sound velocity region 18D, one end is the boundary between the high sound velocity region 17 and the fourth low sound velocity region 18D, and the other end is the outer edge of the first excitation electrode 14a on the negative X-axis direction side.

[0067] However, when the planar shape of the high sound velocity region 17 is polygonal, circular, elliptical, or a combination thereof, and when the planar shape of the first excitation electrode 14a is polygonal, circular, elliptical, or a combination thereof, and the first low sound velocity region 18A does not have a pair of ends parallel to the X-axis direction in a planar view, the length Wz1 is determined by a method other than the above. For example, the length Wz1 may be determined by dividing the area of ​​the first low sound velocity region 18A in a planar view by the dimension of the first low sound velocity region 18A in the X-axis direction. The length Wz1 may also be determined by measuring multiple dimensions along the Z'-axis direction of the first low sound velocity region 18A at multiple positions in the X-axis direction and calculating the average value of the multiple dimensions. When measuring multiple dimensions along the Z'-axis direction, the measurement positions of the dimensions along the Z'-axis direction may be determined, for example, at equal intervals in the X-axis direction, or may be determined arbitrarily. The number of measurement positions of the dimensions along the Z'-axis direction may be determined arbitrarily. When calculating the average value of multiple dimensions along the Z'-axis direction, the average value of the remaining dimensions excluding at least one of the maximum and minimum values ​​may be calculated. The lengths Wz2, Wx1, and Wx2 may also be specified in the same manner as the length Wz1.

[0068] 5, when the first low acoustic velocity region 18A has a pair of ends parallel to the Z'-axis direction in a plan view, the length Lx1 is determined by measuring the distance in the X-axis direction between the pair of ends parallel to the Z'-axis direction of the first low acoustic velocity region 18A. Of the pair of ends parallel to the Z'-axis direction of the first low acoustic velocity region 18A, one end is the outer edge of the first excitation electrode 14a on the positive X-axis direction side, and the other end is the outer edge of the first excitation electrode 14a on the negative X-axis direction side.

[0069] Similarly, the length Lx2 is determined by measuring the distance in the X-axis direction between a pair of ends parallel to the Z'-axis direction of the second low sound speed region 18B. Of the pair of ends parallel to the Z'-axis direction of the second low sound speed region 18B, one end is the outer edge of the first excitation electrode 14a on the positive X-axis direction side, and the other end is the outer edge of the first excitation electrode 14a on the negative X-axis direction side.

[0070] Similarly, the length Lz1 is determined by measuring the distance in the Z'-axis direction between a pair of ends of the third low sound velocity region 18C parallel to the X-axis direction. Of the pair of ends of the third low sound velocity region 18C parallel to the X-axis direction, one end is the outer edge of the first excitation electrode 14a on the positive Z'-axis direction side, and the other end is the outer edge of the first excitation electrode 14a on the negative Z'-axis direction side.

[0071] Similarly, the length Lz2 is determined by measuring the distance in the Z'-axis direction between a pair of ends parallel to the X-axis direction of the fourth low sound speed region 18D. Of the pair of ends parallel to the X-axis direction of the fourth low sound speed region 18D, one end is the outer edge of the first excitation electrode 14a on the positive side of the Z'-axis, and the other end is the outer edge of the first excitation electrode 14a on the negative side of the Z'-axis.

[0072] However, when the planar shape of the high sound velocity region 17 is polygonal, circular, elliptical, or a combination thereof, and when the planar shape of the first excitation electrode 14a is polygonal, circular, elliptical, or a combination thereof, and the first low sound velocity region 18A does not have a pair of ends parallel to the Z'-axis direction in a planar view, the length Lx1 is determined by a method other than the above. For example, the length Lx1 may be determined by dividing the area of ​​the first low sound velocity region 18A in a planar view by the dimension of the first low sound velocity region 18A in the Z'-axis direction. The length Lx1 may also be determined by measuring multiple dimensions along the X-axis direction of the first low sound velocity region 18A at multiple positions in the Z'-axis direction and calculating the average value of the multiple dimensions. When measuring multiple dimensions along the X-axis direction, the measurement positions of the dimensions along the X-axis direction may be determined, for example, at equal intervals in the Z'-axis direction, or may be determined arbitrarily. The number of measurement positions of the dimensions along the X-axis direction may be determined arbitrarily. When calculating the average value of multiple dimensions along the X-axis direction, the average value of the remaining dimensions excluding at least one of the maximum and minimum values ​​may be calculated. The length Lx1 may be specified as the dimension of the first excitation electrode 14a along the X-axis direction on a tangent line extending in the X-axis direction in contact with the boundary between the high sound velocity region 17 and the first low sound velocity region 18A. The lengths Lx2, Lz1, and Lz2 may also be specified in the same manner as the length Lx1.

[0073] The length Ez of the first excitation electrode 14a in the Z'-axis direction corresponds to an example of the "length Ea of the excitation electrode in the first direction". The length Ex of the first excitation electrode 14a in the X-axis direction corresponds to an example of the "length Eb of the excitation electrode in the second direction". The length Wz1 of the first low acoustic velocity region 18A in the Z'-axis direction corresponds to an example of the "length Wa1 of the first low acoustic velocity region in the first direction". The length Wz2 of the second low acoustic velocity region 18B in the Z'-axis direction corresponds to an example of the "length Wa2 of the second low acoustic velocity region in the first direction". The length Wx1 of the third low acoustic velocity region 18C in the X-axis direction corresponds to an example of the "length Wb1 of the third low acoustic velocity region in the second direction". The length Wx2 of the fourth low acoustic velocity region 18D in the X-axis direction corresponds to an example of the "length Wb2 of the fourth low acoustic velocity region in the second direction". The length Lx1 of the first low sound speed region 18A in the X-axis direction corresponds to an example of the "length Lb1 of the first low sound speed region in the second direction". The length Lx2 of the second low sound speed region 18B in the X-axis direction corresponds to an example of the "length Lb2 of the second low sound speed region in the second direction". The length Lz1 of the third low sound speed region 18C in the Z'-axis direction corresponds to an example of the "length La1 of the third low sound speed region in the first direction". The length Lz2 of the fourth low sound speed region 18D in the Z'-axis direction corresponds to an example of the "length La2 of the fourth low sound speed region in the first direction".

[0074] In addition, the lengths Ea, Eb, Wa1, Wa2, Wb1, Wb2, Lb1, Lb2, La1, and La2 are not limited to the above. For example, the length Wz2 may correspond to the length Wa1, and the length Wz1 may correspond to the length Wa2. The length Wx2 may correspond to the length Wb1, and the length Wx1 may correspond to the length Wb2. When the length Ea corresponds to the length Ex, and the length Eb corresponds to the length Ez, one of the lengths Wx1 and Wx2 corresponds to the length Wa1, the other of the lengths Wx1 and Wx2 corresponds to the length Wa2, one of the lengths Wz1 and Wz2 corresponds to the length Wb1, and the other of the lengths Wz1 and Wz2 corresponds to the length Wb2. In addition, the length Lx2 may correspond to the length Lb1, and the length Lx1 may correspond to the length Lb2. The length Lz2 may correspond to the length La1, and the length Lz1 may correspond to the length La2. When the length Ea corresponds to the length Ex, and the length Eb corresponds to the length Ez, one of the lengths Lz1 and Lz2 corresponds to the length Lb1, the other of the lengths Lz1 and Lz2 corresponds to the length Lb2, one of the lengths Lx1 and Lx2 corresponds to the length La1, and the other of the lengths Lx1 and Lx2 corresponds to the length La2.

[0075] As described above, the thickness Tp of the crystal blank 11 is the same in the high acoustic velocity region 17 and the low acoustic velocity region 18. Similarly, the thickness Te2 of the second excitation electrode 14b is the same in the high acoustic velocity region 17 and the low acoustic velocity region 18. The thickness Te1 of the first excitation electrode 14a in the high acoustic velocity region 17 is, for example, the thickness of the first excitation electrode 14a in the center of the high acoustic velocity region 17 when viewed in a plan view. The thickness Te1 may be the minimum value, minimum value, or average value of the thickness of the first excitation electrode 14a in the high acoustic velocity region 17. The thickness Te1+Tf of the first excitation electrode 14a in the low acoustic velocity region 18 is, for example, the thickness of the first excitation electrode 14a in the center of the first low acoustic velocity region 18A, the second low acoustic velocity region 18B, the third low acoustic velocity region 18C, or the fourth low acoustic velocity region 18D when viewed in a plan view. The thickness Te1+Tf may be a maximum value, a minimum value, or an average value of the thickness of the first excitation electrode 14a in the low acoustic velocity region 18. For example, the thickness Te1+Tf may be an average value of the thickness of the first excitation electrode 14a in the central portion of each of the first low acoustic velocity region 18A, the second low acoustic velocity region 18B, the third low acoustic velocity region 18C, and the fourth low acoustic velocity region 18D.

[0076] 4, the thickness of the first excitation electrode 14a changes stepwise at the boundary between the high sound velocity region 17 and the low sound velocity region 18, but is not limited to this. The thickness of the first excitation electrode 14a may change in a tapered, beveled, or convex shape at the boundary between the high sound velocity region 17 and the low sound velocity region 18.

[0077] In the example shown in FIG. 5, the length Wz1 of the first low sound velocity region 18A in the Z'-axis direction is substantially equal to the length Wz2 of the second low sound velocity region 18B in the Z'-axis direction (Wz1≈Wz2). The sum of the lengths Wz1 and Wz2 is 50% or more of the length Ez of the first excitation electrode 14a in the Z'-axis direction. In addition, from the viewpoint of ensuring the high sound velocity region 17, the sum of the lengths Wz1 and Wz2 is 96% or less of the length Ez. Furthermore, the length Wz1 may be different from the length Wz2 as long as both the lengths Wz1 and Wz2 are 20% or more of the length Ez. In other words, as long as the relationships 0.2≦Wz1 / Ez, 0.2≦Wz2 / Ez, and 0.5≦(Wz1+Wz2) / Ez≦0.96 are satisfied, the relationship Wz1≠Wz2 may be satisfied, or the relationship Wz1≒Wz2 may be satisfied.

[0078] It is desirable that both of the lengths Wz1 and Wz2 are 25% or more of the length Ez. From the viewpoint of ensuring the high sound velocity region 17, it is desirable that both of the lengths Wz1 and Wz2 are 48% or less of the length Ez. In other words, it is desirable that the relationships 0.25≦Wz1 / Ez≦0.48 and 0.25≦Wz2 / Ez≦0.48 are satisfied. It is desirable that the relationship Wz1≒Wz2 is satisfied in order to achieve a good balance of mechanical strength, etc.

[0079] Similarly, the length Wx1 of the third low sound velocity region 18C in the X-axis direction is approximately equal to the length Wx2 of the fourth low sound velocity region 18D in the X-axis direction (Wx1≒Wx2). The sum of the lengths Wx1 and Wx2 is 50% or more of the length Ex of the first excitation electrode 14a in the X-axis direction. In addition, from the viewpoint of ensuring the high sound velocity region 17, the sum of the lengths Wx1 and Wx2 is 96% or less of the length Ex. Furthermore, if both of the lengths Wx1 and Wx2 are 20% or more of the length Ex, the length Wx1 may be different from the length Wx2. In other words, if the relationships 0.2≦Wx1 / Ex, 0.2≦Wx2 / Ex, and 0.5≦(Wx1+Wx2) / Ex≦0.96 are satisfied, the relationship Wx1≠Wx2 may be satisfied, or the relationship Wx1≒Wx2 may be satisfied. It is desirable that the relationships 0.25≦Wx1 / Ex≦0.48 and 0.25≦Wx2 / Ex≦0.48 hold, and it is desirable that the relationship Wx1≈Wx2 hold.

[0080] 5, the length Lx1 of the first low acoustic velocity region 18A in the X-axis direction and the length Lx2 of the second low acoustic velocity region 18B in the Z-axis direction are substantially equal to the length Ex of the first excitation electrode 14a in the X-axis direction (Lx1≒Lx2≒Ex). The length Lz1 of the third low acoustic velocity region 18C in the Z'-axis direction and the length Lz2 of the fourth low acoustic velocity region 18D in the Z'-axis direction are substantially equal to the length Ez of the first excitation electrode 14a in the Z'-axis direction (Lz1≒Lz2≒Ez).

[0081] In addition, as long as the first low sound speed region 18A and the second low sound speed region 18B function, the length Lx1 and the length Lx2 may be smaller than the length Ex. That is, in a plan view, the end of the first low sound speed region 18A on the positive side of the X-axis may be spaced away from the end of the first excitation electrode 14a on the positive side of the X-axis toward the negative side of the X-axis, and the end of the first low sound speed region 18A on the negative side of the X-axis may be spaced away from the end of the first excitation electrode 14a on the negative side of the X-axis toward the positive side of the X-axis. However, in order to suppress the first low sound speed region 18A and the second low sound speed region 18B from breaking down the vibration form and splitting the waveform, it is desirable that both the length Lx1 and the length Lx2 are 80% or more of the length Ex. That is, it is desirable that the relationships 0.8≦Lx1 / Ex≦1.0 and 0.8≦Lx2 / Ex≦1.0 are satisfied.

[0082] Similarly, as long as the third low acoustic velocity region 18C and the fourth low acoustic velocity region 18D function, the length Lz1 and the length Lz2 may be smaller than the length Ez. That is, in a plan view, the end of the third low acoustic velocity region 18C on the Z'-axis positive side may be spaced apart from the end of the first excitation electrode 14a on the Z'-axis positive side toward the Z'-axis negative side, and the end of the fourth low acoustic velocity region 18D on the Z'-axis negative side may be spaced apart from the end of the first excitation electrode 14a on the Z'-axis negative side toward the X-axis positive side. However, in order to prevent the third low acoustic velocity region 18C and the fourth low acoustic velocity region 18D from breaking down the vibration form and splitting the waveform, it is desirable that both the length Lz1 and the length Lz2 are 80% or more of the length Ez. That is, it is desirable that the relationships 0.8≦Lz1 / Ez≦1.0 and 0.8≦Lz2 / Ez≦1.0 are satisfied.

[0083] Next, with reference to Figs. 6 to 9, a simulation result of an example based on the first embodiment will be described. Figs. 6 to 9 are diagrams showing the simulation result based on the first embodiment. The quartz crystal vibration element according to the example has a high sound velocity region where the thickness of the first excitation electrode is Te1 and a low sound velocity region where the thickness of the first excitation electrode is Te1+Tf. The quartz crystal vibration element according to the comparative example has a uniform thickness of the first excitation electrode of Te1. The gray scale in Figs. 6 to 9 indicates the magnitude of displacement. The direction of displacement is opposite between the white area and the black area in the gray scale. (Example) Tp=1.52μm Te1 = Te2 = 0.08 μm Tf=0.02μm Px = Pz = 120 μm Ex=100μm Ez=80μm Wx1 = Wx2 = Wx = 40 μm Wz1 = Wz2 = Wz = 30 μm (Comparative Example) Tp=1.52μm Te1 = Te2 = 0.08 μm Tf=0μm Px = Pz = 120 μm Ex=100μm Ez=80μm Wx1 = Wx2 = Wx = 0 μm Wz1 = Wz2 = Wz = 0 μm

[0084] As shown in Fig. 6, the frequency of the main mode in the embodiment is about 945 MHz, and the frequency of the main mode in the comparative example is 965 MHz. The frequency interval of each mode in the embodiment is wider than the frequency interval of each mode in the comparative example. In other words, it is easier to separate the main mode from the inharmonic mode in the embodiment than in the comparative example.

[0085] As shown in FIG. 7, the electromechanical coupling coefficient k of the S0 mode, which is the main mode in the example, is 7.40%, which is improved from the electromechanical coupling coefficient k of the S0 mode, which is the main mode in the comparative example, which is 6.87%. Comparing the S0 displacement distributions of the example and the comparative example, the phase change in the example is earlier in the low sound velocity region than the phase change in the comparative example. The S0 displacement distribution in the example is divided at the center in both the Z'-axis direction and the X-axis direction, and has two maxima and one minimum. In the S0 displacement distribution of the example, two maxima exist in the low sound velocity region, and one minimum exists in the high sound velocity region.

[0086] As shown in FIG. 8, the electromechanical coupling coefficient k of the S1Z mode, which is an inharmonic mode in the embodiment, is 0.15%, which is reduced from the electromechanical coupling coefficient k of the S1Z mode, which is an inharmonic mode in the comparative example, which is 2.44%. Since the S1 mode has a shorter wavelength in the X direction than the S0 mode, the influence of the phase change due to the low sound speed region is large. In the comparative example, the vibration region extending in the X-axis direction at the center of the Z'-axis direction, i.e., the white region in the gray scale of FIG. 8, is divided in the center of the X-axis direction in the embodiment and spreads in the Z'-axis direction at the end of the X-axis direction. As a result, the positive and negative charges are canceled, and the S1Z displacement in the embodiment is suppressed in both the Z'-axis direction and the X-axis direction.

[0087] As shown in Fig. 9, the electromechanical coupling coefficient k of the S1X mode, which is an inharmonic mode in the embodiment, is 1.61%, which is reduced from the electromechanical coupling coefficient k of the S1X mode, which is an inharmonic mode in the comparative example, which is 2.17%. In the comparative example, the vibration region extending in the Z'-axis direction at the center in the X-axis direction, i.e., the white region in the gray scale in Fig. 9, is divided at the center in the Z'-axis direction in the embodiment and spreads in the X-axis direction. Therefore, the vibration region extending in the Z'-axis direction at both ends in the X-axis direction in the comparative example, i.e., the black region in the gray scale in Fig. 9, is divided into four corners by the white region spreading in the X-axis direction in the embodiment.

[0088] Next, the influence of the dimensions of the low sound velocity region on the electromechanical coupling coefficient k will be described with reference to Figs. 10 to 12. Figs. 10 to 12 are graphs showing the influence of the planar dimensions of the low sound velocity region. Based on the first embodiment, k in the S0 mode and the S1Z mode were calculated with Wx1=Wx2=Wx and Wz1=Wz2=Wz as variables. The horizontal axis of the graph (A) in Fig. 10 is Wx / Tp, and the horizontal axis of the graph (B) in Fig. 10 is Wz / Tp. The vertical axis of the graphs (A) and (B) in Fig. 10 is k in the S0 mode (hereinafter also referred to as "k_S0"). Fig. 11 is a graph showing the distribution of k_S0 with the horizontal axis being Wx / Ex and the vertical axis being Wz / Ez. Fig. 12 is a graph showing the distribution of k in the S1Z mode (hereinafter also referred to as "k_S1Z") with the horizontal axis being Wx / Ex and the vertical axis being Wz / Ez. k_S0 and k_S1Z were calculated under the following conditions based on the first embodiment. Note that, under the following conditions, when Tf=0 μm, k_S0=6.87%. Tp=1.52μm Te1 = Te2 = 0.08 μm Tf=0.02μm Px = Pz = 120 μm Ex=100μm Ez=80μm Wx1=Wx2=Wx:variable Wz1=Wz2=Wz:variable

[0089] 10, when 16.5≦Wx / Tp and 13.2≦Wz / Tp, i.e., 0.25≦Wx / Ex and 0.25≦Wz / Ez, k_S0 is improved compared to k_S0=6.87% of the comparative example. Also, when Wx / Tp≦31.6 and Wz / Tp≦25.0, i.e., Wx / Ex≦0.48 and Wz / Ez≦0.48, k_S0 is improved compared to k_S0=6.87% of the comparative example.

[0090] The dashed and dotted lines in the graph of Fig. 11 indicate the range in which k_S0 is improved from k_S0=6.87% in the comparative example. When the relationships 0.25≦Wx / Ex≦0.48 and 0.25≦Wz / Ez≦0.48, which are the range surrounded by the dashed and dotted lines, are satisfied, k_S0 is 7.1%≦k_S0. In addition, when the relationship 0.8<5.0×(Wx / Ex) is satisfied, which is the range surrounded by the dotted line, k_S0 is 7.1%≦k_S0. 2 +4.0×(Wz / Ez) 2 When the relationships Wx / Ex≦0.48 and Wz / Ez≦0.48 are satisfied, then 6.90%≦k_S0 is satisfied. In particular, when the relationships Wx / Ex=0.35±0.05 and Wz / Ez=0.35±0.05 are satisfied, k_S0 is maximized.

[0091] The dotted line in the graph of FIG. 12 indicates the range where k_S1Z is particularly reduced. When the relationship of 0.30≦Wx / Ex≦0.43 and 0.30≦Wz / Ez≦0.48 is satisfied, k_S1Z≦1.0% is satisfied. When the relationship of 0.30≦Wx / Ex≦0.46 and 0.31≦Wz / Ez≦0.46 is satisfied, k_S1Z≦1.0% is satisfied. When the relationship of 0.30≦Wx / Ex≦0.47 and 0.34≦Wz / Ez≦0.44 is satisfied, k_S1Z is ≦1.0%. In particular, when the relationship of Wx / Ex=0.40±0.05 and Wz / Ez=0.40±0.05 is satisfied, k_S1Z is minimized.

[0092] Next, the influence of Tf and Te1 on k_S0 will be described with reference to Fig. 13 and Fig. 14. Fig. 13 is a graph showing the influence of the thickness of the low sound velocity region. Fig. 14 is a graph showing the influence of the thickness of the high sound velocity region.

[0093] 13, the horizontal axis represents Wx, and the vertical axis represents k_S0 calculated under the following conditions based on the first embodiment. Note that under the following conditions, when Tf=0 μm, k_S0=6.87%. Tp=1.52μm Te1 = Te2 = Te = 0.08 μm Tf:0.01μm, 0.02μm, 0.03μm, 0.05μm, 0.07μm, 0.10μm, Px = Pz = 120 μm Ex = 100 μm Ez = 80 μm Wx1 = Wx2 = Wx: variable Wz1 = Wz2 = Wz = 30 μm

[0094] When the relationship 25.0 ≤ Wx, that is, 0.25 ≤ Wx / Ex holds, k_S0 improves and 6.87% < k_S0. In the range 25.0 ≤ Wx ≤ 48.0, that is, 0.25 ≤ Wx / Ex ≤ 0.48, for any of Tf = 0.01 μm, 0.02 μm, 0.03 μm, 0.05 μm, 0.07 μm, 0.10 μm, k_S0 shows a similar trend with respect to Wx. That is, in the range 0.01 μm ≤ Tf ≤ 0.10 μm, that is, 0.125 ≤ Tf / Te1 ≤ 1.25, the condition for k_S0 to increase does not depend on Tf, and 6.87% < k_S0 in the range 0.25 ≤ Wx / Ex ≤ 0.48.

[0095] The horizontal axis of the graph in Fig. 14 shows Wx, and the vertical axis shows k_S0 calculated based on the following conditions in the first embodiment. When Te1 = Te2 = 0.05 μm and Tf = 0 μm under the following conditions, k_S0 = 6.87%. Tp = 1.52 m Te1 = Te2 = Te: 0.02 μm, 0.05 μm, 0.08 μm, 0.10 μm, 0.15 μm, 0.20 μm, 0.30 μm Tf = 0.02 μm Px = Pz = 120 μm Ex = 100 μm Ez = 80 μm Wx1 = Wx2 = Wx: variable Wz1 = Wz2 = Wz = 30 μm

[0096] When the relationship 20μm ≦ Wx ≦ 48μm, that is, 0.20 ≦ Wx / Ex ≦ 0.48 holds, k_S0 improves and 6.74% < k_S0. When the relationship 25μm ≦ Wx ≦ 48μm, that is, 0.25 ≦ Wx / Ex ≦ 0.48 holds, k_S0 further improves and 7.00% ≦ k_S0. In the range of 0.20 ≦ Wx / Ex ≦ 0.48, for any of Te = 0.02μm, 0.05μm, 0.08μm, 0.10μm, 0.15μm, 0.20μm, 0.30μm, k_S0 shows a similar trend with respect to Wx. That is, in the range of 0.02μm ≦ Te ≦ 0.30μm, that is, 0.132 ≦ Te / Tp ≦ 0.197, the condition for k_S0 to improve does not depend on Te, 6.87% < k_S0 in the range of 0.20 ≦ Wx / Ex ≦ 0.48, and 7.00% ≦ k_S0 in the range of 0.25 ≦ Wx / Ex ≦ 0.48.

[0097] As described above, according to this embodiment, when the length of the first excitation electrode 14a in the Z'-axis direction is Ez, the length of the first low sound velocity region 18A in the Z'-axis direction is Wz1, and the length of the second low sound velocity region 18B in the Z'-axis direction is Wz2, the relationships 0.20 ≦ Wz1 / Ez, and 0.20 ≦ Wz2 / Ez, and 0.50 ≦ (Wz1 + Wz2) / Ez ≦ 0.96 hold. Desirably, the relationships 0.25 ≦ Wz1 / Ez ≦ 0.48, and 0.25 ≦ Wz2 / Ez ≦ 0.48 hold.

[0098] According to this, spurious vibration in the Z'-axis direction can be suppressed, and the electromechanical coupling coefficient k of the main mode can be improved.

[0099] Also, according to this embodiment, when the length of the first excitation electrode 14a in the X-axis direction is Ex, the length of the first low sound velocity region 18A in the X-axis direction is Wx1, and the length of the second low sound velocity region 18B in the X-axis direction is Wx2, the relationships 0.20 ≦ Wx1 / Ex, and 0.20 ≦ Wx2 / Ex, and 0.50 ≦ (Wx1 + Wx2) / Ex ≦ 0.96 hold. Desirably, the relationships 0.25 ≦ Wx1 / Ex ≦ 0.48, and 0.25 ≦ Wx2 / Ex ≦ 0.48 hold.

[0100] This makes it possible to suppress spurious vibration in the X-axis direction and improve the electromechanical coupling coefficient k of the main mode.

[0101] In order to suppress spurious vibrations in both the Z'-axis direction and the X-axis direction and further improve the electromechanical coupling coefficient k of the main mode, it is desirable that both of the following relationships are satisfied: 0.20≦Wz1 / Ez, 0.20≦Wz2 / Ez, and 0.50≦(Wz1+Wz2) / Ez≦0.96, and 0.20≦Wx1 / Ex, 0.20≦Wx2 / Ex, and 0.50≦(Wx1+Wx2) / Ex≦0.96. It is even more desirable that both of the following relationships are satisfied: 0.25≦Wz1 / Ez≦0.48, and 0.25≦Wz2 / Ez≦0.48, and 0.25≦Wx1 / Ex≦0.48, and 0.25≦Wx2 / Ex≦0.48.

[0102] According to the present embodiment, Wz1=Wz2=Wz, Wx1=Wx2=Wx, and 0.8<5.0×(Wz / Ez) 2 +4.0×(Wx / Ex) 2 , and the relationships Wz / Ez≦0.48 and Wx / Ex≦0.48 hold.

[0103] This makes it possible to improve the electromechanical coupling coefficient k of the main mode.

[0104] Furthermore, according to this embodiment, when the length of the first low sound velocity region 18A in the X-axis direction is Lx1 and the length of the second low sound velocity region 18B in the X-axis direction is Lx2, the relationships 0.8≦Lx1 / Ex≦1.0 and 0.8≦Lx2 / Ex≦1.0 hold.

[0105] This makes it possible to prevent the first low sound velocity region 18A and the second low sound velocity region 18B from destroying the vibration form and splitting the waveform.

[0106] Furthermore, according to this embodiment, when the length of the third low sound speed region 18C in the Z'-axis direction is Lz1 and the length of the fourth low sound speed region 18D in the Z'-axis direction is Lz2, the relationships 0.8≦Lz1 / Ez≦1.0 and 0.8≦Lz2 / Ez≦1.0 hold.

[0107] This makes it possible to prevent the third low sound velocity region 18C and the fourth low sound velocity region 18D from destroying the vibration form and splitting the waveform.

[0108] Furthermore, according to this embodiment, the relationships Wx / Ex=0.35±0.05 and Wz / Ez=0.35±0.05 hold.

[0109] According to this, within the range of 0.25≦Wz / Ez≦0.48 and 0.25≦Wx / Ex≦0.48, or within the range of 0.8<5.0×(Wz / Ez) 2 +4.0×(Wx / Ex) 2 , and within the ranges of Wz / Ez≦0.48 and Wx / Ex≦0.48, the electromechanical coupling coefficient k of the main mode can be maximized.

[0110] Furthermore, according to this embodiment, the relationships Wx / Ex=0.40±0.05 and Wz / Ez=0.40±0.05 hold.

[0111] According to this, within the range of 0.25≦Wz / Ez≦0.48 and 0.25≦Wx / Ex≦0.48, or within the range of 0.8<5.0×(Wz / Ez) 2 +4.0×(Wx / Ex) 2 , and the electromechanical coupling coefficient k of the inharmonic mode S1Z can be minimized within the ranges of Wz / Ez≦0.48 and Wx / Ex≦0.48.

[0112] Moreover, according to this embodiment, the thickness Te1+Tf of the first excitation electrode 14a in the low acoustic velocity region 18 is greater than the thickness Te1 of the first excitation electrode 14a in the high acoustic velocity region 17.

[0113] According to this, due to the difference in thickness of the first excitation electrode 14a, the sound velocity of the low sound velocity region 18 can be made smaller than that of the high sound velocity region 17. In other words, the high sound velocity region 17 and the low sound velocity region 18 can be formed by further laminating a metal on the end portion of the first excitation electrode 14a, or by thinning the central portion of the first excitation electrode 14a by etching or the like.

[0114] In this embodiment, the first excitation electrode 14a has a single-layer structure, but is not limited thereto. For example, the first excitation electrode 14a in the low acoustic velocity region 18 may have a multi-layer structure, so that the thickness of the first excitation electrode 14a in the low acoustic velocity region 18 may be greater than the thickness of the first excitation electrode 14a in the high acoustic velocity region 17. Specifically, a first metal layer with a uniform thickness Te1 may be provided in the high acoustic velocity region 17 and the low acoustic velocity region 18, and a second metal layer with a thickness Tf may be further provided in the low acoustic velocity region 18. The second metal layer may be provided between the first metal layer and the crystal blank, or may be provided on the opposite side of the first metal layer from the crystal blank.

[0115] In addition, the present invention is not limited to a configuration in which the high sound velocity region 17 and the low sound velocity region 18 are formed only by the difference in thickness of the first excitation electrode 14a. For example, the high sound velocity region and the low sound velocity region may be formed by making the thickness of the end portion of the second excitation electrode larger than the thickness of the central portion. In addition, the high sound velocity region and the low sound velocity region may be formed by making the thickness of the end portions of both the first excitation electrode and the second excitation electrode larger than the thickness of the central portion.

[0116] Other embodiments will be described below. Note that the same or similar components as those in the first embodiment are denoted by the same or similar reference numerals, and the description thereof will be omitted as appropriate. Also, similar effects due to similar components will not be mentioned one by one.

[0117] <Second embodiment> Next, the configuration of a quartz crystal vibrating element 210 according to the second embodiment will be described with reference to Fig. 15. Fig. 15 is a plan view of the quartz crystal vibrating element according to the second embodiment.

[0118] As shown in FIG. 15, the quartz crystal vibrating element 210 has a high acoustic velocity region 217, a first low acoustic velocity region 218A, and a second low acoustic velocity region 218B. In a plan view, the high acoustic velocity region 217 is provided in a region extending in the X-axis direction at the center of the first excitation electrode 214a in the Z'-axis direction. The first low acoustic velocity region 218A is provided in a region extending in the X-axis direction adjacent to the high acoustic velocity region 217 on the Z'-axis negative side. The second low acoustic velocity region 218B is provided in a region extending in the X-axis direction adjacent to the high acoustic velocity region 217 on the Z'-axis positive side. The high acoustic velocity region 217, the first low acoustic velocity region 218A, and the second low acoustic velocity region 218B are provided in a strip shape from the end of the first excitation electrode 214a on the X-axis negative side to the end of the first excitation electrode 214a on the X-axis positive side in a plan view.

[0119] <Third embodiment> Next, the configuration of a quartz crystal vibrating element 310 according to the third embodiment will be described with reference to Fig. 16. Fig. 16 is a plan view of the quartz crystal vibrating element according to the third embodiment.

[0120] As shown in FIG. 16, the quartz crystal vibrating element 310 has a high acoustic velocity region 317, a third low acoustic velocity region 318C, and a fourth low acoustic velocity region 318D. In a plan view, the high acoustic velocity region 317 is provided in a region extending in the Z'-axis direction at the center of the first excitation electrode 314a in the X-axis direction. The third low acoustic velocity region 318C is provided in a region extending in the Z'-axis direction adjacent to the high acoustic velocity region 317 on the positive X-axis side. The fourth low acoustic velocity region 318D is provided in a region extending in the Z'-axis direction adjacent to the high acoustic velocity region 317 on the negative X-axis side. The high acoustic velocity region 317, the third low acoustic velocity region 318C, and the fourth low acoustic velocity region 318D are provided in a strip shape from the end of the first excitation electrode 314a on the negative Z'-axis side to the end of the first excitation electrode 314a on the positive Z'-axis side in a plan view.

[0121] <Fourth embodiment> Next, a configuration of a quartz crystal vibrating element 410 according to a fourth embodiment will be described with reference to Fig. 17 and Fig. 18. Fig. 17 is a plan view of the quartz crystal vibrating element according to the fourth embodiment. Fig. 18 is a cross-sectional view of the quartz crystal vibrating element according to the fourth embodiment.

[0122] As shown in FIG. 17, the crystal oscillator 410 has a high sound velocity region 417, a first low sound velocity region 418A, a second low sound velocity region 418B, a third low sound velocity region 418C, and a fourth low sound velocity region 418D. The thickness of the first excitation electrode 414a in the high sound velocity region 417 and the low sound velocity regions 418 is Te1. In the high sound velocity region 417, a plurality of holes H are formed in the first excitation electrode 414a. The hole H is a through hole that penetrates the first excitation electrode 414a in the Y' axis direction. However, the hole is not limited to a through hole, and the hole may be a bottomed groove shape that opens in the Y' axis direction.

[0123] Let the dimension of the hole H in the Z' axis direction be Hz, and the dimension of the hole H in the X axis direction be Hx. The planar shape of the hole H is a square shape having a side extending along the Z' axis direction and a side extending along the X axis direction. That is, Hz = Hx.

[0124] Note that the planar shape of the hole H is not limited to a square shape having sides extending in the X axis direction and the Z' axis direction. For example, the planar shape of the hole H may be a square shape having sides extending in a direction intersecting the X axis direction and the Z' axis direction, or may be a rectangular shape with Hz < Hx or Hx < Hz. As shown in FIG. 32, the planar shape of the hole H may be a circular shape. As shown in FIG. 33, the planar shape of the hole H may be an elliptical shape. As shown in FIG. 34, the planar shape of the hole H may be a shape in which the four corners of the square shape are arc-shaped. Thus, the planar shape of the hole H may be a polygonal shape, a circular shape, an elliptical shape, or a combination thereof.

[0125] As shown in FIG. 17, a plurality of holes H are arranged in a matrix in the X-axis direction and the X'-axis direction. Let the pitch of the plurality of holes H in the Z'-axis direction, that is, the distance between the ends on the negative Z'-axis side of two adjacent holes H in the Z'-axis direction, be PHz. Let the pitch of the holes H in the X-axis direction, that is, the distance between the ends on the negative X-axis side of two adjacent holes H in the X-axis direction, be PHx. The plurality of holes H are arranged at equal intervals in each of the Z'-axis direction and the X-axis direction. That is, PHz = PHx.

[0126] Note that the pitch of the plurality of holes H is not limited to the above, and PHz < PHx or PHx < PHz may be satisfied. Also, the arrangement of the plurality of holes H is not limited to the above. The plurality of holes H may be arranged in a direction intersecting the Z'-axis direction and the X-axis direction. As shown in FIGS. 31 to 34, the plurality of holes H may be arranged in a staggered pattern. As shown in FIG. 35, the plurality of holes H may be arranged randomly.

[0127] Next, with reference to FIGS. 19 and 20, the simulation results of the examples based on the fourth embodiment will be described. FIG. 19 is a diagram showing the simulation results based on the fourth embodiment. FIG. 20 is a diagram comparing the simulation results based on the first embodiment and the fourth embodiment.

[0128] The configurations of the examples and the comparative examples in FIG. 19 are as follows. (Example) Tp = 1.52 μm Te1 = Te2 = 0.08 μm Px = Pz = 140 μm Ex = 100 μm Ez = 80 μm Wx = 39.5 μm Wz = 29.5 μm PHx = PHz = 3 μm Hx = Hz = 2 μm Number of H: 8 × 8 = 64 (Comparative Example) Tp = 1.52 μm Te1 = Te2 = 0.08 μm Px = Pz = 140 μm Ex=100μm Ez=80μm Wx=0μm Wz=0μm

[0129] As shown in the graph of frequency distribution in FIG. 19, the main mode frequency in the example is about 985 MHz, and the main mode frequency in the comparative example is 984 MHz. In the example based on the first embodiment, the frequency is lower than that in the comparative example, whereas in the example based on the fourth embodiment, the frequency is higher than that in the comparative example. This is because, in the first embodiment, mass is added to the low sound velocity region to form a sound velocity difference between the low sound velocity region and the high sound velocity region, whereas in the fourth example, the mass of the high sound velocity region is reduced to form a sound velocity difference between the low sound velocity region and the high sound velocity region. Therefore, in the case of increasing the frequency, the quartz crystal vibration element 410 according to the fourth embodiment is advantageous.

[0130] 19, in the comparative example, k_S0=6.93%, k_S1Z=2.26%, and k_S1Z=2.28%. In contrast, in the example, k_S0=7.42%, k_S1Z=0.05%, and k_S1X=1.17%. Therefore, in the example, the electromechanical coupling coefficient k_S0 of the main mode is improved, and the electromechanical coupling coefficients k_S1Z and k_S1X of the inharmonic modes are reduced.

[0131] The configurations of the example based on the first embodiment and the example based on the fourth embodiment in Fig. 20 are as follows: The horizontal axis Ter of the graph in Fig. 20 indicates the ratio of the average thickness of the excitation electrode in the high sound velocity region to the thickness of the excitation electrode in the low sound velocity region. (Example based on the fourth embodiment) Tp=1.52μm Te1 = Te2 = 0.08 μm Px = Pz = 140 μm Ex=100μm Ez=80μm Wx=39.5μm Wz=29.5μm PHx = PHz = 3μm Hx=Hz:variable Number of Hs: 8 x 8 = 64 (Example Based on the First Embodiment) Tp=1.52μm Te3(=Te1+Tf)=Te2=0.08μm Te1: Variables Px = Pz = 140 μm Ex=100μm Ez=80μm Wx=40μm Wz=30μm

[0132] In an example based on the fourth embodiment, Ter is expressed by the following formula: Ter = (Te1h + Te2) / (Te1 + Te2) Te1h is the average thickness of the first excitation electrode in the high sound velocity region and is expressed by the following formula. Te1h = Te1 × (1-Har) Har is the aperture ratio of the plurality of holes H and is expressed by the following formula: Har = (Hx / PHx) × (Hz / PHz)

[0133] In an example based on the first embodiment, Ter is expressed by the following formula: Ter = (Te1 + Te2) / (Te3 + Te2)

[0134] 20, the trends of k_S0, k_S1Z, and k_S1X versus Ter in the examples based on the fourth embodiment are substantially the same as the trends of k_S0, k_S1Z, and k_S1X versus Ter in the examples based on the first embodiment. That is, in the fourth embodiment, it is considered that the electromechanical coupling coefficient is improved by the same mechanism as in the first embodiment.

[0135] Next, while referring to FIG. 21, the influence of the hole H on the function as the excitation electrode will be described. FIG. 21 is a graph showing the influence of the planar dimensions of the hole. The horizontal axis of the graph in FIG. 21 indicates the ratio Hr / Tp of the length Hx = Hz = Hr of one side of the hole H having a square planar shape to the thickness Tp of the crystal piece 11. The vertical axis of the graph in FIG. 21 indicates the capacitance normalized by the capacitance in the state where the hole H is not formed.

[0136] If the length Hr of the hole H is equal to or less than twice the thickness Tp of the crystal piece 11, that is, if the relationship 0 < Hr / Tp ≤ 2.0 holds, the capacitance reduction rate can be suppressed to 1% or less, so that it can function sufficiently as the excitation electrode. Desirably, the length Hr of the hole H satisfies the relationship 0 < Hr / Tp ≤ 1.5 with respect to the thickness Tp of the crystal piece 11, and more desirably, the length Hr of the hole H satisfies the relationship 0 < Hr / Tp ≤ 1.0 with respect to the thickness Tp of the crystal piece 11. If 0 < Hr / Tp ≤ 1.5, the capacitance reduction rate can be suppressed to 0.5% or less, and if 0 < Hr / Tp ≤ 1.0, the capacitance reduction rate can be suppressed to 0.1% or less. In addition, in order to form the hole H with sufficient processing accuracy, it is desirable that the length Hr of the hole H is 0.1 times or more the thickness Tp of the crystal piece 11, that is, 0.1 ≤ Hr / Tp, and more desirably, the length Hr of the hole H is 0.5 times or more the thickness Tp of the crystal piece 11, that is, 0.5 ≤ Hr / Tp.

[0137] In addition, as shown in FIGS. 32 to 35, when the planar shape of the hole H is other than a square, the length Hr of the hole H is defined as the length of one side when the planar shape of the hole H is converted into a square while keeping the area constant. Even in such a case, if the relationship 0 < Hr / Tp ≤ 2.0 holds as in the case where the planar shape of the hole H is a square, the capacitance reduction rate can be suppressed to 1% or less, so that it can function sufficiently as the excitation electrode. Also, as in the case where the planar shape of the hole H is a square, if 0 < Hr / Tp ≤ 1.5, the capacitance reduction rate can be suppressed to 0.5% or less, and if 0 < Hr / Tp ≤ 1.0, the capacitance reduction rate can be suppressed to 0.1% or less.

[0138] Next, the influence of the pitches PHz, PHx of the multiple holes H will be described with reference to Fig. 22 and Fig. 23. Fig. 22 and Fig. 23 are graphs showing the influence of the planar dimensions and pitch of the holes. The horizontal axis of the graph in Fig. 22 is the above-mentioned Har, and the horizontal axis of the graph in Fig. 23 is the above-mentioned Ter. The vertical axis of Fig. 22 and Fig. 23 is k_S0 calculated under the following conditions. Tp=1.00μm Te1 = Te2 = 0.05 μm Px = Pz = 100 μm Ex=75μm Ez=70μm Wx=30μm Wz=20μm PHx=PHz:variable Hx=Hz:variable

[0139] As shown in FIG. 22, k_S0 shows the same tendency with respect to Har in any of the cases where PHz=PHx=3 μm, 2 μm, and 1 μm. Also, as shown in FIG. 23, k_S0 shows the same tendency with respect to Ter in any of the cases where PHz=PHx=3 μm, 2 μm, and 1 μm. That is, the main mode electromechanical coupling coefficient k_S0 is determined by Har and Ter, not by the pitches PHz and PHx of the multiple holes H. According to the graph in FIG. 22, k_S0 is maximum when the relationship Har=0.1±0.05 is satisfied. According to the graph in FIG. 23, k_S0 is maximum when the relationship Ter=0.93±0.03 is satisfied.

[0140] According to this embodiment, the high-velocity region 417 and the low-velocity region 418 can be formed by the single-layer first excitation electrode 414a. After providing the first metal film with a uniform thickness in the high-velocity region and the low-velocity region, in the case of providing the second metal film to form the low-velocity region or providing the mass addition film of the insulator to form the low-velocity region, due to the manufacturing variations caused by the displacement of the second metal film or the mass addition film, a low-velocity region with a desired width may not be formed. On the other hand, according to this embodiment, even if the displacement of the plurality of hole portions H occurs, only the position of the high-velocity region 417 changes, and a low-velocity region 418 with a desired width can be formed.

[0141] <Fifth Embodiment> Next, with reference to FIG. 24, the configuration of the crystal oscillator 510 according to the fifth embodiment will be described. FIG. 24 is a cross-sectional view of the crystal oscillator according to the fifth embodiment.

[0142] The thickness of the first excitation electrode 514a in the high-velocity region 517 and the low-velocity region 518 is Te1. In the high-velocity region 717, a plurality of hole portions H are formed in the first excitation electrode 514a. In the low-velocity region 718, a plurality of sub-hole portions h are formed in the first excitation electrode 514a. The sub-hole portion h is a through hole that penetrates the first excitation electrode 514a in the Y' axis direction. However, the sub-hole portion h is not limited to a through hole and may be a bottomed groove shape that opens in the Y' axis direction.

[0143] Let the dimension of the sub-hole portion h in the Z' axis direction be hz, and the dimension of the sub-hole portion h in the X axis direction be hx. The planar shape of the sub-hole portion h is a square shape having a side extending along the Z' axis direction and a side extending along the X axis direction. That is, hz = hx. However, the planar shape of the sub-hole portion h is not limited to a square shape, and may be a rectangular shape with hz < hx or a rectangular shape with hx < hz. The planar shape of the sub-hole portion h may be a polygonal shape, a circular shape, an elliptical shape, or a combination thereof.

[0144] Let the pitch of the plurality of sub-aperture portions h in the Z'-axis direction, that is, the distance between the ends on the negative Z'-axis side of two adjacent sub-aperture portions h in the Z'-axis direction, be Phz. Let the pitch of the sub-aperture portions h in the X-axis direction, that is, the distance between the ends on the negative X-axis side of two opposing sub-aperture portions h in the X-axis direction, be Phx. The plurality of sub-aperture portions h are arranged at equal intervals in each of the Z'-axis direction and the X-axis direction. That is, Phz = Phx. However, the pitch of the plurality of sub-aperture portions h is not limited to the above, and Phz < Phx or Phx < Phz may be possible. Also, the direction in which the plurality of sub-aperture portions h are arranged is not limited to the Z'-axis direction and the X-axis direction, and they may be arranged in a direction intersecting the Z'-axis direction and the X-axis direction. The plurality of sub-aperture portions h may be arranged in a staggered pattern.

[0145] In plan view, the area hz × hx of the sub-aperture portion h is smaller than the area Hz × Hx of the aperture portion H. The pitch Phz of the plurality of sub-aperture portions h is substantially equal to the pitch PHz of the plurality of aperture portions H (Phz ≒ PHz). Also, the pitch Phx of the plurality of sub-aperture portions h is substantially equal to the pitch PHx of the plurality of aperture portions H (Phx ≒ PHx).

[0146] Next, while referring to FIG. 25, the simulation results of the example based on the fifth embodiment will be described. FIG. 25 is a diagram showing a comparison of the simulation results based on the fourth embodiment and the fifth embodiment.

[0147] The configuration of the example based on the fifth embodiment is as follows. Tp = 1.52 μm Te1 = Te2 = 0.08 μm Px = Pz = 140 μm Ex = 100 μm Ez = 80 μm Wx = 39.5 μm Wz = 29.5 μm PHx = PHz = 3 μm Hx = Hz = 2 μm Number of H: 8 × 8 = 64 Phz = Phx = 3 μm hx = hz = 0.5 μm The configuration of the embodiment based on the fourth embodiment is the same as that of the embodiment shown in FIG. 19, and is the same as the configuration of the embodiment based on the fifth embodiment except that a plurality of sub-aperture portions h are not formed.

[0148] In the embodiment based on the fifth embodiment, k_S0 = 7.41%, k_S1Z = 0.17%, and k_S1Z = 1.08%. Also in the embodiment based on the fifth embodiment, similar to the embodiment based on the fourth embodiment, the electromechanical coupling coefficient k_S0 in the main mode is improved, and the electromechanical coupling coefficients k_S1Z and k_S1X in the inharmonic modes are decreased.

[0149] According to the present embodiment, by adjusting the ratio between the aperture ratio Har of the plurality of aperture portions H and the aperture ratio har of the plurality of sub-aperture portions h, the ratio between the sound speed in the high sound speed region 517 and the sound speed in the low sound speed region 518 can be appropriately adjusted.

[0150] Note that if the relationship har < Har holds for the aperture ratio har of the sub-aperture portion h and the aperture ratio Har of the aperture portion H, the dimensions hz, hx and the pitches Phx, Phz of the sub-aperture portion h are not limited to the above. The aperture ratio har is represented by the following formula. har = (hx / Phx) × (hz / Phz)

[0151] For example, if the relationship har < Har holds, the pitch Phz of the sub-aperture portion h may be smaller than the pitch PHz of the aperture portion H (Phz < PHz), and the pitch Phx of the sub-aperture portion h may be smaller than the pitch PHx of the aperture portion H (Phx < PHx). At this time, in order for the relationship har < Har to hold, the area hz × hx of the sub-aperture portion h is smaller than the area Hz × Hx of the aperture portion H (hz × hx < Hz × Hx).

[0152] For example, if the relationship har < Har holds, the area hz × hx of the auxiliary hole portion h may be equal to or larger than the area Hz × Hx of the hole portion H (Hz × Hx ≤ hz × hx). At this time, in order for the relationship har < Har to hold, at least one of the relationship that the pitch Phz of the auxiliary hole portion h is larger than the pitch PHz of the hole portion H (PHz < Phz) and the relationship that the pitch Phx of the auxiliary hole portion h is larger than the pitch PHx of the hole portion H (PHx < Phx) holds.

[0153] However, even when the area hz × hx of the auxiliary hole portion h is larger than the area Hz × Hx of the hole portion H (Hz × Hx < hz × hx), the length hr of one side of the auxiliary hole portion h = hz = hx satisfies the relationship 0 < hr / Tp ≤ 2.0, similar to the length Hr of one side of the hole portion H = Hz = Hx. According to this, since the reduction rate of the capacitance can be suppressed to 1% or less, the low sound velocity region 518 can function as the excitation electrode. If 0 < hr / Tp ≤ 1.5, the reduction rate of the capacitance can be suppressed to 0.5% or less, and if 0 < Hr / Tp ≤ 1.0, the reduction rate of the capacitance can be suppressed to 0.1% or less.

[0154] <Sixth Embodiment> Next, with reference to FIG. 26, the configuration of the crystal oscillator 610 according to the sixth embodiment will be described. FIG. 26 is a cross-sectional view of the crystal oscillator according to the sixth embodiment.

[0155] The first excitation electrode 614a includes a high sound velocity electrode E17 provided in the high sound velocity region 617 and a low sound velocity electrode E18 provided in the low sound velocity region 618. The high sound velocity electrode E17 and the low sound velocity electrode E18 are continuous in the Z' axis direction and the X axis direction. The thickness Te17 of the high sound velocity electrode E17 is substantially equal to the thickness Te18 of the low sound velocity electrode E18 (Te17 ≒ Te18). The material of the high sound velocity electrode E17 is different from the material of the low sound velocity electrode E18. The specific gravity of the low sound velocity electrode E18 is larger than the specific gravity of the high sound velocity electrode E17.

[0156] Next, a simulation result of an example based on the sixth embodiment will be described with reference to Fig. 27. Fig. 27 is a diagram showing a simulation result based on the sixth embodiment.

[0157] The configuration of an example based on the sixth embodiment is as follows. Tp=1.52μm Te17 = Te18 = Te2 = 0.08 μm Px = Pz = 140 μm Ex=100μm Ez=80μm Wx=40μm Wz=30μm E17: Al E18:Ti

[0158] As shown in the frequency distribution graph in Fig. 27, the main mode frequency is about 937.5 MHz. Also, as shown in Fig. 27, in an example based on the sixth embodiment, k_S0=7.45%, k_S1Z=0.11%, and k_S1X=1.28%.

[0159] Seventh embodiment Next, the configuration of a quartz crystal vibrating element 710 according to the seventh embodiment will be described with reference to Fig. 28. Fig. 28 is a cross-sectional view of the quartz crystal vibrating element according to the seventh embodiment.

[0160] A thickness Te1 of the first excitation electrode 714a in the high sound velocity region 717 is smaller than a thickness Te3 of the first excitation electrode 714a in the low sound velocity region 718. That is, the relationship Te3=Te1+Tf holds. In the high sound velocity region 717, a plurality of holes H are formed in the first excitation electrode 714a.

[0161] According to this embodiment, the thickness Te3 of the first excitation electrode 714a in the low sound velocity region 718 is thicker than the thickness Te1 of the first excitation electrode 714a in the high sound velocity region 717 by Tf, so that the sound velocity in the low sound velocity region 718 is reduced. Furthermore, since a plurality of holes H are formed in the first excitation electrode 714a in the high sound velocity region 717, the sound velocity in the high sound velocity region 717 increases. That is, the difference in sound velocity between the high sound velocity region 717 and the low sound velocity region 718 is further increased.

[0162] Eighth embodiment Next, the configuration of a quartz crystal vibrating element 810 according to the eighth embodiment will be described with reference to Fig. 29. Fig. 29 is a cross-sectional view of the quartz crystal vibrating element according to the eighth embodiment.

[0163] The thickness Tp2 of the crystal blank 811 in the low acoustic velocity region 818 is greater than the thickness Tp1 of the crystal blank 811 in the high acoustic velocity region 817. That is, in the region overlapping with the first excitation electrode 814a in a plan view, the crystal blank 811 is formed in an inverted mesa shape. The acoustic velocity of the low acoustic velocity region 818 is smaller than the acoustic velocity of the high acoustic velocity region 817 by the difference Tp2-Tp1 in the thickness of the crystal blank 811.

[0164] <Ninth embodiment> Next, the configuration of a quartz crystal vibrating element 910 according to the ninth embodiment will be described with reference to Fig. 30. Fig. 30 is a cross-sectional view of the quartz crystal vibrating element according to the ninth embodiment.

[0165] A mass-adding film AD is provided on the first excitation electrode 914a in the low sound velocity region 918. In a plan view, the mass-adding film AD is provided outside the high sound velocity region 917 and in a region overlapping the low sound velocity region 918. The mass-adding film AD adds mass to the low sound velocity region 918, making the mass per unit area in a plan view of the low sound velocity region 918 larger than the mass per unit area in a plan view of the high sound velocity region 917. As a result, the mass-adding film AD reduces the sound velocity in the low sound velocity region 918. The material of the mass-adding film AD is, for example, an insulator. From the viewpoint of efficiently reducing the sound velocity in the low sound velocity region 918, it is desirable that the material of the mass-adding film be a material with a large specific gravity. For example, it is desirable that the specific gravity of the mass-adding film is larger than the specific gravity of the first excitation electrode 914a.

[0166] Although the mass-adding film AD is provided on the first excitation electrode 914a, the position of the mass-adding film is not limited to this as long as it is provided in an area overlapping the first excitation electrode or the second excitation electrode in the low sound velocity region. The mass-adding film may be provided in at least one of the following locations: the side of the first excitation electrode opposite the crystal blank, the side of the first excitation electrode opposite the crystal blank, the side of the second excitation electrode opposite the crystal blank, and the side of the second excitation electrode opposite the crystal blank. The material of the mass-adding film AD is an insulator, but is not limited to this, and the material of the mass-adding film may be, for example, a metal different from the first excitation electrode, or a semiconductor.

[0167] Some or all of the embodiments of the present invention will be described below. Note that the present invention is not limited to the following descriptions.

[0168] <1> A piezoelectric vibration element including a piezoelectric piece and an excitation electrode overlapping in a thickness direction, A high sound speed region and a low sound speed region in which the sound speed is slower than that of the high sound speed region, The high sound velocity region is provided in a region overlapping a center portion of the excitation electrode in a plan view in the thickness direction, The low acoustic velocity region includes a first low acoustic velocity region and a second low acoustic velocity region provided in a region overlapping an end of the excitation electrode surrounding the high acoustic velocity region in a plan view in the thickness direction, and in a first direction intersecting the thickness direction, the first low acoustic velocity region is adjacent to the high acoustic velocity region, and the second low acoustic velocity region is adjacent to the high acoustic velocity region on the opposite side to the first low acoustic velocity region, When the length of the excitation electrode in the first direction is Ea, the length of the first low sound velocity region in the first direction is Wa1, and the length of the second low sound velocity region in the first direction is Wa2, 0.20≦Wa1 / Ea and, 0.20≦Wa2 / Ea and, 0.5≦(Wa1+Wa2) / Ea≦0.96 The relationship is established as follows: Piezoelectric vibration element.

[0169] <2> 0.25≦Wa1 / Ea≦0.48 and, 0.25≦Wa2 / Ea≦0.48 The relationship is established as follows: <1> The piezoelectric vibration element described in

[0170] <3> The low acoustic velocity region includes a third low acoustic velocity region and a fourth low acoustic velocity region provided in a region overlapping an end of the excitation electrode surrounding the high acoustic velocity region in a plan view in the thickness direction, and in a second direction intersecting the thickness direction and the first direction, the third low acoustic velocity region is adjacent to the high acoustic velocity region, and the fourth low acoustic velocity region is adjacent to the high acoustic velocity region on the opposite side to the third low acoustic velocity region, When the length of the excitation electrode in the second direction is Eb, the length of the third low sound velocity region in the second direction is Wb1, and the length of the fourth low sound velocity region in the second direction is Wb2, 0.20≦Wb1 / Eb and, 0.20≦Wb2 / Eb and, 0.5≦(Wb1+Wb2) / Eb≦0.96 The relationship is established as follows: <1> or <2> The piezoelectric vibration element described in

[0171] <4> 0.25≦Wb1 / Eb≦0.48 and, 0.25≦Wb2 / Eb≦0.48 The relationship is established as follows: <3> The piezoelectric vibration element described in

[0172] <5> A piezoelectric vibration element including a piezoelectric piece and an excitation electrode, A high sound speed region and a low sound speed region in which the sound speed is slower than that of the high sound speed region, The high sound velocity region is provided in a region overlapping a center portion of the excitation electrode in a plan view in the thickness direction, The low sound speed region is In a plan view in the thickness direction, the first low acoustic velocity region, the second low acoustic velocity region, the third low acoustic velocity region, and the fourth low acoustic velocity region are provided in a region overlapping an end of the excitation electrode surrounding the high acoustic velocity region, In a first direction intersecting the thickness direction, the first low sound velocity region is adjacent to the high sound velocity region, and the second low sound velocity region is adjacent to the high sound velocity region on an opposite side to the first low sound velocity region; In a second direction intersecting the thickness direction and the first direction, the third low sound velocity region is adjacent to the high sound velocity region, and the fourth low sound velocity region is adjacent to the high sound velocity region on the opposite side to the third low sound velocity region; When the length of the excitation electrode in the first direction is Ea, the length of the excitation electrode in the second direction is Eb, the length of each of the first low sound velocity region and the second low sound velocity region in the first direction is Wa, and the length of each of the third low sound velocity region and the fourth low sound velocity region in the second direction is Wb, 0.8<5.0×(Wa / Ea) 2 +4.0×(Wb / Eb) 2 and, Wa / Ea≦0.48 and, Wb / Eb≦0.48 The relationship is established as follows: Piezoelectric vibration element.

[0173] <6> In plan view in the thickness direction, One end of the first low sound speed region in the second direction overlaps with one end of the third low sound speed region in the first direction, the other end portion of the first low sound speed region opposite to the one end portion in the second direction overlaps with one end portion of the fourth low sound speed region in the first direction, One end of the second low sound speed region in the second direction overlaps with another end of the third low sound speed region opposite to the one end of the third low sound speed region in the first direction, The other end portion of the second low sound speed region opposite to the one end portion in the second direction overlaps with the other end portion of the fourth low sound speed region opposite to the one end portion in the first direction. <3> from <5> 13. The piezoelectric vibration element according to claim 12,

[0174] <7> the first low sound velocity region and the second low sound velocity region extend along a second direction intersecting the first direction in a plan view; When the length of the excitation electrode in the second direction is Eb, the length of the first low sound velocity region in the second direction is Lb1, and the length of the first low sound velocity region in the second direction is Lb2, 0.8≦Lb1 / Eb≦1.0 and, 0.8≦Lb2 / Eb≦1.0 The relationship is established as follows: <1> from <6> 13. The piezoelectric vibration element according to claim 12,

[0175] <8> The third low sound velocity region and the fourth low sound velocity region extend along a first direction in a plan view, and when the length of the third low sound velocity region in the first direction is La1 and the length of the fourth low sound velocity region in the first direction is La2, 0.8≦La1 / Ea≦1.0 and, 0.8≦La2 / Ea≦1.0 The relationship is established as follows: <3> from <6> 13. The piezoelectric vibration element according to claim 12,

[0176] <9> When the length of the excitation electrode in the first direction is Ea, the length of the excitation electrode in the second direction is Eb, the length of each of the first low sound velocity region and the second low sound velocity region in the first direction is Wa, and the length of each of the third low sound velocity region and the fourth low sound velocity region in the second direction is Wb, Wa / Ea=0.35±0.05 and, Wb / Eb=0.35±0.05 The relationship is established as follows: <3> from <6> 13. The piezoelectric vibration element according to claim 12,

[0177] <10> When the length of the excitation electrode in the first direction is Ea, the length of the excitation electrode in the second direction is Eb, the length of each of the first low sound velocity region and the second low sound velocity region in the first direction is Wa, and the length of each of the third low sound velocity region and the fourth low sound velocity region in the second direction is Wb, Wa / Ea=0.40±0.05 and, Wb / Eb=0.40±0.05 The relationship is established as follows: <3> from <6> 13. The piezoelectric vibration element according to claim 12,

[0178] <11> The thickness of the excitation electrode in the low sound velocity region is greater than the thickness of the excitation electrode in the high sound velocity region. <1> from <10> 13. The piezoelectric vibration element according to claim 12,

[0179] <12> Further comprising a mass-adding film overlapping the excitation electrode in the low sound velocity region; <1> from <11> 13. The piezoelectric vibration element according to claim 12,

[0180] <13> The material of the mass-addition membrane is a metal different from that of the excitation electrode. <12> The piezoelectric vibration element described in

[0181] <14> The material of the mass-added film is an insulator different from the piezoelectric element. The piezoelectric vibration element described in <12>.

[0182] <15> In the high sound velocity region, a plurality of holes are formed in the excitation electrode. The piezoelectric vibration element according to any one of <1> to <14>.

[0183] <16> The plurality of holes are through holes penetrating the excitation electrode in the thickness direction. Let the thickness of the piezoelectric element be Tp. In plan view, when the shape of the plurality of holes is square, let the length of one side be Hr, and when the shape of the plurality of holes is other than square, let the length of one side be Hr when converted to a square with a constant area. The relationship 0 < Hr / Tp ≦ 2.0 holds. The piezoelectric vibration element according to claim 15. The piezoelectric vibration element described in <15>.

[0184] <17> In the low sound velocity region, a plurality of sub-holes are formed in the excitation electrode. The aperture ratio of the plurality of sub-holes is smaller than the aperture ratio of the plurality of holes. Let the thickness of the piezoelectric element be Tp. In plan view, when the shape of the plurality of holes is square, let the length of one side be hr, and when the shape of the plurality of holes is other than square, let the length of one side be hr when converted to a square with a constant area. The relationship 0 < hr / Tp ≦ 2.0 holds. The piezoelectric vibration element according to <15> or <16>.

[0185] <18> The material of the excitation electrode in the low sound velocity region is different from the material of the excitation electrode in the high sound velocity region, and the specific gravity of the excitation electrode in the low sound velocity region is larger than the specific gravity of the excitation electrode in the high sound velocity region. The piezoelectric vibration element according to any one of <1> to <17>.

[0186] <19> The thickness of the piezoelectric piece in the low sound velocity region is greater than the thickness of the piezoelectric piece in the high sound velocity region. <1> from <18> 13. The piezoelectric vibration element according to claim 12,

[0187] <20> The main vibration mode is thickness-shear vibration. <1> from <19> 13. The piezoelectric vibration element according to claim 12,

[0188] <21> The piezoelectric strip is a quartz crystal strip. <1> from <20> 13. The piezoelectric vibration element according to claim 12,

[0189] <22> The cut angle of the quartz crystal piece is AT cut, BT cut or ST cut. <21> The piezoelectric vibration element described in

[0190] In addition, the embodiment according to the present invention is not limited to a quartz crystal resonator, and can be applied to other piezoelectric resonators (Piezoelectric Resonator Units). Examples of piezoelectric pieces suitable for use in the piezoelectric resonator according to the present embodiment include piezoelectric ceramics such as lead zirconate titanate (PZT) and aluminum nitride, and piezoelectric single crystals such as lithium niobate and lithium tantalate, but are not limited thereto and can be appropriately selected.

[0191] The embodiments according to the present invention can be appropriately applied to any device that performs electromechanical energy conversion by utilizing the piezoelectric effect, such as a timing device, a sound generator, an oscillator, or a load sensor, without any particular limitation.

[0192] As described above, according to one aspect of the present invention, a piezoelectric vibration element capable of improving the electromechanical coupling coefficient can be provided.

[0193] The above-described embodiments are provided to facilitate understanding of the present invention, and are not intended to limit the present invention. The present invention may be modified / improved without departing from the spirit thereof, and equivalents are also included in the present invention. In other words, the embodiment and / or modification may be modified by a person skilled in the art as long as it has the characteristics of the present invention. For example, the elements and their arrangements, materials, conditions, shapes, sizes, etc. of the embodiment and / or modification are not limited to those shown as examples, and may be modified as appropriate. In addition, the embodiment and modification are illustrative, and it goes without saying that partial replacement or combination of the configurations shown in different embodiments and / or modifications is possible, and these are also included in the scope of the present invention as long as they include the characteristics of the present invention. [Explanation of symbols]

[0194] 100...Crystal oscillator 1...Crystal resonator 10...Crystal vibration element 11...Crystal piece 11A…Top surface 11B…Bottom surface 14a...first excitation electrode 14b…Second excitation electrode 17…High sound velocity region 18…Low sound velocity region 18A…1st low sound velocity region 18B…Second low sound velocity region 18C…3rd low sound velocity region 18D…4th low sound velocity region

Claims

1. A piezoelectric vibration element including a piezoelectric piece and an excitation electrode overlapping in a thickness direction, A high sound speed region and a low sound speed region in which the sound speed is slower than that of the high sound speed region, The high acoustic velocity region is provided in a region overlapping a central portion of the excitation electrode in a plan view in the thickness direction, In the high sound velocity region, a plurality of holes are formed in the excitation electrode, the plurality of holes are through holes penetrating the excitation electrode in the thickness direction, The low acoustic velocity region includes a first low acoustic velocity region and a second low acoustic velocity region provided in a region overlapping an end of the excitation electrode surrounding the high acoustic velocity region in a plan view in the thickness direction, In a first direction intersecting the thickness direction, the first low sound speed region is adjacent to the high sound speed region, and the second low sound speed region is adjacent to the high sound speed region on the opposite side to the first low sound speed region, When the length of the excitation electrode in the first direction is Ea, the length of the first low sound velocity region in the first direction is Wa1, and the length of the second low sound velocity region in the first direction is Wa2, 0.25<Wa1 / Ea≦0.48 and, 0.25<Wa2 / Ea≦0.48 and, 0.5≦(Wa1+Wa2) / Ea≦0.96 The relationship is established, The thickness of the piezoelectric piece is Tp, In a plan view, when the shape of the plurality of holes is a square, the length of one side of the square is defined as Hr. When the shape of the plurality of holes is other than a square, the length of one side of the square shape when the shape is converted to a square shape while keeping the area constant is defined as Hr. The relationship 0<Hr / Tp≦2.0 is satisfied. Piezoelectric vibration element.

2. A piezoelectric vibration element comprising a piezoelectric piece and an excitation electrode overlapping in a thickness direction, A high sound speed region and a low sound speed region in which the sound speed is slower than that of the high sound speed region, The high acoustic velocity region is provided in a region overlapping a central portion of the excitation electrode in a plan view in the thickness direction, In the high sound velocity region, a plurality of holes are formed in the excitation electrode, The low acoustic velocity region includes a first low acoustic velocity region and a second low acoustic velocity region provided in a region overlapping an end of the excitation electrode surrounding the high acoustic velocity region in a plan view in the thickness direction, In a first direction intersecting the thickness direction, the first low sound speed region is adjacent to the high sound speed region, and the second low sound speed region is adjacent to the high sound speed region on the opposite side to the first low sound speed region, In the low sound velocity region, a plurality of sub-holes are formed in the excitation electrode, an aperture ratio of the plurality of sub-holes is smaller than an aperture ratio of the plurality of holes; When the length of the excitation electrode in the first direction is Ea, the length of the first low sound velocity region in the first direction is Wa1, and the length of the second low sound velocity region in the first direction is Wa2, 0.25<Wa1 / Ea≦0.48 and, 0.25<Wa2 / Ea≦0.48 and, 0.5≦(Wa1+Wa2) / Ea≦0.96 The relationship is established, The thickness of the piezoelectric piece is Tp, In a plan view, when the shape of the plurality of holes is a square, the length of one side of the square is defined as hr, and when the shape of the plurality of holes is other than a square, the length of one side of the square shape when the shape is converted to a square shape while keeping the area constant is defined as hr. The relationship 0<hr / Tp≦2.0 is satisfied. Piezoelectric vibration element.

3. The low acoustic velocity region includes a third low acoustic velocity region and a fourth low acoustic velocity region provided in a region overlapping an end of the excitation electrode surrounding the high acoustic velocity region in a plan view in the thickness direction, In a second direction intersecting the thickness direction and the first direction, the third low sound speed region is adjacent to the high sound speed region, and the fourth low sound speed region is adjacent to the high sound speed region on the opposite side to the third low sound speed region, When the length of the excitation electrode in the second direction is Eb, the length of the third low sound velocity region in the second direction is Wb1, and the length of the fourth low sound velocity region in the second direction is Wb2, 0.25<Wb1 / Eb≦0.48 and, 0.25<Wb2 / Eb≦0.48 and, 0.5≦(Wb1+Wb2) / Eb≦0.96 The relationship is established as follows: The piezoelectric vibration element according to claim 1 .

4. A piezoelectric vibration element including a piezoelectric piece and an excitation electrode overlapping in a thickness direction, A high sound speed region and a low sound speed region in which the sound speed is slower than that of the high sound speed region, The high acoustic velocity region is provided in a region overlapping a central portion of the excitation electrode in a plan view in the thickness direction, The low sound speed region is A first low acoustic velocity region, a second low acoustic velocity region, a third low acoustic velocity region, and a fourth low acoustic velocity region are provided in a region that overlaps an end of the excitation electrode surrounding the high acoustic velocity region when viewed in a plan view in the thickness direction, In a first direction intersecting the thickness direction, the first low sound velocity region is adjacent to the high sound velocity region, and the second low sound velocity region is adjacent to the high sound velocity region on an opposite side to the first low sound velocity region, In a second direction intersecting the thickness direction and the first direction, the third low sound speed region is adjacent to the high sound speed region, and the fourth low sound speed region is adjacent to the high sound speed region on the opposite side to the third low sound speed region, When the length of the excitation electrode in the first direction is Ea, the length of the excitation electrode in the second direction is Eb, the length of each of the first low sound velocity region and the second low sound velocity region in the first direction is Wa, and the length of each of the third low sound velocity region and the fourth low sound velocity region in the second direction is Wb, 0.8<5.0×(Wa / Ea) 2 +4.0×(Wb / Ea) 2 and, Wa / Ea≦0.48 and, Wb / Eb≦0.48 The relationship is established as follows: Piezoelectric vibration element.

5. In a plan view in the thickness direction, one end of the first low sound speed region in the second direction overlaps with one end of the third low sound speed region in the first direction, an end portion of the first low sound speed region opposite to the end portion in the second direction overlaps with an end portion of the fourth low sound speed region in the first direction; one end of the second low sound speed region in the second direction overlaps with another end of the third low sound speed region opposite to the one end of the third low sound speed region in the first direction, the other end portion of the second low sound speed region opposite to the one end portion in the second direction overlaps with the other end portion of the fourth low sound speed region opposite to the one end portion in the first direction; The piezoelectric vibration element according to claim 3 .

6. The first low sound velocity region and the second low sound velocity region extend along the thickness direction and a second direction intersecting the first direction, When the length of the excitation electrode in the second direction is Eb, the length of the first low sound velocity region in the second direction is Lb1, and the length of the first low sound velocity region in the second direction is Lb2, 0.8≦Lb1 / Eb≦1.0 and, 0.8≦Lb2 / Eb≦1.0 The relationship is established as follows: The piezoelectric vibration element according to claim 1 .

7. The third low sound velocity region and the fourth low sound velocity region extend along the first direction in a plan view, When the length of the third low sound speed region in the first direction is La1 and the length of the fourth low sound speed region in the first direction is La2, 0.8≦La1 / Ea≦1.0 and, 0.8≦La2 / Ea≦1.0 The relationship is established as follows: The piezoelectric vibration element according to claim 3 .

8. When the length of the excitation electrode in the first direction is Ea, the length of the excitation electrode in the second direction is Eb, the length of each of the first low sound velocity region and the second low sound velocity region in the first direction is Wa, and the length of each of the third low sound velocity region and the fourth low sound velocity region in the second direction is Wb, Wa / Ea=0.35±0.05 and, Wb / Eb=0.35±0.05 The relationship is established as follows: The piezoelectric vibration element according to claim 3 .

9. When the length of the excitation electrode in the first direction is Ea, the length of the excitation electrode in the second direction is Eb, the length of each of the first low sound velocity region and the second low sound velocity region in the first direction is Wa, and the length of each of the third low sound velocity region and the fourth low sound velocity region in the second direction is Wb, Wa / Ea=0.40±0.05 and, Wb / Eb=0.40±0.05 The relationship is established as follows: The piezoelectric vibration element according to claim 3 .

10. The thickness of the excitation electrode in the low sound velocity region is greater than the thickness of the excitation electrode in the high sound velocity region. The piezoelectric vibration element according to claim 1 .

11. Further comprising a mass addition film overlapping the excitation electrode in the low sound velocity region. The piezoelectric vibration element according to claim 1 .

12. The material of the mass addition film is a metal different from that of the excitation electrode. The piezoelectric vibration element according to claim 11.

13. The material of the mass-adding film is an insulator different from that of the piezoelectric piece. The piezoelectric vibration element according to claim 11.

14. A plurality of holes are formed in the excitation electrode in the high sound velocity region. The piezoelectric vibration element according to claim 4 .

15. the plurality of holes are through holes penetrating the excitation electrode in the thickness direction, The thickness of the piezoelectric piece is Tp, In a plan view, when the shape of the plurality of holes is a square, the length of one side of the square is defined as Hr. When the shape of the plurality of holes is other than a square, the length of one side of the square shape when the shape is converted to a square shape while keeping the area constant is defined as Hr. The relationship 0<Hr / Tp≦2.0 is satisfied. The piezoelectric vibration element according to claim 14.

16. In the low sound velocity region, a plurality of sub-holes are formed in the excitation electrode, an aperture ratio of the plurality of sub-holes is smaller than an aperture ratio of the plurality of holes; The thickness of the piezoelectric piece is Tp, In a plan view, when the shape of the plurality of holes is a square, the length of one side of the square is defined as hr, and when the shape of the plurality of holes is other than a square, the length of one side of the square shape when the shape is converted to a square shape while keeping the area constant is defined as hr. The relationship 0<hr / Tp≦2.0 is satisfied. The piezoelectric vibration element according to claim 14.

17. The material of the excitation electrode in the low sound velocity region is different from the material of the excitation electrode in the high sound velocity region, The specific gravity of the excitation electrode in the low sound velocity region is greater than the specific gravity of the excitation electrode in the high sound velocity region. The piezoelectric vibration element according to claim 1 .

18. The thickness of the piezoelectric piece in the low sound velocity region is greater than the thickness of the piezoelectric piece in the high sound velocity region. The piezoelectric vibration element according to claim 1 .

19. The main vibration mode is thickness-shear vibration. The piezoelectric vibration element according to claim 1 .

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