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

Piezoelectric vibration element

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

[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. A piezoelectric vibration element includes a piezoelectric plate having a pair of main surfaces and a pair of excitation electrodes provided on the pair of main surfaces of the piezoelectric plate.

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

[0004] International Publication No. 98 / 38736

[0005] However, in the prior art, it is desired 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 an object of the present invention is to provide a piezoelectric vibration element that can improve the electromechanical coupling coefficient.

[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, 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 central portion of the excitation electrode in a plan view in the thickness direction, and the low acoustic velocity region includes 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 that surrounds the high acoustic velocity region in a plan view in the thickness direction, In a first direction intersecting 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 central portion of the excitation electrode in a plan 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 regions that overlap end portions of the excitation electrode that surround the high acoustic velocity region in a plan view in the thickness direction, and in a first direction that intersects with the thickness direction, the first low acoustic velocity region is adjacent to the high acoustic velocity region. the second low acoustic velocity region is adjacent to the high acoustic velocity region on the side opposite to the first low acoustic velocity region, the third low acoustic velocity region is adjacent to the high acoustic velocity region in a second direction intersecting the thickness direction and the first direction, and the fourth low acoustic velocity region is adjacent to the high acoustic velocity region on the side opposite to the third low acoustic 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 acoustic velocity region and the second low acoustic velocity region in the first direction is Wa, and the length of each of the third low acoustic velocity region and the fourth low acoustic 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 established.

[0009] According to the present invention, it is possible to provide a piezoelectric vibration element that can improve the electromechanical coupling coefficient.

[0010] 1. A cross-sectional view of a crystal oscillator according to a first embodiment. An exploded perspective view of a crystal resonator according to the first embodiment. A cross-sectional view of a crystal resonator according to the first embodiment. A cross-sectional view of a crystal resonator element according to the first embodiment. A plan view of a crystal resonator element according to the first embodiment. A diagram showing simulation results based on the first embodiment. A diagram showing simulation results based on the first embodiment. A diagram showing simulation results based on the first embodiment. A diagram showing simulation results based on the first embodiment. A graph showing the influence of the planar dimensions of a low sound velocity region. A graph showing the influence of the planar dimensions of a low sound velocity region. A graph showing the influence of the planar dimensions of a low sound velocity region. A graph showing the influence of the thickness of a low sound velocity region. A graph showing the influence of the thickness of a high sound velocity region. A plan view of a crystal resonator element according to a second embodiment. A plan view of a crystal resonator element according to a third embodiment. A plan view of a crystal resonator element according to a fourth embodiment. A cross-sectional view of a crystal resonator element according to the fourth embodiment. A diagram comparing simulation results based on the first and fourth embodiments. A graph showing the influence of the planar dimensions of a hole. A graph showing the influence of the planar dimensions and pitch of the hole. A graph showing the influence of the planar dimensions and pitch of the hole. A cross-sectional view of a crystal resonator element according to a fifth embodiment. FIG. 10 is a diagram showing a comparison of simulation results based on the fourth embodiment and the fifth embodiment. FIG. 11 is a cross-sectional view of a quartz vibrating element according to the sixth embodiment. FIG. 12 is a diagram showing simulation results based on the sixth embodiment. FIG. 13 is a cross-sectional view of a quartz vibrating element according to the seventh embodiment. FIG. 14 is a cross-sectional view of a quartz vibrating element according to the eighth embodiment. FIG. 15 is a cross-sectional view of a quartz vibrating element according to the ninth embodiment. FIG. 16 is a plan view of a modified example of the high acoustic velocity region according to the fourth embodiment. FIG. 17 is a plan view of a modified example of the high acoustic velocity region according to the fourth embodiment. FIG. 18 is a plan view of a modified example of the high acoustic velocity region according to the fourth embodiment.

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

[0012] For the sake of clarity, each drawing may be accompanied by a Cartesian coordinate system consisting of an X-axis, a Y'-axis, and a Z'-axis to clarify the interrelationships between the drawings and to aid in understanding the positional relationships of each component. The X-axis, Y'-axis, and Z'-axis correspond to each other in each drawing. The X-axis, Y'-axis, and Z'-axis correspond to the crystalline 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 Z'-axis are 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 arrows on the X-axis, Y'-axis, and Z'-axis are referred to as "positive" or "+ (plus)," and the directions opposite the arrows are referred to as "negative" or "- (minus)." For convenience, the +Y'-axis direction will be described as the upward direction, and the -Y'-axis direction will be described as the downward direction, but the up-down orientation of the quartz resonator element 10, the quartz resonator 1, and the quartz oscillator 100 is not limited to this. The plane specified by the X-axis and Z'-axis is referred to as the Z'X plane, and the same applies to 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) equipped with a quartz crystal resonator unit will be used as an example of a piezoelectric oscillator. Furthermore, a crystal resonator unit equipped with a quartz crystal resonator will be used as an example of a piezoelectric resonator unit. Furthermore, a crystal resonator element equipped with a quartz crystal element will be used as an example of a piezoelectric resonator element. A quartz crystal element is a type of piezoelectric material (piezoelectric piece) that vibrates in response to an applied voltage. Note that the piezoelectric oscillator is not limited to a quartz crystal resonator, and may utilize other piezoelectric materials such as ceramic. Similarly, the piezoelectric vibrator is not limited to a quartz crystal vibrator, but may be one that uses other piezoelectric materials such as ceramics, etc. Similarly, the piezoelectric vibrating element is not limited to a quartz crystal vibrating element, but may be one that uses other piezoelectric materials such as ceramics, etc.

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

[0021] The lid 140 includes a bottomed opening that is open on one side (the bottom side in FIG. 1 ). In other words, the lid 140 includes a flat top wall, a side wall that extends from the outer edge of the top wall toward the mounting substrate 130, and a flange that extends outward from the tip of the side wall. The flange is bonded to one surface (the top surface in FIG. 1 ) of the mounting substrate 130. This allows the crystal unit 1 bonded to the mounting substrate 130 to be 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 substrate 130. More specifically, the wiring layer of the mounting substrate 130 and the electronic component 156 are joined by solder 153. In this way, the electronic component 156 is mounted on the mounting substrate 130.

[0023] The electronic component 156 is electrically connected to the crystal unit 1 through a wiring layer of the mounting substrate 130. The electronic component 156 includes, for example, a capacitor, an IC chip, etc. The electronic component 156 is, for example, part of an oscillation circuit that causes the crystal unit 1 to oscillate, or 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 Figures 2 and 3. Figure 2 is an exploded perspective view of the crystal resonator according to the first embodiment. Figure 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 the "first direction", the X-axis direction corresponds to an example of the "second direction", and the Y'-axis direction corresponds to an example of the "third direction". The Y'-axis direction corresponds to an example of the "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 lid member 40 , and a bonding portion 50 .

[0027] The quartz crystal vibrating element 10 is an electromechanical energy conversion element that converts electrical energy into mechanical energy and vice versa through the piezoelectric effect. The main mode frequency of the quartz crystal vibrating element 10 is, for example, approximately 0.8 GHz to 2.0 GHz, e.g., approximately 0.95 GHz. The inharmonic mode frequency of the quartz crystal vibrating element 10 is, for example, within a range of approximately 1% of the main mode frequency. The quartz crystal vibrating element 10 includes a thin quartz crystal piece (quartz crystal element) 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 facing the top wall portion 41 of the cover member 40. The lower surface 11B is located on the side facing 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 crystal 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 top surface 11A is viewed in a plan view in the thickness direction (hereinafter simply referred to as "plan view"), the shape of the quartz crystal blank 11 (hereinafter referred to as "planar shape") is a square with a pair of sides extending in the Z'-axis direction and a pair of sides extending in the X-axis direction. Furthermore, the quartz crystal blank 11 has a thickness in the Y'-axis direction. As an example, the shape of the quartz crystal blank 11 is a flat plate with a uniform thickness.

[0030] The planar shape of the crystal blank is not limited to the above. For example, the planar shape of the crystal blank may be rectangular with long sides extending in the Z'-axis direction and short sides extending in the X-axis direction, or may be rectangular with short sides extending in the Z'-axis direction and long sides extending in the X-axis direction. The planar shape of the crystal blank may be polygonal, circular, elliptical, or a combination thereof. Furthermore, the crystal blank is not limited to a flat plate. The crystal blank may have a mesa structure or an inverted mesa structure with irregularities on at least one of the upper surface 11A and the lower surface 11B. The crystal blank 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 crystal piece 11 is cut out with the XZ' plane as the main surface, with the Y'-axis and Z'-axis being the axes obtained 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 toward 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. The AT-cut quartz crystal vibrating element also 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 primary vibration mode.

[0033] The cut angle of the quartz crystal blank is not limited to the above. The rotation angle of the Y'-axis and Z'-axis of the AT-cut quartz crystal blank 11 may be in the range of -5 degrees or more or +15 degrees or less from 35 degrees 15 minutes. Furthermore, the cut angle of the quartz crystal blank may be a different cut 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 AC 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 planar 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, sandwiching the crystal blank 11 therebetween. The first excitation electrode 14a is an example of an "excitation electrode."

[0035] The planar shape of the first excitation electrode 14 is a rectangle with 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 those described 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 also be square, polygonal, circular, elliptical, or a combination thereof.

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

[0039] The first excitation electrode 14a, the first extraction electrode 15a, and the first connection electrode 16a are integrally formed. The same is true for the second excitation electrode 14b, the second extraction electrode 15b, and the second connection electrode 16b. These electrodes of the quartz crystal vibrating element 10 have a multilayer structure, for example, in which a base layer and a surface layer are stacked 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) primarily composed of aluminum. The electrodes of the quartz crystal vibrating element 10 may also 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 vibrating element 10 and the lid member 40, and corresponds to the mounting surface on which the quartz vibrating element 10 is mounted. From the viewpoint of suppressing thermal stress acting from the base 31 on the quartz 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 with a thermal expansion coefficient similar to that of the quartz blank 11. The base 31 is made of, for example, a ceramic substrate, a glass substrate, or a quartz substrate.

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

[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 lid member 40, and the other is a dummy electrode that is not electrically connected to the quartz crystal vibrating element 10 or the lid member 40. The external electrodes 35a, 35b, 35c, and 35d are each continuously provided from the cutout side surfaces provided at four corners of the base 31 to the bottom surface 31B. In the example shown in FIG. 2 , the external electrodes 35a and 35b are located at diagonal corners on the top surface 31A of the base 31, and the external electrodes 35c and 35d are located at another diagonal corner on the top surface 31A of the base 31. However, the external electrodes 35a, 35b, 35c, and 35d are not limited to those described above. Both the external electrodes 35c and 35d may 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, 36b electrically connect the base member 30 and the quartz vibrating element 10 and mechanically hold the quartz vibrating element 10. The conductive holding member 36a electrically connects the first connection electrode 16a of the quartz vibrating 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 quartz vibrating element 10 to the connection electrode 33b of the base member 30. The conductive holding members 36a, 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, 36b is, for example, a silicone resin. The conductive holding members 36a, 36b contain conductive particles, such as metal particles containing silver (Ag).

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

[0048] The lid member 40 forms an internal space 20 between itself and the base member 30, in which the quartz-crystal vibrating element 10 is housed. The lid member 40 has a top wall 41, a side wall 42 extending from the outer edge of the top wall 41 toward the base member 30, and a flange 43 extending outward from the tip of the mounting substrate 130. The top wall 41 faces the base member 30 in the Y'-axis direction, sandwiching the quartz-crystal vibrating element 10 therebetween. The side wall 42 surrounds the quartz-crystal vibrating element 10 at a distance in the XZ'-plane direction. The flange 43 has a frame shape in plan view and is located closest to the base member 30 on the lid member 40. The lid member 40 is preferably made of a conductive material, more preferably a highly airtight metal material. By using a conductive material for the lid member 40, an electromagnetic shielding function is imparted to the lid member 40, reducing the amount of electromagnetic waves entering and leaving the internal space 20. In order to suppress the occurrence of thermal stress, the material of the lid member 40 is preferably 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 lid member 40 is electrically connected to at least one of the external electrodes 35c, 35d by a grounding member (not shown).

[0049] The joint 50 joins the base member 30 and the lid member 40 and seals the internal space 20. The joint 50 is provided in a frame shape around the entire periphery 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 made of an insulating material. The joint 50 is provided with an organic adhesive, 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 organic adhesives, 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 also be low-melting-point glass (e.g., 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 not shown in 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 Figure 4, the thickness of the crystal blank 11 in the high acoustic velocity region 17 is the same as the thickness of the crystal blank 11 in the low acoustic velocity region 18. Furthermore, the thickness of the second excitation electrode 14b in the high acoustic velocity region 17 is the same as the thickness of the second excitation electrode 14b in the low acoustic velocity region 18. However, the thickness of the first excitation electrode 14a in the low acoustic velocity region 18 is greater than the thickness of the first excitation electrode 14a in the high acoustic velocity region 17. In other words, the high acoustic velocity region 17 is lighter than the low acoustic velocity region 18 by the difference in thickness of the first excitation electrode 14a. The acoustic velocity in the low acoustic velocity region 18 is lower than the acoustic velocity in the high acoustic velocity region 17 due to the addition of 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 lower 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, this reason may be that the thickness of the second excitation electrode in the low sound velocity region is greater than the thickness of the second excitation electrode in the high sound velocity region. This reason may be that the thickness of the quartz crystal element in the low sound velocity region is greater than the thickness of the quartz crystal element in the high sound velocity region. This 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. This 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 planar 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 central portion of the first excitation electrode 14a. The planar shape of the high acoustic velocity region 17 is a rectangle having long sides extending along the X-axis direction and short sides 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 also 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 the shape of a continuous rectangular frame 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 acoustic velocity region is not limited to a rectangular frame shape that is continuous in the circumferential direction. The planar shape of the low acoustic velocity region may be a frame shape that extends along the contour of a polygonal shape, a circle, an ellipse, or a shape that is a combination of these. Furthermore, the low acoustic velocity region may be a frame shape that is discontinuous in the circumferential direction.

[0058] The first low acoustic velocity region 18A is adjacent to the high acoustic velocity region 17 on the negative side of the Z' axis and extends along the X axis. The second low acoustic velocity region 18B is adjacent to the high acoustic velocity region 17 on the positive side of the Z' axis and extends along the X axis. The third low acoustic velocity region 18C is adjacent to the high acoustic velocity region 17 on the positive side of the X axis and extends along the Z' axis. The fourth low acoustic velocity region 18D is adjacent to the high acoustic velocity region 17 on the negative side of the X axis and extends along the Z' axis. The end of the first low acoustic velocity region 18A on the positive side of the X axis connects to the end of the third low acoustic velocity region 18C on the negative side of the Z' axis, and the end of the first low acoustic velocity region 18A on the negative side of the X axis connects to the end of the fourth low acoustic velocity 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 a plan view, the end of first low sound speed region 18A on the positive X-axis side overlaps the end of third low sound speed region 18C on the negative Z'-axis side, and the end of first low sound speed region 18A on the negative X-axis side overlaps the end of fourth low sound speed region 18D on the negative Z'-axis side. The end of second low sound speed region 18B on the positive X-axis side overlaps the end of third low sound speed region 18C on the positive Z'-axis side, and the end of second low sound speed region 18B on the negative X-axis side overlaps the end of 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 and fourth low acoustic velocity regions may be omitted. That is, the high acoustic velocity region, the first and second low acoustic velocity regions 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 X-axis side to the end on the positive X-axis side in a plan view. The first and second low acoustic velocity regions may be omitted. That is, the high acoustic velocity region, the third and fourth low acoustic velocity regions 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 Z'-axis side to the end on the positive Z'-axis side in a plan view. The end of the first low acoustic velocity region on the positive X-axis side may be spaced apart from the third low acoustic velocity region, and the end of the first low acoustic velocity region on the negative X-axis side may be spaced apart 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] Furthermore, the positional relationship between the first, second, third, and fourth low acoustic velocity regions is not limited to the above. The first low acoustic velocity region may be adjacent to the high acoustic velocity region on the positive side of the Z'-axis, and the second low acoustic velocity region may be adjacent to the high acoustic velocity region on the negative side of the Z'-axis. The third low acoustic velocity region may be adjacent to the high acoustic velocity region on the negative side of the X-axis, and the fourth low acoustic velocity region may be adjacent to the high acoustic velocity region on the positive side of the X-axis. One of the first and second low acoustic velocity regions may be adjacent to the high acoustic velocity region on the negative side of the X-axis, and the other may be adjacent to the high acoustic velocity region on the positive side of the X-axis. One of the third and fourth low acoustic velocity regions may be adjacent to the high acoustic velocity region on the negative side of the Z'-axis, and the other may be adjacent to the high acoustic velocity region on the positive side of the Z'-axis.

[0062] As shown in Figures 4 and 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 along the Y'-axis direction in the high acoustic velocity region 17 is defined as thickness Te1. The dimension of the first excitation electrode 14a along the Y'-axis direction in the low acoustic velocity region 18 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 defined as length Wx2. The dimension of the first low sound speed region 18A along the X-axis direction is defined as length Lx1. The dimension of the second low sound speed region 18B along the X-axis direction is defined as length Lx2. The dimension of the third low sound speed region 18C along the Z'-axis direction is defined as Lz1. The dimension of the fourth low sound speed region 18D along the Z'-axis direction is defined as 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 the pair of ends parallel to the X-axis direction of the first low acoustic velocity region 18A. One of the pair of ends parallel to the X-axis direction of the first low acoustic velocity region 18A 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 side of the Z′-axis.

[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 that are parallel to the X-axis direction. One of the pair of ends of the second low acoustic velocity region 18B that are parallel to the X-axis direction 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 side of the Z'-axis.

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

[0066] Similarly, the length Wx2 is determined by measuring the distance in the X-axis direction between a pair of ends of the fourth low acoustic velocity region 18D that are parallel to the Z'-axis direction. One of the pair of ends of the fourth low acoustic velocity region 18D that are parallel to the Z'-axis direction is the boundary between the high acoustic velocity region 17 and the fourth low acoustic 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 acoustic velocity region 17 is polygonal, circular, elliptical, or a combination thereof, or when the planar shape of the first excitation electrode 14a is polygonal, circular, elliptical, or a combination thereof, and the first low acoustic velocity region 18A does not have a pair of ends parallel to the X-axis direction in a planar view, the length Wz1 can be determined by a method other than the above. For example, the length Wz1 may be determined by dividing the area of ​​the first low acoustic velocity region 18A in a planar view by the dimension of the first low acoustic velocity region 18A in the X-axis direction. Alternatively, the length Wz1 may be determined by measuring multiple dimensions of the first low acoustic velocity region 18A along the Z'-axis direction at multiple positions in the X-axis direction and calculating the average value of these multiple dimensions. When measuring multiple dimensions along the Z'-axis direction, the measurement positions for the dimension 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 for the dimension 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 may be calculated by excluding at least one of the maximum and minimum values. 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 of the second low acoustic velocity region 18B that are parallel to the Z'-axis direction. One of the pair of ends of the second low acoustic velocity region 18B that are parallel to the Z'-axis direction 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 acoustic velocity region 18C that are parallel to the X-axis direction. One of the pair of ends of the third low acoustic velocity region 18C that are parallel to the X-axis direction 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.

[0071] Similarly, the length Lz2 is determined by measuring the distance in the Z'-axis direction between a pair of ends of the fourth low acoustic velocity region 18D that are parallel to the X-axis direction. One of the pair of ends of the fourth low acoustic velocity region 18D that are parallel to the X-axis direction 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.

[0072] However, when the planar shape of the high acoustic velocity region 17 is polygonal, circular, elliptical, or a combination thereof, or when the planar shape of the first excitation electrode 14a is polygonal, circular, elliptical, or a combination thereof, and the first low acoustic velocity region 18A does not have a pair of ends parallel to the Z'-axis direction in a planar view, the length Lx1 can be determined by a method other than the above. For example, the length Lx1 may be determined by dividing the area of ​​the first low acoustic velocity region 18A in a planar view by the dimension of the first low acoustic velocity region 18A in the Z'-axis direction. Alternatively, the length Lx1 may be determined by measuring multiple dimensions of the first low acoustic velocity region 18A along the X-axis direction at multiple positions in the Z'-axis direction and calculating the average value of these multiple dimensions. When measuring multiple dimensions along the X-axis direction, the measurement positions for the dimension 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 for the dimension along the X-axis direction may be determined arbitrarily. When calculating the average value of multiple dimensions along the X-axis direction, at least one of the maximum and minimum values ​​may be excluded and the average value of the remaining dimensions may be calculated. Furthermore, the length Lx1 may be specified as the dimension of the first excitation electrode 14a along the X-axis direction on a tangent line that extends in the X-axis direction and contacts the boundary between the high acoustic velocity region 17 and the first low acoustic 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 acoustic velocity region 18A in the X-axis direction corresponds to an example of the "length Lb1 of the first low acoustic velocity region in the second direction." The length Lx2 of the second low acoustic velocity region 18B in the X-axis direction corresponds to an example of the "length Lb2 of the second low acoustic velocity region in the second direction." The length Lz1 of the third low acoustic velocity region 18C in the Z'-axis direction corresponds to an example of the "length La1 of the third low acoustic velocity region in the first direction." The length Lz2 of the fourth low acoustic velocity region 18D in the Z'-axis direction corresponds to an example of the "length La2 of the fourth low acoustic velocity region in the first direction."

[0074] Note that the lengths Ea, Eb, Wa1, Wa2, Wb1, Wb2, Lb1, Lb2, La1, and La2 are not limited to those described 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 may correspond to the length Wa1, the other of the lengths Wx1 and Wx2 may correspond to the length Wa2, one of the lengths Wz1 and Wz2 may correspond to the length Wb1, and the other of the lengths Wz1 and Wz2 may correspond to the length Wb2. Furthermore, 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 at 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 at 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 at the center 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 acoustic velocity region 17 and the low acoustic 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 acoustic velocity region 17 and the low acoustic velocity region 18.

[0077] In the example shown in Figure 5, the length Wz1 of the first low acoustic velocity region 18A in the Z'-axis direction is approximately equal to the length Wz2 of the second low acoustic 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. Furthermore, from the viewpoint of ensuring the high acoustic 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, if the relationships 0.2≦Wz1 / Ez, 0.2≦Wz2 / Ez, and 0.5≦(Wz1+Wz2) / Ez≦0.96 hold, then the relationship Wz1≠Wz2 may hold, or the relationship Wz1≒Wz2 may hold.

[0078] It is desirable that both the lengths Wz1 and Wz2 be 25% or more of the length Ez. Furthermore, from the viewpoint of ensuring the high sound velocity region 17, it is desirable that both the lengths Wz1 and Wz2 be 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 be satisfied. It is desirable that the relationship Wz1 ≒ Wz2 be satisfied in order to achieve a good balance of mechanical strength, etc.

[0079] Similarly, the length Wx1 of the third low acoustic velocity region 18C in the X-axis direction is approximately equal to the length Wx2 of the fourth low acoustic 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. Furthermore, from the viewpoint of ensuring the high acoustic velocity region 17, the sum of the lengths Wx1 and Wx2 is 96% or less of the length Ex. Furthermore, as long as both 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, as long as 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] As long as the first low acoustic velocity region 18A and the second low acoustic velocity region 18B function, the lengths Lx1 and Lx2 may be smaller than the length Ex. That is, in a plan view, the end of the first low acoustic velocity region 18A on the positive X-axis side may be spaced apart in the negative X-axis direction from the end of the first excitation electrode 14a on the positive X-axis side, or the end of the first low acoustic velocity region 18A on the negative X-axis side may be spaced apart in the positive X-axis direction from the end of the first excitation electrode 14a on the negative X-axis side. However, to prevent the first low acoustic velocity region 18A and the second low acoustic velocity region 18B from disrupting the vibration mode and splitting the waveform, it is desirable that both the lengths Lx1 and Lx2 be 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 be satisfied.

[0082] Similarly, as long as the third low acoustic velocity region 18C and the fourth low acoustic velocity region 18D function, the lengths Lz1 and 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 positive Z'-axis side may be spaced in the negative Z'-axis direction from the end of the first excitation electrode 14a on the positive Z'-axis side, and the end of the fourth low acoustic velocity region 18D on the negative Z'-axis side may be spaced in the positive X-axis direction from the end of the first excitation electrode 14a on the negative Z'-axis side. However, to prevent the third low acoustic velocity region 18C and the fourth low acoustic velocity region 18D from disrupting the vibration mode and splitting the waveform, it is desirable that both the lengths Lz1 and Lz2 be 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 hold.

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

[0084] 6, the main mode frequency in the example is about 945 MHz, while the main mode frequency in the comparative example is 965 MHz. The frequency intervals between the modes in the example are wider than the frequency intervals between the modes in the comparative example. In other words, it is easier to separate the main mode from the inharmonic modes in the example 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 example, 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%. Because the S1 mode has a shorter wavelength in the X direction than the S0 mode, the influence of phase change due to the low acoustic velocity region is significant. In the comparative example, the vibration region extending in the X-axis direction from the center in the Z'-axis direction, i.e., the white region in the gray scale of FIG. 8 , is divided in the X-axis direction from the center in the X-axis direction in the example, and extends in the Z'-axis direction from the end in the X-axis direction. As a result, positive and negative charges are canceled, and the S1Z displacement in the example 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 example, 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 and spreads in the X-axis direction in the example. Therefore, in the comparative example, the vibration region extending in the Z'-axis direction at both ends in the X-axis direction, i.e., the black region in the gray scale in Fig. 9 , is divided into four corners by white regions spreading in the X-axis direction in the example.

[0088] Next, with reference to FIGS. 10 to 12 , the influence of the dimensions of the low acoustic velocity region on the electromechanical coupling coefficient k will be described. FIGS. 10 to 12 are graphs showing the influence of the planar dimensions of the low acoustic velocity region. Based on the first embodiment, k in the S0 mode and S1Z mode was calculated using variables Wx1 = Wx2 = Wx and Wz1 = Wz2 = Wz. The horizontal axis of graph (A) in FIG. 10 is Wx / Tp, and the horizontal axis of graph (B) in FIG. 10 is Wz / Tp. The vertical axis of 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 based on the first embodiment under the following conditions. When Tf = 0 μm under the following conditions, k_S0 = 6.87%: Tp = 1.52 μm Te1 = Te2 = 0.08 μm Tf = 0.02 μm Px = Pz = 120 μm Ex = 100 μm Ez = 80 μm Wx1 = Wx2 = Wx: variable Wz1 = Wz2 = Wz: variable

[0089] 10, when Wx / Tp and Wz / Tp are 16.5≦Wx / Ex and 13.2≦Wz / Tp, i.e., when Wx / Ex and Wz / Ez are 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., when 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 Figure 11 indicate the range in which k_S0 is improved compared to the k_S0 = 6.87% of 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 line, are satisfied, k_S0 becomes 7.1% ≤ k_S0. Also, when the relationships 0.8 < 5.0 × (Wx / Ex) ≤ 0.48, which are the range surrounded by the dotted line, are satisfied, k_S0 becomes 7.1% ≤ k_S0. ２ +4.0×(Wz / Ez) ２When the relationships Wx / Ex≦0.48 and Wz / Ez≦0.48 are satisfied, k_S0 is 6.90%≦k_S0. 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 Figure 12 indicates the range in which k_S1Z is particularly reduced. When the relationships 0.30 ≤ Wx / Ex ≤ 0.43 and 0.30 ≤ Wz / Ez ≤ 0.48 are satisfied, k_S1Z ≤ 1.0% is satisfied. When the relationships 0.30 ≤ Wx / Ex ≤ 0.46 and 0.31 ≤ Wz / Ez ≤ 0.46 are satisfied, k_S1Z ≤ 1.0% is satisfied. When the relationships 0.30 ≤ Wx / Ex ≤ 0.47 and 0.34 ≤ Wz / Ez ≤ 0.44 are satisfied, k_S1Z ≤ 1.0% is satisfied. In particular, when the relationships Wx / Ex = 0.40 ± 0.05 and Wz / Ez = 0.40 ± 0.05 are 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 when Tf=0 μm under the following conditions, k_S0=6.87%: Tp=1.52 μm Te1=Te2=Te=0.08 μm Tf: 0.01 μm, 0.02 μm, 0.03 μm, 0.05 μm, 0.07 μm, 0.10 μm 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, i.e., 0.25≦Wx / Ex, holds, k_S0 improves, and k_S0 becomes 6.87%<k_S0. In the range of 25.0≦Wx≦48.0, i.e., the range of 0.25≦Wx / Ex≦0.48, k_S0 shows a similar trend with respect to Wx regardless of whether Tf is 0.01 μm, 0.02 μm, 0.03 μm, 0.05 μm, 0.07 μm, or 0.10 μm. In other words, in the range of 0.01 μm≦Tf≦0.10 μm, i.e., the range of 0.125≦Tf / Te1≦1.25, the condition for k_S0 to increase is independent of Tf, and k_S0 becomes 6.87%<k_S0 in the range of 0.25≦Wx / Ex≦0.48.

[0095] 14, the horizontal axis represents Wx, and the vertical axis represents k_S0 calculated under the following conditions based on the first embodiment. Note that when Te1=Te2=0.05 μm and Tf=0 μm under the following conditions, k_S0=6.87%: Tp=1.52 μm 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 20 μm≦Wx≦48 μm, i.e., 0.20≦Wx / Ex≦0.48, holds, k_S0 improves, becoming 6.74%<k_S0. When the relationship 25 μm≦Wx≦48 μm, i.e., 0.25≦Wx / Ex≦0.48, holds, k_S0 improves further, becoming 7.00%≦k_S0. Within the range of 0.20≦Wx / Ex≦0.48, k_S0 shows a similar tendency with respect to Wx for all cases where Te = 0.02 μm, 0.05 μm, 0.08 μm, 0.10 μm, 0.15 μm, 0.20 μm, and 0.30 μm. In other words, in the range of 0.02 μm≦Te≦0.30 μm, i.e., 0.132≦Te / Tp≦0.197, the condition for improving k_S0 does not depend on Te, and in the range of 0.20≦Wx / Ex≦0.48, 6.87%<k_S0 is satisfied, and in the range of 0.25≦Wx / Ex≦0.48, 7.00%≦k_S0 is satisfied.

[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 acoustic velocity region 18A in the Z'-axis direction is Wz1, and the length of the second low acoustic velocity region 18B in the Z'-axis direction is Wz2, the relationships 0.20≦Wz1 / Ez, 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] This makes it possible to suppress spurious vibrations in the Z'-axis direction and improve the electromechanical coupling coefficient k of the main mode.

[0099] Furthermore, 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 acoustic velocity region 18A in the X-axis direction is Wx1, and the length of the second low acoustic velocity region 18B in the X-axis direction is Wx2, the relationships 0.20≦Wx1 / Ex, 0.20≦Wx2 / Ex, and 0.50≦(Wx1+Wx2) / Ex≦0.96 are satisfied. Preferably, the relationships 0.25≦Wx1 / Ex≦0.48 and 0.25≦Wx2 / Ex≦0.48 are satisfied.

[0100] This makes it possible to suppress spurious vibrations 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 main mode electromechanical coupling coefficient k, it is desirable that both of the following relationships be 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 be 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] Furthermore, according to this 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 acoustic velocity region 18A and the second low acoustic velocity region 18B from disrupting the vibration form and splitting the waveform.

[0106] Furthermore, according to this embodiment, when the length of the third low sound velocity region 18C in the Z'-axis direction is Lz1 and the length of the fourth low sound velocity 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 acoustic velocity region 18C and the fourth low acoustic velocity region 18D from disrupting 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 true.

[0109] According to this, within the ranges of 0.25≦Wz / Ez≦0.48 and 0.25≦Wx / Ex≦0.48, or 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 true.

[0111] According to this, within the ranges of 0.25≦Wz / Ez≦0.48 and 0.25≦Wx / Ex≦0.48, or 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] Furthermore, according to this embodiment, the thickness Te 1 +Tf of the first excitation electrode 14 a in the low acoustic velocity region 18 is greater than the thickness Te 1 of the first excitation electrode 14 a in the high acoustic velocity region 17 .

[0113] According to this, due to the difference in thickness of the first excitation electrode 14a, the acoustic velocity in the low acoustic velocity region 18 can be made lower than that in the high acoustic velocity region 17. In other words, the high acoustic velocity region 17 and the low acoustic velocity region 18 can be formed by further stacking 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 this is not limited to this. 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 is 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] Furthermore, the present invention is not limited to a configuration in which the high acoustic velocity region 17 and the low acoustic velocity region 18 are formed solely by a difference in thickness of the first excitation electrode 14a. For example, the high acoustic velocity region and the low acoustic velocity region may be formed by making the thickness of the end portion of the second excitation electrode greater than the thickness of the central portion. Furthermore, the high acoustic velocity region and the low acoustic velocity region may be formed by making the thickness of the end portion of both the first excitation electrode and the second excitation electrode greater than the thickness of the central portion.

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

[0117] Second Embodiment Next, the configuration of a quartz crystal vibrating element 210 according to a 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] 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 located in the center of the first excitation electrode 214a in the Z′-axis direction and is provided in a region extending in the X-axis direction. The first low acoustic velocity region 218A is adjacent to the high acoustic velocity region 217 on the negative Z′-axis side and is provided in a region extending in the X-axis direction. The second low acoustic velocity region 218B is adjacent to the high acoustic velocity region 217 on the positive Z′-axis side and is provided in a region extending in the X-axis direction. In a plan view, 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 extending from the end of the first excitation electrode 214a on the negative X-axis side to the end on the positive X-axis side.

[0119] Third Embodiment Next, the configuration of a quartz crystal vibrating element 310 according to a 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] 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 located in the center of the first excitation electrode 314a in the X-axis direction and is provided in a region extending in the Z′-axis direction. The third low acoustic velocity region 318C is adjacent to the high acoustic velocity region 317 on the positive X-axis side and is provided in a region extending in the Z′-axis direction. The fourth low acoustic velocity region 318D is adjacent to the high acoustic velocity region 317 on the negative X-axis side and is provided in a region extending in the Z′-axis direction. In a plan view, 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 extending from the end of the first excitation electrode 314a on the negative Z′-axis side to the end on the positive Z′-axis side.

[0121] Fourth Embodiment Next, the 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] 17 , the quartz crystal vibrating element 410 has a high acoustic velocity region 417, a first low acoustic velocity region 418A, a second low acoustic velocity region 418B, a third low acoustic velocity region 418C, and a fourth low acoustic velocity region 418D. The thickness of the first excitation electrode 414a in the high acoustic velocity region 417 and the low acoustic velocity region 418 is Te1. In the high acoustic velocity region 417, the first excitation electrode 414a has a plurality of holes H formed therein. The holes H are through holes that penetrate the first excitation electrode 414a in the Y′-axis direction. However, the holes are not limited to through holes, and the holes may be grooves with bottoms that open in the Y′-axis direction.

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

[0124] 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 a rectangular shape where H<Hx or Hx<Hx. As shown in FIG. 32, the planar shape of the hole H may be a circle. As shown in FIG. 33, the planar shape of the hole H may be an ellipse. As shown in FIG. 34, the planar shape of the hole H may be a square with arc-shaped corners. Thus, the planar shape of the hole H may be a polygon, a circle, an ellipse, or a combination thereof.

[0125] As shown in Figure 17, the multiple holes H are arranged in a matrix in the X-axis direction and the X'-axis direction. The pitch of the multiple holes H in the Z'-axis direction, i.e., the distance between the ends of two adjacent holes H in the Z'-axis direction on the negative side of the Z'-axis, is defined as PHz. The pitch of the holes H in the X-axis direction, i.e., the distance between the ends of two adjacent holes H in the X-axis direction on the negative side of the X-axis, is defined as PHx. The multiple holes H are arranged at equal intervals in both the Z'-axis direction and the X-axis direction. In other words, PHz = PHx.

[0126] The pitch of the multiple holes H is not limited to the above, and may be PHz<PHx, or PHx<PHz. Furthermore, the arrangement of the multiple holes H is not limited to the above. The multiple 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 multiple holes H may be arranged in a staggered pattern. As shown in FIG. 35, the multiple holes H may be arranged randomly.

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

[0128] 19 has the following configurations: (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 Hs: 8 × 8 = 64 (Comparative Example) Tp = 1.52 μm Te1 = Te2 = 0.08 μm Px = Pz = 140 μm Ex = 100 μm Ez = 80 μm Wx = 0 μm Wz = 0 μm

[0129] As shown in the frequency distribution graph in Figure 19, the main mode frequency in the example is approximately 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 in the comparative example, while in the example based on the fourth embodiment, the frequency is higher than in the comparative example. This is because, in the first embodiment, mass is added to the low acoustic velocity region to create a difference in acoustic velocity between the low acoustic velocity region and the high acoustic velocity region, whereas in the fourth example, the mass in the high acoustic velocity region is reduced to create a difference in acoustic velocity between the low acoustic velocity region and the high acoustic velocity region. Therefore, when increasing the frequency, the quartz crystal vibrating 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 = 1.52 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: variable Number of H: 8 × 8 = 64 (Example based on the first embodiment) Tp = 1.52 μm Te3 (= Te1 + Tf) = Te2 = 0.08 μm Te1: variable Px = Pz = 140 μm Ex = 100 μm Ez = 80 μm Wx = 40 μm Wz = 30 μm

[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 opening 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, it is believed that the electromechanical coupling coefficient is improved in the fourth embodiment by the same mechanism as in the first embodiment.

[0135] Next, the effect of the hole H on the function as an excitation electrode will be described with reference to Figure 21. Figure 21 is a graph showing the effect of the planar dimensions of the hole. The horizontal axis of the graph in Figure 21 represents the ratio Hr / Tp, where Hx = Hz = Hr, of the length of one side of the square-shaped hole H in plan view to the thickness Tp of the crystal blank 11. The vertical axis of the graph in Figure 21 represents the capacitance normalized by the capacitance when no hole H is formed.

[0136] If the length Hr of the hole H is less than twice the thickness Tp of the crystal blank 11, i.e., if the relationship 0<Hr / Tp≦2.0 holds, the capacitance reduction rate can be kept to 1% or less, allowing the electrode to function satisfactorily as an excitation electrode. Desirably, the length Hr of the hole H is less than 1.5 times the thickness Tp of the crystal blank 11, i.e., if the relationship 0<Hr / Tp≦1.5 holds, and even more desirably, the length Hr of the hole H is less than 1.0 times the thickness Tp of the crystal blank 11, i.e., if the relationship 0<Hr / Tp≦1.0 holds, the capacitance reduction rate can be kept to 0.5% or less. If the relationship 0<Hr / Tp≦1.0 holds, the capacitance reduction rate can be kept to 0.1% or less. In order to form the hole H with sufficient processing precision, it is desirable that the length Hr of the hole H be 0.1 times or more the thickness Tp of the quartz crystal blank 11, i.e., 0.1≦Hr / Tp, and it is even more desirable that the length Hr of the hole H be 0.5 times or more the thickness Tp of the quartz crystal blank 11, i.e., 0.5≦Hr / Tp.

[0137] 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 to a square while keeping the area constant. Even in such a case, as in the case where the planar shape of the hole H is square, if the relationship 0<Hr / Tp≦2.0 holds, the capacitance reduction rate can be kept to 1% or less, and the hole H can function sufficiently as an excitation electrode. Furthermore, as in the case where the planar shape of the hole H is square, if 0<Hr / Tp≦1.5, the capacitance reduction rate can be kept to 0.5% or less, and if 0<Hr / Tp≦1.0, the capacitance reduction rate can be kept to 0.1% or less.

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

[0139] As shown in Fig. 22, k_S0 shows a similar tendency with respect to Har when PHz = PHx = 3 μm, 2 μm, or 1 μm. Also, as shown in Fig. 23, k_S0 shows a similar tendency with respect to Ter when PHz = PHx = 3 μm, 2 μm, or 1 μm. In other words, the main mode electromechanical coupling coefficient k_S0 is determined by Har and Ter, regardless of the pitches PHz and PHx of the multiple holes H. According to the graph in Fig. 22, k_S0 is maximized when the relationship Har = 0.1 ± 0.05 holds. According to the graph in Fig. 23, k_S0 is maximized when the relationship Ter = 0.93 ± 0.03 holds.

[0140] According to this embodiment, the high acoustic velocity region 417 and the low acoustic velocity region 418 can be formed by the first excitation electrode 414a having a single-layer structure. In a configuration in which a first metal film of uniform thickness is provided in the high acoustic velocity region and the low acoustic velocity region, and then a second metal film is provided to form the low acoustic velocity region, or in a configuration in which an insulating mass-adding film is provided to form the low acoustic velocity region, manufacturing variations due to misalignment of the second metal film or the mass-adding film may prevent the formation of a low acoustic velocity region of the desired width. In contrast, according to this embodiment, even if the positions of the multiple holes H are misaligned, the position of the high acoustic velocity region 417 simply changes, and the low acoustic velocity region 418 of the desired width can be formed.

[0141] Fifth Embodiment Next, the configuration of a quartz crystal vibrating element 510 according to a fifth embodiment will be described with reference to Fig. 24. Fig. 24 is a cross-sectional view of the quartz crystal vibrating element according to the fifth embodiment.

[0142] The thickness of the first excitation electrode 514a in the high acoustic velocity region 517 and the low acoustic velocity region 518 is Te1. In the high acoustic velocity region 717, a plurality of holes H are formed in the first excitation electrode 514a. In the low acoustic velocity region 718, a plurality of sub-holes h are formed in the first excitation electrode 514a. The sub-holes h are through-holes that penetrate the first excitation electrode 514a in the Y'-axis direction. However, the sub-holes h are not limited to through-holes, and may be grooves with a bottom that open in the Y'-axis direction.

[0143] The dimension of the sub-hole h in the Z'-axis direction is defined as hz, and the dimension of the sub-hole h in the X-axis direction is defined as hx. The planar shape of the sub-hole h is a square having a side extending along the Z'-axis direction and a side extending along the X-axis direction. In other words, hz = hx. However, the planar shape of the sub-hole h is not limited to a square, and may be a rectangle where hz < hx, or a rectangle where hx < hz. The planar shape of the sub-hole h may be a polygon, a circle, an ellipse, or a combination thereof.

[0144] The pitch of the sub-holes h in the Z'-axis direction, i.e., the distance between the ends of two adjacent sub-holes h in the Z'-axis direction on the negative side of the Z'-axis, is defined as Phz. The pitch of the sub-holes h in the X-axis direction, i.e., the distance between the ends of two adjacent sub-holes h in the X-axis direction on the negative side of the X-axis, is defined as Phx. The sub-holes h are arranged at equal intervals in both the Z'-axis direction and the X-axis direction. In other words, Phz = Phx. However, the pitch of the sub-holes h is not limited to the above, and Phz < Phx or Phx < Phz may be satisfied. Furthermore, the arrangement direction of the sub-holes h 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 sub-holes h may also be arranged in a staggered pattern.

[0145] In a plan view, the area hz × hx of the sub-hole h is smaller than the area Hz × Hx of the hole H. The pitch Phz of the sub-holes h is approximately equal to the pitch PHz of the holes H (Phz ≈ PHz). Furthermore, the pitch Phx of the sub-holes h is approximately equal to the pitch PHx of the holes H (Phx ≈ PHx).

[0146] Next, a simulation result of an example based on the fifth embodiment will be described with reference to Fig. 25. 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 an 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 Hs: 8 × 8 = 64 Phz = Phx = 3 μm hx = hz = 0.5 μm The configuration of the example based on the fourth embodiment is the same as the example shown in FIG. 19 , and is the same as the configuration of the example based on the fifth embodiment, except that the multiple sub-holes h are not formed.

[0148] In the example based on the fifth embodiment, k_S0 = 7.41%, k_S1Z = 0.17%, and k_S1Z = 1.08%. In the example based on the fifth embodiment, as in the example based on the fourth embodiment, 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.

[0149] According to this embodiment, by adjusting the ratio between the opening rate Har of the multiple holes H and the opening rate har of the multiple sub-holes 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, as long as the relationship har<Har holds between the aperture ratio har of the sub-holes h and the aperture ratio Har of the holes H, the dimensions hz, hx and pitches Phx, Phz of the sub-holes h are not limited to those described above. The aperture ratio har is expressed by the following formula: har=(hx / Phx)×(hz / Phz).

[0151] For example, if the relationship har<Har is established, the pitch Phz of the sub-holes h may be smaller than the pitch PHz of the holes H (Phz<PHz), and the pitch Phx of the sub-holes h may be smaller than the pitch PHx of the holes H (Phx<PHx). In this case, for the relationship har<Har to be established, the area hz×hx of the sub-holes h must be smaller than the area Hz×Hx of the holes H (hz×hx<Hz×Hx).

[0152] For example, if the relationship har<Har is established, the area hz×hx of the sub-holes h may be equal to or larger than the area Hz×Hx of the holes H (Hz×Hx≦hz×hx). In this case, for the relationship har<Har to be established, at least one of the following relationships must be established: the pitch Phz of the sub-holes h is larger than the pitch PHz of the holes H (PHz<Phz), and the pitch Phx of the sub-holes h is larger than the pitch PHx of the holes H (PHx<Phx).

[0153] However, even if the area hz × hx of the sub-hole h is larger than the area Hz × Hx of the hole H (Hz × Hx < hz × hx), the relationship 0 < hr / Tp ≦ 2.0 holds true for the side length hz = hx = hr of the sub-hole h, similar to the side length Hz = Hx = Hr of the hole H. This allows the capacitance reduction rate to be kept to 1% or less, allowing the low acoustic velocity region 518 to function as an excitation electrode. If 0 < hr / Tp ≦ 1.5, the capacitance reduction rate can be kept to 0.5% or less, and if 0 < Hr / Tp ≦ 1.0, the capacitance reduction rate can be kept to 0.1% or less.

[0154] Sixth Embodiment Next, the configuration of a quartz crystal vibrating element 610 according to a sixth embodiment will be described with reference to Fig. 26. Fig. 26 is a cross-sectional view of the quartz crystal vibrating element according to the sixth embodiment.

[0155] The first excitation electrode 614a has a high acoustic velocity electrode E17 provided in the high acoustic velocity region 617 and a low acoustic velocity electrode E18 provided in the low acoustic velocity region 618. The high acoustic velocity electrode E17 and the low acoustic velocity electrode E18 are continuous in the Z'-axis direction and the X-axis direction. The thickness Te17 of the high acoustic velocity electrode E17 is approximately equal to the thickness Te18 of the low acoustic velocity electrode E18 (Te17 ≒ Te18). The material of the high acoustic velocity electrode E17 is different from the material of the low acoustic velocity electrode E18. The specific gravity of the low acoustic velocity electrode E18 is greater than the specific gravity of the high acoustic 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 structure of an example based on the sixth embodiment is as follows: Tp = 1.52 μm Te17 = Te18 = Te2 = 0.08 μm Px = Pz = 140 μm Ex = 100 μm Ez = 80 μm Wx = 40 μm Wz = 30 μm 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 the 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 a 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 acoustic velocity region 717 is smaller than a thickness Te3 of the first excitation electrode 714a in the low acoustic velocity region 718. In other words, the relationship Te3 = Te1 + Tf holds true. In the high acoustic 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 acoustic velocity region 718 is thicker than the thickness Te1 of the first excitation electrode 714a in the high acoustic velocity region 717 by Tf, and therefore the acoustic velocity in the low acoustic velocity region 718 is reduced. Furthermore, since a plurality of holes H are formed in the first excitation electrode 714a in the high acoustic velocity region 717, the acoustic velocity in the high acoustic velocity region 717 increases. That is, the difference in acoustic velocity between the high acoustic velocity region 717 and the low acoustic velocity region 718 is further increased.

[0162] Eighth Embodiment Next, the configuration of a quartz crystal vibrating element 810 according to an 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 that overlaps with the first excitation electrode 814a in plan view, the crystal blank 811 is formed in an inverted mesa shape. The acoustic velocity in the low acoustic velocity region 818 is smaller than the acoustic velocity in the high acoustic velocity region 817 by the difference in thickness of the crystal blank 811, Tp2-Tp1.

[0164] Ninth Embodiment Next, the configuration of a quartz crystal vibrating element 910 according to a 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 acoustic velocity region 918. In plan view, the mass-adding film AD is provided outside the high acoustic velocity region 917, in a region overlapping the low acoustic velocity region 918. The mass-adding film AD adds mass to the low acoustic velocity region 918, making the mass per unit area in plan view of the low acoustic velocity region 918 greater than the mass per unit area in plan view of the high acoustic velocity region 917. As a result, the mass-adding film AD reduces the acoustic velocity in the low acoustic velocity region 918. The material of the mass-adding film AD is, for example, an insulator. From the viewpoint of efficiently reducing the acoustic velocity in the low acoustic 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 be greater than the specific gravity of the first excitation electrode 914a.

[0166] Although the mass addition film AD is provided on the first excitation electrode 914a, the position of the mass addition film is not limited thereto as long as it is provided in an area overlapping the first excitation electrode or the second excitation electrode in the low acoustic velocity region. The mass addition 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. Furthermore, the material of the mass addition film AD is an insulator, but is not limited thereto. The material of the mass addition film may be, for example, a metal different from that of the first excitation electrode, or a semiconductor.

[0167] Some or all of the embodiments of the present invention will be described below, but 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, 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 overlapping a central portion of the excitation electrode in a plan view in the thickness direction, the low acoustic velocity region including a first low acoustic velocity region and a second low acoustic velocity region being provided in a region overlapping an end portion of the excitation electrode surrounding the high acoustic velocity region in a plan view in the thickness direction, the first low acoustic velocity region being adjacent to the high acoustic velocity region in a first direction intersecting the thickness direction, the second low acoustic velocity region being adjacent to the high acoustic velocity region on the opposite side to the first low acoustic velocity region, wherein, 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, 0.20≦Wa1 / Ea and 0.20≦Wa2 / Ea and A piezoelectric vibration element in which the relationship 0.5≦(Wa1+Wa2) / Ea≦0.96 holds.

[0169] <2> The piezoelectric vibration element according to <1>, wherein the relationships 0.25≦Wa1 / Ea≦0.48 and 0.25≦Wa2 / Ea≦0.48 are satisfied.

[0170] <3> The piezoelectric vibration element according to <1> or <2>, wherein 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 planar view in the thickness direction, and the third low acoustic velocity region is adjacent to the high acoustic velocity region in a second direction intersecting the thickness direction and the first direction, 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, wherein the length of the excitation electrode in the second direction is Eb, the length of the third low acoustic velocity region in the second direction is Wb1, and the length of the fourth low acoustic velocity region in the second direction is Wb2, the relationships 0.20≦Wb1 / Eb, 0.20≦Wb2 / Eb, and 0.5≦(Wb1+Wb2) / Eb≦0.96 hold.

[0171] <4> The piezoelectric vibration element according to <3>, wherein the relationships 0.25≦Wb1 / Eb≦0.48 and 0.25≦Wb2 / Eb≦0.48 are satisfied.

[0172] <5> A piezoelectric vibration element including a piezoelectric piece and an excitation electrode, 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 overlapping a central portion of the excitation electrode in a plan view in the thickness direction, the low acoustic velocity region including 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 being provided in a region overlapping an end portion of the excitation electrode surrounding the high acoustic velocity region in a plan view in the thickness direction, the first low acoustic velocity region being adjacent to the high acoustic velocity region in a first direction intersecting with the thickness direction, and the second low acoustic velocity region being adjacent to the high acoustic velocity region on a side opposite to the first low acoustic velocity region, the third low acoustic velocity region being adjacent to the high acoustic velocity region in a second direction intersecting with the thickness direction and the first direction, 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 acoustic velocity region and the second low acoustic velocity region in the first direction is Wa, and the length of each of the third low acoustic velocity region and the fourth low acoustic velocity region in the second direction is Wb, 0.8<5.0×(Wa / Ea) ２ +4.0×(Wb / Eb) ２A piezoelectric vibration element in which the relationships Wa / Ea≦0.48 and Wb / Eb≦0.48 are satisfied.

[0173] <6> A piezoelectric vibration element described in any one of <3> to <5>, wherein, in a planar view in the thickness direction, one end of the first low acoustic velocity region in the second direction overlaps with one end of the third low acoustic velocity region in the first direction, the other end of the first low acoustic velocity region opposite to the one end of the second low acoustic velocity region in the second direction overlaps with one end of the fourth low acoustic velocity region in the first direction, one end of the second low acoustic velocity region in the second direction overlaps with the other end of the third low acoustic velocity region opposite to the one end of the second low acoustic velocity region in the first direction, and the other end of the second low acoustic velocity region opposite to the one end of the second low acoustic velocity region in the second direction overlaps with the other end of the fourth low acoustic velocity region opposite to the one end of the first direction.

[0174] <7> The piezoelectric vibration element according to any one of <1> to <6>, wherein the first low acoustic velocity region and the second low acoustic velocity region extend along a second direction intersecting the first direction in a planar view, and when the length of the excitation electrode in the second direction is Eb, the length of the first low acoustic velocity region in the second direction is Lb1, and the length of the first low acoustic velocity region in the second direction is Lb2, the relationships 0.8≦Lb1 / Eb≦1.0 and 0.8≦Lb2 / Eb≦1.0 hold.

[0175] <8> The piezoelectric vibration element according to any one of <3> to <6>, wherein the third low acoustic velocity region and the fourth low acoustic velocity region extend along a first direction in a planar view, and when the length of the third low acoustic velocity region in the first direction is La1 and the length of the fourth low acoustic velocity region in the first direction is La2, the relationships 0.8≦La1 / Ea≦1.0 and 0.8≦La2 / Ea≦1.0 hold.

[0176] <9> The piezoelectric vibration element according to any one of <3> to <6>, wherein, 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 acoustic velocity region and the second low acoustic velocity region in the first direction is Wa, and the length of each of the third low acoustic velocity region and the fourth low acoustic velocity region in the second direction is Wb, the relationships Wa / Ea = 0.35 ± 0.05 and Wb / Eb = 0.35 ± 0.05 hold.

[0177] <10> The piezoelectric vibration element according to any one of <3> to <6>, wherein, 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 acoustic velocity region and the second low acoustic velocity region in the first direction is Wa, and the length of each of the third low acoustic velocity region and the fourth low acoustic velocity region in the second direction is Wb, the relationships Wa / Ea = 0.40 ± 0.05 and Wb / Eb = 0.40 ± 0.05 hold.

[0178] <11> The piezoelectric vibration element according to any one of <1> to <10>, wherein the thickness of the excitation electrode in the low acoustic velocity region is greater than the thickness of the excitation electrode in the high acoustic velocity region.

[0179] <12> The piezoelectric vibration element according to any one of <1> to <11>, further comprising a mass-adding film overlapping the excitation electrode in a low acoustic velocity region.

[0180] <13> The piezoelectric vibration element according to <12>, wherein the mass-adding film is made of a metal different from that of the excitation electrode.

[0181] <14> The piezoelectric vibration element according to <12>, wherein the mass-adding film is made of an insulating material different from that of the piezoelectric piece.

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

[0183] <16> The piezoelectric vibration element according to claim 15, wherein the plurality of holes are through holes that penetrate the excitation electrode in a thickness direction, the thickness of the piezoelectric piece is Tp, and when the shape of the plurality of holes is square in plan view, the length of one side of the square is Hr, and when the shape of the plurality of holes is other than square, the length of one side when the shape is converted to a square while keeping the area constant is Hr, a relationship of 0<Hr / Tp≦2.0 is established. The piezoelectric vibration element according to <15>.

[0184] <17> The piezoelectric vibration element according to <15> or <16>, wherein in a low acoustic 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, the thickness of the piezoelectric piece is Tp, and when the shape of the plurality of holes is square in plan view, the length of one side of the plurality of holes is hr, and when the shape of the plurality of holes is other than square, the length of one side when the holes are converted into a square shape while keeping the area constant is hr, the relationship 0<hr / Tp≦2.0 holds.

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

[0186] <19> The piezoelectric vibration element according to any one of <1> to <18>, wherein the thickness of the piezoelectric piece in the low acoustic velocity region is greater than the thickness of the piezoelectric piece in the high acoustic velocity region.

[0187] <20> The piezoelectric vibration element according to any one of <1> to <19>, wherein a main vibration mode is thickness-shear vibration.

[0188] <21> The piezoelectric vibration element according to any one of <1> to <20>, wherein the piezoelectric piece is a quartz crystal piece.

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

[0190] It should be noted that the embodiment of the present invention is not limited to a quartz crystal resonator, and can also 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 the present invention is not limited to these and can be selected as appropriate.

[0191] The embodiments according to the present invention are not particularly limited and can be appropriately applied to any device that performs electromechanical energy conversion using the piezoelectric effect, such as a timing device, a sound generator, an oscillator, or a load sensor.

[0192] As described above, according to one aspect of the present invention, it is possible to provide a piezoelectric vibration element that can improve the electromechanical coupling coefficient.

[0193] The above-described embodiments are intended to facilitate understanding of the present invention and are not intended to limit the scope of the present invention. The present invention may be modified or improved without departing from its spirit, and equivalents are also included within the scope of the present invention. In other words, designs modified by those skilled in the art as appropriate to the embodiments and / or modifications are also encompassed within the scope of the present invention as long as they incorporate the characteristics of the present invention. For example, the elements and their arrangements, materials, conditions, shapes, sizes, etc. of the embodiments and / or modifications are not limited to those illustrated and can be modified as appropriate. Furthermore, the embodiments and modifications are merely examples, and it goes without saying that partial substitutions or combinations of the components shown in different embodiments and / or modifications are possible. These are also encompassed within the scope of the present invention as long as they incorporate the characteristics of the present invention.

[0194] 100...Crystal oscillator 1...Crystal resonator 10...Crystal vibrating element 11...Crystal piece 11A...Top surface 11B...Bottom surface 14a...First excitation electrode 14b...Second excitation electrode 17...High sound speed region 18...Low sound speed region 18A...First low sound speed region 18B...Second low sound speed region 18C...Third low sound speed 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, 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 as follows: Piezoelectric vibration element.

2. 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 .

3. 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.

4. 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 2 or 3.

5. 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 .

6. 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 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: The piezoelectric vibration element according to claim 2 or 3.

7. 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 2 or 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=0.40±0.05 and, Wb / Eb=0.40±0.05 The relationship is established as follows: The piezoelectric vibration element according to claim 2 or 3.

9. 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 .

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

11. The material of the mass addition film is a metal different from that of the excitation electrode. The piezoelectric vibration element according to claim 10.

12. The material of the mass-adding film is an insulator different from that of the piezoelectric piece. The piezoelectric vibration element according to claim 10.

13. A plurality of holes are formed in the excitation electrode in the high sound velocity region. The piezoelectric vibration element according to claim 1 .

14. 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 13.

15. 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 13.

16. 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 .

17. 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 .

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