Crystal vibrator and crystal vibration device

A crystal vibration device, comprising:

• a base member;
• a lid member connected to the base member to form a hermetically sealed inner space;
• and
• a crystal vibrator housed in the inner space, the crystal vibrator comprising:
• an AT-cut crystal substrate including a crystallographic axes including an X axis, a Y axis, and a Z axis and having a Z′ axis that is obtained by rotating the Z axis around the X axis by a predetermined angle greater than 0°, the AT-cut crystal substrate having a principal surface that is parallel to a plane defined by the X axis and the Z′ axis;
• an excitation electrode disposed on the principal surface of the AT-cut crystal substrate;
• and
• an extension electrode electrically connected to the excitation electrode,
• wherein the AT-cut crystal substrate includes a vibration portion and a peripheral portion surrounding the vibration portion and having a thickness less than the vibration portion,
• wherein the AT-cut crystal substrate has a longitudinal direction parallel to the Z′-axis direction and a transverse direction parallel to the X-axis direction,
• wherein the vibration portion has a first edge side lateral surface abutting the peripheral portion at an acute angle θ1 at a first side of the AT-cut crystal substrate, and a tapered lateral surface adjacent to the first edge side lateral surface and angled relative to the X axis in a view of the plane defined by the X axis and the Z′ axis,
• wherein the tapered lateral surface abuts the peripheral portion at an angle θ′ that is larger than the acute angle θ1, and
• wherein the extension electrode extends from the excitation electrode and is disposed on at least a portion of the tapered lateral surface extending to the first side of the AT-cut crystal substrate.

A crystal vibrator, comprising:

• an AT-cut crystal substrate including a crystallographic axes having an X axis, a Y axis, a Z axis and a Z′ axis that is obtained by rotating the Z axis of the AT-cut crystal substrate around the X axis by a predetermined angle, wherein the AT-cut crystal substrate has a principal surface parallel to a plane defined by the X axis and the Z′ axis;
• an excitation electrode disposed on the principal surface of the AT-cut crystal substrate;
• and
• an extension electrode electrically connected to the excitation electrode,
• wherein the AT-cut crystal substrate includes a vibration portion and a peripheral portion that surrounds the vibration portion and has a thickness less than the vibration portion,
• wherein the AT-cut crystal substrate is rectangular shaped with a first pair of opposing sides extending in a first direction parallel to the X-axis direction and a second pair of opposing extending in a second direction parallel to the Z′-axis direction and perpendicular to the first direction,
• wherein the vibration portion has a first lateral side surface that abuts the peripheral portion at an angle θ1 at one side of the first pair of opposing sides of the AT-cut crystal substrate,
• wherein the vibration portion has a second lateral side surface that abuts the peripheral portion at an angle θ2 at one side of the second pair of opposing sides of the AT-cut crystal substrate,
• wherein the vibration portion has a tapered lateral surface between the first and second lateral side surfaces, the tapered lateral surface abutting the peripheral portion at an angle θ′, wherein θ1<θ′<θ2, and
• wherein the extension electrode extends from the excitation electrode and is disposed on at least a portion of the tapered lateral surface of the vibration portion.