AT cut quartz crystal resonator element and method for manufacturing the same

1. An AT cut quartz crystal resonator element comprising:

a quartz crystal element piece having an exciting part formed from an AT cut quartz crystal plate in a rectangular shape, the rectangular shape having four sides, each side including a side surface, having an X-axis direction of a quartz crystal set to a long side of the four sides having two ends; and

an exciting electrode formed on each of front and back main surfaces of the exciting part, wherein:

each side surface at the two ends of the long side of the exciting part is composed of two faces, an m-face of a quartz crystal and a crystal face other than the m-face.

2. The AT cut quartz crystal resonator element according to claim 1 , wherein: the crystal face other than the m-face is tilted at an angle of 3 degrees ±30 minutes with respect to a normal direction of the main surface of the exciting part.

3. The AT cut quartz crystal resonator element according to claim 1 , wherein: the quartz crystal element piece includes a thick center portion and a thin surrounding portion both composing the exciting electrode; and each side surface in a longitudinal direction of a step between the thick center portion and the thin surrounding portion is composed of the in-face of the quartz crystal or the crystal face other than the m-face.

4. The AT cut quartz crystal resonator element according to claim 3 , wherein: a difference in a thickness between the thick center portion and the thin surrounding portion is set to smaller than or equal to 10% of a thickness of the thick center portion.