Patent ID: 8692632

Claim:
A resonator element comprising: a base portion; a resonating arm that is extended from the base portion, in a first direction, the resonating arm having a first surface and a second surface opposite to the first surface; an elongated groove that is formed in the first surface of the resonating arm and that is extended in the first direction, wherein the resonating arm comprises: a weight portion; an arm portion that extends from the weight portion, a width of the arm portion in a second direction perpendicular to the first direction is smaller than a width of the weight portion in the second direction; and an arm root portion that is located between the arm portion and the base portion, a width of the arm root portion in the second direction gradually increasing toward the base portion, the first surface of the resonating arm is coplanar along an entirety of the weight portion, the arm portion and the arm root portion, and a percentage of a length of the weight portion in the first direction to a length of the resonating arm in the first direction is equal to or more than 35% and equal to or less than 41%.