Patent ID: 8258676

Claim:
A method for manufacturing a crystal device having a crystal plate that includes a base and a vibrating prong including at least a first vibrating prong and a second vibrating prong protruding from said base, the method comprising the steps of: forming a mask layer having corrosion resistance and a resist layer made of a photosensitive material on top thereof on each of two plane surfaces of a crystal substrate; exposing the resist layer formed on a first of the two plane surfaces of said crystal substrate to radiation through a first mask on which a first mask pattern is drawn, and exposing the resist layer formed on a second of the two plane surfaces of said crystal substrate to radiation through a second mask on which a second mask pattern is drawn that differs in shape from said first mask pattern, wherein said first and second mask patterns each have a crotch portion defined by a line that originates from a tip of said first vibrating prong, passes through a root of said first vibrating prong and through a root of said second vibrating prong, and leads to a tip of said second vibrating prong, and an angle of a bend contained in the crotch portion of said first mask pattern is different from an angle of a bend contained in the crotch portion of said second mask pattern; forming a first resist layer pattern by patterning the resist layer on the first plane surface of said crystal substrate into a shape corresponding to said first mask pattern, and forming a second resist layer pattern by patterning the resist layer on the second plane surface of said crystal substrate into a shape corresponding to said second mask pattern; forming a first mask layer pattern by patterning the mask layer on the first plane surface of said crystal substrate into the shape corresponding to said first mask pattern, and forming a second mask layer pattern by patterning the mask layer on the second plane surface of said crystal substrate into the shape corresponding to said second mask pattern; and forming said crystal plate having a first major face and a second major face on said crystal plate by etching said crystal substrate through said first mask layer pattern and said second mask layer pattern, wherein said first major face contains a portion of said base, a portion of said first vibrating prong and a portion of said second vibrating prong within a single plane, and said second major face contains another portion of said base, another portion of said first vibrating prong and another portion of said second vibrating prong within a single plane and wherein the crotch portion of said first major face and the crotch portion of said second major face have different outer shapes.