A crystal device that has stable vibration characteristics and that offers high reliability and high accuracy. The crystal device includes a first major face, which contains a portion of a base and a portion of a vibrating prong within a single plane, formed on the crystal plate, and a second major face, which contains another portion of the base and another portion of the vibrating prong within a single plane, formed on a crystal plate, wherein the first major face and the second major face have different outer shapes. The shapes of the first and second major faces can be produced by first forming mask layer patterns on a crystal substrate by exposure through different mask patterns and then etching the crystal substrate using the thus formed mask layer patterns.