Patent ID: 7564177

Claim:
A crystal unit, comprising: a first crystal plate in which a vibration member with excitation electrodes provided thereon links to an outer circumferential frame portion, and a pair of extending electrodes extends from the excitation electrodes to the frame portion; and a second and third crystal plates which have a concave portion in an area opposite to the vibration member and whose open end surfaces are joined by direct bonding to both principal surfaces of the frame portion in the first crystal plate, wherein the extending electrodes are extended to an outer surface of at least one of the second and third crystal plates via electrode through-holes formed of via-holes provided in the frame portion, and electrically connected to external terminals formed on the outer surface, and wherein the electrode through-hole in the frame portion includes: a first electrode through-hole penetrating through the frame portion from the principal surface of the frame portion where the extending electrode extends; and a second electrode through-hole provided in at least one of the second and third crystal plates.