A multi-layered piezoelectric device includes a plurality of piezoelectric portions and a plurality of electrodes electrically connected to the piezoelectric portions, that are formed in layers on a ceramic substrate. In an array sensor comprising a plurality of sensor elements, the two outermost sensor elements are alternately selected by a switch for use as a transmitting sensor, and the other sensor elements are selected in time division fashion as receiving sensors. A small via is drilled by laser drilling and plated filled with copper to be used as the connection between the circuits.