Piezoelectric device for ultrasonic sensor

A piezoelectric device for an ultrasonic sensor comprising:

• a substrate with a cavity;
• a vibrating plate which is provided on the substrate so as to block an opening surface of the cavity;
• a piezoelectric element which is provided on a surface of the vibrating plate opposite to the cavity, including a first electrode, a piezoelectric layer which is provided on the first electrode, and a second electrode which is provided on the piezoelectric layer,
• wherein the second electrode has a laminated structure including a platinum layer and a first iridium layer,
• the platinum layer is in contact with the piezoelectric layer,
• if it is assumed that two directions which are parallel to a surface of the substrate and mutually perpendicular are defined as an X direction and a Y direction, the first iridium layer is extended to an outside of the piezoelectric element and the cavity at least in the X direction on an X-Y plane view,
• a second iridium layer is extended to the outside of the piezoelectric element and the cavity in the Y direction on the X-Y plane view, and
• the second iridium layer is separated from the first iridium layer, on the piezoelectric layer.