Ultrasonic sensor and method for manufacturing ultrasonic sensor

An ultrasonic sensor comprising:

• a substrate having a first surface and a second surface at an opposite side from the first surface, the substrate having an opening penetrating the substrate from the first surface to the second surface;
• a vibration plate covering a first surface side of the opening;
• a plurality of piezoelectric elements provided at a surface of the vibration plate at an opposite side from the opening and each including a first electrode, a piezoelectric layer, and a second electrode which are stacked;
• and
• an elastic layer in contact with the vibration plate in the opening, wherein
• a direction in which the first electrode, the piezoelectric layer, and the second electrode are stacked is defined as a stacking direction, a portion in which the first electrode, the piezoelectric layer, and the second electrode overlap in a plan view seen from the stacking direction is defined as an active portion, and a plurality of active portions face the opening, and
• a thickness of the elastic layer is equal to or larger than half a thickness of the substrate and less than the thickness of the substrate, and the thickness of the elastic layer in each of the plurality of active portions is uniform when viewed from a direction orthogonal to the stacking direction.