Ultrasonic sensor and ultrasonic apparatus

An ultrasonic sensor comprising:

• a substrate having a first surface and a second surface in a front-back relationship with the first surface and having an opening portion penetrating from the first surface to the second surface;
• a vibrating plate provided on the first surface of the substrate and covering the opening portion;
• a piezoelectric element provided in a position overlapping with the opening portion in a plan view as seen from a direction from the first surface to the second surface in the vibrating plate;
• and
• a coupling electrode coupled to the piezoelectric element, extended from a position overlapping with the opening portion to a position not overlapping with the opening portion in the plan view, and having a line width smaller than a width of the piezoelectric element, wherein
• the piezoelectric element has an outline including a first line portion, a second line portion, and a corner portion coupling the first line portion and the second line portion in the plan view,
• when an intersection point of a first virtual line connecting a point of a center of gravity of the piezoelectric element and the corner portion with a virtual circle inscribed in the outline of the piezoelectric element is a first intersection point, an intersection point of a tangent line of the virtual circle at the first intersection point with the first line portion is a second intersection point, and an intersection point of the tangent line of the virtual circle at the first intersection point with the second line portion is a third intersection point, the coupling electrode is coupled to a corner portion within a range from the second intersection point through the corner portion to the third intersection point in the outline of the piezoelectric element.