Piezoelectric actuator, ultrasonic element, ultrasonic probe, ultrasonic device, and electronic device

A piezoelectric actuator, comprising:

• a substrate in which an opening is formed;
• a vibrating plate provided at the substrate and having a first surface configured to close the opening;
• a plurality of piezoelectric elements provided at a second surface correspondingly to the opening, the second surface being at an opposite side of the vibrating plate from the first surface;
• a suppressing portion provided correspondingly to the piezoelectric elements and configured to suppress vibration of the vibrating plate, and
• a plurality of walls sticking out into the opening from the first surface, wherein
• the piezoelectric elements include a first electrode, a piezoelectric layer, and a second electrode stacked in this order from a side of the second surface,
• when an active portion is a portion where the first electrode, the piezoelectric layer, and the second electrode overlap, each of the walls are provided between the active portions adjacent to each other in a plan view from a stacking direction, and
• a distance between the walls adjacent to each other is longer than a distance between the active portions adjacent to each other in a plane perpendicular to the stacking direction,
• wherein a distance between the walls adjacent to each other is at least twice a distance between suppressing portions adjacent to each other.