Actuator, liquid discharge head, liquid discharge apparatus, and method of manufacturing actuator

An actuator comprising:

• a substrate having a void space having a first width, defined by opposed inner walls, in a width direction;
• a vibration film disposed over the substrate in a lamination direction perpendicular to the width direction, the vibration film serving as a part of a wall of the void space;
• and
• a piezoelectric element disposed over the vibration film in the lamination direction, the piezoelectric element opposed to the void space of the substrate via the vibration film,
• wherein the piezoelectric element has a second width smaller than the first width in the width direction,
• the piezoelectric element has outer ends, defining the second width, within the opposed inner walls of the void space in the width direction,
• the void space has a circular shape, having a first area, in a plane of the substrate, and
• the piezoelectric element has a circular shape, having a second area smaller than the first area, in the plane of the substrate.