Patent ID: 7364275

Claim:
A piezoelectric actuator for providing a driving force to a pressure chamber of an ink-jet printhead for ejecting ink by deforming a vibration plate, the vibration plate forming an upper wall of the pressure chamber, the piezoelectric actuator comprising: a lower electrode formed on the vibration plate; a piezoelectric film having protruding portions, the piezoelectric film being formed on the lower electrode at a position that corresponds to the pressure chamber, the protruding portions protruding from upper sidewall portions of the piezoelectric film such that an upper portion of the piezoelectric film has a wider width than a lower portion of the piezoelectric film; and an upper electrode formed on the piezoelectric film for applying a voltage to the piezoelectric film, wherein a space exists between a lower surface of the protruding portions and an upper surface of the lower electrode.