Patent ID: 7887163

Claim:
A piezoelectric actuator, comprising: a diaphragm made of silicon; an insulating layer formed on a front surface of the diaphragm; a plurality of individual electrodes formed on a surface of the insulating layer; a plurality of piezoelectric bodies formed respectively on surfaces of the plurality of individual electrodes; and a plurality of common electrodes which are respectively arranged across the plurality of piezoelectric bodies from the plurality of individual electrodes, wherein the plurality of piezoelectric bodies are polarized in a direction from the individual electrodes toward the plurality of common electrodes; the insulating layer formed on the front surface of the diaphragm is a first silicon oxide film; a second silicon oxide film is formed on a rear surface of the diaphragm; and taking a thickness of the first silicon oxide film to be A (μm), taking a thickness of the second silicon oxide film to be B (μm), and taking a thickness of the diaphragm to be C (μm), all of following conditions are satisfied: 0.2≦A≦5, 0.2≦B≦5, 0.2≦( B/A )≦5, and 2≦C≦20.