Patent ID: 7667374

Claim:
An ultrasonic transducer for transmitting and receiving ultrasonic comprising: a semiconductor substrate; a first insulating film provided on the semiconductor substrate, wherein the first insulating film comprises silicon oxide; a lower electrode provided on the first insulating film; a second insulating film provided on the lower electrode, wherein the second insulating film comprises silicon oxide; a gap provided above the second insulating film; a third insulating film provided on the gap, wherein the third insulating film comprises silicon oxide; an upper electrode provided above the third insulating film; a fourth insulating film provided above the upper electrode, wherein the fourth insulating film is a compression stress layer, the fourth insulating film comprising silicon oxide; and a fifth insulating film provided on the fourth insulating film, wherein the fifth insulating film is a tensile stress layer, wherein the third insulating film, the upper electrode, the fourth insulating film and the fifth insulating film above the gap comprise a vibratable membrane.