Ultrasonic transducer, ultrasonic probe and method for fabricating the same

摘要

In an ultrasonic transducer including a gap between an upper electrode 18 and a lower electrode 14 on a silicon substrate 11, it is made possible to reduce or adjust warpage of an above-gap membrane vibrated by electrostatic actuation due to internal stress. A fourth insulating film 19 and a fifth insulating film 20 of films positioned above the gap 16 which is a cavity required for transmitting and receiving ultrasonic are respectively a silicon oxide film for compression stress and a silicon nitride film for tensile stress. Therefore, compression stress and tensile stress cancel each other, so that warpage of the above-gap membrane is reduced. An amount of warpage can be adjusted by adjusting a film thickness of the fourth insulating film 19 and a film thickness of the fifth insulating film 20.