High-temperature electrostatic transducers and fabrication method

A high temperature micromachined ultrasonic transducer (HTCMUT) comprising:

• a. a silicon on insulator (SOI) substrate, wherein said SOI substrate comprises a doped first silicon layer and a first insulating layer;
• b. a doped second silicon layer, wherein said first insulating layer is disposed between said first silicon layer and said second silicon layer;
• c. a cavity in said first silicon layer, wherein a cross section of said cavity comprises a horizontal cavity portion on top of vertical cavity portions disposed at each end of said horizontal cavity portion, wherein said vertical cavity portion spans from said first insulating layer through said first silicon layer, wherein a portion of said first silicon layer is isolated by said first insulating layer and said cavity;
• d. a membrane layer, wherein said membrane layer is disposed on said first silicon layer top surface, wherein said membrane layer spans across said cavity;
• and
• e. a bottom electrode, wherein said bottom electrode is disposed on a bottom surface of said second silicon layer.