An ultrasonic transducer is formed by a plurality of cMUT cells, each comprising a charged diaphragm plate capacitively opposing an oppositely charged base plate. The diaphragm plate is distended toward the base plate by a bias charge. The base plate includes a central portion elevated toward the center of the diaphragm plate to cause the charge of the cell to be of maximum density at the moving center of the diaphragm plate. For harmonic operation the drive pulses applied to the cells are predistorted in consideration of the nonlinear operation of the device to reduce contamination of the transmit signal at the harmonic band. The cMUT cells can be fabricated by conventional semiconductor processes and hence integrated with ancillary transducer circuitry such as a bias charge regulator. The cMUT cells can also be fabricated by micro-stereolithography whereby the cells can be formed using a variety of polymers and other materials.
