A CMUT transducer cell suitable for use in an ultrasonic CMUT transducer array has a membrane with a first electrode a substrate with a second electrode and a cavity between the membrane and the substrate. The CMUT is operated in a precollapsed state by biasing the membrane to a collapsed condition with the floor of the cavity and a lens is cast over the collapsed membrane. When the lens material has polymerized or is of a sufficient stiffness the bias voltage is removed and the lens material retains the membrane in the collapsed state.
