Complementary metal oxide semiconductor (CMOS) ultrasonic transducers and methods for forming the same

An apparatus, comprising:

• a semiconductor wafer having a complementary metal oxide semiconductor (CMOS) integrated circuit;
• an electrode;
• an insulating material having a cavity formed at least partially therein;
• a conductive layer contacting the insulating material, sealing the cavity and having a first side proximate the cavity and a second side distal the cavity, wherein the electrode, cavity, and conductive layer together define, at least in part, an ultrasonic transducer, with the cavity being between the electrode and the conductive layer;
• a conductive contact coupling the electrode to the CMOS integrated circuit;
• and
• a conductive plug embedded in the insulating material and terminating on the first side of the conductive layer proximate the cavity without extending through the conductive layer such that a surface of the conductive plug is bonded with the first side of the conductive layer, wherein the conductive plug electrically connects the conductive layer to the CMOS integrated circuit, and
• wherein the electrode and the conductive plug are electrically isolated from each other.