A piezoelectric micromachined ultrasonic transducer comprising a
substrate and a first dielectric film formed on the substrate. An
opening having a sidewall is formed through the substrate and first
dielectric film. A bottom electrode is formed on the first
dielectric film spanning the opening. A piezoelectric element is
formed on the bottom electrode. A second dielectric film surrounds
the piezoelectric element. A conformal insulating film is formed on
the sidewall of the opening. A conformal conductive film is formed
in contact with the bottom electrode and on the sidewall of the
opening, wherein an open cavity is maintained in the opening. A top
electrode is formed in contact with the piezoelectric element.
