FBAR device includes a membrane supporting layer between a substrate and a membrane
layer, surrounding an air gap region. The membrane supporting layer support the
membrane layer to obtain a robust structure. The substrate has a first area and
a second area surrounding the first area. The membrane supporting layer is formed
on the second area of the substrate so as to form the air gap on the first area
of the substrate. The membrane layer is formed on the membrane supporting layer
and the air gap. A first electrode is formed on a portion of the membrane layer.
A piezoelectric layer is formed on a portion of the first electrode. A second electrode
is formed on a portion of the piezoelectric layer.
