A tuneable film bulk acoustic resonator (FBAR) device. The FBAR device
includes a bottom electrode, a top electrode and a piezoelectric layer in
between the bottom electrode and the top electrode. The piezoelectric
layer has a first overlap with the bottom electrode, where the first
overlap is defined by a projection of the piezoelectric layer onto the
bottom electrode in a direction substantially perpendicular to a plane of
the bottom electrode. The FBAR device also includes a first dielectric
layer in between the piezoelectric layer and the bottom electrode and a
mechanism for reversibly varying an internal impedance of the device, so
as to tune a resonant frequency of the FBAR device.