Film Bulk Acoustic Resonator (FBAR) is an acoustically isolated device consisting of a piezoelectric material sandwich between two electrodes.
FBAR devices using piezoelectric films with thicknesses ranging from several micrometres down to tenth of micrometres resonate in the frequency range of roughly 100 MHz to 10 GHz. Aluminium nitride and zinc oxide are two common piezoelectric materials used in FBARs.
Common applications of FBARs is radio frequency (RF) filters used in phones and other wireless applications. Filters are made from a network of resonators and are designed to remove unwanted frequencies from being transmitted whilst allowing specific frequencies to be recieved. These networks are usually in half-ladder, full-ladder, lattice or stacked topologies. FBARs can also be used in sensor applications in this case when a device is subject to some form of mechanical pressure its resonance frequency will shift.
3D FBAR Surface Deformation at Resonance