A method for fabricating a film bulk acoustic resonator (FBAR) structure includes: sequentially forming a top electrode material layer, a piezoelectric layer, and a bottom electrode material layer on a substrate; patterning the bottom electrode material layer to form a bottom electrode; forming a sacrificial layer above the bottom electrode; bonding a bottom cap wafer onto the sacrificial layer; removing the substrate; patterning the top electrode material layer to form a top electrode; and removing a portion of the sacrificial layer to form a lower cavity.