A method for fabricating an FBAR device includes (a) preparing a substrate; (b) forming an insulating layer on the substrate; (c) forming a sacrificial layer on the insulating layer; (d) forming a plurality of sacrificial regions for forming air-gaps by selectively removing the sacrificial layer; (e) forming a membrane support layer on the insulating layer with the selectively removed sacrificial layer; (f) forming a membrane layer on the sacrificial regions and the membrane support layer; (g) forming a plurality of active regions on the sacrificial regions of the membrane layer so that a thickness of the active region corresponding to a series resonator differs from a thickness of the active region corresponding to a shunt resonator of the FBAR; (h) forming lower electrodes on the membrane layer including the active regions; (i) forming a piezoelectric layer on the lower electrodes; (j) forming upper electrodes on the piezoelectric layer; and (k) forming the air-gaps by removing the sacrificial regions.