Patent ID: 6839946

Claim:
A method for fabricating a Thin Film Bulk Acoustic Wave Resonator (FBAR), comprising the steps of: STEP A: forming a sacrificial layer on a selected portion of a substrate, wherein the sacrificial layer comprises one of a metal and a polymer; STEP B: forming a bottom electrode layer on the sacrificial layer and on selected portions of the substrate; STEP C: forming a piezoelectric layer on a selected portion of the bottom electrode layer and on a selected portion of the substrate; STEP D: forming a top electrode layer on a selected portion of the piezoelectric layer; STEP E: removing the sacrificial layer to form an air gap beneath at least a portion of the bottom electrode layer; wherein STEP A is performed by the steps of STEP 1: depositing one of the metal and the polymer over the substrate; and STEP 2: patterning the deposited one of the metal and the polymer to form the sacrificial layer; wherein STEP E is performed by etching the sacrificial layer using a chemical that is not harmful to the piezoelectric layer; and wherein between the performances of STEPS D and E, a step is performed of: forming at least one via through at least one of the layers formed in STEPS B-D so that the sacrificial layer can be removed through the at least one via, thereby forming an RF resonator.