Air-gap type film bulk acoustic resonator

An air-gap type film bulk acoustic resonator (FBAR) comprising:

• a substrate comprising an air-gap portion with a top surface in which a substrate cavity is formed;
• a lower electrode formed above the substrate while surrounding the air-gap portion;
• a piezoelectric layer formed above the lower electrode;
• and
• an upper electrode formed above the piezoelectric layer corresponding to a virtual area formed according to a vertical projection of the air-gap portion,
• wherein the piezoelectric layer comprises a third void portion having a third piezoelectric cavity between the lower electrode and the upper electrode, and a fourth void portion having a fourth piezoelectric cavity formed to be spaced at a certain distance apart from the third void portion, and
• wherein the third void portion is formed below an edge portion corresponding to an end part of the upper electrode.