Disclosed is an air-gap type film bulk acoustic resonator (FBAR) including a substrate including 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. Here, the piezoelectric layer includes a void portion having a piezoelectric cavity between the lower electrode and the upper electrode, and the void portion is formed below an edge portion corresponding to an end part of the upper electrode.