Air-gap type film bulk acoustic resonator

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

• a substrate which comprises an air gap portion having a substrate cavity formed in a top surface;
• a lower electrode formed on the substrate and extending beyond opposing sides of the air gap portion in the substrate;
• a piezoelectric layer which is formed on the lower electrode and has one side forming an edge portion in the vicinity of a virtual edge according to vertical projection of the air gap portion;
• an upper electrode formed on the piezoelectric layer;
• a first electrode frame which comprises an open ring structure in plane, the open ring structure surrounding a part of a periphery of the piezoelectric layer on the lower electrode;
• and
• a second electrode frame positioned on the upper electrode and adjacent to an open portion of the open ring structure, wherein a distance between the first electrode frame and the second electrode frame is equal to a distance between the opposing sides of the air gap portion in the substrate.