1. A resonator comprising:
an interdigital transducer electrode, being disposed on a piezoelectric thin film;
a resonance part, being held on a substrate through an air gap;
a supporting part, supporting the resonance part; and
two beam parts, connecting the resonance part to the supporting part at both ends of the resonance part,
wherein, the air gap forms a level difference at the supporting part, or
each beam part includes a thin beam part and an extended beam part, wherein the extended beam part is disposed where the air
gap forms the level difference.