Resonator and filter using the same

A filter comprising two or more acoustic resonators, wherein each of the acoustic resonators comprises:

• a substrate;
• a resonator film which is supported above the main surface of the substrate and includes a piezoelectric film and a pair of a top electrode and a bottom electrode which are formed on part of the top surface and part of the bottom surface of the piezoelectric film, respectively, to face each other via the piezoelectric film;
• and
• a support which is formed on the main surface of the substrate to support the resonator film from below, the support being so formed that a resonance cavity is provided in part of a region between the substrate and the resonator film below at least a portion of part of the resonator film where the top electrode and the bottom electrode coincide with each other and an isolation cavity is provided in other part of said region where the support and the resonance cavity do not exist.