Patent ID: 7531943

Claim:
An acoustic resonator for vibrating at a predetermined frequency, comprising: a vibrating section including a piezoelectric element, an upper electrode formed on an upper surface of the piezoelectric element, and a lower electrode formed on a lower surface of the piezoelectric element; a substrate section with a cavity formed therein, the cavity having an opening with an area equal to or greater than a horizontal cross section of the vibrating section; and a support section formed between the vibrating section and the substrate section, wherein: the vibrating section is located on the support section at a position such that a vertical projection of the vibrating section onto the substrate section is accommodated within the opening of the cavity; and the vibrating section and the support section are shaped so that vertical thicknesses thereof are different from each other with a sum of the vertical thicknesses being equal to one wavelength of a resonant vibration frequency of the acoustic resonator, and are shaped so that an interface between the piezoelectric element and the lower electrode does not coincide with an antinode of the resonant vibration frequency of the acoustic resonator.