Patent ID: 7348714

Claim:
A piezoelectric resonator comprising: a first electrode film formed on a substrate; a piezoelectric film formed on the first electrode film; a second electrode film formed on the piezoelectric film and obtaining, in collaboration with the first electrode film, a signal having a predetermined resonance frequency by a propagation of a bulk acoustic wave inside the piezoelectric film; and an oscillation energy confining film including a first acoustic film having a predetermined acoustic impedance and a second acoustic film having an acoustic impedance higher than the first acoustic film, and reflecting the bulk acoustic wave, the first acoustic film and the second acoustic film being alternately stacked on the second electrode film, and the first acoustic film being in contact with the second electrode film, wherein the resonance frequency of the second acoustic film is higher than the resonance frequency of the first acoustic film, wherein the oscillation energy confining film substantially eliminates loss of oscillation energy of the piezoelectric resonator, and wherein a thickness of at least one of the first acoustic film and the second acoustic film is selected to optimize a temperature characteristic and a Q-value of said resonator.