Patent ID: 6906451

Claim:
A piezoelectric resonator comprising: a substrate; and a vibration portion provided on the substrate, the vibration portion including a thin film portion in which top and bottom surfaces of the thin film portion includes at least one layer of piezoelectric thin film sandwiched between at least a pair of upper and lower electrodes facing each other in a thickness direction of the thin film portion; wherein first and second insulation films arranged between the substrate and the vibration portion; and a temperature coefficient of resonant frequency of one of the first insulation film, the second insulation film, and the piezoelectric thin film and temperature coefficients of resonant frequencies of the others of the first insulation film, the second insulation film, and the piezoelectric thin film have opposite signs; the arithmetic average surface roughness of the lower electrode is about 2.5 nm or less; and one of the first and second insulation films primarily comprises Al 2 O 3 , and the Al 2 O 3 includes an oxygen defect.