A thin-film piezoelectric
resonator including a substrate (6); a piezoelectric layer (2), a piezoelectric
resonator stack (12) with a top
electrode (10) and bottom
electrode (8), and a cavity (4). The piezoelectric
resonator stack (12) has a vibration region (40) where the top
electrode and bottom electrode overlap in the thickness direction, and the vibration region comprises a first vibration region, second vibration region, and third vibration region. When seen from the thickness direction, the first vibration region is present at the outermost side, the third vibration region is present at the innermost side and does not contact the first vibration region, and the second vibration region is interposed between the first vibration region and third vibration region. The
resonance frequency of the primary thickness-
longitudinal vibration of the vibration region (40) is f1 at the first vibration region, is f2 at the third vibration region, wherein f1 and f2 satisfy a relationship of f1<f2, and is a value between f1 and f2 at the second vibration region, said value increasing from the outer portion contacting the first vibration region to the inner portion contacting the third vibration region.