A piezoelectric thin-film resonator includes a lower electrode (43) formed on a substrate (41) to define a rounded dome-shaped cavity (46) between the lower electrode and the substrate, a piezoelectric film (44) provided on the lower electrode, and an upper electrode (45) provided on the piezoelectric film. A membrane region is an overlapping region of the lower electrode and the upper electrode interposing the piezoelectric film and a projected area of the cavity onto the substrate includes the membrane region.
