A resonator includes a vibration portion with a base and a plurality of vibration arms each having a fixed end and a free end with the fixed end being connected to the base. Each of the plurality of vibration arms includes a piezoelectric thin film and an electrode stacked on the piezoelectric thin film. Moreover, a width of each of the plurality of vibration arms increases from the fixed end toward the free end. In addition, a width of the electrode of each of the plurality of vibration arms increases from the fixed end towards the free end of the vibration arm.