A bulk acoustic wave (BAW) resonator includes: a plurality of acoustic reflectors disposed in a substrate; a lower electrode disposed over the plurality of acoustic reflectors; a piezoelectric layer disposed over the lower electrode; and a plurality of upper electrodes, disposed over the piezoelectric layer. One of the plurality of upper electrodes is formed over a respective one of the plurality of acoustic reflectors. Each of the plurality of upper electrodes, the piezoelectric layer, the lower electrode, and each of the acoustic reflectors form an individual active area.