A bulk acoustic wave filter device includes a substrate, a lower electrode on the substrate, a piezoelectric layer covering at least a portion of the lower electrode, and an upper electrode covering at least a portion of the piezoelectric layer. The upper electrode has a density reduction layer disposed on at least a portion thereof, except a central portion of a resonance region of the bulk acoustic wave filter device that deforms and vibrates with the piezoelectric layer during activation of the piezoelectric layer. The density reduction layer has a density lower than a density of other portions of the upper electrode.