A bulk acoustic wave resonator includes a substrate, a first electrode, wherein a cavity is formed between the substrate and the first electrode, a piezoelectric layer disposed on the first electrode and overlapping at least a portion of the first electrode, a second electrode disposed on the piezoelectric layer and overlapping at least a portion of the piezoelectric layer, a passivation layer having at least a portion disposed on the second electrode and overlapping at least a portion of the second electrode, and a lower frame spaced apart from the substrate and having a portion of the cavity disposed therebetween. Any one of the second electrode and the passivation layer includes a protruding portion having a first thickness and an extended portion having a second thickness less than the first thickness, and an inner end of the lower frame and an end of the protruding portion are spaced apart horizontally.