A bulk acoustic wave resonator includes: a substrate; a resonant portion including a sequentially stacked first electrode, piezoelectric layer, and second electrode; a cavity defined between the substrate and the resonant portion; and a heat dissipation portion disposed in the cavity and supporting the resonant portion. The second electrode includes a first region and a second region having a thickness greater than a thickness of the first region, and the second region is disposed above the heat dissipation portion.