An acoustic resonator includes: a substrate; a resonant region including a first electrode, a piezoelectric layer, and a second electrode disposed on the substrate, and a reflective layer disposed along a periphery of the resonant region; and a connection electrode extending from the second electrode. The reflective layer includes a second section disposed between the resonant region and the connection electrode, and a first section, and a cross-sectional area of the first section is different than a cross-sectional area of the second section.