An extreme ultraviolet (EUV) mask comprises a substrate, a first reflective layer above a surface of the substrate, and a second reflective layer over the first reflective layer. The second reflective layer has various openings that define a first state and a second state. The first state includes the first reflective layer and is free of the second reflective layer. The second state includes both the first and second reflective layers. The first state has a first reflection coefficient and a first reflectivity. The second state has a second reflection coefficient and a second reflectivity. A phase difference between the first and second reflection coefficients is about 180 degrees.