This invention relates to a structure for fixing phase effects on EUV mask which contains a repeating pattern with an assist feature, or a pattern with two different sized features in close proximity. The EUV mask with the repeating pattern is capable of printing a group of trenches on a photoresist layer. The invention also relates to a method of fabricating an EUV mask for fixing phase effects. The EUV mask contains an absorber layer over the multilayer reflector, and the absorber layer is patterned to form a mask pattern which contains absorptive regions and reflective regions. The absorber is in the absorptive regions, and a phase shifter is deposited at least in the whole reflective regions of the mask pattern to a thickness capable of correcting phase effects. The phase shifter has an index of refraction value is about equal to or less than that of the absorber. The thickness of the phase shifter is determined by simulation.