A method for semiconductor fabrication includes forming mandrel patterns over a substrate using a first mask that defines the mandrel patterns, wherein the first mask includes at least four first patterns that are spaced from each other in a first direction, wherein each of the first patterns extends lengthwise in a second direction orthogonal to the first direction. The method further includes forming spacers on sidewalls of the mandrel patterns; removing the mandrel patterns, and performing a cut process using a second mask that includes at least four cut windows, each cut window in the second mask being an elongated shape extending lengthwise in the second direction and covering a side of one of the first patterns when the first and second masks are superimposed, the side extending in the second direction.