A fabricating method of a customized mask includes forming first patterns in a mold structure, forming second patterns in the mold structure using initial masks, the mold structure having the first patterns formed therein, measuring overlap failure between the first patterns and the second patterns, and fabricating customized masks by compensating for pattern positions of the initial masks based on the measuring results, wherein compensating for the pattern positions of the initial masks includes shifting positions of at least some patterns of the initial masks according to shift directions and sizes of at least some of the first patterns.