PURPOSE: A semiconductor device manufacturing method is provided to calculate an actual projection influence pattern based on areas of overlapped shots, thereby improving accuracy of a photo mask by correcting an overlapped pattern. CONSTITUTION: Broken shots which are not overlapped with each other are determined based on a final pattern(S110). Overlapped shots are determined based on the final pattern(S120). Area difference data is generated by comparing areas of the overlapped shots and the broken shots(S130). A projection influence pattern is calculated based on the area difference data(S140). The overlapped shots are corrected based on the projection influence pattern(S150).
