PURPOSE: An overlay measurement method is provided to precisely measure the overlay between upper and lower patterns from a virtual image before performing a patterning process with respect to an upper film, thereby repairing the upper film without discarding a semiconductor substrate. CONSTITUTION: First information with respect to a first structure is acquired(ST130). A second auxiliary structure is arranged on the first structure(ST140). The first structure and second auxiliary structure are arranged(ST150). Second information with respect to the second auxiliary structure is acquired(ST160). Virtual information is acquired by synthesizing the first information and second information(ST170). A virtual overlay between the first structure and second structure is measured from the virtual information(ST180).
