A method for generating mask data that is used for a method of manufacturing semiconductor devices is provided. The semiconductor device includes wiring layers disposed in a specified pattern on a base and stress relieving layers disposed in a specified pattern over the base. The method for generating mask data comprises a step of forming resized patterns 130 by resizing wiring layer patterns 120 with a positive (+) resizing amount, a step of deleting, among the resized patterns 130, resized patterns having portions that mutually overlap, and a step of forming stress relieving layer patterns having a specified width outside the resized patterns.