PURPOSE: To offset the strain of a mask substantially and to form the mask in a desired shape by a method wherein, when an X-ray absorber film is patterned to a desired mask shape, the strain of the mask which is caused due to a change in the distribution of a stress is simulated and a patterning operation is performed by using a pattern which is deformed in the opposite direction so as to compensate the strain of the mask.

CONSTITUTION: The surface of an X-ray absorber 3 is coated with an electron- beam resist film. A mask pattern incorporating a strain pattern whose phase is opposite to that of a mask-strain estimation value obtained by a simulation is exposed on the electron-beam resist film by means of an electron-beam lithography apparatus. Then, a reactive ion etching operation is performed by making use of the resist film as a mask; the X-ray absorber 3 is patterned. A chip region 8 which has been etched selectively is deformed by a change in the distribution of the internal stress. When the mask of the electron-beam resist film is removed, it is possible to form a mask, for X-ray exposure, in which a selective X-ray transmission region has been formed. At this time, the pattern is deformed in an exposure operation, and the mask can be formed in a desired shape.