Pattern data creating method, pattern data creating program, and semiconductor device manufacturing method

A pattern data creating method according to an embodiment of the present invention comprises: extracting marginal error patterns using a first result obtained by applying process simulation to mask pattern data based on an evaluation target cell pattern, applying the process simulation to mask pattern data based on an evaluation target cell pattern with peripheral environment pattern created by arranging a peripheral environment pattern in the marginal error patterns such that a second result obtained by creating mask pattern data and applying the process simulation to the mask pattern data is more deteriorated than the first result, and correcting the evaluation target cell pattern or the mask pattern data based on the evaluation target cell pattern when there is a fatal error.