Abstract: One inventive aspect relates to a phase shift mask suitable for lithographic processing of a device, to a method of making such a mask and to lithographic processing using such a mask. The phase shift mask is made taking into account the threshold or dose that will be used for lithographic processing using the mask. In this way, image imbalance will be reduced in a significant focus-exposure processing window. In one embodiment, evaluation of the image imbalance is performed taking into account the processing windows for the different edges of the features of the pattern.