There is considerable interest in the use of phase shift masks as a route to extend the resolution, contrast, and depth‐of‐focus of lithographic tools beyond what is achievable with the normal chrome mask technology. In the attenuating phase shift mask, the chrome layer is replaced with a slightly transparent layer and the mask is etched so that light through the layer is 180° out of phase with light through clear regions. Thus, optical interference occurs which has the effect of increasing contrast at edges and of improving depth‐of‐focus. In this article, experiments of thin film materials designed to provide both the desired 180° phase shift and optical absorption in a single layer are described.