This article presents experimental and computational studies of a phase shifting photolithographic technique that uses binary elastomeric phase masks in conformal contact with layers of photoresist. The work incorporates optimized masks formed by casting and curing prepolymers to the elastomer poly(dimethylsiloxane) against anisotropically etched structures of single crystal silicon on SiO2/Si. Scanning optical microscopy and full-vector finite element computations reveal the important near field and proximity optical effects. Representative structures fabricated with this technique, including several that exploit subtle features in the intensity distributions, illustrate some of the capabilities. (c) 2006 American Vacuum Society.