High Quality Content by WIKIPEDIA articles! In semiconductor fabrication, a resist is a thin layer used to transfer a circuit pattern to the semiconductor substrate which it is deposited upon. A resist can be patterned via lithography to form a (sub)micrometer-scale, temporary mask that protects selected areas of the underlying substrate during subsequent processing steps. The material used to prepare said thin layer is typically a viscous solution. Resists are generally proprietary mixtures of a polymer or its precursor and other small molecules (e.g. photoacid generators) that have been specially formulated for a given lithography technology. Resists used during photolithography are called photoresists.