Ultrafine patterns with dimensions smaller than the chemical and optical limits of lithography are formed by superimposing two photoresist patterns using a double exposure technique. Embodiments include forming a first resist pattern over a target layer to be patterned, forming a protective cover layer over the first resist pattern, forming a second resist pattern on the cover layer superimposed over the first resist pattern while the cover layer protects the first resist pattern, selectively etching the cover layer with high selectivity with respect to the first and second resist patterns leaving an ultrafine target pattern defined by the first and second resist patterns, and etching the underlying target layer using the superimposed first and second resist patterns as a mask.