A method for forming photoresist patterns, comprising the steps of: coating a photoresist containing a photosensitive acid generator 3 on a support 1 forming a silicon monomer layer 2 on the photoresist 2; exposing the monomer layer to light through a mask 4 to selectively polymerize the silicon monomer; removing the unexposed regions of the monomer layer and subjecting the remaining polymerized regions 5 to oxygen plasma to form silicon oxide layer 7 and imagewise exposing photoresist 3 to deep UV, X-ray or electron beams and developing to produce photoresist pattern 3 with said oxide layer 7 serving as a mask. Exposure of the photosensitive acid generator generates protons which trigger the polymerization of silicon monomers. The silicon oxide layer 7 subsequentially formed is not removed by typical developing solutions and serves as a mask to expose the photoresist film 3. <IMAGE>
