The present invention relates to a process for forming a photoresist pattern by employing a silylation process, and particularly to a method for forming a photoresist pattern according to a top surface imaging (TSI) process using a photoresist composition comprising a cross-linker having a cross-linker monomer of the following Chemical Formula 1 or 2. The photoresist composition containing a polymer of the above cross-linker monomer is preferably used in a TSI process which has been optimized by controlling the conditions of each step, such as temperature and time, thereby obtaining an ultrafine pattern that can be more efficiently applied to a 4 G or 16 G DRAM semiconductor fabrication process: wherein, R1, R2, R3, R5, R6, R7, R, m and n are as defined in the specification attached hereto.