Methods of forming a pattern using negative-type photoresist compositions

A method of forming a pattern, the method comprising:

• forming a lower resist film;
• forming an upper resist film on the lower resist film by coating a photoresist composition thereon, the photoresist composition including a polymer, a photoacid generator, and a solvent, and the polymer including an alkoxysilyl group as a side chain and being cross-linkable by an acid to be insoluble in a developer;
• curing a first portion of the upper resist film by exposing the first portion to light, the exposed first portion being cured by a cross-linking reaction of the alkoxysily groups therein;
• providing a developer to the upper resist film to remove a second portion of the upper resist film that is not exposed to light, thereby forming a upper resist pattern on the lower resist film;
• and
• partially removing the lower resist film using the upper resist pattern as an etching mask to form a lower resist pattern, the lower and upper resist patterns forming a bilayer resist pattern structure on the substrate.