A method of forming a pattern includes forming an underlayer on an etching target layer by a chemical vapor deposition (CVD) process, the underlayer including a silicon compound combined with a photoacid generator (PAG), forming a photoresist layer on the underlayer, irradiating extreme ultraviolet (EUV) light on the photoresist layer to form a photoresist pattern, and etching the etching target layer using the photoresist pattern as an etching mask.