Embodiments relate to a method of forming a 90 nm semiconductor device, including forming an isolation film within a semiconductor substrate in which a pMOS region and an nMOS region are defined. A first mask is formed to shield the nMOS region by using a DUV photoresist having a thickness of approximately 0.7 to 0.75 .mu.m. Ions are implanted into the pMOS region to form a p type well. A second mask is formed to shield the pMOS region by using a DUV photoresist having a thickness of approximately 0.7 to 0.75 .mu.m. Ions are implanted into the nMOS region to form an n type well. A gate oxide film and a gate is formed over the semiconductor substrate. A low-concentration impurity may be implanted by using the gate as a mask. An LDD region may be formed. A sidewall spacer may be formed over both sidewalls of the gate. A high-concentration impurity is implanted by using the sidewall spacer as a mask, forming a source/drain region.