| 摘要 |
PURPOSE:To form the semiconductor device having a sufficient withstand voltage even if a plane size of an element isolation region is reduced by using the non-oxidizable film, which is a masking material for forming an oxide film, as the mask for etching the oxide film and a substrate after forming the oxide film by selective oxidation. CONSTITUTION:After forming a thick oxide film 16 by thermal oxidation using a silicon nitride film 14 and an oxide film 15 as a mask, the thick oxide film 16 and a substrate 11 is etched to a predetermined depth by using the silicon nitride film 14 and the oxide film 15 for a mask as they are. A CVD SiO2 film 18 is deposited over the entire surface so as to fill an opening 17 followed by etching to define an element isolation region 19 composed of the oxide film 16 and the residual CVD SiO2 film 18. Even if a plane size of the element isolation region 19 is reduced, a distance between diffusion layers can be kept long practically and a decline of a punch-through withstand voltage can be prevented. |
