Semiconductor device

摘要

A dose of arsenic for an extension region in an NMOS transistor is in a range from 5x10¹⁴ to 2x10¹⁵ ions/cm² and preferably in a range from 1.1x10¹⁵ to 1.5x10¹⁵ ions/cm². Also, in addition to arsenic, a low concentration of phosphorus is doped into the extension region by ion implantation. Consequently, with a semiconductor device of the CMOS structure, it is possible to prevent unwanted creeping of silicide that occurs often in the shallow junction region depending on a concentration of an impurity having a low diffusion coefficient as represented by arsenic. Further, not only can the resistance in the shallow junction region be lowered, but also an amount of overlaps can be optimized in each transistor.