Argon doped epitaxial layers for inhibiting punchthrough within a semiconductor device

摘要

A fabrication process and transistor are described in which a transistor having decreased susceptibility to punchthrough and increased resistance to impurity diffusion is formed. One or more argon doped silicon epitaxial layers are formed superjacent a semiconductor substrate. In a preferred dual layer embodiment, a first argon doped silicon epi layer is grown over a substrate, and a second argon doped epi layer, preferably having an argon concentration less than that in the first epi layer, is formed over the first epi layer. A transistor is formed in an active region of a well having a channel laterally bounded by source/drain regions located exclusively in the second epi layer. The lighter argon doping of the second epi layer accommodates current flow in the channel while acting as a barrier to impurity outdiffusion and inhibiting punchthrough. The more heavily doped first epi layer serves primarily as a barrier to outdiffusion of impurities from the bulk substrate.