an improved manufacturing process and an improved device made by the process for retarding diffusion of implanted dopants during subsequent high - temperature processing . a layer of an electrically inactive species is implanted well below the active dopant layers , and the excess interstitials due to damage from the electrically inactive species layer form a retarding gradient which opposes dopant diffusion . using this process , shallow source - drain junctions can be achieved , and lateral encroachment of ldd implants under the gate can be minimized .