[en] Computer simulations in conjunction with TEM experiments have been used to test the different models usually adopted in the literature to explain the formation of ''End Of Range'' (EOR) defects which appear after annealing of preamorphized silicon layers. Only one survives careful experimental investigations involving Si⁺, Ge⁺, Sn⁺ amorphization at RT and LNT. The ''excess-interstitial'' model appears relevant at least for a semi-quantitative explanation of the source of point-defects which after recombination and agglomeration, lead to the formation of these defects. This model may be used for the numerical optimization of conditions for the production of high performances ultrashallow junctions