We have synthesized Si Nps rich submicron area within a thin SiO2 layer using a new method called “stencil-masked ion implantation”. It consists in implanting silicon ions at ultra-low energy through windows (from 50nm to 2μm) opened in a stencil mask containing. After thermal annealing the implanted regions perfectly mimic the mask geometry. Energy-filtered transmission electron microscopy images and PL measurement reveal that smaller nanocrystals are formed near the edges of the implanted areas due to a dose edge effect.