In this paper, we present a study on the contribution of silicon nanocrystals to the electrical transport characteristics of large (100 mu m x 100 mu m) and small (100 nm X 100 nm) metal-oxide-semiconductor (MOS) capacitors at room temperature. A layer of silicon nanocrystals is synthesized within the oxide of these capacitors by ultra-low energy ion implantation and annealing. Several features including negative differential resistance (NDR), sharp current peaks and random telegraph signal (RTS) are demonstrated in the current-voltage and current-time characteristics of these capacitors. These features have been associated to charge storage in silicon nanocrystals and to the resulting Coulomb interaction between the stored charges and the tunneling current. Clear transition from a continuous response of large capacitors to a discrete response of small capacitors reveals the quantized nature of the charge storage phenomenon in these nanocrystalline dots. (c) 2005 Elsevier Ltd. All rights reserved.