In this work, a simple technique was proposed to fabricate germanium nanocrystal charge-trapping capacitors by an only one-step oxidation procedure on polycrystalline-SiGe (poly-SiGe) with different di-silane (Si2H6) and GeH4 gas ratio mixtures. This one-step oxidation method can directly result in the top-control oxide layer via the oxidation of amorphous-Si film and the formation of Ge nanocrystals from the poly-SiGe film at the same time. For the charge-trapping capacitor with a high Ge percentage, a 12 V memory window was achieved, and Ge nanocrystals were gathered to form a continuous poly-Ge layer from the TEM pictures. Another charge-trapping capacitor with a low Ge percentage, a 4 V memory window, was also achieved, and the Ge nanocrystals became separated (cracked) and disordered. Furthermore, a single spherical and isolated Ge nanocrystal was also found at a diameter of about 6 nm. (C) 2008 Elsevier B. V. All rights reserved.