Metal–oxide–semiconductor structures with a Ge nanocrystal embedded in SiO2 films were fabricated by Ge+ ion implantation and subsequent high-temperature annealing. The Raman spectra indicate the evidence of self-assembled Ge nanocrystals in the SiO2 films. The Ge size and its density were estimated to 3–5 nm and 1×1012/cm2, respectively. Photoluminescence spectra showed a strong blue–violet band around 400 nm and a weak near-infrared band around 750 nm, respectively. The several implantation-induced deficient centers are believed to be responsible for the blue-light luminescence. Capacitance–voltage characteristics exhibit the flatband voltage shifts of 1.02 V after the electron injection into the SiO2/Ge/SiO2 potential well. An anomalous leakage current was clearly observed in the current–voltage characteristics. The precise simulation of quantum electron transport in the SiO2 film indicates that the anomalous conduction is originated from resonant tunneling in the SiO2/Ge/SiO2 double-well band structure. © 2001 American Institute of Physics.