Ultrathin (< 100 Angstrom) oxynitrides were grown on strained Si0.74Ge0.26/Si heterolayers by low energy plasma source nitrogen implantation followed by microwave plasma oxidation at a low temperature. Secondary ion mass spectroscopy analysis revealed the incorporation of nitrogen into the strained Si0.74Ge0.26/Si heterolayers, forming good quality oxynitride films upon plasma oxidation. Though the fixed oxide and interface charge densities are relatively high, grown films exhibit low leakage current and high breakdown field strength (6-9 MV/cm), indicating that the oxynitrides formed by plasma source nitrogen implantation are suitable for metal-oxide-semiconductor devices. (C) 2004 Elsevier Ltd. All rights reserved.