Low temperature microwave plasma oxidation of UHV CVD grown partially strain compensated Si1-x-yGexCy (Ge/C = 20:1 and 40:1) with and without a Si cap layer is reported. The electrical properties of grown oxides have been characterized using C-V, G-V, J-E and constant current stressing of metal-oxide-semiconductor capacitors. Fixed oxide charge density and mid-gap interface trap density are found to be 2.9 x 10(11) cm(-2) and 8.8 x 10(11) cm(-2)/eV, respectively, for directly oxidized Si0.79Ge0.2Co0.01 films. The oxide on samples with C concentration of 0.5% exhibits hole trapping, whereas electron trapping is observed for oxides on alloys containing 1.0% carbon.