The effects of the oxidation of Si 1−x C x films (x=0.0125) on Si (100) substrates were evaluated. Epitaxial Si 1−x C x (x=0.0125) films were deposited by ultrahigh-vacuum chemical vapor deposition at 600°C. Oxidation at 800°C and 900°C under an O 2 ambient in a tube furnace resulted in a decrease in substitutional C concentration, due to the formation of interstitial carbon or β-SiC precipitation. Transmission electron microscopy analyses indicated that the formation of β-SiC on the Si 1−x C x layer occurred when the oxidation temperature exceeded 900°C. This indicates that relaxation of compressive stress in the depth direction occurred as the result of the formation of β-SiC. No evidence was found for the segregation of carbon at the top of the Si 1−x C x layers during the oxidation of the Si 1−x C x layer unlike the Ge pile up that occurs during the oxidation of Si 1−x Ge x layers.