By using the SPring-8 beam line, we have studied the dependence of the chemical structure and uniformity of three kinds of approximately 1 nm-thick silicon oxide films formed by using atomic oxygen at 300degreesC on the oxidation process. Among the SiO2Si interfaces formed by several oxidation methods using atomic oxygen, the uniformity was strongly dependent on the oxidation process and the highest uniformity was obtained with the krypton-mixed oxygen plasma oxidation, while the abruptness of the compositional transition layer was weakly dependent on the oxidation process. (C) 2004 Elsevier B.V. All rights reserved.