The embedded Si structure formed by pattern-dependent oxidation (PADOX) in single-electron device (SED) is analyzed by novel microscopic methods using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The surface charge imaging SEM reveals the outline of the embedded Si nanowire of the electrically-measured SED. The size of the wire in the device is small enough to make a potential barrier caused by the quantum mechanical size effect. The result of the Si height in the oxidized structure estimated by AFM indicates that the huge stress induced by oxidation is applied to the narrow Si wire. The experimental results support the theoretical model of the SED fabricated by PADOX that the potential profile responsible for the SED operation is produced by two effects, the quantum mechanical size effect and the strain-induced bandgap reduction. (C) 2002 Elsevier Science B.V. All rights reserved.