Phosphorus diffusion in a wide range of oxidation rate was investigated. Based on the experimental data, a new physical model for oxidation rate dependence of oxidation enhanced diffusion is proposed, in which self-interstitial concentration at the Si/SiO 2 interface is closely related to the oxidation reaction kinetics. Two dimensional (2-D) simulations for dopant diffusion in submicron LOCOS structures demonstrate the validity of the new boundary condition through the comparison with the experimental data.