A theoretical analysis is presented for the physical model of thermal oxidation proposed by Williams and Hayfield. A rate dL/dt proportional to exp [-(L/L-crit)(2)] is deduced herein for oxide film thickness L as a function of time t. The growth rate exponential falloff parameter is L-crit = root 2 epsilon kT/n(e)e(2), where n(e) is a uniform density of trapped electrons in the oxide, T is the Kelvin temperature, and the parameters epsilon, k, and e are the static dielectric constant of the oxide, Boltzmann's constant, and electronic charge magnitude, respectively. Numerical computations compare this rate law with the logarithmic growth law proposed in the original analysis. (c) 2006 The Electrochemical Society.