The thermal oxide growth process on Si is quite important to
fabricate any Si-based devices, even for future nano-devices. The
process is generally thought to be constituted by two atomic processes;
the oxygen diffusion through the oxide layer and the interfacial
reaction between oxygen and substrate Si. We have studied the barrier
height of the interfacial reaction from first-principles calculation,
and found that the height is quite lower than that estimated from
experiments. This suggests that the general understanding is too
simple. We propose to include the interfacial Si emission process for
the third process constituting the Si oxidation based on our
first-principles calculations and reaction-diffusion theoretical
studies. Our experimental efforts to clarify this Si emission process
are also introduced.