In addition to redistribution of the dopant, another oxide layer is grown which may act as a mask for the further process.

If a dopant is diffused at temperature T₁ for time t₁ and then is diffused at temperature T₂ for time t₂ etc. the total effective Dt is given by the sum of all the individual Dt products.

Some of the Dt steps may be negligible in a process. The Gaussian solution only holds if the Dt used to introduce the dopant is small compared with the final Dt for the drive-in i.e. if an initial delta function approximation is reasonable.