We have made a study for determining the silicon self‐interstitial diffusivity, their equilibrium concentration and their recombination velocity at SiO2/Si and Si3N4/Si interfaces in float zone and Czochralski silicon wafers. The experiments were based on monitoring the stacking fault growth/reduction kinetics at the front surface of a silicon membrane with a SiO2 or Si3N4 thin layer on top, under constant interstitial generation, by means of an oxinitridation process, at the other side of the membrane. We show that under these experimental conditions, the analysis and interpretation of the results is direct because the transport equation can be solved in a simple manner. We have achieved a very good agreement between the experimental results and the calculations made with the model and we have been able to determine values for the interstitial diffusivity, the equilibrium concentration and the recombination velocity at the SiO2/Si and Si3N4/Si interfaces.