The diffusion coefficient for silicon in thin SiC was estimated analyzing the layer growth kinetics during the carbonization with different growth techniques. The silicon diffusion was described by the classical parabolic law as well as by models, taking the peculiarities of the carbonization process into account. Generally, low diffusion coefficients correspond to layer with good morphological and structural properties. The best results were obtained by CVD, followed by GSMBE and finally by the techniques using elemental carbon as source for the carbonization.