The growth kinetics of Si dots grown on 6H-SiC(0001) by molecular beam epitaxy were studied in real time by reflection high-energy electron diffraction. The critical thickness for the Stranski–Krastanov growth mode transition was found to be kinetically delayed leading to a gradual decrease of this thickness with increasing temperature(T).AtT<625 °Cand coverages below the critical thickness, a post-deposition evolution of dots is clearly established. The dot growth process is, under these conditions, mainly determined by the mass transfer out of the two-dimensional layer towards the Si dots. The dots grown on top of a 1 monolayer (ML) thick wetting layer are quantum sized with typical dimensions of 5–6 nm in height and 20–30 nm in diameter after a long post-deposition evolution times at 2–3 ML coverages. Above 625 °C and coverages above the critical thickness, the dot growth is only determined by surface-diffusion kinetics resulting in the growth of larger dots. ©1997 American Institute of Physics.