The aim of this work is to compare the isothermal crystallization kinetics in stoichiometric Ge:Sb:Te as well as in un-doped and Ge doped Sb:Te eutectic films. Experimental results have shown a different crystallization mechanism in the investigated films. In Ge2Sb2Te5 and Ge1Sb2Te4 films the analysis of the kinetic results showed that at the beginning of crystallisation a metastable phase appeared with the Ge1Sb4Te7 composition, this is followed by the nucleation and growth of the stable fcc phase up to full crystallization. In contrast Ge4Sb1Te5 films show diffusion control growing from small dimension grains with decreasing nucleation rate. Sb:Te eutectic films doped by Ge have shown that the addition of Ge increased the effective activation energy of crystallization, but the mechanism of crystallization (diffusion-controlled growth of particles of appreciable initial volume) did not depend on Ge concentration.