The chromium nitride thin layers have became more and more popular in the last decade because of their good physical, chemical and mechanical properties. The present study deals the morphological characterization of hard Cr-N and CrAlN thin layers deposited on silicon (100) substrates by physical vapour deposition (PVD). The effect of the annealing temperature on the adherence and the thermal stability of CrN layers are considered. SEM observations and EDS microanalyses were performed. Cr-N films, 1μm thick, were annealed for 1 hour at 600 to 1000°C under flux of nitrogen. These layers presented a good thermal stability at low temperatures. Moreover SEM observations showed that the CrN films had a low adhesion at high temperatures. In addition, after annealing at 700°C for 4 hours, CrAlN coating of 1μm thickness presents a better thermal stability than CrN coating but with lower adherence. The results given by SEM-EDS and XRD are compared.