Thin films of W were grown using the low pressure chemical-vapour deposition technique in WF6/SiH4 flow on a TiN layer obtained by annealing in nitrogen atmosphere Ti films for different times. The investigation of W nucleation was followed by Atomic Force Microscopy in air. The Atomic Force images taken after fixed time of exposure of the TiN layer to the WF6/SiH4 flow show, on the surface of the W films, the presence of columnar structures only when the TiN films were obtained with forming times below 100 minutes. To investigate this effect X-ray Photoelectron Spectroscopy depth profile and X-Ray Diffraction measurements were performed on the obtained W/TiN films. The results show the deeper penetration of the nitrogen into the titanium layer with the longer forming time and a non stoichiometric composition of TiN interfacial layer which strongly influences the W nucleation.