TiN diffusion barriers have been widely used in submicron contact structures, due to its good adhesion (to SiO2, W, Al and Si) properties, low diffusivity (for Si, W and Al) and compatibility with TiSi2 processing. The purpose of this paper is to present the results of physical and electrical characterization of contact structures with a TiN barrier and W plugs. Two different barrier metal processes were compared, Viz: sputtered Ti followed by post RTN and Ti/TiN films followed by post RTA in the range of 600° to 800°C. The devices were thermal stressed at 450°C for 7 hrs after W plug formation and Al metallization. Ti/TiN films with post RTA are generally superior barrier layers than Ti films with post RTA as shown by electrical characterization of contact resistance and barrier integrity. The relationship between electrical properties and microstructure for the two different barrier structures is discussed. W/TiN and TiN/TiSi2 interface structures were characterized using high resolution TEM. TiSi2 was found to be epitaxially grown during RTA, under certain process conditions. The crystal structure of TiSi2 was determined from electron diffraction patterns.