Method for fabricating thermally stable contacts

In order to provide a thermally stable diffusion barrier for a contact, a layer of titanium (11) is formed on the patterned substrate (10). A layer of tungsten nitride (12) is formed on the titanium layer (11). After an annealing step, an interfacial layer (11') and a layer of titanium nitride (12') are formed between the substrate (10) and a tungsten layer (13'). These layers provide a diffusion barrier which is more thermally stable than a titanium nitride layer applied directly on the substrate and which permits the formation of a contact structures that can withstand subsequent high temperature steps.