Nitrogen doped silicon films have been deposited by low pressure chemical vapour deposition from disilane Si2H6 and ammonia NH3. Deposition kinetics is investigated, pointing out the influences of the deposition temperature, the total pressure and the gas flow rates. According to the Bruggeman theory, variations of the NH3/Si2H6 gaseous ratio allow for a wide range of the SiNx stoichiometry as well as a good control of the film nitrogen doping. The different behaviours of the nitrogen atom in silicon films are discussed and an overview of the nitrogen doped silicon physical properties (optical, mechanical and electrical) is proposed for the development of boron-doped polysilicon gates.