Copper diffusion barrier performance of titanium nitride films was enhanced by formation of a ternary Ti-Si-N layer. The TiSiN films are prepared by chemical vapor deposition (CVD) using a metallorganic precursor (MOCVD-TiN) by thermal decomposition of tetrakis(dimethylamino)titanium (TDMAT). The deposition is followed by plasma treatment with a gas mixture of nitrogen and hydrogen in order to reduce the resistivity of the films. Finally, the films are in situ exposed to silane. This leads to the formation of a Si-N bond layer in the TiSiN film. The process delivers a film with conformal step coverage and low resistivity with improved barrier performance for advanced Cu metallization. The barrier performance as a function of the N2H2 plasma treatment and/or the SiH4 exposure is explained by the microstructural, compositional, and chemical changes in the films.