Abstract TiN films were deposited by plasma chemical vapor deposition utilizing d.c. glow discharge onto metal substrates at 800 K from both gas mixtures of TiCl 4 -H 2 -N 2 and TiCl 4 -H 2 -NH 3 . Plasma diagnostic measurements were carried out using optical emission spectroscopy and quadrupole mass spectrometry. The dependence of TiN film properties and the plasma species on the plasma power input was investigated. TiN films of fine properties were found to form at low plasma power inputs with a higher deposition rate in the plasma of TiCl 4 -H 2 -NH 3 than in the plasma of TiCl 4 -H 2 -N 2 . The difference between the reactivity of N 2 and that of NH 3 in the plasma was examined and the reactive plasma species believed to play important roles in the TiN film formation reaction chain were identified.