The work function of hafnium (Hf) was modified by nitrogen (N) in dc reactive sputtering. The resistivity of the HfNx thin film is sufficiently low up to the N-2 flow ratio of 10%. In addition, the work function is tuned from conduction band (4.1 eV) to midgap (4.55 eV) with increasing N-2 flow ratio. From the X-ray diffraction data, the HfN(200) peak can be observed from the samples which exceed the 8% N-2 flow ratio, which is responsible for the work function increase of the HfNx film. (c) 2006 The Electrochemical Society.