The use of TiN thin films as high temperature diffusion barrier layers for arsenic and boron was investigated. The TiN films are formed by reactive evaporation at room temperature and then annealed at a higher temperature. TiN and TiN/TiSi2 films are placed between heavily doped polycrystalline silicon films and single-crystal silicon substrates of opposite doping polarity for secondary ion mass spectrometry analysis and electrical measurements of Schottky and ohmic contacts respectively. The results indicate that TiN is a good diffusion barrier for arsenic at 900°C. The effectiveness of this property is degraded as the temperature exceeds 900°C and it becomes ineffective at 1000°C. TiN is a better diffusion barrier for boron than for arsenic. It allows limited diffusion of boron at temperatures of up to 1000°C. The TiN/TiSi2 composite forms good ohmic contacts when the substrates are heavily doped. The ohmic contacts can survive after annealing at temperatures of up to 1000°C. It also forms good Schottky contacts when the substrates are lightly doped. The Schottky contacts can survive after annealing at temperatures of up to 950°C in one case and of up to 1000°C in another case. © 1984.