We have investigated the effects of harder layers on the electrical characteristics of Ti-silicide/polycrystalline Si gates. Ti-Si-N films reactively sputtered using TiSi2.1 target and TiN film were used as barrier layers. We found that the increase in nitrogen content of Ti-Si-N films results in the formation of Si3N4 bonding and a small amount of TiN bonding. The effect of the Ti-Si-N barriers on Ti-silicide agglomeration and dopant loss into Ti-silicide is strongly influenced by the nitrogen content, indicating that larger amounts of Si3N4 in the Ti-Si-N film improved barrier performance. However, TiN films are more effective barriers. In addition, Ti-Si-N barriers show more degraded gate-oxide reliability than TiN barriers, which is attributed to the incorporation of Ti atoms into polycrystalline Si. It is conjectured that free Ti atoms not bonded with Si or N in the Ti-Si-N films act as a source of Ti incorporation. TiN barriers not only inhibit Ti diffusion from Ti-silicide, but also do not provide a source of Ti.