A thermally stable Cu/W/Si contact system using Cu(111) and W(110) films with preferred orientations has been developed. The application of the W diffusion barrier with the [110] preferred orientation effectively suppresses the grain boundary diffusion of Si as well as the fast diffusion of Cu through the barrier due to annealing, resulting in raised silicidation temperatures above 670 degrees C and an effective suppression of Cu diffusion. The contact system tolerates annealing at 690 degrees C for 1 h, at which the W layer also stands as an effective barrier, although the W barrier is uniformly consumed by the silicidation reaction at the W/Si interface.