We investigated the physical and electrical properties of a W/WNx/poly-Si1-xGex gates stack with a post-thermal process for use in the high performance complementary metal oxide semiconductor field effect transistor. Under the same annealing conditions, the crystallinity of the W films degraded, and the sheet resistance of the W/WNx/poly-Si1-xGex films increased with increasing Ge content of the poly-Si1-xGex films. These results are attributed to the increase in surface roughness of the poly-Si1-xGex films, which suppressed grain growth in the W films as the Ge content of poly Si1-xGex increased. After high temperature annealing, the grain size of the W films increased, and the crystallinity of the W films was enhanced due to a reduction of the uniform strain. The elimination of uniform strain in W films and the increase in grain size led to a decrease in the sheet resistance of the W/WNx/poly-Si1-xGex structure. In addition, no evidence of the formation of WSix was observed even after annealing at 900degreesC for 30 min due to the WNx barrier between the W film and the poly-Si1-xGex film. However, the N content of the WNx films decreased by about 61% of the initial amount and accumulated below the WNx layer, suggesting an interfacial reaction between the WNx film and the poly-Si1-xGex film. As the annealing temperature increased, the amount of dopant in the poly Si1-xGex films of the W/WNx/poly-Si1-xGex system also decreased due to boron accumulation and the formation of a boron compound (BN). (C) 2003 The Electrochemical Society.