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In this study, (AlCrTaTiZr)N0.7and (AlCrTaTiZr)N1films with quinary metallic elements were developed as diffusion barrier materials for Cu interconnects. To improve the interface adhesion to Cu, an AlCrTaTiZr buffer layer was deposited on the barriers to form (AlCrTaTiZr)N0.7/AlCrTaTiZrand (AlCrTaTiZr)N1/AlCrTaTiZrbilayer structures. The as-deposited AlCrTaTiZr and (AlCrTaTiZr)N0.7films were amorphous structures, and (AlCrTaTiZr)N1possessed a nanocomposite structure. After annealing at 800°C, although Cu penetrated into the AlCrTaTiZr buffer layer, the diffusion of Cu was retarded by the (AlCrTaTiZr)N0.7and (AlCrTaTiZr)N1barriers. During annealing at 900°C, the interdiffusion of Si and Cu occurred through the (AlCrTaTiZr)N0.7/AlCrTaTiZrbilayer, and Cu silicides formed. However, the (AlCrTaTiZr)N1/AlCrTaTiZrbilayer remained stable. Neither the interdiffusion of Cu and Si through the (AlCrTaTiZr)N1/AlCrTaTiZrbilayer nor the silicide formation was identified, indicating the high diffusion resistance of the bilayer structure.