Substituted aluminum (SA) metal gate on high-kappa gate dielectric is successfully demonstrated. Full substitution of polysilicon with Al is achieved for a Ti-Al-polysilicon-HfAlON gate structure by a low-temperature annealing at 450 degreesC. The SA gate on HfAlON dielectric shows a very low work function of 4.25 eV, which is well suitable for bulk nMOSFETs. The SA process is fully free from the Fermi-level pinning problem. In addition, the SA process also shows improved uniformity in leakage current distribution compared to fully silicided metal gate.