The impact of additives (La, Al and Mg) at the SiO2/high-kappa interface has been investigated through ab initio simulations and electrical measurements. Various gate stacks with additive below or the above high-kappa dielectric are compared. Combination of capacitance versus gate bias measurement and internal photon emission is performed to demonstrate that the threshold voltage shift is related to a dipole formation at the SiO2/high-kappa interface. The respective roles of aluminum and lanthanum are clearly identified as well as their sensitivity to roll-off. Impact of additive on metal gate function is studied. Finally, ab initio enables an analysis of the dipole formation with additive at the SiO2/HfO2 interface. (c) 2013 Elsevier Ltd. All rights reserved.