Density functional theory calculations are used to highlight some basics of the densification mechanisms arising during atomic layer deposition of HfO2 onto silicon dioxide. The obtained results are discussed at the light of a multi-model approach that enables process simulation at the atomic scale via Kinetic Monte Carlo simulations. The impact of the proposed densification mechanisms on the growth is demonstrated. We show that a complete coverage is possible thanks to these mechanisms at a slow rate after that all surface reactive sites (OH sites) have been consumed by precursor molecules. (C) 2011 Elsevier B.V. All rights reserved.