The ongoing miniaturizing of electronic devices poses major challenges to semiconductor industry. One of the fundamental limits is the down-scaling of the gate oxide. Using conventional SiO₂, scaling below 1.5 nm results in intolerable leakage currents due to direct tunneling. Alternative oxides with larger dielectric constant, so-called high-k oxides, can be employed at larger thickness, while their electrical properties (capacitance) are equal to that of an ultrathin SiO₂ layer. Currently, this is the most promising route for avoiding leakage currents in future devices. One of the major problems related to gate oxides is the quality of the interface between silicon and the oxide. Epitaxial oxides hold the promise of low interface defect concentrations on a level comparable to that of conventional SiO₂ based gate oxides. In this work, we concentrated on the deposition of Zr on Si(001) as a first step of oxide growth but also report on results obtained for Sr and Hf. We use state-of-the-art electronic structure calculations and ab-initio molecular dynamics simulations based on density functional theory and the projector augmented wave method. Our results relate to a number of experimental results reported so far and therefore improve the global understanding of the oxide growth processes.