Two and three dimensional growth of SrTiO3 films on (001) MgO substrate was achieved by pulsed laser interval and pulsed laser deposition respectively. The growth mode was monitored by in-situ reflection high energy electron diffraction. Interval deposition forces layer-by-layer growth of materials even with such a large lattice misfit (similar to 7.9%). A titanium dioxide buffer monolayer was deposited to allow the film to wet the substrate to encourage two dimensional growth of the strontium titanate. A variety of defects was investigated using transmission electron microscopy and high resolution scanning transmission electron microscopy. Misfit dislocations, steps at the interface, Ti-rich defects and regularly shaped nano-holes connected by anti-phase boundaries were found to be the dominant defects in these films grown layer by layer. The edges of the nano-holes were mainly along  and 1100] for a  growth direction. The large strain between the two crystal systems with large lattice mismatch leads to in-plane tensile stress during the layer-by-layer growth. The stress is relieved in part by the holes. The films with a three dimensional growth mode possess a uniform surface with dislocations as the dominant defects. The individual densities of the various defects, including a Ti-rich phase and misfit and threading dislocations, are determined by the kinetics of the deposition method. (C) 2011 Elsevier B.V. All rights reserved.