Langmuir ion probe and in situ RHEED were applied to study the effects of low oxygen pressure on SrTiO3 (STO) film growth by Pulsed Laser Deposition (PLD). Contributions of different oxygen fluxes were analysed and parameters of STO epitaxial film growth were evaluated using physical model of adiabatic expansion of the ablation products and its interaction with ambient gas. Film surface undergoes reconstruction at growing temperatures > 600 degrees C indicating complete or partial relaxation of top layer without changing growth mechanism of smooth multilayered film. All films have a tetrahedral lattice distortion in the direction of growth that varying with deposition temperature and oxygen pressure. STO lattice distortion is the relevant factor in determining both agility and dielectric loss for tuneable microwave devices. Annealing in oxygen at 1100 degrees C improves significantly functional properties of STO films, but only the layers deposited under the pressure lower than 10(-3) Pa possesses low dielectric losses in combination with high agility. (C) 2007 Elsevier B.V. All rights reserved.