The leakage current behaviour of SrTiO3 thin films was investigated. The commonly reported Schottky emission regime is extended towards low fields for which an ohmic and a saturation regime is found. In addition, the deviation from the Schottky effect towards high fields is explained by applying a more general injection law which is valid over all temperatures and fields and which includes the Schottky approximation as a special case. From this general injection law, the width of the Schottky depletion layer is obtained unambiguously showing that the film is completely depleted.