Insulating epitaxially grown SrTiO3 thin films were prepared on (100)MgO substrates by metal-organic chemical vapor deposition (MOCVD). Semiconductive SrTiO3 thin films were obtained by the rapid cooling after reheating in reduction atmosphere. The microstructure, crystal structure, and electrical properties of these films were investigated. The electrical properties varied by the composition of films and heat-treatment conditions, i.e., the heating temperature, the oxygen partial pressure, and the cooling rate after the annealing. Change of the resistivity of the film was attributed to that of the carrier concentration. Mobility of films was unchanged, and the value was almost the same order of that of bulks. The lowest resistivity of 0.1 Ω·cm was obtained when a sample of Ti/Sr = 1.0 was heated at 1200 °C under 10−15 Pa of PO2 and then rapidly cooled. This value is similar to that of bulks (100 –10−1 Ω · cm).