We have investigated the effect of the annealing conditions on the microstructure and electrical properties of nonstoichiometric strontium bismuth tantalate (SBT) thin films prepared by metallorganic decomposition. The films were deposited on Pt/TiO2/SiO2/Si( 100) substrates, using Sr(thd)(2), Bi(thd)(3), and Ta(OC2H5)(5) as precursors. Annealing of the films was carried out at 600-750 degreesC under an O-2 atmosphere. Crystallization of the orthorhombic SBT phase is completed at 650 degreesC. However, good ferroelectric properties are only observed in films annealed at temperatures above 700 degreesC as a result of elongated grain growth. Remnant polarization (P-x) values of 4-6 muC/cm(2) and coercive fields (2 \E-c\) between 182 and 210 kV/cm have been measured in 300 nm thick films annealed at 750 degreesC. These films are randomly oriented, and their surface morphology is formed by rod-shaped grains having average long axis lengths of 150-180 nm and elongation factors of 1.7-1.8. The effect of microstructure on the net spontaneous polarization measured in these films is also discussed.