Initiation of the crystallization of the triple-alkoxy-derived gel films to SrBi2Ta2O9(SBT) perovskite thin films on Pt-passivated Si was addressed. The organic functional group of the triple alkoxide may determine the degree of the hydrolysis and poly-condensation reactions and affect the nucleation sites in the film after annealing. A mixture of water vapor and oxygen flow during the calcination at 250°C promoted the nucleation and growth of SBT below 500°C. It was clarified that the crystallographic orientaion of the SBT thin films has been determined in the primary stage of the crystallization.