The path of crystal growth from the precursor to SrBi2Ta2O9 (SBT) crystal was investigated in order to obtain abetter method of fabricating SET films. A phase diagram of the Sr-Bi-Ta-O system With a constituent element ratio similar to that of SET was determined. Thin film samples were prepared by the metal-organic decomposition method. In the case of a Bi-rich nominal composition (compared with SBT crystal), a fluorite-like structure appeared at the early stage of the crystal growth, after which the SET phase was finally stabilized. The lower limit of annealinng temperature for synthesis of SET thin films with thicknesses less than 100 nm was about 650 degrees C.