Ferroelectric SrxBi2+yTa2O9+$alpha$ thin films with various compositions(x=0.7, 0.8, 1, y=0.3, 0.4) were prepared by sol-gel method. The film with moled ratio of 0.8:2.3:2.0 in Sr/Bi/Ta, which was deposited on Pt/SiO2/Si (100), showed better ferroelectric properties than other films. To investigate substrate effects, the same compositions were spin coated on Pt/Ti/SiO2/Si (100) substrates. At an applied voltage of 5V, the dielectric constant($varepsilon$r), remanent polarization (2Pr) and coercive field (Ec) of the Sr0.8Bi2.3Ta2O9+$alpha$ thin film prepared on Pt/Ti/SiO2/Si (100) were about 296, 24$mu$C/$ extrm{cm}^2$ and Ec of 49kV/cm respectively. Both SBT films firred at 80$0^{circ}C$ revealed no fatigue up to 1010 cycles. Retention characteristics of these capacitors showed no degradation up to 104 sec.