Utilization of ferroelectric thin films for nonvolatile random access memory (NvRAM) applications has been under intensive investigation. Films for transistor-type memory require possessing these properties: a large remnant polarization, a low coercive field (2E c ), sufficient fatigue endurance against repetitive polarization switching. Layered perovskite structure SrBi 2 Ta 2 O 9 (SBT) thin film has attracted ever increasing attention because it exhibits fatigue-free property up to 10 12 cycles (even on Pt bottom electrode), excellent retention characteristics, and low leakage current density. However, two shortcomings are involved in SBT thin films: the low remnant polarization (2Pr<10μC/cm 2 ) and high annealing temperature (>800℃). Substitution at A or B site can effectively modify polarization properties. Trivalent elemental substitution such as Bi 3+ , La 3+ and Nd 3+ with the Sr 2+ site induces A-site cation vacancies to satisfy charge neutrality, which significantly improves the low-field polarization.This project aims to improve the polarization properties through doping, and at the same time to reduce the crystallization temperature of the Aurivillius phase. The Sr-deficient and Nd-doped SBT thin films are deposited via radio frequency magnetron sputtering. The relationship among deposition parameters, microstructure and polarization properties of Sr-deficient SBT thin films are discussed in details so that pure layered perovskite structure without pyrochlore is obtained. Based on this,