There is provided a method for fabricating a ferroelectric capacitor which comprises the steps of: forming a bottom electrode over a substrate on which a predetermined lower structure is formed; forming a thin film of polycrystalline strontium bismuth tantalate (SBT) over the entire structure; forming an amorphous thin film of SBT on the polycrystalline film of SBT; and forming an upper electrode on the amorphous film of SBT. Though the amorphous thin film of SBT is lower in dielectric constant than the polycrystalline thin film of SBT so as not to have the properties of ferroelectric, it does not have crystalline grain boundary and, thus, does not form the path for transferring material. Therefore, the amorphous thin film of SBT can block the path of leakage current. It also results in complement of bismuth lost in the processes of deposition and thermal treatment for crystallization of the ferroelectric film of SBT at a high temperature.