Bismuth titanate (Bi4Ti3O12) (BTO) thin films were fabricated on an n-type Si substrate and annealed by rapid thermal annealing methods. The I-V measurement shows that the device has properties of Schottky diode with the Phi(B0) of 0.76 eV, n of 2.42, and leakage current of about 10(-7) A at -8 V. The experimental C-V-f and G/w-V-f characteristics of metal-ferroelectric-insulator-semiconductor (MFIS) structures show fairly large frequency dispersion especially at low frequencies due to interface states N-ss. The energy distribution of (N-ss) has been determined by using the high-low frequency capacitance (C-HF-C-LF) and conductance method. The relaxation time (tau) of interface states was calculated from the conductance method. It has been shown that both the N-ss and relaxation time increase almost exponentially with bias, which activates traps located at deeper gap energies. Copyright (C) 2011 John Wiley & Sons, Ltd.