In this study, Al/p-Si and Al/Bi4Ti3O12/p-Si structures are fabricated and their interface states (N-ss), the values of series resistance (R-s), and AC electrical conductivity (sigma(ac)) are obtained each as a function of temperature using admittance spectroscopy method which includes capacitance-voltage (C-V) and conductance-voltage (G-V) measurements. In addition, the effect of interfacial Bi4Ti3O12 (BTO) layer on the performance of the structure is investigated. The voltage-dependent profiles of N-ss and R-s are obtained from the high-low frequency capacitance method and the Nicollian method, respectively. Experimental results show that N-ss and R-s, as strong functions of temperature and applied bias voltage, each exhibit a peak, whose position shifts towards the reverse bias region, in the depletion region. Such a peak behavior is attributed to the particular distribution of N-ss and the reordering and restructuring of N-ss under the effect of temperature. The values of activation energy (E-a), obtained from the slope of the Arrhenius plot, of both structures are obtained to be bias voltage-independent, and the E-a of the metal-ferroelectric-semiconductor (MFS) structure is found to be half that of the metal-semiconductor (MS) structure. Furthermore, other main electrical parameters, such as carrier concentration of acceptor atoms (N-A), built-in potential (V-bi), Fermi energy (E-F), image force barrier lowering (Delta Phi(b)), and barrier height (Phi(b)), are extracted using reverse bias C-2-V characteristics as a function of temperature.