The weak increasing of the ac electrical conductivity (蟽ac) on frequency is observed. The real part of electric modulus (M鈥? increases with increasing frequency. Also, the imaginary part of electric modulus (M鈥? shows a peak and the peak position shifts to higher frequency with increasing applied voltage. The energy loss tan 未 versus frequency has a weak wide peak at 300 kHz for each voltage. It can be concluded that the interfacial polarization can be more easily occurred at low frequencies, and the majority of interface states at metal semiconductor interface, contributes to deviation of dielectric properties of Al-TiW-PtSi/n-Si structures.