The dielectric properties and electrical conductivity of Al/SiO2/p-Si (MIS) Schottky diodes (SDs) in the frequency range of 10 kHz to 10 MHz and the gate voltage range of 2 to 6 V have been investigated in detail using experimental C-V and G/w-V measurements. Experimental results indicated that the voltage dependence of the real part of the dielectric constant (epsilon') and loss tangent (tan delta) characteristics have a peak at each frequency. The values of epsilon' increase with decreasing frequency and tend to be frequency independent in the negative voltage region. However, the values of the dielectric loss (epsilon '') increase with decreasing frequency at each voltage. In contrast, epsilon' and epsilon '' are almost found to decrease, and the ac electrical conductivity (sigma(ac)) and the real part of the electric modulus (M') increase, with increasing frequency. In addition, the imaginary part of the electric modulus (M '') showed a peak that shifts to a higher frequency with increasing applied voltage. It can be concluded that interfacial polarization can more easily occur at low frequencies, and consequently the majority of interface states at the Si-SiO2 interface contribute to the deviation of the dielectric properties of Al/SiO2/p-Si (MIS) SDs. (C) 2011 American Institute of Physics.