Temperature-dependent, the capacitance-frequency measurements of Sn/polypyrrole/n-Si structure have been carried out by using the Schottky capacitance spectroscopy (SCS) technique. It has seen that capacitance almost independent of temperature up to a certain value of frequency but the capacitance decrease at high frequencies. Besides, the interface states densities show a decrease with bias from the bottom of the conduction band towards the midgap at different temperature. The values of relaxation time have been higher towards the low temperature. The higher values of capacitance at low frequencies were attributed to the excess capacitance resulting from the interface states in equilibrium with the n-Si that can follow the Ac signal. (c) 2005 Elsevier Ltd. All rights reserved.