Analysis of Zn/p-Si Schottky diodes (SDs) with high resistivity has been given by admittance spectroscopy. The importance of the series resistance in the determination of energy distribution of interface states and especially their relaxation time in the SDs with high resistivity has been considered. The effect of the series resistance on capacitance-conductance/frequency characteristics has been given by comparing experimental data with theoretical data. The interface state density A,, from the admittance spectroscopy ranges from 1.0 X 10(12) cm(-2) eV(-1) in 0.720-E-v eV to 2.03 x 10(12) cm(-2) eV(-1) in 0.420-E-v eV. Furthermore, the relaxation time ranges from 4.20 x 10(-5) s in (0.420-E-v) eV to 3.20 x 10(-4) s in (0.720-E-v)eV. It has been seen that the interface state density has a very small distribution range (1.0-2.03 x 10(12) cm(-2) eV(-1)) that is ascribed to the predominant termination with hydrogen of the silicon surface after HF treatment. (C) 2003 Elsevier Ltd. All rights reserved.