In this study, our main goal is fabricated with and without insulator layer Au/GaAs Schottky barrier diodes (SBDs) to explain whether or not he insulator layer is effective oil some electric parameters such as phi(B), n. N-ss, and R-s, The current-voltage (I-V) and capacitance-voltage (C-V) characteristics of metal-semiconductor (Au/u-GaAs) are investigated and compared with metal-insulator-semiconductor (Au/SiO2/n-GaAs) Schottky diodes. Horn the room temperature I-V characteristics of these devices, the main electrical parameters Such as, ideality factor (n) and zero bias barrier height (phi(bo)) values of 1.25 and 0.73 eV for Au/n-GaAs. and 1.51 and 0.75 eV for Au/SiO2/n-GaAs, were obtained. The interface distribution profile (N-ss) as a function of (E-c E-ss) was extracted from the forward-bias I-V measurements by taking into account the bias dependence of the effective barrier height (phi(e)) and series resistance (R-s) for the Schottky diodes. The Nss values obtained taking into account the series resistance Values are lower than those obtained Without considering the series resistance. The diodes show non-ideal I-V behavior with ideality factor greater than unity. This behavior is attributed to the interfacial insulator layer and the interface states. The I-V characteristics confirmed that the distribution of N-ss, R-s, and interfacial insulator layer are Important parameters that influence the electrical characteristics of metal-semiconductor and metal-insulator-semiconductor Schottky diodes. (C) 2009 Elsevier Ltd. All rights reserved.