In this work the electrical properties of the locally produced MOS devices are investigated. For this purpose, simple MOS capacitor is used. The oxide in this structure was prepared by the thermal oxidation technique. MOS capacitors are used for its simple fabrication and analysis. The important parameters which affect the MOS device performance and stability are mobile impurities, oxide charge and interface states density which are described in details in the present work. The techniques most extensively used for electrical analysis of the MOS devices are capacitance and conductance measurements. The dielectric loss, which yields information on the presence of defects, was also measured for different voltages and frequencies. Interface state density Nss For different locally made p-type and n-type samples where measured and investigated. Practical results gives Nss= 3.092 x K, V1 cm'2 for the/r-type samples and Na= 5.773 x 1010 eV1 cm"2 for the n-type samples. These values are relatively higher than the standard ones To reduce the Nss value two approaches are used. The first is careful preparation and cleaning steps, the second was the post annealing of the prepared samples. The results obtained with postannealing technique to 400 °C for 45 min. give reasonable values for N. for the locamade MOS devices.