In this paper, a theoretical analysis of thin film oxide resulted from lumped element model analysis using ASITIC simulation tool is presented. The study is aimed to investigate the effect of the oxide thickness on the electrical characteristics of planar micro-coils. Some important device parameters, such as parasitic capacitances and resistances caused by oxide and substrate layer, and quality factor of the planar coil, as well as the characteristic of the magnetic field coupled between the coils are analyzed in wide range of operating frequency. The simulation results show that there is significant influence of the oxide thickness to the device characteristics. It is shown that by increasing the thickness of the oxide layer on the substrate, a high Q-factor of 5 can be obtained, while the magnetic coupling is improved when the thickness of the oxide layer residing between metal layers is reduced.