Study on effects of changing the oxide thickness, can give us a view of the aspects of MOSFET, in field of design of the transistor elements. Changing the oxide thickness affects on both Cox and Vt. At first, in this paper, the relation between the threshold voltage and oxide thickness will be discussed. Then, the relation between the drain current and oxide thickness will be modeling. The result is a nonlinear and parabolic relationship between the drain current and oxide thickness. To ensure the authenticity of the obtained model, a MOSFET parameters, based on 5 µm CMOS technology was designed. This MOSFET was simulated with COMSOL software and obtained mathematical model analyzed with MATLAB. Finally, the data were compared, which confirmed the authenticity of the mathematical model. پرونده مقاله