In this paper, we report a model for calculating the gate current as a function of gate and drain biases by considering the quantum-mechanical effect. Using a WKB approximation for the transmission probability, direct and Fowler-Nordheim tunneling currents across thin gate oxides of MOSFETs have been modeled for carriers from the inversion layers in Si substrate. The modeled direct tunneling currents have been compared to experimental data obtained from MOSFETs with oxide thickness of 2 nm. The gate current model is developed by using a pseudo-2D and analytical drain current model as a basis to generate channel electric field and electron temperature, which is derived using a simplified energy balance equation. From the electron temperature, we can calculate the non-local gate current. This model is a time-saving CAD model.