The work presented in this paper focuses on the effects of high leakage current in field effect transistors and the possible ways to play down with the leakage currents. This paper combines density functional theory and non equilibrium Green's function formalism to perform atomic scale calculation of tunnel currents through SiO2, HfO2, Ta2O 5ZrO2 and DY2O3 dielectrics in MOSFETs. The tunnel currents for different bias voltages applied to Si/Insulator/Si systems have been obtained along with tunnel conductance v/s bias voltage plots for each system and the plots have been analyzed with reference to the presently used bulk Si/SiO2/Si systems that have SiO2 as the gate dielectric material. The results justify the use of high dielectric constant materials as gate dielectric in FET devices so as to enable further downscaling of MOSFETs with reduced gate leakage currents thereby enabling ultra large scale integration. © 2013 IEEE.