An analytical model has been developed to study inversion layer quantization in the ultra thin oxide MOS (metal oxide semiconductor) structures using variation and triangular well approaches.Accurate modeling of the inversion charge density using the continuous surface potential equations has been done.No approximation has been taken to model the inversion layer quantization process.The results show that the variation approach describes inversion layer quantization process accurately as it matches well with the BSIM 5 (Berkeley short channel insulated gate field effect transistor model 5) results more closely compared with triangular well approach. An analytical model has been developed to study inversion layer quantization in the ultra thin oxide MOS (metal oxide semiconductor) structures using variation and triangular well approaches. Accurate modeling of the inversion charge density using the continuous surface potential equations has been done. No approximation has has taken to model the inversion layer quantization process. The results show that the variation approach describes inversion layer quantization process accurately as it matches well with the BSIM 5 (Berkeley short channel insulated gate field effect transistor model 5) results more closely compared with triangular well approach.