This work is a presentation of the so-called "Bardeen's approach" formalism for tunneling. The way to use it for the modeling of tunnel current in MOS structure is also discussed. The theoretical background of this formalism is presented in an understandable way, and compared with other approaches. Then, an original method to use it is also proposed, which allows both numerical and analytical calculations. (C) 2002 Elsevier Science Ltd. All rights reserved.