Source-to-drain current including tunneling in deca-nanometer double-gate MOSFETs is studied using a Monte Carlo approach for the Wigner transport equation. This approach allows the effect of scattering to be included. The subband structure is calculated by means of post-processing results from the device simulator (MINIMOS)-NT, and the contribution of the lowest subband is determined by the quantum transport simulation. Intersubband coupling elements are explicitly calculated and proven to be small in double-gate MOSFETs. The simulation results clearly show an increasing tunneling component of the drain current with decreasing gate length. For long gate length the semi-classical result is recovered. (c) 2005 Elsevier Ltd. All rights reserved.