In this work a non-local band-to-band tunnelling model has been implemented into a full-band Monte Carlo simulator. Two different approaches for the choice of the tunnelling path have been implemented and their impact on the transfer characteristics of different Tunnel FET structures is investigated. In both the SOI and the DG TFET architectures we have simulated, up to 1 order of magnitude of underestimation in the current and up to 15% of difference in the value of the Subthreshold Slope can be found according to the choice of the tunnelling path. © 2011 IEEE.