Quantum mechanical confinement and tunnelling play an important role in present and future generation decanano (sub-100 nm) MOSFETs and have to be properly taken into account in the simulation and design. Here we present a simple approach of introducing quantum corrections in a 3D drift-diffusion simulation framework using the density gradient (DG) algorithm. We discuss the calibration of the DG approach in respect of quantum confinement effects in comparison with more comprehensive but computationally expensive quantum simulation techniques. We also speculate about the capability of DG to describe source-to-drain tunnelling in sub-10 nm (nano) MOSFETS. The application of the DG approach is illustrated with examples of 3D statistical simulations of intrinsic fluctuation effects in decanano and nano-scale double-gate MOSFETs. (C) 2003 Elsevier Science Ltd. All rights reserved.