In this work, we report the development of a 3D drift-diffusion (DD) simulator for ultrascaled transistors with quantum corrections based on the solution of the Schrödingerequation. In a novel multi-scale simulation approach we use effective masses from tight-binding calculations, carrier mobility from the semi-classical Kubo-Greenwood formalism, and quantum corrections based on self-consistent Poisson-Schrödinger solution. This scheme has been implemented into the University of Glasgow TCAD tool called NESS (Nano Electronic Simulation Software). The approach is validated with respect to non-equilibrium Green's function (NEGF) simulations in the case of nanowire field effect transistors with different cross-sectional shapes. © 2019 IEEE.