Monte Carlo, Hydrodynamic and Drift-Diffusion Simulation of Scaled Double-Gate MOSFETs

Double-gate MOSFETs with gate lengths of 50 and 25 nm are theoretically analyzed by drift-diffusion (DD), hydrodynamic (HD) and self-consistent full-band Monte Carlo (MC) simulation. The underestimation of the on-current I _on by DD is found to be stronger than the overestimation by HD. The main differences to the case of bulk MOSFETs are: (i) not only the velocities in the source-side of the channel, but also the sheet densities vary appreciably between the different transport models, (ii) current conservation leads to strong non-equilibrium in the highly doped source region with high velocities and electric fields and (iii) surface roughness appears to become more effective for reduced silicon film thicknesses which might jeopardize the performance enhancement upon further scaling.