Prospective characteristics of nanoscale MOSFETs

Among emerging issues on nanoscale MOSFETs, two aspects are discussed. One is a new type of parasitic capacitance in MOS capacitors, and the other is analysis of channel transport in terms of a newly developed reflection-transmission formalism. The non-zero thickness of charge layer in the MOS gate electrode causes a new type of parasitic capacitance, which is comparable to and is equally serious as the notorious inversion and gate-depletion capacitances. The reflection-transmission approach suggests difficulty of achieving ballistic transport by simple down-sizing, showing that even a 5 nanometer MOSFET suffers considerable degradation of ballistic current. At the same time, the analysis shows the energy relaxation due to optical phonon emission plays an essentially different role from the elastic scattering. The elastic scattering causes carrier back-scattering and degrades the device current, but the optical phonon emission prevents the back-scattering and encourages the device current