Nanoscale silicon MOSFETs: A theoretical study

We have carried out extensive numerical modeling of double-gate, nanoscale silicon n-metal oxide semiconductor field effect transistors (MOSFETs) with ultrathin, intrinsic channels connecting bulk, highly doped electrodes. Our model takes into account two most important factors limiting the device performance as the gate length is reduced, namely the gate field screening by source and drain, and quantum mechanical tunneling from source to drain. The results show that the devices with small but plausible values of gate oxide thickness t_ox and channel thickness t (both of the order of 2 nm) may retain high ON current, good saturation and acceptable subthreshold slope even if the gate length L is as small as ∼5 nm, with voltage gain above unity all the way down to L≈2 nm (channel length L_c=L+2t_ox≈5 nm). However, as soon as L is decreased below ∼10 nm, specific power (per unit channel width) starts to grow rapidly. Even more importantly, threshold voltage becomes an extremely sensitive function of L,t, and t_ox, creating serious problems for reproducible device fabrication.