Influence of Thermal Noise on Drain Current in Very Small Si-MOSFETs.

We investigate the intrinsic current fluctuations in very small Si-metal-oxide-semiconductor field-effect-transistors (MOSFETs) using Monte Carlo device simulation. It is demonstrated that the temporal fluctuation of the drain current in small Si-MOSFETs attains a significant fraction of the averaged drain current when the device width is scaled down to the deep sub-µm regime. This enhancement of current fluctuation is caused by the drastic decrease in the number of channel electrons underneath the gate. It is also demonstrated that current fluctuation is physically associated with the quasi-equilibrium thermal noise in the heavily doped source and drain regions. More significantly, the current fluctuation is intrinsically unavoidable and could be a critical issue for further device shrinkage.