Increasing importance of electronic thermal noise in sub-0.1 mu m Si-MOSFETs

We investigate the intrinsic current fluctuations in small Si-MOSFETs via t he Monte Carlo device simulation. It is demonstrated that the temporal fluc tuation of the drain current in Si-MOSFETs attains a significant fraction o f the averaged drain current when the device width is scaled down to the de ep sub-mu m regime. This is caused by the drastic decrease in the number of channel electrons. This finding holds true whenever the device width is re duced to deep sub-mu m, regardless of the channel length. Most importantly, current fluctuation is associated with the quasi-equilibrium thermal noise in the heavily-doped source and drain regions, whereas its magnitude with respect to the averaged drain current is directly related to the number of channel electrons underneath the gate.