Low frequency noise in 0.18 mum technology n-MOSFETs is investigated in subthreshold, ohmic and saturation regimes. The impact of the channel length on the drain current noise characteristics is studied. The results are analysed as a function of the drain current or gate voltage and compared to the existing noise models. We find that the 1/f noise can be interpreted in terms of carrier number fluctuations. The oxide trap density N-t at the Fermi energy level is evaluated. The significant deviation of the normalised noise amplitude observed at high V-GS is attributed to the noise in the access resistances. In deep saturation regime, for gate length device <0.9 μm, the drain current spectral density tends to saturate with the gate overdrive voltage. The noise characteristics calculated with BSIM3v3 noise model are compared with the experimental results and discussed. (C) 2002 Elsevier Science Ltd. All rights reserved.