The drain current activation energy dependence on the gate voltage is first evaluated from temperature measurements in both low temperature (<= 600 degrees C) polysilicon thin film transistors and in crystalline silicon N-MOSFETs, operating from sub-threshold to above-threshold regions. The noise behaviour of these transistors is then described with a low frequency noise model based on the Meyer-Neldel drain current expression. This model is built on carrier fluctuations at the gate oxide/active layer interface and the corresponding defect density is then deduced. It suggests that these defects close to the interface, causing detrapping/trapping processes of carriers and fluctuations of the flat-band voltage, are mainly responsible for the low frequency noise in the two operating modes. Noise measurements on different N-MOS transistors are confronted to result from the presented model. (c) 2005 Elsevier Ltd. All rights reserved.