Degradation of body factor (y) and subthreshold factor (S) of single gate fully depleted SOI MOSFETs due to short channel effects has been studied analytically. The effect of source/drain fringing fields in buried oxide is found to play a more significant role in the reduction of body factor at smaller gate lengths. Present work provides the analytical expressions of effective back gate voltage, body factor and subthreshold factor of short channel fully depleted SOI MOSFETs. The results obtained are found in good approximation with 2D simulation. (c) 2005 Elsevier Ltd. All rights reserved.