A method to extract gate-bias-dependent MOSFET's effective channel width

A modification to the conventional channel conductance method is introduced to extract the MOSFET's effective channel width W/sub eff/. The gate-bias-dependent effective channel width can be readily delineated with this extraction method. The physical meaning of this gate-bias dependence is further discussed, and structures with different isolation configurations are studied. W/sub eff/ is influenced by the local oxide thickness, surface doping concentration, and gate voltage. Unless the transition between the channel active area and field isolation area is so abrupt that changes of both oxide thickness and doping concentration are like step functions, gate-bias dependence of W/sub eff/ will be inevitable. As gate bias increases in the strong inversion region larger gate bias will gradually turn on the transition region. This in turn increases the W/sub eff/. A strong or weak gate-voltage dependence of W/sub eff/ is indicative to a gradual or fast transition in doping concentration and oxide thickness from channel to the field regions.<
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