We use a full quantum model of MOS (metal oxide semiconductor) structure to study
the influence of a non-uniform doping profile of the substrate on the capacitance-voltage (C−V)
behavior of the structure. For different “realistic” doping profiles, simulations are performed and
compared to simulations with an uniform doping and to C−V measurements for samples with
oxide thickness in the range [2−5 nm] [1]. In each case, we have extracted the oxide thickness that
is found to be independent of the doping and the flat-band voltage which can be shifted up to
200 mV regarding the different profiles tested here. Moreover, below about 3 nm, the shape of the
C−V simulation is more affected, which shows that the doping profile of the substrate has a great
importance for an accurate C−V modeling of ultra-thin MOS structures.