  The accuracy of contact resistance values of two-dimensional field-effect
transistors extracted with the \textit{Y}-function considering the impact of
the intrinsic mobility degradation is evaluated here. The difference between
methodologies that take this factor into account and ignore it is pointed out
by a detailed analysis of the approximations of the transport model used for
each extraction. In contrast to the oftenly used approach where the intrinsic
mobility degradation is neglected, a \textit{Y}-function-based method
considering a more complete transport model yields contact resistance values
similar to reference values obtained by other intricate approaches. The latter
values are more suitable also to describe experimental data of two dimensional
devices of different technologies. The intrinsic mobility degradation factor of
two-dimensional transistors is experimentally characterized for the first time
and its impact on the device performance is described and evaluated.
