Channel length-dependent series resistance?

A recently developed series resistance (R
_SD
) extraction procedure from a single nanoscale device is shown to be highly robust. Despite these virtues, the technique unexpectedly results in a channel length-dependent R
_SD
which is observed across a wide range of channel lengths and across many different technologies (SiO
₂
, SiON, and high-k) (see Figs. 1a-f). This observation obviously raises some concerning issues and implications as R
_SD
is universally accepted as channel length-independent. However, careful examination of the R
_SD
extraction procedure as well as comparison between R
_SD
-corrected field effect mobility (u
_FE
) and geometric magnetoresistance mobility (u
_MR
) suggests that this unexpected observation may be valid.