difference between feature size and channel length in mosfet

[rp276]

kindly explain..what is difference between feature size and channel length in mosfet????

 

[dick_freebird]

Feature size has come to mean the minimum manufacturable
poly drawn dimension, although this was not always the case.
Back when, the contact used to be the most aggressive size.

But from there, actual electrical channel length is subject to
the lithography / processing deltas - over/underetch, LDD or
S/D side diffusion and designed reach-under, etc. So you
may see a Leff that varies above or below the advertised
feature size.

And of course you're usually at liberty to go longer on any
given FET, and might go shorter with enough begging and
signoff (cash and disclaimers).