It's just body doping (typically quite low, "intrinsic") and
gate poly doping, their difference makes the work function.
I used to work in a technology that gave me depletion,
intrinsic, low VT and "regular" VT of both N and P type.
There were only two VT-adjust implants per species
(or none) to get all 8 types. Crossing up the S/D and
gate poly doping was another degree of freedom.
Not all were that great, but I used them all on occasion.
This was an oddball SOI technology. I see some JI
that has intrinsic NMOS, this would require either an
unusually light body doping or a really jacked work
function. RF technologies will make efforts to deliver
a zero-VT FET for switches and linear PAs.