In conventional NMOS and CMOS technologies the 
-type gate is doped by the
deposition from POCl
source and subsequent diffusion. Similarly, in the
old PMOS technologies, 
-type gate has been doped by diffusion from
BCl or BBr. The gates produced by these diffusion processes are doped
heavily with a chemical concentration as high as 
.
It is established in the standard CMOS technologies that the same type of gate
( or ) is used for both devices, 
-channel and 
-channel. We
assume the more common -type gate in the following. For bulk and well
doping, as well as anti-punch-through implants the threshold voltage of
-channel devices would be too low. To increase the threshold voltage a
shallow threshold-adjustment implant of the acceptor-type is
used [469]. The thereby produced -channel MOSFETs are
surface-channel devices. Note that an increased dopant concentration at the
surface due to implantation reduces the surface low-field (ohmic) mobility. For
-channel devices with -type gate the threshold voltage would be too
high. An acceptor-type shallow threshold-adjustment implant is used to
decrease the absolute value of the threshold voltage. 
-channel MOSFETs
become buried-channel devices.
Assuming -type gates the opposite holds: -channel MOSFETs exhibit
a surface channel, while -channel MOSFETs become buried-channel
devices after a shallow donor-type threshold-adjustment implant.