Patent ID: 7595244

Claim:
A method of fabricating a pair of like-polarity first and second field-effect transistors (“FETs”), the method comprising: separately introducing a plurality of primary semiconductor dopants of a first conductivity type into body material of a semiconductor body such that the body material is of the first conductivity type; subsequently defining a pair of gate electrodes respectively for the FETs such that (a) the gate electrodes are situated above, and vertically separated by gate dielectric material from, a pair of parts of the body material intended to be channel zones respectively for the FETs, (b) the semiconductor body has an upper surface along which there are locations for a pair of channel surface depletion regions that respectively extend into the channel zones during operation of the FETs, (c) each of the primary dopants of the first conductivity type reaches a maximum concentration below the locations of the channel surface depletion regions and below largely all material of the gate electrodes overlying the parts of the body material intended to be the channel zones, and (d) each maximum concentration of the primary dopants of the first conductivity type occurs at a different depth into the body material than each other maximum concentration of the primary dopants of the first conductivity type; and introducing (i) additional semiconductor dopant of the first conductivity type into at least the intended channel-zone parts of the body material and (ii) semiconductor dopant of a second conductivity type opposite to the first conductivity type into the semiconductor body such that (a) the dopant of the second conductivity type forms, for each FET, a pair of source/drain zones of the second conductivity type laterally separated by that FET's channel zone, (b) a pocket portion of the body material more heavily doped than laterally adjacent material of the body material and defined by the additional dopant of the first conductivity type extends along each of the source/drain zones of the first FET and into its channel zone, and (c) a pocket portion of the body material more heavily doped than laterally adjacent material of the body material and defined by the additional dopant of the first conductivity type extends largely along only one of the source/drain zones of the second FET and into its channel zone such that the channel zone of the second FET is asymmetrical.