Patent ID: 8304320

Claim:
A method of fabricating a structure comprising a field-effect transistor from a semiconductor body having body material of a first conductivity type, the method comprising: defining a gate electrode above, and vertically separated by a gate dielectric layer from, a portion of the body material intended to be a channel zone; and introducing composite semiconductor dopant of a second conductivity type opposite to the first conductivity type into the semiconductor body to form first and second source/drain (“S/D”) zones of the second conductivity type laterally separated by the channel zone such that each S/D zone comprises a main S/D portion and a more lightly doped lateral S/D extension laterally continuous with the main S/D portion and extending laterally under the gate electrode, the channel zone is terminated by the S/D extensions directly below the gate dielectric layer, the S/D extensions of the first and second S/D zones are respectively largely defined by first and second dopants of the composite dopant, the first dopant of the second conductivity type is of higher atomic weight than the second dopant of the second conductivity type, and the main S/D portions of the S/D zones are defined primarily by a third dopant of the composite dopant; wherein: the body material extends laterally below the first and second S/D zone and is defined by semiconductor dopant of the first conductivity type; the dopant of the first conductivity type is also present in the first and second S/D zones; and the method further includes, prior to the act of defining the gate electrode, introducing primary semiconductor dopant of the first conductivity type into the semiconductor body such that, upon completion of fabrication of the structure, (i) the semiconductor body has an upper surface along which the gate dielectric layer extends, (ii) one of the main S/D portions extends to a maximum depth below the body's upper surface, and (iii) all semiconductor dopant of the first conductivity type in the semiconductor body has a concentration which (a) locally reaches a concentration maximum in the semiconductor body at a subsurface body-material location extending laterally below largely all of each of the channel zone, the first S/D zone main S/D portion, and the second S/D zone main S/D portion, (b) decreases by at least a factor of 10 in moving upward from the subsurface body-material location along a selected vertical location through the one main S/D portion to the body's upper surface, and (c) decreases substantially monotonically in moving from the subsurface body-material location along the selected vertical location to the one main S/D portion, the subsurface body-material location occurring no more than 10 times deeper below the body's upper surface than the maximum depth of the one main S/D portion.