Patent ID: 8258026

Claim:
A method of fabricating a structure comprising a field-effect transistor, the method comprising: introducing primary semiconductor dopant of a first conductivity type into body material of a semiconductor body such that the body material is of the first conductivity type; defining a gate electrode above, and vertically separated by a gate dielectric layer from, a segment of the body material intended to be a channel zone; 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 (a) the body material forms respective pn junctions with the S/D zones and extends laterally below both S/D zones, (b) the primary dopant of the first conductivity type is also present in the S/D zones, (c) 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, and (d) the channel zone is terminated by the S/D extensions directly below the gate dielectric layer; and performing additional processing to complete fabrication of the structure such that, upon completion of fabrication of the structure, (a) the semiconductor body has an upper surface, (b) each pn junction extends to a maximum depth below the body's upper surface, (c) all semiconductor dopant of the first conductivity type in the semiconductor body has a concentration which (c1) locally reaches a subsurface maximum concentration at a subsurface maximum concentration location extending laterally below largely all of each of the channel and S/D zones, (c2) decreases by at least a factor of 10 in moving upward from the subsurface maximum concentration location along a selected vertical line through a specified one of the S/D zones to the body's upper surface, and (c3) has a logarithm that decreases substantially monotonically and substantially inflectionlessly in moving from the subsurface maximum concentration location along the selected vertical line to the pn junction for the specified S/D zone, and (d) the subsurface maximum concentration location occurs no more than 10 times deeper below the body's upper surface than the maximum depth of the pn junction for the specified S/D zone.