Structure and fabrication of insulated-gate field-effect transistor with hypoabrupt change in body dopant concentration below source/drain zone

A method of fabricating a semiconductor structure from a semiconductor body, the method comprising:

• defining, for a principal field-effect transistor (“FET”), a principal gate electrode above, and vertically separated by a principal gate dielectric layer from, a segment of the semiconductor body intended to be a principal channel zone of a first conductivity type;
• introducing semiconductor dopant of a second conductivity type opposite to the first conductivity type into the semiconductor body to define, for the FET, a pair of principal source/drain zones of a second conductivity type opposite to the first conductivity type laterally separated by the channel zone such that, subsequent to completion of fabrication of the structure, (a) the semiconductor body has an upper semiconductor surface, (b) the channel zone is part of principal body material which is of the first conductivity type and which extends laterally below the source/drain zones, and (c) all semiconductor dopant of the first conductivity type in the semiconductor body has a concentration that decreases by at least a factor of 10 in moving upward to a specified one of the source/drain zones from a principal underlying subsurface body-material location which is no more than 10 times deeper below the upper semiconductor surface than the specified source/drain zone.

A method as in 31 wherein:

• the gate-electrode-defining act includes defining, for an additional FET of opposite polarity to the principal FET, an additional gate electrode above, and vertically separated by an additional gate dielectric layer from, a segment of the semiconductor body intended to be an additional channel zone of the second conductivity type;
• and
• the method further includes introducing semiconductor dopant of the first conductivity type into the semiconductor body to define, for the additional FET, a pair of additional source/drain zones of the first conductivity type laterally separated by the additional channel zone such that, subsequent to completion of fabrication of the structure, (a) the additional channel zone is part of additional body material which is of the second conductivity type and which extends below the additional source/drain zones and (b) all semiconductor dopant of the second conductivity type in the semiconductor body has a concentration that decreases by at least a factor of 10 in moving upward to a specified one of the additional source/drain zones from an additional underlying subsurface body-material location which is no more than 10 times deeper below the upper semiconductor surface than the specified additional source/drain zone.