Patent ID: 7419863
Filing Date: 2008-09-02
Classification: H01L

Abstract:
1. A method comprising: providing an initial structure in which (a) a subsurface semiconductor region of a first conductivity type adjoins and overlies a subsurface electrically insulating layer, (b) a more lightly doped surface-adjoining semiconductor region of the first conductivity type adjoins and overlies the subsurface semiconductor region, (c) the semiconductor regions are doped with dopant of the first conductivity type such that the dopant of the first conductivity type has a concentration which substantially undergoes a step decrease by at least a factor of 10 in crossing from the subsurface semiconductor region upward into the surface-adjoining semiconductor region, and (e) a lower semiconductor layer adjoins and underlies the subsurface insulating layer; forming a cavity through the semiconductor regions and the subsurface insulating layer down to the lower semiconductor layer whereby (a) a remaining portion of the subsurface semiconductor region constitutes a principal subsurface body-material portion of the first conductivity type and (b) a remaining portion of the surface-adjoining semiconductor region constitutes a more lightly doped precursor principal surface-adjoining body-material portion of the first conductivity type; introducing semiconductor material of a second conductivity type opposite to the first conductivity type into the cavity to create (a) an additional subsurface body-material portion of the second conductivity type extending down to the lower semiconductor layer to form a pn junction and (b) a more lightly doped precursor additional surface-adjoining body-material portion of the second conductivity type, the additional semiconductor portions being doped with dopant of the second conductivity type such that the dopant of the second conductivity type has a concentration which substantially undergoes a step decrease by at least a factor of 10 in crossing from the additional subsurface body-material portion upward into the additional surface-adjoining body-material portion; and providing (a) a pair of principal source/drain zones of the second conductivity type in the precursor principal surface-adjoining body-material portion along its upper surface such that a principal channel zone of the principal surface-adjoining body-material portion laterally separates the principal source/drain zones, (b) a pair of additional source/drain zones of the first conductivity type in the precursor additional surface-adjoining body material portion along its upper surface such that an additional channel zone of the additional body-material portion laterally separates the additional source/drain zones, (c) principal and additional gate dielectric layers respectively above the principal and additional channel zones, and (d) principal and additional gate electrodes respectively above the principal and additional gate dielectric layers respectively above the principal and additional channel zones.