Patent ID: 8304835
Filing Date: 2012-11-06
Classification: H01L

Abstract:
1. A semiconductor structure comprising: first and second well regions of body material of a semiconductor body having an upper surface, the body material doped with semiconductor dopant of a first conductivity type so as to be of the first conductivity type; and first and second zones of a second conductivity type opposite to the first conductivity type situated in the semiconductor body along its upper surface, the first and second well regions respectively extending below the first and second zones and respectively meeting the first and second zones so as to respectively form first and second pn junctions with the first and second zones such that (a) each pn junction reaches a maximum depth below the body's upper surface, (b) the dopant of the first conductivity type is present in both zones and has a concentration which locally reaches first and second subsurface maximum concentrations at respective first and second subsurface maximum concentration locations situated respectively in the first and second well regions and respectively extending laterally below the first and second zones, (c) the first and second subsurface maximum concentration locations occur no more than 10 times deeper below the body's upper surface respectively than the maximum depths of the first and second pn junctions, and (d) the concentration of the dopant of the first conductivity type (i) decreases by at least a factor of 10 in moving upward from the first subsurface maximum concentration location along a selected first vertical location through the first zone to the body's upper surface, (ii) decreases substantially monotonically by less than a factor of 10 in moving from the first subsurface maximum concentration location along the first vertical location to the first pn junction, and (iii) reaches at least one additional subsurface maximum concentration in moving upward from the second subsurface maximum concentration location along a selected second vertical location through the second zone to the body's upper surface.