MOSFET structure and fabrication process implemented by forming deep and narrow doping regions through doping trenches

A MOSFET device formed in a substrate includes a plurality of vertical cells each includes a source, a drain, and a channel for conducting source-to-drain current therethrough across a body region wherein each of said vertical cells being surrounded by a polysilicon layer acting as a gate for controlling said source-to-drain current through said channel, said MOSFET device further comprising:

• a plurality of doping trenches filled with a trench-filling material;
• a plurality of deep-doped regions disposed underneath said doping trenches wherein each of said deep-doped regions extends downwardly to substantially a total depth of an implant depth of said deep-doped region and a vertical diffusion depth below a bottom of a corresponding doping trench whereby each of said deep-doped regions defining a buried region disposed below said body region;
• and
• each of said doping trenches included an insulation layer insulating said trench filling material from said substrate and said doping trench is employed only for implanting dopant ions there through and serving no active electrical function.

A vertical power transistor cell formed in a substrate includes a source, a drain, and a channel for conducting source-to-drain current therethrough across a body region wherein said vertical cell being surrounded by a polysilicon layer acting as a gate for controlling said source-to-drain current through said channel, said power transistor cell further comprising:

• a doping trench filled with a trench-filling material wherein said doping trench includes an insulation layer insulating said trench filling material from said substrate and said gate, and said doping trench is employed only for implanting dopant ions therethrough and serving no active electrical functions;
• a deep-doped region disposed underneath said doping trench wherein said deep-doped region extends downwardly to substantially a total depth of an implant depth of said deep-doped region and a vertical diffusion depth below a bottom of said doping trench whereby said deep-doped region defining a buried region disposed below said body region;
• and
• a lower deep-doped region disposed lower than said deep-doped region wherein said lower deep doped region is doped with impurities of a different conductivity type than a conductivity type of said deep-doped region.