Trench mosfet with high cell density

A trench MOSFET comprising:

• a plurality of gate trenches formed in epitaxial layer of a first conductivity doping type and filled with gate conductive layer over gate insulation layer;
• said plurality of gate trenches defining a plurality of mesas, each of said mesas being between every two adjacent said gate trenches;
• a plurality of source regions of a first conductivity doping type formed inside said mesas, each of said source regions having a side portion exposed at a sidewall of each of said gate trenches;
• a first body region of a second conductivity doping type formed between a pair of said gate trenches;
• a second body region of said second conductivity doping type having heavier doping concentration than said first body region, formed inside said mesas and between a pair of said source regions;
• a heavily-doped contact region of said second conductivity doping type on top of each mesa over said source region and said second body region, said heavily-doped contact region having a heavier doping concentration than said second body region;
• and
• a plurality of metal plugs filled into the upper portion of said gate trenches, wherein said plurality of metal plugs is isolated from said gate conductive layer inside said gate trenches;
• and
• a front metal over top surface of said mesas and said plurality of metal plugs.

A Method for making a trench MOSFET comprising:

• forming a plurality of gate trenches within epitaxial layer and filled with gate conductive layer padded by a gate insulation layer;
• implanting with a first body dopant and diffusing said first body dopant to form said first body regions;
• implanting with a second body dopant and diffusing said second body dopant to form said second body regions over said first body regions;
• removing the upper portion of said gate conductive layer;
• removing said gate insulation layer from the top surface of said second body region and from the upper sidewalls of gate trenches;
• depositing a doped insulation layer on top of said gate conductive layer within said gate trenches to form source region;
• etching said insulation layer to a thinner thickness;
• and
• implanting with heavy contact dopant to form said heavily-doped contact region on top of each mesa.