Trench MOSFET with high cell density
First Claim
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1. 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 front metal over top surface of said mesas and extending into each gate trench, wherein said front metal is isolated from said gate conductive area inside said gate trenches.
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Abstract
A trench MOSFET with high cell density is disclosed where there is a heavily doped contact region on the top surface of mesas between a pair of gate trenches. The present invention can prevent the degradation of avalanche capability when shrinking the device in prior art.
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Citations
22 Claims
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1. A trench MOSFET comprising:
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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 front metal over top surface of said mesas and extending into each gate trench, wherein said front metal is isolated from said gate conductive area inside said gate trenches. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A trench MOSFET comprising:
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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. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16)
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17. A Method for making a trench MOSFET comprising:
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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. - View Dependent Claims (18, 19, 20, 21, 22)
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Specification