Trench FET with self aligned source and contact
View Patent ↗A trench type power MOSgated device has a plurality of spaced trenches lined with oxide and filled with conductive polysilicon. The tops of the polysilicon fillers are below the top silicon surface and are capped with a deposited oxide the top of which is flush with the top of the silicon. Source regions of short lateral extent extend into the trench walls to a depth below the top of the polysilicon. A trench termination is formed having an insulation oxide liner covered by a polysilicon layer, covered in turn by a deposited oxide.
1. A power semiconductor device comprising:
a semiconductor die, said semiconductor die including a drift region of a first conductivity type;
a channel region of a second conductivity type over said drift region;
a plurality of trenches extending to a depth below said channel region;
gate insulation formed on sidewalls of each trench;
a gate electrode disposed inside each trench;
a silicide body formed over each gate electrode;
an oxide plug comprised of TEOS formed inside each trench and directly on a respective silicide body;
conductive regions of said first conductivity each formed adjacent a respective trench; and
a first contact formed over said die and in electrical contact with each one of said conductive regions of said first conductivity, said first contact extending over said oxide plug, wherein no other insulation is disposed between said oxide plug and said silicide body, and wherein each oxide plug is laterally bound by sidewalls of a respective trench whereby said oxide plug does not extend over said conductive regions.
2. A device according to claim 1 , further comprising a thickened oxide layer at the bottom of each trench.
3. A device according to claim 1 , further comprising a termination region, wherein no conductive region of said first conductivity is present in said termination region.
4. A device according to claim 1 , further comprising a substrate, said drift region being disposed over said substrate, and a second contact in electrical contact with said substrate.
5. A device according to claim 4 , wherein said conductive regions are source regions, said first contact is a source contact and said second contact is a drain contact.
6. A device according to claim 1 , wherein said silicide body is contained within said trench.
7. A device according to claim 1 , wherein said conductive regions and said channel region electrically connect to said first contact on a common plane.