US Patent 7301200 Trench FET with self aligned source and contact

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.