Patent ID: 8637370

Claim:
A method comprising: forming a first trench in a substrate, the first trench having a first width; forming a first oxide layer on side surfaces of the first trench; forming a second trench in the substrate, below the first trench, the second trench having a second width less than the first width; forming a second oxide layer on side and bottom surfaces of the second trench; forming spacers on sides of the first and second trenches; removing a portion of the second oxide layer from the bottom surface of the second trench between the spacers; filling the first and second trenches with a first poly-silicon to form a drain region; removing the spacers, exposing side surfaces of the first poly-silicon; forming a third oxide layer on the side surfaces and a top surface of the first poly-silicon; and filling a remainder of the first and second trenches with a second poly-silicon to form a gate region on each side of the drain region.