Patent ID: 9209297
Filing Date: 2015-12-08
Classification: H01L

Abstract:
1. 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 an upper portion of the spacers, leaving a lower portion of the spacers and exposing an upper portion of side surfaces of the first poly-silicon; forming a third oxide layer on the upper portion of 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.