US 11,721,755 B2
Methods of forming semiconductor power devices having graded lateral doping
Philipp Steinmann, Durham, NC (US); Edward Van Brunt, Raleigh, NC (US); Jae Hyung Park, Apex, NC (US); and Vaishno Dasika, Morrisville, NC (US)
Assigned to Wolfspeed, Inc., Durham, NC (US)
Filed by Wolfspeed, Inc., Durham, NC (US)
Filed on Feb. 11, 2022, as Appl. No. 17/669,409.
Application 17/669,409 is a continuation of application No. 16/892,604, filed on Jun. 4, 2020, granted, now 11,282,951.
Prior Publication US 2022/0165876 A1, May 26, 2022
Int. Cl. H01L 29/78 (2006.01); H01L 29/16 (2006.01)
CPC H01L 29/7802 (2013.01) [H01L 29/1608 (2013.01); H01L 29/7833 (2013.01)] 26 Claims
OG exemplary drawing
 
1. A method of forming a semiconductor device, comprising:
providing a drift layer on a substrate, the drift layer comprising a surface opposite the substrate;
implanting ions into the drift layer to form a source/drain region in an upper portion of the drift layer that has a first portion that has a first dopant dose and a second portion in the first portion, the second portion having a second dopant dose, different from the first dopant dose;
forming a gate dielectric layer on the drift layer; and
forming a gate electrode on the gate dielectric layer, the gate electrode is entirely above the surface of the drift layer,
wherein a portion of the gate dielectric layer has a bottom surface that is closer to the substrate than a top surface of the first portion of the source/drain region.