Forming high voltage complementary semiconductor device (HV-CMOS) with gradient doping electrodes
AssigneeUnited Microelectronics Corp.
InventorMing-Tsung Tung
Life of this patent
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Abstract
A method for fabricating high voltage semiconductor devices having a gradient doping of a drift region which comprises N-well 1 and N-well 2 with two different doping densities. This method results in the lift in device's current drive capability and as well as its breakdown voltage. The method further comprises forming a buried spacer oxide, serving as a point of exertion for the edges of the buried gate electrode. And finally, the extension in channel length and the placement of both the channel and drift regions change to vertical direction, all of those result in a greater reduction in the occupied chip area. These advantages attribute to the formation of a buried gate electrode by trench etching method.
Claims17
A method for forming high voltage semiconductor devices, comprising:
- providing a semiconductor substrate;
- overlaying an oxide layer on top of an exposed surface of said substrate;
- forming a pair of source and drain region, said pair further comprises forming a first doping region within said pair of source and drain region, the conductivity type of a first dopant of said first doping region is opposite to the conductivity type of said substrate;
- forming a second doping region within said pair of source and drain region and on top of said first doping region, the conductivity type of a second dopant of said second doping region is same as the conductivity type of said first doping region, moreover, a doping density of said second doping region is higher than a doping density of said first doping region;
- forming a third doping region within said pair of source and drain region and on top of said second doping region, the conductivity type of a third dopant of said third doping region is same as the conductivity type of said second doping region, moreover, a doping density of said third doping region is higher than the doping density of said second doping region;
- forming a first trench and a second trench inside said substrate and at a same location;
- forming a spacer on top of a sidewall of said first trench;
- forming a gate oxide layer on top of both sidewalls and a bottom surface of said second trench;
- and
- forming a buried gate electrode on top of said gate oxide layer and also filled up said first trench and said second trench, wherein the top surface of said buried gate electrode having almost an equal height as the uppermost surface of said pair of source and drain region.
Dependencies are inferred from the claim text.