Method of making a high voltage DMOS transistor
First Claim
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1. A process for making a semiconductor device comprising the steps of:
- providing a substrate of a first conductivity type;
covering said substrate with an oxide layer;
forming a polysilicon gate on said oxide layer;
forming an opening in said oxide layer;
subjecting said substrate to a first predeposition of impurity material of a second conductivity type through said opening;
subjecting said substrate to a first diffusion drive-in operation to form a well of said second conductivity type therein through said opening;
subjecting said substrate to a second predeposition and second diffusion drive-in steps of impurity material to form a region in said well through said opening separated from the boundary of said well by a channel zone, said channel zone being formed under said polysilicon gate;
covering said polysilicon gate by a silicon nitride layer during at least said first drive-in step; and
wherein said region forms the source of said device and said substrate forms the drain of said device.
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Abstract
A process for manufacturing a high voltage DMOS (Deep Diffusion Metal Oxide Semiconductor) transistor includes a first ion implantation and drive-in step to form a P-well in a N-substrate, and a second such step to form a N+ region in this well and a channel between this region and the substrate and under a polysilicon gate which is covered with a silicon nitride layer during the first step. By the presence of the latter layer pitting of the gate is prevented and no leakage paths are formed between source and drain.
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Citations
7 Claims
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1. A process for making a semiconductor device comprising the steps of:
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providing a substrate of a first conductivity type; covering said substrate with an oxide layer; forming a polysilicon gate on said oxide layer; forming an opening in said oxide layer; subjecting said substrate to a first predeposition of impurity material of a second conductivity type through said opening; subjecting said substrate to a first diffusion drive-in operation to form a well of said second conductivity type therein through said opening; subjecting said substrate to a second predeposition and second diffusion drive-in steps of impurity material to form a region in said well through said opening separated from the boundary of said well by a channel zone, said channel zone being formed under said polysilicon gate; covering said polysilicon gate by a silicon nitride layer during at least said first drive-in step; and wherein said region forms the source of said device and said substrate forms the drain of said device. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A process for making a semiconductor device comprising the steps of:
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providing a substrate of a first conductivity type; covering said substrate with an oxide layer; forming a polysilicon gate on said oxide layer; forming a first and a second opening in said oxide layer; subjecting said substrate to a first predeposition of impurity material of a second conductivity type through said first opening; subjecting said substrate to a first diffusion drive-in operation to form a well of said second conductivity type therein through said first opening; subjecting said substrate to a second predeposition and second diffusion drive-in steps of impurity material through said second opening to form a region separated from the boundary of said well by a channel zone, said channel zone being formed under said polysilicon gate; covering said polysilicon gate by a silicon nitride layer during at least said first drive-in step; and wherein said region forms the source of said device and said well forms the drain of said device.
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Specification