High density trenched DMOS transistor
First Claim
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1. A field effect transistor comprising:
- a substrate of a first conductivity type;
a first drift region of the first conductivity type having a lower dopant concentration than the substrate and formed on the substrate;
a second drift region of the first conductivity type having a dopant concentration intermediate that of the substrate and the first drift region, and overlying the first drift region;
a body region of a second conductivity type and overlying the second drift region;
a conductive gate electrode extending from a principal surface of the body region into the first drift region; and
a source region of the first conductivity type adjacent the conductive gate electrode at the principal surface of the body region.
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Abstract
The cell density of a trenched DMOS transistor is increased by overcoming the problem of lateral diffusion of deep P+body regions. This problem is solved in three versions. In a first version, the deep P+body region is formed using a high energy implant into a single epitaxial layer. In a second version, a double epitaxial layer is used with a somewhat lower but still high energy deep P+body implant. In a third version, there is no deep P+body implant but only the double epitaxial layer is used. The cell density is improved to more than 12 million cells per square inch in each of the three versions.
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7 Claims
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1. A field effect transistor comprising:
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a substrate of a first conductivity type; a first drift region of the first conductivity type having a lower dopant concentration than the substrate and formed on the substrate; a second drift region of the first conductivity type having a dopant concentration intermediate that of the substrate and the first drift region, and overlying the first drift region; a body region of a second conductivity type and overlying the second drift region; a conductive gate electrode extending from a principal surface of the body region into the first drift region; and a source region of the first conductivity type adjacent the conductive gate electrode at the principal surface of the body region. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification