Trenched DMOS transistor with channel block at cell trench corners
First Claim
1. A trenched transistor cell comprising:
- a substrate of a first conductivity type and defining at least two intersecting trenches;
an insulating layer lining the trenches;
a conductive material filling the trenches;
a source region of the first conductivity type and extending from a principal surface of the substrate adjacent to the trenches into the substrate; and
a body region of a second conductivity type opposite the first type and extending from the principal surface adjacent to the trenches into the substrate;
wherein at a corner of the cell defined by the two intersecting trenches, the source region is spaced apart from the trenches.
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Accused Products
Abstract
A trenched DMOS transistor has improved device performance and production yield. During fabrication the cell trench corners, i.e. the areas where two trenches intersect, are covered on the principal surface of the integrated circuit substrate with a blocking photoresist layer during the source region implant step in order to prevent (block) a channel from forming in these corner areas. Punch-through is thereby eliminated and reliability improved, while source/drain on-resistance is only slightly increased. The blocking of the trench corners creates a cutout structure at each trench corner, whereby the source region does not extend to the trench corner, but instead the underlying oppositely-doped body region extends to the trench corner.
70 Citations
21 Claims
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1. A trenched transistor cell comprising:
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a substrate of a first conductivity type and defining at least two intersecting trenches; an insulating layer lining the trenches; a conductive material filling the trenches; a source region of the first conductivity type and extending from a principal surface of the substrate adjacent to the trenches into the substrate; and a body region of a second conductivity type opposite the first type and extending from the principal surface adjacent to the trenches into the substrate; wherein at a corner of the cell defined by the two intersecting trenches, the source region is spaced apart from the trenches. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A trenched transistor cell comprising:
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a substrate of a first conductivity type and defining at least two intersecting trenches; an insulating layer lining the trenches; a conductive material filling the trenches; a source region of the first conductivity type and extending from a principal surface of the substrate adjacent to the trenches into the substrate; and a body region of a second conductivity type opposite the first type and extending from the principal surface adjacent to the trenches into the substrate; wherein at a corner of the cell defined by the two intersecting trenches, the source region is spaced apart from both of the trenches, and at a side of the cell away from the corner of the cell, the source region is adjacent one of the trenches.
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13. A method of forming a transistor cell comprising:
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providing a semiconductor substrate having a first region of a first conductivity type extending from a principal surface of the substrate; forming at least two trenches in the substrate and extending into the substrate from the principal surface, the trenches intersecting to define a corner of the cell; forming an insulating layer lining the trenches; forming a conductive electrode in the trenches overlying the insulating layer; forming a body region in the substrate having a second conductivity type, the body region extending into the substrate alongside the at least two trenches; forming a masking layer over the principal surface and covering the principal surface at the corner; and forming a source region of the first conductivity type and extending into the substrate from the principal surface alongside the at least two trenches, an extent of the source region being defined by the masking layer, the source region thereby being spaced apart from the corner. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21)
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Specification