Vertical type power mosfet having trenched gate structure
First Claim
1. A power MOSFET comprising:
- a drain layer of a first conductivity type;
a drift layer of the first conductivity type provided on said drain layer;
a base layer of a second conductivity type provided on said drift layer;
a source region of the first conductivity type provided on said base layer;
a gate insulating film formed on an inner wall surface of a trench penetrating the base layer and reaching at said drift layer; and
a gate electrode provided on said gate insulating film inside said trench, wherein said gate insulating film is formed such that a portion thereof adjacent to said drift layer is thicker than a portion thereof adjacent to said base layer, and said drift layer has an impurity concentration gradient higher in the vicinity of said drain layer and lower in the vicinity of said source region along a depth direction of the trench.
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Accused Products
Abstract
A power MOSFET comprising a drain layer of a first conductivity type, a drift layer of the first conductivity type provided on the drain layer, a base layer of a first or a second conductivity type provided on the drift layer, a source region of the first conductivity type provided on the base layer, a gate insulating film formed on an inner wall surface of a trench penetrating the base layer and reaching at the drift layer, and a gate electrode provided on the gate insulating film inside the trench, wherein the gate insulating film is formed such that a portion thereof adjacent to the drift layer is thicker than a portion thereof adjacent to the base layer, and the drift layer has an impurity concentration gradient higher in the vicinity of the drain layer and lower in the vicinity of the source region along a depth direction of trench.
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Citations
33 Claims
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1. A power MOSFET comprising:
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a drain layer of a first conductivity type;
a drift layer of the first conductivity type provided on said drain layer;
a base layer of a second conductivity type provided on said drift layer;
a source region of the first conductivity type provided on said base layer;
a gate insulating film formed on an inner wall surface of a trench penetrating the base layer and reaching at said drift layer; and
a gate electrode provided on said gate insulating film inside said trench, wherein said gate insulating film is formed such that a portion thereof adjacent to said drift layer is thicker than a portion thereof adjacent to said base layer, and said drift layer has an impurity concentration gradient higher in the vicinity of said drain layer and lower in the vicinity of said source region along a depth direction of the trench. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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16. A power MOSFET comprising:
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a drain layer of a first conductivity type;
a drift layer of the first conductivity type provided on said drain layer;
a base layer of the first conductivity type provided on said drift layer;
a source region of the first conductivity type provided on said base layer;
a gate insulating film formed on an inner wall surface of a trench penetrating the base layer and reaching at said drift layer; and
a gate electrode provided on said gate insulating film inside said trench, wherein said gate insulating film is formed such that a portion thereof adjacent to said drift layer is thicker than a portion thereof adjacent to said base layer, and said drift layer has an impurity concentration gradient higher in the vicinity of said drain layer and lower in the vicinity of said source region along a depth direction of the trench.
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31. A method of manufacturing a power MOSFET, comprising:
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epitaxially growing a drift layer of a first conductivity type on a first conductivity type semiconductor substrate used as a drain layer, said drift layer being doped with impurities having a concentration distribution increasing up to said semiconductor substrate;
epitaxially growing a base layer of a second conductivity type on said drift layer;
forming a source region of the first conductivity type on said base layer;
forming a trench penetrating said source region and said base layer to reach at said drift layer; and
forming a trenched gate structure including a gate insulating film and a gate electrode, said gate insulating film having a thin portion facing said base layer and a thick portion facing said drift layer. - View Dependent Claims (32, 33)
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Specification