Bi-directional power trench MOS field effect transistor having low on-state resistance and low leakage current
First Claim
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1. A trench MOSFET comprising:
- (a) at least one pedestal, that functions as a vertically-oriented body region, doped with a first conductivity type of dopant, extending in a direction from a top surface to a bottom surface of this MOSFET;
(b) for each of said pedestals;
(b.1) at least one gate region adjacent to a sidewall of said pedestal and extending across substantially the entire sidewall to control conduction of current throughout said pedestal, whereby a voltage applied to said gate region controls a conductivity of said pedestal;
(b.2) an insulating layer, on a sidewall of said pedestal, between said gate region and said pedestal; and
(b.3) at least one charge carrier getter region, of a second conductivity type opposite to the first conductivity type, in electrical contact with said pedestal, whereby, between each pedestal and each charge carrier getter region with which it is in electrical contact, is formed a p-n junction that tends to deplete a charge carrier density within said pedestal;
wherein a dopant concentration in each charge carrier getter region, a dopant concentration of each body region, a width of each charge carrier getter region, a width of each body region, a thickness of each charge carrier getter region and a thickness of each body region are selected to substantially deplete each body region when said trench MOSFET is in an off-state.
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Abstract
A trench MOSFET that includes a charge carrier getter region to substantially deplete a plurality of body regions during an off-state of this MOSFET to produce a very low off-state leakage current. In a first class of embodiments, this charge carrier getter region is a thin layer of material, of opposite conductivity type to that of the body regions, and located between a plurality of gate regions and the body regions. In a second class of embodiments, the gate regions are of opposite conductivity type to the body regions to function as a charge carrier getter region as well as a gate region.
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Citations
10 Claims
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1. A trench MOSFET comprising:
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(a) at least one pedestal, that functions as a vertically-oriented body region, doped with a first conductivity type of dopant, extending in a direction from a top surface to a bottom surface of this MOSFET; (b) for each of said pedestals; (b.1) at least one gate region adjacent to a sidewall of said pedestal and extending across substantially the entire sidewall to control conduction of current throughout said pedestal, whereby a voltage applied to said gate region controls a conductivity of said pedestal; (b.2) an insulating layer, on a sidewall of said pedestal, between said gate region and said pedestal; and (b.3) at least one charge carrier getter region, of a second conductivity type opposite to the first conductivity type, in electrical contact with said pedestal, whereby, between each pedestal and each charge carrier getter region with which it is in electrical contact, is formed a p-n junction that tends to deplete a charge carrier density within said pedestal; wherein a dopant concentration in each charge carrier getter region, a dopant concentration of each body region, a width of each charge carrier getter region, a width of each body region, a thickness of each charge carrier getter region and a thickness of each body region are selected to substantially deplete each body region when said trench MOSFET is in an off-state. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A trench MOSFET comprising:
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(a) at least one pedestal, that functions as a vertically-oriented body region extending in a direction from a top surface to a bottom surface of this trench MOSFET, doped with a first conductivity type of dopant; (b) for each of said at least one pedestal; (b.1) an insulating layer on a sidewall of each of said at least one pedestal; and (b.2) at least one gate region, of opposite conductivity type to that of each of said at least one pedestal, in contact with the insulating layer on a sidewall of each of said at least one pedestal, to control a conductivity of each of said at least one pedestal, the composition and doping of said gate region and said pedestals being selected such that this pedestal is substantially depleted of charge carriers in an off-state of this trench MOSFET;
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Specification