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Abstract

A power trench MOS-gated device includes a heavily doped semiconductor substrate, a doped upper layer of a first conduction type on the substrate, and a trench gate in the upper layer that comprises a conductive material separated from the upper layer by an insulating layer. An enhanced conductivity drain region underlies the trench gate, and a heavily doped source region of the first conduction type and a heavily doped body region of a second and opposite conduction type are disposed at an upper surface of the upper layer. A deep well region of the second conduction type underlies the source and body regions and extends below the trench gate and abuts the enhanced conductivity drain region. A process for forming a power trench MOS-gated device comprises providing a semiconductor substrate having a doped upper layer of a first conduction type. A dopant of a second and opposite conduction type is implanted into an upper surface of the upper layer, thereby forming a well region in the upper layer, and a layer of nitride is deposited on the upper surface. The nitride layer and upper layer are selectively etched to form a trench in the upper layer. The sidewalls and floor of the trench are lined with a thin insulating layer, and a dopant of the first conduction type is implanted through the thin insulating layer on the trench floor, thereby forming an enhanced conductivity drain region in the upper layer underlying the trench floor. The thin insulating layer is removed from the trench, and a layer of gate insulating material is formed on the sidewalls and floors of the trench, which is then substantially filled with a conductive material to form a trench gate. The nitride layer is removed from the upper surface of the upper layer, and the well region in the upper layer is thermally diffused, thereby forming a deep well region in the upper layer. The deep well region extends below the trench gate and abuts the enhanced conductivity drain region. A dopant of the first conduction type is selectively implanted into the upper layer to form a heavily doped source region adjacent to the gate trench, and a dopant of the second conduction type is selectively implanted into the upper layer to form a heavily doped body region adjacent to the source region.

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