Method of manufacturing a transistor
First Claim
1. A method of manufacturing a transistor having a semiconductor substrate having a drain layer of a first conductivity type and an opposite conductive region of a second conductivity type in contact with the drain layer;
- comprising steps of;
forming a deep trench reaching from a surface of the opposite conductive region to the drain layer in the semiconductor substrate, wherein a bottom of deep trench is positioned in the drain layer;
disposing a semiconductor filler of the second conductivity type on a bottom of the deep trench, wherein top of the semiconductor filler is deeper than a bottom of the opposite conductive region;
forming a gate insulating film on an inner side surface of a gate trench composed of an upper part than the top of semiconductor filler in the deep trench;
forming a gate electrode insulated from the semiconductor filler in the gate trench to contact with the gate insulating film, and forming a source region of the first conductivity type on a surface within the opposite conductive region to contact with the gate insulating film.
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Abstract
A technique for reducing an on-resistance of a transistor is provided. A power MOSFET of the present invention has a semiconductor material which is disposed under a polysilicon gate and composed of polysilicon into which impurities are doped at low concentration. Therefore, a depletion layer is expanded to the inside of the semiconductor material under the polysilicon gate. Since the electric field strengths are uniform from the surface of a drain layer to a depth of the bottom surface of the semiconductor material and a high electric field is not generated at one site, the avalanche breakdown voltage of the transistor is increased. Therefore, the concentration of impurities in drain layer can be made higher than that in a conventional transistor and thereby the on-resistance of the transistor 1 can be reduced.
27 Citations
14 Claims
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1. A method of manufacturing a transistor having a semiconductor substrate having a drain layer of a first conductivity type and an opposite conductive region of a second conductivity type in contact with the drain layer;
- comprising steps of;
forming a deep trench reaching from a surface of the opposite conductive region to the drain layer in the semiconductor substrate, wherein a bottom of deep trench is positioned in the drain layer;
disposing a semiconductor filler of the second conductivity type on a bottom of the deep trench, wherein top of the semiconductor filler is deeper than a bottom of the opposite conductive region;
forming a gate insulating film on an inner side surface of a gate trench composed of an upper part than the top of semiconductor filler in the deep trench;
forming a gate electrode insulated from the semiconductor filler in the gate trench to contact with the gate insulating film, and forming a source region of the first conductivity type on a surface within the opposite conductive region to contact with the gate insulating film. - View Dependent Claims (2, 3, 4, 5, 6, 7)
- comprising steps of;
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8. The method of manufacturing a transistor having
a drain layer of a first conductivity type, an opposite conductive region of a second conductivity type in contact with the drain layer, a gate trench formed on a deeper position than a depth of the opposite conductive region on a surface of the opposite conductive region, a gate insulating film disposed on an inner side surface of the gate trench, a gate electrode disposed on an inside of the gate trench and insulated from the opposite conductive region by the gate insulating film, a source region of the first conductivity type on a surface within the opposite conductive region to contact with the gate insulating film and comprising the steps of: -
forming a deep trench having a deeper depth than a depth of the gate trench, and disposing a semiconductor filler of the second conductivity type on inside of the deep trench, thereby making an upper part than a top of the semiconductor filler into the gate trench. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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Specification