Abstract: A semiconductor device having an FET of a trench-gate structure is obtained by disposing a conductive layer, which will be a gate, in a trench extended in the main surface of a semiconductor substrate. The trench is formed on the main surface of the semiconductor substrate with the insulating film formed thereon with a mask; and the side surface of the insulating film is caused to retreat from the upper end of the trench by isotropic etching, whereby a gate insulating film and a conductive layer to be the trench gate are formed in the trench and over the main surface of the semiconductor substrate at the periphery of the trench. Thus, the occurrence of a source offset and damage to the gate insulating film is prevented.

Abstract: Described is a method for fabricating a semiconductor device having an FET of a trench-gate structure obtained by disposing a conductive layer, which will be a gate, in a trench extended in the main surface of a semiconductor substrate, wherein the upper surface of the trench-gate conductive layer is formed equal to or higher than the main surface of the semiconductor substrate. In addition, the conductive layer of the trench gate is formed to have a substantially flat or concave upper surface and the upper surface is formed equal to or higher than the main surface of the semiconductor substrate. Moreover, after etching of the semiconductor substrate to form the upper surface of the conductive layer of the trench gate equal to or higher than the main surface of the semiconductor substrate, a channel region and a source region are formed by ion implantation. The semiconductor device thus fabricated according to the present invention is free from occurrence of a source offset.

Abstract: Described is a method for fabricating a semiconductor device having an FET of a trench-gate structure obtained by disposing a conductive layer, which will be a gate, in a trench extended in the main surface of a semiconductor substrate, wherein the upper surface of the trench-gate conductive layer is formed equal to or higher than the main surface of the semiconductor substrate. In addition, the conductive layer of the trench gate is formed to have a substantially flat or concave upper surface and the upper surface is formed equal to or higher than the main surface of the semiconductor substrate. Moreover, after etching of the semiconductor substrate to form the upper surface of the conductive layer of the trench gate equal to or higher than the main surface of the semiconductor substrate, a channel region and a source region are formed by ion implantation. The semiconductor device thus fabricated according to the present invention is free from occurrence of a source offset.

Abstract: Described is a method for fabricating a semiconductor device having an FET of a trench-gate structure obtained by disposing a conductive layer, which will be a gate, in a trench extended in the main surface of a semiconductor substrate, wherein the upper surface of the trench-gate conductive layer is formed higher than the main surface of the semiconductor substrate and the trench gate conductive layer and gate insulating film are formed in the trench and over the main surface of the semiconductor substrate at the periphery of the trench.