Transistor and transistor manufacturing method

Abstract

In a transistor of the invention, at a boundary between gate oxideformed on a silicon substrateof a device formation regionand a device isolation filmadjoining the gate oxide, a thickness D' of the gate electrodeis set larger than a uniform thickness D of the gate electrodeon the gate oxide. A height difference A between a surface of the gate oxideand a surface of the device isolation film, a width B of a step portionof the device isolation film, and the thickness D of the gate electrodein its uniform-thickness portion satisfy relationships that D>B and A/D+(1−(B/D))>1. By ion implantation via the gate electrodeand the gate oxide, an impurity is added into a surface portion of the silicon substrateat an end portionof the device formation region, the impurity having concentrations higher than in the surface portion of the silicon substratein the electrode uniform portionof the device formation region. The transistor can be prevented from occurrence of the inverse narrow channel effect and kink characteristics, thus being suitable for scale-down of LSIs, and yet can be manufactured with less steps.