Semiconductor device and method of fabricating the same

An impurity having a conductivity type same as that contained in a source-and-drain region is implanted to an exposed surface of a gate electrode along a direction inclined to the surface of said semiconductor substrate, while using over-etched sidewalls as a mask, where the gate electrode is implanted both at the top surface and the upper portion of one side face thereof, whereas one of the source-and-drain regions is implanted with the impurity in an amount possibly attained by a single implantation, but the other portion is not implanted or only slightly implanted to a less affective degree.