Field effect transistor with short channel and manufacturing method therefor

Claim 1

A field effect transistor comprising: a semiconductor substrate of a first conductivity type; source and drain regions of a second conductivity type arranged apart from each other on the substrate; a gate electrode provided on a channel region between the source region and the drain region, whose edge portions superpose on the source region and the drain region; and a channel diffusion region formed along an entire boundary which exists between the drain region and the substrate extending from below the drain region up to and even with a surface of the semiconductor substrate next to a portion of the channel region below the gate electrode such that the channel diffusion region completely separates the drain region from the substrate; wherein one portion of the channel diffusion region separates a side portion of the drain region from the channel region and is doped with an impurity of the first conductivity type more heavily than the substrate in order to suppress a short channel effect; wherein another portion of the channel diffusion region below the drain region has a first conductivity impurity concentration less than an impurity concentration of the substrate.