Fabrication method for semiconductor device having non-uniformly doped channel (NUDC) construction

Abstract

A fabrication method for a semiconductor memory device with a non-uniformly doped channel(hereinafter, called NUDC) formed in a semiconductor substrate with a thin central portion that becomes gradually thicker toward the edges of the substrate. The method includes forming an impurity-bearing layer on a semiconductor substrate, selectively etching the impurity containing layer in a manner such that the portion of the impurity-bearing layer serving as a gate region is formed to be thin at a central portion thereof and gradually thickens as it nears the edges thereof; forming a first conductive impurity region by driving the impurity from the impurity containing layer into the semiconductor substrate, stripping the impurity containing layer, sequentially forming a gate insulating film and a gate electrode on the semiconductor substrate, and forming a second conductive impurity region in the semiconductor substrate at the sides of the gate electrode.

Dependencies are inferred from the claim text.