a semiconductor device with a non - uniformly and lightly doped channel comprises a gate electrode formed on a silicon substrate of first conductivity through the intermediary of a gate oxide dielectric film , and an extension of each side walls of the gate electrode composed of a thin polysilicon layer which is substantially thinner than the gate electrode , the silicon substrate having a channel region in which its central part is doped with ions of first conductivity at a concentration higher than in the silicon substrate and its part below the thin polysilicon layer is doped with ions of first conductivity at a concentration higher than in the central part , and having at an outer region of the channel region a source - drain region doped with ions of second conductivity .