Flat cell mask ROM having compact select transistor structure

摘要

A method of manufacture for flat-cell Mask ROM devices on a silicon semiconductor substrate covered with a first gate oxide layer comprises, forming a first conductor structure on the first gate oxide layer, forming a buried conductive structure within the substrate by ion implantation with a portion thereof in juxtaposition with the first conductor structure, etching away the exposed surfaces of the first gate oxide layer exposing portions of the semiconductor, forming a second gate oxide layer on the surface of the semiconductor, and forming a second conductor structure on the second gate oxide layer.