Method of fabricating a mask rom with raised bit-line on each buried bit-line

Abstract

A method of fabricating a mask ROM, in which conductive strips are formed with a cap layer on each of them, then a plurality of spacers are formed on the side-walls of the conductive strips, while the substrate under the spacers are used as the coding regions. The buried bit-lines are formed in the substrate between the spacers, then a two-step coding process is performed, wherein the coding regions at the first and the second side of the conductive strips are selectively doped by a first and a second tilt coding implantation with a first and a second coding mask. After the second mask layer and the cap layer are removed, a conductive layer is formed over the substrate, then the conductive layer and the conductive strips are patterned successively to form a plurality of word-lines and plural gates, respectively.