Method of making high density ROM, without using a code implant

摘要

A method of fabricating read only memory, (ROM), devices has been developed. This process is accomplished using self-alignment of buried N+ bit lines. Thick field oxides are used for isolation purposes. The programmable cell is obtained by growing a gate oxide in a region in which the thick field oxide has been removed. The non-programmable cells contain thick gate oxides. Polysilicon gate structures are processed to function as the word lines.