Process for fabricating double poly high density buried bit line mask ROM

摘要

In accordance with the invention, a double poly process is used to double the memory density of a buried bit line ROM on the same silicon area. In particular the word-line pitch is decreased to increase the cell density in a direction perpendicular to the word lines. The invention uses a self-aligned method for ROM code implantation and a polyplanarization by chemical-mechanical polishing (CMP) to achieve a self aligned double poly word line structure.