NOR-TYPE ROM PROVIDED WITH LDD CELL

摘要

PURPOSE: To obtain a ROM matrix whose cell has the junction of diffused parts with concentration gradients by a method wherein ions sufficient to reverse the conductivity-type of a part of a drain region are implanted and diffused and the drain region is decoupled from a channel region. CONSTITUTION: A gate oxide layer 2, a single cell gate electrode 3 and drain regions 4 and 5 are formed in a semiconductor substrate region 1 having the p-type conductivity. A part of the drain area of a programming cell to which a current is not applied is restricted by a photoresist mask M1. Phosphorus ions are diffused through the aperture of the photoresist mask M1 and boron ions are implanted. The conductivity type of a region 6 between programming channel and drain regions is reversed. Then a photoresist mask M2 is formed, drain area of the memory cell is masked and arsenic ions are implanted through the aperture.