PROGRAMMABLE READ-ONLY MEMORY AND METHOD OF PRODUCING SAME

摘要

A semiconductor PROM contains a group of PROM cells (12) each consisting of a pair of opposing diodes oriented vertically with their common intermediate region (22) fully adjoining a recessed oxide insulating region (16). A composite buried layer consisting of buried regions (32) which adjoin the insulating region below the lower cell regions (20) and an opposite-conductivity buried web (44) which laterally surrounds each buried region is employed to improve programming efficiency as well as provide intermediate electrical connections. In fabricating the PROM, the insulating region serves as a mask to control the lateral extent of the dopants utilised to define the diodes. The intermediate cell regions are ion implanted to obtain maximum dopant concentration near their mid-points so as to facilitate manufacture in large arrays.