Semiconductor memory device and method of making it.

摘要

A semiconductor memory device, preferably a PROM or a mask ROM, has MOS transistors (TR) formed in a semiconductor substrate (11), and arranged in rows (R1, R2, R3 and R4) are isolated from each other by a plurality of field insulation films (22) arranged in an island pattern. The MOS transistors aligned in each of the rows have one common gate electrode (40A and 40B) which extends over a row of the field insulation films (22). The MOS transistors aligned in each of the rows have a common first region (17) for forming a drain (36) or a source (37) extending parallel to the common gate electrodes (40A and 40B) and second regions (16) for forming the other of the drain or source are surrounded by a pair of common gate electrodes (40A and 40B) and a pair of field insulation films (22) so that the plurality of second regions are isolated from each other. The edges of the field insulation films (22) and of the common gate electrodes (40A and 40B) facing the common first region (17) are coincident. This can be achieved by using a mask film (26) extending between and covering the region between a pair of common gate electrodes and the part of the common gates not covered by the masking film (26) as masks and carrying out an etching process.