Abstract: A method of coding a ROM from a partially processed semiconductor wafer comprising a substrate, a plurality of spaced regions separated by regions of isolating oxide deposited in said substrate, a layer of gate oxide overlying each of said spaced regions and a gate electrode overlying each layer of said gate oxide, is described comprising the use of photoresist material for preventing the formation of source and drain regions under selected ones of said gate electrodes during a subsequent doping step. The photoresist material restricts the area of implantation of dopant used for forming source and drain regions in the ROM device.