Starting product for the production of a read-only memory and a method of producing it and the read-only memory

A method of forming a ROM from a plurality of coplanar MOS devices, the insulated gates of each of which are connected to a selected one of a plurality of column conductors, each device including a pair of controlled electrodes each in contact with a doped region of a semiconductor, one of the controlled electrodes of each device being connected to a selected one of a plurality of row conductors, the other controlled electrode being grounded, wherein the method comprises:

• rapidly decreasing the cross-sectional area of the controlled electrodes adjacent the doped regions by contacting the electrodes with an etchant which forms an electrochemical cell with the electrode and the doped semiconductor, portions of the electrodes not in contact with the doped regions etching at a slower, chemical rate;
• and then
• applying voltages to selected row and column conductors sufficient to blow selected controlled electrodes.

An improved method of decreasing the cross-sectional area of selected conductors associated with doped semiconductor regions of an array of semiconductive devices, preparatory to blowing out predetermined ones of the selected cross-sectionally decreased conductors by I.sup.2 R heating, wherein the improvement comprises:

• contacting the selected conductors and their associated doped regions with a first etchant which forms an electrochemical cell with the conductors and the regions, to rapidly etch and decrease the cross-sectional area thereof.