Semiconductor read-only memory with higher density - uses common contacts to word and bit-lines and source diffusion, reduces series resistance with metal- or silicide-layers

摘要

Read-only memory (ROM) device has storage transistors of which the drain- (4d) and source-diffusion (4s) regions are each part of a long diffusion-region which is shared with other storage transistors. The diffusion regions are parallel to each other and are covered with a metal layer, pref a silicide (6), and then with an insulating layer (8), pref. Si-oxide. The surface area not occupied by the diffusions is covered with a gate-oxide layer (10). Gate-electrodes (12) have been formed at a right angle to the diffusions and are pref. formed polycrystalline Si and covered with a refractory metal layer pref a silicide (14). The substrate material used is pref Si. USE/ADVANTAGE: Avoids the use of a contact to any of the 3 electrodes for each cell. This saves a large amt of space, which allows the designs to be densified. Any increase in series resistance of the electrodes is reduced by using metal- or silicide-layers in electrical contact with each of the electrodes.