The BO-MOS RAM cell

A new structure and its fabrication process of MOS dynamic RAM cells are presented for higher density and potentially higher yield. The buried oxide MOS RAM (BO-MOS RAM) cell consists of a planar MOS transfer gate and a buried storage capacitor of N⁺diffusion. Its operation is identical to that of the conventional one-transistor dynamic RAM cell. The resulting advantages are (a) A cell size of 6F²with the minimum lithographic feature size F is achieved, which is equivalent to one-fifth to one-eighth of the conventional 16 Kbit or 64 Kbit RAM cell. (b) A combination of the smaller cell size and an elimination of the MOS capacitor should result in higher production yield as well as higher packing density in one-transistor dynamic RAM.