Advanced cell structures for dynamic RAMs

Recent major progress in the area of advanced DRAM cell structures is described, focusing on three-dimensional approaches. Cell design criteria are first outlined. Then a number of structures are discussed, namely, the stacked-capacitor cell, the trench-capacitor cell, the substrate-plate trench-capacitor cell, the dielectrically insulated trench cell, the buried stacked-capacitor cell, the folded-capacitor cell, the isolation-merged vertical-capacitor cell, the buried-capacitor or stacked transistor cell, and the trench transistor cell. Future trends in cell structures are projected.>