A three-dimensional folded dynamic RAM in beam-recrystallized polysilicon

A three-dimensional folded one-transistor dynamic RAM circuit consisting of an access transistor in a beam-recrystallized polysilicon layer above a storage capacitor has been fabricated. Large cell capacitance and low transistor leakage are obtained by use of multiple polysilicon layers and by folding the storage capacitor beneath the access transistor. The resulting storage times are longer than 1 min, several orders of magnitude greater than storage times in a previously published nonfolded dynamic RAM in recrystallized polysilicon [1].