SEMICONDUCTOR MEMORY DEVICE

摘要

PURPOSE:To improve information holding characteristics by increasing overlapping areas of gate electrodes and upper surfaces of source and drain regions in MISFET's which constitute a flip-flop circuit. CONSTITUTION:N<+> type semiconductor regions 4 constitute switching MISFET's QSW with gate insulation films 5 and gate electrodes 6 and the gate electrodes 6 are formed together with word lines WL. N-type semiconductor regions 7 constitute driving MISFET's QDR of a flip-flop circuit with gate insulation films 8 and gate electrodes 9 and each semiconductor region 7 consists of an N<+> type semiconductor region 7A and an N<++> type semiconductor region 7B which has impurity concentration higher than the region 7A. The N<+> type semiconductor region 7A is provided to make the channel length of the driving MISFET QDR equal to that of the switching MISFET QSW or to those of MISFET's composing peripheral circuits. With this constitution, the overlapping area of the gate electrode 9 and the upper surface of the semiconductor region in the driving MISFET QDR is made to be larger than the area in the switching MISFET QSW.