Semiconductor memory device with electrical write-in and erasure, e.g. flash EEPROM - has insulating film of greater thickness than gate insulating layer applied to source and gate diffusion zones

摘要

The memory device has 2 zones (6, 7) of opposite type formed in the surface of a doped substrate (1) with a channel region between them carrying an insulating film (2) of given thickness, a second insulating film (15) of greater thickness applied to one of the opposite conductivity zones. A charge storage electrode (3) is applied over both insulating films, with a further insulating film between the charge storage electrode and the control electrode (5). Pref., the second insulating film comprises a nitride film, applied to source and drain diffusion layers (6, 7) to enclose the first insulating film, the floating gate charge storage electrode (3) overlapping the nitride film. ADVANTAGE - Prevents bird's beak oxide film formation in gate insulating layer.