Direct access semiconductor storage cell - using MOS transistors and semiconductor capacitance with thin dielectric oxide layer over capacitor zone

摘要

The direct-access, N-channel storage cell, with a silicon gate electrode comprises an MOS transistor and a semiconductor capacitance. It comprises a p-type silicon substrate with a n+ surface zone and a capacitor zone at a distance from the latter. The capacitor zone has a thin dielectric oxide layer, forming the capacitor dielectric, over which is a polycrystalline silicon layer. The latter has an insulating layer which is thicker than the dielectric oxide layer. A channel zone for the MOS transistor lies between the n+ surface zone and the capacitor zone, over which is a thin gate oxide layer, with a second polycrystalline silicon layer over this and over part of the first silicon layer. The second silicon layer has an insulating layer which is thicker than the gate oxide layer, with a conductive layer over the insulating layer connected to the second silicon layer.