Semiconductor device equipped with a field effect transistor having a

Abstract

Disclosed is a semiconductor device, and method of manufacture thereof, the device having a conductive layer formed on a semiconductor substrate, with an insulating layer interposed between the substrate and conductive layer, and wherein a dense insulating layer is disposed at the sides of the conductive layer so as to cover the sides of the insulating layer on the substrate, the dense insulating layer acting to increase retention of charge in the conductive layer. The conductive layer can be the floating gate of a field effect transistor, with a control gate formed on the floating gate via another insulating layer whose sides can also be covered by the dense insulating layer. Such field effect transistor, having the floating gate, can be used as the memory cell of an EPROM, with the charge being the data stored in the cell. A field effect transistor of a peripheral circuit of the EPROM can also have the dense insulating layer applied so as to cover the sides of the gate oxide layer thereof.