a nitrogen atmosphere followed by the deposition of a layer of silicon nitride having a thickness of about 12 to 15 nm and a partial oxidation of the thickness of the deposited layer of nitride in presence of water vapor at a temperature comprised between 900 u00b0 c and 1000 u00b0 c until a dielectric layer of silicon oxide whose thickness may vary between 5 and 20 nm is grown according to a typical sample implementation the rapid thermal nitridization of the polysilicon is conducted at 950 u00b0 c for 90 seconds thereafter silicon nitride is deposited at 780 u00b0 c for 5 minutes using an nh 3 sih 2 cl 2 mixture in a 5 1 ratio by volume producing a 12 nm thick layer oxidation in steam and oxygen at 950 u00b0 c is protracted for 2 hrs causing the growth of a 10 nm thick sio 2 layer the residual thickness of the partially oxidized layer of silicon nitride 12 nm thick as deposited is reduced to about 7 nm after oxidation fig4 bis is an enlarged portion of the cross section of fig4 wherein the resulting stratification is made visible the layer 6a represents the nitridized top portion of the layer of the polysilicon 5 i e of the floating gate the layer 6b represents a residual thickness of the silicon nitride layer deposited over the nitridized layer 6a after oxidation the layer 6c represents a dielectric layer of silicon oxide grown by oxidising a top portion of the thickness of the deposited silicon nitride fig5 deposition of a 34 dummy 34 layer of polysilicon 7 over the dielectric multilayer 6 o n rtn for protecting the so formed isolation multilayer 6 i e the oxidized top layer 6c fig6 formation of a so.