the charge trapping dielectric layer 12 note that the etch stop layer 14 is itself optional in that careful selection of subsequent etching processes may obviate the need for a distinct etch stop layer 14 in some instances however if it is found that the etch stop layer 14 is beneficial to the operation of the transistor 10 this layer or some portion thereof may remain part of the structure of the transistor 10 examples of some suitable materials that may form the etch stop layer 14 include but are not limited to titanium nitride and al 2 o 3 a sacrificial layer 16 preferably of silicon nitride is applied over the etch stop layer 14 to act as a hard mask to the extent that the etch stop layer 14 is later removed the total thickness of the sacrificial layer 16 and any remaining portion of the etch stop layer 14 taken together can define the height of the control gate 30 fig3 illustrates the formation of a groove or gap 22 in the sacrificial layer 16 by way of example the groove 22 may be formed by applying a photoresist layer 18 over the sacrificial layer 16 and then exposing the.