An advantageous further development of the invention provides that the application of the SiO2 layer 11, FIGS. 4-8, and 13, FIGS. 9 and 10, proceeds by means of thermal oxidation after etching of the poly-Si-2 layer, whereby, due to the fact that the layer thickness at the edges becomes relatively large, the degree of the cited insignificant overlapping between ends such as A and B, FIG. 6, is fur