doping level as the first conductive region to a conductive material layer overlying the gate oxide layer to be protected the third conductive region the well and the substrate form an n n p diode that protects the gate oxide layer during manufacture of the integrated device from the deposition of the polycrystalline silicon layer that forms the gate regions of the mos elements application_number US 34442699 A description fig1 shows a cross section through a wafer 1 comprising a p type monocrystalline silicon substrate 2 in an initial step of the manufacturing process in particular fig1 shows an ion implant with doping species able to determine an n type conductivity for example phosphorous or arsenic in detail in fig1 substrate 2 having a surface 3 is covered by a sacrifice oxide layer 4 in turn covered by a resist mask 5 arrows 6 show the n type implant which leads to the formation of n type wells 7 in the areas of wafer 1 where protection structures are to be formed only one of these structures can be seen in the figures after the growth of thick field oxide regions 10 a 10 b 10 c in a way known per se the implant of n type doping species is carried out as represented in fig2 by arrows 11 this implant masked by a resist mask 12 leads to the formation of n regions having a first depth in the example shown two n regions are formed one of which is intended to form a cathode region indicated by 13 a and the other is intended to form a cathode contact region indicated by.