Abstract: A PMOS device comprises a semiconductor-on-insulator (SOI) substrate having a layer of insulating material over which is provided an active layer of n-type semiconductor material. P-type source and drain regions are provided by diffusion in the n-type active layer. A p-type plug is provided at the source region, which extends through the active semiconductor layer to the insulating layer. The plug is provided so as to enable the source voltage applied to the device to be lifted significantly above the substrate voltage without the occurrence of excessive leakage currents.

Abstract: In high-voltage devices comprising a lightly doped region (3) provided with a heavily doped contact zone 4, damage caused by local breakdown at the corner of the contact zone may occur as a result of the Kirk effect at a high current density. To improve the robustness of the device, an annular protection zone (14) of the same conductivity type is provided so as to surround the contact zone at a small distance. As a result, breakdown will occur initially at the corner of the protection zone. However, due to the resistance between the protection zone and the contact zone, a more uniform current distribution is obtained, which prevents damage caused by local current concentration.