Trench insulation is used in semiconductor technology, especially MOS technology, in order to isolate components in a substrate electrically from one another given a small width of an insulation region. A longitudinal trench which is completely filled with SiO.sub.2 is mainly used as trench insulation. The depth of the trench generally corresponds approximately to the smallest structure dimension in the respective technology.
Leakage currents in the bulk are prevented by the trench insulation. If insulating layers and conductive layers are arranged on the surface of the trench, then leakage currents may occur at the surface on account of parasitic MOS components. These leakage currents must also be prevented by the trench insulation.
In order to improve the insulation behaviour of the trench insulation, doped regions which prevent the formation of conductive channels are employed in the region of the trench insulation. These doped regions are generally produced by implantation. However, this implantation influences the parameters of the components which are insulated from one another.
It has furthermore been proposed to enlarge the cross-section of the trench in the region of the bottom section of the trench. The components to be insulated are arranged on the surface of the substrate (see German Reference DE 38 09 218 A1).