Method for forming a trench element separation structure, a trench element separation structure and their use in a DRAM memory cell structure

摘要

There is provided a method for forming a trench type element isolation structure wherein no recess develops in the edge part of an imbedded oxide film of a trench type element isolation.Thermal oxidation films having higher etching resistance than the CVD film are formed not only on the surroundings of the imbedded oxide film inside the groove formed on the silicon substrate but also on the lateral sides of the imbedded oxide film projecting upward from the silicon substrate surface.