Method for manufacturing a semiconductor device

A method of manufacturing a semiconductor device comprising:

• removing portions of a substrate to form isolation trenches;
• forming an oxide layer on sidewalls and bottom faces of the isolation trenches;
• forming a liner nitride layer on the oxide layer;
• depositing an insulating layer on the liner nitride layer, the insulating layer having a thickness sufficient to fill the isolation trenches;
• removing upper portions of the insulating layer, the liner nitride layer and the oxide layer to expose surface portions of the substrate and to form isolation trench structures;
• forming a first channel trench by removing an upper portion of the substrate between adjacent isolation trench structures, the formation of the first channel trench leaving residual substrate regions adjacent the isolation trench structure;
• oxidizing the residual substrate regions to form peripheral oxide regions, the oxidation consuming substantially all of the residual substrate regions;
• removing the peripheral oxide regions to form a second channel trench having as a lower boundary a primary lower substrate surface;
• forming a gate oxide layer on the primary lower substrate surface;
• forming a gate electrode on the gate oxide layer;
• and
• wherein removing the peripheral oxide regions includes removing a portion of the oxide layer lying below a plane defined by the primary lower substrate surface and forming a peripheral lower substrate surface adjacent to and recessed relative to the primary lower substrate surface.