Method for silicon island formation

A method of manufacturing a silicon-on-insulator device, comprising the steps of:

• (1) forming a resist pattern over a silicon substrate to designate a plurality of silicon islands;
• (2) anisotropically etching the structure resulting from step (1) to form the plurality of designated silicon islands from the silicon substrate and forming thereby a passivation layer on the sides of the silicon islands;
• (3) performing isotropic etching, using only a deposition film formed on the sides of the islands during said anisotropic etching step as a protective mask of the sides of the islands, on the structure resulting from step (3) to a depth which creates a thin foot region beneath each of the silicon islands formed in step (2);
• and
• (4) removing the deposition film from the structure resulting from step (3);
• and
• (5) oxidizing the structure resulting from step (4) to form an oxidation layer on the sides of the islands and the thin foot regions, while leaving the inner portion of the thin foot regions to be a non-oxidized portion.

A method of manufacturing a semiconductor device, comprising the steps of:

• forming a resist pattern over a semiconductor substrate to designate a plurality of islands;
• anisotropically etching the structure, resulting from said forming step, to form the plurality of designated islands from the semiconductor substrate;
• isotropically etching the structure resulting from said anisotropically etching step, using only a deposition film formed on the sides of the islands in said anisotropically etching step as a protective mask of the sides of the islands, and stopping said isotropically etching step thereby leaving a plurality of thin foot regions each of which connects one of the plurality of islands formed in said anisotropically etching step to the semiconductor substrate;
• oxidizing the structure resulting from said removing step to form a thermal oxidation layer on the sides of the islands and the thin foot regions, said oxidizing step being controlled so as to leave the inner portion of the thin foot regions to be a non-oxidized portion which provides a conductive charge drain interface between each of the plurality of islands and the semiconductor substrate.