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Manufacturing method of semiconductor device

  • US 8,778,729 B2
  • Filed: 07/28/2011
  • Issued: 07/15/2014
  • Est. Priority Date: 08/05/2010
  • Status: Active Grant
First Claim
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1. A manufacturing method of a semiconductor device comprising the steps of:

  • forming an insulating film over a surface of a substrate;

    forming a first mask over the insulating film;

    performing a slimming process on the first mask, so that a second mask is formed;

    performing an etching process on the insulating film using the second mask, so that an insulating layer is formed;

    forming an oxide semiconductor layer covering the insulating layer;

    forming a conductive film covering the oxide semiconductor layer;

    performing a polishing process on the conductive film, so that a surface of the conductive film is flattened;

    performing an etching process on the conductive film, so that a conductive layer is formed and a surface of the conductive layer is lower than a surface of an uppermost part of the oxide semiconductor layer;

    forming a gate insulating film in contact with the conductive layer and the oxide semiconductor layer; and

    forming a gate electrode in a region which is over the gate insulating film and overlaps with the insulating layer.

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