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Method for manufacturing semiconductor device comprising oxide semiconductor layer

  • US 9,048,265 B2
  • Filed: 05/20/2013
  • Issued: 06/02/2015
  • Est. Priority Date: 05/31/2012
  • Status: Active Grant
First Claim
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1. A method for manufacturing a semiconductor device, comprising the steps of:

  • forming an oxide semiconductor layer over an insulating surface;

    performing a first treatment so that a resistance of the oxide semiconductor layer is reduced;

    forming a first insulating layer over the oxide semiconductor layer after performing the first treatment;

    forming a sacrificial layer overlapping with a part of the oxide semiconductor layer with the first insulating layer interposed therebetween;

    forming a second insulating layer over the sacrificial layer;

    removing a part of the second insulating layer and a part of the sacrificial layer so that a top surface of the sacrificial layer is exposed and the top surface of the sacrificial layer is substantially flush with a top surface of the rest of the second insulating layer;

    removing the sacrificial layer, thereby forming a third insulating layer which does not cover a part of the first insulating layer;

    performing a second treatment after removing the sacrificial layer;

    forming a conductive layer over the first insulating layer and the third insulating layer after performing the second treatment; and

    forming a gate electrode by processing the conductive layer so that a top surface of the third insulating layer is exposed and a top surface of the processed conductive layer is substantially flush with the top surface of the third insulating layer,wherein the second treatment is performed so that a resistance of only a region in the oxide semiconductor layer is increased,wherein the region does not overlap with the third insulating layer, andwherein the first treatment is performed before forming any layer over and in contact with the oxide semiconductor layer.

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