Method of fabricating a thin film transistor
AssigneeSemiconductor Energy Laboratory Co., Ltd.
InventorsMitsufumi Codama, Noriaki Kondo
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Abstract
A thin film transistor and a producing method therefor having a semiconductor layer which is formed in an islandish form and constitutes a channel forming region, a source region and a drain region, wherein the edge portion of the islandish semiconductor layer is so designed as to be gradually or monotonously thinned toward the edge thereof to prevent the gate insulating film covering the active layer from being thinned at the edge portion of the semiconductor layer. The gate insulating film is also smoothly formed to prevent an electric field concentration phenomenon at the edge portion.
Claims13
A method for forming a thin film transistor comprising the steps of:
- forming a first layer on a semiconductor layer;
- forming a mask pattern on said first layer;
- etching said first layer to form a side recess under said mask pattern on said semiconductor layer;
- and
- anisotropically etching said semiconductor layer with said mask pattern to leave a semiconductor island with a side portion of said semiconductor island being tapered so that thickness of said side portion of said semiconductor island is monotonously decreased toward an end of said side portion of said semiconductor island.
A method for forming a thin film transistor comprising the steps of:
- forming a semiconductor island comprising a channel forming region, a source region and a drain region therein;
- forming a first insulator on a side portion of said semiconductor island;
- and
- forming a gate insulating film on said first insulator and said semiconductor island wherein said gate insulating film directly contacts said semiconductor island at said channel forming region and is formed to cover both said semiconductor island and said first insulator.
A method for forming a thin film transistor comprising the steps of:
- forming on a semiconductor layer a first layer having an etching rate larger than that of said semiconductor layer;
- forming a mask pattern on said first layer;
- etching said first layer to form a side recess under said mask pattern on said semiconductor layer;
- and
- anisotropically etching said semiconductor layer with said mask pattern to leave a semiconductor island with a side portion of said semiconductor island being tapered so that thickness of said side portion of said semiconductor island is monotonously decreased toward an end of said side portion of said semiconductor island.
Dependencies are inferred from the claim text.