Vertical dual gate field effect transistor
View Patent ↗A method of manufacturing provides a vertical transistor particularly suitable for high density integration and which includes potentially independent gate structures on opposite sides of a semiconductor pillar formed by etching or epitaxial growth in a trench. The gate structure is surrounded by insulating material which is selectively etchable to isolation material surrounding the transistor. A contact is made to the lower end of the pillar (e.g. the transistor drain) by selectively etching the isolation material selective to the insulating material. The upper end of the pillar is covered by a cap and sidewalls of selectively etchable materials so that gate and source connection openings can also be made by selective etching with good registration tolerance. A dimension of the pillar in a direction parallel to the chip surface is defined by a distance between isolation regions and selective etching and height of the pillar is defined by thickness of a sacrificial layer.
1. A method of making a semiconductor device including a field effect transistor, said method including steps of
forming a semiconductor pillar in a trench in a body of a first insulating material, said trench extending to a layer of semiconductor material,
forming a layer of a second insulating material on walls of said trench, and
etching a contact opening to said semiconductor material through said first insulating material selectively and adjacent to said second insulating material.
2. A method as recited in claim 1 , including further steps of
forming a gate structure adjacent sides of said pillar,
forming layers and/or sidewalls of selectively etchable materials over said gate structure and said pillar, and
forming contact openings to an end of said pillar and said gate structure by selective etching of said layers at locations above and adjacent said pillar, respectively.
3. A method as recited in claim 1 , including further steps of
defining a height of said pillar by thickness of a layer of sacrificial material.
4. A method as recited in claim 3 , wherein said sacrificial material is germanium oxide.
5. A method as recited in claim 1 , wherein said step of forming said pillar is performed by epitaxial semiconductor growth in a trench.
6. A method as recited in claim 1 , wherein said step of forming said pillar is performed by etching of a layer of semiconductor material.
7. A method as recited in claim 1 , including a further step of
limiting a dimension of said pillar by a distance between isolation structures.