Double gate FET and fabrication process
A method of fabricating a double gate FET on a silicon substrate includes the steps of sequentially epitaxially growing a lower gate layer of crystalline rare earth silicide material on the substrate, a lower gate insulating layer of crystalline rare earth insulating material, an active layer of crystalline semiconductor material, an upper gate insulating layer of crystalline rare earth insulating material, and an upper gate layer of crystalline rare earth conductive material. The upper gate layer and the upper gate electrically insulating layer are etched and a contact is deposited on the upper gate layer to define an upper gate structure. An impurity is implanted into the lower gate layer to define a lower gate area aligned with the upper gate structure. A source and drain are formed in the active layer and contacts are deposited on the source and drain, respectively.
1. A double gate field effect transistor structure comprising:
a single crystal silicon substrate;
a lower gate layer of single crystal rare earth electrically conductive silicide material positioned on the silicon substrate;
a lower gate electrically insulating layer of single crystal rare earth electrically insulating material positioned on the lower gate layer of single crystal rare earth electrically conductive silicide material;
an active layer of single crystal semiconductor material positioned on the lower gate layer of single crystal rare earth electrically insulating material;
an upper gate insulating layer of single crystal rare earth electrically insulating material positioned on the active layer of single crystal semiconductor material;
an upper gate layer of single crystal rare earth electrically conductive material positioned on the upper gate electrically insulating layer;
the upper gate layer and the upper gate electrically insulating layer being formed to define an upper gate structure and a metal contact positioned on the upper gate layer;
an impurity introduced into the lower gate layer of single crystal rare earth electrically conductive silicide material so as to define a lower gate area aligned with the upper gate structure;
a source area and drain area in the active layer; and
metal source and drain contacts positioned on the source area and drain area, respectively.
2. A double gate field effect transistor structure as claimed in claim 1 wherein the electrically conductive layer of single crystal rare earth silicide material includes one of erbium and ytterbium as the rare earth.
3. A double gate field effect transistor structure as claimed in claim 1 wherein the active layer of single crystal semiconductor material includes growing an active layer of single crystal silicon material.
4. A double gate field effect transistor structure as claimed in claim 1 wherein the lower gate electrically insulating layer has a thickness of 10 nm or less.
5. A double gate field effect transistor structure as claimed in claim 1 wherein the upper gate electrically insulating layer has a thickness of 10 nm or less.
6. A double gate field effect transistor structure as claimed in claim 1 wherein the impurity includes oxygen.
7. A double gate field effect transistor structure as claimed in claim 1 further including an electrically conductive via coupled to the lower gate area.
8. A double gate field effect transistor structure as claimed in claim 1 wherein each of the lower gate layer, the lower gate electrically insulating layer, the active layer, the upper gate electrically insulating layer, and the upper gate layer are substantially lattice matched to the single crystal silicon substrate, the lower gate layer, the lower gate electrically insulating layer, the active layer, and the upper gate electrically insulating layer, respectively.