Transistors with dielectric-isolated source and drain regions
Semiconductor devices and method of forming the same include forming a sacrificial layer on source/drain regions of a semiconductor layer. A reactant layer is formed on the sacrificial layer. The reactant layer and sacrificial layer are annealed to convert the reactant layer to a dielectric layer. Source and drain regions are formed on the dielectric layer.
1. A method of forming a semiconductor device, comprising:
forming a sacrificial layer on source/drain regions of a semiconductor layer;
forming a reactant layer on the sacrificial layer;
annealing the reactant layer and the sacrificial layer to convert the reactant layer to a dielectric layer; and
forming source and drain regions on the dielectric layer.
2. The method of claim 1 , wherein the semiconductor layer is a top surface of a bulk semiconductor substrate.
3. The method of claim 2 , further comprising forming source/drain recesses in the source/drain regions of the semiconductor layer, wherein forming the sacrificial layer comprises forming the sacrificial layer on only a bottom surface of the source/drain recesses.
4. The method of claim 1 , wherein the semiconductor layer is a fin formed from a bulk semiconductor substrate.
5. The method of claim 1 , wherein the sacrificial layer is formed from silicon germanium and the reactant layer is formed from germanium dioxide.
6. The method of claim 5 , wherein annealing the reactant layer and sacrificial layer comprises heating the reactant layer and sacrificial layer to about 600° C. in a gaseous nitrogen environment.
7. The method of claim 5 , wherein the dielectric layer is a silicon dioxide layer.
8. The method of claim 1 , wherein forming the sacrificial layer comprises epitaxially growing the sacrificial layer from the source/drain regions of the semiconductor layer.
9. The method of claim 1 , wherein only part of the reactant layer is converted, further comprising washing away remaining material from the reactant layer.