Multiple work function nanosheet field effect transistor using sacrificial silicon germanium growth
A method of forming a semiconductor device that includes forming a stack of nanosheets composed of a semiconductor material; and forming a sacrificial layer of a work function adjusting material on the semiconductor material of the stack of nanosheets. In a following step, the work function adjusting material is mixed into the semiconductor material on at least a channel surface of nanosheets. The sacrificial layer is removed. An interfacial oxide layer is formed including elements from the semiconductor material and the work function adjusting layer on said at least the channel surface of the stack of nanosheets. A gate structure including a gate dielectric is formed on the interfacial oxide that is present on the channel surface of the nanosheets.
1. A method of forming a semiconductor device comprising:
forming a stack of nanosheets composed of a semiconductor material;
forming a sacrificial layer of a work function adjusting material including germanium on the semiconductor material of the stack of nanosheets;
intermixing the work function adjusting material into the semiconductor material on at least a channel surface of nanosheets in said stack of nanosheets;
removing the sacrificial layer of the work function adjusting material;
forming an interfacial oxide including elements from the semiconductor material and the work function adjusting layer on said at least the channel surface of the stack of nanosheets; and
forming a gate structure including a gate dielectric on the interfacial oxide that is present on the channel surface of the nanosheets;
wherein the semiconductor material of the stack of nanosheets is a silicon containing material; and
wherein the sacrificial layer of the work function adjusting material comprises silicon germanium containing material.
2. The method of claim 1 , wherein the germanium content of the silicon germanium (SiGe) is greater than 35%.
3. The method of claim 1 , wherein said intermixing the work function adjusting material into the semiconductor material on at least the channel surface of said nanosheets in said stack of nanosheets comprises thermal annealing.
4. The method of claim 1 , wherein said removing the sacrificial layer of the work function adjusting material comprises an etch process that is selective to the semiconductor material of the stack of nanosheets.
5. The method of claim 1 , where said forming the interfacial oxide including the elements from the semiconductor material and the work function adjusting layer comprised introducing the stack of nanosheets to an oxygen including atmosphere.
6. The method of claim 1 , wherein the work function adjusting material produces up to a 200 mV shift in the threshold voltage of the semiconductor device.