Method of forming vertical field effect transistors with different threshold voltages and the resulting integrated circuit structure
Abstract:
An integrated circuit and method are disclosed. In the method, a stack of sacrificial layers is formed on a semiconductor layer such that a first portion of the stack has an extra sacrificial layer as compared to a second portion. First and second multi-layer fins are etched through the first and second portions and into the semiconductor layer. First and second vertical field effect transistors (VFETs) are formed using the fins. During VFET formation, multiple etch processes are performed to remove the sacrificial layers. The last of these etch processes is a selective isotropic etch process that removes the extra sacrificial layer and etches back first and second upper dielectric spacers on the first and second multi-layer fins. Due to the extra sacrificial layer, the first upper dielectric spacer will be taller than the second and the first VFET will have a higher threshold voltage than the second.
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