Semiconductor structures employing strained material layers with defined impurity gradients and methods for fabricating same

摘要

Semiconductor structures and devices including strained material layers having impurity-free zones, and methods for fabricating same. Certain regions of the strained material layers are kept free of impurities that can interdiffuse from adjacent portions of the semiconductor. When impurities are present in certain regions of the strained material layers, there is degradation in device performance. By employing semiconductor structures and devices (e.g., field effect transistors or “FETs”) that have the features described, or are fabricated in accordance with the steps described, device operation is enhanced.

主权项

1. A method comprising:
forming a dummy gate structure on a channel area of a substrate; forming a source region and a drain region on opposing sides of the channel area in the substrate; after forming the source region and the drain region, removing the dummy gate structure; after removing the dummy gate structure, forming a semiconductor layer on the channel area of the substrate, wherein the semiconductor layer comprises a first concentration of an impurity in a first portion adjacent an interface with the substrate, a second concentration of the impurity in a second portion distal from the interface, and a third concentration in a third portion disposed between the first portion and the second portion, the first concentration being greater than the second concentration, the third concentration being greater than the second concentration; and forming a gate electrode structure over the semiconductor layer.