Semiconductor Structures Employing Strained Material Layers with Defined Impurity Gradients and Methods for Fabricating Same

A method of forming a semiconductor structure comprising:

• forming a substrate having multiple layers;
• forming one or more strained layers over the substrate;
• and
• providing an impurity gradient along an axis orthogonal to a top surface of the one or more strained layers and a bottom surface of the substrate, the impurity gradient having a value equal to zero at the bottom surface of the substrate, having a value equal to zero at a distal zone of the one or more strained layers, and having a peak within one of the substrate multiple layers.

A method comprising:

• doping a substrate with an impurity to form a channel region;
• forming a strained channel layer on a surface of the substrate over the channel region, the strained channel 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 structure over the strained channel layer.