Method to control source/drain stressor profiles for stress engineering

摘要

A strained channel transistor structure and methods of forming a semiconductor device are presented. The transistor structure includes a strained channel region having a first semiconductor material with a first natural lattice constant. A gate dielectric layer overlying the strained channel region, a gate electrode overlying the gate dielectric layer and a source region and drain region oppositely adjacent to the strained channel region are provided. One or both of the source region and drain region include a stressor region having a second semiconductor material with a second natural lattice constant different from the first natural lattice constant. The stressor region has graded concentration of a dopant impurity and/or of a stress inducing molecule.