FIELD EFFECT TRANSISTOR AND METHOD OF FORMING A FIELD EFFECT TRANSISTOR

摘要

A method of forming a field effect transistor comprises providing a semiconductor substrate, a gate electrode being formed over the semiconductor substrate. At least one cavity is formed adjacent the gate electrode. A strain-creating element is formed in the at least one cavity. The strain-creating element comprises a compound material comprising a first chemical element and a second chemical element. A first concentration ratio between a concentration of the first chemical element in a first portion of the strain-creating element and a concentration of the second chemical element in the first portion of the strain-creating element is different from a second concentration ratio between a concentration of the first chemical element in a second portion of the strain-creating element and a concentration of the second chemical element in the second strain-creating element.