STRESS ENHANCED MOS TRANSISTOR AND METHODS FOR FABRICATION

摘要

A stress enhanced MOS transistor and methods for its fabrication are provided. In one embodiment the transistor includes a channel region at a surface of a semiconductor substrate. The method includes etching first recesses into the semiconductor substrate adjacent the channel region to define adjacent regions in the semiconductor substrate between the first recesses and the channel region. A first layer of SiGe is epitaxially grown in the first recesses. The method includes etching second recesses through the first layer of SiGe and into the adjacent regions of the semiconductor substrate. Further, a second layer of SiGe is epitaxially grown in the second recesses.