Method of forming source and drain of a field-effect-transistor and structure thereof

Abstract

A semiconductor fabrication method involving the use of eSiGe is disclosed. The eSiGe approach is useful for applying the desired stresses to the channel region of a field effect transistor, but also can introduce complications into the semiconductor fabrication process. Embodiments of the present invention disclose a two-step fabrication process in which a first layer of eSiGe is applied using a low hydrogen flow rate, and a second eSiGe layer is applied using a higher hydrogen flow rate. This method provides a way to balance the tradeoff of morphology, and fill consistency when using eSiGe. Embodiments of the present invention promote a pinned morphology, which reduces device sensitivity to epitaxial thickness, while also providing a more consistent fill volume, amongst various device widths, thereby providing a more consistent eSiGe semiconductor fabrication process.