Transistors with a hybrid source or drain

Abstract

Structures for a field-effect transistor and methods of forming a structure for a field-effect transistor. A gate structure extends over a channel region in a semiconductor body. The gate structure has a first side surface and a second side surface opposite the first side surface. A first source/drain region is positioned adjacent to the first side surface of the gate structure and a second source/drain region is positioned adjacent to the second side surface of the gate structure. The first source/drain region includes a first epitaxial semiconductor layer, and the second source/drain region includes a second epitaxial semiconductor layer. A first top surface of the first epitaxial semiconductor layer is positioned at a first distance from the channel region, a second top surface of the second epitaxial semiconductor layer is positioned at a second distance from the channel region, and the first distance is greater than the second distance.