US Patent 9673295 Contact resistance optimization via EPI growth engineering

A transistor contact structure and methods of making the same. The method includes forming a first semiconductor layer in a source/drain opening of a substrate, the first layer having a non-planar top surface; forming a second semiconductor layer directly on the first layer, the second layer having a defect density greater than the first layer; and forming a silicide region formed with the second layer, the silicide region having a non-planar interface with the first layer. A portion of the silicide interface may be higher than a top surface of the substrate and another portion may be below.