Semiconductor devices are provided which have a tensile and/or compressive strain applied thereto and methods of manufacturing. A method of forming a semiconductor structure includes forming sidewalls and spacers adjacent to a gate stack structure, and forming a recess in the gate stack structure. The method further includes epitaxially growing a straining material on a polysilicon layer of the gate stack structure, and in the recess in the gate stack structure. The straining material is Si:C and the gate stack structure is a PFET gate stack structure. The straining material is grown above and covering a top surface of the sidewalls and the spacers.