Integrated circuit libraries include a first standard cell having a first left boundary and a first right boundary, and a second standard cell having a second left boundary and a second right boundary. The first standard cell and the second standard cell are of a same cell variant. A first active region in the first standard cell has a different length of diffusion than a second active region in the second standard cell. The first active region and the second active region are corresponding active regions represented by a same component of a same circuit diagram representing both the first standard cell and the second standard cell.