In a FinFET integrated circuit design, a combined cell structure contains two single cell structures at a first design hierarchy having fin shapes, the cell structures are placed adjacent to each other. The combined fin shapes of the two single cell structures at the first design hierarchy lead to a violation of a design rule related to fin topology in the overlapping region. A fin generation tool thus decides not to place the fins in the first design hierarchy. The fin generation is delegated another design hierarchy resulting in the generation of a single combined fin for both single cells.