An abutment structure comprises a power rail, a ground rail parallel to the power rail, first cells and second cells. An area is defined between the power and the ground rails. A portion of each first and second cell overlaps the power and the ground rails, and another portion thereof is within the area. The first cells are within the abutment structure with original patterns thereof. The second cells respectively has an original pattern and a base pattern being a flip pattern of the original pattern, and are within the area with alternate of the original and the base patterns. The first and the second cells are within the area alternately without overlapping. Alternatively, the first and the second cells may also be within different areas, and the second cells are within different areas respectively with the base pattern and a flip pattern of the base pattern thereof.