FIG. 9C is a diagram illustrating of the logic cell 912 placed in the mixed-row heights layout system 900 in accordance with some embodiments. When the logic cell 902 is replaced with the logic cell 912, the logic cell 902 may be re-configured into two portions, i.e. 912a and 912b. The two portions 912a and 912b may be placed in the first-type doped rows 906 and 908 respectively. The logic cell 912 is similar to the above mentioned logic cell 512 or 514, thus the detailed description of the logic cell 912 is omitted here for brevity.