The cell structure 314, which may be a rectilinear dual-driver cell structure, comprises a first portion 314a with the height T and the width W_f, a second portion 314b with the height T and the width W_f, and a third portion 314c. The width W_f of the first portion 314a may be different to the width W_f of the second portion 314b. A distance between the first portion 314a and the second portion 314b in vertical direction is S2. A distance between the first portion 314a and the second portion 314b in horizontal direction is D2. The distance S2 is substantially equal to the height S of the standard cell structure 304. The heights T and S2 may be constant heights and the widths W_f and D2 may be variable widths. According to some embodiments, the first portion 314a, the second portion 314b, and the third portion 314c may be formed within a bounding box 314d of the cell structure 314. The width of the bounding box 314d is W2, and the height of the bounding box 314d is H2. According to some embodiments, the width W2 is not less than a total of the width W_f of the first portion 314a, the width W_f of the second portion 314b, and the distance D2. The height H2 is not less than a total of the height T of the first portion 314a, the height T of the second portion 314b, and the distance S2. According to some embodiments, the bounding box 314d is a rectangular boundary, and the first portion 314a and the second portion 314b may be located on the diagonal direction of the bounding box 314d. However, this is not a limitation of the present embodiments. The bounding box 314d may be a polygonal bounding box surrounding the first portion 314a, the second portion 314b, and the third portion 314c. According to some embodiments, the first portion 314a and the second portion 314b may comprise semiconductor elements, e.g. transistors, and the third portion 314c may comprise the interconnecting paths for connecting the semiconductor elements in the first portion 314a and the semiconductor elements in the second portion 314b.