A method includes forming a circuit region over a substrate. The circuit region includes at least one active region extending along a first direction, and at least one gate region extending across the at least one active region and along a second direction transverse to the first direction. At least one first input/output (TO) pattern and at least one second TO pattern are correspondingly formed in different first and second metal layers to electrically couple the circuit region to external circuitry outside the circuit region. The at least one first TO pattern extends along a third direction oblique to both the first direction and the second direction. The at least one second TO pattern extends along a fourth direction oblique to both the first direction and the second direction, the fourth direction transverse to the third direction.