A method of generating an ECO-layout of an ECO base cell includes: generating first and second active area patterns and arranging them on opposite sides of a first axis; generating non-overlapping first, second and third conductive patterns and arranging each of them so as to correspondingly overlap the first and second active area patterns; locating the first conductive pattern between the second and third conductive patterns; generating a first cut-pattern which overlaps corresponding central regions of the second, and third conductive patterns; aligning the first cut-pattern relative to the first axis; generating a fourth conductive pattern; locating the fourth conductive pattern over an area bounded by the first cut-pattern; and expanding the fourth conductive pattern to occupy an area which substantially overlaps a first segment of the first conductive pattern and a first segment of one of the second and third conductive patterns, thereby resulting in the ECO-layout.