A method for defining routing tracks to be formed in a target layer above a standard cell semiconductor device, the method comprising: forming a first mandrel, a second mandrel and a third mandrel above the target layer, the second mandrel being arranged between the first mandrel and the third mandrel; providing a first spacer material on at least part of the sidewalls of said mandrels (111, 112, 113), thereby forming a first set of spacers including at least a first spacer on a sidewall of the first mandrel, said sidewall facing the second mandrel, a second and a third spacer (122, 123) on the second mandrel, and at least a fourth spacer on a sidewall of the third mandrel, said sidewall facing the second mandrel; removing said mandrels (111, 112, 113); transferring said first set of spacers into a dummy layer arranged between the target layer and the first set of spacers, thereby forming a set of dummy features including a first, second, third and fourth dummy feature (131, 132, 133, 134) corresponding to said first, second, third and fourth spacer (121, 122, 123, 124), wherein said set of dummy features defines positions of off-centre routing tracks (T1, T2, T3, T4); providing a second spacer material on at least part of the sidewalls of said set of dummy features, thereby forming a second set of spacers, wherein spacers of said second set of spacers fill a gap between said first and second dummy feature (131, 132) and a gap between said third and fourth dummy feature (133, 134), and leave a gap between said second and third dummy feature (122, 123), said gap defining a position of a central routing track; providing a filler material in said gap; removing said second set of spacers; patterning said filler material and said set of dummy features; and patterning the target layer using said patterned filler material and said set of dummy features as a mask. forming a first mandrel, a second mandrel and a third mandrel above the target layer, the second mandrel being arranged between the first mandrel and the third mandrel; providing a first spacer material on at least part of the sidewalls of said mandrels (111, 112, 113), thereby forming a first set of spacers including at least a first spacer on a sidewall of the first mandrel, said sidewall facing the second mandrel, a second and a third spacer (122, 123) on the second mandrel, and at least a fourth spacer on a sidewall of the third mandrel, said sidewall facing the second mandrel; removing said mandrels (111, 112, 113); transferring said first set of spacers into a dummy layer arranged between the target layer and the first set of spacers, thereby forming a set of dummy features including a first, second, third and fourth dummy feature (131, 132, 133, 134) corresponding to said first, second, third and fourth spacer (121, 122, 123, 124), wherein said set of dummy features defines positions of off-centre routing tracks (T1, T2, T3, T4); providing a second spacer material on at least part of the sidewalls of said set of dummy features, thereby forming a second set of spacers, wherein spacers of said second set of spacers fill a gap between said first and second dummy feature (131, 132) and a gap between said third and fourth dummy feature (133, 134), and leave a gap between said second and third dummy feature (122, 123), said gap defining a position of a central routing track; providing a filler material in said gap; removing said second set of spacers; patterning said filler material and said set of dummy features; and patterning the target layer using said patterned filler material and said set of dummy features as a mask.