The present disclosure provides a semiconductor structure including a semiconductor substrate having a device region and a dummy region adjacent the device region; a plurality of active regions in the device region; and a plurality of dummy active regions in the dummy region, where each of the active regions has a first dimension in a first direction and a second dimension in a second direction perpendicular to the first direction, and the first dimension is substantially greater than the second dimension; and each of the dummy active regions has a third dimension in the first direction and a fourth dimension in the second direction, and the third dimension is substantially greater than the fourth dimension. The plurality of dummy active regions are configured such that thermal annealing effect in the dummy region is substantially equal to that of the device region.