The present disclosure provides one embodiment of a semiconductor structure. The semiconductor structure includes a semiconductor substrate having a n-type doped well (N-well) and a p-type doped well (P-well) disposed side by side; a first fin active region extruded from the N-well of the semiconductor substrate; a second fin active region extruded from the P-well of the semiconductor substrate; a first isolation feature formed on the N-well and the P-well and laterally contacting the first and second fin active regions, the first isolation feature having a first width; and a second isolation feature inserted between the N-well and the P-well, the second isolation feature having a second width less than the first width.