A semiconductor structure is provided. The semiconductor structure include a substrate and a first dielectric layer having at least one via over the substrate. The first dielectric layer includes a first portion having a first thickness and a second portion having a second thickness greater than the first thickness. The semiconductor structure further includes a second dielectric layer containing at least one first conductive line overlying the first portion of the first dielectric layer and at least one second conductive line overlying the second portion of the first dielectric layer. The at least one first conductive line includes a first conductive portion and a conductive cap, and the at least one second conductive line including a second conductive portion having a top surface coplanar with a top surface of the conductive cap.