A semiconductor device and a method of forming the same, the semiconductor device includes a substrate, a gate structure, a first dielectric layer, a second dielectric layer, a first plug and two metal lines. The substrate has a shallow trench isolation and an active area, and the gate structure is disposed on the substrate to cover a boundary between the active area and the shallow trench isolation. The first dielectric layer is disposed on the substrate, to cover the gate structure, and the first plug is disposed in the first dielectric layer to directly in contact with a conductive layer of the gate structure and the active area. The second dielectric layer is disposed on the first dielectric layer, with the first plug and the gate being entirely covered by the first dielectric layer and the second dielectric layer. The two metal lines are disposed in the second dielectric layer.