A semiconductor device includes a first insulating layer, a contact plug formed in the first insulating layer, a first etch stop layer over the first insulating layer, a second etch stop layer over the first etch stop layer, a second insulating layer over the second etch stop layer and having a contact opening over the contact plug, and a conductive layer disposed in the contact opening and over the contact plug. The contact opening is substantially free of the second etch stop layer, and the first etch stop layer is present in the contact opening.