A method of manufacturing a semiconductor device includes: providing a semiconductor having active regions; depositing a dielectric layer on the semiconductor; forming a patterned etch mask on the dielectric layer; depositing a further dielectric layer on the dielectric layer and the patterned etch mask; planarizing the further dielectric layer until the patterned etch mask is exposed; and forming a further patterned etch mask having an opening on the further dielectric layer so that portions of the patterned etch mask are exposed from the opening.