In a method of forming a contact structure, a first insulation layer including a first contact hole is formed on a substrate. A metal layer including tungsten is formed to fill the first contact hole. A planarization process is performed on the metal layer until the first insulation layer is exposed to form a first contact. A second contact is grown from the first contact. The second contact is formed without performing a photolithography process and an etching process to prevent misalignments.