Method of manufacturing semiconductor device are provided including forming an insulation layer having a pad on a substrate; forming an etch stop layer on the insulation layer and the pad; forming a mold structure having at least one mold layer on the etch stop layer; forming a first supporting layer on the mold structure; etching the first supporting layer and the mold structure to form a first opening exposing the etch stop layer; forming a spacer on a sidewall of the first opening; etching the etch stop layer using the spacer as an etching mask to form a second opening, different from the first opening, exposing a first portion of the pad having a first associated area; etching the etch stop layer using the spacer as an etching mask to form a third opening exposing a second portion of the pad having a second associated area, the second associated area being larger than the first associated area; and etching the mold structure to form a fourth opening having a width larger than a width of the third opening.