Patent ID: 7351667

Claim:
A method of manufacturing a semiconductor device, comprising: forming a first contact pad and a second contact pad on a substrate; forming a conductive structure including a metal suicide layer pattern electrically connected to the second contact pad; forming a silicon oxide layer including different silicon oxides on the substrate to cover the conductive structure, the silicon oxide layer including a first opening exposing the first contact pad; etching the silicon oxide layer using an etching solution for etching the different silicon oxides with an etching selectivity while preventing damage to the metal silicide layer pattern to form a second opening which is wider than the first opening; and forming a contact plug in the second opening, the contact plug having a lower portion which is wider than an upper portion, wherein the etching solution comprises about 0.2 to about 5.0 percent by weight of a hydrogen fluoride solution, about 0.05 to about 20.0 percent by weight of an ammonium fluoride solution, about 40.0 to about 70.0 percent by weight of an alkyl hydroxide solution and water.