Patent ID: 7381640

Claim:
A method of forming a metal line and a contact plug of a flash memory device, the method comprising the steps of: providing a gate, a first region in which a contact plug through which the gate is exposed will be formed, and a second region in which a contact plug through which a semiconductor substrate is exposed will be formed, the first and second region being formed in the semiconductor substrate in which the gate is formed; forming a first etch-stop film, a first interlayer insulating layer, a second etch-stop film, and a second interlayer insulating film on the resulting surface, patterning the second interlayer insulating film and the second etch-stop film to form a trench for a metal line, and forming an anti-reflection film and a pattern for defining a contact hole on the resulting surface in which the trench is formed; etching the anti-reflection film and the first interlayer insulating layer by performing a first etch process using the pattern as an etch mask, so that first and second holes are formed in the first region and third and fourth holes are formed in the second region, wherein the first and third holes have a similar depth and the second and fourth holes have a similar depth; etching the first interlayer insulating film by performing a second etch process using the pattern as an etch mask, wherein the third and fourth holes have a similar depth; and etching the first etch-stop film by performing a third etch process using the pattern as an etch mask so that the semiconductor substrate is exposed through the third and fourth holes, wherein contact holes in which a contact plug through which the gate is exposed will be formed are defined in the first and second holes, respectively, and contact holes in which a contact plug through which the semiconductor substrate is exposed will be formed are defined in the third and fourth holes, respectively.