Method for fabricating semiconductor device by damascene process

A method for fabricating a semiconductor device, the method comprising:

• forming a plurality of isolation patterns, isolated from each other by a plurality of trenches, over an underlying structure;
• forming a plurality of conductive lines filled in the trenches;
• forming contact holes by removing first portions of the isolation patterns, wherein the contact holes are defined by the plurality of conductive lines and second portions of the isolation patterns that remain after removing of the first portions of the isolation patterns;
• and
• forming plugs filled in the contact holes,
• wherein the isolation patterns are in the form of lines, each consisting of a stack of a first layer and a second layer that has an etch selectivity with respect to the first layer.