Abstract: Various embodiments generally relate to a method for forming a graphene barrier layer for a semiconductor device, and more particularly, to a method of forming a barrier thin film including a graphene layer capable of reducing the contact resistance of a metal interconnect. A method for forming a graphene barrier layer according to an embodiment includes: loading a substrate, which has a titanium-containing layer formed thereon, in a chamber of a substrate processing system, the chamber having a processing space formed therein; inducing nucleation on the titanium-containing layer by supplying a first reactant gas including a unsaturated hydrocarbon into the chamber; and forming a graphene layer on the titanium-containing layer by supplying a second reactant gas including a saturated hydrocarbon into the chamber.