Disclosed is a method for forming a low dielectric layer of a semiconductor device. The method includes the steps of forming a low dielectric polymer layer on a semiconductor substrate and performing an in-situ plasma-assistant surface modification process with respect to the low dielectric polymer layer, thereby forming an adhesion promoter layer on the low dielectric polymer layer. The method prevents a film from being delaminated at an interfacial surface due to film stress or adhesion fault, after processes for forming the low dielectric layer and a low resistance metal wiring have been completed to achieve semiconductor devices operated at a high speed.