A method of fabricating a flexible display device. The method includes forming an adhesive layer on a first carrier substrate; laminating a first flexible substrate on the adhesive layer, so that a first separation layer of the first flexible substrate is disposed on the adhesive layer; forming a thin film transistor array on the first flexible substrate; and separating the first carrier substrate from the flexible substrate by directing a laser beam onto the first separation layer. The first separation layer comprises silicon nitride (SiNx) with amounts of nitride A1 and amounts of silicon B1 satisfying 0.18≦{A1/B1}≦0.90.