A method for fabricating semiconductor device includes the steps of: forming an inter-metal dielectric (IMD) layer on a substrate; forming a metal interconnection in the IMD layer; forming a magnetic tunneling junction (MTJ) on the metal interconnection; forming a top electrode on the MTJ; and forming a trapping layer on the top electrode for trapping hydrogen. Preferably, the trapping layer includes a concentration gradient, in which a concentration of hydrogen decreases from a top surface of the top electrode toward the MTJ.