A method for fabricating a semiconductor device includes the steps of first forming a first inter-metal dielectric (IMD) layer on a substrate and a metal interconnection in the first IMD layer, forming a magnetic tunneling junction (MTJ) and a top electrode on the metal interconnection, forming a spacer adjacent to the MTJ and the top electrode, forming a second IMD layer around the spacer, forming a cap layer on the top electrode, the spacer, and the second IMD layer, and then patterning the cap layer to form a protective cap on the top electrode and the spacer.