A semiconductor device preferably includes a metal-oxide semiconductor (MOS) transistor disposed on a substrate, an interlayer dielectric (ILD) layer disposed on the MOS transistor, and a magnetic tunneling junction (MTJ) disposed on the ILD layer. Preferably, a top surface of the MTJ includes a reverse V-shape while the top surface of the MTJ is also electrically connected to a source/drain region of the MOS transistor.