A method for fabricating semiconductor device includes first forming a first magnetic tunneling junction (MTJ) and a second MTJ on a substrate, performing an atomic layer deposition (ALD) process or a high-density plasma (HDP) process to form a passivation layer on the first MTJ and the second MTJ, performing an etching process to remove the passivation layer adjacent to the first MTJ and the second MTJ, and then forming an ultra low-k (ULK) dielectric layer on the passivation layer.