A method for fabricating semiconductor device includes the steps of: forming a first magnetic tunneling junction (MTJ) and a second MTJ on a substrate; forming a first top electrode on the first MTJ and a second top electrode on the second MTJ; forming a first ultra low-k (ULK) dielectric layer on the first MTJ and the second MTJ; forming a passivation layer on the first ULK dielectric layer, wherein a bottom surface of the passivation layer between the first MTJ and the second MTJ is lower than a top surface of the first MTJ; and forming a second ULK dielectric layer on the passivation layer.