A semiconductor device includes a first magnetic tunneling junction (MTJ) and a second MTJ on a substrate, a first ultra low-k (ULK) dielectric layer on the first MTJ and the second MTJ, a passivation layer on the first ULK dielectric layer, and a second ULK dielectric layer on the passivation layer. Preferably, the first ULK dielectric layer includes a first thickness, the passivation layer between the first MTJ and the second MTJ includes a second thickness, the passivation layer on top of the first MTJ includes a third thickness, and the second thickness is greater than the third thickness