The present invention makes it possible to obtain: a semiconductor device capable of forming a highly reliable upper wire without a harmful influence on the properties of the magnetic material for an MTJ device; and the manufacturing method thereof. Plasma treatment is applied with reducible NH3 or H2 as pretreatment. Thereafter, a tensile stress silicon nitride film to impose tensile stress on an MTJ device is formed over a clad layer and over an interlayer dielectric film where the clad layer is not formed. Successively, a compressive stress silicon nitride film to impose compressive stress on the MTJ device is formed over the tensile stress silicon nitride film. The conditions for forming the tensile stress silicon nitride film and the compressive stress silicon nitride film are as follows: a parallel plate type plasma CVD apparatus is used; the RF power is set in the range of 0.03 to 0.4 W/cm2; and the film forming temperature is set in the range of 200° C. to 350° C.