Disclosed is a method for manufacturing a magnetic storage device comprising a TMR element, which comprises a step for forming an insulting film on an interlayer insulating film provided with a wiring layer, an opening formation step for forming an opening in the insulating film so that the wiring layer is exposed therefrom, a metal layer formation step for forming a metal layer on the insulating layer so that the opening is filled therewith, a CMP step for polishing and removing the metal layer on the insulating layer by a CMP method and forming the metal layer remaining in the opening into a lower electrode, and a step for forming a TMR element on the lower electrode. Also disclosed is a magnetic storage device comprising an interlayer insulating film provided with a wiring layer, an insulating film formed on the interlayer insulating film, an opening formed in the insulating film so that the wiring layer is exposed therefrom, a barrier metal layer provided so as to cover the inner surface of the opening, a lower electrode formed on the barrier metal so as to fill the opening, and a TMR element formed on the lower electrode.