A MRAM storage device comprises a substrate, on/above of which a plurality of word lines, a plurality of bit lines, a plurality of memory cells, and a plurality of isolation diodes are provided. Each memory cell forms a resistive cross point of one word line and one bit line, respectively. Each memory cell is connected to one isolation diode such that a unidirectional conductive path is formed from a word line to a bit line via the corresponding memory cell, respectively. The substrate, at least a part of the word lines or at least a part of the bit lines, and the isolation diodes are realized as one common monocrystal semiconductor block.