A semiconductor device comprises a first semiconductor chip comprising a first substrate. A first magnetic tunnel junction is on the first substrate. A second semiconductor chip comprises a second substrate. A second magnetic tunnel junction is on the second substrate. The second semiconductor chip is positioned on the first semiconductor chip to form a chip stack. A first critical current density required for magnetization reversal of the first magnetic tunnel junction is different than a second critical current density required for magnetization reversal of the second magnetic tunnel junction.