A semiconductor device comprises an array of magnetic cell structures each comprising a magnetic tunnel junction over an electrode on a substrate. Each of the magnetic tunnel junctions includes a magnetic material over the substrate, a first tunnel barrier material over the magnetic material, a second tunnel barrier material over the annealed first tunnel barrier material, and another magnetic material over the second tunnel barrier material. Each magnetic tunnel junction is configured to exhibit a tunnel magnetoresistance greater than or equal to about 180% at a resistance area product of less than about 8 ohm μm2. The semiconductor device also includes another electrode over the another magnetic material. Semiconductor devices including the magnetic tunnel junctions, methods of forming the magnetic tunnel junctions, and methods of forming semiconductor devices including the magnetic tunnel junctions are disclosed.