A semiconductor device includes a substrate, an array of magnetic tunnel junctions (MTJs), an array of first dummy MTJs, and an array of second dummy MTJs. The substrate includes an array region defined thereon, and the array region includes at least an outermost corner. The array of MTJs is disposed in the array region. The array of the first dummy MTJs is disposed along the outermost corner of the array region. The array of the second dummy MTJs is disposed around the array region and the array of first dummy MTJs.