A semiconductor device includes a hard mask including a first layer and a second layer in contact with each other and having opposite stress types, wherein a difference between initial stresses of the first layer and the second layer is increased so that after a thermal process, the difference between the final stresses of the first and second layer becomes smaller, to reduce the likelihood of peeling of the first or second layer. The initial stress of the first layer includes a compressive stress and the initial stress of the second layer includes a tensile stress.