A semiconductor device has a semiconductor package with a semiconductor element is mounted on a mounting substrate. The mounting substrate has at least two anisotropic areas which are located at both sides of a semiconductor package mounting area in a way to sandwich it and have an anisotropic linear expansion coefficient. In the anisotropic areas, a linear expansion coefficient in a direction toward a center of the semiconductor package mounting area is larger than a linear expansion coefficient in an in-plane direction of the mounting substrate perpendicular to the direction and larger than a linear expansion coefficient of the semiconductor package mounting area in a direction toward the anisotropic areas. The semiconductor device makes it possible to reduce thermal deformation of a semiconductor package mounting area of a mounting substrate easily and at low cost.