The yield of a manufacturing process of a semiconductor device is increased. The productivity of a semiconductor device is increased. A first material layer is formed over a substrate, a second material layer is formed over the first material layer, and the first material layer and the second material layer are separated from each other, so that a semiconductor device is manufactured. In addition, a stack including the first material layer and the second material layer is preferably heated before the separation. The first material layer includes one or more of hydrogen, oxygen, and water. The first material layer includes a metal oxide, for example. The second material layer includes a resin (e.g., polyimide or acrylic). The first material layer and the second material layer are separated from each other by cutting a hydrogen bond. The first material layer and the second material layer are separated from each other in such a manner that water separated out by heat treatment at an interface between the first material layer and the second material layer or in the vicinity of the interface is irradiated with light.