A semiconductor device includes a fin field effect transistor (FinFET). The FinFET includes a channel disposed on a fin, a gate disposed over the channel and a source and drain. The channel includes at least two pairs of a first semiconductor layer and a second semiconductor layer formed on the first semiconductor layer. The first semiconductor layer has a different lattice constant than the second semiconductor layer. A thickness of the first semiconductor layer is three to ten times a thickness of the second semiconductor layer at least in one pair.