TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Method: The method above further comprises between forming a layer to be a tunnel junction and forming a layer to be a second cell, forming a layer to be a third cell having a third band gap lower than the first band gap and higher than the second band gap, on the layer to be the tunnel junction, and forming a layer to be another tunnel junction on the layer to be the third cell by epitaxial growth, where, in forming a layer to be a second cell, the layer to be the second cell is formed on the layer to be another tunnel junction. A compound semiconductor substrate is employed as the semiconductor substrate, the layer to be the first cell, the layer to be the second cell, and the layer to be the third cell are compound semiconductors. A lattice constant of each of the layer to be the first cell and the layer to be the third cell takes a value identical to the lattice constant of the semiconductor substrate. A compound semiconductor substrate is employed as the semiconductor substrate, and the layer to be the first cell and the layer to be the second cell are compound semiconductors. A lattice constant of each of the layer to be the first cell and the layer to be the second cell takes a value identical to the lattice constant of the semiconductor substrate. The method further comprises forming a prescribed intermediate layer by epitaxial growth between the layer to be the first cell and the semiconductor substrate, where separating the layer to be the first cell from the semiconductor substrate includes removing the semiconductor substrate by etching and further removing the intermediate layer. The method further comprises forming a prescribed intermediate layer by epitaxial growth between the layer to be the first cell and the semiconductor substrate, where separating the layer to be the first cell from the semiconductor substrate includes removing the intermediate layer by etching to detach the semiconductor substrate.