NOVELTY - A solar cell comprises a substrate (1); a buffer layer (2) that is formed on the substrate and is composed of a group-III nitride semiconductor; and a group-III nitride semiconductor layers (p-type layer (50)/n-type layer(51)) that have a p-n junction and are formed on the buffer layer. At least one of the buffer layer and group-III nitride semiconductor layer having the p-n junction has a compound semiconductor layer formed by a sputtering method.    USE - As a solar cell useful for industry.    ADVANTAGE - The solar cell has high photoelectric conversion efficiency. The solar cell is capable of achieving both mass productivity and excellent characteristics. When the buffer layer is formed by a sputtering method, the buffer layer has high uniformity. As a result, when the underlying layer is subsequently formed on the buffer layer, it is possible to reduce the threading dislocation in the underlying layer. In particular, the buffer layer formed by the sputtering method has a thickness smaller than that of the buffer layer formed by an MOCVD method, also has in-plane uniformity higher than that of the buffer layer formed by the MOCVD method. The sputtering method can maintain the substrate at a low temperature. Therefore, even when a substrate formed of a material that is decomposed at a high temperature is used, the sputtering method makes it possible to form a layer on the substrate without damaging the substrate. The use of the manufacturing method and the solar cell element make it possible to increase the area of the solar cell substrate and to considerably reduce manufacturing costs.    DETAILED DESCRIPTION - A solar cell comprises a substrate (1); a buffer layer (2) that is formed on the substrate and is composed of a group-III nitride semiconductor; and a group-III nitride semiconductor layers (p-type layer (50)/n-type layer (51)) that have a p-n junction and are formed on the buffer layer. At least one of the buffer layer and group-III nitride semiconductor layer having the p-n junction has a compound semiconductor layer formed by a sputtering method. The group-III nitride semiconductor layers (p-type layer/n-type layer) having the p-n junction are comprised in a solar cell element. The group-III nitride semiconductor layer is formed of InxGa(1-x)N (80, 81) (where x is 0-1). In the solar cell, an n-type electrode and a p-type electrode are formed on at least a portion of or the entire surface of the group-III nitride semiconductor layer. An INDEPENDENT CLAIM is included for manufacturing the solar cell, involving forming a buffer layer comprising a group-III nitride semiconductor on a substrate using a sputtering method; and forming a group-III nitride semiconductor layer and electrodes on the buffer layer, where group-III nitride semiconductor layer is formed on the buffer layer by at least one selected from the sputtering method, a metal oxide chemical vapor deposition (MOCVD) method, an metal-organic beam epitaxy (MBE) method, a chemical beam epitaxy (CBE) method, and an molecular layer epitaxy (MLE) method, and the electrodes are formed on the group-III nitride semiconductor layer.    DESCRIPTION OF DRAWING(S) - The figure shows a cross-sectional view of the structure of the solar cell element having two junctions of gallium nitride junction layer and indium gallium nitride layer.    Substrate (1)    Buffer layer (2)    p-Type layer (50)    n-Type layer (51)    Indium gallium nitride layers. (80, 81)