The present invention presents a semiconductor device (10) which is adapted to a solar cell, and in which a semiconductor element (1) is produced by forming one flat surface (2) on a spherical or substantially spherical silicon single crystal (1a, 1b). A diffusion layer (3) and a substantially spherical pn junction (4) are formed on this semiconductor element (1), and a diffusion-mask thin film (5) and a positive electrode (6a) are formed on the flat surface (2). A negative electrode 6b is formed at the apex on the opposite side to the positive electrode (6a), and an antireflection film (7) is formed on the surface side of the diffusion layer (3).