Semiconductors of different types are formed by a crystal growth technique and joined at the interface at which rapid atomic-layer-level compositional changes occur while maintaining high crystallinity of the semiconductor layers so as to form a heterogeneous PN junction. A layered film that includes a PN junction oxide thin film is formed on a single crystal substrate. The PN junction oxide thin film is constituted by an N-type semiconductor oxide thin film and a P-type semiconductor oxide thin film that are epitaxially grown to have c-axis orientation represented by (00k).