PURPOSE: To enable a Cd based II-VI compound semiconductor thin film to be recrystallized without doping any needless impurity for enhancing the performances of a device by a method wherein a Cd base II-VI compound semiconductor thin film is deposited on the surface of amorphous substrate or an amorphous thin film which is made rugged and then the whole body is heat treated at specified temperature.

CONSTITUTION: A Cd based II-VI compound semiconductor thin film 2 is deposited on the surface of an amorphous substrate or an amorphous thin film 1 which is made rugged and then the whole body is heat treated at the temperature exceeding 500°C. For example, the surface of a glass substrate 1 is made rugged by sputter etching process. Then, the Cd based II-VI compound semiconductor thin film 2 comprising either CdS, CdSe or solid solution thereof is formed on the substrate 1. Later, the whole body is heat treated at the temperature exceeding 500°C in nitrogen atmosphere to deposit crystalline grains. Then, opposite electrodes 3 are formed to manufacture a photosensor. Through these procedures, the thin film 2 can be recrystallized even if the atmosphere of heat treatment after film formation is not CdCl2 atmosphere thereby enabling the doping of needless impurity to be avoided.