PURPOSE:To improve the yield and the reliability of an image pickup element by integrally forming the drain electrode of an amorphous silicon thin film transistor and the lower electrode of a photodiode to prevent a line from generating. CONSTITUTION:Source, drain electrode materials are deposited on an insulating substrate 11, then dry etched to form source, drain electrodes 16a, 16b having phosphorus doping amorphous silicon layers 15a, 15b. Then, the active layer 14 and the gate insulating film 13 of a thin film transistor TFT are formed by plasma vapor growth without breaking a vacuum with SiN or SiO2, etching, and patterning. Thereafter, a gate electrode 12 is formed. Then, a metal mask is used to deposit an amorphous silicon thin film 17 of a photodiode D by plasma vapor growth, and a transparent electrode 18, an upper electrode, is sputtered, and patterned.