PURPOSE: To provide an infrared detector, in which the crystallinity of n-type Hg1-xCdxTe layer is not impaired and a manufacturing process is not complicated.

CONSTITUTION: An opening 21B is provided in one region of a semiconductor substrate(Si) 3 covered with an insulating film 6, an intermediate layer 13 composed of a high-resistance compound semiconductor layer containing no impurity atom is provided in the opening 21B from the side of the substrate 3, different compound semiconductor layers 14 and 15 of mutually conductive type are laminated on the intermediate layer 3 so that a photodetection element 2 is provided, the source region 7 and drain region 8 of MOS-type switching element 12 for processing the signal of the photodetection element 2 are provided in another region of the substrate 3, and a gate electrode 11 is provided inside the insulating film 6. An opening 21A is provided in the insulating film 6 on the source region 7 and the compound semiconductor layers 14 and 15 forming the photodetection element 2 and the source region 7 are connected by the compound semiconductor layer 14 forming the photodetection element 2.