The invention relates to semiconductor devices for conversion of the ionizing radiation into an electrical signal enabling determination of the radiation level and absorbed dose of gamma, proton, electronic and alpha radiations being measured. The ionizing radiation sensor is a p-i-n structure fabricated by the planar technology. The sensor contains a high-resistance silicon substrate of n-type conductivity, on whose front side there are p-regions; layer from SiO2; aluminum metallization; and a passivating layer. P-region, located in the central part of the substrate and occupying the most surface area, forms the active region of the sensor. At least two p-regions in the form of circular elements are located in the inactive region on the perimeter of the substrate around the central p-region and ensure a decrease in the surface current value and smooth voltage drop from the active region to the device perimeter.