A process for fabricating a hybrid optical detector, includes the steps of: assembling, via an assembly layer, on the one hand an absorbing structure and on the other hand a read-out circuit, locally etching, through the absorbing structure, the assembly layer and the read-out circuit up to the contacts, so as to form electrical via-holes, depositing a protective layer on the walls of the via-holes, producing a doped region of a second doping type different from the first doping type by diffusing a dopant into the absorbing structure through the protective layer, the region extending annularly around the via-holes so as to form a diode, depositing a metallization layer on the walls of the via-holes allowing the doped region to be electrically connected to the contact.