Semiconductor silicon detectors are used in many applications for detection and imaging of ionizing radiation. Detection of neutrons is also possible with these devices. However, the silicon detectors must be adapted for the thermal neutron detection and imaging. The devices must be supplemented with a material which “converts” neutrons into a radiation detectable directly in the semiconductor detector. The principle of the thermal neutron detection with semiconductor silicon detectors is explained. Advantages of such detectors are shown as well as their limitations. The way of the detector improvement using 3D detector technologies is described. The 3D detector properties were simulated; real 3D structures were fabricated and successfully tested with a beam of thermal neutrons, finally. The functionality of these devices was proved.