Planar semiconductor diodes supplemented with a layer of an appropriate neutron converter such as 6LiF can be used for thermal neutron counting or imaging. Neutrons interacting in the converter generate alphas and tritons which enter the semiconductor and are detected there. However, simple planar devices suffer from limited detection efficiency which cannot reach more than about 5%. The limit in detection efficiency can be overcome by etching a 3D microstructure of trenches, pores or columns in the detector and filling it with the neutron converter. The overall neutron detection efficiency of such structure with pores was simulated. The results indicate an increase in the detection efficiency by factor 6 in comparison with a standard planar neutron detector. Samples with different silicon column sizes were fabricated to study the electrical properties of 3D structures. The charge collection efficiency in silicon columns from 10 μm to 800 μm wide and 80 μm high was measured. Single pad detectors with pores were fabricated and tested for thermal neutron detection. The samples have square pores of 20 μm wide, ~60 μm deep. The pore pitch is 70 μm. 6LiF was used as the neutron converter for all measurements. Pulse height spectra of the filled samples irradiated by thermal neutrons were measured. The measurement proved functionality of such detector and its usability for thermal neutron detection.