[en] The use of the 3D detector geometry, where the electrodes go through the bulk of the semiconductor instead of sitting at the surface, allows the life of semiconductor devices to be extended in harsh radiation environments. This geometry also enables the use of less than optimal material, i.e. with poorer charge collection efficiency. Three different production methods have been investigated: dry etching, laser machining and photoelectrochemical etching. The electrical characteristics of the resulting test devices made in low resistivity silicon and gallium arsenide have been studied. Some of these 3D detectors were characterised after irradiation by 300 MeV/c pions, up to a fluence of 10¹⁴ π/cm² at the Paul Scherrer Institute, Villigen