Silicon sensors are used for the tracker and vertex detectors of all the main current high energy physics experiments because of their unsurpassed performance in terms of granularity, resolution and speed while offering relatively low mass. The anticipated future upgrade of the present Large Hadron Collider (the Super LHC, sLHC) will require detectors with similar performance in terms of speed and low mass, but with increased granularity and a factor often more radiation tolerance. The radiation hardening of silicon sensors, given the sLHC requirements, is being investigated from many angles: different silicon materials, different electrode geometries and varying the thickness of the active substrate. It has been proposed that possible advantages could be achieved with detectors thinner than the accepted standard of 300 Â¿m. The effect of the thickness on the performances of finely segmented silicon sensors after severe hadron irradiation (up to 2 Ã 1016 1 MeV neutron equivalent/cm2) is presented. For the first time, the charge collection properties of microstrip detectors made on 200 Â¿m n-type float zone (FZ) and 150 Â¿m high resistivity epitaxial silicon substrates are compared with thin (140 Â¿m) and standard p-type devices.