25 years of improvement of the silicon based TFT: from as-deposited polycrystalline silicon to nanostructured silicon deposited at very low temperature

25 years of effort made in Rennes 1 University to improve the performance of silicon based thin film transistors are reviewed. The review is focused mainly on the technological progress. It starts from the end of 80's at the time where the main work was devoted to understand the physical properties of polycrystalline silicon that was used as active layer of transistors for the first time. It finishes with microcrystalline silicon TFTs fabricated at low temperature compatible with the use of transparent plastic substrates, going through the different crystallized forms of silicon. These different crystallized forms obtained by different techniques allow silicon to be able to stay as the basic material of TFTs whatever the applications and the substrates