In this paper, we review some possibilities given by the LPCVD technique to deposit undoped and in-situ doped silicon films on amorphous substrates. To deposit undoped silicon films, two main techniques can be investigated : (i) the silicon films are deposited at temperature higher than 580°C and are polycrystalline. However, their grain size which depends on the deposition parameters, is also dependent on their thickness. (ii) The silicon films are deposited at temperature lower than 580°C and are amorphous. When these films are thermally crystallized at low temperature (Tanneal ≤ 600°C), the grain size may exceed 0.5 µm and does not depend on the thickness of the silicon films. When diborane is added (B2H6 /SiH4= 5.10-3), the micro-crystalline of the silicon films is strongly modified. The decrease down to 10 mTorr of the gas pressure during the deposition process results in the increase of the boron incorporation and in the decrease of the resistivity to 2.10-3 ohm.cm, without any annealing for the films deposited at 625°C. TFT's have been fabricated with these undoped silicon films and their electrical characteristics are presented.