Thin Film Transistors were deposited with different insulator/semiconductor interfaces using silicon nitride (a-SiNX) as bulk dielectric, to determine what interface modification technique (plasma treatment or interface layer deposition) is the most suitable for improving their electrical characteristics and stability. One of the samples has only a-SiNX and was used as control sample. Three samples were treated with H-2, N-2 and O-2 plasmas prior to the amorphous silicon deposition. Another two samples were prepared using other materials such as silicon carbide (a-SiCX) or silicon oxide (a-SiOX) as interface layers, building a-SiNX/a-SiCX or a-SiNX/a-SiOX stacks. Results show that oxidizing plasma treatment increases drastically the threshold voltage (V-Th) from 6.23V to about 11.2V. N-2 and H-2 plasma treatments are effective in lowering the leakage OFF current, but only H-2 plasma leads to a decrease of V-Th (from 6.23V to 4.98V). N-2 plasma treated TFTs present an increase of V-Th (from 6.23V to 6.91V) and are less stable to voltage bias stress than H-2 plasma treated TFTs. In all samples submitted to interface plasma, an improvement of mu(FE) was observed, except in the case of O-2 plasma. Devices made with an intermediate a-SiOX layer present lower V-th and mu(FE). The best improvement was achieved in samples with a-SiNX/a-SiCX stack layers, achieving mu(FE) = 0.56 cm(2)/V.s, which represents an increase of similar to 50% over conventional TFT.