The Cl doped amorphous silicon film was deposited from SiH4, SiH2Cl2 and H2 gas mixture by PECVD process and their properties with various SiH2CI2 flow rate is discussed. Controlling the amount of Cl doped was crucial for acquiring high stability TFT without lowering on current. Amorphous silicon and Cl doped amorphous silicon double layer TFT structure, with satisfactory on current and throughput, proved to be more stable than conventional amorphous silicon TFT in photo state and in elevated temperatures.