Bit line gate and manufacturing method thereof

A method for forming a bit line gate structure, comprising:

• providing a substrate;
• forming an amorphous silicon layer on the substrate;
• performing an ion doping step to form a first doped region in the amorphous silicon layer, wherein an oxide layer is formed on the surface of the amorphous silicon layer after the ion doping step is performed;
• performing an etching step to completely remove the oxide layer;
• forming a titanium silicon nitride (TiSiN) layer on the amorphous silicon layer;
• and
• performing a rapid thermal process (RTP) to diffuse the first doped region into the TiSiN layer, and to form a second doped region within the TiSiN layer.