Method for forming polycide gate electrode of metal oxide semiconductor field effect transistor

A method for fabricating a MOSFET device having a polycide gate to which a titanium silicide is applied, comprising the steps of:

• forming a gate insulating layer on a semiconductor substrate;
• forming a polysilicon layer on the gate insulating layer;
• forming a titanium layer on the polysilicon layer;
• forming a nitrogen blocking layer on the titanium layer to prevent a formation of a titanium nitride layer where the nitrogen blocking layer prevents nitrogen in a nitrogen atmosphere form reacting on the titanium layer during a rapid thermal process, wherein the blocking layer is formed with a layer selected from a group consisting of a polysilicon layer, an amorphous layer and an oxide layer;
• forming a titanium silicide layer under the nitrogen blocking layer by performing a rapid thermal process in the nitrogen atmosphere;
• forming a mask insulating layer on the nitrogen blocking layer;
• pattering the nitrogen blocking layer, the titanium silicide layer, the polysilicon layer and the gate insulating layer by using the mask insulating layer and etching process, whereby the surface of the semiconductor substrate and sidewalls of the nitrogen blocking layer, the titanium silicide layer, the polysilicon layer and the gate insulating layer are exposed;
• and
• performing an oxidation process for forming a screen oxide layer on the exposed surface of the semiconductor substrate and the exposed sidewalls of the nitrogen blocking layer, titanium silicide layer, the polysilicon layer and the gate insulating layer.