Method of fabricating gate oxide layer with different thickness

摘要

A method of fabricating a gate oxide layer of different thickness. A substrate having a gate oxide layer and a gate is provided and a portion of the gate oxide layer is removed. A first thermal oxide layer is formed to cover the surface of the substrate and the gate and a masking layer is formed to cover the first thermal oxide layer. The masking layer is defined and a portion of the thermal oxide layer is removed to expose a portion of the surface of the gate and the substrate. A first implantation is performed and a drain region is formed at the side of the gate. A second thermal oxide layer is then formed to cover the exposing substrate and the exposing gate. The masking layer is removed and the second thermal oxide layer and the first thermal oxide layer are etched back to expose the surface of the gate and the second thermal oxide layer becomes a spacer structure. A second implantation is performed and a source region is then formed at the other side of the gate; the dopant concentration in the drain region adjacent to the gate is lighter.