Semiconductor device and method for fabricating the same

A method of fabricating a semiconductor device, comprising the steps of:

• forming a first gate insulating layer on a semiconductor substrate, and forming a second gate insulating layer on one side of the first gate insulating layer, the second gate insulating layer being thicker than the first gate insulating layer, wherein the second gate insulating layer is formed from an insulating layer containing semiconductor conductivity type impurity ions;
• forming a gate electrode on the first and second gate insulating layers, a first side of the gate electrode corresponding to the first gate insulating layer and a second side of the gate electrode corresponding to the second gate insulating layer;
• and
• forming first impurity regions in the semiconductor substrate on both sides of the gate electrode, and forming a second impurity region in the semiconductor substrate under the second gate insulating layer.