1.  Field of the Invention
The invention relates to a semiconductor device and a fabricating method thereof.  More particularly, the invention relates to a non-volatile memory and a fabricating method thereof. 
2.  Description of Related Art
Non-volatile memory is a kind of memory having the advantages that it allows multiple data storing, reading or erasing operations.  The data stored in the non-volatile memory will be retained even if the power applied to the device is cut off.  The non-volatile memory has become a widely adopted memory device in personal computers and electronic equipments. 
A typical non-volatile memory device is a stacked gate structure constituted by a floating gate and a control gate manufactured by doped polysilicon.  The floating gate is disposed between the control gate and the substrate, and is floating instead of being connected to any circuit.  The control gate is connected to a word line.  Besides, a tunneling oxide layer is disposed between the substrate and the floating gate while an inter-gate dielectric layer is disposed between the floating gate and the control gate. 
As the level of integration of the device increases currently, the size of the device is minimized based on the design rule.  Generally, the larger a gate coupling ratio (GCR) between the floating gate and the control gate is, the lower the required working voltage for operation will be.  The methods of increasing the gate coupling ratio include increasing the capacitance of the inter-gate dielectric layer or reducing the capacitance of the tunneling oxide layer.  The principle method for increasing the capacitance of the inter-gate dielectric layer includes increasing the overlapped area between the control gate and the floating gate.  However, as the integration of the device becomes higher, it is difficult to increase the overlapped area between the control gate and the floating gate in the conventional stacked gate structure, and therefore the issue of increasing the GCR and increasing the device integration remains.