A flash memory and a flash memory fabrication method for increasing the coupling ratio by HSG including forming a STI region on a silicon substrate to define an active region, forming a tunneling oxide layer on the active region, and depositing an amorphous silicon layer on the silicon substrate. The method also includes patterning the amorphous silicon layer along a bit line direction, forming an embossed silicon layer including HSGs on the patterned amorphous silicon layer, and sequentially depositing an ONO layer and a polysilicon layer for a control gate on the resulting structure. The method further includes forming a photoresist pattern on the polysilicon layer, and forming a control gate by etching the polysilicon layer using the photoresist pattern as a mask, and simultaneously forming a floating gate along the bit line.