Semiconductor storage device and method for manufacturing the same

A semiconductor storage device comprising:

• a semiconductor substrate;
• an embedded insulator embedded in a trench formed in the semiconductor substrate and having an upper portion protruding above a top surface of the semiconductor substrate;
• a first insulating film formed on the top surface of the semiconductor substrate;
• a floating gate formed on the first insulating film at a side of the embedded insulator, having an upper side portion arching out above the embedded insulator;
• a second insulating film contacting an upper surface and a side surface of the floating gate;
• and
• a control gate disposed adjacent to the floating gate, the second insulating film being disposed between the control gate and the floating gate;
• the floating gate including a first conductive layer disposed on the first insulating film and a second conductive layer disposed on the first conductive layer such that a joint between the first conductive layer and the second conductive layer is more remote than a top surface of the embedded insulator from the top surface of the semiconductor substrate, the first conductive layer being laminated on the first insulating film;
• and
• the second conductive layer being wider than the first conductive layer, the second conductive layer having an overhanging side portion extending along the top surface of the semiconductor substrate beyond a side surface of the first conductive layer to overhang above the embedded insulator, the second insulating film contacting a lower surface of the overhanging side portion to intervene between the overhanging side portion and the embedded insulator.