A semiconductor memory device comprises: a plurality of transistors having a stacked-gate structure, each transistor including a semiconductor substrate, a gate insulator formed on the semiconductor substrate, a lower gate formed on the semiconductor substrate with the gate insulator interposed, an intergate insulator formed on the lower gate, and an upper gate formed and silicided on the lower gate with the intergate insulator interposed. A portion of the transistors has an aperture formed through the intergate insulator to connect the lower gate with the upper gate and further includes a silicide suppression region between the aperture and the gate insulator to suppress diffusion of metal atoms from the silicided upper gate.