Each of MIS transistors of a semiconductor memory device has a semiconductor layer (12); a source region (15) formed in the semiconductor layer; a drain region (14) formed apart from the source region in the semiconductor layer, the semiconductor layer between the source region and the drain region serving as a channel body in a floating state; a first gate (13) which forms a channel in the channel body; a second gate (20) formed so as to control a potential of the channel body by a capacitive coupling; and a high concentration region (21) formed in the channel body on the second gate side, impurity concentration of the high concentration region being higher than that of the channel body.