A semiconductor memory device includes a plurality of memory cell transistors arranged along a common semiconductor layer. Each of the plurality of memory cell transistors comprises a first source/drain region and a second source/drain region formed in the common semiconductor layer; a gate stack formed on a portion of the common semiconductor layer between the first source/drain region and the second source/drain region; and an electrical floating portion in the portion of the common semiconductor layer, a charge state of the electrical floating portion being adapted to adjust a threshold voltage and a channel conductance of the memory cell transistor. The plurality of memory cell transistors connected in series with each other along the common semiconductor layer provide a memory string.