| 摘要 |
PROBLEM TO BE SOLVED: To lift the trade off relation between threshold and diffusive leakage by a method wherein at least one out of the control electrodes facing respective doped channel layers of the first to third kinds of transistors is formed of a second conductivity type impurity layer having the concentration distribution in the internal depth direction. SOLUTION: Within the gate electrodes 4A-4C of N channel type MOS transistors T41-T43, the impurity concentrations are respectively differentiated from one another by changing the impurity dosages so as to lower the impurity concentration in the ascending order of the threshold. That is, the impurity concentration of the transistor T41 in the sense amplifier is made to have the highest value, and the concentration is lowered in the order from the transistor T42 in the peripheral circuit part to the transistor T43 in the memory cell array part. In such a constitution, the trade off relation between the threshold and the diffusive leakage layer is lifted by setting up the impurity concentrations in the doped channel layers so as to minimize the diffusion layer leakage thereby enabling the restriction on the circuit design to be broken off. |
