| 摘要 |
PROBLEM TO BE SOLVED: To freely set the threshold voltage Vth of a field-effect transistor, without doping impurities. SOLUTION: A field-effect transistor has a first gate electrode 7, which is positioned at the central part of the transistor, and second gate electrodes 8, which are positioned on both sides of the electrode 7, and at least one part of each of the second gate electrodes 8 is positioned on a channel formation region. As the materials for the electrodes 7 and 8, materials having different work functions are used. A first gate electrode length is set in the range that an electric field from the electrode 7 and electric fields from the electrodes 8 cause interference with each other. The electrode length is preferably set in a length of 40 nm or shorter.
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