JPH0135507B

PURPOSE:To easily form a plurality of MOS transistors of different threshold values on the same chip by a method wherein at least one gate electrode of a plurality of gate electrodes is irradiated with radiation while a voltage is impressed. CONSTITUTION:The desired electrode is irradiated with the radiation, while the voltge is impressed after forming the gate electrodes, when a plurality of MOS transistors of different threshold values are formed on the same chip. For example, when a transistor 20 is desired to change into a depletion type, and a transistor 24 into an enhancement type, the gate bias 23 is impressed only on the gate electrode 21 of the transistor 20, and the electrode is irradiated with the radiation 25. The change of gate threshold values of channels due to the irradiation of radiation is dependent on the gate bias; therefore MOS transistors having arbitrary threshold values can be obtained by impressing the bias of arbitrary value and then applying radiation.