METHOD OF IMPLANTING IONS FOR CONTROLLING THRESHOLD VOLTAGE OF MOS TRANSISTOR

摘要

PROBLEM TO BE SOLVED: To provide a method of implanting ions to form transistor elements having a plurality of different threshold voltages in pellets in a silicon wafer, which has simple processes and requires only one mask to be used. SOLUTION: This is method of implanting ions for controlling threshold voltages of a MOS transistor to manufacture a MOS IC(metal oxide semiconductor IC) in which threshold voltage values of elements are divided and set as a plurality of values. Predetermined film thicknesses corresponding to the plurality of different threshold voltage values. Ion implanted regions having the same threshold voltage have the same film thickness. A resist mask is provided to cover the ion implanted regions for controlling transistor threshold voltage with a resist. The whole surface of the resist mask is irradiated with ions. Ions for controlling the threshold voltages are implanted via the resist covering the ion implanted regions for controlling the threshold voltage.