| 摘要 |
PROBLEM TO BE SOLVED: To obtain a method in which a stable threshold voltage can be set for a MOS device having various channel lengths by a method wherein first- conductivity-type ions are implanted into a channel region in two opposite edge parts at an angle of inclination with reference to the surface of a substrate. SOLUTION: First-conductivity-type ions are implanted at an angle of inclinationθwith reference to the surface of a wafer substrate as shown by an arrow 46 while a gate structure 20 is used as a mask. The angle of inclinationθis set preferably between 50 to 70 deg., but is depends on the concentration of a dopant, on a channel length and on a desired threshold voltage. Then, the wafer substrate is turned from a first rotating position up to a second rotating position at about 180 deg., and dopant ions are implanted again into a channel region at the angle of inclination with reference to the surface of the wafer substrate as shown by an arrow 48. Thereby, a stable threshold voltage can be set for a MOS device having various channel lenghts.
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