| 摘要 |
PURPOSE:To form an N-type diffused layer with a double-layer composition which has a high concentration is a shallow region and has a low concentration in a deep region in a silicon substrate effectively by a method wherein phosphorus ions are implanted into a silicide film only and, after a silicon oxide film is formed, annealing is applied. CONSTITUTION:After a metal film is formed on a P-type silicon substrate 1, a silicide film 2 is formed by annealing. Then phosphorus ions are implanted into the silicide film 2 only with a high concentration and a silicon oxide film 4 is formed on the silicide film 2. Finally, annealing is carried out to diffuse the phosphorus implanted in the silicide film 2 into the silicon substrate 1 and a phosphorus diffused layer 5 is formed. The N-type carrier concentration distribution 6 of the phosphorus diffused layer 5 in the silicon substrate 1 is obtained as a two-step distribution consisting of a high concentration part 7 in a shallow region and a low concentration part 8 in a deep region. The junction depth of this double-layer N-type diffused layer is mainly determined by the relatively deep low concentration diffused layer and a required depth can be obtained by optionally selecting the temperature and period of the annealing.
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