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Experimental results of germanium (Ge) and indium (In) preamorphization by ion-implantation show that the diffusion of boron (B) is retarded by the presence of Ge or In and that this retardation is more important than the preamorphization (dechanneling) effect. Result shows that In retards B diffusion more than Ge and the retardation effect due to In becomes greater with increasing retained dose of In. Larger In doses cause larger strain, which results in more B being tied up in immobile clusters near the surface. In order to achieve adequate retained dose of In, the implanted dose of In must be increased to 5/spl times/10/sup 15/ cm/sup -2/. After anneal, the junction depth (at 10/sup 18/ cm/sup -3/) is reduced from 628 /spl Aring/ in the control wafer (no In co-implant) to 480 /spl Aring/.