To decrease the leakage current of $p^{+}n$ junction diode with hyperabrupt structure, the $3000{AA}$ polysilicon was deposited on the top of conventional $p^{+}n$ diode and then annealed for 30 minutes at $900^{circ}C$ in the $N_{2}$ ambient. It was estimated for both $p^{+}n$ diodes with and without polysilicon layer, and the impurity materials of n diffused layer to observe the influence of the polysilicon layer on leakage current characteristics. The leakage current was reduced to the order of 3 by using polysilicon layer. A large number of dislocation loops, which were believed to be generated by As-implanted diffused layer, were found to be removed by using polysilicon through TEM analysis.