Method for decreasing pn junction leakage current of dynamic random access memory

Abstract

A method for decreasing a PN junction leakage current of a dynamic random access memory (DRAM), including the steps of: preparing an NMOS transistor formed on a P-type silicon substrate and comprising a drain; forming an insulation oxide layer on the P-type silicon substrate; etching the insulation oxide layer until the P-type silicon substrate is exposed so as to form a bit line contact hole on the drain; implanting arsenic ions into the P-type silicon substrate via the bit line contact hole to form an arsenic bit line contact window; and implanting phosphorus ions into the P-type silicon substrate via the bit line contact hole to form a phosphorus bit line contact window below the arsenic bit line contact window. In this way, a concentration gradient of N-type ions can be reduced at the bit line contact window, and further a PN junction leakage current can be reduced, thus lowing the power consumption of the DRAM when the DRAM is used for a low power consumption product.