| 摘要 |
PROBLEM TO BE SOLVED: To realize a DRAM having the excellent refleshing characteristics without decreasing the threshold voltage of a memory-cell selecting MISFET (metal-insulator semiconductor field-effect transistor). SOLUTION: In a channel region, high-concentration boron for adjusting a threshold voltage is introduced. At the lower part of a pair of n-type semiconductor region constituting a source and a drain, an electric-field alleviating layer constituted of phosphor is formed. Furthermore, at the sloping region of the concentration distribution of the boron for adjusting the threshold voltage, arsenic is introduced. At the region, wherein the arsenic is introduced, the concentration distribution of the above described boron becomes low. The impurity concentration of the semiconductor substrate at the metallurgical bonding position of the electric-field alleviating layer and the semiconductor substrate becomes low to the degree of 1×10<17> cm<3> . |
