| 摘要 |
PURPOSE:To reduce the leakage current of a mask ROM by adopting a structure that differentiates the depth of a semiconductor region formed in the region except at channel forming region from that of the source or drain region of an MISFET. CONSTITUTION:An MISFETQm which forms a memory cell of a mask ROM is formed of a semiconductor substrate 1, a gate insulating film 4, a gate electrode 5, a pair of n<+> type source region and drain region 6. Since an impurity is introduced into the substrate 1, a semiconductor region 7A can be formed deeply as compared with the depths of a semiconductor region 7 and the source or drain region 6. Since the depth of the region 7A is formed deeper than the junction of the source and drain regions 6 in this manner, a crystal defect is positively formed in a boundary portion between the region 7A and the substrate 1 to reduce crystal defects produced in the junction between the source and drain regions 6. Thus, a leakage current can be reduced. |
