| 摘要 |
PURPOSE:To improve write characteristic by performing impurity additions to a channel region and an inactive region is individual processes and making the impurity density of the channel region thinner than the impurity density of the inactive region. CONSTITUTION:SiO2 film 14 and Si3N4 film 15 are caused to adhere onto P-type Si substrate 13 by lamination, and further, SiO2 film 16 is grown on these films, and film 16 on inactive region 18 is removed by photo resistor technique. Next, left film 16 is used as a mask to etch exposed film 15 and film 14, and substrate 13 of inactive region 18 is exposed. After that, P-type mpurity is diffused to region 18 and is made P<+>-type, and thick SiO2 film 19 is grown on this impurity by heat treatment. Next, films 16, 15 and 14 are all removed, and thin gate SiO2 film 20 is caused to adhere there, and P-type impurity ions are injected into substrate 13 through film 20 to form P-type channel region 30 having a density thinner than inactive region 18. After that, N-tupe source and drain regions 34 and 35 are formed at both edges of region 30 by diffusion. |
