| 摘要 |
PURPOSE:To obtain a high density and high-speed operating memory storage by a method wherein the FET gate insulating film to be located on the circumferential circuit is formed thinner than the floating gate FET for memory. CONSTITUTION:The region 30 located on a semiconductor substrate 32 indicates one of FET groups for memory arranged in matrix form, and the region 31 indicates one of FET's which constitutes the circumferential circuit. At this point, the thickness of gate insulating films 41 and 42 is selected as tox3<tox1 and tox2, the tox1 and tox2 are formed in the minimum film thickness with which sufficient holding characteristics can be obtained, and also a reduced film thickness is to be selected for tox3 in order to accomplish a high efficiency. As the access time, power consumption and the like of the memory storage are mostly determined by the circumferential circuit, the dimensions of the gate insulating film of the circumferential circuit are preponderantly reduced, thereby enabling to form a floating gate type memory storage of high degree of integration and high efficiency without impairing the information holding characteristics at all. |
