| abstract |
An object of the present invention is to improve the TDDB resistance of a vertical transistor and to suppress a variation in threshold voltage. An upper end of a gate electrode is located below a surface of a semiconductor substrate. The insulating layer 340 is formed on the semiconductor substrate 100 located on and around the gate electrode 120. The insulating layer 340 includes a first insulating film 342 and a low oxygen permeable insulating film 344. The first insulating film 342 is an NSG film, for example, and the low oxygen permeable insulating film 344 is an SiN film, for example. Further, a second insulating film 346 is formed on the low oxygen permeable insulating film 344. The second insulating film 346 is, for example, a BPSG film. After forming the insulating layer 340, the TDDB resistance of the vertical MOS transistor 20 is improved by processing in an oxidizing atmosphere. Further, since the insulating layer 340 includes the low oxygen permeable insulating film 344, variation in the threshold voltage of the vertical MOS transistor 20 can be suppressed. [Selection] Figure 1 |