Semiconductor devices having an improved gate

摘要

A MOSFET comprises a silicon substrate 1 having a source/drain region 7b formed in a surface region thereof, an insulating film 3 formed of silicon oxide, and a gate electrode 4a. The side surface region of the electrode 4a is covered with an insulating film 6 formed of silicon nitride. The insulating film 6 has an extended portion interposed between the electrode 4a and the insulating film 3 in a manner to surround the lower corner portion 4b of the electrode. Since the insulating film 6 has a dielectric constant larger than that of the insulating film 3, it is possible to suppress the electric field intensity at the lower corner portion 4b of the electrode.