US Patent 7138692 Semiconductor device

A gate insulating film and a gate electrode are formed on a silicon substrate. The gate insulating film contains at least hafnium, oxygen, fluorine, and nitrogen. The fluorine concentration is high in the vicinity of an interface with the silicon substrate and progressively decreases with decreasing distance from the gate electrode. The nitrogen concentration is high in the vicinity of an interface with the gate electrode and progressively decreases with decreasing distance from the silicon substrate. The fluorine concentration in the vicinity of the interface with the silicon substrate is preferably 1×1019 cm−3 or more. The nitrogen concentration in the vicinity of the interface with the gate electrode is preferably 1×1020 cm−3 or more.