Abstract: A semiconductor device includes: a semiconductor substrate; a first insulating film (third insulating film 24) formed on the semiconductor substrate, having a first trench (second interconnect trench 28), and having a composition ratio varying along the depth from an upper face of the first insulating film; and a first metal interconnect (second metal interconnect 25) filling the first trench (second interconnect trench 28). The mechanical strength in an upper portion of the first insulating film (third insulating film 24) is higher than that in the other portion of the insulating film (third insulating film 24).

Abstract: A semiconductor substrate in a state that an inter-layer insulation film is formed is loaded in a chamber, air in the chamber is purged by introducing a large amount of a nitrogen gas in the chamber, and an atmospheric gas in the chamber is substituted with a nitrogen gas. After that, UV cure is performed by introducing a small amount of an oxygen gas adjusted to an atmospheric pressure or a little more positive pressure in the chamber by nitrogen purge. For the introduction of an oxygen gas, an oxygen gas is introduced while controlling the flow rate by using a flow meter, and adjustment is performed using the flow meter so that the oxygen concentration in the chamber becomes a constant value in the range of 5 ppm to 400 ppm.