Patent ID: 8183647

Claim:
A semiconductor device comprising: a silicon based semiconductor channel of a field effect transistor provided with a step including a non-horizontal surface, a horizontal surface and a connection region for connecting the non-horizontal surface and the horizontal surface; a gate insulating film formed in at least a part of the step; a gate electrode formed on the gate insulating film, wherein the entirety or a part of the gate insulating film is formed of a silicon oxynitride film that contains a rare gas element at a area density of 10 10 cm −2 or more in at least a part of the silicon oxynitride film, and wherein the horizontal surface corresponds to a (100) plane in the silicon based semiconductor substrate, the connection regions correspond to a (111) plane in the silicon based semiconductor substrate and the non-horizontal surface corresponds to a (110) plane in the silicon based semiconductor substrate, and wherein a (100) plane and a (111) plane have an interface level density in the order of 10 10 eV −1 cm −2 .