Patent ID: 8570455

Claim:
A semiconductor device comprising: a supporting substrate; a semiconductor film on the supporting substrate; a gate insulating film on the semiconductor film; a gate electrode on the gate insulating film; and a source region and a drain region formed by introducing boron to the semiconductor film, wherein a thickness of the semiconductor film is within a range of 20 nm to 40 nm, the semiconductor device further comprises low-concentration regions provided between the source region and a channel forming region, and between the drain region and the channel forming region, respectively, the low-concentration regions each having a boron concentration smaller than that of the source region and that of the drain region, and the boron concentration in a lower surface side region on a side of the supporting substrate being smaller than that of an upper surface side region on the opposite side, and the semiconductor film is configured such that the integral of product A×B over the total wavelength range (nm) is not more than 5 , where A is a relative intensity spectrum obtained by normalizing a luminescence spectrum of incident light upon the semiconductor film, by the maximum value of the luminescence spectrum, B is a relative intensity spectrum obtained by normalizing an absorption spectrum of the semiconductor film by the maximum value of the absorption spectrum, and the incident light has a wavelength range of 400 nm to 800 nm.