Patent ID: 8247273

Claim:
A semiconductor device with at least one thin-film transistor comprising: a substrate; a crystalline semiconductor layer, which has been formed on the substrate to include a region to be a channel region, a source region and a drain region; a gate electrode for controlling the conductivity of the region to be a channel region; a gate insulating film arranged between the semiconductor layer and the gate electrode; and a source electrode and a drain electrode, which are connected to the source and drain regions, respectively, wherein at least one of the source and drain regions contains an element to be a donor or an acceptor and a rare-gas element, and wherein the region to be a channel region does not contain the rare-gas element, and wherein the atomic weight of the rare-gas element is greater than that of the element to be a donor or an acceptor, and wherein the concentration of the rare-gas element in the at least one region as measured in the thickness direction thereof decreases continuously from the upper surface of the at least one region toward its lower surface.