Patent ID: 6903383

Claim:
A semiconductor device comprising: at least one active region stacked unit comprising a first active region disposed on a substrate and a second active region disposed on the first active region, at least a portion of the first active region functioning as a channel region, and the second active region including a material having a band gap different from a band gap of the first active region such that a band discontinuity occurs between the first and second active regions; a gate electrode disposed above the second active region located at the uppermost of said at least one active region stacked unit; and a pair of diffusion regions of high concentration impurities provided above the second active region located at the uppermost of said at least one active region stacked unit, and opposing each other with the gate electrode being interposed therebetween, wherein the second active region includes multiple δ-doped layers made by alternately stacking a plurality of first semiconductor layers and a plurality of second semiconductor layers, each of the plurality of first semiconductor layers allows passage of carriers therethrough, each of the plurality of second semiconductor layers contains an impurity for carriers having concentration higher than that of each of the plurality of first semiconductor layers, and is smaller in film thickness than each of said plurality of first semiconductor layers, the plurality of first semiconductor layers and the plurality of second semiconductor layers have a same composition, and no channel region is provided above the second active region located at the uppermost of said at least one active region stacked unit.