n-channel enhancement m.o.s. transistor built in germanium-doped silicon

Shallow diffusion of germanium into silicon, performed in a vacuum or an open-tube furnace and followed by dry oxidation, results in a C/V curve positively shifted by about 1 V for a 1000 Å thick oxide layer. The shift is due to negative charges in the oxide, which make possible the manufacture of n-channel enhancement metal¿oxide¿semiconductor transistors with an inversion-layer mobility of 770 cm2/Vs and a threshold voltage of +0.8 V.