Patent ID: 7678645

Claim:
Method for forming a heterostructure semiconductor device in a growth chamber with gas inlet, said method comprising the steps of: providing a silicon substrate in the growth chamber on a substrate carrier, maintaining a constant substrate temperature (T S ) of the substrate in a range between 350° C. and 500° C. during the deposition of a Si 1-x Ge x semiconductor layer having a thickness between 100 nm and 800 nm, establishing a high-density, low-energy plasma in the growth chamber such that the substrate is being exposed to the plasma, directing Silane gas (SiH 4 ) and Germane gas (GeH 4 ) through the gas inlet into the growth chamber, the flow rates of the Silane gas and the Germane gas being adjusted in order to form said semiconductor layer by means of low-energy plasma enhanced chemical vapor deposition with a growth rate in a range between 1 and 10 nm/s, said Si 1-x Ge x semiconductor layer having a constant Germanium concentration x in a range between 0<x<50% a degree of relaxation of at least 75%, performing an annealing step with a temperature in a range between 600° C. and 870° C. providing a surface roughness (rms) of said Si 1-x Ge x semiconductor layer having rms values below 1.8 nm, forming an active region above said Si 1-x Ge x layer.