Method for fabricating a semiconductor substrate

A method for fabricating a semiconductor substrate having an improved dopant profile which comprises:

• providing a silicon on insulator (SOI) substrate comprising a base, an insulating layer and a first semiconductor layer;
• doping the first semiconductor layer with n-type or p-type doping atoms in a flow of hydrogen with temperatures of about 900 to 1200°C. and for a time of 30 seconds to 4 minutes to thereby obtain a modified first semiconductor layer having a dopant concentration of at least 107 atoms/cm3;
• and
• epitaxially growing a second semiconductor layer with a different dopant concentration than the modified first semiconductor layer upon the modified first semiconductor layer, wherein the second semiconductor layer is epitaxially grown at a temperature of 1000 to 1200° C. from a precursor gas that contains n-type or p-type dopant atoms to provide the second semiconductor layer with a dopant concentration of about 1014 to 1016 atoms/cm3;
• wherein the doping of the first semiconductor layer and the providing of the second semiconductor layer are both carried out in n epi-reactor without removing the substrate to thus provide an improved dopant profile in the fabricated semiconductor substrate;
• and
• wherein the first semiconductor layer has a thickness of 50 nm to 800 nm, the second semiconductor layer has a thickness of up to 8 μm, and the insulating layer has a thickness of 50 nm to 1500 nm.