Semiconductor device using sige for substrate and method for fabricating the same

A semiconductor device comprising:

• a first semiconductor layer;
• a p-type second semiconductor layer which is formed on the first semiconductor layer and has an oxidation rate which is lower than an oxidation rate of the first semiconductor layer;
• n-type third semiconductor layers which are formed spaced apart in the second semiconductor layer and have a depth reaching an inner part of the first semiconductor layer from a surface of the second semiconductor layer, a lattice constant of the second semiconductor layer being greater than a lattice constant of the third semiconductor layer;
• and
• a gate electrode which is formed on the second semiconductor layer between the neighboring third semiconductor layers with a gate insulation film interposed between the second semiconductor layer and the gate electrode.

A method for fabricating a semiconductor device, comprising:

• forming, on a first semiconductor layer, a second semiconductor layer of a first conductivity type;
• forming a gate electrode layer and a mask material on the gate electrode with a gate insulation film interposed between the second semiconductor layer and the gate electrode layer;
• etching the mask material and the gate electrode layer, thereby forming a gate electrode;
• after forming the gate electrode, etching the second semiconductor layer while gate electrode covered with the mask material is not etched thereby exposing the first semiconductor layer;
• oxidizing an exposed surface of the first semiconductor layer under a condition in which an oxidation rate of the first semiconductor layer is higher than an oxidation rate of the second semiconductor layer;
• removing oxide films on surfaces of the first and second semiconductor layers by a wet process;
• and
• epitaxially growing a third semiconductor layer of a second conductivity type on the surfaces of the first and second semiconductor layers from which the oxide films are removed.