Epitaxial silicon wafer and method for fabricating the same

1. An epitaxial silicon wafer comprising:

a doped bulk wafer;

a first inter-layer formed directly on the doped bulk wafer;

a first epitaxial layer formed directly on the first inter-layer, the first epitaxial layer having a doping concentration higher than that of the doped bulk wafer;

a second inter-layer formed directly on the first epitaxial layer; and

a second epitaxial layer formed directly on the second inter-layer, and the second epitaxial layer having a doping concentration less than that of the first epitaxial layer,

wherein the bulk wafer, the first inter-layer, the first epitaxial layer, the second inter-layer, and the second epitaxial layer have a same conductivity type,

wherein both the first inter-layer and the second inter-layer have a different concentration from the first epitaxial layer and the second epitaxial layer, and

wherein both the first inter-layer and the second inter-layer have a concentration higher than that of the doped bulk wafer.

2. The epitaxial silicon wafer of claim 1 , wherein the doped bulk wafer has a resistivity ranging from approximately 1 Ω·cm to 50 Ω·cm.

3. The epitaxial silicon wafer of claim 1 , wherein the first epitaxial layer has a resistivity ranging from approximately 10-5 Ω·cm to 10-1 Ω·cm.

4. The epitaxial silicon wafer of claim 1 , wherein the second epitaxial layer has a resistivity ranging from approximately 1 Ω·cm to 50 Ω·cm.

5. The epitaxial silicon wafer of claim 1 , wherein the same conductivity is N-type or P-type.

6. The epitaxial silicon wafer of claim 5 , wherein the first epitaxial layer and the second epitaxial layer are formed using one selected from a group consisting of Boron, Arsenic, and Phosphorous.

7. The epitaxial silicon wafer of claim 1 , wherein both the first inter-layer and the second inter-layer are epitaxial layer.