Patent ID: 8242605

Claim:
A semiconductor device, comprising: (a) a semiconductor substrate comprised of a silicon-based single crystal of a first conductivity type, and having a first main surface and a second main surface; (b) a first semiconductor layer provided closer to the second main surface in the semiconductor substrate, and having a first impurity concentration; (c) a second semiconductor layer provided closer to the first main surface in the semiconductor substrate so as to come in contact with the first semiconductor layer, and having a second impurity concentration; and (d) a silicon-based plug extending from the first main surface through the second semiconductor layer to reach an inside of the first semiconductor layer, wherein the plug includes: (d1) a poly-crystalline region in a center portion thereof; and (d2) a solid-phase epitaxial region including a boundary region between the first and second semiconductor layers, and formed in a vicinity of the boundary in a direction extending between the first and second main surfaces so as to cover a periphery of the poly-crystalline region.