Patent ID: 7049681

Claim:
A semiconductor device comprising: a substrate including an n-type first single-crystal semiconductor layer functioning as a collector layer; a p-type second single-crystal semiconductor layer formed on the first single-crystal semiconductor layer, the second single-crystal semiconductor layer containing a p-type impurity and functioning as a base layer; a third single-crystal semiconductor layer made of Si and formed on the second single-crystal semiconductor layer, an upper portion of the third single-crystal semiconductor layer functioning as an emitter containing phosphorus in a concentration equal to or less than the solid-solubility limit; and an emitter lead electrode formed on the third single-crystal semiconductor layer, wherein the emitter lead electrode includes: an n − polysilicon layer containing phosphorus in a concentration higher than that in the upper portion of the third single-crystal semiconductor layer functioning as the emitter; and an n + polysilicon layer containing phosphorus in a concentration higher than that in the n − polysilicon layer, and wherein the n − polysilicon layer and the upper portion of the third single-crystal semiconductor layer functioning as an emitter are in contact with each other.