Patent ID: 9595606
Date: 2017-03-14
CPC Classifications: H01L

Claim:
1. A field-effect transistor comprising: a first semiconductor layer made of a first nitride semiconductor and formed on a substrate; a second semiconductor layer made of a second nitride semiconductor and formed on the first semiconductor layer; and a third semiconductor layer made of a third nitride semiconductor with a band gap wider than that of the second nitride semiconductor and formed on the second semiconductor layer, wherein: the first semiconductor layer includes carbon (C) and Si as impurity elements, an impurity concentration of carbon (C) in the first semiconductor layer is equal to or higher than 5×10 an impurity concentration of Si in the first semiconductor layer is lower than the impurity concentration of carbon (C) in the first semiconductor layer, an impurity concentration of carbon (C) in the second semiconductor layer is equal to or lower than 1×10 a thickness of the second semiconductor layer is equal to or greater than 0.75 μm.