| abstract |
A first GaN layer, a first AlGaN layer, a second GaN layer and a third GaN layer are formed in layers on a substrate. A second AlGaN layer is formed on the sidewall of an opening formed in the multilayer structure. A gate electrode is formed to fill an electrode trench in an insulating film. A portion of the insulating film between the gate electrode and the second AlGaN layer functions as a gate insulating film. A source electrode is formed above the gate electrode and a drain electrode is formed below the gate electrode. This configuration enables implementation of a miniatuarizable, reliable vertical HEMT that has a sufficiently high withstand voltage and high output power and is capable of a normally-off operation without problems that could otherwise result from the use of a p-type compound semiconductor. |