<p>A terahertz wave emitting device is provided with a nitride semiconductor layer, which is formed on a substrate; another nitride semiconductor layer, which has a large band gap compared to the first nitride semiconductor layer and is formed upon the first nitride semiconductor layer; and a source electrode, gate electrode and drain electrode, which are all formed upon the second nitride semiconductor layer. The source electrode and drain electrode are each formed from a plurality of periodically arranged source electrode fingers and drain electrode fingers.</p>
