SEMICONDUCTOR DEVICE AND METHOD FOR MANUFACTURING SEMICONDUCTOR DEVICE

摘要

PROBLEM TO BE SOLVED: To increase threshold voltage in a transistor using a nitride semiconductor layer as a channel.

SOLUTION: A second nitride semiconductor layer 200 has a structure in which a plurality of nitride semiconductor layers having Al composition ratios different from each other are sequentially laminated so that the Al composition ratio varies stepwise. The plurality of semiconductor layers forming the second nitride semiconductor layer 200 are polarized in the same direction respectively. A semiconductor layer nearer to a gate electrode 420 has a stronger (or weaker) polarization intensity than that of the semiconductor layer farther from the gate electrode 420. That is, in the plurality of semiconductor layers, the polarization intensity varies in a single direction with increasing proximity to the gate electrode 420. The polarization direction is a direction in which negative charges become larger than positive charges at boundaries in the plurality of semiconductor layers.

COPYRIGHT: (C)2013,JPO&INPIT