(i) Technical Field
The present invention relates to methods for fabricating semiconductor devices, and more particularly, to a method for fabricating a semiconductor device having a silicon nitride film formed on a nitride semiconductor layer.
(ii) Related Art
Semiconductor devices using nitride semiconductors are used in, for example, power devices capable of operating at high frequencies and outputting high power. Particularly, FETs (Field Effect Transistors) such as HEMT (High Electron Mobility Transistor) are known as transistors suitable for amplifying in high-frequency or RF bands, which may include microwaves, quasi-millimeter waves, or millimeter waves.
It is known to form a silicon-rich silicon nitride film formed on a nitride semiconductor layer in order to suppress the collapse phenomenon of the drain current (see Japanese Patent Application Publication No. 2006-278812.
However, a high composition ratio of silicon in the silicon-rich silicon nitride film results in a drift of the drain current.