COMPOUND SEMICONDUCTOR FET

摘要

PROBLEM TO BE SOLVED: To achieve both of high gate threshold voltage and low ON-state voltage of a compound semiconductor FET.SOLUTION: A compound semiconductor FET comprises: a semiconductor substrate 20; a source electrode 42 directly or via an other layer connected to a surface of a semiconductor substrate 20; a gate electrode 44; a drain electrode 46; and a back gate electrode 48. A deep carrier gas layer 25b that is either one of two-dimensional electron gas or two-dimensional hole gas; and a front side carrier gas layer 27b that is the other of two-dimensional electron gas or two-dimensional hole gas, and is arranged at a location nearer to the surface side of the semiconductor substrate 20 than the deep carrier gas layer 25b and opposed to the deep carrier gas layer 25b, are in the semiconductor substrate 20. The back gate electrode 48 is electrically connected to the deep carrier gas layer 25b. At a lower side of the gate electrode 44, a carrier concentration of the deep carrier gas layer 25b is higher than that of the front side carrier gas layer 27b.