  We present the systematic study of the resonant tunneling spectroscopy on a
series of ferromagnetic-semiconductor Ga1-xMnxAs with the Mn content x from
~0.01 to 3.2%. The Fermi level of Ga1-xMnxAs exists in the band gap in the
whole x region. The Fermi level is closest to the valence band (VB) at x=1.0%
corresponding to the onset of ferromagnetism near the metal-insulator
transition (MIT), but it moves away from the VB as x increasing or decreasing
from 1.0%. This anomalous behavior of the Fermi level indicates that the
ferromagnetism and MIT emerge in the Mn-derived impurity band.
