  We describe a planar silicon metal-oxide-semiconductor (MOS) based single
hole transistor, which is compatible with conventional Si CMOS fabrication. A
multi-layer gate design gives independent control of the carrier density in the
dot and reservoirs. Clear Coulomb blockade oscillations are observed, and
source-drain biasing measurements show that it is possible to deplete the dot
down to the few hole regime, with excited states clearly visible. The
architecture is sufficiently versatile that a second hole dot could be induced
adjacent to the first one.
