  DEPleted Field Effect Transistor (DEPFET) active pixel detectors combine a
first amplification stage with a fully depleted sensor in one single device,
resulting in a very good signal-to-noise ratio even for thin sensors. DEPFET
pixels are produced in MOS technology with two metal and two poly-silicon
layers and have been developed for the use in Xray imaging and tracking in
particle physics experiments. The sensor concept will be presented and all
aspects of operation will be detailed with the focus on its application at the
upgraded detector Belle II under preparation for the high-luminosity upgrade of
the e+e- KEKB collider in Japan. The stringent requirements on excellent
spatial resolution can be met by cell sizes as small as 25x25 um2 and minimal
material budget. The readout ASICs attached to the sensors will be described as
well as the module design and the thinning technology employed to reduced the
active sensor thickness to as little as 50 um. DEPFET prototype performance at
lab and beam tests will be presented, as well as results of irradiations up to
8 MRad. Extensive simulation studies have been made to asses the vertexing and
tracking performance of DEPFET-based vertex detector of Belle II. The main
performance parameters will be shown, together with an overview of the project
status
