  Monolithic Active Pixel Sensors (MAPS) have been developed since the late
1990s based on silicon substrates with a thin epitaxial layer (thickness of
10-15 $\mu$m) in which charge is collected on an electrode, albeit by
disordered and slow diffusion rather than by drift in a directed electric
field. As a consequence, the signal is small ($\approx$ 1000 e$^-$) and the
radiation tolerance is much below the LHC requirements by factors of 100 to
1000. In this paper we present the development of a fully Depleted Monolithic
Active Pixel Sensors (DMAPS) based on a high resistivity substrate allowing the
creation of a fully depleted detection volume. This concept overcomes the
inherent limitations of charge collection by diffusion in the standard MAPS
designs. We present results from a test chip EPCB01 designed in a commercial
150 nm CMOS technology. The technology provides a thin (50 $\mu$m) high
resistivity n-type silicon substrate as well as an additional deep p-well which
allows to integrate full CMOS circuitry inside the pixel. Different matrix
types with several variants of collection electrodes have been implemented.
Measurements of the analog performance of this first implementation of DMAPS
pixels will be presented.
