Vertex detectors allow high precision reconstruction of particle tracks and therefore make possible the investigation of the decay topology of short-lived particles in collider experiments. In the ALEPH experiment at LEP a minivertex detector will be installed. It consists of silicon microstrip detectors arranged on two concentric "cylindrical" surfaces around the interaction point. With this geometry it will be possible to measure the r - ϕ - z coordinates of particles traversing the detector. The expected position resolution is 10 μm in r - ϕ and 20 μm in r - z. For optimum signal processing monolithic CMOS readout electronics are under development. Each chip consists of 60 charge sensitive preamplifiers, multiplexed into one output channel. Fast power switching will reduce heat dissipation. Details about construction and expected device performance will be described.