We have fabricated and tested an atom chip that operates as a matter waveinterferometer. In this paper we describe the fabrication of the chip byion-beam milling of gold evaporated onto a silicon substrate. We present dataon the quality of the wires, on the current density that can be reached in thewires and on the smoothness of the magnetic traps that are formed. We show thatthe chip is able to operate as an interferometer with good phase stability.