A new insulating film, InPxOy, has been deposited in an indirect plasma‐enhanced low‐pressure chemical vapor deposition system for use as a gate dielectric layer on InP. In this system the oxygen is excited in an rf plasma chamber which is separated from the deposition chamber to avoid radiation damage to the InP surfaces. Triethylindium (TEI) and PH3 were used as sources for indium and phosphorus, respectively. A two‐zone furnace was employed in which PH3 was decomposed in the high‐temperature (800 °C) zone, whereas deposition was carried out in the low‐temperature (300 °C) zone. The electrical properties of the deposited films are dependent, to a large extent, upon the ratio of TEI vapor to PH3 during deposition. The resistivities range from 1013 to 1015 Ω cm. Fast interface state densities as determined from capacitance‐voltage (C‐V) measurements of layers deposited on n‐type InP substrates exhibit minima as low as 1010 cm−2 eV−1. The hysteresis in the high‐frequency C‐V curves was as low as 0.2 V, indicating that the densities of the slow states were reduced to a very low level due, probably, to the structural compatibility between the deposited layer and the InP substrates.