We present results on n-channel inversion-type InP metal-oxide-semiconductor field-effect transistors (MOSFETs) with atomic-layer-deposited Al2O3 gate dielectric using the gate-last process. InP MOSFETs with an equivalent oxide thickness (EOT) of 21 angstrom were realized with high performance including a drive current of 50 mA/ mm, an extrinsic transconductance of 44.2 mS/ mm, a subthreshold swing of 90 mV/ dec, and a peak effective electron mobility of 745 cm(2)/ Vs for a 50 mu m gate length. The transmission electron microscopy and X-ray photoemission spectroscopy measurements demonstrate an interface between Al2O3 and InP substrates with high quality and good thermal stability. The effects of fast and slow traps on the transistor performance have also been investigated using constant electrical stress measurements and pulse measurements. (C) 2008 The Electrochemical Society.