We present the technology and performance of InAlN/AlN/GaN MOS HEMTs with gate insulation and surface passivation using ZrO2 or HfO2. About 10-nm-thick high-k dielectrics were deposited by MOCVD before the ohmic contact processing. Plasma pretreatment allowed the reduction of the temperature of the ohmic contact annealing at 600 degrees C. The insulation and passivation of 2-mu m gate-length MOS HEMTs lead to a gate leakage current reduction by four orders of magnitude and a 2.5 x increase of the pulsed drain-current if compared with a Schottky barrier (SB) HEMT. A dc characterization shows 110 mS mm(-1) transconductance and 0.9 A mm(-1) drain-currents that represent improvements in comparison to the similar SB HEMT and that is explained by a mobility-dependent carrier depletion effect.