In this study, InAs metal-oxide-semiconductor field effect transistors (MOSFETs) ultra-thin body (UTB) were fabricated with self-aligned method. 4 nm thick Al2O3 gate oxide was deposited by Atomic Layer Deposition (ALD) technique. Ni-alloyed ohmic contacts for n-type source and drain (S/D) regions were formed at low annealing temperature (250°C). We developed a special shape based on the vertical diffusion of Ni metal by capillarity. We have systematically studied and analyzed the sheet resistance (Rsheet) of Ni-epilayer alloy and the lateral diffusion of the Nickel alloy. For a MOSFET with a gate length (LG) of 150 nm, we obtained a maximum drain current (ION) of 700 mA/mm, and the extrinsic transconductance (GM, MAX) showed a peak value of 500 mS/mm.