Provided is a semiconductor device manufacture method which comprises steps of: forming a cushion layer mainly containing nitride on the side surface of a pseudo gate electrode; converting the cushion layer into a first barrier layer mainly containing oxide; successively forming a accumulation layer, a tunneling layer, and a channel layer on the first barrier layer; removing the pseudo gate electrode and forming a second barrier layer on the exposed first barrier layer; and forming a gate conductive layer on the second barrier layer. According to a semiconductor device and the manufacture method thereof, the nitride cushion layer is converted into the oxide barrier layers so that defect states can be effectively reduced, threshold voltage drift is inhibited, charge transverse diffusion in the accumulation layer is improved, and device reliability is enhanced.