The invention belongs to the technical field of devices with high electron mobility and particularly relates to a device with low parasitic resistance and high electron mobility and a manufacturing method of the device. According to the device and the manufacturing method of the device, the device with high electron mobility is manufactured by adopting a grid-first process, the self-alignment of positions of a grid electrode and a source electrode is realized by using side walls of the grid electrode, and thus, the parameter drift of a product is reduced; and meanwhile, as the grid electrode is protected by a passivation layer, the source electrode and the drain electrode of the device can be formed through an epitaxial process after the grid electrode is formed, the parasitic resistances of the source and drain electrodes are reduced, and the electrical performance of the device with high electron mobility is enhanced.