In a semiconductor device and a method of manufacturing the semiconductor device, a plug and a channel structure are formed. The plug fills an opening and the channel structure extends upwardly from the plug. The channel structure has a substantially vertical sidewall. The opening is formed through an insulation structure located on a substrate. The plug and the channel structure comprise a material in a single crystalline state that is changed from an amorphous state by an irradiation of a laser beam. The channel structure is doped with impurities such as boron, phosphorus or arsenic.