METHODS OF MANUFACTURING A SEMICONDUCTOR DEVICE

In a method of manufacturing a semiconductor device, a first insulation layer and a first sacrificial layer are alternately and repeatedly formed on a substrate to form a mold layer. A sacrificial layer structure is formed on the mold layer to include an etch stop layer and a second sacrificial layer sequentially stacked. After forming a hard mask on the sacrificial layer structure, the sacrificial layer structure and the mold layer are etched by a dry etching process using the hard mask as an etching mask to form a channel hole exposing an upper surface of the substrate and form a recess on a sidewall of the second sacrificial layer adjacent to the channel hole. A memory channel structure is formed in the channel hole. The first sacrificial layer is replaced with a gate electrode.