A semiconductor device includes a stacked structure having first conductive layers stacked stepwise and first insulating layers interposed between the first conductive layers, wherein undercuts are formed under the first conductive layers and each of the first conductive layers includes a first region covered by the first conductive layer and a second region extending from the first region, contact pads coupled to the second regions of the respective first conductive layers, and a liner layer formed on the contact pads and filling the undercuts.