A 3D memory device and a manufacture method thereof are disclosed. The 3D memory device includes a substrate; A laminated structure over the substrate, the laminated structure comprising a plurality of spaced-apart gate conductors, the gate conductors being divided into a plurality of gate lines by gate line slots; A plurality of channel columns penetrating the laminated structure; And a conductive channel and an insulating layer located in the gate line slot, the conductive channel being spaced apart from the plurality of gate lines by the insulating layer, wherein the 3D memory device further includes a barrier layer located between an end of the gate line adjacent the conductive channel and the insulating layer. The barrier layer in the 3D memory device can avoid the gap formed by the residual precursor gas causing the gate conductor to be short-circuited with the conductive channel, thereby improving the yield and reliability of the 3D memory device.