Step 2: etching the first sublayer of non-metal conductive material 310a and the substrate 100 to form the bitline contact hole 200, the retained first sublayer of non-metal conductive material 310a serving as a first sublayer 310 of the non-metal conductive layer. Referring to FIGS. 4 and 5, in one of the embodiments, the step of etching the first sublayer of non-metal conductive material 310a and the substrate 100 to form the bitline contact hole 200 includes: forming a first hard mask layer on the first sublayer of non-metal conductive material 310a, the first hard mask layer having a first graphical target pattern, the first graphical target pattern defining the bitline contact hole 200; etching, based on the first hard mask layer, the first sublayer of non-metal conductive material 310a and the substrate 100 to form the bitline contact hole 200.