Provided are methods of manufacturing semiconductor devices by which two different kinds of contact holes with different sizes are formed using one photolithography process. The methods include preparing a semiconductor substrate in which an active region is titled in a diagonal direction. A hard mask is formed on the entire surface of the semiconductor substrate. A mask hole is patterned not to overlap a word line. A first oxide layer is deposited on the hard mask, and the hard mask is removed to form a piston-shaped sacrificial pattern. A first polysilicon (poly-Si) layer is deposited on the sacrificial pattern and patterned to form a cylindrical first sacrificial mask surrounding the piston-shaped sacrificial pattern. A second oxide layer is coated on the first sacrificial mask to such an extent as to form voids. A second poly-Si layer is deposited in the voids and patterned to form a pillar-shaped second sacrificial mask. The second oxide layer is removed to expose the active region. The sectional area of a buried contact (BC) storage contact pad may be increased, while the sectional area of a direct contact (DC) bit line contact pad may be reduced.