In a method of forming a dense contact-hole pattern in a semiconductor device, the method uses a self-align double patterning technique including forming a square or triangular lattice dot pattern on double layers of mask materials, forming first holes in the upper mask material and second holes wider than the first holes in the lower mask material by double patterning, additionally forming an insulating layer to a thickness such that the first holes are closed such that voids are left in the second holes, and transferring the shape of the voids to a base layer. The hole pattern formed thereby has a high precision, with a density thereof being double or triple that of a pattern formed by a lithography technique.