The present invention relates to a method of forming a trench-type capacitor. More particularly, the plate areas of the trench-type capacitor are increased according to the present invention. The method of this invention comprises the steps of: providing a semiconductor substrate; forming a first trench in the semiconductor substrate, wherein the first trench has a first predetermined depth in the semiconductor substrate; forming first spacers on the side-walls of the first trench, wherein the first spacers include second spacers formed at the bottom of the first trench and third spacers exposed to the air; forming a second trench by aligning the semiconductor substrate with masks of the first spacers and etching the semiconductor substrate to a second predetermined depth; forming a first conducting layer by doping ions into the semiconductor substrate in the second trench; forming an oxide layer on the surface of the first conducting layer by oxidation, wherein the thickness of the oxide layer is less than that of the first conducting layer; forming a second conducting layer by removing the oxide layer, removing the first spacers; forming a dielectric layer upon the second conducting layer; and forming a third conducting layer upon the dielectric layer.