A method for fabricating a semiconductor device having LDD structure. The method includes: a first step for forming an electrically insulating layer on an active area defined on a surface of a semiconductor substrate; a second step for forming a conductive layer on said insulating layer; a third step for forming a patterned photoresist layer of a downward tapered shape on said conductive layer; a fourth step for forming a gate electrode by patterning said conductive layer using a mask provided by bottom portions of said patterned photoresist layer; a fifth step for forming heavilyly doped regions at both sides of said gate electrode by introducing ions using a mask provided by top portions of said patterned photoresist layer; a sixth step for removing said patterned photoresist layer; and a seventh step for forming lightly doped regions at both sides of said gate electrode by introducing ions using a mask provided by said gate electrode.