A method of fabricating a semiconductor device is provided which requires less distance allowance between gate electrodes and a contact hole, and which can therefore readily promote micro-fine patterning. A gate insulating film, conductive films to be used as material for gate electrodes, and a mask insulating film to be used as an etching mask are sequentially formed in stack on a surface of a semiconductor substrate. The mask insulating film and the conductive films are processed into a gate electrode pattern. An interlayer insulation film is deposited to fill a space between adjacent stacks of the mask insulating film and gate electrodes. The interlayer insulation film is selectively etched relative to the mask insulating film, thereby exposing sides of the mask insulating film. Side wall films are formed on the exposed portions of sides of the mask insulating film. The interlayer insulation film is selectively etched relative to the mask insulating film and side wall films, a contact hole being thereby formed.