A method for forming a pattern film with a narrower width than the resolution of an exposure machine and a resist used independently of etching is provided. The method comprises the steps of: forming a first frame layer having end surfaces facing each other across a space having a width W1; forming a second frame layer having end surfaces facing each other across a space having a width W2 that is larger than the width W1, the space having the width W2 being located right above the space having the width W1; forming a trench-forming film provided with a trench having a minimum width W3 that is smaller than the width W1 so as to fill at least a part of the spaces having the width W1 and the width W2 respectively; and forming a pattern film so as to fill at least a part of the trench.