Resist pattern forming method and semiconductor device manufacturing method

A method of manufacturing a semiconductor device, the method comprising:

• applying a photoresist to first and second regions of a processing target to form a resist layer, the processing target including a stacked body of first and second layers alternately stacked one on the other, the first region including an upper surface of the stacked body and the second region including a recess extending in a first direction from the upper surface into the stacked body, the resist layer including a portion inside the recess;
• exposing the resist layer with light through a multi-gradation mask, the multi-gradation mask including a partial translucent feature corresponding in position to an outer perimeter of the recess, a light shielding feature corresponding in position to the recess, and a translucent feature surrounding the partial translucent feature;
• and
• forming a resist pattern by developing the exposed resist layer with a developer, the resist pattern including an overhang portion extending in a second direction parallel to the upper surface to a position above a portion of the recess in the first direction, the portion of the resist layer inside the recess being removed in the developing of the exposed resist layer with developer;
• and
• etching the processing target by using the resist pattern as an etch mask.