Semiconductor device and method for producing the same

A method for producing a semiconductor device comprising steps of:

• preparing a semiconductor substrate on which a layer to be patterned is formed;
• forming an auxiliary mask layer so that the same layer covers said layer to be patterned;
• forming photoresist of a prescribed pattern so that the photoresist is brought into contact with the auxiliary mask layer on the upper part of the auxiliary mask layer;
• patterning the auxiliary mask layer by carrying out the first etching for which the etching speed with respect to the photoresist is lower than that with respect to the auxiliary mask layer using the photoresist as a mask, and forming a auxiliary mask;
• and
• patterning the layer to be patterned by carrying out the second etching for which the etching speed with respect to the photoresist is lower than that with respect to the layer to be patterned, and is higher than the etching speed with respect to the auxiliary mask, using the auxiliary mask, which is formed through the first etching, and the remaining photoresist as masks;
• wherein, where it is assumed that, prior to said second etching, the minimum clearance between said respective photoresists is G, the thickness of the photoresist is U, the thickness of said layer to be patterned is M, and that the permissible maximum aspect ratio for patterning the layer to be patterned is A, and the width of the layer to be patterned by the second etching is made smaller by a prescribed permissible amount than the width of the photoresist before the second etching, the thickness L of said auxiliary mask layer is determined so that said prescribed permissible amount is 1/10 or less of the width of the photoresist before said second etching, and so that it may meet the following inequality:
• L<=A*G−(U+M).