Different sized features in the array and in the periphery of an 
integrated circuit are patterned on a substrate in a 
single step. In particular, a 
mixed pattern, combining two separately formed patterns, is formed on a single 
mask layer and then transferred to the underlying substrate. The first of the separately formed patterns is formed by 
pitch multiplication and the second of the separately formed patterns is formed by conventional 
photolithography. The first of the separately formed patterns includes lines that are below the resolution of the photolithographic process used to form the second of the separately formed patterns. These lines are made by forming a pattern on 
photoresist and then 
etching that pattern into an 
amorphous carbon layer. Sidewall pacers having widths less than the widths of the un-etched parts of the 
amorphous carbon are formed on the sidewalls of the 
amorphous carbon. The amorphous carbon is then removed, leaving behind the sidewall spacers as a 
mask pattern. Thus, the spacers form a 
mask having feature sizes less than the resolution of the 
photolithography process used to form the pattern on the 
photoresist. A protective material is deposited around the spacers. The spacers are further protected using a 
hard mask and then 
photoresist is formed and patterned over the 
hard mask. The photoresist pattern is transferred through the 
hard mask to the protective material. The pattern made out by the spacers and the temporary material is then transferred to an underlying amorphous carbon hard 
mask layer. The pattern, having features of difference sizes, is then transferred to the underlying substrate.