Semiconductor FinFET device and method

A method comprising:

• forming a first mask layer over a semiconductor substrate;
• forming a second mask layer over the first mask layer;
• patterning the second mask layer;
• etching the first mask layer through the patterned second mask layer to form a patterned first mask layer, the etching of the first mask layer comprising:
• performing a first etching process to form upper portions of the patterned first mask layer, the upper portions having a first width;
• after performing the first etching process, performing a second etching process to form middle portions of the patterned first mask layer, the middle portions having a second width greater than the first width, wherein the second etching process is different than the first etching process;
• and
• after performing the second etching process, performing a third etching process to form lower portions of the patterned first mask layer, the lower portions having a third width less than the first width, wherein the third etching process is different than the second etching process;
• and
• etching the semiconductor substrate through the patterned first mask layer to form a plurality of adjacent fins protruding from the semiconductor substrate.

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

• depositing a mask layer over a substrate;
• patterning the mask layer to form a plurality of mask regions, wherein each mask region has convex sidewalls;
• etching the substrate using the plurality of mask regions as an etching mask to form a plurality of fins, wherein after etching the substrate, the convex sidewalls of the mask regions extend laterally beyond upper sidewalls of the fins;
• forming an isolation region surrounding the fins;
• forming a gate structure over top surfaces of the fins and on the upper sidewalls of the fins;
• and
• forming source and drain regions in the fin adjacent the gate structure.