Method for fabricating finfet structure

Abstract

A method of forming a semiconductor device includes providing a substrate structure having a semiconductor substrate and a fin structure on the semiconductor substrate. The fin structure includes a semiconductor layer and a hard mask layer on top of the semiconductor layer. The method also includes forming a spacer layer on sidewalls of the fin structure. Next, using the hard mask layer and the spacer layer as a mask, the semiconductor substrate is etched to form recesses on both sides of the fin structure that extend partially to underneath the bottom of the fin structure. The method further includes forming a filler material to fill at least the recesses, thereby forming the first filler layer. The first filler layer may be oxidized to form a porous oxide layer and the remaining portion of the substrate under the fin structures may be oxidized to form an oxide layer.

Dependencies are inferred from the claim text.