Mask-free methods of forming structures in a semiconductor device

Abstract

The present disclosure generally relates to semiconductor device fabrication and integrated circuits. More particularly, the present disclosure relates to replacement metal gate processes and structures for transistor devices having a short channel and a long channel component. The present disclosure also relates to processes and structures for multi-gates with dissimilar threshold voltages. The present disclosure further provides a method of forming structures in a semiconductor device by forming a first and second cavities having sidewalls and bottom surfaces in a dielectric structure, where the first cavity has a narrower opening than the second cavity, forming a first material layer in the first and second cavities, forming a protective layer over the first material layer, where the protective layer fills the first cavity and conformally covers the sidewall and the bottom surfaces of the second cavity, performing a first isotropic etch on the protective layer to selectively remove a portion of the protective layer and form a retained portion of the protective layer, performing a second isotropic etch on the first material layer to selectively remove a portion of the first material layer and form a retained portion of the first material layer, removing the retained portion of the protective layer, and forming a second material layer in the first and second cavities, the second material layer being formed on the retained portion of the first material layer.