Method for filling a space in a semiconductor

A method for partially filling a space between two superimposed structures in a semiconductor device under construction is provided. The method includes the steps of: (a) providing the two superimposed structures having said space therebetween; (b) entirely filling said space with a thermoplastic material; (c) removing a first portion of the thermoplastic material present in the space, the first portion comprising at least part of a top surface of the thermoplastic material, thereby leaving in said space a remaining thermoplastic material having a height; and (d) heating up the remaining photosensitive thermoplastic material so as to reduce its height. A replacement metal gate process for forming a different gate stack on two superimposed transistor channels in a semiconductor device under construction as well as a semiconductor device under construction is also provided.