A three-dimensional MOS transistor formation technique with crystallographic orientation-dependent TMAH etchant

Along with continuous scaling of MOS devices on LSI's since early 1970s, it is widely recognized that three-dimensional (3-D) transistor structures will increasingly be important to extend further scaling in future. In response to the requirement, tetra methyl ammonium hydroxide (TMAH) etchant has been utilized to obtain 3-D MOS transistors named corrugated-channel transistor, CCT with vertical channels. The transistor channel is formed on steep vertical walls of almost exact {111} Miller index planes of single crystal {110} silicon substrate.