FinFET alignment structures using a double trench flow

摘要

A method is provided for forming FinFETS with improved alignment features. Embodiments include forming on a Si substrate pillars of TEOS on poly-Si; conformally depositing a first TEOS liner over the entire substrate; etching the first TEOS liner and substrate through the pillars, forming first trenches; filling the first trenches and spaces between the pillars with an oxide; removing the TEOS from the pillars and the oxide therebetween; removing the poly-Si; conformally depositing a second TEOS liner over the entire Si substrate; etching the second TEOS liner and Si between the oxide, forming second trenches having a larger depth than the first trenches; filling the second trenches with oxide; removing the oxide and the first and second TEOS liners down to an upper surface of the Si substrate; and recessing the oxide below the upper surface of the Si substrate.