A method for reducing interfacial layer (IL) thickness for high-k dielectrics and metal gate stack is provided. In one embodiment, the method includes forming an interfacial layer on a semiconductor substrate, etching back the interfacial layer, depositing a high-k dielectric material over the interfacial layer, and forming a metal gate over the high-k dielectric material. The IL can be chemical oxide, ozonated oxide, thermal oxide, or formed by ultraviolet ozone (UVO) oxidation process from chemical oxide, etc. The etching back of IL can be performed by a Diluted HF (DHF) process, a vapor HF process, or any other suitable process. The method can further include performing UV curing or low thermal budget annealing on the interfacial layer before depositing the high-k dielectric material.