Patent ID: 8053315

Claim:
A method for manufacturing a trenched semiconductor power device comprising step of opening a trench in a semiconductor substrate and said method further comprising: forming an oxide layer on sidewalls and a bottom surface of said trench followed by filling said trench with a trenching filling material followed by an etch back process to remove from a top portion of said trench until a desired depth is reached; depositing a high density plasma (HDP) oxide layer into said trench filling a space above said trench filling material and surrounded by said oxide layer on said trench sidewalls followed by an annealing densification process in an N2 or O2/N2 ambient environment at an elevated temperature for increasing an etch rate of said HDP oxide layer to be substantially the same as an etch rate of the oxide layer surrounding the HDP oxide layer; and dry etching back said HDP oxide layer and partially etching the oxide layer on said trench sidewalls surrounding said HDP oxide layer to expose said HDP oxide layer followed by a dry or wet-etch to obtain a desired HDP oxide layer thickness and a desired oxide layer thickness of the oxide layer on said trench sidewalls.