Fabrication method of a semiconductor integrated circuit having an SOI device and a bulk semiconductor device on a common semiconductor substrate

Claim 1

A method of fabricating a semiconductor integrated circuit carrying a first type semiconductor device wherein at least a part thereof is formed within a substrate and a second type semiconductor device which is provided on an oxide layer formed on the substrate, comprising the steps of: a) providing a silicon oxide film on the substrate selective in correspondence to where the first type semiconductor device is to be formed, the silicon oxide film having an upper major surface at a first level; b) producing a silicon nitride film on the silicon oxide film; c) oxidizing the substrate using the silicon nitride film as an oxidation resistant mask to form an oxide layer in correspondence to where the substrate is not covered by the silicon nitride film, the oxide layer having an upper major surface at a second level that is higher than the first level, the oxide layer forming a birds beak structure at a boundary between the oxide layer and the oxide film, the birds beak structure having a declining upper major surface that declines toward the oxide film and continues declining toward the upper major surface of the oxide film, the oxide layer having the silicon nitride film extending over a limited portion of the declining upper major surface of the birds beak structure; d) depositing a silicon layer on the substrate extending continuously over the silicon nitride film and the oxide layer to bury thereunder the silicon nitride film and the oxide layer; e) annealing the silicon layer such that the silicon layer melts and crystallizes prior to forming a single crystal silicon layer; and f) patterning the single crystal silicon layer such that the single crystal silicon layer is removed except for a part thereof covering a region of the oxide layer where the second type semiconductor device is to be provided, the patterning being performed to remove the silicon nitride film simultaneously with the removal of the silicon layer.

Claim 2

A method of fabricating a semiconductor integrated circuit carrying a first type semiconductor device wherein at least a part thereof is formed within a substrate and a second type semiconductor device which is provided on an oxide layer formed on the substrate, comprising the steps of: a) providing a silicon oxide film on the substrate selective in correspondence to where the first type semiconductor device is to be formed, the silicon oxide film having an upper major surface at a first level; b) producing a silicon nitride film on the silicon oxide film; c) oxidizing the substrate using the silicon nitride film as an oxidation resistant mask to form an oxide layer in correspondence to where the substrate is not covered by the silicon nitride film, the oxide layer having an upper major surface at a second level that is higher than the first level, the oxide layer forming a birds beak structure at a boundary between the oxide layer and the oxide film, the birds beak structure having a declining upper major surface that declines toward the oxide film and continues declining toward the upper major surface of the oxide film, the oxide layer having the silicon nitride film extending over a limited portion of the declining upper major surface of the birds beak structure; d) depositing a silicon layer on the substrate extending continuously over the silicon nitride film and the oxide layer to bury thereunder the silicon nitride film and the oxide layer; e) annealing the silicon layer such that the silicon layer melts and crystallizes prior to forming a single crystal silicon layer; and f) patterning the single crystal silicon layer such that the single crystal silicon layer is removed except for a part thereof covering a region of the oxide layer where the second type semiconductor device is to be provided, the patterning being performed to remove the silicon nitride film simultaneously with the removal of the silicon layer.