Semiconductor device and method for producing the same

A method for producing a semiconductor device comprising:

• preparing an SOI substrate having a first insulating film between a support substrate and a semiconductor layer;
• forming an element region and an element-separation region in said semiconductor layer;
• forming a gate insulating film on said semiconductor layer in said element region;
• forming a gate electrode on said gate insulating film;
• forming a second insulating film overlaying peripheral surfaces of said gate electrode;
• removing said gate insulating film by using said gate electrode overlaid by said second insulating film as a mask;
• performing a first thickness ajustment by a selective epitaxial growth process to obtain a predetermined thickness of said semiconductor layer after removing said gate insulating film;
• preforming ion implantation introducing a low concentration of impurities on said semiconductor layer;
• forming a first sidewall portion on side surfaces of said gate electrode by removing said second insulating film on an upper surface of said gate electrode;
• forming a second sidewall portion on side surfaces of said first sidewall portion;
• said second sidewall formation step including the steps of forming a third insulating film over at least the second insulating film and the semicoductor layer after preforming said first thickness adjustment, and preforming etch back on said third insulating film;
• wherein said first sidewall portion is formed simultaneously with said preformance of said etch back on said third insulating film.

A method for producing a semiconductor device, comprising:

• preparing an SOI substrate having a first insulating film between a support substrate and a semiconductor layer;
• forming an element region and an element-separation region in said semiconductor layer;
• forming a gate insulating film on said semiconductor layer in said element region;
• forming a gate electrode on said gate insulating film;
• forming a second insulating film overlaying peripheral surfaces of said gate electrode;
• removing said gate insulating film by using said gate electrode overlaid by said second insulating film as a mask;
• performing a first thickness adjustment by a selective epitaxial growth process to obtain a predetermined thickness of said semiconductor layer after removing said gate insulating film;
• performing ion implantation introducing a low concentration of impurities on said semiconductor layer;
• forming a first sidewall portion on side surfaces of said gate electrode by removing said second insulating film on an upper surface of said gate electrode;
• and
• forming a second sidewall portion on side surfaces of said first sidewall portion,
• wherein over etching on said semiconductor layer directly under said gate insulating film is restrained by performing wet etching on said gate insulating film while removing said gate insulating film.