Semiconductor device

A semiconductor device, comprising:

• a memory cell region having a first transistor, and a peripheral circuit region which is formed around said memory cell region and has a second transistor, on a semiconductor substrate;
• wherein
• said first transistor has:
• a first source electrode and a first drain electrode which are formed on said semiconductor substrate,
• a first buried gate insulating film which is formed along an inner wall of a trench formed in said semiconductor substrate between said first source electrode and said first drain electrode and whose relative dielectric constant is higher than a relative dielectric constant of silicon oxide, and
• a buried gate electrode which is formed in said trench on said first buried gate insulating film, comprises metal and functions as a word line;
• and
• said second transistor has:
• a second source electrode and a second drain electrode which are formed on said semiconductor substrate,
• a first on-substrate gate insulating film which is formed on a surface of said semiconductor substrate between said second source electrode and said second drain electrode and whose relative dielectric constant is higher than a relative dielectric constant of silicon oxide, and
• an on-substrate gate electrode which is formed on said first on-substrate gate insulating film and comprises metal;
• said first buried gate insulating film and said first on-substrate gate insulating film comprising a compound containing hafnium (hereinafter referred to as “hafnium-containing compound”.);
• wherein
• a first Hf content percentage, which is a content percentage of hafnium in said first buried gate insulating film, is different from a second Hf content percentage, which is a content percentage of hafnium in said first on-substrate gate insulating film.