Patent ID: 7947547
Filing Date: 2011-05-24
Classification: H01L

Abstract:
1. A method for manufacturing a semiconductor device comprising: forming a gate insulating film over a semiconductor layer in an nMOS transistor formation region and a pMOS transistor formation region; forming a work function control layer in which nitrogen concentration in the nMOS transistor formation region is lower than nitrogen concentration in the pMOS transistor formation region over the gate insulating film; forming a low-resistance layer which contains nitrogen over the work function control layer; and performing heat treatment for diffusing nitrogen from the low-resistance layer into the work function control layer; wherein the forming of the work function control layer comprises: forming a first work function control layer having a first nitrogen concentration in the nMOS transistor formation region, the first nitrogen concentration is lower than a second nitrogen concentration at which a work function of a gate electrode of an nMOS transistor is obtained; and forming a second work function control layer having a third nitrogen concentration at which a work function of a gate electrode of a pMOS transistor is obtained in the pMOS transistor formation region, the third nitrogen concentration being higher than the second nitrogen concentration; and wherein after the heat treatment for diffusing nitrogen from the low-resistance layer into the work function control layer, the first work function control layer has the second nitrogen concentration and the second work function control layer has a nitrogen concentration higher than or equal to the third nitrogen concentration; the first work function control layer and the second work function control layer include hafnium; and the low-resistance layer includes molybdenum nitride.