Patent ID: 7700438

Claim:
A method for forming a semiconductor device with a nano-crystal gate structure resistant to migration of a mobile species, comprising: providing a semiconductor substrate having an upper surface; creating on the upper surface a gate dielectric having therein a layer of spaced-apart nano-crystals of a material adapted to reversibly receive and store charge; forming first and second impurity blocking layers over the gate dielectric by forming the first impurity blocking layer in contact with the gate dielectric, wherein the first impurity blocking layer comprises FeBSi, and forming the second impurity blocking layer in contact with the first impurity blocking layer, wherein the second impurity blocking layer comprises a second material selected from a second group that includes Al 2 O 3 , TiN, TiO2, Co3O4, FeBSi, MoSiN, W, TaC, and Si3N4; forming a gate conductor layer over the first and second impurity blocking layers; etching out a gate stack comprising portions of the gate dielectric, the nano-crystals, the first and second impurity blocking layers and the gate conductor layer; and providing spaced-apart source-drain regions laterally disposed on either side of the gate stack.