Method of manufacturing a buried-gate semiconductor device and corresponding integrated circuit

A method of fabricating a semiconductor transistor device comprising a semiconductive channel region and a gate region, the gate region comprising at least one buried part extending under the semiconductive channel region, wherein fabricating comprises:

• forming a stack comprising a layer of silicon above a sacrificial layer,
• forming source/drain regions on either end of the stack,
• selectively etching away the sacrificial layer from either side of the stack to form a cavity,
• depositing first semiconductor material filling the cavity,
• forming an access opening to reach the first semiconductor material,
• depositing second semiconductor material in the access opening to be in contact with the first semiconductor material, and
• annealing to form in the cavity an alloy of the first and second semiconductor material which forms the at least one buried part of the gate region.

A method of fabricating a semiconductor transistor device comprising a semiconductive channel region and a gate region, the gate region comprising at least one buried part extending under the semiconductive channel region, wherein fabricating comprises:

• forming a stack comprising a layer of silicon above a sacrificial layer,
• forming source/drain regions on either end of the stack,
• selectively etching away the sacrificial layer from either side of the stack to form a cavity,
• depositing first semiconductor material filling the cavity,
• forming an access opening to reach the first semiconductor material,
• depositing aluminum in the access opening to be in contact with the first semiconductor material, and
• annealing to substitute the aluminum for the first semiconductor material in the cavity which forms the at least one buried part of the gate region.

A method of fabricating semiconductor transistor devices each comprising a semiconductive channel region and a gate region, the gate region comprising at least one buried part extending under the semiconductive channel region, wherein fabricating comprises:

• at each transistor location:
• forming a stack comprising a layer of silicon above a sacrificial layer,
• forming source/drain regions on either end of the stack,
• selectively etching away the sacrificial layer from either side of the stack to form a cavity,
• depositing first semiconductor material filling the cavity,
• forming an access opening to reach the first semiconductor material,
• if the transistor at that location is to be of pMOS type, then:
• depositing second semiconductor material in the access opening to be in contact with the first semiconductor material;
• and
• if the transistor at that location is to be of nMOS type, then:
• depositing aluminum in the access opening to be in contact with the first semiconductor material, and
• annealing to form the at least one buried part of the gate region,
• wherein annealing for the pMOS type transistor forms an alloy of the first and second semiconductor material in the cavity;
• and
• wherein annealing for the nMOS type transistor causes a substitution of the aluminum for the first semiconductor material in the cavity.

A method for manufacturing a semiconductor device comprising a semiconductor channel region and a gate region, the gate region comprising at least one buried part extending under the channel region, comprising forming the buried part of the gate region by:

• forming a cavity under the channel region,
• filling of the cavity with a first material,
• forming an access opening to the first material;
• depositing aluminum in the access opening in contact with the first material,
• annealing so as to substitute aluminum for the first material in the cavity and form the buried part of the gate region.

A method for manufacturing a semiconductor device comprising a semiconductor channel region and a gate region, the gate region comprising at least one buried part extending under the channel region, comprising forming the buried part of the gate region by:

• forming a cavity under the channel region,
• filling of the cavity with a first material,
• forming an access opening to the first material;
• depositing a second material in the access opening in contact with the first material,
• annealing so as to form an alloy of the first and second materials in the cavity and form the buried part of the gate region.