Semiconductor device including p-channel type transistor, and production method for manufacturing such semiconductor device
View Patent ↗In a semiconductor device including at least one p-channel type MOS transistor, a silicon dioxide layer is formed on a silicon substrate, and a gate electrode is formed on the silicon dioxide layer. The gate electrode silicon has a three-layered structure including a silicon-seed layer formed on the silicon dioxide layer, a silicon/germanium layer formed on the silicon-seed layer, and a polycrystalline silicon layer on the silicon/germanium layer. An average grain size of polycrystalline silicon in the polycrystalline silicon layer is at most 100 nm, and p-type impurities are substantially uniformly distributed in the gate electrode along a height thereof, and the germanium atoms are diffused from the silicon/germanium layer into the silicon-seed layer at high density.
1. A semiconductor device including at least one p-channel type MOS transistor, which device comprises:
a semiconductor substrate;
a gate insulating layer formed on said semiconductor substrate; and
a gate electrode formed on said gate insulating layer, said gate electrode having a multi-layered structure including a silicon-seed layer formed as a lowermost layer on said gate insulating layer, a polycrystalline silicon layer formed as an uppermost layer above said lowermost layer, and a silicon/germanium layer formed as an intermediate layer between said lowermost and uppermost layers,
wherein an average grain size of polycrystalline silicon in said uppermost layer is at most 100 nm, p-type impurities are substantially uniformly distributed in said gate electrode along a height thereof, and the germanium atoms are diffused from said intermediate layer into said lowermost layer at high density.
2. A semiconductor device as set forth in claim 1 , wherein said lowermost, intermediate, and uppermost layers are formed by using a chemical vapor deposition method, and the formation of said uppermost layer is carried out at a higher process temperature than a process temperature at which said lowermost and intermediate layers are formed.
3. A semiconductor device as set forth in claim 2 , wherein said chemical vapor deposition method is performed by a leaf-type chemical vapor deposition apparatus, the formation of said lowermost and intermediate layers is carried out at a process temperature falling in a range between approximately 550° C. and approximately 650° C., and the formation of said uppermost layer is carried out at a process temperature falling in a range between approximately 680° C. and approximately 800° C.
4. A semiconductor device as set forth in claim 2 , wherein said chemical vapor deposition method is performed by a batch-type chemical vapor deposition apparatus, the formation of said lowermost and intermediate layers is carried out at a process temperature falling in a range between approximately 450° C. and approximately 550° C., and the formation of said uppermost layer is carried out at a process temperature falling in a range between approximately 600° C. and approximately 650° C.
5. A semiconductor device as set forth in claim 2 , wherein said p-type impurities are implanted in said gate electrode, and the uniform distribution of said p-type impurities in said gate electrode and the diffusion of the germanium atoms from said intermediate layer into said lowermost layer are simultaneously achieved by annealing said semiconductor substrate at a higher process temperature than the process temperature at which said lowermost and intermediate layers are formed.