A refresh characteristic of a DRAM memory cell is improved and the performance
of a MISFET formed in the periphery thereof and constituting a logic circuit is improved.
Each gate electrode in a memory cell area is formed of p type polycrystalline
silicon, and a cap insulating film on each gate electrode and a sidewall film on
the sidewall thereof are formed of a silicon oxide film. A polycrystalline silicon
film formed on the gate electrodes and between the gate electrodes is polished
by a CMP method, and thereby contact electrodes are formed. Also, sidewall films
each composed of a laminated film of the silicon oxide film and the polycrystalline
silicon film are formed on the sidewall of the gate electrodes in the logic circuit
area, and these films are used as a mask to form semiconductor areas. As a result,
it is possible to reduce the boron penetration and form contact electrodes in a
self-alignment manner. In addition, the performance of the MISFET constituting
the logic circuit can be improved.
