Semiconductor device and method of manufacturing the same

A semiconductor device comprising:

• a first conductive type semiconductor portion formed on a semiconductor substrate;
• a gate electrode formed to surround a side portion of said first conductive type semiconductor portion;
• a channel region formed in said first conductive type semiconductor portion surrounded by said gate electrode;
• and
• source and drain layers formed to cover an upper surface and a lower surface of said first conductive type semiconductor portion,
• said gate electrode being formed of polycrystalline silicon-germanium, in which a germanium concentration is increased from a drain layer side to a source layer side, and
• an impurity concentration in said channel region being increased from the source layer side to the drain layer side.

A semiconductor device comprising:

• a first MISFET including:
• a first conductive type first semiconductor region formed in a semiconductor substrate;
• a first gate electrode formed on said first conductive type first semiconductor region;
• a first channel region formed immediately below said first gate electrode in said first conductive type first semiconductor region;
• and
• a second conductive type first diffusion layer constituting source/drain regions formed at opposite sides of said first channel region in said first conductive type first semiconductor region;
• and
• a second MISFET including:
• a second conductive type second semiconductor region formed in the semiconductor substrate and isolated from said first conductive type first semiconductor region;
• a second gate electrode formed on said second conductive type second semiconductor region;
• a second channel region formed immediately below said second gate electrode in said second conductive type second semiconductor region;
• and
• a first conductive type second diffusion layer constituting source/drain regions formed at opposite sides of said second channel region in said second conductive type second semiconductor region,
• said first and second gate electrodes being formed of polycrystalline silicon-germanium, in which a germanium concentration is continuously increased from a drain region side to a source region side,
• an impurity concentration immediately below said first gate electrode in said first conductive type first semiconductor region being continuously increased from the source region side to the drain region side in accordance with the germanium concentration in said first gate electrode, and
• an impurity concentration immediately below said second gate electrode in said second conductive type second semiconductor region being continuously increased from the source region side to the drain region side in accordance with the germanium concentration in said second gate electrode.