Manufacturing method of partial SOI wafer, semiconductor device using the partial SOI wafer and manufacturing method thereof

A semiconductor device comprising:

• a first semiconductor region having a buried oxide layer formed therein,
• a second semiconductor region in which the buried oxide layer does not exist,
• a trench formed to a depth to reach at least the buried oxide layer in a boundary portion between said first and second semiconductor regions, and
• an insulating layer for isolation buried in said trench,
• wherein a portion near a contact portion of the bottom surface of said isolation insulating layer with said second semiconductor region has a curved surface.

A partial SOI wafer manufacturing method comprising:

• selectively removing part of a buried oxide layer and first silicon layer on an SOI substrate having the first silicon layer formed on a semiconductor substrate with the buried oxide layer disposed therebetween,
• forming a protection film to cover a remaining portion of the first silicon layer,
• forming a second silicon layer by use of an epitaxial growth method on that part of the semiconductor substrate from which the first silicon layer and buried oxide layer are removed,
• forming a trench to reach at least the buried oxide layer in a boundary portion between the first and second silicon layers by anisotropic etching, and
• burying an isolation insulating material into the trench,
• wherein an angle made by the bottom surface of the trench with the side surface of the second silicon layer is an obtuse angle or a portion near a contact portion of the bottom surface of the trench with the second silicon layer has a curved surface.

A semiconductor device manufacturing method comprising:

• selectively removing part of a buried oxide layer and first silicon layer on an SOI substrate having the first silicon layer formed on a semiconductor substrate with the buried oxide layer disposed therebetween,
• forming a protection film to cover a remaining portion of the first silicon layer,
• forming a second silicon layer by use of an epitaxial growth method on that part of the semiconductor substrate from which the first silicon layer and buried oxide layer are removed,
• forming a trench to reach at least the buried oxide layer in a boundary portion between the first and second silicon layers,
• burying an isolation insulating material into the trench, and
• respectively forming first and second elements in the first and second silicon layers.