| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a forming method of manufacturing a plurality of kinds of transistors having desired characteristics through a small number of processes. Ž<P>SOLUTION: A semiconductor device has a device isolation region 12 having a first depth, first and second wells of a first conductivity type, a gate insulating film GI1 formed at the first well and having a first thickness, a first transistor 17 having a source/drain region of a second conductivity type and a gate electrode, a gate insulating film GI2 formed at the second well and having a second thickness thinner than the first thickness, and a second transistor 18 having a source/drain region of the second conductivity type and a gate electrode. The first well has a first impurity concentration distribution having a maximum value only at a depth equal to or deeper than the first depth, and the second well has a second impurity concentration distribution having a maximum value even at a second depth shallower than the first depth on the whole by putting an impurity concentration distribution having a maximum value at the second depth over the same first impurity concentration distribution with the first well. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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