| 摘要 |
PROBLEM TO BE SOLVED: To simplify the manufacturing process of an optical sensor including semiconductor devices, by forming through the doping of a second impurity the P+ active regions of its P-channel MOS transistor through using as masks the oxide films formed after doping a first impurity into the P-well region of its N-channel MOS transistor to form the N+ active regions of its N-channel MOS transistor. SOLUTION: In an N-type substrate 1, a P-well region 5 of an N-channel MOS transistor and a base region 4 of a phototransistor are formed. Then, into each of the element isolation regions of the MOS transistor and phototransistor, phosphorus ions and boron ions are field-doped successively to form a P-field-dope 6 and an N-field-dope 2. Thereafter, the element isolation regions of the MOS transistor and phototransistor are oxidized selectively to form field oxide films 3. By using as masks the field oxide films 3, phosphorus ions are doped into the P-well region 5 of the N-channel MOS transistor to form therein N+ active regions, and boron ions are doped into the semiconductor region of a P-channel MOS transistor to form therein P+ active regions.
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