| 摘要 |
PROBLEM TO BE SOLVED: To improve driving reliability by separating DMOS, CMOS transistors by an isolation layer and a partial oxide film, forming a DMOS region and a CMOS region different in thickness and forming a polysilicon resistance element on a partial oxide film. SOLUTION: A DMOS transistor, a CMOS transistor and a bipolar transistor are formed on a P-type substrate 10 simultaneously. Each of the transistors is separated by an element isolation layer 321 formed in an upper part of a bottom layer 31 and a thick oxide film 230 formed thereon by employing a local oxidation method. Resistor 511, 512 formed of polysilicon are formed on the thick oxidation film 230 on each isolation layer 231 and doped with a proper amount of ion according to a resistance value to be obtained. A gate oxide film 220 of a DMOS transistor is made thicker than an oxide film 221 of a CMOS transistor. As a result, withstand voltage characteristics of a DMOS which is a high withstand voltage element are improved. |
