The invention is directed to providing a resistor with high reliability. The invention is also directed to miniaturizing a semiconductor device having a MOS transistor and a resistor element on the same semiconductor substrate. An N-type well region is formed in a front surface of a P-type semiconductor substrate, and a P−-type resistor layer is formed in a front surface of the well region. A conductive layer is annularly formed on the well region so as to surround the resistor layer. A predetermined voltage is applied to the conductive layer and a channel is not formed under the conductive layer during normal operation, thereby isolating a pull-down resistor from the other elements (e.g. a P-channel type MOS transistor). The resistor layer and an element isolation insulation film do not contact each other. Both the PMOS and the pull-down resistor are formed in one region surrounded by the element isolation insulation film.