To obtain a low-noise MOSFET and a sensor device integrating the MOSFET by a method wherein a channel is provided in the deep part of a semiconductor substrate.

A channel 5a is provided in a depth of 1 to 10 nm or thereabouts from the surface of an Si substrate 1 consisting of a P-type region 2a and an N-type region 2b not on the surface of the substrate 2 but in the deep part of the substrate 2 to constitute the channel 5a into a bulk channel stricture. Consequently, the 1/f noise of a MOSFET is reduced. Accordingly, the MOSFET can be used favorably to the first-step amplification part in a sensor device, which is provided with a high insulation property sensor and takes out an external physical change as an electrical signal by an impedance conversion. This low-noise MOSFET can be suitably combined with a vacuum tube, a ferroelectric film, a PH glass, a cooled pure Si film or the like. The MOSFET with a CMOS process can be made common, whereby an integral formation of the MOSFET with a CMOS circuit having all functions, such as a memory function, an operation function and a communication function, is realized and a low-cost and compact sensor device can be obtained.