A
p channel field effect transistor in which the sensitivity of an
enzyme can be enhanced by immobilizing the
enzyme directly on an FET channel surface (
diamond surface), as well as a sensor including the same, is provided.
A diamond surface (22) having mixed
hydrogen terminals,
oxygen terminals, and amino terminals is treated under the action of
glutaraldehyde OHC(CH2)3CHO (30), so that the
glutaraldehyde (30) is immobilized on the
diamond surface (22) having mixed
hydrogen terminals,
oxygen terminals, and amino terminals. Subsequently,
urease (29) is further applied thereto, so that the amino group (31) of the
urease (29) is bonded to the
glutaraldehyde (30). That is, the
urease (29) can be immobilized on the
diamond surface (22) having mixed
hydrogen terminals,
oxygen terminals, and amino terminals. When the
urea concentration is increased from 10−6 M to 10−2 M, the
threshold voltage shifts by about 0.1 V in the
positive direction, and the sensitivity to
urea concentration of 30 mV / decade is exhibited.