| 摘要 |
PROBLEM TO BE SOLVED: To adjust and set the turn-on voltage to a specified value even when using a short channel transistor in a read amplifier by installing a field-effect transistor having a variable bus tab potential in a bus tab separated from the other elements in a semiconductor substrate. SOLUTION: On an n--type semiconductor substrate 4, a p-type epitaxial layer 5 is disposed. Between the semiconductor substrate 4 and the epitaxial layer 5, an n+-type buried layer 6 is formed. The n+-type buried layer 6 forms a bus tab 9 together with an n-type drain D and n-type diffusion regions 7, 8. The diffusion regions are disposed in the bus tab 9, separating a field-effect transistor 10 having the n-type drain D, the source S, and the gate G made of polycrystalline silicon from the other elements. The bus tab potential is supplied to the field-effect transistor 10 through a p+-type region having a connection terminal B to set the turn-on voltage to a specified value.
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