PURPOSE: To vary the state of a polymer by means of physical external stimulus of heat, light, etc., by using a polymer semiconductor having at least one type of π electron conjugated skeleton selected from a specific group.

CONSTITUTION: A MIS field effect transistor is manufactured by the steps of forming an insulating film 6 on a gate electrode 5 formed on a insulating substrate 1, superposing a polymer semiconductor film 2 thereon, and forming a source electrode 3 and a drain electrode 4 on the polymer semiconductor film via a gate region. In this case, the polymer semiconductor is selected from a group consisting of compounds represented by formulae I, II, III and IV having at least one type of π electron conjugated skeleton. In the formulae, X is NH or an element selected from oxygen group of S, O, Se, Te and Po. R1, R2 are alkyl group, and a group solubilized in organic solvent, having a group in which an isomeric reaction occurs by physical stimulus. n is the polymerization degree of 5-2000.