We study the N-component (2+1)-dimensional Gross-Neveu model bounded between two parallel planes separated by a distance L at finite temperature (T). We obtain a closed expression for the large-N effective coupling constant g = g(L,T,lambda). Different behavior depending on the magnitude of the fixed coupling constant lambda is found to lead to a ''critical'' value lambdac. If lambda < lambdac, only short-distance and/or high-temperature asymptotic freedom is found. For lambda > lambdac one also observes spatial confinement, which is destroyed by temperature effects. We find a confining length, Lc ~ 1.61 fm, that is close to the proton charge diameter ( ~ 1.74 fm) and a deconfining temperature, ~ 138 MeV, which is comparable to the estimated value of ~ 200 MeV for hadrons.