Observation of the spin signals in devices with low interface resistance of ferromagnetic/semiconductor junctions is one of the most important issues from the application view point. We demonstrate spin transport and accumulation signals in highly doped similar to 1x10(20) cm(-3) n(+)-Si by using CoFe/MgO/n(+)-Si (10 nm, 20 nm)/n-Si devices. The highly doped n(+)-Si was confined within a thin n(+)-Si layer (10 nm and 20 nm in thickness). In this confined structure, we observed the spin accumulation signals for the devices with impurity concentration of similar to 1x10(20) cm(-3) and the spin transport signals for the devices with similar to 1 k Omega mu m(2) interface resistance. This indicates that the n(+) confined structure is important for observing and increasing spin signals in the low-interface-resistance region. (C) 2017 Author(s).