\documentclass[tikz, border=5pt]{standalone}

\usetikzlibrary{patterns}

\begin{document}

\begin{tikzpicture}[font=\sffamily]
  \node[above=1ex] at (2,3.5) {\large $n$-channel MOSFET};

  \draw[fill = teal] (0,0) rectangle (11,-0.25) node[below=1ex, midway] {circuit board};
  \draw[fill=orange!50] (0,0) rectangle (11,2) node [below,midway] {$p$-doped semiconductor};

  \draw[pattern=bricks, pattern color=red] (4-0.2,2) rectangle (7+0.2,3) node[midway, fill=white, inner sep=2pt, draw, ultra thin, rounded corners=1] {dielectric};

  \draw[fill=blue!10] (4,3) rectangle (7,3.5) node[above=6pt, midway] {gate};
  \draw[fill=blue!10] (1.25,2) rectangle (3,2.5) node[above=6pt, midway] {source};
  \draw[fill=blue!10] (8,2) rectangle (9.75,2.5) node[above=6pt, midway] {drain};

  \foreach \x in {1,7} {
    \filldraw[fill=green!35] (\x,1) rectangle +(3,1) node[midway, align=center] {$n$-doped\\semiconductor};
  }
\end{tikzpicture}
\end{document}