\draw[semithick] (-4.01, 0) -- (4.01, 0);
\draw[semithick] (-4.01,-2) -- (4.01,-2);

\draw[pencildraw,semithick]  (-4,  0) to (-4, -2);
\draw[pencildraw,semithick]  (4 ,  0) to ( 4, -2);

\draw[semithick] (-2.5,0   ) rectangle (2.5,0.25);
\draw[semithick] (-2.5,0.25) rectangle (2.5,1.00);

\draw[semithick] (-3.5,0) -- (-2,0) 
  {[rounded corners=8pt] --(-2,-0.6) -- (-3.5,-0.6)} -- cycle;
\draw[semithick] ( 3.5,0) -- ( 2,0) 
  {[rounded corners=8pt] --( 2,-0.6) -- ( 3.5,-0.6)} -- cycle;

\node[] at ( 0   ,-1.5) {p};
\node[] at (-2.75,-0.3) {n+};
\node[] at ( 2.75,-0.3) {n+};

\draw[densely dashed] (-1.99,-0.75) rectangle (1.99,0.5);

\draw[{Latex[round,scale=.8]}-,thick]
  (0.5,0.5) --++ (0.5,1) node[anchor=west,font=\small] {Intrinsic model};