First things first: Poe creates atmosphere by setting a tone and mood from the outset of all his short stories. We as readers are led into dark and foreboding places, and the stories themselves build from that darkness.
Tension is created by Poe's use of language. Whether it's the constant heartbeat in "The Tell-Tale Heart," or the finger-tapping suspense in "Fall of the House of Usher," we as readers are kept waiting in suspense for the next plot event.
Overall, Poe's characters and settings contributed to the gothic feel of each of his works. We can picture the stony, shadowed places that he leads us, and as a result, we become more involved with each piece.
In Poe’s Gothic short stories like “The Fall of the House of Usher” and his portraits of madmen and grotesques such as “The Tell-Tale Heart” and “The Cask of Amontillado,” he is a master at building suspense and horror through his settings. Many of the stories take place in dark damp dungeons, or prisons and crypts. The mood is heavy and the dark setting and the tone of the author creates the weird feeling many get when they read today's Gothic novels like Steven Kings novels. Poe's short stories like "Fall of The House of Usher" contain “everything needed; a Gothic house, a terrified narrator, live burial, madness, and horrific catastrophe.”